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2021

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Sheng Y, Zhang T, Zhang S, Johnston M, Zheng X, Shan Y, Liu T, Huang Z, Qian F, Xie Z, Ai Y, Zhong H, Kuang T, Dincer C, Urban G, Hu J
A CRISPR/Cas13a-powered catalytic electrochemical biosensor for successive and highly sensitive RNA diagnostics
2021 Biosens Bioelectron, Band: 178, Seite: 113027
KurzfassungRapid and specific quantitation of a variety of RNAs with low expression levels in early-stage cancer is highly desirable but remains a challenge. Here, we present a dual signal amplification strategy consisting of the CRISPR/Cas13a system and a catalytic hairpin DNA circuit (CHDC), integrated on a reusable electrochemical biosensor for rapid and accurate detection of RNAs. Signal amplification is accomplished through the unique combination of the CRISPR/Cas13a system with CHDC, achieving a limit of detection of 50 aM within a readout time of 6 minutes and an overall process time of 36 minutes, using a measuring volume of 10 μL. Enzymatic regeneration of the sensor surface and ratiometric correction of background signal allow up to 37 sequential RNA quantifications by square-wave voltammetry on a single biosensor chip without loss of sensitivity. The reusable biosensor platform could selectively (specificity = 0.952) and sensitively (sensitivity = 0.900) identify low expression RNA targets in human serum, distinguishing early-stage patients (n = 20) suffering from non-small-cell lung carcinoma (NSCLC) from healthy subjects (n = 30) and patients with benign lung disease (n = 12). Measurement of six NSCLC-related RNAs (miR-17, miR-155, TTF-1 mRNA, miR-19b, miR-210 and EGFR mRNA) shows the ability of the electrochemical CRISPR/CHDC system to be a fast, low-cost and highly accurate tool for early cancer diagnostics.
Wieland T, Assmann J, Bethe A, Fidelak C, Gmoser H, Janßen T, Kotthaus K, Lübke-Becker A, Wieler LH, Urban G
A Real-Time Thermal Sensor System for Quantifying the Inhibitory Effect of Antimicrobial Peptides on Bacterial Adhesion and Biofilm Formation
2021 Sensors, Band: 21, Seite: 2771
KurzfassungThe increasing rate of antimicrobial resistance (AMR) in pathogenic bacteria is a global threat to human and veterinary medicine. Beyond antibiotics, antimicrobial peptides (AMPs) might be an alternative to inhibit the growth of bacteria, including AMR pathogens, on different surfaces. Biofilm formation, which starts out as bacterial adhesion, poses additional challenges for antibiotics targeting bacterial cells. The objective of this study was to establish a real-time method for the monitoring of the inhibition of (a) bacterial adhesion to a defined substrate and (b) biofilm formation by AMPs using an innovative thermal sensor. We provide evidence that the thermal sensor enables continuous monitoring of the effect of two potent AMPs, protamine and OH-CATH-30, on surface colonization of bovine mastitis-associated Escherichia (E.) coli and Staphylococcus (S.) aureus. The bacte- ria were grown under static conditions on the surface of the sensor membrane, on which temperature oscillations generated by a heater structure were detected by an amorphous germanium thermistor. Bacterial adhesion, which was confirmed by white light interferometry, caused a detectable amplitude change and phase shift. To our knowledge, the thermal measurement system has never been used to assess the effect of AMPs on bacterial adhesion in real time before. The system could be used to screen and evaluate bacterial adhesion inhibition of both known and novel AMPs.

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Farahani H, Wagiran R, Urban G
Barium Strontium Titanate-Based Humidity Sensors: Microstructure, Surface Morphology, Dopant Influence, and Transduction Mechanism Investigations
2021 ACS Applied Electronic Materials
KurzfassungInvestigation of the effect of addition of external positive ions on the humidity-sensing properties of perovskite-based oxides is an interesting topic. Humidity-sensitive properties of barium strontium titanate nanocomposite films have been investigated in the range of 20–95% relative humidity (RH) at room temperature in the pure form (Ba₀.₅,Sr₀.₅)TiO₃ (BST) and doped with 1, 3, and 5 mol % magnesium oxide (MgO) nanoparticles. Microstructural characterization of nanopowders and films was performed by X-ray diffraction (XRD), surface area and pore size analyzer, field emission scanning electron microscopy (FESEM), and energy-dispersive X-ray spectroscopy (EDX) exhibiting an ordered crystallite size, surface area, average pore volume, and open porosity reduction as a function of doping. X-ray photoelectron spectroscopy (XPS) was applied as a complementary characterization technique. None of the (1 – x)(Ba₀.₅,Sr₀.₅)TiO₃ – (x)MgO (with x = 0.01, 0.03, 0.05) nanocomposites shows a remarkable improvement in the performance of humidity-sensing devices such as intrinsic impedance and hysteresis. BST as a humidity-sensing material shows the lowest and suitable intrinsic impedance, an excellent linearity, an acceptable sensor repeatability with a total impedance/bulk resistance change of 3 orders of magnitude for the entire RH range at 10 kHz, and a small hysteresis of about 4.9% RH. The BST sensor also exhibits the desired response time of about 34 s and adequate stability. Possible sensing mechanisms for different humidity levels based on the experimental results were discussed and further confirmed by impedance spectroscopy of the materials. For the first time, a Gerischer element was detected as an interfacial electrical phenomenon for mass-transfer control at high RH levels. This phenomenon arises from the contribution of a kinetic process and a diffusion process associated with a chemical reaction(s) over the surface.
Ates H, Mohsenin H, Wenzel C, Glatz R, Wagner H, Bruch R, Höfflin N, Spassov S, Streicher L, Lozano-Zahonero S, Flamm B, Trittler R, Hug MJ, Köhn M, Schmidt J, Schumann S, Urban G, Weber W, Dincer C
Biosensor-Enabled Multiplexed On-Site Therapeutic Drug Monitoring of Antibiotics
2021 Advanced Materials, Seite: 2104555
KurzfassungPersonalized antibiotherapy ensures that the antibiotic concentration remains in the optimal therapeutic window to maximize efficacy, minimize side effects, and avoid the emergence of drug resistance due to insufficient dosing. However, such individualized schemes need frequent sampling to tailor the blood antibiotic concentrations. To optimally integrate therapeutic drug monitoring (TDM) into the clinical workflow, antibiotic levels can either be measured in blood using point-of-care testing (POCT), or can rely on noninvasive sampling. Here, a versatile biosensor with an antibody-free assay for on-site TDM is presented. The platform is evaluated with an animal study, where antibiotic concentrations are quantified in different matrices including whole blood, plasma, urine, saliva, and exhaled breath condensate (EBC). The clearance and the temporal evaluation of antibiotic levels in EBC and plasma are demonstrated. Influence of matrix effects on measured drug concentrations is determined by comparing the plasma levels with those in noninvasive samples. The system's potential for blood-based POCT is further illustrated by tracking ß‑lactam concentrations in untreated blood samples. Finally, multiplexing capabilities are explored successfully for multianalyte/sample analysis. By enabling a rapid, low-cost, sample-independent, and multiplexed on-site TDM, this system can shift the paradigm of “one‑size-fits-all” strategy.

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Bruch R, Johnston M, Kling A, Mattmüller T, Baaske J, Partel S, Madlener S, Weber W, Urban G, Dincer C
CRISPR-powered electrochemical microfluidic multiplexed biosensor for target amplification-free miRNA diagnostics
2021 Biosens Bioelectron, Band: 177, Seite: 112887
KurzfassungRecently the use of microRNAs (miRNAs) as biomarkers for a multitude of diseases has gained substantial significance for clinical as well as point-of-care diagnostics. Amongst other challenges, however, it holds the central requirement that the concentration of a given miRNA must be evaluated within the context of other factors in order to unambiguously diagnose one specific disease. In terms of the development of diagnostic methods and devices, this implies an inevitable demand for multiplexing in order to be able to gauge the abundance of several components of interest in a patient's sample in parallel. In this study, we design and implement different multiplexed versions of our electrochemical microfluidic biosensor by dividing its channel into subsections, creating four novel chip designs for the amplification-free and simultaneous quantification of up to eight miRNAs on the CRISPR-Biosensor X ('X' highlighting the multiplexing aspect of the device). We then use a one-step model assay followed by amperometric readout in combination with a 2-minute-stop-flow-protocol to explore the fluidic and mechanical characteristics and limitations of the different versions of the device. The sensor showing the best performance, is subsequently used for the Cas13a-powered proof-of-concept measurement of two miRNAs (miRNA-19b and miRNA-20a) from the miRNA-17~92 cluster, which is dysregulated in the blood of pediatric medulloblastoma patients. Quantification of the latter, alongside simultaneous negative control measurements are accomplished on the same device. We thereby confirm the applicability of our platform to the challenge of amplification-free, parallel detection of multiple nucleic acids.

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Phan QA, Truong LB, Medina-Cruz D, Dincer C, Mostafavi E
CRISPR/Cas-powered nanobiosensors for diagnostics
2021 Biosensors and Bioelectronics, Band: 197, Seite: 113732
KurzfassungCRISPR diagnostics (CRISPR-Dx) offer a wide range of enhancements compared to traditional nanobiosensors by taking advantage of the excellent trans-cleavage activity of the CRISPR/Cas systems. However, the single-stranded DNA/RNA reporters of the current CRISPR-Dx suffer from poor stability and limited sensitivity, which make their application in complex biological environments difficult. In comparison, nanomaterials, especially metal nanoparticles, exhibits robust stability and desirable optical and electrocatalytical properties, which make them ideal as reporter molecules. Therefore, biosensing research is moving towards the use of the trans-cleavage activity of CRISPR/Cas effectors on metal nanoparticles and apply the new phenomenon to develop novel nanobiosensors to target various targets such as viral infections, genetic mutations and tumor biomarkers, by using different sensing methods, including, but not limited to fluorescence, luminescence resonance, colorimetric and electrochemical signal readout. In this review, we explore some of the most recent advances in the field of CRISPR-powered nanotechnological biosensors. Demonstrating high accuracy, sensitivity, selectivity and versatility, nanobiosensors along with CRISPR/Cas technology offer tremendous potential for next-generation diagnostics of multiple targets, especially at the point of care and without any target amplification.
Martinez-Dominguez MV, Zottel A, Šamec N, Jovčevska I, Dincer C, Kahlert UD, Nickel A-C
Current Technologies for RNA-Directed Liquid Diagnostics
2021 Cancers, Band: 13, Seite: 5060
KurzfassungThere is unequivocal acceptance of the variety of enormous potential liquid nucleic acid-based diagnostics seems to offer. However, the existing controversies and the increased awareness of RNA-based techniques in society during the current global COVID-19 pandemic have made the readiness of liquid nucleic acid-based diagnostics for routine use a matter of concern. In this regard — and in the context of oncology — our review presented and discussed the status quo of RNA-based liquid diagnostics. We summarized the technical background of the available assays and benchmarked their applicability against each other. Herein, we compared the technology readiness level in the clinical context, economic aspects, implementation as part of routine point-of-care testing as well as performance power. Since the preventive care market is the most promising application sector, we also investigated whether the developments predominantly occur in the context of early disease detection or surveillance of therapy success. In addition, we provided a careful view on the current biotechnology investment activities in this sector to indicate the most attractive strategies for future economic success. Taken together, our review shall serve as a current reference, at the interplay of technology, clinical use and economic potential, to guide the interested readers in this rapid developing sector of precision medicine.

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Uka B, Kieninger J, Urban G, Weltin A
Electrochemical Microsensor for Microfluidic Glyphosate Monitoring in Water Using MIP-Based Concentrators
2021 ACS Sensors, Band: 6, Nummer: 7, Seiten: 2738 - 2746
KurzfassungGlyphosate (GLY) is a broad-spectrum herbicide and is the most used pesticide worldwide. This vast usage has raised strong interest in the ecotoxicological impacts and human risks, with contamination of water being a major concern. Decentralized analytical techniques for water monitoring are of high importance. In this work, we present a small, low-cost, and time-effective electrochemical, chip-based microfluidic device for direct electrochemical detection of GLY downstream of a molecularly imprinted polymer (MIP) concentrator. We studied the electrochemical behavior of GLY and its metabolite aminomethylphosphonic acid (AMPA) using cyclic voltammetry with noble metal electrodes in acidic, neutral, and basic media. A chronoamperometric sensor protocol was developed for sensitive and selective GLY measurements on gold electrodes. The optimized protocol was transferred to a chip-based microsensor platform for online and real-time detection of GLY in a microfluidic setup. The results in the range from 0 to 50 μM GLY in 0.5 M H₂SO₄ show high linearity and a sensitivity of 10.3 ± 0.6 μA mm⁻² mM⁻¹ for the chip-based microfluidic platform. Successful recovery of GLY concentrated from untreated tap water and its precise detection from low volumes demonstrates the advantages of our system.
Urban S, Deschner BJ, Trinkies LL, Kieninger J, Kraut M, Dittmeyer R, Urban G, Weltin A
In Situ Mapping of H₂, O₂, and H₂O₂ in Microreactors: A Parallel, Selective Multianalyte Detection Method
2021 Acs Sensors, Band: 6, Nummer: 4, Seiten: 1583 - 1594
KurzfassungDetermining local concentrations of the analytes in state-of-the-art microreactors is essential for the development of optimized and safe processes. However, the selective, parallel monitoring of all relevant reactants and products in a multianalyte environment is challenging. Electrochemical microsensors can provide unique information on the reaction kinetics and overall performance of the hydrogen peroxide synthesis process in microreactors, thanks to their high spatial and temporal resolution and their ability to measure in situ, in contrast to other techniques. We present a chronoamperometric approach which allows the selective detection of the dissolved gases hydrogen and oxygen and their reaction product hydrogen peroxide on the same platinum microelectrode in an aqueous electrolyte. The method enables us to obtain the concentration of each analyte using three specific potentials and to subtract interfering currents from the mixed signal. While hydrogen can be detected independently, no potentials can be found for a direct, selective measurement of oxygen and hydrogen peroxide. Instead, it was found that for combined signals, the individual contribution of all analytes superimposes linearly additive. We showed that the concentrations determined from the subtracted signals correlate very well with results obtained without interfering analytes present. For the first time, this approach allowed the mapping of the distribution of the analytes hydrogen, oxygen, and hydrogen peroxide inside a multiphase membrane microreactor, paving the way for online process control.
Ates H, Brunauer A, von Stetten F, Urban G, Güder F, Merkoçi A, Früh S, Dincer C
Integrated Devices for Non‐Invasive Diagnostics
2021 Adv Funct Mater, Band: 31, Nummer: 15, Seite: 2010388
Kurzfassung“Sample‐in‐answer‐out” type integrated diagnostic devices have been widely recognized as the ultimate solution to simplify testing across healthcare systems. Such systems are equipped with advanced fluidic, mechanical, chemical, biological, and electronic components to handle patient samples without any manual steps therefore have the potential to accelerate intervention and improve patient outcomes. In this regard, the combination of integrated devices and non‐invasive sampling has gained a substantial interest to further improve the comfort and safety of patients. In this Review, the pioneering developments in integrated diagnostics are covered and their potential in non‐invasive sampling is discussed. The key properties of possible sample types are highlighted by addressing their relevance for the clinical practice. Last, the factors affecting the transition of integrated devices from academia to the market are identified by analyzing the technology readiness levels of selected examples and alternative remedies are explored to increase the rate of survival during this transition.

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Kiefer R, Weis DG, Velmurugan BK, Tamm T, Urban G
Ion Mobility in Thick and Thin Poly-3,4 Ethylenedioxythiophene Films—From EQCM to Actuation
2021 Polymers, Band: 13, Nummer: 15, Seite: 2448
KurzfassungConductive polymer actuators and sensors rely on controlled ion transport coupled to a potential/charge change. In order to understand and control such devices, it is of paramount importance to understand the factors that determine ion flux at various conditions, including the synthesis potential. In this work, the ion transport in thinner poly-3,4-ethylenedioxythiophene (PEDOT) films during charge/discharge driven by cyclic voltammetry is studied by consideration of the electrochemical quartz crystal microbalance (EQCM) and the results are compared to the actuation responses of thicker films that have been synthesized with the same conditions in the bending and linear expansion modes. The effects of polymerization potentials of 1.0 V, 1.2 V, and 1.5 V are studied to elucidate how polymerization potential contributes to actuation, as well the involvement of the EQCM. In this work, it is revealed that there is a shift from anion-dominated to mixed to cation-dominated activity with increased synthesis potential. Scanning electron microscopy shows a decrease in porosity for the PEDOT structure with increasing synthesis potential. EQCM analysis of processes taking place at various potentials allows the determination of appropriate potential windows for increased control over devices.
Dryg I, Xie Y, Bergmann M, Urban G, Shain W, Hofmann UG
Long-term in vivo monitoring of gliotic sheathing of ultrathin entropic coated brain microprobes with fiber-based optical coherence tomography
2021 J. Neural Eng., Band: 18, Nummer: 4, Seite: 045002
KurzfassungMicrofabricated neuroprosthetic devices have made possible important observations on neuron activity; however, long-term high-fidelity recording performance of these devices has yet to be realized. Tissue-device interactions appear to be a primary source of lost recording performance. The current state of the art for visualizing the tissue response surrounding brain implants in animals is Immunohistochemistry + Confocal Microscopy, which is mainly performed after sacrificing the animal. Monitoring the tissue response as it develops could reveal important features of the response which may inform improvements in electrode design. Optical Coherence Tomography (OCT), an imaging technique commonly used in ophthalmology, has already been adapted for imaging of brain tissue. Here, we use OCT to achieve real-time, in vivo monitoring of the tissue response surrounding chronically implanted neural devices. The employed tissue-response-provoking implants are coated with a plasma-deposited nanofilms, which have been demonstrated as a biocompatible and anti-inflammatory interface for indwelling devices. We evaluate the method by comparing the OCT results to traditional histology qualitatively and quantitatively. The differences in OCT signal across the implantation period between the plasma group and the control reveal that the Plasma-type coating of otherwise rigid brain probes (glass) only slightly improve the glial encapsulation in the brain parenchyma indicating that geometrical or mechanical influences are dominating the encapsulation process.

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Jiang N, Tansukawat ND, Gonzalez-Macia L, Ates H, Dincer C, Güder F, Tasoglu S, Yetisen AK
Low-Cost Optical Assays for Point-of-Care Diagnosis in Resource- Limited Settings
2021 ACS Sensors, Band: 6, Nummer: 6, Seiten: 2108 - 2124
KurzfassungReadily deployable, low-cost point-of-care medical devices such as lateral flow assays (LFAs), microfluidic paper-based analytical devices (μPADs), and microfluidic thread-based analytical devices (μTADs) are urgently needed in resource-poor settings. Governed by the ASSURED criteria (affordable, sensitive, specific, user-friendly, rapid and robust, equipment-free, and deliverability) set by the World Health Organization, these reliable platforms can screen a myriad of chemical and biological analytes including viruses, bacteria, proteins, electrolytes, and narcotics. The Ebola epidemic in 2014 and the ongoing pandemic of SARS-CoV-2 have exemplified the ever-increasing importance of timely diagnostics to limit the spread of diseases. This review provides a comprehensive survey of LFAs, μPADs, and μTADs that can be deployed in resource-limited settings. The subsequent commercialization of these technologies will benefit the public health, especially in areas where access to healthcare is limited.
Weis DG, Kiefer R, Zondaka Z, Tamm T, Urban G
Polypyrrole and poly(3,4-ethylenedioxythiophene) on silicon cantilever: Role of formation potential in bending displacement
2021 Synthetic Met, Band: 271, Seite: 116653
KurzfassungThe feasibility of conducting polymer bending actuators deposited on free-standing conductive silicon cantilevers was studied in this work. The motivation is the micro-system-technique, where mostly silicon bimorph piezo- electric actuators have been applied. Polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT) with various formation potentials were studied. The formation potential 1.1 V was found optimal for both materials, while PEDOT outperformed PPy in virtually every aspect. Long-term durability tests of 1000 cycles showed that activity was maintained, with PEDOT holding up better than PPy. The results show that conducting polymers, especially PEDOT, could be viable active materials for Si-based bilayer actuators, with low driving voltages to reach significant displacements.
Altay A, Learney R, Güder F, Dincer C
Sensors in Blockchain
2021 Trends in Biotechnology
KurzfassungBlockchain, the technology behind bitcoin, has stimulated global conversation around digital decentralization to connect societies and economies. Connected low-cost sensors within Internet of Things (IoT) networks may soon perform measurements, exchange data, and make decisions automatically over decentralized networks; these systems could improve healthcare, the quality of goods, and supply chain efficiency.
Ates H, Yetisen AK, Güder F, Dincer C
Wearable devices for the detection of COVID-19
2021 Nat Electron, Band: 4, Seiten: 13 - 14
KurzfassungWearable electronic devices, which allow physiological signals to be continuously monitored, can be used in the early detection of asymptomatic and pre-symptomatic cases of COVID-19.

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2020

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Behrmann O, Hügle M, Eckardt F, Bachmann I, Heller C, Schramm M, Turner C, Hufert F, Dame G
3D Printed Monolithic Microreactors for Real-Time Detection of Klebsiella pneumoniae and the Resistance Gene blaNDM-1 by Recombinase Polymerase Amplification
2020 Micromachines-basel, Band: 11, Nummer: 6, Seite: 595
Hügle M, Behrmann O, Raum M, Hufert FT, Urban G, Dame G
A lab-on-a-chip for free-flow electrophoretic preconcentration of viruses and gel electrophoretic DNA extraction
2020 Analyst, Band: 145, Seiten: 2554 - 2561
KurzfassungNucleic acid amplification techniques such as real-time PCR are essential instruments for the identification and quantification of viruses. They are fast, very sensitive and highly specific, but often require elaborate and labor intensive sample preparation to achieve successful amplification of the target sequence. In this work we demonstrate the complete microfluidic preparation of amplifiable virus DNA from dilute specimens. Our approach combines free-flow electrophoretic preconcentration of viral particles with thermal lysis and gel-electrophoretic nucleic acid extraction on a single device. The on-chip preconcentration achieves a capture efficiency of >99% for dilute suspensions of bacteriophage PhiX174. Following preconcentration, phages are thermally lysed and released DNA is recovered after 40 s of on-chip gel-electrophoresis with a recovery rate of ∼73%. Furthermore we demonstrate a detection limit of ∼1 PFU ml⁻¹ (∼0.02 DNA copies per μl) for the detection of bacteriophage PhiX174 by PCR. To simplify operation of the device, we describe the development of a custom-made chip holder as well as a compact peristaltic pump and power supply, which enable user-friendly operation with low risk of cross-contamination and high potential for automation in the field of point-of-care diagnostics.
Behrmann O, Spiegel M
COVID-19: from rapid genome sequencing to fast decisions
2020 Lancet Infect Dis
Wöhrle J, Krämer SD, Meyer PA, Rath C, Hügle M, Urban G, Roth G
Digital DNA microarray generation on glass substrates
2020 Sci Rep-uk, Band: 10, Seite: 5770
KurzfassungIn this work, we show how DNA microarrays can be produced batch wise on standard microscope slides in a fast, easy, reliable and cost-efficient way. Contrary to classical microarray generation, the microarrays are generated via digital solid phase PCR. We have developed a cavity-chip system made of a PDMS/aluminum composite which allows such a solid phase PCR in a scalable and easy to handle manner. For the proof of concept, a DNA pool composed of two different DNA species was used to show that digital PCR is possible in our chips. In addition, we demonstrate that DNA microarray generation can be realized with different laboratory equipment (slide cycler, manually in water baths and with an automated cartridge system). We generated multiple microarrays and analyzed over 13,000 different monoclonal DNA spots to show that there is no significant difference between the used equipment. To show the scalability of our system we also varied the size and number of the cavities located in the array region up to more than 30,000 cavities with a volume of less than 60 pL per cavity. With this method, we present a revolutionary tool for novel DNA microarrays. Together with new established label-free measurement systems, our technology has the potential to give DNA microarray applications a new boost.
Rostas AM, Ledernez L, Dietel L, Heidinger L, Bergmann M, Altenburger M, Bruch R, Urban G, Schleicher E, Weber S
Direct EPR detection of atomic nitrogen in a nitrogen plasma jet
2020 Phys Chem Chem Phys, Band: 22, Seiten: 3875 - 3882
KurzfassungIn this study a low-pressure nitrogen plasma jet was analyzed by real-time EPR spectroscopy at room temperature. It could be demonstrated that transiently formed nitrogen radicals can be detected without the necessity to use spin-traps or other reagents. In contrast to results from optical emission spectroscopy, only signals from the ⁴S ground state of atomic ¹⁴N and ¹⁵N could be detected via continuous-wave and pulsed EPR methods. Analysis of the EPR spectra lead to an isotropic g value of 1.9971 and to a magnetic isotropic hyperfine interaction constant of a(¹⁴N) = (10.47 ± 0.02) MHz and a(¹⁵N) = (14.69 ± 0.02) MHz. Moreover, the life and relaxation times could be determined; both are discussed in terms of spectral widths and actual concentrations of nitrogen species within the plasma. In sum, the real-time EPR technique is a fast and reliable alternative to detect paramagnetic species like atomic nitrogen in atmospheric pressure plasma jets, and may be used for a continuous monitoring of the quality of a plasma jet.
Wieland F, Bruch R, Bergmann M, Partel S, Urban G, Dincer C
Enhanced Protein Immobilization on Polymers—A Plasma Surface Activation Study
2020 Polymers-basel, Band: 12, Nummer: 1, Seite: 104
KurzfassungOver the last years, polymers have gained great attention as substrate material, because of the possibility to produce low-cost sensors in a high-throughput manner or for rapid prototyping and the wide variety of polymeric materials available with different features (like transparency, flexibility, stretchability, etc.). For almost all biosensing applications, the interaction between biomolecules (for example, antibodies, proteins or enzymes) and the employed substrate surface is highly important. In order to realize an effective biomolecule immobilization on polymers, different surface activation techniques, including chemical and physical methods, exist. Among them, plasma treatment offers an easy, fast and effective activation of the surfaces by micro/nanotexturing and generating functional groups (including carboxylic acids, amines, esters, aldehydes or hydroxyl groups). Hence, here we present a systematic and comprehensive plasma activation study of various polymeric surfaces by optimizing different parameters, including power, time, substrate temperature and gas composition. Thereby, the highest immobilization efficiency along with a homogenous biomolecule distribution is achieved with a 5-min plasma treatment under a gas composition of 50% oxygen and nitrogen, at a power of 1000 W and a substrate temperature of 80 °C. These results are also confirmed by different surface characterization methods, including SEM, XPS and contact angle measurements.

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Kutluk H, Bruch R, Urban G, Dincer C
Impact of assay format on miRNA sensing: Electrochemical microfluidic biosensor for miRNA-197 detection
2020 Biosens Bioelectron, Band: 148, Seite: 111824
KurzfassungMicroRNAs (miRNAs) are important biomarkers for the early detection of various diseases, especially cancer. Therefore, there is a continuing interest in different biosensing strategies that allow for the point-of-care measurement of miRNAs. Almost all miRNA sensors utilize cross-hybridization of the target miRNA with a capture probe for the recognition, which can be designed in either a sandwich or a competitive format. In this work, we present a low-cost microfluidic biosensor platform for the electrochemical measurement of miRNA-197 (a tumor biomarker candidate) in undiluted human serum samples, using very low sample volumes (580 nl) and within an hour. For this purpose, different on-chip miRNA bioassays based on sandwich and competitive formats are developed and compared in terms of their sensitivity, dynamic range, selectivity, precision, and simplicity. The obtained results show that, despite having a narrower dynamic range when compared to the competitive format, the sandwich assay has superior performance regarding its sensitivity and selectivity. The lowest limit of detection which can be achieved with the sandwich assay is 1.28 nM (0.74 fmole), while 4.05 nM (2.35 fmole) with the competitive format. Moreover, the sandwich assay proves to have a better distinction against single-base mismatch oligonucleotide sequences compared to the competitive one. Due to its versatility and easy handling, overcoming the issue with the sensitivity, the implemented electrochemical microfluidic biosensor could pave the way for rapid and low-cost on-site miRNA diagnostics.
Farahani H, Wagiran R, Urban G
Investigation of Room Temperature Protonic Conduction of Perovskite Humidity Sensors
2020 IEEE Sens J
KurzfassungThis paper shows a correlation between surface effective porosity due to various sintering regimes and humidity sensitive electrical properties of the perovskite-based bulk type humidity sensors, at room temperature. Furthermore, room temperature humidity transduction mechanism of the thick film type humidity sensors was studied in detail through electrochemical impedance spectroscopy (EIS) and major transmissive components were detected by the fitting of the Bode diagrams and Nyquist complexes to the equivalent circuits. The microstructural, morphological and elemental characterizations were carried on using XRD, EFTEM, FESEM, and EDX. Physical properties including open porosity/bulk density were investigated through American Standard Test Method (ASTM). An innovative self-designed material test fixture with ceramic supports was fabricated for a high S/N ratio electrical measurement of the bulk samples. All the sensors were set up at 20-95% RH. The morphological, physical, and electrical results of the bulk pellets indicate a direct correlation of the open cavities and AC conduction. The higher the open porosity is, the greater is the conduction and vice versa. Presence of the ionic transport is clearly observed from the frequency-conductance spectra at room temperature. Noise-free detected behavior via EIS proves that the proton transfer mechanism is a dominant responsible, and executed by both charge transfer resistance and kinetically controlled charge transfer (diffusive species) at low and middle to high RH. Next to the Warburg effect (at 80% RH), for the first time, a Gerischer impedance was found as a dominant agent of transduction at 85% RH to above.
Wenzel C, Schmidt J, Urban G, Schumann S, Spassov SG
Mechanical ventilation restores blood gas homeostasis and diaphragm muscle strength in ketamine/medetomidine anaesthetized rats
2020 Exp Physiol
KurzfassungIn pre‐clinical small animal studies with surgical interventions under general anaesthesia, animals are often left to breathe spontaneously. However, anaesthesia may impair respiratory functions and result in disturbed blood gas homeostasis. In turn, the disturbed blood gas homeostasis can affect physiological functions and thus unintentionally impact the experimental results. We hypothesized that short‐term mechanical ventilation restores blood gas balance and physiological functions despite anaesthesia and surgical interventions. Therefore, we investigated variables of blood gas analyses and diaphragm muscle strength in rats anesthetized with ketamine/medetomidine after tracheotomy and catheterization of the carotid artery under spontaneous breathing and after 20 min of mechanical ventilation following the same surgical intervention. Spontaneous breathing during general anaesthesia and surgical intervention resulted in unphysiological blood oxygen partial pressure (<65 mmHg) and carbon dioxide partial pressure (> 55 mmHg). After subsequent short‐term mechanical ventilation, blood gas partial pressures were restored to their physiological ranges. Additionally, diaphragm muscle strength of animals breathing spontaneously was lower compared to animals that received subsequent mechanical ventilation (P = 0.0063). We conclude that spontaneous breathing of rats under ketamine/medetomidine anaesthesia is not sufficient to maintain a physiological blood gas balance. Disturbed blood gas balance is related to reduced diaphragm muscle strength. Mechanical ventilation for only 20 min restores blood gas homeostasis and muscle strength. Therefore, monitoring and maintenance of blood gas balance should be conducted to ensure quality and relevance of small animal experiments.
Urban S, Tamilselvi Sundaram V, Weltin A, Kieninger J, Urban G, Weltin A
Microsensor Electrodes for 3D Inline Process Monitoring in Multiphase Microreactors
2020 Sensors-basel, Band: 20, Nummer: 17, Seite: 4876
KurzfassungWe present an electrochemical microsensor for the monitoring of hydrogen peroxide direct synthesis in a membrane microreactor environment by measuring the hydrogen peroxide and oxygen concentrations. In prior work, for the first time, we performed in situ measurements with electrochemical microsensors in a microreactor setup. However, the sensors used were only able to measure at the bottom of the microchannel. Therefore, only a limited assessment of the gas distribution and concentration change over the reaction channel dimensions was possible because the dissolved gases entered the reactor through a membrane at the top of the channel. In this work, we developed a new fabrication process to allow the sensor wires, with electrodes at the tip, to protrude from the sensor housing into the reactor channel. This enables measurements not only at the channel bottom, but also along the vertical axis within the channel, between the channel wall and membrane. The new sensor design was integrated into a multiphase microreactor and calibrated for oxygen and hydrogen peroxide measurements. The importance of measurements in three dimensions was demonstrated by the detection of strongly increased gas concentrations towards the membrane, in contrast to measurements at the channel bottom. These findings allow a better understanding of the analyte distribution and diffusion processes in the microreactor channel as the basis for process control of the synthesis reaction.
Nguyen T.A., Echtermeyer D, Barthel A, Urban G, Pliquett U
Multichannel cell detection in microcompartments by means of true parallel measurements using the Solartron S-1260
2020 Journal of Electrical Bioimpedance, Band: 11, Nummer: 1, Seiten: 49 - 56
KurzfassungDesigning proper frontend electronics is critical in the development of highly sophisticated electrode systems. Multielectrode arrays for measuring electrical signals or impedance require multichannel readout systems. Even more challenging is the differential or ratiometric configuration with simultaneous assessment of measurement and reference channels. In this work, an eight-channel frontend was developed for contacting a 2×8 electrode array (8 measurement and 8 reference electrodes) with a large common electrode to the impedance gain-phase analyzer Solartron 1260 (S-1260). Using the three independent and truly parallel monitor channels of the S-1260, impedance of trapped cells and reference material was measured at the same time, thereby considerably increasing the performance of the device. The frontend electronics buffers the generator output and applies a potentiostatic signal to the common electrode of the chip. The applied voltage is monitored using the current monitor of the S-1260 via voltage/current conversion. The frontend monitors the current through the electrodes and converts it to a voltage fed into the voltage monitors of the S-1260. For assessment of the 8 electrode pairs featured by the chip, a relay-based multiplexer was implemented. Extensive characterization and calibration of the frontend were carried out in a frequency range between 100 Hz and 1 MHz. Investigating the influence of the multiplexer and the frontend electronics, direct measurement with and without frontend was compared. Although differences were evident, they have been negligible below one per cent. The significance of measurement using the complex S-1260-frontend-electrode was tested using Kohlrausch's law. The impedance of an electrolytic dilution series was measured and compared to the theoretical values. The coincidence of measured values and theoretical prediction serves as an indicator for electrode sensitivity to cell behavior. Monitoring of cell behavior on the microelectrode surface will be shown as an example.
Weltin A, Ganatra D, König K, Joseph K, Hofmann UG, Urban G, Kieninger J
New life for old wires: Electrochemical sensor method for neural implants
2020 J Neural Eng, Band: 17, Nummer: 1, Seite: 016007
KurzfassungObjective. Electrochemical microsensors based on noble metals can give essential information on their microenvironment with high spatio‐temporal resolution. However, most advanced chemo‐ and biosensors lack the long‐term stability for physiological monitoring of brain tissue beyond an acute application. Noble metal electrodes are widely used as neural interfaces, particularly for stimulating in the central nervous system. Our goal was to recruit already deployed, unmodified noble metal electrodes (Pt, Pt/Ir) as in situ chemical sensors. Approach. With advanced electrochemical sensor methods, we investigated electrode surface processes, oxidizable species and oxygen as an indicator for tissue mass transport. We developed a unique, multi‐step, amperometric/potentiometric sensing procedure derived from the investigation of Pt surface processes by chronocoulometry providing fundamental characterization of the electrode itself. Main results. The resulting electrochemical protocol preconditions the electrode, measures oxidizable and reducible species, and the open circuit potential. A linear, stable sensor performance was demonstrated, also in the presence of proteins, validating signal stability of our cyclic protocol in complex environments. We investigated our sensor protocol with microelectrodes on custom Pt/Ir‐wire tetrodes by in vivo measurements in the rat brain for up to four weeks. Results showed that catalytic activity of the electrode is lost over time, but our protocol is repeatedly able to both quantify and restore electrode sensitivity in vivo. Significance. Our approach is highly relevant because it can be applied to any existing Pt electrode. Current methods to assess the brain/electrode microenvironment mainly rely on imaging techniques, histology and analysis of explanted devices, which are often end‐point methods. Our procedure delivers online and time‐transient information on the chemical microenvironment directly at the electrode/tissue interface of neural implants, gives new insight into the charge transfer processes, and delivers information on the state of the electrode itself addressing long‐term electrode degradation.

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Ates HC, Roberts JA, Lipman J, Cass AEG, Urban G, Dincer C
On-Site Therapeutic Drug Monitoring
2020 Trends Biotechnol
KurzfassungRecent technological advances have stimulated efforts to bring personalized medicine to the fore. Yet, more traditional application fields like therapeutic drug monitoring (TDM) remained rather under-appreciated. Owing to clear dose response relationships, TDM could improve patient outcomes and reduce healthcare costs. While chromatography-based routine practices are restricted due to high costs and turnaround-times, biosensors offer on-site analysis, overcoming these limitations. Nevertheless, sensor-based approaches have yet breakthrough for clinical TDM applications, due to the gap between scientific and clinical community. This review provides a critical overview of current TDM practices, followed by a TDM guideline to establish a common ground across disciplines. Finally, we discuss how the translation of sensor systems for TDM can be facilitated, by highlighting the challenges and opportunities.
Behrmann O, Bachmann I, Spiegel M, Schramm M, Abd El Wahed A, Dobler G, Dame G, Hufert F
Rapid Detection of SARS-CoV-2 by Low Volume Real-Time Single Tube Reverse Transcription Recombinase Polymerase Amplification Using an Exo Probe with an Internally Linked Quencher (Exo-IQ)
2020 Clin Chem, Band: 66, Nummer: 8, Seiten: 1047 - 1054
KurzfassungBackground The current outbreak of SARS-CoV-2 has spread to almost every country with more than 5 million confirmed cases and over 300,000 deaths as of May 26, 2020. Rapid first-line testing protocols are needed for outbreak control and surveillance. Methods We used computational and manual designs to generate a suitable set of reverse transcription recombinase polymerase amplification (RT-RPA) primer and exonuclease probe, internally quenched (exo-IQ), sequences targeting the SARS-CoV-2 N gene. RT-RPA sensitivity was determined by amplification of in vitro transcribed RNA standards. Assay selectivity was demonstrated with a selectivity panel of 32 nucleic acid samples derived from common respiratory viruses. To validate the assay against full-length SARS-CoV-2 RNA, total viral RNA derived from cell culture supernatant and 19 nasopharyngeal swab samples (8 positive and 11 negative for SARS-CoV-2) were screened. All results were compared to established RT-qPCR assays. Results The 95% detection probability of the RT-RPA assay was determined to be 7.74 (95% CI: 2.87–27.39) RNA copies per reaction. The assay showed no cross-reactivity to any other screened coronaviruses or respiratory viruses of clinical significance. The developed RT-RPA assay produced 100% diagnostic sensitivity and specificity when compared to RT-qPCR (n = 20). Conclusions With a run time of 15 to 20 minutes and first results being available in under 7 minutes for high RNA concentrations, the reported assay constitutes one of the fastest nucleic acid based detection methods for SARS-CoV-2 to date and may provide a simple-to-use alternative to RT-qPCR for first-line screening at the point of need.
Schössler T, Schön F, Lemier C, Urban G
Reliability improvements of thin film platinum resistors on wafer-level and micro-hotplates at stress temperatures in the range of 140–290 °C
2020 Microelectron Reliab, Band: 104, Seite: 113557
KurzfassungIn this work, we present the improvement of thermal long-term reliability of platinum resistors through transition from a quasi-stoichiometric SiO2 layer to silicon-rich SiOx cover layers. The physical effects were investigated on a platinum meander test structure using a wafer-level based approach. As a result, reliability can be studied simultaneously on several hundreds of chips with a great statistical certainty. In addition, possible influences of chip dicing and packaging technology can be avoided. The activation energy for drift is extracted from a linear fit to the Arrhenius diagram. Furthermore, a comparison of drift data with an analytical equation is done as proposed in literature. Investigations with resistors on fabricated micro-hotplates exemplify the validity of improving the long-term reliability even on device-level.

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Morales-Narváez E, Dincer C
The Impact of Biosensing in a Pandemic Outbreak: COVID-19
2020 Biosens Bioelectron, Band: 163, Seite: 112274
KurzfassungCOVID-19 pandemic outbreak is the most astounding scene ever experienced in the XXI century. In this opinionated review, we underscore the crucial role of biosensing to handle with such situations. As a matter of fact, testing accelerates life-saving decisions on treatment and isolation of COVID-19 patients in an early stage, and thereby, decelerating or even preventing the spread of such emerging infectious diseases. Meanwhile, it is also proven that a timely and broad application of testing leads to lower mortality rates in countries like Germany or South Korea. Besides, biosensors are also powerful tools for effective assessment of clinical progress and to provide alertness on severity or critical trends of infection. In view hereof, we critically discuss the state-of-the-art biosensing devices for COVID-19 testing. We spot the urgent needs and highlight innovative diagnostic approaches for targeting various COVID-19 related biomarkers. Finally, we outline our recommendations on biosensors and biosensing-related issues towards pandemic outbreaks.

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Liebisch F, Weltin A, Marzioch J, Urban G, Kieninger J
Zero-Consumption Clark-Type Microsensor for Oxygen Monitoring in Cell Culture and Organ-on-Chip Systems
2020 Sensor Actuat B-chem, Seite: 128652
KurzfassungClark-type oxygen microsensors promise zero analyte consumption if the feedback mode (Ross principle) is successfully implemented. Our approach was a microsensor with platinum as working and counter electrode material, a pHEMA hydrogel layer containing buffer solution as electrolyte and PDMS as gas-permeable membrane. We were able to demonstrate successful implementation of the Ross principle by measurement of the counter electrode potential. The microsensors could be stored dry and activated by immersion into aqueous analyte. Chronoamperometric protocols were applied to enable long-term stability for more than one week without recalibration. The microsensors were integrated in conventional tissue culture flasks for cell measurements. Respiration monitoring was done in T-47D breast cancer monolayer culture. The unique feature combination of zero analyte consumption, 1-point calibration and sufficient long-term stability make these sensors an ideal candidate to monitor oxygenation and respiration in different cell culture and organ-on-chip systems.

2019

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Behrmann O, Hügle M, Bronsert P, Herde B, Heni J, Schramm M, Hufert FT, Urban G, Dame G
A lab-on-a-chip for rapid miRNA extraction
2019 Plos One, Band: 14, Nummer: 12, Seite: e0226571
KurzfassungWe present a simple to operate microfluidic chip system that allows for the extraction of miRNAs from cells with minimal hands-on time. The chip integrates thermoelectric lysis (TEL) of cells with native gel-electrophoretic elution (GEE) of released nucleic acids and uses non-toxic reagents while requiring a sample volume of only 5 μl. These properties as well as the fast process duration of 180 seconds make the system an ideal candidate to be part of fully integrated point-of-care applications for e.g. the diagnosis of cancerous tissue. GEE was characterized in comparison to state-of-the-art silica column (SC) based RNA recovery using the mirVana kit (Ambion) as a reference. A synthetic miRNA (miR16) as well as a synthetic snoRNA (SNORD48) were subjected to both GEE and SC. Subsequent detection by stem-loop RT-qPCR demonstrated a higher yield for miRNA recovery by GEE. SnoRNA recovery performance was found to be equal for GEE and SC, indicating yield dependence on RNA length. Coupled operation of the chip (TEL + GEE) was characterized using serial dilutions of 5 to 500 MCF7 cancer cells in suspension. Samples were split and cells were subjected to either on-chip extraction or SC. Eluted miRNAs were then detected by stem-loop RT-qPCR without any further pre-processing. The extraction yield from cells was found to be up to ~200-fold higher for the chip system under non-denaturing conditions. The ratio of eluted miRNAs is shown to be dependent on the degree of complexation with miRNA associated proteins by comparing miRNAs purified by GEE from heat-shock and proteinase-K based lysis.

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Grell M, Dincer C, Le T, Lauri A, Nunez Bajo E, Kasimatis M, Barandun G, Maier SA, Cass AEG, Güder F
Autocatalytic Metallization of Fabrics Using Si Ink, for Biosensors, Batteries and Energy Harvesting
2019 Adv Funct Mater, Band: 29, Seite: 1804798
KurzfassungCommercially available metal inks are mainly designed for planar substrates (for example, polyethylene terephthalate foils or ceramics), and they contain hydrophobic polymer binders that fill the pores in fabrics when printed, thus resulting in hydrophobic electrodes. Here, a low‐cost binder‐free method for the metallization of woven and nonwoven fabrics is presented that preserves the 3D structure and hydrophilicity of the substrate. Metals such as Au, Ag, and Pt are grown autocatalytically, using metal salts, inside the fibrous network of fabrics at room temperature in a two‐step process, with a water‐based silicon particle ink acting as precursor. Using this method, (patterned) metallized fabrics are being enabled to be produced with low electrical resistance (less than 3.5 Ω sq⁻¹). In addition to fabrics, the method is also compatible with other 3D hydrophilic substrates such as nitrocellulose membranes. The versatility of this method is demonstrated by producing coil antennas for wireless energy harvesting, Ag–Zn batteries for energy storage, electrochemical biosensors for the detection of DNA/proteins, and as a substrate for optical sensing by surface enhanced Raman spectroscopy. In the future, this method of metallization may pave the way for new classes of high‐performance devices using low‐cost fabrics.

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Bruch R, Urban G, Dincer C
CRISPR/Cas Powered Multiplexed Biosensing
2019 Trends Biotechnol, Band: 37, Nummer: 8, Seiten: 791 - 792
KurzfassungMultiplexed CRISPR/Cas biosensing offers various possibilities for diagnosing different diseases by analyzing many analytes from one single specimen. However, in this relatively new field, nearly no multiplexing approaches exist, as many challenges need to be addressed. We discuss the reasons behind it and possible strategies to push the multiplexing level.
Bruch R, Baaske J, Chatelle C, Meirich M, Madlener S, Weber W, Dincer C, Urban G
CRISPR/Cas13a powered electrochemical microfluidic biosensor for nucleic acid amplification-free miRNA diagnostics
2019 Adv Mater, Band: 31, Nummer: 51, Seite: 1905311
KurzfassungNon-coding small RNAs, such as microRNAs, are becoming the biomarkers of choice for multiple diseases in clinical diagnostics. A dysregulation of these microRNAs can be associated with many different diseases, such as cancer, dementia or cardiovascular conditions. The key for an effective treatment is an accurate initial diagnosis at an early stage, improving the patient’s survival chances. In this work, the first CRISPR/Cas13a powered microfluidic, integrated electrochemical biosensor for the on-site detection of microRNAs is introduced. Through this unique combination, the quantification of the potential tumor markers microRNA miR-19b and miR-20a has been realized without any nucleic acid amplification. With a readout time of 9 minutes and an overall process time of less than 4 hours, a limit of detection of 10 pM was achieved, using a measuring volume of less than 0.6 μl. Furthermore, the feasibility of our biosensor platform to detect miR-19b in serum samples of children, suffering from brain cancer, has been demonstrated. The validation of the obtained results with a standard qRT-PCR method shows the ability of our electrochemical CRISPR powered system to be a low-cost, easily scalable and target amplification-free tool for nucleic acid based diagnostics.

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Dönch I, Tran TA, David L, Montembault A, Viguier E, Gorzelanny C, Sudre G, Cachon T, Louback-Mohamed M, Horbelt N, Peniche-Covas C, Osorio-Madrazo A
Cellulose Nanofiber-Reinforced Chitosan Hydrogel Composites for Intervertebral Disc Tissue Repair
2019 Biomimetics, Band: 4, Nummer: 1, Seite: 19
KurzfassungThe development of non-cellularized composites of chitosan (CHI) hydrogels, filled with cellulose nanofibers (CNFs) of the type nanofibrillated cellulose, was proposed for the repair and regeneration of the intervertebral disc (IVD) annulus fibrosus (AF) tissue. With the achievement of CNF-filled CHI hydrogels, biomaterial-based implants were designed to restore damaged/ degenerated discs. The structural, mechanical and biological properties of the developed hydrogel composites were investigated. The neutralization of weakly acidic aqueous CNF/CHI viscous suspensions in NaOH yielded composites of physical hydrogels in which the cellulose nanofibers reinforced the CHI matrix, as investigated by means of microtensile testing under controlled humidity. We assessed the suitability of the achieved biomaterials for intervertebral disc tissue engineering in ex vivo experiments using spine pig models. Cellulose nanofiber-filled chitosan hydrogels can be used as implants in AF tissue defects to restore IVD biomechanics and constitute contention patches against disc nucleus protrusion while serving as support for IVD regeneration.
Dornhof J, Urban G, Kieninger J
Deposition of Copper Nanofilms by Surface-Limited Redox Replacement of Underpotentially Deposited Lead on Polycrystalline Gold
2019 J Electrochem Soc, Band: 166, Nummer: 1, Seiten: D3001 - D3005
KurzfassungElectrochemical atomic layer deposition (E-ALD) of copper on polycrystalline gold is a promising method to achieve highly reproducible nanofilms. Cu films of more than 30 nm were deposited by the repetitive execution of underpotential deposition (UPD) of lead and a subsequent surface limited redox replacement by Cu. Both steps were carried out in the same solution. The method enables, in contrast to conventional gas phase ALD, the deposition of layers with different height on the same substrate. Deposit growth in this one-pot system was monitored in-situ with an electrochemical quartz crystal microbalance. Film thickness, measured by optical profilometry, was compared to the number of deposition cycles and indicated a highly linear dependency. Obtained layers were characterized by means of atomic force and scanning electron microscopy and showed a slight roughening with almost no increase in the effective surface area. Energy dispersive X-ray measurements confirmed the purity of deposited Cu nanofilms. It was shown, that even with a simple setup, the described method allows the reproducible deposition of Cu on polycrystalline Au.

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Yi Q, Cai D, Xiao M, Nie M, Cui Q, Cheng J, Li C, Feng J, Urban G, Xu Y-C, Lan Y, Du W
Direct antimicrobial susceptibility testing of bloodstream infection on SlipChip
2019 Biosens Bioelectron, Band: 135, Seiten: 200 - 207
KurzfassungThis paper describes an integrated microfluidic SlipChip device for rapid antimicrobial susceptibility testing (AST) of bloodstream pathogens in positive blood cultures. Unlike conventional AST methods, which rely on an overnight subculture of positive blood cultures to obtain isolated colonies, this device enables direct extraction and enrichment of the bacteria from positive blood cultures by dielectrophoresis. SlipChip technology enables parallel inoculation of the extracted bacteria into nanoliter-scale broth droplets to perform multiplexed ASTs simultaneously. The nanoliter confinement in the droplets increases the effective inoculation amount of the bacteria, shortens the diffusion distance of nutrient elements and gases, and allows faster growth and proliferation rates. Entropy-based image analysis used for the characterization of bacterial susceptibility patterns eliminates the requirement for single-cell morphological analysis and fluorescence labeling. As a proof-of-concept, the susceptibility patterns of Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 6538p, and a positive blood culture containing Escherichia coli against several broad-spectrum antibiotics were determined by the SlipChip device. The on-chip AST results were well matched with those respectively reported by the broth microdilution method and a BD Phoenix Automated Microbiology System. Reliable AST results can be reported to clinicians within 3–8 h using this simple device after positive blood culture, allowing earlier proper administration of antimicrobial therapy.
Dincer C, Bruch R, Costa-Rama E, Fernández-Abedul MT, Merkoçi A, Manz A, Urban G, Güder F
Disposable Sensors in Diagnostics, Food, and Environmental Monitoring
2019 Adv Mater, Band: 31, Nummer: 30, Seite: 1806739
KurzfassungDisposable sensors are low-cost and easy-to-use sensing devices intended for short-term or rapid single-point measurements. The growing demand for fast, accessible, and reliable information in a vastly connected world makes disposable sensors increasingly important. The areas of application for such devices are numerous, ranging from pharmaceutical, agricultural, environmental, forensic, and food sciences to wearables and clinical diagnostics, especially in resource-limited settings. The capabilities of disposable sensors can extend beyond measuring traditional physical quantities (for example, temperature or pressure); they can provide critical chemical and biological information (chemo- and biosensors) that can be digitized and made available to users and centralized/decentralized facilities for data storage, remotely. These features could pave the way for new classes of low-cost systems for health, food, and environmental monitoring that can democratize sensing across the globe. Here, a brief insight into the materials and basics of sensors (methods of transduction, molecular recognition, and amplification) is provided followed by a comprehensive and critical overview of the disposable sensors currently used for medical diagnostics, food, and environmental analysis. Finally, views on how the field of disposable sensing devices will continue its evolution are discussed, including the future trends, challenges, and opportunities.

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Ledernez L, Engesser F, Altenburger M, Urban G, Bergmann M
Effect of Transient Spark Disinfection on Various Endodontics Relevant Bacteria
2019 Plasma Medicine, Band: 9, Nummer: 2, Seiten: 121 - 128
KurzfassungThe in-vitro efficacy of the Transient Spark Disinfection was examined on different types of bacteria that are relevant in the field of endodontics, in particular E. faecalis. The device is so constructed that it can be inserted down to the apex of prepared root canals and the method can be applied in conventional, regenerative and reparative endodontics. Starting with a bacterial load of 0.2 ml of undiluted 10⁹ bacteria / ml spread on a Petri dish, the 3-minute treatment lead to a 10⁶ CFU/cm² reduction of the bacterial load over a surface area that is relevant in this indication.
Krämer S, Wöhrle J, Meyer P, Urban G, Roth G
How to copy and paste DNA microarrays
2019 Sci Rep-uk, Band: 9, Seite: 13940
KurzfassungAnalogous to a photocopier, we developed a DNA microarray copy technique and were able to copy patterned original DNA microarrays. With this process the appearance of the copied DNA microarray can also be altered compared to the original by producing copies of different resolutions. As a homage to the very first photocopy made by Chester Charlson and Otto Kornei, we performed a lookalike DNA microarray copy exactly 80 years later. Those copies were also used for label-free real-time kinetic binding assays of apo-dCas9 to double stranded DNA and of thrombin to single stranded DNA. Since each DNA microarray copy was made with only 5 µl of spPCR mix, the whole process is cost-efficient. Hence, our DNA microarray copier has a great potential for becoming a standard lab tool.
Maier D, Laubender E, Basavanna A, Schumann S, Güder F, Urban G, Dincer C
Toward Continuous Monitoring of Breath Biochemistry: A Paper-Based Wearable Sensor for Real-Time Hydrogen Peroxide Measurement in Simulated Breath
2019 Acs Sensors, Band: 4, Nummer: 11, Seiten: 2945 - 2951
KurzfassungExhaled breath contains a large amount of biochemical and physiological information concerning one’s health and provides an alternative route to noninvasive medical diagnosis of diseases. In the case of lung diseases, hydrogen peroxide (H₂O₂) is an important biomarker associated with asthma, chronic obstructive pulmonary disease, and lung cancer and can be detected in exhaled breath. The current method of breath analysis involves condensation of exhaled breath, is not continuous or real time, and requires two separate and bulky devices, complicating the periodic or long-term monitoring of a patient. We report the first disposable paper-based electrochemical wearable sensor that can monitor exhaled H₂O₂ in artificial breath calibration-free and continuously, in real time, and can be integrated into a commercial respiratory mask for on-site testing of exhaled breath. To improve precision for sensing H₂O₂, we perform differential electrochemical measurement by amperometry in which screen-printed Prussian Blue-mediated and nonmediated carbon electrodes are used for differential analysis. We were able to measure H₂O₂ in simulated breath in a concentration-dependent manner in real time, confirming its functionality. This proposed system is versatile, and by modifying the chemistry of the sensing electrodes, our method of differential sensing can be extended to continuous monitoring of other analytes in exhaled breath.

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Ledernez L, Bruch R, Altenburger M, Bergmann M, Urban G
Transient Spark for Bacterial Cleaning of Dental Microcavities
2019 Plasma Medicine, Band: 9, Nummer: 1, Seiten: 39 - 48
KurzfassungIn this work, we present a method that can be used for the disinfection of microcavities such as tooth root canals. The device is aimed to be introduced inside the root canal. The parameters are chosen so that it produces ROS to inactivate bacteria and develops little to no temperature increase within the root canal. Its effect on bacteria is demonstrated using E. coli spread on Agar in a Petri dish.
Bruch R, Urban G, Dincer C
Unamplified gene sensing via Cas9 on graphene
2019 Nat Biomed Eng, Band: 3, Seiten: 419 - 420
KurzfassungAn electrical biosensor that relies on the binding of target nucleic acid sequences to Cas9 immobilized on a graphene field-effect transistor enables the rapid detection of mutations in purified samples without the need for nucleic acid amplification.

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2018

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Hügle M, Dame G, Behrmann O, Rietzel R, Karthe D, Hufert F, Urban G
A lab-on-a-chip for preconcentration of bacteria and nucleic acid extraction
2018 Rsc Adv, Band: 8, Seiten: 20124 - 20130
KurzfassungTo improve detection sensitivity, molecular diagnostics require preconcentration of low concentrated samples followed by rapid nucleic acid extraction. This is usually achieved by multiple centrifugation, lysis and purification steps, for instance, using chemical reagents, spin columns or magnetic beads. These require extensive infrastructure as well as time consuming manual handling steps and are thus not suitable for point of care testing (POCT). To overcome these challenges, we developed a microfluidic chip combining free-flow electrophoretic (FFE) preconcentration (1 ml down to 5 ml) and thermoelectric lysis of bacteria as well as purification of nucleic acids by gel-electrophoresis. The integration of these techniques in a single chip is unique and enables fast, easy and space-saving sample pretreatment without the need for laboratory facilities, making it ideal for the integration into small POCT devices. A preconcentration efficiency of nearly 100% and a lysis/gel-electrophoresis efficiency of about 65% were achieved for the detection of E. coli. The genetic material was analyzed by RT-qPCR targeting the superfolder Green Fluorescent Protein (sfGFP) transcripts to quantify mRNA recovery and qPCR to determine DNA background.
Zimmermann P, Weltin A, Urban G, Kieninger J
Active Potentiometry for Dissolved Oxygen Monitoring with Platinum Electrodes
2018 Sensors, Band: 18, Nummer: 8, Seite: 2404
KurzfassungPotentiometric oxygen monitoring using platinum as the electrode material was enabled by the combination of conventional potentiometry with active prepolarization protocols, what we call active potentiometry. The obtained logarithmic transfer function is well-suited for the measurement of dissolved oxygen in biomedical applications, as the physiological oxygen concentration typically varies over several decades. We describe the application of active potentiometry in phosphate buffered salt solution at different pH and ion strength. Sensitivity was in the range of 60 mV/dec oxygen concentration; the transfer function deviated from logarithmic behavior for smaller oxygen concentration and higher ion strength of the electrolyte. Long-term stability was demonstrated for 60 h. Based on these measurement results and additional cyclic voltammetry investigations a model is discussed to explain the potential forming mechanism. The described method of active potentiometry is applicable to many different potentiometric sensors possibly enhancing sensitivity or selectivity for a specific parameter.

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Dongyang C, Behrmann O, Hufert F, Dame G, Urban G
Capacity of rTth polymerase to detect RNA in the presence of various inhibitors
2018 Plos One, Band: 13, Nummer: 1, Seite: e0190041
KurzfassungThe full potential of the real-time reverse transcription polymerase chain reaction (RT-PCR) as a rapid and accurate diagnostic method is limited by DNA polymerase inhibitors as well as reverse transcriptase inhibitors which are ubiquitous in clinical samples. rTth polymerase has proven to be more resistant to DNA polymerase inhibitors present in clinical samples for DNA detection and also exhibits reverse transcriptase activity in the presence of Mn2+ ions. However, the capacity of rTth polymerase, which acts as DNA polymerase and reverse transcriptase, to detect RNA in the presence of various inhibitors has not been investigated in detail. Herein, the inhibitors originating from various clinical samples such as blood, urine, feces, bodily fluids, tissues and reagents used during nucleic acid extraction were employed to evaluate the capacity of rTth polymerase to detect RNA. The results show that the inhibitors have different inhibitory effects on the real-time RT-PCR reactions by rTth polymerase, and the inhibitory effects are concentration dependent. Additionally, the capacity of rTth polymerase to detect RNA in the presence of various inhibitors is better or at least comparable with its capacity to detect DNA in the presence of various inhibitors. As a consequence, RNA may be directly detected in the presence of co-purified inhibitors or even directly from crude clinical samples by rTth polymerase.

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Dongyang C, Behrmann O, Hufert F, Dame G, Urban G
Direct DNA and RNA detection from large volumes of whole human blood
2018 Sci Rep-uk, Band: 8, Seite: 3410
KurzfassungPCR inhibitors in clinical specimens negatively affect the sensitivity of diagnostic PCR and RT-PCR or may even cause false-negative results. To overcome PCR inhibition, increase the sensitivity of the assays and simplify the detection protocols, simple methods based on quantitative nested real-time PCR and RT-PCR were developed to detect exogenous DNA and RNA directly from large volumes of whole human blood (WHB). Thermus thermophilus (Tth) polymerase is resistant to several common PCR inhibitors and exhibits reverse transcriptase activity in the presence of manganese ions. In combination with optimized concentrations of magnesium ions and manganese ions, Tth polymerase enabled efficient detection of DNA and RNA from large volumes of WHB treated with various anticoagulants. The applicability of these methods was further demonstrated by examining WHB specimens collected from different healthy individuals and those stored under a variety of conditions. The detection limit of these methods was determined by detecting exogenous DNA, RNA, and bacteria spiked in WHB. To the best of our knowledge, direct RNA detection from large volumes of WHB has not been reported. The results of the developed methods can be obtained within 4 hours, making them possible for rapid and accurate detection of disease-causing agents from WHB.

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Dongyang C, Yi Q, Shen C, Lan Y, Urban G, Du W
Direct enrichment of pathogens from physiological samples of high conductivity and viscosity using H-filter and positive dielectrophoresis
2018 Biomicrofluidics, Band: 12, Nummer: 1, Seite: 014109
KurzfassungThe full potential of microfluidic techniques as rapid and accurate methods for the detection of disease-causing agents and foodborne pathogens is critically limited by the complex sample preparation process, which commonly comprises the enrichment of bacterial cells to detectable levels. In this manuscript, we describe a microfluidic device which integrates H-filter desalination with positive dielectrophoresis (pDEP) for direct enrichment of bacterial cells from physiological samples of high conductivity and viscosity, such as cow's milk and whole human blood. The device contained a winding channel in which electrolytes in the samples continuously diffused into deionized (DI) water (desalination), while the bacterial cells remained in the samples. The length of the main channel was optimized by numerical simulation and experimentally evaluated by the diffusion of fluorescein into DI water. The effects of another three factors on H-filter desalination were also investigated, including (a) the flow rate ratio between the sample and DI water, (b) sample viscosity, and (c) non-Newtonian fluids. After H-filter desalination, the samples were withdrawn into the dielectrophoresis chamber in which the bacterial cells were captured by pDEP. The feasibility of the device was demonstrated by the direct capture of the bacterial cells in 1× PBS buffer, cow's milk, and whole human blood after H-filter desalination, with the capture efficiencies of 70.7%, 90.0%, and 80.2%, respectively. We believe that this simple method can be easily integrated into portable microfluidic diagnosis devices for rapid and accurate detection of disease-causing agents and foodborne pathogens.
Matylitskaya V, Kasemann S, Urban G, Dincer C, Partel S
Electrochemical Characterization of Nanogap Interdigitated Electrode Arrays for Lab-on-a-Chip Applications
2018 J Electrochem Soc, Band: 165, Nummer: 3, Seiten: B127 - B134
KurzfassungIn this work we present recent results on electrochemical characterization of the fabricated nanogap interdigitated electrode arrays (nIDAs) for Lab-on-a-Chip applications (LoC). The advantages of the presented nIDAs and their potential for application in bioelectrochemistry were studied using different electrochemical methods. Chronoamperometry is applied to achieve reversible redox processes which lead to an amplification of the measured current compared to a single electrode configuration and as a result, an increase in signal-to-noise ratio. For the electrochemical characterization of the created nIDAs ferrocenemethanol (FcMeOH) and p-aminophenol (pAP) were selected as redox couples. An amplification factor above 160 compared to a single electrode configuration was obtained with FcMeOH for the nIDAs with 100 nm gap. An inverse correlation between gap size and amplification was proven. In addition, the formation of a polymer film during redox cycling could be verified to cause the lower amplification factor observed in pAP measurements. Furthermore, different electrode cleaning procedures were demonstrated by combination of O2 plasma and cyclic voltammetry. The nIDAs presented here offer many advantages including low-cost fabrication, high amplification and collection factors and thus are highly suitable for biosensor applications.

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Urban S, Weltin A, Flamm H, Kieninger J, Deschner BJ, Kraut M, Dittmeyer R, Urban G
Electrochemical multisensor system for monitoring hydrogen peroxide, hydrogen and oxygen in direct synthesis microreactors
2018 Sensor Actuat B-chem, Band: 273, Seiten: 973 - 982
KurzfassungWe present an electrochemical microsensor system for the monitoring of hydrogen peroxide, dissolved hydrogen and dissolved oxygen inside a direct synthesis microreactor. The setup allows the online, in situ measurement of high reactant concentrations by amperometric detection of all three reactants in aqueous solution using chronoamperometric protocols. Hydrogen peroxide is a key chemical for industrial oxidation applications, and its catalyzed direct synthesis is an attractive process route. For the first time, we integrated an electrochemical cell into a high pressure stainless steel microreactor environment (pressures up to 100  bar, pH of 3-4 and presence of bromide) by fabricating sensor plugs with 300  µm platinum microelectrodes encapsulated into a robust epoxy housing. The first microfabricated silver/silver bromide pseudo-reference electrode, integrated by electrodeposition, allowed to obtain a stable measurement potential directly from the electrolyte containing bromide. The investigation of platinum electrochemistry in the presence of bromide by cyclic voltammetry led to the development of chronoamperometric protocols for the stable, precise and reproducible measurement in this environment. Hydrogen peroxide was detected under reaction conditions showing linear behaviour up to 20  mM with high sensitivity of 55  μA  cm⁻²  mM⁻¹ and excellent stability by application of a diffusion limiting hydrogel layer to the electrode surface. This linear range surpasses most micro- and nanostructured platinum approaches. Oxygen and hydrogen were both measured at elevated pressures up to 70  bar and high dissolved concentrations up to 52  mM and 40  mM with measured sensitivities of 26  μA  cm⁻²  mM⁻¹ and 356  μA  cm⁻²  mM⁻¹, respectively. We have successfully shown the application of electrochemical sensors for online, in situ monitoring of analyte concentrations under conditions found in direct synthesis microreactors.
Lehmann K, Yurchenko O, Melke J, Fischer A, Urban G
High electrocatalytic activity of metal-free and non-doped hierarchical carbon nanowalls towards oxygen reduction reaction
2018 Electrochim Acta, Band: 269, Seiten: 657 - 667
KurzfassungUnderstanding the influence of synthesis parameters on morphology and electrochemical properties of carbon nanostructure is necessary for the development of application-tailored materials. We report on the synthesis by plasma enhanced chemical vapor deposition, morphology and catalytic activity towards oxygen reduction reaction (ORR) of hierarchical carbon nanowalls (hCNW) at different deposition times. hCNW are an advancement of common CNW possessing an increased surface area while retaining the ideal mass transport characteristics of common CNW. The hCNW structure results from a synthesis using p-xylene as an aromatic precursor. hCNW are non-doped and metal-free with easily accessible graphitic edge sites at the top of the walls and numerous defects sites located within the porous side walls, which are ideal sites for adsorption and electron transfer. hCNW reveal a high amount of different electrochemically active sites that dominate the material character depending on the deposition time. The hCNW exhibit excellent catalytic activity towards ORR with very high ORR onset potential of 830 mV vs RHE in 0.1  mol L⁻¹ KOH solution and selectivity towards a two electron transfer mechanism. Thereby, the onset is higher than that of several nitrogen doped carbons and one of the highest for pure carbon electrodes. In contrast to other pure carbon materials with similar onsets, oxygen doping of hCNW before the experiments could be ruled out. As such, the results of this paper indicate the existence of inner sphere ORR on sp²-carbon. Additionally, the results emphasize the relevance of often overlooked material properties such as surface accessibility as well as electrical conductivity for ORR.
Kieninger J, Weltin A, Flamm H, Urban G
Microsensor systems for cell metabolism – from 2D culture to organ-on-chip
2018 Lab Chip, Band: 18, Seiten: 1274 - 1291
KurzfassungMicrosensor systems for cell metabolism are essential tools for investigation and standardization in cell cul- ture. Electrochemical and optical read-out schemes dominate, which enable the marker-free, continuous, online recording of transient effects and deliver information beyond microscopy and end-point tests. There has been much progress in microfluidics and microsensors, but the translation of both into standard cell culture procedures is still limited. Within this critical review, we discuss different cell culture formats ranging from standard culture vessels to dedicated microfluidic platforms. Key aspects are the appropriate supply of cells, mass transport of metabolites to the sensors and generation of stimuli. Microfluidics enable the transition from static to dynamic conditions in culture and measurement. We illustrate the parameters oxy- gen (respiration), pH (acidification), glucose and lactate (energy metabolism) as well as short-lived reactive species (ROS/RNS) from the perspective of microsensor integration in 2D and 3D cell culture. We discuss different sensor principles and types, along with their limitations, microfabrication technologies and mate- rials. The state-of-the-art of microsensor platforms for cell culture is discussed with respect to sensor per- formance, the number of parameters and timescale of application. That includes the advances from 2D culture to the increasingly important 3D approaches, with specific requirements for organotypic micro- tissues, spheroids and solid matrix cultures. We conclude on the current progress, potential, benefits and limitations of cell culture monitoring systems from monolayer culture to organ-on-chip systems.

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Kubon M, Hartmann H, Moschallski M, Burkhardt C, Link G, Werner S, Lavalle P, Urban G, Vrana N E, Stelzle M
Multimodal Chemosensor‐Based, Real‐Time Biomaterial/Cell Interface Monitoring
2018 Advanced Biosystems, Seite: 1700236
KurzfassungReal‐time monitoring of the cell/biomaterial interface for biomedical applications can significantly improve the assessment of biomaterials. However, currently there are no multiparametric real‐time monitoring systems for the ex vivo assessment of biomaterials. This study presents a method for monitoring of cell and tissue response to biomaterials based on microsensor read‐outs of pH, O2, and impedance. In vitro, the sensors are compatible with cells implants. For ex vivo measurements, either a biodegradable polymer poly(lactic‐co‐glycolic acid) or a protein‐repellent plasma polymer nanofilm is coated onto sensor arrays and placed on the chorioallantoic membrane of avian embryo ex ovo cultures. Signals related to dissolved oxygen, pH, and electrical impedance are continuously acquired for up to 90 h. Optical observation, immunohistochemical examination of CD45, and Haematoxylin and Eosin (H&E) staining show different unspecific immune responses. Tissue inflammation, capsule formation, and neovascularization are observed. These results correlate well with the type of coating material and the signal patterns acquired by the chemosensors. In addition, tissue death can be inferred from sensor signal patterns. This system is intended to enable continuous monitoring of biomaterials and is envisioned as a prescreening tool to provide real‐time monitoring of cell/biomaterial interface and also to reduce animal testing for biomaterial assessment purposes.
Unmüssig T, Daubinger P, Weltin A, Urban S, Urban G, Kieninger J
Non-enzymatic glucose sensing based on hierarchical platinum micro-/nanostructures
2018 J Electroanal Chem, Band: 816, Seiten: 215 - 222
KurzfassungNon-enzymatic glucose monitoring for biomedical applications asks for long-term stable and selective sensors at neutral pH. A hierarchical platinum micro-/nanostructured electrode along with a novel measurement scheme leads to increased sensitivity, selectivity and stability compared to state-of-the-art. The hierarchical electrode coating was applied by a scalable two-step process, which combined electrochemical deposition and colloidal synthesis to obtain a hierarchical structure with high surface roughness. This three-dimensional structure consists of a cauliflower-like platinum deposition, which is coated by a platinum nanowire network. Amperometric glucose measurements showed a 10,000-fold increase in sensitivity (473  μA  cm⁻²  mM⁻¹) compared to unmodified electrodes and linear behavior in the physiological range. The obtained sensitivities are among the highest values reported for non-enzymatic glucose sensors in neutral pH media. The hierarchical morphology provides a selectivity mechanism depending on the reaction kinetics, improving the selectivity for glucose in the presence of the interferent ascorbic acid 2,000-fold. Selectivity was further enhanced by low-frequency electrochemical impedance spectroscopy (EIS). Chronoamperometric protocols were developed to achieve long-term stability and overcome the loss of sensitivity due to electrode poisoning. Using chronoamperometric protocols for both the amperometry and the EIS measurements improved stability significantly. The presented results make hierarchical platinum micro-/nanostructured electrodes a promising candidate for continuous glucose monitoring.
Marzioch J, Kieninger J, Weltin A, Flamm H, Aravindalochanan K, Sandvik J A, Pettersen E O, Peng Q, Urban G
On-Chip Photodynamic Therapy – Monitoring Cell Metabolism by Electrochemical Microsensors
2018 Lab Chip, Band: 18, Seiten: 3353 - 3360
KurzfassungWe introduce a new system which combines metabolic monitoring by electrochemical microsensors with photodynamic therapy on-chip for the first time. Oxygen consumption of T-47D breast cancer cells was measured during therapy with protoporphyrin IX. We determined the efficacy of therapy and revealed recovery effects, which underlines the high relevance of continuous monitoring.
Kieninger J, Tamari Y, Enderle B, Jobst G, Sandvik JA, Pettersen EO, Urban G
Sensor Access to the Cellular Microenvironment Using the Sensing Cell Culture Flask
2018 Biosensors, Band: 8, Nummer: 2, Seite: 44
KurzfassungThe Sensing Cell Culture Flask (SCCF) is a cell culture monitoring system accessing the cellular microenvironment in 2D cell culture using electrochemical microsensors. The system is based on microfabricated sensor chips embedded in standard cell culture flasks. Ideally, the sensor chips could be equipped with any electrochemical sensor. Its transparency allows optical inspection of the cells during measurement. The surface of the sensor chip is in-plane with the flask surface allowing undisturbed cell growth on the sensor chip. A custom developed rack system allows easy usage of multiple flasks in parallel within an incubator. The presented data demonstrates the application of the SCCF with brain tumor (T98G) and breast cancer (T-47D) cells. Amperometric oxygen sensors were used to monitor cellular respiration with different incubation conditions. Cellular acidification was accessed with potentiometric pH sensors using electrodeposited iridium oxide films. The system itself provides the foundation for electrochemical monitoring systems in 3D cell culture.

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Tanvir N, Yurchenko O, Laubender E, Pohlec R, Sicard O v, Urban G
Zinc peroxide combustion promoter in preparation of CuO layers for conductometric CO₂ sensing
2018 Sensor Actuat B-chem, Band: 257, Seiten: 1027 - 1034
KurzfassungThe detection of CO₂ has applications for both industrial and domestic use due to its high exposure effects on the human health. Conductivity sensors on the other hand, present a cost-effective approach that can be successfully utilized for the detection of CO₂. However, the integration of metal oxide based nanoparticles layers for conducometric sensing is complicated and requires improvement in the layer quality to achieve effective and stable gas sensing properties. Addressing this challenge, we present in this work, p-type semiconducting CuO nanoparticles as a CO₂ gas sensitive material and introduce a combination of organic binder and peroxide such as ZnO₂ for improved gas sensitive layer quality. The addition of ZnO₂ to CuO nanoparticles enables the layers annealing at 300 °C which makes the preparation method compatible to silicon based gas sensing devices. For the characterization of layers, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and Fourier transform infrared measurements are employed. The CO₂ gas sensing measurements show a reversible change in resistance suggesting hybrid nanoparticles layers as an efficient gas sensitive material. The measurements performed at different humidity levels for CuO-ZnO₂ (10:1) layer indicate different sensing mechanism for dry conditions in comparison to the measurements performed under humid atmosphere. The Lewis acid-base reaction between oxide oxygen and CO₂ has been proposed as sensing mechanism for the measurements in dry air, whereas the formation of surface barriers between nano-grains due to the reaction with CO₂ has been suggested for the CO₂ response under humid conditions.

2017

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Partel S, Kasemann S, Matylitskaya V, Thanner C, Dincer C, Urban G
A simple fabrication process for disposable interdigitated electrode arrays with nanogaps for lab-on-a-chip applications
2017 Microelectron Eng, Band: 173, Seiten: 27 - 32
KurzfassungIn this paper, we introduce for the first time a novel fabrication process for interdigitated electrode arrays (IDA) with nanogaps on polymer substrates. The IDA sensor for disposable lab-on-a-chip (LoC) applications employs an amperometric detection principle which allows a signal amplification by redox cycling. Our fabrication sequence is based on a lift-off free process and therefore, reduces the number of process steps and simplifies the fabrication and increases the yield. This innovative approach consists of an initial structure followed by two deposition processes. The initial structure, which is transferred into the polymer, is in the micrometer range and is formed by hot embossing. A silicon stamp is fabricated by mask aligner lithography and a subsequent dry etching step. An imprint template was prepared from the master and the structures are transferred into a 1 mm thick cycle-olefin polymer (COP) sheet. A subsequent sputter deposition process was carried out to form an undercut of the finger structures, which should guarantee a separation of the electrodes. A 90 nm thick gold layer was deposited by thermal evaporation to pattern the electrodes. The presented fabrication procedure represents an approach to fabricate disposable nanogap interdigitated electrode arrays allowing high signal amplifications in LoC applications. Furthermore, it demonstrates a low-cost method to fabricate IDAs with nanogaps for high volume mass production.
Weltin A, Hammer S, Noor F, Kaminski Y, Kieninger J, Urban G
Accessing 3D Microtissue Metabolism: Lactate and Oxygen Monitoring in Hepatocyte Spheroids
2017 Biosens Bioelectron, Band: 87, Seiten: 941 - 948
Kurzfassung3D hepatic microtissues, unlike 2D cell cultures, retain many of the in-vivo-like functionalities even after long-term cultivation. Such 3D cultures are increasingly applied to investigate liver damage due to drug exposure in toxicology. However, there is a need for thorough metabolic characterization of these microtissues for mechanistic understanding of effects on culture behaviour. We measured metabolic parameters from single human HepaRG hepatocyte spheroids online and continuously with electrochemical microsensors. A microsensor platform for lactate and oxygen was integrated in a standard 96-well plate. Electrochemical microsensors for lactate and oxygen allow fast, precise and continuous long-term measurement of metabolic parameters directly in the microwell. The demonstrated capability to precisely detect small concentration changes by single spheroids is the key to access their metabolism. Lactate levels in the culture medium starting from 50 μM with production rates of 5 μM h⁻¹ were monitored and precisely quantified over three days. Parallel long- term oxygen measurements showed no oxygen depletion or hypoxic conditions in the microwell. Increased lactate production by spheroids upon suppression of the aerobic metabolism was observed. The dose-dependent decrease in lactate production caused by the addition of the hepatotoxic drug Bosentan was determined. We showed that in a toxicological application, metabolic monitoring yields quantitative, online information on cell viability, which complements and supports other methods such as microscopy. The demonstrated continuous access to 3D cell culture metabolism within a standard setup improves in vitro toxicology models in replacement strategies of animal experiments. Controlling the microenvironment of such organotypic cultures has impact in tissue engineering, cancer therapy and personalized medicine.
Dincer C, Bruch R, Wirth S, Schumann S, Urban G
Biosensors and personalized drug therapy: what does the future hold?
2017 Expert Review of Precision Medicine and Drug Development, Band: 2, Nummer: 6, Seiten: 303 - 305
Ayed D, Laubender E, Souiri M, Yurchenko O, Marmouch H, Urban G, Othmane A
Carbon Nanotubes Supported Ru-Au Nanoparticles with Core-Shell Structure for Glucose Detection with High Resistance against Chloride Poisoning
2017 J Electrochem Soc, Band: 164, Nummer: 14, Seiten: B767 - B775
KurzfassungBimetallic Au-Ru nanoparticles (NPs) with novel core-shell morphology were prepared through a single-step microemulsion synthesis for the decoration of COOH surface modified multi-walled carbon nanotubes (fMWCNTs). The presence of Ru leads to particles with smaller diameters, improved distribution and adhesion on fMWCNTs, affording very good accessibility to the catalytic sites. Thereby, Ru exists in a highly amorphous state in the shell and as a solid solution in the gold lattice of the core. The effect of Ru on the activity and effectiveness of the catalyst were studied in alkaline solutions. Au-RuNPs/fMWCNTs exhibits a high sensitivity of 28.7 μA mM¹ cm⁻² toward glucose and provides a linear range for physiological concentrations (1 mM–10 mM). Contrary to Au the Au-RuNPs/fMWCNTs electrode is highly resistant against poisoning by chloride ions, and the interference from the oxidation of common interfering species is effectively suppressed. Additionally, the presence of other sugars affects only marginally the response toward glucose. The role of Ru and the special core-shell morphology are discussed. The Au-RuNPs/fMWCNTs electrode exhibits good selectivity, high sensitivity toward glucose oxidation and applicability for glucose detection in real human serum samples, thus is promising for the future development of non-enzymatic glucose sensors.
Bruch R, Chatelle C, Kling A, Rebmann B, Wirth S, Schumann S, Weber W, Dincer C, Urban G
Clinical on-site monitoring of ß-lactam antibiotics for a personalized antibiotherapy
2017 Sci Rep-uk, Band: 7, Seite: 3127
KurzfassungAn appropriate antibiotherapy is crucial for the safety and recovery of patients. Depending on the clinical conditions of patients, the required dose to effectively eradicate an infection may vary. An inadequate dosing not only reduces the efficacy of the antibiotic, but also promotes the emergence of antimicrobial resistances. Therefore, a personalized therapy is of great interest for improved patients’ outcome and will reduce in long-term the prevalence of multidrug-resistances. In this context, on-site monitoring of the antibiotic blood concentration is fundamental to facilitate an individual adjustment of the antibiotherapy. Herein, we present a bioinspired approach for the bedside monitoring of free accessible ß-lactam antibiotics, including penicillins (piperacillin) and cephalosporins (cefuroxime and cefazolin) in untreated plasma samples. The introduced system combines a disposable microfluidic chip with a naturally occurring penicillin-binding protein, resulting in a high-performance platform, capable of gauging very low antibiotic concentrations (less than 6 ng ml⁻¹) from only 1 μl of serum. The system’s applicability to a personalized antibiotherapy was successfully demonstrated by monitoring the pharmacokinetics of patients, treated with ß-lactam antibiotics, undergoing surgery.

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Bruch R, Kling A, Urban G, Dincer C
Dry Film Photoresist-based Electrochemical Microfluidic Biosensor Platform: Device Fabrication, On-chip Assay Preparation, and System Operation
2017 Jove-j Vis Exp, Band: 127, Seite: e56105
KurzfassungIn recent years, biomarker diagnostics became an indispensable tool for the diagnosis of human disease, especially for the point-of-care diagnostics. An easy-to-use and low-cost sensor platform is highly desired to measure various types of analytes (e.g., biomarkers, hormones, and drugs) quantitatively and specifically. For this reason, dry film photoresist technology—enabling cheap, facile, and high-throughput fabrication—was used to manufacture the microfluidic biosensor presented here. Depending on the bioassay used afterwards, the versatile platform is capable of detecting various types of biomolecules. For the fabrication of the device, platinum electrodes are structured on a flexible polyimide (PI) foil in the only clean-room process step. The PI foil serves as a substrate for the electrodes, which are insulated with an epoxy-based photoresist. The microfluidic channel is subsequently generated by the development and lamination of dry film photoresist (DFR) foils onto the PI wafer. By using a hydrophobic stopping barrier in the channel, the channel is separated into two specific areas: an immobilization section for the enzyme-linked assay and an electrochemical measurement cell for the amperometric signal readout. The on-chip bioassay immobilization is performed by the adsorption of the biomolecules to the channel surface. The glucose oxidase enzyme is used as a transducer for electrochemical signal generation. In the presence of the substrate, glucose, hydrogen peroxide is produced, which is detected at the platinum working electrode. The stop-flow technique is applied to obtain signal amplification along with rapid detection. Different biomolecules can quantitatively be measured by means of the introduced microfluidic system, giving an indication of different types of diseases, or, in regard to therapeutic drug monitoring, facilitating a personalized therapy.
Matylitskaya V, Kasemann S, Urban G, Dincer C, Partel S
Electrochemical Characterization of Nanogap Interdigitated Electrode Arrays for Lab-on-a-Chip Applications
2017 ECS Transactions, Band: 80, Nummer: 10, Seiten: 1295 - 1308
KurzfassungIn this work we present recent results on electrochemical characterization of the fabricated nanogap interdigitated electrode arrays (nIDAs) for Lab-on-a-Chip applications. The advantages of the presented nIDAs and their potential for application in bioelectrochemistry were studied using different electrochemical methods. Chronoamperometry is applied to achieve reversible redox processes which lead to an amplification of the measured current compared to a single electrode configuration and as a result,an increase in signal-to-noise ratio. For the electrochemical characterization of the created nIDAs ferrocenemethanol (FcMeOH) and p-aminophenol (pAP) were selected as redox couples. An amplification factor above 160 was obtained with FcMeOH for the nIDAs with 100 nm gap. An inverse correlation between gap size and amplification was proven. In addition, the formation of a polymer film during redox cycling could be verified to cause the lower amplification factor observed in pAP measurements. Furthermore, different electrode cleaning procedures were demonstrated by combination of O₂ plasma and cyclic voltammetry. The nIDAs presented here offer many advantages including low-cost fabrication, high amplification and collection factors and thus are highly suitable for biosensor applications.
Hepp C J, Krogmann F T, Urban G
Flow Rate Independent Sensing of Thermal Conductivity in a Gas Streamby a Thermal MEMS-Sensor - Simulation and Experiments
2017 Sensor Actuat A-phys, Band: 253, Seiten: 136 - 145
KurzfassungA thermal system for measuring thermal conductivity in a streaming gas is presented. The system features a heating element and a downstream temperature sensor on a membrane area surrounded by a substrate serving as heat sink. Simulations predict a flow independent region by use of the FEM heat transfer model in all directions in a laminar flow profile. Both simulation and experimental results show that the temperature of the downstream element is sensitive towards the gas type but insensitive towards the gas flow over a wide range. Furthermore, the findings show that the temperature of the downstream element in the flow independent region only depends on the gas’ thermal conductivity. The distance between the heater and the downstream temperature sensor is found to be a design parameter in order to shift the flow independent region according to the requirements of the application. The experimental results correspond very well to the theoretical predictions.
Lehmann K, Yurchenko O, Heilemann A, Vierrath S, Zielke L, Thiele S, Fischer A, Urban G
High surface hierarchical carbon nanowalls synthesized by plasma deposition using an aromatic precursor
2017 Carbon, Band: 118, Seiten: 578 - 587
KurzfassungHierarchical carbon nanowalls (CNW) are synthesized by plasma-enhanced chemical vapor deposition using p-xylene as a complex precursor. In contrast to ordinary CNW, synthesized with short-chained carbons, hierarchical CNW show a unique multi-scale pore structure, made up of micro- and mesopores connected by tubular macropores, offering higher surface area and surface accessibility. Their morphology, graphitic structure, surface area and accessibility are verified by transmission and scanning electron microscopy, gas sorption and impedance spectroscopy. Focused ion beam scanning electron microscopy tomography demonstrates the presence of macropores ensuring pore connectivity down to the substrate. Nitrogen/krypton physisorption confirms the micro- and mesoporous structure contributing extensively to the surface area. The impedance spectra are evaluated according to standard RC and transmission line models. The sample deposited for 60 min, with a structure height of 4.75 μm, features a volumetric capacitance of 2.6 F cm⁻³ and a response time of 25 ms. Hierarchical CNW exhibit a two to six times higher volumetric capacitance than CNW of similar proportions, reported in literature. Hierarchical CNW offer a promising way to realize high power and energy density requirements in electrochemical energy systems, like supercapacitors, due to their good conductivity, high surface area and open pore structure.
Ring A, Sorg H, Weltin A, Tilkorn D J, Kieninger J, Urban G, Hauser J
In-vivo monitoring of infection via implantable microsensors: a pilot study
2017 Biomed Eng-biomed Te
KurzfassungThe most common complication after implantation of foreign material is infection, leading to implant failure and severe patient discomfort. Smoldering-infections proceed inapparently and might not get verified by radiological diagnostics. Early identification of this type of infection might significantly reduce the rate of complications. Therefore, we manufactured a microsensor strip in a hybrid of thin-film and laminate technology in a wafer-level process. It comprises electrochemical, amperometric microsensors for glucose, oxygen and lactate as well as an integrated reference electrode. Microsensors have been implanted in the mouse dorsal skin fold chamber, which got inoculated with a human-pathogen bacterial strain. A selective signal could be measured for all parameters and time points. The infection led to measurable changes of the wound environment as given by a decrease of the oxygen- as well as the glucose-concentration while the lactate concentration increased markedly over time. The given results in this study are the first hints on a promising new tool and should therefore be interpreted as a proof of the principle to show the functionality of the microsensors in an in vivo setting. These microsensors could be used to monitor smoldering infections of implantable foreign materials reducing foreign implant associated complications.
Enderle B, Moser I, Kannan C, Schwab K O, Urban G
Interstitial Glucose and Lactate Levels Are Inversely Correlated With the Body Mass Index: Need for In Vivo Calibration of Glucose Sensor Results With Blood Values in Obese Patients
2017 Journal of Diabetes Science and Technology
KurzfassungContinuously measured glucose and lactate levels in interstitial fluid (ISF) may markedly differ from their respective blood levels. Combining microdialysis with a bioanalytical microsystem, the interstitial glucose and lactate concentrations of eight male volunteers with different body mass index (BMI) were monitored during a 2-fold glucose tolerance test over the period of three hours. Significant correlations were found between abdominally measured sensor results and reference measurements (R² = .967 for glucose and R² = .936 for lactate, P < .05). The physiological delay of the abdominally observed glucose appearance in the ISF correlated positively with the BMI (R² = .787, P < .05). The relative in vivo recovery of glucose and lactate was inversely proportional to the BMI of the volunteers (R² = .540 for glucose, R² = .609 for lactate, P < .05). One subject with a BMI of > 34 kg/m² showed abdominally as well as the antebrachially significantly reduced tissue glucose values compared to blood glucose values (P < .001). A very good correlation between abdominally measured sensor results and the results of the reference method verified the reliability of the BioMEMS. The abdominally measured glucose level in ISF decreased significantly with increasing BMI. Therefore, an in vivo calibration of glucose levels in ISF with blood levels seems to be necessary especially in markedly obese subjects.
Tanvir N, Yurchenko O, Laubender E, Urban G
Investigation of low temperature effects on work function based CO₂ gas sensing of nanoparticulate CuO films
2017 Sensor Actuat B-chem, Band: 247, Seiten: 968 - 974
KurzfassungThe gas sensing behavior of semiconducting nanoparticulate copper oxide (CuO‐NPs) towards CO₂ with respect to different conditions affecting the signal response is investigated with the help of adsorption induced work function changes. Work function measurements have been carried out with the help of Kelvin probe. The analysis of cross‐sensitivities to humidity is conducted in the low temperature range between 25 °C and 110 °C and it is shown that for CuO‐NPs, optimization of work function based CO₂ sensing is possible by using a combined effect of humidity and temperature. Furthermore, the temperature induced effects during CO₂ sensing are explained using considerations of kinetics and thermodynamics of the process. We show that moderate temperatures of about 65 °C exert a positive influence on the kinetics of chemical processes occurring on the CuO‐NPs surface in the presence of water and CO₂ as well as counterbalance the negative impact of high humidity dependence on CO₂ gas sensing. However starting from 65 °C, CO₂ response decreases owing to a negative effect of temperature on the thermodynamics of the sensing reaction. Compared to other metal oxide based materials for CO₂ sensing, CuO‐NPs show promising results and enables the prospect towards the development of new CO₂ gas sensor operable at low temperatures.
Burger J, Rath C, Woehrle J, Meyer P A, Ben Ammar N, Kilb N, Brandstetter T, Proell F, Proll G, Urban G, Roth G
Low-Volume Label-Free Detection of Molecule-Protein Interactions on Microarrays by Imaging Reflectometric Interferometry
2017 SLAS TECHNOLOGY: Translating Life Sciences Innovation, Band: 22, Nummer: 4, Seiten: 437 - 446
KurzfassungThis system allows the high-throughput protein interaction analysis on microarrays. We apply the interference technology 1λ–imaging reflectometric interferometry (iRIf) as a label-free detection method and create microfluidic flow cells in microscope slide format for low reagent consumption and lab work compatibility. By now, most prominent for imaging label-free interaction analyses on microarrays are imaging surface plasmon resonance (SPR) methods, quartz crystal microbalance, or biolayer interferometry. SPR is sensitive against temperature drifts and suffers from plasmon crosstalk, and all systems lack array size (maximum 96 spots). Our detection system is robust against temperature drifts. Microarrays are analyzed with a spatial resolution of 7 µm and time resolution of ≤50 fps. System sensitivity is competitive, with random noise of <5 × 10⁻⁵ and baseline drift of <3 × 10⁻⁶. Currently available spotting technologies limit array sizes to ~4 spots/mm² (1080 spots/array); our detection system would allow ~40 spots/mm² (10,800 spots/array). The microfluidic flow cells consist of structured PDMS inlays sealed by versatilely coated glass slides immobilizing the microarray. The injection protocol determines reagent volumes, priming rates, and flow cell temperatures for up to 44 reagents; volumes of ≤300 µL are validated. The system is validated physically by the biotinylated bovine serum albumin streptavidin assay and biochemically by thrombin aptamer interaction analysis, resulting in a KD of ~100 nM.
Purkl F, Daus A, English T, Provine J, Feyh A, Urban G, Kenny T
Measurement of Young's modulus and residual stress of atomic layer deposited Al₂O₃ and Pt thin films
2017 J Micromech Microeng, Band: 27, Nummer: 8, Seite: 085008
KurzfassungThe accurate measurement of mechanical properties of thin films is required for the design of reliable nano/micro-electromechanical devices but is increasingly challenging for thicknesses approaching a few nanometers. We apply a combination of resonant and static mechanical test structures to measure elastic constants and residual stresses of 8 nm to 27 nm-thick Al₂O₃ and Pt layers which have been fabricated through atomic layer deposition. The Young's modulus of poly-crystalline Pt films was found to be reduced by less than 15% compared to the bulk value, whereas for amorphous Al₂O₃ it was reduced to about half of its bulk value. We observed no discernible dependence of the elastic constant on thickness or deposition method for Pt, but the use of plasma-enhanced atomic layer deposition was found to increase the Young's modulus of Al₂O₃ by 10% compared to a thermal atomic layer deposition. As deposited, the Al₂O₃ layers had an average tensile residual stress of 131 MPa. The stress was found to be higher for thinner layers and layers deposited without the help of a remote plasma. No residual stress values could be extracted for Pt due to insufficient adhesion of the film without an underlying layer to promote nucleation.
Hepp C J, Krogmann F T, Urban G
Multi Parameter monitoring of Binary Gas Mixtures: Concentration and Flow Rate by DC Excitation of Thermal Sensor Arrays
2017 Sensor Actuat A-phys, Band: 265, Seiten: 32 - 39
KurzfassungThis contribution presents a thermal sensor, which is capable of simultaneously determining gas concentrations of a binary gas mixture under flow conditions and its flow rate. The sensor design corresponds to the calorimetric principle. The multi parameter detection is achieved by the use of two time independent excitation modes (power and temperature). Due to the developed sensor design, a flow independent, but gas sensitive region is obtained in power mode. In this flow range, the thermal conductivity is measured by analyzing the temperature of the downstream element. Gas concentration of the binary gas mixture is derived from the theoretical relationship to thermal conductivity. Afterwards, the flow rate is detected by evaluating the temperature difference between the down- and upstream temperature sensors in temperature excitation mode. This measurement technique has been successfully proven under laboratory conditions, where a flowing mixture of e.g. methane and carbon dioxide has been analyzed. The carried out measurements show an accuracy of ±5% in gas concentration and of ±3.3% in flow rate. This measuring method seems to be sufficient to analyze biogas in anaerobic distinctions. However, further investigation is needed to open this technique for this application.
Dincer C, Bruch R, Kling A, Dittrich P, Urban G
Multiplexed Point-of-Care Testing – xPOCT
2017 Trends Biotechnol, Band: 35, Nummer: 8, Seiten: 728 - 742
KurzfassungMultiplexed point-of-care testing (xPOCT), which is simultaneous on-site detection of different analytes from a single specimen, has recently gained increasing importance for clinical diagnostics, with emerging applications in resource-limited settings (such as in the developing world, in doctors’ offices, or directly at home). Nevertheless, only single-analyte approaches are typically considered as the major paradigm in many reviews of point-of-care testing. Here, we comprehensively review the present diagnostic systems and techniques for xPOCT applications. Different multiplexing technologies (e.g., bead- or array-based systems) are considered along with their detection methods (e.g., electrochemical or optical). We also address the unmet needs and challenges of xPOCT. Finally, we critically summarize the in-field applicability and the future perspectives of the presented approaches.

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Qazzazie D, Yurchenko O, Urban S, Kieninger J, Urban G
Platinum nanowires anchored on graphene-supported platinum nanoparticles as highly active electrocatalyst towards glucose oxidation for fuel cell applications
2017 Nanoscale, Band: 9, Seiten: 6436 - 6447
KurzfassungThe limited performance of platinum-based electrocatalysts for glucose electrooxidation is a major concern for glucose fuel cells, since glucose electrooxidation is characterized by slow reaction kinetics and low diffusion coefficient. Here, the presented graphene-supported platinum-based hierarchical nanostructures attain highly enhanced electrocatalytic activity towards glucose oxidation. Platinum nanoparticles electrodeposited on graphene support retain mechanical stability and act as junctions allowing a reliable, smooth and dense growth of platinum nanowires with extremely small diameters (>10 nm) on graphene. The electrode’s surface roughness was increased by factors up to 4000 to the geometrical surface area enabling maximized exploitation of the electrocatalytic activity of platinum and efficient electron transfer between nanowires and substrate. The unique three-dimensional geometry of these hierarchical nanostructures has a significant impact on their catalytic performance offering short diffusional paths for slow glucose species, thus, mass transport limitations are optimized leading to lower polarization losses. This was examined by galvanostatic measurements of the operation as anodes in glucose half-cells at conditions corresponding to implantable glucose fuel cells. The presented hierarchical nanostructures show remarkably enhanced catalytic performance for glucose electrooxidation, i.e. negatively shifted open circuit potential of -580 mV vs. Ag/AgCl, hence, representing appropriate electrocatalysts for uses as anodes in glucose fuel cells. In combination with a non-metal N-doped graphene cathode, a cell potential of 0.65 V was achieved at a galvanostatic load of 17.5 µA cm⁻² which noticeably surpasses the performance of state of the art catalysts for aforementioned operation conditions.
Al-Halhouli M, Kieninger J, Yurchenko O, Urban G
Rational design of morphological characteristics to determine the optimal hierarchical nanostructures in heterogeneous catalysis
2017 Chemcatchem, Band: 9, Seiten: 354 - 364
KurzfassungThis work draws attention to the optimal hierarchical nanostructures morphology and the morphological characteristics that lead to a rational design of heterogeneous nanocatalysts, especially for reactions exhibiting sluggish kinetics. A simplified methanol oxidation on two types of hierarchical nanostructures, external and internal, is reported. A complex system of asymmetric geometries was simplified by mapping 3D geometries into 2D using mass transport approach. Macropore-size turned out to be the most comprehensive characteristic for evaluating specific activity and current density of hierarchical nanostructures. The optimal current densities for both types of nanostructures were achieved in macropore-size ranges of 3.2 - 4.5 µm and 1.9 - 3.2 µm, respectively. The optimal mass activity of internal nanostructures was achieved at the porosity range of 40 - 50% whereas the optimal mass activity of external hierarchical nanostructures was achieved at high porosity values. External hierarchical nanostructures in comparison to internal hierarchical nanostructures tend to be the cost-effective catalysts that have high catalytic activity.

2016

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Nguyen T, Tiberius B, Pliquett U, Urban G
An Impedance Biosensor For Monitoring Cancer Cell Attachment, Spreading And Drug-Induced Apoptosis
2016 Sensor Actuat A-phys, Band: 241, Seiten: 231 - 237
KurzfassungIn the last three decades, Electrical Cell-substrate Impedance Sensing (ECIS) has emerged as a powerful technique for in vitro cellular research and preclinical testing. In this study, a cell-based impedance biosensor based on ECIS technique, which integrates microelectrode arrays with a small culture chamber has been developed for monitoring the attachment, spreading and drug-induced apoptosis of very few MCF-7 breast cancer cells. It was found out that cell spreading caused a significant increase of impedance magnitude in the frequency range between 10 kHz and 100 kHz and also pronounced phase shift. Using an electrical equivalent circuit to model the measured spectra, the morphological change of cells was analyzed. Cell spreading induced a slight decrease of membrane capacitance of 2 % and a prominent increase of membrane resistance of 57 % within incubating for nearly one day. For pharmaceutical assessment, the cells were treated with different concentrations of an anti-cancer drug (Cisplatin) in the range from 10 μM to 50 μM. We observed a fast decrease of impedance magnitude within the initial 4 h of treatment with concentrations of 25 μM and 50 μM. The results derived from this study demonstrated the usability of cell-based impedance microbiosensors in cell biology and cancer research.
Pentyala V, Davydovskaya P, Ade M, Pohle R, Urban G
Carbon dioxide gas detection by open metal site metal organic frameworks and surface functionalized metal organic frameworks
2016 Sensor Actuat B-chem, Band: 225, Seiten: 363 - 368
KurzfassungNovel nanoporous materials known as Metal-Organic Frameworks (MOFs) are currently attracting wide attention due to their potential applications such as gas storage, gas separation and catalysis. Recently, MOF materials were also developed for chemical sensors. In this work, for the first time iso-structural MOFs M-MOF-74 (where M = Mg, Ni, Co and Zn) and ethylenediamine functionalized Mg-MOF-74 were investigated as selective CO₂ gas sensing material for the work function read-out based method at ambient temperature and different humidity levels. M-MOF-74s are very interesting MOFs because they contain coordinatively unsaturated metal centers where adsorbates can interact strongly with their affinity towards gas molecules. Interaction of the CO₂ molecules with open metal sites or amine-functional groups changes the work function (ΔΦ) of sensing layer which can serve as a signal for gas sensors. Results show that ethylenediamine functionalized Mg-MOF-74 exhibited enhanced CO₂ gas sensing properties compared to other M-MOF-74 with respect to sensitivity, reversibility and stability.
Qazzazie D, Al-Halhouli M, Yurchenko O, Urban G
Control over fuel cell performance through modulation of pore accessibility: investigation and modeling of carbon nanotubes effects on oxygen reduction at N-graphene-based nanocomposite
2016 Nanotechnology, Band: 27, Seite: 475401
KurzfassungThe lack of performance of graphene-based electrocatalysts for oxygen reduction (ORR) is a major concern for fuel cells which can be mastered using nanocomposites. This work is highlighted by the optimization of nitrogen(N)-doped graphene/carbon nanotubes (CNTs) nanocomposite’s ORR performance examined by galvanostatic measurements in realistically approached glucose half-cells. Obtained results mark an essential step for the development of nanocarbon-based cathodes, as we specifically evaluate the electrode performance under real fuel cell conditions. The 2D simulations exclusively represent an important approach for understanding the catalytic efficiency of the nanocomposite with unique structure. The kinetics features extracted from simulations are consistent with the experimentally determined kinetics. The morphology analysis reveals a 3D porous structure. The results demonstrate that the incorporation of CNTs implements mesoscale channels for improved mass transport and leads to efficient 4-electron transfer and enhanced overall catalytic activity in pH-neutral media. The nanocomposite shows increased specific surface area of 142 m² g⁻¹, positively shifted ORR onset potential of 67 mV and higher open circuit potential of 268 mV versus Ag/AgCl compared to N-graphene (11 m² g⁻¹, −17, 220 mV). The findings are supported by 2D simulations giving qualitative evidence to the significant role of CNTs for achieving better accessibility of pores, i.e. enabling improved transfer of oxygen and OH−, and providing more reaction sites in the nanocomposite. The nanocomposite demonstrates better ORR performance than constituent components regarding potential application in miniaturized single-compartment glucose-based fuel cells.
Dincer C, Kling A, Chatelle C, Armbrecht L, Kieninger J, Weber W, Urban G
Designed miniaturization of microfluidic biosensor platforms using the stop-flow technique
2016 Analyst, Band: 141, Seiten: 6073 - 6079
KurzfassungHere, we present a novel approach to increase the degree of miniaturization as well as the sensitivity of biosensor platforms by optimization of microfluidic stop-flow techniques independent of the applied detection technique (e.g. electrochemical or optical). The readout of labeled bioassays, immobilized in a microfluidic channel, under stop-flow conditions leads to a rectangular shaped peak signal. Data evaluation using the peak height allows for a high level miniaturization of the channel geometries. To study the main advantages and limitations of this method by numerical simulations, a universally applicable model system is introduced for the first time. Consequently, proof-of-principle experiments were successfully performed with standard and miniaturized versions of an electrochemical biosensor platform utilizing a repressor protein-based assay for tetracycline antibiotics. Herein, the measured current peak heights are the same despite the sextuple reduction of the channel dimensions. Thus, it results in a 22-fold signal amplification compared to the constant flow measurements in the case of the miniaturized version.

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Lehmann K, Yurchenko O, Urban G
Effect of Aromatic Precursor Flow Rate on Morphology and Properties of Carbon Nanostructures in Plasma Enhanced Chemical Vapor Deposition
2016 Rsc Adv, Band: 6, Seiten: 32779 - 32788
KurzfassungUnderstanding the effects of the synthesis parameters on the morphology and electrochemical properties of nanocarbon layers is a key step in the development of application-tailored nanostructures. In this paper we used an aromatic carbon as a new kind of precursor for the synthesis of carbon based nanostructures by plasma enhanced chemical vapor deposition (PECVD). Complex precursor molecules enable a new degree of influence over the atomic structure of PECVD synthesized carbons. Here, we report on the synthesis and characterization of the nanostructures resulting from varied flow rates of p-xylene used as carbon precursor. By changing the flow rate of the precursor, three different morphologies with graphitic character were synthesized. The resulting structures were carbon nanofibers (CNF), freestanding carbon nanowalls (fCNW) and interconnected carbon nanowalls (iCNW), formed at flow rates of 3 ml h⁻¹, between 1 and 3 ml h⁻¹ and less than 1 ml h⁻¹, respectively. Structural characterization by transmission electron microscopy and Raman spectroscopy indicate a lower defect density for the CNF in comparison to the CNW nanostructures. The electrochemical characterization of the oxygen reduction reaction onset potential and effective surface area feature a significantly higher onset at around −171 mV and an electrochemically active surface area of 0.76 μm⁻¹ for the iCNW compared to −196 mV, 0.61 μm⁻¹ and 0.22 μm⁻¹ for the fCNW and CNF, respectively. The similarities in defect density and differences in activity observed for the iCNW and fCNF suggest that the kind of the defects determines the electrochemical properties. Thus, the iCNW was identified as the most appropriate morphology for further investigations.
Ghodsi J, Hajian A, Rafati A A, Shoja Y, Yurchenko O, Urban G
Electrostatically Immobilized Hemoglobin on Silica-Coated Magnetic Nanoparticles for Simultaneous Determination of Dopamine, Uric Acid, and Folic Acid
2016 J Electrochem Soc, Band: 163, Nummer: 13, Seiten: B609 - B616
KurzfassungThis work describes the development of a novel biosensor for simultaneous determination of dopamine, uric acid, and folic acid by carbon paste electrode modified by hemoglobin which is electrostatically immobilized on silica-coated magnetic nanoparticles and multi-walled carbon nanotubes. Peroxidase properties of hemoglobin nominate this protein as an abundant and inexpensive alternative for costly peroxidase enzymes in dopamine biosensor fabrication. Silica-coated nanoparticles of Fe₃O₄ as a suitable support for hemoglobin immobilization can enhance the loading and stability of hemoglobin. Magnetic nanoparticles were synthesized via a simple co-precipitation method and then were coated with silica to immobilize hemoglobin electrostatically on them. All synthesis and modification steps were characterized by different techniques and then the conditions of hemoglobin immobilization on magnetic nanoparticles were optimized. Multi-walled carbon nanotubes were used as an additional modifier of carbon paste electrode because of their high electroactive surface area and interesting electrocatalytic properties. The modified carbon paste electrode provided a sensitive and stable biosensor for simultaneous determination of dopamine, uric acid, and folic acid whose performance is much better than those of many previously reported sensors. The detection limits were calculated to be about 12 nM, 14 nM and 18 nM and the linear range for determination of DA, UA and FA are 1–30.6 μM, 1–286 μM and 1–369 μM, for dopamine, uric acid, and folic acid, respectively. Finally, the applicability of the proposed biosensor was verified by dopamine evaluation in serum samples.
Bin Tanvir N, Yurchenko O, Urban G, Wilbertz C
Investigation of CO₂ reaction with copper oxide nanoparticles for room temperature gas sensing
2016 J Mater Chem A, Band: 4, Seiten: 5294 - 5302
KurzfassungThe sensing of CO₂ at room temperature enables the prospects towards low power and low cost CO₂ gas sensors and has a high demand in both industrial and domestic applications. In this work we report detailed work function read out (Kelvin probe) based analysis on copper oxide nanoparticles (CuO NPs) as a new CO₂ gas sensitive material. The reversible interactions of CO₂ with thick CuO NPs layer result in a work function change of about 42 mV for dry air and approximately 97 mV for humid conditions (r.h. = 20%), at a CO₂ concentration step of 400 to 4000 ppm. The CO₂ gas sensing mechanism at room temperature is studied by Fourier transform infrared (FTIR) spectroscopy and explained by thermodynamical calculations. The correlation found between the FTIR-spectrum and thermodynamical studies suggest the reversible formation of hydroxocarbonates (malachite, azurite) which is responsible for the gas sensing effect. Moreover, the results concerning long term signal stability over time present suitability towards indoor gas sensing applications. The results indicated in this paper give a new direction to metal oxide based nanoparticles as sufficiently fast and sensitive ambient CO₂ detecting materials.
Partel S, Dincer C, Kasemann S, Kieninger J, Edlinger J, Urban G
Lift-Off Free Fabrication Approach for Periodic Structures with Tunable Nano Gaps for Interdigitated Electrode Arrays
2016 Acs Nano, Band: 10, Nummer: 1, Seiten: 1086 - 1092
KurzfassungWe report a simple, low-cost and lift-off free fabrication approach for periodic structures with adjustable nanometer gaps for interdigitated electrode arrays (IDAs). It combines an initial structure and two deposition process steps; first a dielectric layer is deposited, followed by a metal evaporation. The initial structure can be realised by lithography or any other structuring technique (e.g. nano imprint, hot embossing or injection moulding). This method allows the fabrication of nanometer sized gaps and completely eliminates the need for a lift-off process. Different substrate materials like silicon, Pyrex® or polymers can be used. The electrode gap is controlled primarily by sputter deposition of the initial structure, and thus, adjustable gaps in the nanometer range can be realized independent of the mask or stamp pattern. Electrochemical characterizations using redox cycling in ferrocenemethanol (FcMeOH) demonstrate signal amplification factors of more than 110 together with collection factors higher than 99 %. Furthermore, the correlation between the gap width and the amplification factor was studied to obtain an electrochemical performance assessment of the nano gap electrodes. The results demonstrate an exponential relationship between amplification factor and gap width.
Al-Halhouli M, Kieninger J, Yurchenko O, Urban G
Mass transport and catalytic activity in hierarchical/non-hierarchical and internal/external nanostructures: A novel comparison using 3D simulation
2016 Appl Catal A-gen, Band: 517, Seiten: 12 - 20
KurzfassungThe distinct organization of nanostructured materials influences several catalytic characteristics, like selectivity, sensitivity or catalytic efficiency. This paper studies the effect of geometrical configuration of nanostructured catalyst on mass transport and catalytic activity based on 3D simulations of hierarchical external, hierarchical internal, non-hierarchical external and non-hierarchical internal nanostructures. Generally, external nanostructures revealed higher utilization of catalytic surface than the internal nanostructures. Among the four investigated nanostructures, the mass transport in hierarchical external nanostructures was found to be the best; they even showed kinetic controlled regime for the species with low diffusion coefficient. In contrast, hierarchical internal nanostructures showed slightly less specific activity than non-hierarchical internal nanostructures because of higher total diffusional resistance and longer diffusional path. As a result, although hierarchical nanostructures possess large surface area, only the hierarchical external nanostructures provided an outstanding accessibility of active sites. The obtained results provide the tool for understanding the catalytic efficiency in complex nanostructure and phenomena that are technically difficult to measure.
Pentyala V, Davydovskaya P, Ade M, Pohle R, Urban G
Metal–Organic Frameworks for Alcohol Gas Sensor
2016 Sensor Actuat B-chem, Band: 222, Seiten: 904 - 909
KurzfassungMetal–organic frameworks (MOFs) containing unsaturated coordination metal(II) sites (or open metal sites) have shown high selectivity for gas adsorption, separation and chemical sensor applications. The compound Zn3(btc)2·12H2O (Zn-btc), a coordination polymer with specific binding sites for guest molecules consist of Zn(II) ions and benzene tricarboxylic acid (btc) as anionic organic linkers, stabilized by numerous hydrogen bonds from crystal water molecules was synthesized. For the first time alcohol gas sensing interaction with Zn-btc framework was studied by using work function change methods. The as prepared Zn-btc thin layers show good response with reference to the alcohol concentration, chain length and a pronounced influence of humidity. The results are interpreted starting from the known crystal structure of Zn-btc. It is argued that the sensing mechanism is based on the exchange of Zn-coordinated water against alcohol molecules. The unfavourable loss of hydrogen bonds when replacing water against alcohol in the structure can be partially balanced by van der Waals interactions between alcohols alkyl chains and the aromatic rings of the btc linker molecules. These non-polar interactions should also be responsible for the work function change induced by alcohol adsorption in the framework.
Weltin A, Kieninger J, Urban G
Microfabricated, amperometric, enzyme-based biosensors for in vivo applications
2016 Anal Bioanal Chem, Band: 408, Seiten: 4503 - 4521
KurzfassungMiniaturized electrochemical in vivo biosensors allow the measurement of fast extracellular dynamics of neurotransmitter and energy metabolism directly in the tissue. Enzyme-based amperometric biosensing is characterized by high specificity and precision as well as high spatial and temporal resolution. Aside from glucose monitoring, many systems have been introduced mainly for application in the central nervous system in animal models. We compare the microsensor principle with other methods applied in biomedical research to show advantages and drawbacks. Electrochemical sensor systems are easily miniaturized and fabricated by microtechnology processes. We review different microfabrication approaches for in vivo sensor platforms, ranging from simple modified wires and fibres to fully microfabricated systems on silicon, ceramic or polymer substrates. The various immobilization methods for the enzyme such as chemical cross-linking and entrapment in polymer membranes are discussed. The resulting sensor performance is compared in detail. We also examine different concepts to reject interfering substances by additional membranes, aspects of instrumentation and biocompatibility. Practical considerations are elaborated, and conclusions for future developments are presented.

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Karthe D, Behrmann O, Blättel V, Elsässer D, Heese C, Hügle M, Hufert F, Kunze A, Niessner R, Ho J, Scharaw B, Spoo M, Tiehm A, Urban G, Vosseler S, Westerhoff T, Dame G, Seidel M
Modular development of an inline monitoring system for waterborne pathogens in raw and drinking water
2016 Environmental Earth Sciences, Band: 75, Seite: 1481
KurzfassungThe state-of-the-art monitoring of drinking water hygiene is based on the cultivation and enumeration of indicator bacteria. Despite its proven reliability, this approach has the disadvantages of being (a) relatively slow and (b) limited to a small number of indicator bacteria. Ideally, alternative methods would be less time-consuming while providing information about a larger set of hygienically relevant microorganisms including viruses. In this paper, we present insights into the design of a modular concentration and detection system for bacteria, bacteriophages and viruses. Following further validation, this or similar techniques have the potential to extend and speed up the monitoring of raw and drinking water hygiene in the future. The system consists of different modules for the concentration of microorganisms, an amplification and detection unit that includes a module for the differentiation between live and dead microorganisms, and an automated system for decision support and self-diagnosis. The ongoing testing under controlled laboratory conditions and real-life conditions in the water supply industry yields further system improvements. Moreover, the increased sensitivity and broader range of microbiological parameters emphasize the need for a reconsideration of the currently used criteria for the assessment of (drinking) water hygiene.
Kling A, Chatelle C, Armbrecht L, Qelibari E, Kieninger J, Dincer C, Weber W, Urban G
Multianalyte antibiotic detection on an electrochemical microfluidic platform
2016 Anal Chem, Band: 88, Nummer: 20, Seiten: 10036 - 10043
KurzfassungFast and easy-to-handle multi-analyte single-use sensors are of increasing interest for many fields such as medical analysis or environmental and food control. This report presents an electrochemical and universally applicable microfluidic platform enabling the simultaneous readout of up to eight enzyme-linked assays. For this purpose, microfluidic channel networks are designed each comprising distinct numbers of immobilization sections with a very low volume of 680 nl each. These immobilization sections can be actuated separately for an individual functionalization and assay procedure. To demonstrate the applicability of this platform in the context of surveillance and monitoring of different antibiotics, the simultaneous detection of the two commonly employed antibiotics tetracycline and pristinamycin is investigated. The limits of detection (LOD) are determined to 6.33 and 9.42 ng ml⁻¹ for tetracycline and pristinamycin, respectively, with inter-assay coefficients of variation (CV) below 10 %. The device provides a shelf-life of at least three months. The ability for multi-analyte measurements in a complex medium is demonstrated by the simultaneous detection of both antibiotics in spiked human plasma within a sample-to-result time of 15 minutes.

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Hajian A, Ghodsi J, Afraz A, Yurchenko O, Urban G
Nanomolar Detection of Methylparaben by a Cost-Effective Hemoglobin-Based Biosensor
2016 Mat Sci Eng C-mater, Band: 69, Seiten: 122 - 127
KurzfassungThis work describes the development of a new biosensor for methylparaben determination using electrocatalytic properties of hemoglobin in the presence of hydrogen peroxide. The voltammetric oxidation of methylparaben by the proposed biosensor in phosphate buffer (pH = 7.0), a physiological pH, was studied and it was confirmed that methylparaben undergoes a one electron-one proton reaction in a diffusion-controlled process. The biosensor was fabricated by carbon paste electrode modified with hemoglobin and multiwalled carbon nanotube. Based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for determination of methylparaben within a linear range from 0.1 to 13 μmol L⁻¹ and detection limit of 25 nmol L⁻¹. The developed biosensor possessed accurate and rapid response to methylparaben and showed good sensitivity, stability, and repeatability. Finally, the applicability of the proposed biosensor was verified by methylparaben evaluation in various real samples.
Al-Halhouli M, Kieninger J, Daubinger P, Yurchenko O, Urban G
Sensitivity and selectivity of porous electrodes in heterogeneous liquid-based catalytic reactions: 3D simulation study
2016 J Electrochem Soc, Band: 163, Nummer: 10, Seiten: E273 - E281
KurzfassungEfficiency, selectivity and sensitivity are important issues in catalytic applications, such as fuel cells and electrochemical sensors. This paper discusses the catalytic activity of porous layers in heterogeneous reactions based on the impact of pore morphology on pore accessibility in liquids. We present three-dimensional simulations to discuss some critical geometrical characteristics that influence the overall catalytic activity of porous catalyst. Sensitivity is proportional to the overall catalytic activity of the surface area. However, selectivity depends on pore accessibility. Simulation results demonstrate that at constant k⁰, porous layers with small pores and large numbers of pores are selective to the species with high diffusion coefficient because of high pore accessibility. In contrast, porous electrodes with low number of large pores and a large top surface area are selective to the species with low diffusion coefficient because of low pore accessibility. Additionally, pore accessibility influences the diffusional resistance, which has an impact on the local pH-value. High diffusional resistance in the porous layer leads to an accumulation of reaction products and a modification in the concentration of buffer molecules, which change local pH-value and therefore the catalytic behavior.
Zeniieh D, Rostas A M, Schleicher E, Ledernez L, Weber S, Urban G
The Effect of Low Pressure Plasma Polymerization Modes on the Properties of the Deposited Plasma Polymers
2016 Plasma Process Polym, Band: 13, Nummer: 7, Seiten: 744 - 751
KurzfassungThis work characterizes the properties of deposited plasma polymer that has been generated using three different low-pressure, low-temperature plasma modes: magnetron-enhanced audio frequency (15 kHz), magnetron-enhanced radio frequency (13.56 MHz), and radio frequency (13.56 MHz). A correlation between the applied plasma modes, the concentration of generated radicals in the deposited nanofilms, and the radical decay kinetics was found and is discussed. In addition, the role of the plasma driving frequency with respect to the properties of the films, in particular their density and their barrier properties, has been elucidated.

2015

nach oben zur Jahresübersicht

Qazzazie D, Beckert M, Mülhaupt R, Yurchenko O, Urban G
A Nitrogen-Doped Graphene Electrocatalyst for Selective Oxygen Reduction in Presence of Glucose and D-Gluconic Acid in pH-Neutral Media
2015 Electrochim Acta, Band: 186, Seiten: 579 - 590
Hakenberg S, Hügle M, Meyer P, Behrmann O, Dame G, Urban G
Fenton Fragmentation for Faster Electrophoretic on Chip Purification of Amplifiable Genomic DNA
2015 Biosens Bioelectron, Band: 67, Seiten: 49 - 52
KurzfassungWith a rapid and simple actuation protocol electrophoretic nucleic acid extraction is easy automatable, requires no moving parts, is easy to miniaturize and furthermore possesses a size dependent cut-off filter adjustable by the pore size of the hydrogel. However electrophoretic nucleic acid extraction from bacteria has so far been applied mainly for short RNA targets. One of the reasons is that electrophoretic processing of unfragmented genomic DNA strands is time-consuming, because of the length. Here DNA fragmentation would accelerate extraction and isolation. We introduce on-chip lysis and non-enzymatic DNA cleavage directly followed by a purifying step for receiving amplifiable DNA fragments from bacteria in less than 25 min. In contrast to restriction enzymes the Fenton reaction is known to cleave DNA without nucleotide specificity. The reaction mix contains iron(II) EDTA, sodium ascorbate, hydrogen peroxide and lysozyme. The degree of fragmentation can be adjusted by the concentration of reagents. The results enable electrophoretic extraction methods to unspecifically process long genomic DNA in a short time frame, e.g. for pathogen detection in a lab-on-a-chip format
Qazzazie D, Beckert M, Mülhaupt R, Yurchenko O, Urban G
Modified Nitrogen-Doped Graphene Electrocatalyst for Oxygen Reduction Reaction in Alkaline Fuel Cells
2015 Journal of Energy and Power Engineering, Band: 9, Seiten: 886 - 895
Dincer C, Ktaich R, Laubender E, Hees J J, Kieninger J, Nebel C E, Heinze J, Urban G
Nanocrystalline boron-doped diamond nanoelectrode arrays for ultrasensitive dopamine detection
2015 Electrochim Acta, Band: 185, Seiten: 101 - 106
KurzfassungIn this paper we present nanocrystalline boron-doped diamond nanoelectrode arrays (BDD-NEAs) for the low-level detection of biogenic substances such as dopamine (DA) without the need for a selective membrane. We achieved a sensitive and reproducible detection of dopamine in the presence of ascorbic acid (AA) with oxygen (O-) terminated BDD-NEAs. To improve the peak separation between dopamine and ascorbic acid, differential pulse voltammetry (DPV) was employed. Therewith, it was possible to measure dopamine with a sensitivity of 57.9 nA μM⁻¹ cm⁻². The detection limit was less than 100 nM with a linear behavior up to a concentration of 20 μM. The choice of the appropriate termination, the combination of the advantages of nanoelectrode arrays together with the outstanding electrochemical properties of boron-doped diamond and the right measurement method allowed successful measurement of dopamine in physiological concentrations in the presence of ascorbic acid.
Hajian A, Abbas Rafati A, Yurchenko O, Urban G, Afraz A, Najafi M, Bagheri A
Nanostructured Flower like Pt-Ru for Ethanol Oxidation and Determination
2015 J Electrochem Soc, Band: 162, Nummer: 1, Seiten: B41 - B46
Horak J, Dincer C, Qelibari E, Bakirci H, Urban G
Polymer-Modified Microfluidic Immunochip For Enhanced Electrochemical Detection of Troponin I
2015 Sensor Actuat B-chem, Band: 209, Seiten: 478 - 485
KurzfassungWe report enhanced electrochemical detection of a cardiac biomarker using a combination of a disposable microfluidic immunochip fabricated in Vacrel® 8100 photoresist film and a highly effective surface functionalization employing polyethylenimine (PEI). The use of the photoresist film enables fast prototyping and low-cost production without the need for a cleanroom. We use the surface carboxylates of the photoresist to biofunctionalize the microchannel on the chip using direct amine-specific coupling and modification via adsorbed and immobilized PEI in both linear (LPEI) and branched (BPEI) form. Characteristics of each immobilization strategy are assessed by a sandwich immunoassay for troponin I quantification in serum. The best assay performance is achieved using the immunochip modified with immobilized BPEI: the antigen was routinely detected at concentrations of 25 pg ml⁻¹ in 4 minute read-out time and 5 μl serum sample, representing an 18-fold improvement of the detection limit and 2.5-times faster read-out time in comparison to the assay implemented over amine-reactive esters without the PEI coating. We demonstrate that immobilized BPEI represents a stable and tunable scaffold that enhances biomolecule immobilization up to 60-times and stability two-fold while lowering non-specific binding by factor of three. This system provides a versatile and nonaggressive means for incorporation of biological material to virtually any platform design.
Armbrecht L, Dincer C, Kling A, Horak J, Kieninger J, Urban G
Self-assembled magnetic bead chains for sensitivity enhancement of microfluidic electrochemical biosensor platforms
2015 Lab Chip, Band: 15, Seiten: 4314 - 4321
KurzfassungIn this paper, we present a novel approach to enhance the sensitivity of microfluidic biosensor platforms with self-assembled magnetic bead chains. An adjustable, more than 5-fold sensitivity enhancement is achieved by introducing a magnetic field gradient along a microfluidic channel by means of a soft- magnetic lattice with a 350 μm spacing. The alternating magnetic field induces the self-assembly of the magnetic beads in chains or clusters and thus improves the perfusion and active contact between the analyte and the beads. The soft-magnetic lattices can be applied independent of the channel geometry or chip material to any microfluidic biosensing platform. At the same time, the bead-based approach achieves chip reusability and shortened measurement times. The bead chain properties and the maximum flow velocity for bead retention were validated by optical microscopy in a glass capillary. The magnetic actuation system was successfully validated with a biotin–streptavidin model assay on a low-cost electrochemical microfluidic chip, fabricated by dry-film photoresist technology (DFR). Labelling with glucose oxidase (GOx) per- mits rapid electrochemical detection of enzymatically produced hydrogen peroxide.

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Flamm H, Kieninger J, Weltin A, Urban G
Superoxide Microsensor Integrated into a Sensing Cell Culture Flask Microsystem Using Direct Oxidation for Cell Culture Application
2015 Biosens Bioelectron, Band: 65, Seiten: 354 - 359
KurzfassungA new electrochemical sensor system for reliable and continuous detection of superoxide radical release from cell culture was developed utilizing direct oxidation of superoxide on polymer covered gold microelectrodes. Direct superoxide oxidation was demonstrated to provide robust measurement principle for sensitive and selective reactive oxygen species (ROS) quantification without the need for biocomponent supported conversion. Sensor performance was investigated by using artificial enzymatic superoxide production revealing a sensitivity of 2235 A M⁻¹ m⁻². An electrode protection layer with molecular weight cut-off property from adsorbed linear branched polyethylenimine was successfully introduced for long term and selectivity improvement. Thin-film based sensor chip fabrication with implemented three-electrode setup and full integration into the technological platform Sensing Cell Culture Flask was described. Cell culturing directly on-chip and free radical release by phorbol-12-myristate-13-acetate (PMA) stimulation was demonstrated using T-47D human breast cancer carcinoma cell model. Transient extracellular superoxide production upon stimulation was successfully observed from amperometric monitoring. Signal inhibition from scavenging of extracellular superoxide by specific superoxide dismutase (SOD) showed the applicability for selective in vitro ROS determination. The results confirm the possibility of direct superoxide oxidation, with exclusion of the main interfering substances uric acid and hydrogen peroxide. This offers new insights into the development of reliable and robust ROS sensors.
Abushammala H, Pontes J F, Gomes G H, Osorio-Madrazo A, Thiré R M S M, Pereira F V, Laborie M-P G
Swelling, viscoelastic, and anatomical studies on ionic liquid-swollen Norway spruce as a screening tool toward ionosolv pulping
2015 Holzforschung, Band: 69, Seiten: 1059 - 1067
KurzfassungTo screen ionic liquid (IL) candidates for wood ionosolv pulping, swelling and viscoelastic studies on Norway spruce wood treated with ionic liquids have been conducted. In particular, the temperature dependency and kinetics of swelling in 1-butyl-3-methylimidazolium acesulfamate ([BMIM]Ace) and in 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc) were in focus. The kinetics of volumetric swelling in [BMIM]Ace yielded an Ea of 54 kJ.mol-1 compared to 23 kJ.mol-1 in [EMIM]OAc. The viscoelastic behavior of IL-swollen wood was studied by dynamic mechanical analysis, and the lowest in situ glass transition temperature (Tg) of lignin was ∼58 °C and ∼65 °C in [BMIM]Ace and in [EMIM]OAc, respectively. These Tg values are lower than that found in water. Higher Tg was calculated by the Gordon-Taylor equation, which means that swelling is not only due to the plasticizing effect of the ILs. SEM images showed that [EMIM]OAc has a stronger plasticizing effect than [BMIM]Ace. Overall, [EMIM]OAc is the most efficient agent for wood swelling, softening, and disintegration and, thus, it is the most promising candidate for ionosolv pulping.
Beigelbeck R, Cerimovic S, Reyes-Romero D, Kohl F, Voglhuber-Brunnmaier T, Jakoby B, Sauter T, Urban G
Thermal Properties of a Thin-Film Membrane Embedded in a Multiparameter Wind Sensor–On-Device Characterization Utilizing a Transient Measurement Approach
2015 Ieee Sens J, Band: PP, Nummer: 99
Gloecklhofer F, Lumpia D, Kohlstaedt M, Yurchenko O, Wuerfel U, Froehlich J
Towards Continuous Junction (CJ) Organic Electronic Devices: Fast and Clean Post-Polymerization Modification by Oxidation Using Dimethyldioxirane (DMDO)
2015 Reactive and Functional Polymers, Band: 86, Seiten: 16 - 26

2014

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Horak J, Dincer C, Bakirci H, Urban G
A Disposable Dry Film Photoresist-Based Microcapillary Immunosensor Chip for Rapid Detection of Epstein–Barr Virus Infection
2014 Sensor Actuat B-chem, Band: 191, Ergänzungsband: 820, Seiten: 813 - 820
KurzfassungAlthough there has been considerable progress in the development of engineering principles for miniaturized diagnostic devices, a substantial challenge remains to construct an integrated platform combining the advantages of low-cost production, easy handling and sensitive detection technique. We here report a new approach to disposable, polymeric bioanalytical microdevice: an immunosensor fabricated in Vacrel® 8100, a photoresist film that enables wafer-level production via simple lamination and photolithography in a non-cleanroom setting. The incorporated procedures of facile reagent delivery, fluid handling and amperometric detection using microfluidics allowed replicating the workflow of benchtop ELISA technique. The presence and accessibility of surface carboxyl groups enabled fast and versatile immobilization of biomolecules via amide crosslinking. We investigated the covalent bonding yield utilizing glucose oxidase and IR spectroscopy. To evaluate the platform, we show specific detection of an IgG-class antibody to Epstein–Barr virus (EBV) infection from a 5 μl human serum specimen with only a 2 min read-out time, which demonstrated 97.5 % agreement with results obtained from a reference microplate format. Our approach offers the opportunity for rapid and low-cost microfluidic assays that enables easy-to-use point-of-care biomarker detection in clinically relevant samples.
Cubukcu A, Reyes D, Urban G
A Dynamic Thermal Flow Sensor For Simultaneous Measurement of Thermal Conductivity and Flow Velocity of Gases
2014 Sensor Actuat A-phys, Band: 208, Seiten: 73 - 87
Weltin A, Slotwinski K, Kieninger J, Moser I, Jobst G, Wego M, Ehret R, Urban G
Cell Culture Monitoring for Drug Screening and Cancer Research: a Chip-Based, Transparent, Microfluidic, Multi-Sensor Microsystem
2014 Lab Chip, Band: 14, Nummer: 1, Seiten: 138 - 146
Reyes D, Behrmann O, Dame G, Urban G
Dynamic Thermal Sensor for Biofilm Monitoring
2014 Sensor Actuat A-phys, Band: 213, Seiten: 43 - 51
Daubinger P, Kieninger J, Unmüssig T, Urban G
Electrochemical Characteristics of Nanostructured Platinum Electrodes – A Cyclic Voltammetry Study
2014 Phys Chem Chem Phys, Band: 16, Nummer: 18, Seiten: 8392 - 8399
KurzfassungPlatinum surfaces play a decisive role in catalysis in sensors, fuel cells, solar cells and other applications like neuronal stimulation and recording. Technical advances in nanotechnology contributed tremendously to the progress in these fields. A fundamental understanding of the chemical and physical interactions between the nanostructured surfaces and electrolytes is essential, but was barely investigated up to now. In this article, we present a wet-chemical process for the deposition of nanostructures on polycrystalline platinum surfaces. The electrochemically active surface area was increased by a factor of over 1000 times with respect to the geometrical surface. The influence of the nanostructures was examined in different acidic, alkaline, and neutral electrolytes. Comparing cyclic voltammograms of nanostructured and planar polycrystalline platinum revealed new insights into the microenvironment at the electrode-electrolyte interface. The characteristic features of the cyclic voltammograms were altered in their shape and strongly shifted with respect to the applied potential. In neutral buffered and unbuffered electrolytes the water window was expanded from 1.4 V to more than 2 V. The shifts were interpreted as local pH-changes and exhausted buffer capacity in direct proximity of the electrode surface due to the strong release and binding of protons, respectively. These polarized electrodes induce significant changes in the electrochemical potential of the electrolyte due to the high roughness of their surface. The electrochemical phenomena and the observed voltage shifts are crucial for the understanding of the basic mechanism at nanostructured electrodes and mandatory for designing fuel cells, sensors and many other devices
Meyer P, Hakenberg S, Larbi S, Urban G, Dame G
Integrated Electrochemical Pumping and Dosing System Using Phaseguide Techniques with Inherent Implemented Valving and Metering
2014 Micro and Nanosystems, Band: 6, Nummer: 2, Seiten: 118 - 125

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Weltin A, Enderle B, Kieninger J, Urban G
Multiparametric, Flexible Microsensor Platform for Metabolic Monitoring In Vivo
2014 Ieee Sens J, Band: 14, Nummer: 10, Seiten: 3345 - 3351
KurzfassungIn this paper, we present a multiparametric microsensor platform for metabolic monitoring in vivo. In contrast to silicon or ceramic-based systems, the flexible, implantable polymer-based sensor strip is manufactured in a cost-effective hybrid of thin-film and laminate technology in a wafer-level process. Flexibility allows easy handling and placement in soft tissue. It comprises a microelectrode array for up to four electrochemical, amperometric micro-(bio)sensors, and an integrated reference electrode. The energy metabolism parameters glucose, lactate, and oxygen as well as the neurotransmitter glutamate were measured. The sensors allow dynamic, highly sensitive, localized, long-term, online measurement of up to four metabolic parameters with a single device. The reliable analytical performance of the sensors, stability of the reference electrode, and the multiparametric measurement are shown. The sensor can be inserted directly into the tissue for in vivo applications.
Partel S, Kasemann S, Choleva P, Dincer C, Kieninger J, Urban G
Novel fabrication process for sub-μm interdigitated electrode arrays for highly sensitive electrochemical detection
2014 Sensor Actuat B-chem, Band: 205, Seiten: 193 - 198
KurzfassungInterdigitated electrode arrays (IDAs) are often used for electrochemical detection using redox-cycling for signal amplification. Its geometry, especially the gap width, is an important factor defining its electrochemical performance (sensitivity and collection efficiency). Minimal defect density on a wafer is a must as a single shortcut prevents the function of the sensor chip. Therefore, the fabrication of interdigitated electrode arrays is a fundamental step in the integration of electrochemical sensors. This paper presents a novel fabrication approach that allows electrode spacing in the sub-micrometer region by using standard equipment such as UV Mask Aligner, physical vapor deposition and diffusion furnace. The fabrication procedure is a combination of dry etching, thermal oxidation and wet etching. This approach has potential to realize electrode distances down to 140 nm or even less. The proposed method enables the fabrication of sub-micron IDAs with the use of a conventional Mask Aligner and standard silicon technology. Moreover, it allows the electrode spacing adjustment without changing the mask design. The presented results demonstrate high sensitivity electrochemical sensors with amplification factors more than 12 without the need of e-beam lithography. Hence, this fabrication method offers a low-cost alternative to sub-micron e-beam written IDAs.
Zeniieh D, Ledernez L, Urban G
Parylene-C as High Performance Encapsulation Material for Implantable Sensors
2014 Procedia Engineering, Band: 87, Seiten: 1398 - 1401
Kieninger J, Aravindalochanan K, Sandvik J, Pettersen E, Urban G
Pericellular oxygen monitoring with integrated sensor chips for reproducible cell culture experiments
2014 Cell Proliferat, Band: 47, Nummer: 2, Seiten: 180 - 188
Weltin A, Kieninger J, Enderle B, Gellner AK, Fritsch B, Urban G
Polymer-Based, Flexible Glutamate and Lactate Microsensors for in vivo Applications
2014 Biosens Bioelectron, Band: 61, Seiten: 192 - 199
Horak J, Dincer C, Bakirci H, Urban G
Sensitive, Rapid and Quantitative Detection of Substance P in Serum Samples Using an Integrated Microfluidic Immunochip
2014 Biosens Bioelectron, Band: 58, Seiten: 186 - 192
KurzfassungMiniaturized diagnostic devices hold the promise of accelerate the specific and sensitive detection of various biomarkers, which can translate into many areas of medicine - from cheaper clinical trials, to early diagnosis and treatment of complex diseases. Therefore, we report on a disposable integrated chip-based capillary immunoassay featuring a microfluidic ELISA format combining electrochemical detection and low-cost fabrication employing a dry film photoresist, Vacrel® 8100. The readily accessible carboxylate groups on the material surface allow fast and high yield immobilization of biomolecules using amine-specific coupling via reactive esters requiring no laborious surface pretreatment. The integrated microfluidic system provides a convenient platform for a flow-through immunoassay. Capillary force is used for easy reagent delivery and loading the chip channel. We performed rapid quantification of serum level of substance P, a potential biomarker of acute neuroinflammation, using the developed microfluidic immunochip. Our miniaturized assay demonstrated a sensitive electrochemical detection of the antigen at 15.4 pg ml⁻¹ (11.5 pM) using only 5 µl of the biological fluid while cutting the total assay preparation time in half and the read-out time to 10 min. Combining microfluidics and fabrication suitable for mass production with the capability of testing clinically relevant samples creates conditions for the construction of low-cost and portable point of care diagnostic devices with minimal auxiliary electronics.
Pettersen E, Ebbesen P, Gieling R, Williams K, Dubois L, Lambin P, Ward C, Meehan J, Kunkler I, Langdon S, Ree A, Flatmark K, Lyng H, Calzada M, del Peso L, Landazuri M, Görlach A, Flamm H, Kieninger J, Urban G, Weltin A, Singleton D, Haider S, Buffa F, Harris A, Scozzafava A, Supuran C, Moser I, Jobst G, Busk M, Toustrup K, Overgaard J, Alsner J, Pouyssegur J, Chiche J, Mazure N, Marchiq I, Parks S, Ahmed A, Ashcroft M, Pastorekova S, Cao Y, Rouschop K, Wouters B, Koritzinsky M, Mujcic H, Cojocari D
Targeting Tumour Hypoxia to Prevent Cancer Metastasis. From Biology, Biosensing And Technology to Drug Development: the METOXIA Consortium
2014 J Enzym Inhib Med Ch, Band: 29, Nummer: 5, Seiten: 1 - 33
Davydovskaya P, Pentyala V, Hussein L, Yurchenko O, Pohle R, Urban G
Work Function Based Sensing of Alkanes and Alcohols with Benzene Tricaroxylate Linked Metal Organic Frameworks
2014 Sensor Actuat B-chem, Band: 193, Seiten: 911 - 917

2013

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Yin T-I, Yunpeng Z, Horak J, Bakirci H, Liao H-H, Tsai H-H, Juang Y-Z, Urban G
A Micro-cantilever Sensor Chip Based on Contact Angle Analysis for a Label-Free Troponin I Immunoassay
2013 Lab Chip, Band: 13, Nummer: 5, Seiten: 834 - 842
Nguyen A, Yin T, Reyes D, Urban G
A Microfluidic Chip with Integrated Electrical Cell-Impedance Sensing for Monitoring Single Cancer Cells Migration in 3D Matrices
2013 Anal Chem, Band: 85, Nummer: 22, Seiten: 11068 - 11076
Stevens G, Silver D, Zgaga-Griesz A, Bessler W, Vashist S, Patel P, Achazi K, Strotmeier J, Worbs S, Dorner M, Dorner B, Pauly D, Rummel A, Urban G, Krueger M
Bioluminescence Assay for the Highly Sensitive Detection of Botulinum Neurotoxin A Activity
2013 Analyst, Band: 138, Nummer: 20, Seiten: 6154 - 6162
KurzfassungThis article describes a novel bioluminescence assay for detecting proteolytic activity of Botulinum Neurotoxins (BoNT) in complex matrices. The assay is capable of detecting traces of BoNT in blood samples as well as in food drinks. The assay was responsive to BoNT/A subtypes 1 to 5, and serotype E3 in buffered solutions. It was responsive to filtered Clostridium botulinum supernatants and BoNT/A1 in complex with neurotoxin associated proteins in bouillon and milk (3.8% fat) down to 400 fM after 4 h RT incubation and in bouillon at concentrations down to 120 fM after 21 h RT incubation. In combination with an immunocapture/enrichment step it could detect BoNT/A1 in citrated plasma at concentrations down to 30 fM (1.2 mouse LD50/mL). The simplicity of the assay, combined with a demonstrated ability to lyophilize the reagents, demonstrates its usefulness for detection of BoNT in non-specialised analytical laboratories.
Vulto P, Kuhn P, Urban G
Bubble-Free Electrode Actuation for Micro-Preparative Scale Electrophoresis of RNA
2013 Lab Chip, Band: 13, Seiten: 2931 - 2936
Kiefer R, Weis D G, Aabloo A, Urban G, Heinze J
Dependence of Polypyrrole Bilayer Deflection Upon Polymerization Potential
2013 Synthetic Met, Band: 172, Seiten: 37 - 43
Zeniieh D, Bajwa A, Ledernez L, Urban G
Effect of Plasma Treatments and Plasma-Polymerized Films on the Adhesion of Parylene-C to Substrates
2013 Plasma Process Polym, Band: 10, Nummer: 12, Seiten: 1081 - 1089
Reyes D, Cubukcu A, Urban G
Measurement and Simulation of the Frequency Response of a Thermal Flow Sensor at Different Flow Speeds
2013 Sensor Actuat A-phys, Band: 189, Seiten: 168 - 176
Bergmann M, Ledernez L, Dame G, Lickert S, Widmer F, Gier Y, Urban G
Nanofilms Produced by Magnetron Enhanced Plasma Polymerization from Methane and Oxygen for Coating of Rigid Contact Lenses
2013 Plasma Process Polym, Band: 10, Nummer: 11, Seiten: 970 - 977
Meskath S, Urban G, Heinze J
Nanophase Separated Amphiphilic Polymer Co-Networks as Efficient Matrices for Optical Sensors: Rapid and Sensitive Detection of NO2
2013 Sensor Actuat B-chem, Band: 186, Seiten: 367 - 373
Bunte C, Hussein L, Urban G
Performance of Non-Compartmentalized Enzymatic Biofuel Cell Based on Buckypaper Cathode and Ferrocene-Containing Redox Polymer Anode
2013 J Power Sources, Band: 247, Seiten: 579 - 586
Partel S, Urban G, Motzek K
Simulation Model Validation of Two Common i-Line Photoresists
2013 Microelectron Eng, Band: 1, Seiten: 1 - 5
KurzfassungIn this paper we analyze the dissolution behavior of two common i-line resists (MEGAPOSIT SPR 955-CM and AZ MiR 701) and validate the experimental findings by generating simulation models and implementing them in simulation software. It is demonstrated that with the data provided by a Dissolution Rate Monitor (DRM) the quality of lithography simulation results can improve and can speed up process development and optimization. Different process conditions were investigated to evaluate the area of validity of the simulation model. Lithography simulation software packages LayoutLAB and Dr. LiTHO were used to verify the resist models
Reyes D, Kogan K, Cubukcu A, Urban G
Simultaneous Flow And Thermal Conductivity Measurement of Gases Utilizing a Calorimetric Flow Sensor
2013 Sensor Actuat A-phys, Band: 203, Seiten: 225 - 233
Bergmann M, Zeniieh D, Ledernez L, Dame G, Urban G
Swelling and Water Uptake Behavior of Nanofilms Obtained by a Magnetron Enhanced Plasma-Polymerization Process
2013 Plasma Process Polym, Band: 10, Nummer: 10, Seiten: 904 - 911

2012

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Hakenberg S, Hügle M, Weidmann M, Hufert F, Dame G, Urban G
A Phaseguided Passive Batch Microfluidic Mixing Chamber for Isothermal Amplification
2012 Lab Chip, Band: 12, Nummer: 21, Seiten: 4576 - 4580
Yasuda H, Ledernez L, Olcaytug F, Dame G, Bergmann M
Biocompatible Nanofilm Coating by Magneto-Luminous Polymerization of Methane
2012 Prog Org Coat, Band: 74, Nummer: 4, Seiten: 667 - 678
Darbandi M, Urban G, Krueger M
Bright Luminescent, Colloidal Stable Silica Coated CdSe/ZnS Nanocomposite by an In Situ, One-Pot Surface Functionalization
2012 J Colloid Interf Sci, Band: 365, Nummer: 1, Seiten: 41 - 45
Podszun S, Vulto P, Heinz H, Hakenberg s, Hermann C, Hankemeier T, Urban G
Enrichment of Viable Bacteria in a Micro-Volume by Free-Flow Electrophoresis
2012 Lab Chip, Band: 12, Nummer: 3, Seiten: 451 - 457
Partel S, Mayer M, Hudek P, Dincer C, Kieninger J, Urban G, Motzek K, Matay L
Fabrication Process Development for a High Sensitive Electrochemical IDA Sensor
2012 Microelectron Eng, Band: 97, Seiten: 235 - 240
KurzfassungWe present recent results on a development and fabrication process of the electrochemical sensor with high sensitivity. The electrochemical sensor is based on an enzyme-linked immunosorbent assay (ELISA). The used ELISA provides a redox active species as intermediate product for the electrochemical detection. The increase in sensitivity due to the redox cycling process was evaluated with an interdigitated electrode array (IDA) consisting of 300 fingers with 2 μm width and 1 μm gap each. The lithography process was simulated to estimate the impact of the sensor stack and the illumination source during the lithography step on the sensor’s critical features. Development characteristics of the photoresist were precisely determined using a multi-wavelength dissolution rate monitor (DRM). The final sensor was tested with the ferri/ferro cyanide couple as well as with para-aminophenol (PAP). Both results prove amplification factors of more than 10 measured in a flow cell. The results presented demonstrate that high sensitivity electrochemical immunosensors based on redox cycling at IDAs on Pyrex substrate can be fabricated with conventional but highly optimized UV lithography.
Yuan Y, Riehle F, Nitschke R, Krueger M
Highly Photoluminescent and Photostable CdSe Quantum Dot-Nylon Hybrid Composites for Efficient Light Conversion Applications
2012 Mater Sci Eng B-adv, Band: 177, Seiten: 245 - 250
Ledernez L, Olcaytug F, Urban G
Inter-Electrode Distance and Breakdown Voltage in Low-Pressure Argon Discharges
2012 Contrib Plasm Phys, Band: 52, Nummer: 4, Seiten: 276 - 282
Weinmann M, Nisch W, Stett A, Bucher V, Urban G
Langzeitstabile Verkapselungsschichten mit integriertem Feuchtesensor für aktive Mikroimplantate
2012 WOMag, Band: 12
KurzfassungFür die Therapie- und Diagnoseverfahren neuronaler Erkrankungen werden vermehrt elektrisch aktive Implantate entwickelt und klinisch getestet, wie beispielsweise Netzhautimplantate zur Wiederherstellung von Sehvermögen und Hirnimplantate zur invasi- ven Epilepsiediagnostik. Aufgrund der für diese Anwendungen erforderlichen Miniaturisierung und mechanisch flexiblen Bauformen müssen flexible und diffusionsdichte Verkapselungsschichtsysteme entwickelt werden, die ein Eindringen von Körperflüssigkeit an DC-spannungsführenden Elektronikkomponenten und damit den Ausfall der Mikroimplantate durch Korrosion verhindern. Das NMI hat in Zusammenarbeit mit IMTEK ein Verfahren entwickelt, welches durch eine geeignete Wahl und Kombination von biokompatiblen Polymeren (Polyimid, Parylen) und anorganischen Wasserdampfbarriereschichten die Herstellung einer flexiblen und langzeitstabi- len Verkapselungsschicht erlaubt. Mit Hilfe von flexiblen Dünnschichtfeuchtesensoren kann die Dichtigkeit der Verkapselungsschich- ten kostengünstig bestimmt werden. Die Feuchtesensoren sollen später zur Überwachung der Implantatfunktion in reale Implantate integriert werden.
Yin T-I, Nguyen T A
Molecules Sensing Layer Design of Piezoresistive Cantilever Sensor for Higher Surface Stress Sensitivity
2012 Vietnam Journal of Mechanics, Band: 34, Nummer: 4, Seiten: 311 - 320
KurzfassungThis paper reports on molecular sensing layer design of a piezoresistive cantilever sensor for higher surface stress sensitivity. The proposed analyses show that the previous understanding of piezoresistive cantilevers for surface stress measurement requires reconsideration for a cantilever utilizing polycrystalline silicon as a piezoresistor. The integration of the molecular sensing layer stripe pattern design to the cantilever effectively improves the piezoresistive output and utilizes the full sensing area of the cantilever surface. The proposed sensing layer design can be effectively integrated to current piezoresistive cantilever sensors to improve sensor performance in biochemical assays.
Ledernez L, Olcaytug F, Urban G
Paschen Curve and Film Growth in Low Pressure Capacitively Coupled Magnetron Plasma Polymerization
2012 Contrib Plasm Phys, Band: 52, Nummer: 4, Seiten: 283 - 288
Celik D, Krueger M, Veith C, Schleiermacher H, Zimmermann B, Allard S, Dumsch I, Scherf U, Rauscher F, Niyamakom P
Performance Enhancement of CdSe Nanorod-PCPDTBT Based Hybrid Solar Cells Utilizing a Novel Combination of Postsynthetic Nanoparticle Surface Treatments
2012 Sol Energ Mat Sol C, Band: 98, Seiten: 433 - 440
Rubenwolf S, Sane S, Hussein L, Kestel J, von Stetten F, Urban G, Krueger M, Zengerle R, Kerzenmacher S
Prolongation of Electrode Lifetime in Biofuel Cells by Periodic Enzyme Renewal
2012 Appl Microbiol Biot, Band: 96, Nummer: 3, Seiten: 841 - 849
Dincer C, Laubender E, Hees J, Nebel C, Urban G, Heinze J
SECM Detection of Single Boron Doped Diamond Nanodes and Nanoelectrode Arrays Using Phase-Operated Shear Force Technique
2012 Electrochem Commun, Band: 24, Seiten: 123 - 127
KurzfassungBoron doped diamond (BDD) is a promising electrode material for electrochemical biosensor applications due to its low bio-fouling, chemical stability, and large potential window. For the first time, BDD nanoelectrode arrays (NEA) were studied using Scanning Electrochemical Microscopy (SECM) measurements. Using the phase-operated shear force technique and feedback mode, it was possible to scan a platinum (Pt) nanode with an active radius of 167 nm over a diamond array at a constant distance of 45 nm and to detect the electrochemical activity of single BDD nanodes in the 100 nm range.

2011

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Hussein L, Rubenwolf F, von Stetten F, Urban G, Zengerle R, Krueger M, Kerzenmacher S
A Highly Efficient Buckypaper-Based Electrode Material for Mediatorless Laccase-Catalyzed Dioxygen Reduction
2011 Biosens Bioelectron, Band: 26, Seiten: 4133 - 4138
KurzfassungThe redox enzyme laccase from Trametes versicolor efficiently catalyzes the oxygen reduction reaction (ORR) in mediatorless biofuel cell cathodes when adsorbed onto multi-walled carbon nanotubes (MWCNTs). In this work we demonstrate that the fabrication of MWCNTs in form of buckypaper (BP) results in an excellent electrode material for laccase-catalyzed cathodes. BPs are mechanically stable, self-entangling mats with high dispersion of MWCNTs resulting in easy to handle homogeneous layers with highly mesoporous structures and excellent electrical conductivities. All biocathodes have been electrochemically investigated in oxygen-saturated buffer at pH 5 by galvanostatic polarization and potentiodynamic linear sweep voltammetry. Both methods confirm an efficient direct interaction of laccase with BP with a high open circuit potential of 0.882 V vs. normal hydrogen electrode (NHE). The high oxygen reduction performance leads to high current densities of 422 ± 71 μA cm−2 at a typical cathode potential of 0.744 V vs. NHE. When the current density is normalized to the mass of the electrode material (mass activity), the BP-based film electrodes exhibit a 68-fold higher current density at 0.744 V vs. NHE than electrodes fabricated from the same MWCNTs in a non-dispersed agglomerated form as packed electrodes. This clearly shows that MWCNTs can act more efficiently as cathode when prepared in form of BP. This can be attributed to reduced diffusional mass transfer limitations and enhanced electrical conductivity. BP is thus a very promising material for the construction of mediatorless laccase cathodes for ORR in biofuel cells. In addition we demonstrated that these electrodes exhibit a high tolerance towards glucose, the most common bioanode fuel.
Meskath S, Urban G, Heinze J
A New Optochemical Chlorine Gas Sensor Based on the Application of Amphilic Co-Networks as Matrices
2011 Sensor Actuat B-chem, Band: 151, Nummer: 2, Seiten: 327 - 332
Schaedel M, Jeltsch K, Zhou Y, Krueger M, Meerholz K
Determination of Volume Fractions and Ligand Layer Thickness of Polymer/CdSe Quantum Dot Blend Films by Effective Medium Approximations
2011 J Polym Sci Pol Phys, Band: 50, Seiten: 75 - 82
Zhou Y, Eck M, Veit C, Zimmermann B, Rauscher F, Niyamakom P, Yilmaz S, Dumsch I, Allard S, Scherf U, Krueger M
Efficiency Enhancement for Bulk-Heterojunction Hybrid Solar Cells Based on Acid Treated CdSe Quantum Dots and Low Bandgap Polymer PCPDTBT
2011 Sol Energ Mat Sol C, Band: 95, Nummer: 4, Seiten: 1232 - 1237
KurzfassungWe report on the efficiency enhancement for bulk-heterojunction hybrid solar cells based on hexanoic acid treated trioctylphosphine/oleic acid-capped CdSe quantum dots (QDs) and low bandgap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b0]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) compared to devices based on poly(3-hexylthiophene) (P3HT). Photovoltaic devices with optimized polymer:QD weight ratio, photoactive film thickness, thermal annealing treatment, and cathode materials exhibited a power conversion efficiency of 2.7% after spectral mismatch correction, which is the highest reported value for spherical CdSe QD based photovoltaic devices. The efficiency enhancement is attributed to the surface treatment of the QDs together with the use of the low bandgap polymer PCPDTBT leading to an increased short-circuit current density due to additional light absorption between 650 and 850 nm. Our results suggest that the hexanoic acid treatment is generally applicable to various ligand-capped CdSe and confirm that low bandgap polymers with adequate HOMO and LUMO levels are promising to be incorporated into hybrid solar cells for further device performance improvement.
Zhou Y, Eck M, Men C, Rauscher F, Niyamakom P, Yilmaz S, Dumsch I, Allard S, Scherf U, Krueger M
Efficient Polymer Nanocrystal Hybrid Solar Cells by Improved Nanocrystal Composition
2011 Sol Energ Mat Sol C, Band: 95, Nummer: 12, Seiten: 3227 - 3232
KurzfassungWe demonstrate the importance of the nanocrystal surface treatment and the inorganic composition for hybrid solar cells. Mixtures of CdSe nanorods and CdSe quantum dots integrated in hybrid solar cells together with the conjugated polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) perform better than nanorod and quantum dot only based devices. In addition larger sized quantum dots show a similar improvement after integration in respective solar cells. Power conversion efficiency values exceeding 3% are observed. A first result on the shelf lifetime of such a device is highlighted.
Hussein L, Urban G, Krueger M
Fabrication and Characterization of Buckypaper-Based Nanostructured Electrodes as a Novel Material for Biofuel Cell Applications
2011 Phys Chem Chem Phys, Band: 13, Seiten: 5831 - 5839
KurzfassungThe fabrication process of buckypapers (BPs) made from stable suspensions of as-received or functionalized multi-walled carbon nanotubes (MWCNTs) with high purity (97.5 wt%, Baytubes), their characterization and their utilization towards novel biofuel cell electrode applications are reported. The BPs can vary in thickness between 1 μm and 200 μm, are mechanically robust, flexible, stable in solvents, possess high meso-porosities as well as high apparent electrical conductivities of up to 2500 S m−1. Potentiodynamic measurements of biocathodes based on bilirubin oxidase (BOD)-decorated BPs for the oxygen reduction reaction (ORR) in neutral media (phosphate buffer solution) containing glucose indicate that BP electrodes based on functionalized MWCNTs (fBPs) perform better than BP electrodes of as-received MWCNTs and have high potential as an effective electrode material in biofuel cells and biosensors.
Hussein L, Feng Y, Alonso-Vante N, Urban G, Krueger M
Functionalized-Carbon Nanotube Supported Electrocatalysts and Buckypaper-Based Biocathodes for Glucose Fuel Cell Applications
2011 Electrochim Acta, Band: 56, Nummer: 22, Seiten: 7659 - 7665
KurzfassungThe preparation and testing for electrocatalytic activity of functionalized carbon nanotube (f-CNT) supported Pt and Au–Pt nanoparticles (NPs), and bilirubin oxidase (BOD), are reported. These materials were utilized as oxygen reduction reaction (ORR) cathode electrocatalysts in a phosphate buffer solution (0.2 M, pH 7.4) at 25 °C, in the absence and presence of glucose. Carbon monoxide (CO) stripping voltammetry was applied to determine the electrochemically active surface area (ESA). The ORR performance of the Pt/f-CNTs catalyst was high (specific activity of 80.9 μA cmPt−2 at 0.8 V vs. RHE) with an open circuit potential within ca. 10 mV of that delivered by state-of-the-art carbon supported platinum catalyst and exhibited better glucose tolerance. The f-CNT support favors a higher electrocatalytic activity of BOD for the ORR than a commercially available carbon black (Vulcan XC-72R). These results demonstrate that f-CNTs are a promising electrocatalyst supporting substrate for biofuel cell applications.
Stevens G, Krueger M, Latychevskaia T, Lindner P, Plueckthun A, Fink H
Individual Filamentous Phage Imaged by Electron Holography
2011 Eur Biophys J Biophy, Band: 40, Seiten: 1197 - 1201
Puchberger-Enengl D, Podszun S, Heinz H, Hermann C, Vulto P, Urban G
Microfluidic Concentration of Bacteria by On-Chip Electrophoresis
2011 Biomicrofluidics, Band: 5, Nummer: 4, Seiten: 044111 - 044121
Aravindalochanan K, Kieninger J, Flamm H, Urban G
P7. An Approach to Distinguish and Monitor NO from NO2-/NO3- Levels in Pericellular Region
2011 Nitric Oxide-biol Ch, Band: 24, Ergänzungsband: May, Seiten: 18 - 19
Vulto P, Podszun S, Meyer P, Hermann C, Manz A, Urban G
Phaseguides: a Paradigm Shift in Microfluidic Priming and Emptying
2011 Lab Chip, Band: 11, Nummer: 9, Seiten: 1596 - 1602
Albero J, Zhou Y, Eck M, Rauscher F, Niyamakom P, Dumsch I, Allard S, Scherf U, Krueger M, Palomares E
Photo-Induced Charge Recombination Kinetics in Low Bandgap PCPDTBT Polymer:CdSe Quantum Dot Bulk Heterojunction Solar Cells
2011 Chem. Sci., Band: 2, Nummer: 12, Seiten: 2396 - 2401
Yin T, Zhao Y, Lin C, Tsai H, Juang Y, Yang S, Urban G
The Application of Capillary Force to a Cantilever as a Sensor for Molecular Recognition
2011 Appl Phys Lett, Band: 98, Seiten: 104102 - 104104

2010

nach oben zur Jahresübersicht

Cubukcu A, Zernickel E, Buerklin U, Urban G
A 2D Thermal Flow Sensor with Sub-mW Power Consumption
2010 Sensor Actuat A-phys, Band: 163, Nummer: 2, Seiten: 449 - 456
Darbandi M, Urban G, Krueger M
A Facile Synthesis Method to Silica Coated CdSe/ZnS Nanocomposites with Tunable Size and Optical Properties
2010 J Colloid Interf Sci, Band: 351, Seiten: 30 - 34
Vulto P, Dame G, Maier U, Makohliso S, Podszun S, Zahn P, Urban G
A Microfluidic Approach for High Efficiency Extraction of Low Molecular Weight RNA
2010 Lab Chip, Band: 10, Nummer: 5, Seiten: 610 - 616
Gueder F, Yang Y, Krueger M, Stevens G, Zacharias M
Atomic Layer Deposition on Phase-Shift Lithography Generated Photoresist Pattern for 1D Nanochannel Fabrication
2010 Acs Appl Mater Inter, Band: 2, Nummer: 12, Seiten: 3473 - 3478
Yuan Y, Riehle F, Urban G, Thomann R, Haoshuang G, Krueger M
Critical Parameters for the Scale-Up synthesis of CdSe Quantum Dots
2010 J Nanosci Nanotechno, Band: 10, Nummer: 9, Seiten: 6041 - 6045
Zhou Y, Riehle F, Yuan Y, Schleiermacher H, Niggemann M, Urban G, Krueger M
Improved Efficiency of Hybrid Solar Cells Based on Non Ligand-Exchanged CdSe Quantum Dots and Poly(3-Hexylthiophene)
2010 Appl Phys Lett, Band: 96, Nummer: 1, Seiten: 013304 - 013306
Zhou Y, Riehle F, Yuan Y, Schleiermacher H F, Niggemann M, Urban G, Krueger M
Improved Efficiency of Hybrid Solar Cells Based on Non-Ligand-Exchanged CdSe Quantum Dots and Poly(3-Hexylthiophene)
2010 Appl Phys Lett, Band: 96, Nummer: 1
Redel E, Walter M, Thomann R, Hussein L, Krueger M, Janiak C
Stop-and-Go, Stepwise and "Ligand-Free" Nucleation, Nanocrystal Growth and Formation of Au-NPs in Ionic Liquids (ILs)
2010 Chem Commun, Band: 46, Seiten: 1159 - 1161
Lin C, Yin T, Lin Y, Huang C, Lin T, Chen T, Lin J, Wu H, Chang H
Study on Mechanical Properties of Thrombomodulin Transfected Cancer Cell by Atomic Force Microscopy
2010 J Med Biol Eng, Band: 30, Nummer: 5, Seiten: 313 - 320

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2009

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Vulto P, Huesgen T, Albrecht B, Urban G
A Full-Wafer Fabrication Process for Glass Microfluidic Chips with Integrated Electroplated Electrodes by Direct Bonding of Dry Film Resist
2009 J Micromech Microeng, Band: 19, Nummer: 7, Seite: 077001
Gonska J, Schelling C, Urban G
Application of Hydrogel-Coated Microcantilevers as Sensing Elements for pH
2009 J Micromech Microeng, Band: 19, Nummer: 12, Seite: 127002
Riehle F, Bienert R, Thomann R, Urban G, Krueger M
Blue Luminescence and Superstructures from Magic Size Clusters of CdSe
2009 Nano Lett, Band: 9, Nummer: 2, Seiten: 514 - 518
Redel E, Walter M, Thomann R, Vollmer C, Hussein L, Scherer H, Krueger M, Janiak C
Synthesis, Stabilization, Functionalization and, DFT Calculations of Gold Nanoparticles in Fluorous Phases (PTFE and Ionic Liquids)
2009 Chem-eur J, Band: 15, Nummer: 39, Seiten: 10047 - 10059
Ebbesen P, Pettersen E, Gorr T, Jobst G, Williams, Kieninger J, Wenger R, Pastorekova S, Dubois L, Lambin P, Wouters B, Van Den Beucken T, Supuran C, Poellinger L, Ratcliffe P, Kanopka A, Goerlach A, Gasmann M, Harris A, Maxwell P, Scozzafava A
Taking Advantage of Tumor Cell Adaptations to Hypoxia for Developing New Tumor Markers and Treatment Strategies
2009 J Enzym Inhib Med Ch, Band: 24, Nummer: s1, Seiten: 1 - 39

2008

nach oben zur Jahresübersicht

Ehlert O, Thomann R, Darbandi M, Nann T
A Four-Color Colloidal Multiplexing Nanoparticle System
2008 Acs Nano, Band: 2, Nummer: 1, Seiten: 120 - 124
Yang S, Chang C, Yin T, Kuo P
DNA Hybridization Measurement by Self-Sensing Piezoresistive Microcantilevers in CMOS Biosensor
2008 Sensor Actuat B-chem, Band: 174, Nummer: 2, Seiten: 674 - 681
Kucur E, Buecking W, Nann T
Electrochemical Determination of Mesoscopic Phenomena and Defect States in CdSe Nanocrystals and Charge Carrier Manipulability
2008 Microchim Acta, Band: 160, Nummer: 2, Seiten: 299 - 308
Yasuda H, Ledernez L, Olcaytug F, Urban G
Electron Dynamics of Low-Pressure Deposition Plasma
2008 Pure Appl Chem, Band: 80, Nummer: 9, Seiten: 1883 - 1892
KurzfassungWhen the electric field in the dark gas phase reaches the threshold value, an electron avalanche (breakdown) occurs, which causes dissociation of organic molecules, excitation of chemically reactive molecular gas, and/or ionization of atomic gas, depending on the type of gas involved. The principles that govern these electron-impact reactions are collectively described by the term “electron dynamics”. The electron-impact dissociation of organic molecules is the key factor for the deposition plasma. The implications of the interfacial avalanche of the primary electrons on the deposition plasma and also other plasma processes are discussed. The system dependency of low-pressure plasma deposition processes is an extremely important factor that should be reckoned, because the electron dynamic reactions are highly dependent on every aspect of the reaction system. The secondary electron emission from the cathode is a misinterpretation of the interfacial electron avalanche of the primary electrons described in this paper.
Stoehr U, Vulto P, Hoppe P, Urban G, Reinecke H
High-Resolution Permanent Photoresist Laminate for Microsystem Applications
2008 J Micro-nanolith Mem, Band: 7, Nummer: 3, Seite: 033009
Yasuda H
Magnetron-AF Plasma Polymerization
2008 Plasma Process Polym, Band: 5, Nummer: 3, Seiten: 215 - 227
Urban G
Micro- and Nanobiosensors - State of the Art and Trends
2008 Meas Sci Technol, Band: 20, Nummer: 1, Seite: 012001
Yang S, Chang C, Yin T
On the Temperature Compensation of Parallel Piezoresistive Microcantilevers in CMOS Biosensor
2008 Sensor Actuat B-chem, Band: 129, Nummer: 2, Seiten: 678 - 684
Ehlert O, Buecking W, Riegler J, Merkulov A, Nann T
Organometallic Synthesis and Electrophoretic Characterization of High-Quality ZnS:Mn/ZnS Core/Shell Nanoparticles for Bioanalytical Applications
2008 Microchim Acta, Band: 160, Nummer: 3, Seiten: 351 - 356
Ledernez L, Olcaytug F, Yasuda H, Urban G
Ultraviolet Light in Glow Discharges
2008 J Phys D Appl Phys, Band: 104, Nummer: 10, Seiten: 103303 - 103304

2007

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Yasuda H
An Overview of Magnetron Plasma Polymerization for the Most Successful Industrial Scale Operation of Plasma Polymerization
2007 Journal of the Vacuum Society of Japan, Band: 50, Nummer: 10, Seiten: 598 - 600
Czekai S, Nolting F, Heydermann L, Kunze K, Krueger M
Antiferromagnetic Domain Configurations in Patterned LaFeO3 Thin Films
2007 J Phys-condens Mat, Band: 19, Nummer: 38, Seiten: 6214 - 6218
Cavaliere-Jaricot S, Darbandi M, Nann T
Au-Silica Nanoparticles by "Reverse" Synthesis of Cores in Hollow Silica Shells
2007 Chem Commun, Nummer: 20, Seiten: 2031 - 2033
Yang S, Yin T
Design and Analysis of Piezoresistive Microcantilever for Surface Stress Measurement in Biochemical
2007 Sensor Actuat B-chem, Band: 120, Nummer: 2, Seiten: 736 - 744
Yang S, Yin T, Chang C
Development of a CMOS Biosensor Chip for Surface Stress Measurement in Bioanalyte
2007 Sensor Actuat B-chem, Band: 123, Nummer: 2, Seiten: 707 - 714
Yang S, Yin T, Chang C
Development of a Double-Microcantilever Design for Surface Stress Measurement in Microsensors
2007 Sensor Actuat B-chem, Band: 121, Nummer: 2, Seiten: 545 - 551
Eggenberger K, Merkulov A, Darbandi M, Nann T, Nick P
Direct Immunofluorescence of Plant Microtubules Based on Semiconductor Nanocrystals
2007 Bioconjugate Chem, Band: 18, Nummer: 6, Seiten: 1879 - 1886
Kiefer R, Weiss D, Travas-Sejdic J, Urban GA, Heinze J
Effect of Electrochemial Synthesis Conditions on Deflection PEDOT bilayers
2007 Sensor Actuat B-chem, Band: 123, Nummer: 1, Seiten: 379 - 383
Yasuda H
Electrical Breakdown of Argon and Trimethylsilane in Low-Pressure DC Discharges: The Surface-States Equilibration Principle
2007 Plasma Process Polym, Band: 4, Nummer: 4, Seiten: 347 - 359
Jobst G, Moser I, Urban G
Glukose Öffnet den Markt
2007 Chemische Rundschau, Band: Nr. 4, Seiten: 56 - 57
Buecking W, Riegler J, Rettenmaier C, Nann T
Isotachophoretic Measurement of Luminescent Semiconductor Nanocrystals
2007 Int J Nanotechnol, Band: 4, Nummer: 3, Seiten: 298 - 308
KurzfassungLuminescent semiconductor nanocrystals were derivatised by mercaptocarboxylic acids. A direct synthesis in the solution of the ligand and a post-synthesis ligand exchange method was used. The two methods were compared and evaluated by isotachophoresis. The electrophoretic mobility, as well as the colloidal stability and the coverage with the ligand, were determined. An alternative method for concentration estimation of nanocrystals by isotachophoresis was introduced.
Buecking W, Ehlert O, Riegler J, Rettenmaier C, Merkoulov A, Nann T
Isotachophoretic Measurements of Luminescent Semiconductor Nanocrystals
2007 Biophys. Rev. Lett., Band: 2, Nummer: 1, Seiten: 99 - 108
KurzfassungLuminescent semiconductor nanocrystals of CdTe and CdSe were derivatised by mercaptocarboxylic acids. A direct synthesis in the solution of the ligand and a post-synthesis ligand exchange method was used. The two methods were compared and evaluated by isotachophoresis. The electrophoretic mobility as well as the colloidal stability and the coverage with the ligand, were determined. An alternative method for the concentration estimation of nanocrystals by means of isotachophoresis was introduced.
Ledernez L, Olcaytug F, Urban G, Yasuda S
Magnetically Enhanced 15 kHz Glow Discharge of Methane
2007 Plasma Chem Plasma P, Band: 27, Nummer: 6, Seiten: 659 - 667
Szymanowski H, Sobczyk-Guzenda A, Rylski A, Jakubowski W, Gazicki-Lipman M, Herberth U, Olcaytug F
Photo-Induced Properties of Thin Ti02 Films Deposited Using the Radio Frequency Plasma Enhanced Chemical Vapor Deposition Method
2007 Thin Solid Films, Band: 515, Nummer: 13, Seiten: 5275 - 5281
Ledernez L, Yasuda H, Olcaytug F, Gemetz F, Urban G
Pressure Dependence of Plasma Polymerization of Methane at Constant W/FM
2007 Plasma Process Polym, Band: 4, Nummer: s1, Seiten: 794 - 796
Kucur E, Boldt F, Cavaliere-Jaricot S, Ziegler J, Nann T
Quantitative Analysis of Cadmium Selenide Nanocrystal Concentration by Comparative Techniques
2007 Anal Chem, Band: 79, Nummer: 23, Seiten: 8987 - 8993

2006

nach oben zur Jahresübersicht

Spiller E, Schoell A, Alexy R, Kuemmerer K, Urban G
A Microsystem for Growth Inhibition Test of Enterococcus Faecalis Based on Impedance Measurement
2006 Sensor Actuat B-chem, Band: 118, Nummer: 1-2, Seiten: 182 - 191
Spiller E, Schoell A, Alexy R, Kuammerer K, Urban G
A Sensitive Microsystem as Biosensor for Cell Growth Monitoring and Antibiotic Testing
2006 Sensor Actuat A-phys, Band: 130-131, Seiten: 312 - 321
Bueckling W, Nann T
Electrophoretic Analysis of Gold Nanoparticles: Size-Dependent Electrophoretic Mobility of Nanoparticles
2006 Iet Nanobiotechnol, Band: 153, Nummer: 3, Seiten: 47 - 53
Kucur E, Bueckling W, Arenz S, Giernoth R, Nann T
Heterogeneous Charge Transfer of Colloidal Nanocrystals in Ionic Liquids
2006 Phys Chem Chem Phys, Band: 7, Nummer: 1, Seiten: 77 - 81
Darbandi M, Nann T
One-Pot Synthesis of YF3@Silica Core/Shell Nanoparticles
2006 Chem Commun, Nummer: 16, Seiten: 776 - 778
Xu S, Kumar S, Nann T
Rapid Synthesis of High-Quality InP Nanocrystals
2006 J Am Chem Soc, Band: 128, Nummer: 4, Seiten: 1054 - 1055
Riegger L, Grumann M, Nann T, Riegler J, Ehlert O, Mittenbuehler K, Urban G, Pastewka L, Brenner T, Zengerle R, Ducree J
Read-out Concepts for Multiplexed Bead-based Fluorescence Immunoassays on Centrifugal Microfluidic Platforms
2006 Sensor Actuat A-phys, Band: 126, Nummer: 2, Seiten: 455 - 462
Vulto P, Medoro G, Altomare L, Urban G, Tartagni M, Guerrieri R, Manaresi N
Selective Sample Recovery of DEP-Separated Cells and Particles by Phaseguide-Controlled Laminar Flow
2006 J Micromech Microeng, Band: 16, Nummer: 9, Seiten: 1847 - 1853
Grumann M, Steigert J, Riegger L, Moser I, Enderle B, Riebeseel K, Urban G, Zengerle R, Ducree J
Sensitivity Enhancement for Colorimetric Glucose Assays on Whole Blood by On-Chip Beam-Guidance
2006 Biomed Microdevices, Band: 8, Nummer: 3, Seiten: 209 - 214
Darbandi M, Hoheisel W, Nann T
Silica Coated, Water Dispersible and Photoluminescent Y (V,P)O4:Eu3+,Bi3+ Nanophosphors
2006 Nanotechnology, Band: 17, Nummer: 16, Seiten: 4168 - 4173
Darbandi M, Lu W, Fang J, Nann T
Silica Encapsulation of Hydrophobically Ligated PbSe Nanocrystals
2006 Langmuir, Band: 22, Nummer: 9, Seiten: 4371 - 4375
Kumar S, Thomann R, Nann T
Synthesis and Electrochemical Properties of InP Nanocrystals
2006 J Mater Res, Band: 21, Nummer: 3, Seiten: 543 - 546

2005

nach oben zur Jahresübersicht

Olcaytug F, Szymanowski H, Kaczmarek M, Sobczyk A, Rapiejko C, Schalko J, Piplits K, Gazicki-Lipman M, Yasuda H
Cylindric Electromagnetron Electrode for Continuously Variable PVD/CVD Mixed Processing
2005 Polish Journal of Applied Chemistry, Band: 49, Nummer: 1-2, Seiten: 11 - 21
Babentsov V, Riegler J, Schneider J, Ehlert O, Nann T, Fiederle M
Deep Level Defect Luminescence in CdSe Nanocrystal Films
2005 J Cryst Growth, Band: 280, Nummer: 3-4, Seiten: 502 - 508
Kucur E, Buecking W, Giernoth R, Nann T
Determination of Defect States in Semiconductor Nanocrystals by Cyclic Voltammetry
2005 J Phys Chem B, Band: 109, Nummer: 43, Seiten: 20355 - 20360
Babentsov V, Riegler J, Schneider J, Fiederle M, Nann T
Excitation Dependence of Steady-State Photoluminescence in CdSe Nanocrystal Films
2005 J Phys Chem B, Band: 109, Nummer: 32, Seiten: 15349 - 15354
Nann T
Phase-Transfer of CdSe@ZnS Quantum Dots Using Amphiphilic Hyperbranched Polyethylenimine
2005 Chem Commun, Band: 13, Seiten: 1735 - 1736
Darbandi M, Thomann R, Nann T
Single Quantum Dots in Silica Spheres by Microemulsion Synthesis
2005 Chem Mater, Band: 17, Nummer: 23, Seiten: 5720 - 5725
Kumar S, Ade M, Nann T
Synthesis and Structural Metastability of CdTe Nanowires
2005 Chem-eur J, Band: 11, Nummer: 7, Seiten: 2220 - 2224
Urban GA
[Nanotechnology in medicine].
2005 Praxis (Bern 1994), Band: 94, Nummer: 41, Seiten: 1591 - 1593
KurzfassungIn the past, micro and nano technology were expected to have a considerable meaning for industry and especially for life sciences. The media were prodigal with visions of a tremendous rise of the life span and an enormous amelioration of life quality due to micro and nano submarines in the body and due to novel implants. In spite of these, developments in these disciplines proved to be by far more difficult and therefore lengthy in practice than expected. It is therefore necessary to verify realistically how such high technologies may support medicine. In this article, realised works are treated and new research works presented. Developments in endoscopy, novel materials und the lab on chip reached a sophisticated state of development and are therefore to be included in clinical practice for the future.

2004

nach oben zur Jahresübersicht

Buecking W, Urban G, Nann T
An Electrochemical Biomimetic ATP-Sensor
2004 Sensor Actuat B-chem, Band: 104, Nummer: 1, Seiten: 111 - 116
Kucur E, Riegler J, Urban G, Nann T
Charge Transfer Efficiency in Hybrid Bulk Heterojunction Composites
2004 J Chem Phys, Band: 121, Nummer: 2, Seiten: 1074 - 1079
Nann T, Mulvaney P
Einzelne Quantenpunkte in SiO2-Schalen
2004 Angewandte Chemie, Band: 116, Seiten: 5511 - 5514
Kumar S, Nann T
First Solar Cells Based on CdTe Nanoparticle/MEH-PPV Composites
2004 J Mater Res, Band: 19, Nummer: 7, Seiten: 1990 - 1994
Brabec C, Nann T, Shaheen S
Nanostructured p-n Junctions for Printable Photovoltaics
2004 Mrs Bull, Band: 29, Nummer: 1, Seiten: 43 - 47
Schuderer J, Schmid T, Urban G, Samaras T, Kuster N
Novel High-Resolution Temperature Probe for Radiofrequency Dosimetry
2004 Phys Med Biol, Band: 49, Nummer: 6, Seiten: N83 - N92
Nann T, Schneider J
Origin of Permanent Electric Dipole Moments in Wurtzite Nanocrystals
2004 Chem Phys Lett, Band: 384, Nummer: 1-3, Seiten: 150 - 152
Nann T, Mulvaney P
Single Quantum Dots in Spherical Silica Particles
2004 Angew Chem Int Edit, Band: 43, Nummer: 40, Seiten: 5393 - 5396

2003

nach oben zur Jahresübersicht

Fasching R, Kohl F, Urban G
A Miniaturized Amperometric CO2 Sensor Based on Dissociation of Copper Complexes
2003 Sensor Actuat B-chem, Band: 93, Seiten: 197 - 204
KurzfassungA novel miniaturized amperometric carbon dioxide sensor with fabrication compatibility to most modern MEMS production techniques and with a miniaturization potential down to 100 μm has been developed. The electrochemical detection concept is based on a pH-dependent dissociation of copper complexes. The pH change of an electrolyte solution occurring due a variation of the pCO2 results in a variation of the concentration of free copper ions. In the presence of chloride, the copper ions can be reduced by a quasi-reversible reaction path. The reduction current is taken as measurement signal for the carbon dioxide concentration of an analyte. With the introduction of good-buffer substances as non-volatile ligands for the formation of the copper complexes, a reversible and highly stable chemical system is achieved to allow a radical miniaturization.
Kucur S, Riegler J, Urban G, Nann T
Determination of Quantum Confinement in CdSe Nanocrystals by Cyclic Voltammetry
2003 J Chem Phys, Band: 119, Nummer: 4, Seiten: 2333 - 2337
Kohl F, Fasching R, Keplinger F, Chabicovsky R, Jachimowicz A, Urban G
Development of Miniaturized Semiconductor Flow Sensors
2003 Measurement, Band: 33, Nummer: 2, Seiten: 109 - 119
Kumar S, Nann T
Hexagonal CdTe Nanoparticles of Various Morphologies
2003 Chem Commun, Nummer: 19, Seiten: 2478 - 2479
Petrou P, Moser I, Jobst G
Microdevice Device with Integrated Dialysis Probe and Biosensor Array for Continuous Multi-Analyte Monitoring
2003 Biosens Bioelectron, Band: 18, Nummer: 5-6, Seiten: 613 - 619
Nann T, Heinze J
Simulation in Electrochemistry Using the Finite Element Method - Part 2: Scanning Electrochemical Microscopy
2003 Electrochim Acta, Band: 48, Nummer: 27, Seiten: 3975 - 3980
Riegler J, Nick P, Kielmann U, Nann T
Visualizing the Self-Assembly of Tubulin with Luminescent Nanorods
2003 J Nanosci Nanotechno, Band: 3, Nummer: 5, Seiten: 380 - 385

2002

nach oben zur Jahresübersicht

Petrou P, Moser I, Jobst G
BioMEMS Device with Integrated Microdialysis Probe and Biosensor Array
2002 Biosens Bioelectron, Band: 17, Nummer: 10, Seiten: 859 - 865
Moser I, Jobst G, Urban G
Biosensor Arrays for Simultaneous Measurement of Glucose, Lactate, Glutamate and Glutamine
2002 Biosens Bioelectron, Band: 17, Nummer: 4, Seiten: 297 - 302
Nann T, Kielmann U, Dietrich C
Electrochemical Metallization of Self-Assembled Porphyrin Monolayers
2002 Anal Bioanal Chem, Band: 373, Nummer: 8, Seiten: 749 - 753
Ernst H, Jachimowicz A, Urban GA
High Resolution Flow Characterization in Bio-MEMS
2002 Sensor Actuat A-phys, Band: 100, Nummer: 1, Seiten: 54 - 62
KurzfassungThis paper introduces a micro-sensor compatible with Bio-MEMS applications for wide-range thermal flow rate measurements in liquids. Based on the applied materials and geometry, the sensor allows an outstanding resolution at minimum thermal cross-talk, enabling flow rate measurements down to 100 μg/h in water, i.e. 100 nl/h. Active and passive measuring principles, their respective applications, and the dynamic flow range coverage are presented.
Schwab K, Kannan C, Kienzle F, Moser I, Jobst G, Urban G
Klinische Mikrodialyse: Anwendungen in der Endokrinologie, Diabetologie und bei angeborenen Stoffwechselerkrankungen
2002 Kinder- und Jugendmedizin, Band: A33
Nann T, Riegler J
Monodisperse CdSe Nanorods at Low Temperatures
2002 Chem-eur J, Band: 8, Nummer: 20, Seiten: 4191 - 4795

2001

nach oben zur Jahresübersicht

Rhemrev-Boom MM, Korf J, Venema K, Urban G, Vadgama P
A Versatile Biosensor Device for Continuous Biomedical Monitoring
2001 Biosens Bioelectron, Band: 16, Nummer: 9-12, Seiten: 839 - 847
Nann T, Urban G
Deposition of Hydroquinone-Thiosulfate on Gold by Means of Anodic Oxidation
2001 J Electroanal Chem, Band: 505, Nummer: 1-2, Seiten: 125 - 132
Ernst H, Jachimowicz A, Urban G
Dynamic Thermal Sensor - Principles in MEMS for Fluid Characterization
2001 Ieee Sens J, Band: 1, Nummer: 4, Seiten: 361 - 367
KurzfassungUsing thin-film technology with its characteristic low masses and high aspect ratios a new range of possibilities is made available for the use of dynamic thermal measuring principles. Based on this, a micromachined sensor was developed for the measurement of transient thermal signal responses leading to the thermal characterization of fluids at low sample volumes. The achieved resolution allowed the measurement of thermal parameters of the investigated fluids, i.e., thermal conductivity and specific heat, inside microfluidic systems at a high sensitivity, enabling the detection of inter-fluid boundaries, e.g., as found in micromixers and -reactors, making the sensor a useful tool for micro fluidic system characterization. This is achieved via the measurement of the frequency dependent thermal signal response
Gampp T, Moser I, Jobst G, Urban G, Ayoub M, Pfannes S, Hoffmann P, Bessler W, Mittenbuhler K
Lipopeptide Adjuvants: Generation of Lactate Dehydrogenase Isoenzyme-Specific Antibodies for Immunochemical Diagnosis
2001 Eur J Med Res, Band: 6, Nummer: 1, Seiten: 10 - 20
KurzfassungLactate dehydrogenase catalyzes the final step in glycolysis, the interconversion of pyruvate and lactate. The tetrameric enzyme is composed of one or two subunits (H and/or M) resulting in five isoenzyme forms: LDH-H4, -H3M1, -H2M2, -H1M3, and -M4. The relative distribution of the LDH isoenzymes is tissue dependent and a significant marker for the diagnosis of hepatoma of the liver, myocardial infarction, muscular dystrophy, and a wide variety of other acute and chronic diseases to be detected by alterations of the LDH isoenzyme pattern in serum. Immunochemical approaches to the routine determination of LDH depend on isoenzyme specific antibodies. Since the H- and M-subunits for human LDH are highly homologous, LDH isoenzyme specific antibodies for immunochemical monitoring are hard to generate. Here we present data on the generation and characterization of LDH isoenzyme-specific mono- and polyclonal antibodies in different species in the presence of lipopeptide adjuvants. Western-Blot and ELISA analysis showed that antisera and monoclonal antibodies recognize their homologous antigens with high specificity and are therefore suitable for immunochemical monitoring of the LDH isoenzymes H4 and M4. In addition, they can be used for the determination of LDH isoenzyme specific activity which is an essential prerequisite for online amperometric immunosensor monitoring.

2000

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Nann T, Urban G
A New Dynamic Hydrogen Reference Electrode for Applications in Thin-Film Sensor Systems
2000 Sensor Actuat B-chem, Band: 70, Nummer: 1-3, Seiten: 188 - 195
Glaninger A, Jachimowicz A, Kohl F, Chabicovsky R, Urban G
Wide Range Semiconductor Flow Sensors
2000 Sensor Actuat A-phys, Band: 85, Nummer: 1-3, Seiten: 139 - 146

1999

nach oben zur Jahresübersicht

Urban G
Microstructuring of Organic Layers for Microsystems
1999 Sensor Actuat A-phys, Band: 74, Nummer: 1-3, Seiten: 219 - 224
Nann T, Heinze J
Simulation in Electrochemistry Using the Finite Element Method - Part 1: the Algorithm
1999 Electrochem Commun, Band: 1, Nummer: 7, Seiten: 289 - 294

1998

nach oben zur Jahresübersicht

Ellmerer M, Schaupp L, Trajanoski Z, Jobst G, Moser I, Urban G, Skrabal F, Wach P
Continuous Measurement of Subcutaneous Lactate Concentration During Exercise by Combining Open Flow Microperfusion and Thin-Film Lactate Sensors
1998 Biosens Bioelectron, Band: 13, Nummer: 9, Seiten: 1007 - 1013
Jobst G, Moser I, Urban G, Dubendorfer J, Kunz R
Integrated Optical pH Sensor Using Replicated Chirped Grating Coupler Sensor Chips
1998 Sensor Actuat B-chem, Band: 50, Nummer: 3, Seiten: 210 - 219
Gfrerer R, Brunner G, Trajanoski Z, Schaupp L, Sendlhofer G, Skrabal F, Jobst G, Moser I, Urban G, Pieber T, Wach P
Novel System for Real-Time Ex-Vivo Lactate Monitoring in Human Whole Blood
1998 Biosens Bioelectron, Band: 13, Nummer: 12, Seiten: 1271 - 1278

1997

nach oben zur Jahresübersicht

Dempsey E, Diamond D, Smyth M, Urban G, Jobst G, Moser I, Verpoorte E, Manz A, Michael W, Rabenstein K, Freaney R
Design and Development of a Miniaturised Total Chemical Analysis System for On-Line Lactate and Glucose Monitoring in Biological Samples
1997 Anal Chim Acta, Band: 346, Nummer: 3, Seiten: 341 - 349
Jobst G, Moser I, Svasek P, Varahram M, Trajanoski Z, Wach P, Kotanko P, Skrabal F, Urban G
Mass Producible Miniaturized Flow Through a Device With a Biosensor Array
1997 Sensor Actuat B-chem, Band: 43, Nummer: 1-3, Seiten: 121 - 125
Steinschaden A, Adamovic D, Jobst G, Glatz R, Urban G
Miniaturised Thin Film Conductometric Biosensors With High Dynamic Range and High Sensitivity
1997 Sensor Actuat B-chem, Band: 44, Nummer: 1-3, Seiten: 365 - 369
Freaney R, McShane A, Keaveny T, McKenna M, Rabenstein K, Scheller F, Pfeiffer D, Urban G, Moser I, Jobst G, Manz A, Verpoorte E, Widmer M, Diamond D, Dempsey E, Saez de Viteri F, Smyth M
Novel Instrumentation for Real-Time Monitoring Using Miniaturized Flow Systems With Integrated Biosensors
1997 Ann Clin Biochem, Band: 34, Nummer: 3, Seiten: 291 - 302
Moser I, Jobst G, Svasek P, Svasek E, Varahram M, Urban G
Rapid Liver Enzyme Assay With Miniaturized Liquid Handling System Comprising Thin Film Biosensor
1997 Sensor Actuat B-chem, Band: 44, Nummer: 1-3, Seiten: 377 - 380
Aschauer E, Fasching R, Varahram M, Jobst G, Urban G, Nicolussi G, Husinsky W, Friedbacher G, Grasserbauer M
Surface Modification of Platinum Thin-Film Electrodes Towards a Defined Roughness and Microporosity
1997 J Electroanal Chem, Band: 426, Nummer: 1-2, Seiten: 157 - 165
Moser I, Schalkhammer T, Pittner F, Urban G
Surface Techniques for an Electrochemical DNA Biosensor
1997 Biosens Bioelectron, Band: 12, Nummer: 8, Seiten: 729 - 737

1996

nach oben zur Jahresübersicht

Jobst G, Moser I, Urban G
Numerical Simulation of Multi-Layered Enzymatic Sensors
1996 Biosens Bioelectron, Band: 11, Nummer: 1, Seiten: 111 - 117
Trajanoski Z, Wach P, Gfrerer R, Jobst G, Urban G, Kotanko P, Skrabal F
Portable Device for Continuous Fractionated Blood Sampling and Continuous Ex-Vivo Blood Glucose Monitoring
1996 Biosens Bioelectron, Band: 11, Nummer: 5, Seiten: 479 - 487
Jobst G, Moser I, Varahram M, Svasek P, Aschauer E, Trajanoski Z, Wach P, Kotanko P, Skrabal F, Urban G
Thin-Film Microbiosensors for Glucose-Lactate Monitoring
1996 Anal Chem, Band: 68, Nummer: 18, Seiten: 3173 - 3179

1995

nach oben zur Jahresübersicht

Moser I, Jobst G, Aschauer E, Svasek P, Varahram M, Urban G, Zanin V, Tjoutrina G, Zharikova A, Berezov T
Miniaturized Thin Film Glutamate and Glutamine Biosensors
1995 Biosens Bioelectron, Band: 10, Nummer: 6-7, Seiten: 527 - 532
Yu L, Jobst G, Moser I, Urban G, Gruber H
Photolithographically Patternable Modified Poly(HEMA) Hydrogel Membrane
1995 Polym Bull, Band: 35, Nummer: 6, Seiten: 759 - 765
Aschauer E, Fasching R, Urban G, Nicolussi G, Husinsky W
Surface Characterization of Thin-Film Platinum-Electrodes for Biosensors by Means of Cyclic Voltammetry and Laser SNMS
1995 J Electroanal Chem, Band: 381, Nummer: 1, Seiten: 143 - 150

1994

nach oben zur Jahresübersicht

Kohl F, Jachimowicz A, Steurer J, Glatz R, Kuttner J, Biacovsky D, Olcaytug F, Urban G
A Micromachined Flow Sensor for Liquid and Gaseous Fluids
1994 Sensor Actuat A-phys, Band: 41, Nummer: 1-3, Seiten: 293 - 299
Hofer E, Urban G, Spach M, Schafferhofer I, Mohr G, Platzer D
Measuring Activation Patterns of the Heart at a Microscopic Size Scale with Thin-Film Sensors
1994 Am J Physiol-heart C, Band: 266, Nummer: 5, Seiten: H2136 - H2145

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Urban G, Jobst G, Keplinger F, Aschauer E, Fasching R, Svasek P
Miniaturized Integrated Biosensors
1994 Technology and Health Care, Band: 1, Seiten: 215 - 218
Urban G, Jobst G, Aschauer E, Tilado O, Svasek P, Varahram M, Ritter C, Riegebauer J
Performance of Integrated Glucose and Lactate Thin Film Micro-Biosensors for Clinical Analyzers
1994 Sensor Actuat B-chem, Band: 19, Nummer: 1-3, Seiten: 592 - 596

1993

nach oben zur Jahresübersicht

Jobst G, Urban G, Jachimowicz A, Kohl F, Tilado O, Lettenbichler I, Nauer G
Thin-Film Clark-Type Oxygen Sensor Based on Novel Polymer Membrane Systems for In-Vivo and Biosensor Applications
1993 Biosens Bioelectron, Band: 8, Nummer: 3-4, Seiten: 123 - 128

1992

nach oben zur Jahresübersicht

Moser I, Schalkhammer T, Mann-Buxbaum E, Hawa G, Rakohl M, Urban G, Pittner F
Advanced Immobilization and Protein Techniques on Thin Film Biosensors
1992 Sensor Actuat B-chem, Band: 7, Nummer: 1-3, Seiten: 356 - 362
Ferry R, Misbichler A, Harter E, Mann-Buxbaum E, Schalkhammer T, Urban G, Pittner F
Construction and Use of Two Alpha-Human Adrenalnatriuretic Peptide-Fragment Affinity Chromatography Columns in the Isolation Of C-Terminal Epitope Specific Antibody for Use in a Prototype Alpha-HANAP Biosensor
1992 J Chromatogr B, Band: 577, Seiten: 251 - 265
Urban G, Jobst G, Keplinger F, Aschauer E, Tilado O, Fasching R, Kohl F
Miniaturized Multi-Enzyme Biosensors Integrated with pH Sensors on Flexible Polymer Carriers for In-Vivo Applications
1992 Biosens Bioelectron, Band: 7, Nummer: 10, Seiten: 733 - 739
Urban G
Miniatursensoren zur kontinuierlichen Erfassung metabolischer Parameter
1992 Acta Medica Austriaca, Band: 19, Ergänzungsband: 2, Seiten: 38 - 38

1991

nach oben zur Jahresübersicht

Schalkhammer T, Mann-Buxbaum E, Pittner F, Urban G
Electrochemical Glucose Sensors on Permselective Non-conducting Substituted Pyrrole Polymers
1991 Sensor Actuat B-chem, Band: 4, Nummer: 3-4, Seiten: 273 - 281
Kuttner H, Urban G, Jachimowicz A, Kohl F, Olcaytug F, Goiser P
Microminiaturized Thermistor Arrays for Temperature Gradient, Flow and Perfusion Measurements
1991 Sensor Actuat A-phys, Band: 27, Nummer: 1-3, Seiten: 641 - 645
Urban G, Jobst G, Kohl F, Jachimowicz A, Olcaytug F, Tilado O, Goiser P, Nauer G, Pittner F, Schalkhammer T, Mann-Buxbaum E
Miniaturized Thin-Film Biosensors Using Covalently Immobilized Glucose Oxidase
1991 Biosens Bioelectron, Band: 6, Nummer: 7, Seiten: 555 - 562
Urban G, Kamper H, Jachimowicz A, Kohl F, Kuttner H, Olcaytug F, Goiser P, Pittner F, Schalkhammer T, Mann-Buxbaum E
The Construction of Microcalorimetric Biosensors by Use of High Resolution Thin-Film Thermistors
1991 Biosens Bioelectron, Band: 6, Nummer: 3, Seiten: 275 - 280

1990

nach oben zur Jahresübersicht

Pifl C, Jachimowicz A, Urban G, Kohl F, Goiser P, Theiner J, Nauer G
A New Type of Thin-Layer Microelectrode for In Vivo Voltammetry: Electro-Oxidation of Dopamine, DOPAC and Ascorbic Acid
1990 Sensor Actuat B-chem, Band: 1, Nummer: 1-6, Seiten: 468 - 472
Schalkhammer T, Mann-Buxbaum E, Urban G, Pittner F
Biosensors on Thin-Film Metals and Polymer-Coated Electrodes
1990 Fresenius' Journal of Analytical Chemistry, Band: 337, Nummer: 1, Seiten: 107 - 109
Gazicki M, Pirker K, Schallauer R, Fallmann W, Olcaytug F, Urban G, Jachimowicz A, Kohl F
Deposition and Properties of Germanium-Carbon Alloy Films Produced from Tetraethylgermanium in an R.F. Discharge
1990 Thin Solid Films, Band: 187, Nummer: 1, Seiten: 51 - 63
Urban G, Ganglberger J, Olcaytug F, Kohl F, Schallauer R, Trimmel M, Schmid H, Prohaska O
Development of a Multiple Thin-Film Semimicro DC-Probe for Intracerebral Recordings (During Surgery)
1990 Ieee T Bio-med Eng, Band: 37, Nummer: 10, Seiten: 913 - 918
Schalkhammer T, Mann-Buxbaum E, Urban G, Pittner F
Electrochemical Biosensors on Thin-Film Metals and Conducting Polymers
1990 J Chromatogr A, Band: 510, Seiten: 355 - 366
Urban G, Jachimowicz A, Kohl F, Kuttner H, Olcaytug F, Goiser P, Lindner K, Pockberger H, Prohaska O, Schoenauer M
High Resolution Multi-Temperature Sensors for Biomedical Application
1990 Medical Progress through Technology, Band: 16, Nummer: 3, Seiten: 173 - 181

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Mann-Buxbaum E, Pittner F, Schalkhammer T, Jachimowicz A, Jobst G, Olcaytug F, Urban G
New Microminiaturized Glucose Sensors Using Covalent Immobilization Techniques
1990 Sensor Actuat B-chem, Band: 1, Nummer: 1-6, Seiten: 518 - 522
Keplinger F, Glatz R, Jachimowicz A, Urban G, Kohl F, Olcaytug F, Prohaska O
Thin-Film Ion-Selective Sensors Based on Neutral Carrier Membranes
1990 Sensor Actuat B-chem, Band: 1, Nummer: 1-6, Seiten: 272 - 274

1989

nach oben zur Jahresübersicht

Ullrich B, Kuchar F, Meisels R, Olcaytug F, Jachimowicz A
Capacitance-Voltage Measurements on a p-Type InSb Metal/Insulator/Semiconductor Structure with Si3N4 as the Insulator
1989 Thin Solid Films, Band: 168, Nummer: 2, Seiten: 157 - 163
Urban G, Jachimowicz A, Kohl F, Kuttner H, Olcaytug F, Kamper H, Pittner F, Mann-Buxbaum E, Schalkhammer T, Prohaska O, Schoenauer M
High-Resolution Thin-Film Temperature Sensor Arrays for Medical Applications
1989 Sensor Actuat A-phys, Band: 22, Nummer: 1-3, Seiten: 650 - 654

1986

nach oben zur Jahresübersicht

Urban G, Steiger W, Rudenauer F, Schallauer R
A Thin-Film Bolometer for Particle Current Measurements
1986 Journal of Physics E: Scientific Instruments, Band: 19, Nummer: 2, Seiten: 119 - 123
Pirker K, Schallauer R, Fallmann W, Olcaytug F, Urban G, Jachimowicz A, Kohl F, Prohaska O
Production and Properties of Conducting Carbon Films
1986 Thin Solid Films, Band: 138, Nummer: 1, Seiten: 121 - 129

1982

nach oben zur Jahresübersicht

Rieder G, Olcaytug F
Preparation and Dielectric Properties of Si3N4 Thin Films
1982 Thin Solid Films, Band: 89, Nummer: 1, Seiten: 95 - 99

1980

nach oben zur Jahresübersicht

Olcaytug F, Riedling K, Fallmann W
A Low Temperature Process for the Reactive Formation of Si3N4 Layers on InSb
1980 Thin Solid Films, Band: 67, Nummer: 2, Seiten: 321 - 324

Reviews/Übersichtsartikel in wissenschaftlichen Fachzeitschriften

Jahre: 2011 | 2010 | 2009 | 2006 | 2005 | 2004

zurück zur Übersicht aller Publikationen

2011

nach oben zur Jahresübersicht

Yuan Y, Krueger M
Polymer-Nanocrystal Hybrid Materials for Light Conversion
2011 Polymers, Band: 4, Seiten: 1 - 19

2010

nach oben zur Jahresübersicht

Zhou Y, Eck M, Krueger M
Bulk-Heterojunction Hybrid Solar Cells Based on Colloidal Nanocrystals and Conjugated Polymers
2010 Energy & Environmental Science, Band: 3, Nummer: 2, Seiten: 1851 - 1864
Heinze J, Frontana-Uribe B, Ludwigs S
Electrochemistry of Conducting Polymers—Persistent Models and New Concepts
2010 Chem Rev, Band: 110, Nummer: 8, Seiten: 4724 - 4771

2009

nach oben zur Jahresübersicht

Urban G
Reinhard Renneberg and Fred Lisdat (eds.): Biosensing for the 21st Century
2009 Anal Bioanal Chem, Band: 393, Nummer: 3, Seiten: 777 - 778

2006

nach oben zur Jahresübersicht

Kumar S, Nann T
Shape Control of II–VI Semiconductor Nanomaterials
2006 Small, Band: 2, Nummer: 3, Seiten: 316 - 329

2005

nach oben zur Jahresübersicht

Steigert J, Grumann M, Brenner T, Mittenbühler K, Nann T, Rühe J, Moser I, Haeberle S, Riegger L, Riegler J, Bessler W, Zengerle R, Ducree J
Integrated Sample Preparation, Reaction, and Detection on a High-frequency Centrifugal Microfluidic Platform
2005 Journal of the Association for Laboratory Automation, Band: 10, Nummer: 5, Seiten: 331 - 341

2004

nach oben zur Jahresübersicht

Riegler J, Nann T
Application of Luminescent Nanocrystals as Labels for Biological Molecules
2004 Anal Bioanal Chem, Band: 379, Nummer: 7-8, Seiten: 913 - 919

Rezensionen

Jahre: 2016 | 2013

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2016

nach oben zur Jahresübersicht

Urban G
Jacob Fraden: Handbook of modern sensors
2016 Springer

2013

nach oben zur Jahresübersicht

Urban G
Florinel-Gabriel Banica: Chemical Sensors and Biosensors: Fundamentals and Applications
2013 Anal Bioanal Chem

Monographien

Jahre: 2014 | 2006

zurück zur Übersicht aller Publikationen

2014

nach oben zur Jahresübersicht

De Gruyter
Biomedizinische Technik – Biomaterialien, Implantate und Tissue Engineering
ISBN: 978-3-11-025216-3
Glasmacher B, Urban G, Sternberg K, Müller M

2006

nach oben zur Jahresübersicht

Springer US, Seite: 365
BioMEMS (Microsystems)
ISBN: 0387287310 / 978-0387287317
Urban G
KurzfassungExplosive growth in the field of microsystem technology (MST) has introduced a variety of promising products in major disciplines from microelectronics to life sciences. Especially the life sciences and health care business was, and is expected to be a major market for MST products. Undoubtedly the merging of biological sciences with micro- and nanoscience will create a scientific and technological revolution in future. Microminiaturization of devices, down to the nanoscale, approaching the size of biological structures, will be a prerequisite for the future success of life sciences. Bioanalytical and therapeutic micro- and nanosystems will be mandatory for system biologists in the long run, to obtain insight into morphology, the function and the interactive processes of the living system. With such a deeper understanding new and personalized drugs could be developed leading to a revolution in life sciences. Today, microanalytical devices are used in clinical analytics or molecular biology as gene chips. In parallel, standard microbiomedical products are employed in the intensive care and surgical theatre, mainly for monitoring and implantation purposes. The gap between these two different scientific fields will be closed, however, as soon as functional micro devices can be produced, allowing a deeper view into the function of cells and whole organisms. Here, a new discipline evolved which focuses on microsystems for living systems called "BIOMEMS". In this review at a glance the exciting field of bio-microsystems, from their beginnings to indicators of future successes are presented. It will also show that a broad penetration of micro and nano technologies into biology and medicine will be mandatory for future scientific and new product development progress in life science.

Buchbeiträge

Jahre: 2020 | 2017 | 2014 | 2011 | 2010 | 2009 | 2006 | 2001 | 1990 | 1989 | 1986

zurück zur Übersicht aller Publikationen

2020

nach oben zur Jahresübersicht

Brunauer A, Ates H, Dincer C, Früh S
Paper Based Sensors, Volume 89
In: Integrated paper-based sensing devices for diagnostic applications
2020, Elsevier B.V., Seiten: 1 - 54, ISBN: 9780444643452
KurzfassungPaper-based sensing platforms are one of the most powerful tools for point-of-care diagnostics. The ease of use while ensuring low production costs of such devices is the key for paper-based technologies to find their way to a successful commercialization. Thus, all steps in the analytical process chain from sample interface, sample preparation, signal amplification to signal transduction and data analysis have to be integrated in a single diagnostic platform. In this chapter, we provide a comprehensive and critical overview on recent developments towards integrated paper-based platforms in academia and industry. Herein, innovative solutions are discussed with respect to their sampling methods such as invasive and non-invasive approaches. We also address the requirements and challenges for the sampling and analysis of the different body fluids. Finally, we present our views about the future perspectives, challenges, and opportunities of the integrated paper-based devices.

2017

nach oben zur Jahresübersicht

Karthe D, Behrmann O, Blättel V, Elsässer D, Heese C, Hügle M, Hufert F, Kunze A, Niessner R, Otto J, Scharaw B, Spoo M, Tiehm A, Urban G, Vosseler S, Westerhoff T, Seidel M, Dame G
Innovative Hygieneüberwachung von Roh- und Trinkwasser
In: Wasserinfrastrukturen für die zukunftsfähige Stadt – Beiträge aus der INIS-Forschung
2017, Deutsches Institut für Urbanistik, Seiten: 60 - 63,

2014

nach oben zur Jahresübersicht

Glasmacher B, Urban G, Sternberg K, Kraft M, Moussavi D, Bergmann M
Biomaterialien, Implantate, Tissue Engineering
In: Biomedizinische Technik – Faszination, Einführung, Überblick (Band 1)
2014, De Gruyter, Seite: 131, ISBN: 978-3-11-025218-7

2011

nach oben zur Jahresübersicht

Pruszak J, Döbrössy M, Kieninger J, Aravindalochanan K, Urban G, Nikkhah G
Neural Stem Cells: From Cell Fate and Metabolic Monitoring Towards Clinical Applications
In: Stem Cell Engineering
2011, Springer Verlag, G. Artmann, Seiten: 435 - 455, G. Artmann,
Zhou Y, Eck M, Krueger M
Organic-Inorganic Hybrid Solar Cells: State of the Art, Challenges and Perspectives
In: Solar Cells-New Aspects and Solutions
2011, Intech publisher, Leonid A. Kosyachenko, Seiten: 95 - 120, Leonid A. Kosyachenko, ISBN: ISBN 979-953-307-191-5

2010

nach oben zur Jahresübersicht

Jeschke S., Hauck E, Krueger M, Osten W, Pfeiffer O, Richter T
Part V: Networking Resources for Research and Scientific Education in BW-eLabs
In: Remote Instrumentation Services on the E-Infrastructure: Applications and Tools
2010, Springer Verlag, Eds.: F. Davoli, N. Meyer, R. Pugliese, S. Zappatore, Eds.: F. Davoli, N. Meyer, R. Pugliese, S. Zappatore,

2009

nach oben zur Jahresübersicht

Urban G, Guttmann J, Kieninger J, Weltin A, Wöllenstein J, Zosel J
CO₂ Sensing in Medicine
In: Carbon Dioxide Sensing: Fundamentals, Principles, and Applications
2009, Wiley‐VCH Verlag GmbH & Co. KGaA, Seiten: 391 - 413, ISBN: 9783527688302
KurzfassungThe measurement of biochemical parameters is primarily done in centralized laboratories, in intensive care units, and in the operating theatre with near‐patient point‐of‐care testing (POCT). The measurement of carbon dioxide (CO₂) in blood as a part of the so‐called blood gas panel. POCT is a patient‐centred diagnostic test that is not performed in a centralized laboratory, but in the hospital immediately near the operating room or intensive care or in the ambulance. CO₂ is a gaseous waste product of metabolism and physiologically very tightly controlled. The CO₂ balance is maintained by a carbonate buffer system in blood. Clinical blood gas analysis systems can be grouped into devices for single analysis of a discrete blood sample and continuous monitoring devices. The measurement of CO₂ in human breath – called capnometry – is common practice in respiratory gas monitoring in intensive caremedicine, emergency medicine, and anaesthesiology.
Urban G, Weiss T
Hydrogels for Biosensors
In: Hydrogel Sensors and Actuators: Engineering and Technology
2009, Springer Verlag, Seiten: 197 - 220, ISBN: 978-3-540-75644-6

2006

nach oben zur Jahresübersicht

Nann T, Riegler J, Urban G
Biomedical Microsystems (Bio-MEMS)
In: n.n.
2006, n.n., Seiten: 351 - 373,

2001

nach oben zur Jahresübersicht

Urban G
Biosensor Microsystem
In: Sensors Update 8
2001, n.n., Baltes, Göpel, Hesse, Seiten: 189 - 214, Baltes, Göpel, Hesse,

1990

nach oben zur Jahresübersicht

Olcaytug F, Pirker K, Schallauer R, Kohl F, Urban G, Jachimowicz A, Prohaska O, Fallmann W, Riedling K
Amorphous Carbon Films for Sensor Applications
In: Properties and Characterization of Amorphous Carbon Films
1990, Transtech Verlag, J. J. Pouch and S. A. Alterovitz, Seiten: 671 - 688, J. J. Pouch and S. A. Alterovitz,
Pittner F, Schalkhammer T, Mann Buxbaum E, Urban G
Miniaturized Thin-Film Biosensors
In: Micro System Technologies
1990, Springer Verlag, H. Reichl, H. Reichl, ISBN: 0387530258 / 0-387-53025-8

1989

nach oben zur Jahresübersicht

Urban G, Kohl F, Kuttner H, Jachimowicz A, Olcaytug F, Tilado O, Jobst G, Pittner F, Mann-Buxbaum E, Schalkhammer T
Mikrominiaturisierte Biosensoren
In: Mikroelektronik 89: Berichte der Informationstagung
1989, Springer Verlag, Wie ME, Seiten: 363 - 369, Wie ME, ISBN: 3211821716

1986

nach oben zur Jahresübersicht

Kohl F, Urban G, Olcaytug F, Jachimowicz A, Pirker, Schallauer R, Goiser P
Neuere Entwicklungen auf dem Gebiet der Mehrfach-Mikrosensoren
In: Medizin-Technik: medizinische Informatik '86
1986, Österreichischen Gesellschaft für Biomedizinische Technik, P. Rappelsberger, P. Rappelsberger, ISBN: 3-486-20306-1

Vorträge

Jahre: 2019 | 2015 | 2014 | 2013 | 2012 | 2011 | 2010 | 2009 | 2008 | 2007 | 2006

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2019

nach oben zur Jahresübersicht

Bruch R, Baaske J, Chatelle C, Weber W, Urban G, Dincer C
MicroRNA diagnostics on an electrochemical biosensor via CRISPR/Cas13a technology
2019 MicroTAS 2019, Basel, Switzerland
Wieland T, Kotthaus K, Bergmann M, Ledernez L, Altenburger M, Urban G
Thermal sensor system for the measurement of biofilm formation and bactericidal efficacy by the transient spark disinfection in real-time
2019 6th International Conference on Bio-Sensing Technology, Kuala Lumpur, Malaysia

2015

nach oben zur Jahresübersicht

Bergmann M, Lickert S, Ledernez L, Urban G
Plasma Nanofilm as Biocompatible and Antibacterial Coating for Biomaterials
2015 International Society for Biomedical Polymers and Polymeric Biomaterials
Kling A, Dincer C, Armbrecht L, Horak J, Kieninger J, Urban G
Microfluidic multiplexed electrochemical biosensor platform
2015 BMT 2015, Lübeck, Germany

2014

nach oben zur Jahresübersicht

Bergmann M, Lickert S, Ledernez L, Dame G, Urban G
Plasma Nanofilms as Biocompatible and Antibacterial Interface for Biomaterials
2014 Deutsche Gesellschaft für Biomedizinische Technik (DGBMT 2014)

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2013

nach oben zur Jahresübersicht

Bergmann M, Ledernez L, Lickert S, Dame G, Urban G
Magnetron Enhanced Plasma Nanofilms as Biocompatible and Antibacterial Coating for Biosensors
2013 I3TM Symposium
Bergmann M, Dame G, Urban G
Plasma Nanofilms as Biocompatible and Antibacterial Coatings
2013 Dreiländertagung der Deutschen, Schweizerischen und Österreichischen Gesellschaft für Biomedizinische Technik (BMT 2013)

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Bergmann M, Ledernez L, Dame G, Urban G
Magnetron Enhanced Plasma Process for Antibacterial Coating of Rigid and Hydrogel Contact Lenses
2013 ISPC-21, Cairns, Australia

2012

nach oben zur Jahresübersicht

Bergmann M, Enderle B, Weltin A, Dame G, Urban G
Biocompatible and Antibacterial Plasma Nanofilms Tailored for Biomedical Applications
2012 Semicon 2013

2011

nach oben zur Jahresübersicht

Krueger M
Efficiency Enhancement of Bulk-Heterojunction Hybrid Solar Cells Towards 3.5% by Postsynthetic Surface Treatments of Semiconductor Nanocrystals
2011 2011 MRS Fall Meeting, November 28 - December 2, 2011 Hynes Convention Center, Boston, MA (USA)
Riehle F, Eck M, Krueger M
Quantum Dots, Defect states and Solar Cell Efficiency
2011 2011 MRS Fall Meeting, November 28 - December 2, 2011 Hynes Convention Center, Boston, MA (USA)
Einwaechter S, Krueger M
Multiparametric exploration and optimization of nanoparticle syntheses based on a fully automated synthesis setup with integrated online spectroscopy
2011 2011 MRS Fall Meeting, November 28 - December 2, 2011 Hynes Convention Center, Boston, MA , USA
Krueger M
Towards Nanostructured Solar Cells
2011 Quantum Efficiency Seminar, Physikalisches Institut, Universität Freiburg
Eck M., Krueger M.
Efficiency Enhancement of Hybrid Solar Cells by Improving Charge Transfer and Transport
2011 Quantum Coherence Workshop Freiburg 24.-28.10.2011
Krueger M
Critical Parameters for the Efficiency Enhancement of Inorganic Nanocrystal Based Bulk-Heterojunction Hybrid Solar Cells
2011 BITs 1st Annual World Congress of Nano-S &T October 23-26, 2011, Dalian, China
Eck M., Krueger M.
Efficiency Enhancement of Hybrid Solar Cells by Improving Charge Transfer and Transport
2011 FMF Kolloquium 17.-18.10.2011
Krueger M
Multiparametric exploration and optimization of nanoparticle syntheses based on a fully automated synthesis set-up with integrated online spectroscopy
2011 FMF Kolloquium 17.-18.10.2011
Stevens G, Silver D, Zgaga-Griesz A, Urban G, Krueger M
Rapid, Sensitive Detection of Clostridium Botulinum Neurotoxin in Blood Plasma
2011 48th Annual Interagency Botulism Research Coordinating Committee (IBRCC) Meeting, Santa Fe, New Mexico, US, October 5-7, 2011
Krueger M
Synthesis of (luminescent) inorganic (semiconductor) nanoparticles
2011 LAMP Workshop 07.-08.09.2011, University of Wuppertal, Inst. f. Polymer Technology
Eck M., Zhou Y., Yuan Y., Riehle F., Einwächter S., Krüger M.
Correlation between the photoluminescence of CdSe nanocrystals and their performance in hybrid solar cells
2011 4th International Symposium for Organic Electronics 2011 (ISFOE11) 10-13 July 2011, Thessaloniki (Greece)
Zhou Y, Eck M, Krueger M
Efficient Polymer/CdSe Hybrid Solar Cells by Improving the Nanocrystal Composition
2011 EMRS Spring Meeting, May 9-13 (2011), Congress Center, Nice (France)
Yuan Y, Riehle F, Nitschke R, Krueger M
Nanocrystal-Polymer Hybrid Materials for Energy Conversion and Fluorescence Standard Development
2011 E-MRS Spring Meeting, May 9-13 2011, Congress Center, Nice (France),
Krueger M
Novel approaches to semiconductor nanocrystals and their integration into advanced hybrid solar cells
2011 EMRS Spring Meeting, May 09-13, 2011, Congress Center Nice (France)
Krueger M, Zhou Y, Eck M
Efficiency enhancement of bulk-heterojunction hybrid solar cells towards 3% and beyond
2011 MRS Spring Meeting, San Franciso, 25.04-29.04.2011
Krueger M, Zhou Y, Eck M
Efficiency enhancement of bulk-heterojunction solar cells.
2011 DPG Frühjahrstagung in Dresden, 13.03.-18.03.2011
Aravindalochanan K, Kieninger J, Flamm H, Urban G
An Integrated Bio-MEMS Measurement Platform for Nitric Oxide Research
2011 Gordon Research Conference on Nitric Oxide, Ventura, CA
Bakirci H
Disposable Micro-Immunochips for Early Detection of Cardiovascular Diseases
2011 Biovalley Meet&Match Microfluidics/Lab on Chip, Karlsruhe, Germany
Riehle F, Krueger M
Quantum Dots, Defect States and Solar Cell Efficiency
2011 Quantum Efficiency Seminar, Physikalisches Institut, Universität Freiburg

2010

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Bakirci H
A microchip capillary immunoassay system for rapid and highly sensitive measurement of neuromarkers
2010 Biovalley Meet&Match Biomarkers, Mulhouse, France
Krueger M
Nanocrystal-polymer hybrid materials for applications in light and energy conversion
2010 Kolloquium "Kondensierte Materie", Physik Department, Universität Basel

2009

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Krueger M
Improved efficiencies of hybrid solar cells based on CdSe quantum dots and poly(3-hexylthiophene)
2009 Nanotech Europe 2009, Berlin, Germany
Krueger M
Nanoparticle containing hybrid materials for photovoltaic applications and fuel cell electrodes
2009 Physikalisches Kolloquium, Institut f. Physik, Universität Basel, Schweiz
Krueger M
Nanoparticles for (Bio-)Medical Applications
2009 111th International Congress of Medical Physics and Biomedical Engineering, Munich

2008

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Riehle F, Bienert R, Thomann R, Urban G, Krueger M
A New Type of Ultra Small CdSe Nanoparticle with Exceptional Optical and Chemical Behaviour
2008 IC4N 2008: 1st International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems, Halkidiki, Greece
Krueger M, Riehle F, Bienert R, Thomann R, Urban G
Blue Luminescence and Superstructures from Magic Size Clusters of CdSe
2008 NANAX 3 Conference: Nanoscience with nanocrystals, Lecce, Italy
Zhou Y, Urban G, Krueger M
Bulk-Heterojuction Solar Cells Based on Nanocrystal-Polymer Hybrid Materials
2008 17. FMF Kolloquium, Hornberg
Krueger M, Yuan Y, Riehle F S, Gu H, Urban G
Critical Parameters for the Synthesis of Semiconducting Nanocrystals (Quantum Dots)
2008 IC4N 2008: 1st International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems, Halkidiki, Greece
Kieninger J
Global and local oxygen control in in vitro systems
2008 EUROXY course, Tuscany, Italy
Krueger M
Nanopartikel-Quo Vadis
2008 17. FMF Kolloquium, Hornberg
Krueger M
Nanoscience at the Freiburg Materials Research Centre
2008 Vortrag am Institut für Physik, Universität Basel
Hussein L, Urban G, Krueger M
Novel Ultra-Small Nanoparticles on Nanotube Buckypaper as Electrocatalyst for Implantable Glucose Fuel Cells
2008 17. FMF Kolloquium, Hornberg

2007

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Krueger M
Anwendungen von halbleitenden Nanokristallen in der Biologie, den Materialwissenschaften und der Medizin
2007 16. FMF Kolloquium, Rust
Riehle F, Urban G A, Cardot P J, Krueger M
Celllsorting with nanocrystals
2007 16. FMF Kolloquium, Rust
Kieninger J
Tools for oxygen measurement
2007 EUROXY course, Maastricht, Netherlands

2006

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Krueger M
Bausteine für Quantenaggregate
2006 Quantenaggregate Seminar, Institut für Physik, Universität Freiburg

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2020

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Farahani H, Wagiran R, Urban G
Capacitive Properties of Ceramic Humidity Sensors Made from Porous Perovskite Films
2020 IEEE SENSORS 2020
KurzfassungIn this research, ceramic-based capacitive humidity sensors based on the barium strontium titanate perovskite nanocomposite and doped with the various concentrations of magnesia nanoparticles were fabricated and investigated. The particle size of the sensing elements is varied from 56 nm to 35 nm per dopant surcharges. The interaction between bulk perovskites (pellet) and water vapor was studied by impedance spectroscopy. Presence of the ionic transport even at low RH values is observed from the bulk frequency-capacitance spectra. The EIS results of the bulk sample confirm that the proton transfer operates only by charge transfer kinetics and not diffusion process to metals (up to 90% RH). Among all the proposed sensors, the device contains of 3 mol% magnesia exhibits the most capacitance change (21 pF – 25200 pF) with the sensitivity of 335 pF/RH% in the range of 20–95% RH, and a maximum hysteresis of 5.2% RH at 60% RH. The impact of rest of dopant values on the main perovskite is negative.

2019

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Hügle M, Siegel L, Behrmann O, Hufert FT, Dame G, Urban G
A Lab-on-a-Chip For The Extraction Of Bacterial Nucleic Acids From Whole Human Blood
2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), Berlin, Germany
KurzfassungWe present a lab-on-a-chip for the extraction of bacterial nucleic acids from whole human blood (WHB). Compared to classical methods, with extraction times between hours and days, the presented chip can lyse the bacteria suspended in WHB and extract their nucleic acids within three minutes. This is achieved by directly coupling thermal lysis to gel-electrophoresis on a single microfluidic platform.
Laubender E, Matylitskaya V, Kostal E, Kasemann S, Urban G, Partel S, Dincer C
Gold nanogap interdigitated arrays for redox cycling amplified dopamine detection
2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), Berlin, Germany
KurzfassungHere we present the highly sensitive detection of dopamine using gold nanogap IDAs with redox-cycling amplification. Through the combination with a facile electrochemical activation and a chronoamperometric multistep protocol fouling of the gold electrode surface can be prevented and a sensitivity of 14 nA µM⁻¹ with excellent linearity up to 10 µM is achieved. The low-cost and reproducible wafer level fabrication process of the nanogap IDAs plays a key role. Electrode and substrate materials can be nearly arbitrarily chosen. Also the gap sizes could be adjusted down to sub-100 nm dimensions with this versatile approach, allowing for very high signal amplification. In comparison to the current gold standard, fastscan cyclic voltammetry (FSCV) with carbon fiber microelectrodes (CFMEs), which suffers from high background currents, no elaborate data processing and high-end electronic equipment is needed. Employing our flexible, easy and inexpensive method, DA monitoring with a short acquisition period and a detection limit less than 200 nM is successfully demonstrated.
Wieland T, Kotthaus JK, Gmoser H, Assmann J, Urban G
Inhibition of MDR/MRSA Bacterial Biofilms by the Antimicrobial Peptides Esculaentin 1-A and OH-CATH-30 Monitored by a Thermal Sensor System in Real-Time
2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), Berlin, Germany
KurzfassungIn the present work, we showcase a reusable miniaturized thermal sensor based on sinusoidal excitation for continuous monitoring of biofilms over several days. The sensor measurement system is able to steadily monitor biofilm formation with very low baseline. The presented measurement method utilized for this application is based on the change in thermal properties, specific thermal conductivity and volumetric heat capacity, which leads to different measurement results due to maturation of biofilm. In this work, we describe how the system can detect the inhibition of biofilm formation by the effect of the antimicrobial peptides (AMP) Esculentin 1-a and OH-CATH-30.
Urban S, Kieninger J, Deschner BJ, Kraut M, Dittmeyer R, Urban G, Weltin A
Multiparametric, Spatially Resolved Detection of H2O2 and O2 with Electrochemical Microsensor Array in Synthesis Membrane Microreactors
2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), Berlin, Germany
KurzfassungWe present an electrochemical microsensor system for the multiparametric detection of dissolved concentrations of hydrogen peroxide (H₂O₂) and oxygen (O₂) inside a direct synthesis membrane microreactor. Both reactants are detected with high sensitivity on the same Pt-based electrode by changing the applied measurement potential in a chronoamperometric protocol. The robust integration of the electrochemical cell in the microreactor was demonstrated and allowed for in situ detection of the spatial gradient of the changing oxygen concentration diffusing through a membrane into the microreactor, emphasizing the capabilities of our monitoring system.
Dornhof J, Kieninger J, Maurer J, Urban G, Weltin A
Next Generation Organ-on-Chip System for Directional Control of Culture Conditions and Metabolic Monitoring of Tumor Organoids
2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), Berlin, Germany
KurzfassungIn vitro replica of 3D heterogeneous tumor systems are essential models on the path towards personalized chemotherapy in cancer research. Here, we present an organ-on-chip platform with integrated microelectrodes enabling online-monitoring of culture conditions and metabolic parameters of patient-derived, triple-negative breast cancer stem cells. Tumor organoids grow in compartments separated by microfluidic channels, permitting the generation of oxygen and drug gradients as seen in real tumors. Besides the electrochemical analysis, e.g. for oxygen or lactate, the transparent chip also allows characterization with optical methods. Such in situ monitoring systems bear a high potential for replacing animal models in drug research.
Marzioch J, Kieninger J, Weltin A, Urban G
Oxygen Microsensor Array to Study Spatial Efficacy of Photodynamic Therapy in Vitro
2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII), Berlin, Germany
KurzfassungWe present a cell culture monitoring platform to study effects of photodynamic therapy (PDT) on cancer cells. For the first time, it was possible to observe differences in cellular respiration at the transition between treated and untreated tumor cells in the same culture. Therewith more realistic in vitro studies of treatment efficiency and edge effects during PDT are possible. This resembles the spatially limited exposure in the in vivo situation. The sensor platform comprises an optically transparent microsensor chip with an integrated array of electrochemical oxygen microsensors and a LED light source for the photodynamic treatment.
Ates H, Schneider N, Bruch R, Weber W, Urban G, Dincer C
Antibody-free Assay for Electrochemical ß-lactam Monitoring
2019 MicroTAS 2019, Basel, Switzerland
KurzfassungIn this work, an antibody-free on-chip assay is introduced for electrochemical monitoring ß-lactam levels in untreated human plasma samples, using a microfluidic polymer-based biosensor. This is achieved by re-designing the penicillin-binding protein 3 production methodology and utilizing casein, instead of bovine serum albumin, as surface blocker. The applicability of the on-chip assay is successfully demonstrated by on-chip calibration of piperacillin (a commonly prescribed ß-lactam) in human plasma, resulting a limit of detection of 440 pg ml⁻¹ along with a broad dynamic range up to 100 μg ml⁻¹ and an inter-assay coefficient of variation below 13%.
Weltin A, Ganatra D, Durisin M, Urban G, Kieninger J
Electrochemical Protocols Upgrade Conventional Noble Metal Electrodes to Long-term Stable Sensors at the Tissue/Electrode Interface
2019 IEEE EMBC, Berlin, Germany Proc. 41th Int. Conf. of the IEEE Eng. in Medicine and Biology Soc. (EMBC), Band: 1, Seiten: 1 - 1
Pfau J, Ganatra D, Weltin A, Urban G, Kieninger J, Stieglitz T
Electrochemical Stability of Thin-Film Platinum as Suitable Material for Neural Stimulation Electrodes
2019 IEEE EMBC, Berlin, Germany
Bruch R, Baaske J, Chatelle C, Weber W, Dincer C, Urban G
Electrochemical biosensor for CRISPR/Cas13a powered miRNA diagnostics
2019 IEEE SENSORS 2019, Montreal, Canada
KurzfassungNon-coding small RNAs, such as microRNAs, are becoming the biomarkers of choice for multiple diseases in clinical diagnostics. A dysregulation of these microRNAs can be associated to many different diseases, such as cancer, dementia or cardiovascular conditions. The key issue for an effective treatment is an accurate initial diagnosis at an early stage, improving the patient’s survival chances. Here, we introduce a CRISPR/Cas13a based microfluidic, electrochemical biosensor for the on-site detection of microRNAs. Through this unique combination, the quantification of the tumor marker microRNA miR-19b has been achieved without any nucleic acid amplification with a limit of detection of 10 pM and a signal readout time of less than 10 min.
Farahani H, Wagiran R, Urban G
Perovskites As Surface-Assisted Room Temperature Protonic Conductor Humidity Sensor
2019 IEEE SENSORS 2019, Montreal, Canada
KurzfassungThis paper shows a correlation between surface effective porosity due to various sintering regimes and humidity sensitive electrical properties of the perovskite-based bulk type humidity sensors. Furthermore, room temperature humidity transduction mechanism of the thick film type humidity sensors was studied in details through electrochemical impedance spectroscopy (EIS) and major transmissive components were detected by fitting to the equivalent circuits. The materials were synthesized employing solid state reaction and bulk and film type devices were fabricated by hydraulic pressing and screen printing techniques, respectively. The morphological and elemental characterizations were carried on using FESEM, EFTEM, and EDX. Physical properties including open porosity/bulk density were investigated through ASTM methods. An innovative self-designed material test fixture with ceramic supports was fabricated for high S/N ratio electrical measurement of the bulk samples. All the sensors were set up at 20-95% RH. The morphological, physical, and electrical results of bulk pellets indicate direct correlation of the open cavities and AC conduction. Presence of the ionic transport is clearly observed from the frequency-conductance spectra at room temperature. Noise-free detected behavior via EIS proves that proton transfer mechanism is a dominant responsible.
Schössler T, Schön F, Lemier C, Urban G
Wafer level approach for the investigation of the long-term stability of resistive platinum devices at elevated temperatures
2019 IEEE International Reliability Physics Symposium (IRPS), Monterey, USA
KurzfassungIn this work, we present a new wafer level based approach to evaluate the long-term stability of thin film platinum resistors. This approach enables on the one hand the evaluation of hundreds of devices manufactured with the same processes parameters and exposed to the same stress conditions. Thus, statistical relevant conclusions can be drawn with respect to drift levels in the sub-percent range. On the other hand, the drift pattern on the wafer gives hints to the cause of drift. First investigations with this new approach show a significant influence of the silicon oxide stoichiometry of silicon-rich oxide cover layers on platinum resistors at stress temperatures of only 140°C to 250°C.

2018

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Wieland T, Behrmann O, Bergmann M, Reyes-Romero D, Hügle M, Dame G, Urban G
Application of a real-time thermal sensor system for the evaluation of anti-microbial surface coatings
2018 Biosensors 2016, Göteborg, Schweden Proceedings
Wieland T, Kotthaus K, Hügle M, Bergmann M, Urban G
Application of a thermal sensor system for the measurement and characterization of biofilm formation removal by the disinfectants ethanol, peracetic and sodium hypochlorite in real-time
2018 MicroTAS 2018, Kaohsiung, Taiwan
Wieland T, Assmann J, Hügle M, Behrmann O, Dame G, Tadros M, Urban G
Application of a thermal sensor system for the measurement in real-time of the inhibition of biofilm formation by anti-microbial peptides
2018 Biosensors 2018, Miami, USA Proceedings
Farahani H, Wagiran R, Yurchenko O, Urban G
Barium Strontium Titanate Humidity Sensor: Impact of Doping on the Structural and Electrical Properties
2018 Eurosensors 2018, Graz, Austria Proceedings, Band: 2, Seite: 1007
KurzfassungThe influence of Mg²⁺ doping (3 mol %) on structural and humidity sensing properties of (Ba₀.₅,Sr₀.₅)TiO₃ (BST) perovskite nanocomposite were studied in details. Microstructural properties revealed the particle size, surface area, and average pore volume diminished for doped sample. For the MgO doped BST sensor, the film resistance and total impedance are changed more than four orders of magnitude in the 20–95% RH range, while BST sensor shows three orders change. The 3 mol % MgO doped sample with maximum hysteresis of 6.1 RH% and response/recovery time of about 30/80 s exhibits faster characteristics compare to pure BST sample with 6.8 RH% hysteresis and response/recovery of 41 s and 98 s, respectively. Transduction mechanism was found based on the proton transfer and further confirmed by a Bode plot and Nyquist complex impedance plane plot.
Pfau J, Ganatra D, Weltin A, Urban G, Kieninger J, Stieglitz T
Electrochemical Stability of Thin-Film Platinum as Suitable Material for Neural Stimulation Electrodes
2018 BMT 2018, Aachen, Germany Biomed Eng-biomed Te, Band: 63, Ergänzungsband: 1, Seite: S121
Urban G, Dincer C, Weltin A, Prenzler N, Schmitt H, Warnecke A, Falk C, Lenarz T
In-vitro and in-vivo sensors for monitoring neuronal restauration
2018 BMT 2018, Aachen, Germany Biomed Eng-biomed Te, Band: 63, Ergänzungsband: 1, Seite: S141
Kutluk H, Bruch R, Meirich M, Partel S, Urban G, Dincer C
Microfluidic biosensor for the electrochemical on-site detection of microRNAs
2018 MicroTAS 2018, Kaohsiung, Taiwan
KurzfassungIn this work we present a novel approach for the electrochemical detection of miRNAs using a microfluidic platform. Herein, a sensitive, versatile and low-cost biosensor is combined with an enzyme-linked assay to detect miRNAs via hybridization in very low sample volumes (560 nl). The applicability of the system is successfully shown by measuring the miRNA hsa-miR-197 with a limit of detection (LOD) of 6.4 nM and an inter-assay coefficient of variation of below 10%. It is shown that the microfluidic biosensor is capable of measuring low miRNA concentrations with high selectivity against non-targeted miRNAs.
Grether E, Bruch R, Kutluk H, Moser I, Jobst G, Goymann W, Gahr M, Urban G, Dincer C
On-site hormone monitoring using an electrochemical microfluidic biosensor for lab-on-a-bird applications
2018 MicroTAS 2018, Kaohsiung, Taiwan
KurzfassungIn this work, we introduce a microfluidic electrochemical platform to measure hormone levels of birds on-site. Herein, a low-cost and easy-to-handle biosensor is combined with a single-step competitive enzyme linked immunoassay. It enables to work with very low sample volumes (less than 600 nanoliters) along with a short sample-to-result time (about one hour). The feasibility of the system for future lab-on-a-bird applications is successfully demonstrated by measuring different testosterone concentrations in whole blood samples of zebra finches, reproducibly.

2017

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Urban S, Weltin A, Flamm H, Kieninger J, Deschner B J, Kraut M, Dittmeyer R, Urban G
Electrochemical Multisensor System for Monitoring the Hydrogen Peroxide Direct Synthesis in Microreactors
2017 Eurosensors 2017 Conference, Paris, France Proceedings, Band: 1, Nummer: 4, Seite: 630
KurzfassungWe present an electrochemical sensor system for the detection of hydrogen peroxide inside a direct synthesis microreactor. The setup allows the online, in situ measurement of high reactant concentrations by amperometric detection across the micro channel width and length. The robust integration of the electrochemical cell in the microreactor was demonstrated. Hydrogen peroxide was detected under reaction conditions (pH 3–4, presence of bromide) showing linear behaviour up to 2 mM with high sensitivity and excellent stability. The linear range was increased up to 10 mM by applying a diffusion limiting pHEMA layer to the electrode surface.

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Weltin A, Kieninger J, Urban G
Highly Sensitive Electrochemical Glutamate Microsensors for Food Analysis
2017 Eurosensors 2017 Conference, Paris, France Proceedings, Band: 1, Nummer: 4, Seite: 521
KurzfassungElectrochemical microsensors are ideal to measure substances with low concentration in complex environments. The primary excitatory neurotransmitter l-glutamate is present in many foods as a distinctive flavour (enhancer) with a wide concentration range. In comparison to other methods, electrochemical sensors allow the rapid, precise, cost-effective, online measurement without any sample treatment. We developed a disposable electrochemical microsensor platform with multiple integrated, highly sensitive (detection limit <150 nM) and selective enzyme-based glutamate biosensors. We showed both the precise determination of glutamate levels in processed foods with high glutamate content (15–40 mM), e.g., broth, and in foods with low natural concentrations such as different types of cow’s milk (~250 μM). Hereby, we successfully demonstrated the capabilities of electrochemical biosensors in food monitoring, analysis and quality control.

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Rietzel R, Hügle M, Dame G, Behrmann O, Urban G
In-Situ Electrophoretic Mobility Determination by Particle Image Velocimetry for Efficient Microfluidic Enrichment of Bacteria
2017 Eurosensors 2017 Conference, Paris, France Proceedings, Band: 1, Nummer: 4, Seite: 535
KurzfassungWe present a novel approach for the efficiency enhancement of microfluidic bacteria enrichment systems based on free-flow electrophoresis (FFE). FFE efficiency is highly dependent on the electrophoretic mobility μ of the bacteria. As μ varies strongly with the suspension medium, fast and accurate determination of μ is needed to achieve optimal enrichment performance from different suspension media. For the first time, μ is determined in-situ for multiple media during on-chip FFE by Particle Image Velocimetry (PIV) of fluorescent bacteria, obviating the need for separate measurement equipment or chemical staining of the bacteria.

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Weltin A, Joseph K, Kieninger J, Hofmann UG, Urban G
Investigation of electrical stimulation by glutamate sensing from brain slices with microsensors
2017 MicroTAS 2017, Savannah, USA 21st International Conference on Miniaturized Systems for Chemistry and Life Sciences, Seiten: 1563 - 1564
Farahani H, Wagiran R, Urban G
MgO-Doped (Zr,Sr)TiO₃ Perovskite Humidity Sensors: Microstructural Effects on Water Permeation
2017 Eurosensors 2017 Conference, Paris, France Proceedings, Band: 1, Nummer: 4, Seite: 408
KurzfassungPorous (Zr₀.₅,Sr₀.₅)TiO₃ and MgO (1, 3, 5 mol%) doped ZST nanocomposites have been developed and investigated as humidity sensing elements. The surface area analyser and FESEM data have indicated that the MgO doped perovskites are contained of the macropores and grain size of about 77 to 87 nm. EFTEM proved the reduction of particle size by addition of MgO dopant concentration. While pure ZST shows BET surface area of about 58 m²/g, MgO doped samples exhibit about 12 m²/g. Sensor contained of ZST doped with 3 mol% MgO shows highest sensitivity with about four orders of magnitude change in impedance within the range of 20% to 95% RH.

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Marzioch J, Kramer F, Dungel P, Kieninger J, Urban G
Pericellular Oxygen Monitoring during Low-Level Light Therapy in Cell Culture Using a Microsensor System
2017 Eurosensors 2017 Conference, Paris, France Proceedings, Band: 1, Nummer: 4, Seite: 499
KurzfassungAn electrochemical microsensor system to monitor the pericellular oxygen concentration of fibroblasts during low-level light therapy in vitro was developed. The system provides in-sight into the metabolism of the cells during and in consequence of illumination with visible red light. This approach is a unique method for real-time investigations of cellular respiration during light therapy. The presented sensor system features direct amperometric measurements by using chronoamperometric protocols for long-term stability. The oxygen measurements do not show a disturbance by light.

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Bruch R, Chatelle C, Kling A, Dincer C, Wirth S, Schumann S, Weber W, Urban G
Therapeutic Drug Monitoring for a Personalized Antibiotherapy
2017 MicroTAS 2017, Savanna, USA
KurzfassungFor the therapeutic drug monitoring (TDM) of β-lactam antibiotics at the patient's bedside, a novel approach of an electrochemical, microfluidic platform is presented. Herein, a highly sensitive, low-cost and versatile biosensor is combined with an enzyme linked assay (ELA), using the penicillin binding protein 3 (PBP-3) for a fast and facile detection of ß-lactams (less than 1 hour) from very low sample volumes (580 nl). The system applicability is successfully demonstrated by monitoring the antibiotic blood concentration of patients, receiving antibiotherapy (cefuroxime and cefazolin), while undergoing surgery.
Kieninger J, Liebisch F, Weltin A, Marzioch J, Urban G
Zero consumption Clark-type oxygen microsensor for cell culture monitoring
2017 Transducers 2017, Kaohsiung, Taiwan

2016

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Lackner E, Krainer J, Wimmer-Teubenbacher R, Sosada F, Deluca M, Koeck A, Laubender E, Yurchenko O, Urban G, Bekacz J, Rohracher K, Wachmann E
CMOS integrated tin dioxide gas sensors functionalized with bimetallic nanoparticles for improved carbon monoxide detection
2016 IEEE SENSORS 2016, Orlando, FL, USA IEEE SENSORS, Seiten: 1 - 3
KurzfassungIn this work, we present the integration of functionalized tin dioxide gas sensors on CMOS fabricated microhotplate chips. Spray pyrolysis was used to deposit the gas sensitive films, with a thickness of 50 nm, on CMOS microhotplates. The SnO₂ thin films were functionalized with noble bimetallic nanoparticles — PdAu — by inkjet printing and the influence of the nanoparticles on the sensor performance was evaluated. The functionalization of the CMOS integrated SnO₂ sensors with PdAu nanoparticles lead to an almost three times higher sensor response towards carbon monoxide compared to the bare SnO₂ thin film. The CMOS microhotplate chips are also applicable for 3D-integration of different gas sensing systems based on through-silicon-via technology. Building devices for daily life applications is possible with such 3D-integrated nanosensors.
Laubender E, Tanvir N, Urban G, Yurchenko O
Ceria-zirconia Mixed Oxide Prepared through a Microwave-assisted Synthesis for CO2 Sensing in Low Power Work Function Sensors
2016 Advances in Functional Materials Conference 2015 Materials Today: Proceedings, Band: 3, Nummer: 2, Seiten: 429 - 433
KurzfassungIn this work the sensitivity towards CO₂ of pure ceria, zirconia and a Ce-Zr mixed oxide were tested in a Kelvin Probe setup. The nanocrystalline powders were obtained by microwave-assisted synthesis. A high work function response in humid air was observed for all compositions, the mixed oxide exhibiting the best sensing characteristics. Based on the results presented here, we propose nanocrystalline Ce0.8Zr0.2O2 as a CO₂ sensitive layer for work function based gas sensors.
Bruch R, Chatelle C, Kling A, Dincer C, Weber W, Urban G
Electrochemical mcrofluidic biosensor for the protein-based quantification of ß-lactams
2016 MicroTAS 2016, Dublin, Ireland
KurzfassungIn this work, we present a novel approach for the point-of-care testing (POCT) of β-lactam antibiotics on a miniaturized electrochemical microfluidic platform. Herein, a highly sensitive, low- cost and versatile biosensor is combined with an enzyme linked assay (ELA) using the penicillin binding protein 3 (PBP-3) for the fast and facile detection of ß-lactams from very low sample volumes (580 nl). The demonstration of the system applicability is successfully shown by measuring different piperacillin concentrations in spiked human blood plasma with an inter-assay coefficient of variation (CV) below 15 % and a limit of detection (LOD) of 8.34 ng ml⁻¹.
Marzioch J, Kieninger J, Sandvik J A, Pettersen E A, Peng Q, Urban G
Electrochemical microsensor system for cancer research on photodynamic therapy in vitro
2016 27th Micromechanics and Microsystems Europe (MME) workshop, Cork, Irland Journal of Physics: Conference Series, Band: 757
KurzfassungAn electrochemical microsensor system to investigate photodynamic therapy of cancer cells in vitro was developed and applied to monitor the cellular respiration during and after photodynamic therapy. The redox activity and therefore influence of the photodynamic drug on the sensor performance was investigated by electrochemical characterization. It was shown, that appropriate operation conditions avoid cross-sensitivity of the sensors to the drug itself. The presented system features a cell culture chamber equipped with microsensors and a laser source to photodynamically treat the cells while simultaneous monitoring of metabolic parameter in situ. Additionally, the optical setup allows to read back fluorescence signals from the photosensitizer itself or other marker molecules parallel to the microsensor readings.
Partel S, Urban G
Innovative method to suppress local geometry distortions for fabrication of interdigitated electrode arrays with nano gaps
2016 Optical Microlithography XXIX, California, United States SPIE Proceedings, Band: 9780
KurzfassungIn this paper we present a method to optimize the lithography process for the fabrication of interdigitated electrode arrays (IDA) for a lift-off free electrochemical biosensor. The biosensor is based on amperometric method to allow a signal amplification by redox cycling. We already demonstrated a method to fabricate IDAs with nano gaps with conventional mask aligner lithography and two subsequent deposition processes. By decreasing the distance down to the nanometer range the linewidth variation is becoming the most critical factor and can result in a short circuit of the electrodes. Therefore, the light propagation and the resist pattern of the mask aligner lithography process are simulated to optimize the lithography process. To optimize the outer finger structure assistant features (AsFe) were introduced. The AsFe allow an optimization of the intensity distribution at the electrode fingers. Hence, the periodicity is expanded and the outer structure of the IDA is practically a part of the periodic array. The better CD uniformity can be obtained by adding three assistant features which generate an equal intensity distributions for the complete finger pattern. Considering a mask optimization of the outer structures would also be feasible. However, due to the strong impact of the gap between mask and wafer at contact lithography it is not practicable. The better choice is to create the same intensity distribution for all finger structures. With the introduction of the assistant features large areas with electrode gap sizes in the sub 100 nm region are demonstrated.
Zhu YQ, Hepp CJ, Urban G
Modelling and Simulation of a Thermal Flow Sensor for Determining the Flow Speed and Thermal Properties of Binary Gas Mixtures
2016 Eurosensors 2016, Budapest, Hungary Procedia Engineering, Band: 168, Seiten: 1028 - 1031
KurzfassungA thermal flow sensor has been reported to measure simultaneously the thermal conductivity and flow speed of binary gas mixtures. It features low power consumption and a simple geometry. In this work, by means of 3D modelling and numerical simulations it is shown that the volumetric heat capacity of gas mixtures can also be detected by evaluating the heater's temperature of the sensor under flowing conditions. As a result, for those binary gas mixtures with similar thermal conductivity but different volumetric heat capacity, such as CO2-Ar, the gas concentration can also be determined with a high accuracy.
Tanvir N, Laubender E, Yurchenko O, Urban G
Room Temperature CO Sensing with Metal Oxide Nanoparticles Using work Function Readout
2016 Eurosensors 2016, Budapest, Hungary Procedia Engineering, Band: 168, Seiten: 284 - 288
KurzfassungIn this work a comparative study of work function readout based CO gas sensing using metal oxide nanoparticles at room temperature is presented. The gas sensing measurements were recorded with the help of Kelvin probe that can measure the change in work function of the sensitive layers when exposed to CO. We detected the enhancement in the CO gas sensing properties of n-type nanocrystalline CeO₂ by the introduction of p-type CuO nanoparticles at room temperature. Moreover the inclusion of temperature (T = 100̊C), induced a relatively negative impact in the gas sensing properties of the investigated nanoparticles. The combination of n- and p- type mixed metal oxides has a huge potential to obtain relatively stable gas sensitive layers that can be successfully implied towards low power consuming CO gas sensors.
Bergmann M, Urban G
Tailored Protein Adsorption on Biocompatible Plasma Nanofilms
2016 BMT 2016, Basel, Switzerland Biomed Eng-biomed Te, Band: 61, Seite: S1

2015

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Jachowicz R, Tarapata G, Paczesny D, Urban G, Bergmann M
Influence of the Top Dielectric Layer on Interdigitated Capacitive Dew Point Detector Operation
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 1120 - 1123
Flamm H, Kieninger J, Weltin A, Urban G
Advanced Electrochemical in Vitro Detection of Superoxide Radicals with Fully Integrated Microsensor System
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 26 - 30
Nguyen A, Tran D, Pliquett U, Urban G
Behavior and the Response of Cancer Cells on Anticancer Drug Treatment Monitored with Microelectrode Array
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 928 - 931
Dame G, Lampe J, Hakenberg S, Urban G
Development of a Fast miRNA Extraction System for Tumor Analysis Based on a Simple Lab on Chip Approach
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 158 - 162
Hajian A, Ghodsi J, Afraz A, Rafati A, Shoja Y, Yurchenko O, Urban G
Development of a Novel Biosensor for Nanomolar Detection of Methylparaben
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 552 - 555
KurzfassungThis work describes the development of a new biosensor for methylparaben determination using electrocatalytic properties of haemoglobin in presence of hydrogen peroxide. The biosensor was fabricated by carbon paste electrode modified with haemoglobin and multiwalled carbon nanotube. Based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for determination of methylparaben within a liner range from 1 to 13 μM and detection limit of 25 nM. The prepared biosensor possessed accurate and rapid response to methylparaben and good sensitivity, stability and repeatability.
Kling A, Dincer C, Armbrecht L, Horak J, Kieninger J, Urban G
Electrochemical Microfluidic Platform for Simultaneous Multi-Analyte Detection
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 916 - 919
KurzfassungWe present an electrochemical lab-on-a-chip (LOC) platform for the simultaneous detection of up to four different analytes. The possibility to separately immobilize different assays in a channel network, without active valves, was successfully demonstrated using a model assay linked to glucose oxidase. This enables the detection of various analytes even with different assay formats. For the assay immobilization, the channel surface, made out of dry film photoresist (DFR), could be activated by means of EDC/NHS-linker chemistry and used for the covalent binding of primary amines. Cross-sensitivity due to diffusion within the channel network could be experimentally excluded.
Hepp C, Krogmann F, Urban G
Gas Concentration and Flow Speed Measurement by Thermal Excitation using one Single Chip, Procedia Engineering
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 298 - 301
Hammer S, Weltin A, Kaminski Y, Noor F, Kieninger J, Urban G
Lactate Monitoring in Organotypic 3D Cell Cultures
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 961 - 964
Laubender E, Tanvir N, Yurchenko O, Urban G
Nanocrystalline CeO2 as Room Temperature Sensing Material for CO2 in Low Power Work Function Sensors
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 1058 - 1062
Tanvir N, Yurchenko O, Urban G
Optimization Study for Work Function Based CO2 Sensing Using CuO-nanoparticles in Respect to Humidity and Temperature
2015 Eurosensors, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 667 - 670
KurzfassungThe detection of CO2, based on metal oxide nanoparticles has a lot of potential due to their higher surface area and easy implementation in microsystem devices. In this work, we investigated semiconducting copper oxide nanoparticles (CuO-NPs) with respect to different conditions affecting the stability and sensitivity of the CO2 response. The adsorption induced changes have been recorded through work function (WF) based alterations using Kelvin probe measurements. It is shown that an optimized CO2-sensing behavior for CuO-NPs by using combined effect of humidity and temperature is achievable and can play a pivotal role towards the development of low cost CO2 gas sensors.
Marzioch J, Kieninger J, Sandvik J, Pettersen E, Peng Q, Urban G
Photodynamic Therapy – In Vitro Investigation Using an Electrochemical Microsensor System
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 468 - 471
Bergmann M, Ledernez L, Urban G
Plasma Nanofilms as Biocompatible and Antibacterial Interface for In-Vivo Sensors
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 45 - 48
Urban S, Unmüssig T, Daubinger P, Kieninger J, Urban G
Stability of Non-enzymatic Glucose Sensor Based on Platinum Micro-/Nanostructures
2015 Eurosensors 2015, Freiburg, Germany Procedia Engineering, Band: 120, Seiten: 1145 - 1148
Unmuessig T, Daubinger P, Kieninger J, Urban G
Hierarchical Platinum Nanostructure for the Non-Enzymatic Detection of Glucose by Amperometry and Impedance Analysis
2015 18th International Conference on Solid-State Sensors, Actuators and Microsystems; Anchorage, Alaska, USA Solid-State Sensors, Actuators and Microsystems, Band: M
Flamm H, Weltin A, Kieninger J, Urban G
Measurement of reactive oxygen species release from stimulated cell culture with fully integrated microsensor system by advanced electrochemical detection principle
2015 18th International Conference on Solid-State Sensors, Actuators and Microsystems; Anchorage, Alaska, USA Solid-State Sensors, Actuators and Microsystems, Band: M, Seiten: 1561 - 1564
Osorio-Madrazo A, Fratzl P, David L, Montembault A, Crepet A, Urban G, Gorzelanny C, Mochales-Palau C, Heux L, Viguier E, Cachon T, Peniche-Covas C, Sudre G, Politi Y
Cellulose nanofiber/ chitosan hydrogel nanocomposites: Preparation and characterization of the structural and mechanical properties
2015 12th International Conference of the European Chitin Society EUCHIS 2015; 13th International Conference on Chitin and Chitosan I.C.C.C. 2015
Osorio-Madrazo A, David L, Peniche-Covas C, Rochas C, Putaux J-L, Trombotto S, Alcouffe P, Domard A
Chitosan Nanofibril Networks Preserving Native Directional Packing. Fine Microstructure Characterization
2015 12th International Conference of the European Chitin Society EUCHIS 2015; 13th International Conference on Chitin and Chitosan I.C.C.C. 2015
Peniche-Aguero H, Osorio-Madrazo A, Acosta-Contreras N, Peniche-Covas C
Chitosan based superparamagnetic microparticles for enzyme immobilization
2015 12th International Conference of the European Chitin Society EUCHIS 2015; 13th International Conference on Chitin and Chitosan I.C.C.C. 2015
Osorio-Madrazo A, David L, Peniche-Covas C, Rochas C, Putaux JL, Trombotto S, Alcouffe P, Domard A
Fine microstructure of processed chitosan nanofibril networks preserving directional packing and high molecular weight
2015 Carbohyd Polym, Band: 131, Seiten: 1 - 8
KurzfassungCrystalline chitosan nanofibril networks were prepared, preserving the native structural packing and the polymer high molecular weight. The fine microstructure of the nanomaterial, obtained by mild hydrolysis of chitosan (CHI), was characterized by using synchrotron small- and wide-angle X-ray scattering (SAXS and WAXS), transmission electron microscopy (TEM) and electron diffraction. Hydrolysis of chitosan yielded a network of crystalline nanofibrils, containing both allomorphs of chitosan: hydrated and anhydrous. The comparison of WAXS data in transmission and reflection mode revealed the preferential orientation of the CHI crystals when subjected to mechanical compression constrains. The results are in agreement with the existence of a network nanostructure containing fiber-like crystals with the principal axis parallel to the polymer chain axis. The evolution of the CHI allomorphic composition with temperature was studied to further elucidate the mechanism of structural transitions occurring during CHI nanofibril network processing.
Osorio-Madrazo A, Fratzl P, David L, Urban G, Montembault A, Crepet A, Gorzelanny C, Mochales-Palau C, Heux L, Putaux J-L, Cachon T, Viguier E, Peniche C, Sudre G, Politi Y
Hydrogel nanocomposite biomaterials for intervertebral disc tissue engineering. Preparation, characterization and application
2015 Jahrestagung der Deutschen Gesellschaft für Biomaterialien DGBM Bionanomaterials, Band: 16, Nummer: 2-3
KurzfassungIntervertebral disc (IVD) degeneration is thought to be the primary cause of low back pain (LBP). When treating disc herniation due to degeneration, the ‘gold standard’ consists in IVD excision and fusion of the adjacent vertebral bodies, which often results in degeneration of adjacent discs. Even if disc replacement strategies are available, the surgery is very traumatic and the prosthesis wears with time. Although the IVD has a poor repair capacity, minor self-repair processes are observed. Thus, different approaches aim to regenerate the IVD by means of biomaterials. IVD tissue engineering has focused on using biodegradable polymer biomaterials. Several natural polymers have been used to design scaffolds as provisional support for tissue regeneration. To get advantage of the observed properties of hydrogel materials in nature, we developed biopolymer-based hydrogel nanocomposites for application in IVD regeneration/ repair. The hydrogel nanocomposites were implanted in vitro into defects of growing-pig model discs and the hydrogel-implanted tissue showed mechanical performance as demanded by the native complex IVD tissue. It was investigated the relationship biomaterial physicochemical structure-biomechanics-biological properties.
Kling A, Dincer C, Armbrecht L, Horak J, Kieninger J, Urban G
Microfluidic multiplexed multi-analyte immunosensing platform
2015 MicroTAS 2015, Gyeongju, Korea
Chatelle C, Kling A, Dincer C, Urban G, Weber W
Microfluidic quantification of antibiotics by synthetic biology-derived biosensors
2015 Engineering life 2015, Dresden, Germany
Toeri J R, Osorio-Madrazo A, Laborie M-P
New chitosan-azacrown ether films for bioremediation: Preparation and thermomechanical properties
2015 12th International Conference of the European Chitin Society EUCHIS 2015; 13th International Conference on Chitin and Chitosan I.C.C.C. 2015
Osorio-Madrazo A, Fratzl P, Peniche-Covas C, David L, Ramirez-Arrebato M A, Samyn P, Sudre G, Politi Y
Physico-chemistry and material physics of chitin sources in nature. Microstructure, biomechanics and composition of the cuticle of Caribbean lobster Panulirus argus
2015 12th International Conference of the European Chitin Society EUCHIS 2015; 13th International Conference on Chitin and Chitosan I.C.C.C. 2015
Torres-Ramos M E W, Sereni N, David L, Montembault A, Crepet A, Taheri H, Samyn P, Heux L, Osorio-Madrazo A
Rheological behavior studies of chitosan/cellulose nanofibers injectable formulations in hydroalcoholic and aqueous media
2015 12th International Conference of the European Chitin Society EUCHIS 2015; 13th International Conference on Chitin and Chitosan I.C.C.C. 2015
Armbrecht L, Dincer C, Kling A, Horak J, Kieninger J, Urban G
Signal amplification using magnetic bead chains in microfluidic electrochemical biosensors
2015 Transducers 2015, Alaska, USA

2014

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Lehmann K, Yurchenko O, Urban G
Carbon Nanowalls for Oxygen Reduction Reaction in Bio Fuel Cells
2014 PowerMEMS 2014, Japan Journal of Physics: Conference Series, IOP Publishing, Band: 012008, Nummer: 557
Qazzazie D, Beckert M, Muelhaupt R, Yurchenko O, Urban G
Modified Graphene as Electrocatalyst towards Oxygen Reduction Reaction for Fuel Cells
2014 PowerMEMS 2014, Japan Journal of Physics: Conference Series, IOP Publishing, Band: 012009, Nummer: 557
Mutinati G, Brunet E, Yurchenko O, Laubender E, Urban G, Koeck A, Steinhauer S, Siegert J, Rohracher K, Schrank F
Bimetallic Nanoparticles For Optimizing CMOS Integrated SnO2 Gas Sensor Devices
2014 Solid State Device Research Conference (ESSDERC), Venice, Italy Solid State Device Research Conference, IEEE, Band: 1, Seiten: 78 - 81
Beigelbeck R, Reyes D, Cerimovic S, Kohl F, Voglhuber-Brunnmaier T, Jakoby B, Urban G
Frequency Domain Based Measurement Method for the Thermal Parameters of a Thin-film Diaphragm Embedded in a MEMS Multi-parameter Wind Sensor
2014 Eurosensors 2014 Procedia Engineering, Band: 87, Nummer: 632, Ergänzungsband: 635
Pentyala V, Davydovskaya P, Pohle R, Urban G, Yurchenko O
Mg-MOF74 and Co-MOF74 as Sensing Layers for CO2 Detection
2014 EUROSENSORS 2014, Brescia, Italy Procedia Engineering, Elsevier, Band: 87, Seiten: 1071 - 1074
KurzfassungMg-MOF74 is known as one of the best Metal-Organic Frameworks (MOFs) materials for CO2 adsorption and separation due to strong interactions of their unsaturated metal sites with CO2. In this work, Mg- and Co-MOF74 were investigated for the first time with respect to CO2 sensing and the possible gas interactions with MOFs were discussed. Furthermore, the cross sensitivity to ethanol and acetone was tested. The different sensing behavior towards CO2 and ethanol was observed allowing the differentiation of these gases.
Mutinati G, Brunet E, Koeck A, Steinhauer S, Yurchenko O, Laubender E, Urban G, Siegert J, Rohracher K, Schrank F, Schrems M
Optimization of CMOS Integrated Nanocrystalline SnO2 Gas Sensor Devices with Bimetallic Nanoparticles
2014 Eurosensors 2014 Procedia Engineering, Band: 87, Seiten: 787 - 790
Marzioch J, Kieninger J, Aravindalochanan K, Sandvik J, Pettersen E, Urban G
Microsensor System for Cancer Research on Photodynamic Therapy
2014 Biosensors, Melbourne, Australia
Horak J, Dincer C, Bakirci H, Urban G
An integrated dry film resist-based immunosensor for rapid electrochemical detection of Epstein-Barr virus infection
2014 Biosensors, Melbourne, Australia
Osorio-Madrazo A, Politi Y, Burgert I, Montembault A, David L, Nishiyama Y, Putaux J-L, Rochas C, Pillet E, Roger T, Peniche C, Ramírez M A, Gorzelanny C, Mochales-Palau C, Heux L, Eder M, Rüggeberg M, Crépet A, Fratzl P, Urban G
Bioinspired approach for the development of bioactive composites for tissue engineering
2014 Trilateral Symposium Architectured Biomaterials, Medical and Tissue Engineering, Berlin
Dincer C, Ktaich R, Laubender E, Hees J, Heinze J, Nebel C E, Urban G
Boron doped diamond nanoelectrode arrays as dopamine sensor
2014 Biosensors, Melbourne, Australia
Dincer C, Ktaich R, Laubender E, Hees J, Heinze J, Nebel C E, Urban G
Boron doped diamond nanoelectrode arrays as dopamine sensor
2014 International Conference on Diamond and Carbon Materials, Madrid, Spain
Partel S, Kasemann S, Choleva P, Dincer C, Kieninger J, Urban G
Novel fabrication process for sub-µm interdigitated electrode arrays for highly sensitive electrochemical detection
2014 Biosensors, Melbourne, Australia
Tanvir N, Wilbertz C, Steinhauer S, Köck A, Urban G, Yurchenko O
Work Function Based CO2 Gas Sensing Using Metal Oxide Nanoparticles at Room Temperature
2014 nanoFIS 2014 - Functional Integrated nanoSystems Materials Today: Proceedings, Band: 2, Nummer: 8, Seiten: 4190 - 4195

2013

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Erhardt J, Nock V, Kieninger J, Urban G
Non-invasive characterization of dissolved oxygen dynamics in water-in-oil droplet microfluidics - Towards 3d micro tumor spheroids for high throughput cancer drug screening.
2013 17th International Conference on Miniaturized Systems for Chemistry and Life Sciences (MicroTAS 2013), Freiburg, Germany , Seiten: 1376 - 1378
Pentyala V, Davydovskaya P, Pohle R, Urban G
Work Function Based Gas Sensing with Luminescent Metal-Organic Frameworks
2013 3rd International Conference on Materials and Application for Sensors and Transducer. Prag, Czech Republic
Davydovskaya P, Pentyala V, Hussein L, Pohle R, Urban G
Work Function Based Gas Sensing with Benzene Tricarboxylate Linked Metal Organic Frameworks - a Comparison Study
2013 17th International Conference on Transducers & Eurosensors XXVII. Barcelona, Spain
Osterberg N, Aravindalochanan K, Kieninger J, Urban G, Weyerbrock A
Development and Evaluation of an Electrochemical Nitric Oxide Sensing On-Chip Cell Culture System for Measurement of Pericellular NO in Glioma Cell Cultures
2013 64. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Düsseldorf, Deutschland
O. Yurchenko, D. Xavier, S. Sushank, L. Hussein, F. Olcaytug, G. Urban
Study of the Inluence of the Morphologay of the Nanostructured Carbon on Performance of Supercapacitors
2013 2nd International Conference on Materials for Energy. Karlsruhe, Germany
Zeniieh D, Bajwa A, Olcaytug F, Urban G
Parylene-C Thin Film For Biocompatible Encapsulations With Very Strong Adhesion And Superior Barrier Properties
2013 ISPC-21, Cairns, Australia

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Dincer C, Laubender E, Urban G, Heinze J
SECM Detection of Single Boron Doped Diamond Nanodes and Nanoelectrode Arrays Using Phase-Operated Shear Force Technique
2013 7th SECM Workshop, Ein Geidi, Israel

2012

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Davydovskaya P, Hussein L, Yurchenko O, Pohle R, Urban G
Work Function Based Hydrocarbon-Mix Sensing with Nanoparticles Functionalized WO3 Thick Films
2012 Eurosensors 2012 , Band: 47, Seiten: 594 - 597
Reyes D, Urban G
Simulation of the Frequency Response of a Thermal Flow Sensor in Gaseous Media
2012 EuroSimE
Bakirci H, Dincer C, Horak J, Duchmann H, Sokolowski G, Urban G
A Electrochemical Micro-immunoassay for the Detection of Epstein-Barr Virus-Specific IgG Antibody
2012 Biosensors, Cancun, Mexico
Weltin A, Enderle B, Slotwinski K, Kieninger J, Urban G
A Flexible Multiparametric Microsensor for in-vivo Application
2012 Biosensor (Elsevier), Cancun, Mexico
Reyes D, Urban G
Amplitude and Phase Measurement of a Flow Sensor at High Frequency
2012 Eurosensors XXVI
Reyes D, Urban G
Amplitude and Phase Measurement of a Flow Sensor at High Frequency
2012 26th European Conference on Solid-State Transducers, EUROSENSOR 2012 Procedia Engineering, Band: 47, Seiten: 562 - 565
KurzfassungA flow sensor is being developed at IMTEK to simultaneously measure gas flow and its thermal properties. In this contribution, we show that at high frequency the amplitude and phase shift of the temperature oscillations remain constant for an air flow speed ranged from 0 to 3 m/s. Since amplitude and phase shift strongly depend on the gas properties, and flow can be extracted from the DC component of the temperature, then it is in principle possible to measure both simultaneously.
Kieninger J, Tamari Y, Enderle B, Sandvik J, Pettersen E, Urban G
Cell Culture Monitoring with Integrated Biosensors for Novel Insights into Metabolic Pathways in Tumor Cells
2012 Biosensor (Elsevier), Cancun, Mexico
Bakirci H, Horak J, Dincer C, Urban G
Enhanced Electrochemical Detection of Cardiac Troponin I with Polymer-Coated Capillary Microchip
2012 Biosensors, Cancun, Mexico
Flamm H, Aravindalochanan K, Kieninger J, Urban G
Enzyme-less Superoxide Sensor for Longtime Monitoring in Tumor Cell Culture
2012 Biosensor (Elsevier), Cancun, Mexico
Dincer C, Laubender E, Hees J, Heinze J, Nebel C E, Urban G
SECM Characterization of Single Boron Doped Diamond Nanodes for the Optimization of Electrochemical Biosensors
2012 Biosensors, Cancun, Mexico
Davydovskaya P, Hussein L, Yurchenko O, Pohle R, Urban G
Work Function Based Hydrocarbon-Mix Sensing with Nanoparticles Functionalized WO3 Thick Films
2012 26th European Conference on Solid-State Transducers, EUROSENSOR 2012 Procedia Engineering, Band: 47, Seiten: 594 - 597
KurzfassungIn this work the sensitivity of pure and metal nanoparticles functionalized WO3 thick films towards hydrocarbon-mix (HC-Mix) has been studied based on work function readout by means of Kelvin Probe technique. Measurements have been performed in synthetic air and dry nitrogen atmosphere in the temperature range between 25° and 200 °C. The strongest signals were achieved with PtPd-nanoparticles functionalized WO3 thick layers at 120-140 °C. The influence of oxygen on the sensing mechanism has been discussed.

2011

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G.B.Stevens, A.Zgaga-Griesz, D.A.Silver, G.A.Urban, M.Krueger
An Assay for Automated Rapid, Sensitive Detection of Clostridium botulinum Neurotoxin in the Field
2011 Medical Biodefence Conference 2011, 25-28 Oct 2011, Muniche, Germany, Poster presenetation, best poster award (2nd prize), Band: 5
Reyes D, Cubukcu A, Urban G
Towards a Medium-Independent Flow Sensor
2011 Nürnberg Proceedings SENSOR, Band: A3, Seiten: 73 - 77
Einwaechter S, Krueger M
A fully automated remote controllable microwave-based synthesis setup for colloidal nanoparticles with an integrated absorption and photoluminescence online analytics
2011 MRS Fall Meeting 2010 Boston , Band: 1284, Seiten: 109 - 114
KurzfassungWe present a fully automated microwave-based synthesis setup for colloidal nanoparticles. Integrated absorption and photoluminescence online analytics opens the possibility to monitor the growth of various nanoparticles at any stage of the reaction. Spectroscopic investigation within the first seconds of a reaction is accessible opening the possibility to detect potential critical size nuclei as a function of the reaction conditions. Beside the possibility to perform systematic mechanistic studies, this system allows a high degree of synthesis control leading to very good product reproducibility. In conjunction with an automated auto sampler unit systematic multiple reactions can be performed one after each other and compared. The setup is remote-controllable allowing worldwide online control accessibility over the synthesis setup including data processing, visualization and storage. The performance of the setup will be demonstrated by using the synthesis of CdSe nanocrystals as a model system and can be extended to the synthesis of various metallic and semiconducting nanoparticles.
Krueger M, Zhou Y, Eck M
Inorganic-organic thin hybrid films for applications in bulk-heterojunction solar cells
2011 ICAC-NM 2011 (International Confernce on Advances in Condensed & Nanomaterials, Chandighar, Punjab University, India Institute of Physics, Band: AIP Conf. Proc., Nummer: 1393, Seiten: 19 - 22
KurzfassungInorganic organic hybrid material composites materials based on semiconductor quantum dots are promising materials for the integration as photoactive layers into bulk-heterojunction solar cells [1-3] as well as energy conversion layers for dedicated light emission in LED applications [4]. Dedicated treatment of the quantum dot surface is needed for optimized utilization. Aspects of quantum dot synthesis [5], modification [2] and device integration [2, 3] are addressed and future perspectives are highlighted. [1] Y. Zhou, F.-S. Riehle, Y. Yuan, H.-F. Schleiermacher, M. Niggemann, G. A. Urban, M. Krüger, Appl. Phys. Lett., 96, 0133014 (2010). [2] Yunfei Zhou, Michael Eck, Michael Krüger, Energy Environ. Sci. 3, 1851-1864, (2010). [3] Y. Zhou et al. –submitted- [4] Y. Yuan et al. –submitted- [5] Ying Yuan, Frank-Stefan Riehle, Haoshuang Gu, Ralf Thomann, Gerald Urban, Michael Krüger J. Nanosci. Nanotechnol. 10,604 1-6045, (2010).
Schaedel M, Jeltsch K, Kiesow A, Zhou Y, Krueger M, Meerholz K
Modelling Volume Ratio, Gradient and Ligand Layer Thickness of Quantum Dot – Polymer Solar Cells
2011 5–9 September 2011, Hamburg, Germany , Seiten: 567 - 571
Ledernez L, Olcaytug F, Urban G
Paschen Curves and Film Growth Rates in Low Pressure Capacitively Coupled Magnetron Plasma Polymerization
2011 ISPC-20, Philadelphia, USA
Reyes D, Cubukcu A, Urban G
Utilizing Frequency Response for Medium-Independent Flow Sensing
2011 Eurosensors XXV Procedia Engineering, Band: 25, Seiten: 599 - 602

2010

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Kieninger J, Aravindalochanan K, Urban G, Sandvik J, Pettersen E, Jobst G
Monitoring of Peri-cellular Oxygen Levels in Tumor Cell Cultures by Amperometric Oxygen Sensor Array
2010 IEEE Sensors, Hawai, USA Ieee Sens J, Seiten: 1234 - 1237
Krueger M, Einwaechter S
A fully automated remote controllable microwave-based synthesis setup for colloidal nanoparticles with an integrated absorption and photoluminescence online analytics
2010 MRS Fall Meeting 2010, Boston, USA
KurzfassungWe present a fully automated microwave-based synthesis setup for colloidal nanoparticles. An integrated absorption and photoluminescence online analytics opens the possibility to monitor the growth of various nanoparticles at any stage of the reaction. Spectroscopic investigation within the first seconds of a reaction is accessible opening the possibility to detect potential critical size nuclei as a function of the reaction conditions. Beside the possibility to perform systematic mechanistic studies, this system allows a high degree of synthesis control leading to a very good product reproducibility. In conjunction with an automated autosampler unit systematic multiple reactions can be performed one after each other and compared. The setup is intended to be remote-controllable allowing worldwide online control accessibility over the synthesis setup including data processing, visualisation and storage. The performance of the setup will be demonstrated by using the synthesis of CdSe nanocrystals as a model system and will be extended to the synthesis of various metallic and semiconducting nanoparticles.
Albrecht B, Hautzinger D, Krueger M, Elwenspoek M, Mueller K, Korvink J
ADSORPTION STUDIES OF DNA ORIGAMI ON SILICON DIOXIDE
2010 MME 2010: 21st Workshop on Micromachining, Micromechanics and Microsystems, Enschede, Netherlands
Riehle F, Urban G, Krueger M
Are blue luminescent CdSe nanoclusters ultra-stable?
2010 NaNaX 4 – Nanoscience with Nanocrystals International Conference, April 11-15, 2010, Munich - Tutzing (Germany)
KurzfassungMolecular clusters of CdSe have been routinely synthesized in the beginning of this century and characterized by single crystal X-ray spectroscopy revealing an internal structure similar to the corresponding bulk fragments [1]. A core-cage structure for the (CdSe)33/34 clusters was proposed by Kasuya et al. and later verified by DFT calculations [2, 3]. Their superior stability was experimentally proven by e.g. mass spectroscopy [2]. Recently several groups reported the occurrence of bright band-gap luminescence in so-called magic-size clusters of CdSe [4, 5, 6]. Here we will present a detailed study of their stability based on optical, TEM and mass spectroscopic measurements. [1] Soloviev, V. N.; Eichhoefer, A.; Fenske, D.; Banin, U. J. Am. Chem. Soc. 2001, 123, 2354–2364. [2] Kasuya et al. Nat. Mater. 2004, 3, 99. [3] Botti, S.; Marques, M. A. L. Phys. Rev. B 2007, 75, 035311. [4] Kucur, E.; Ziegler, J.; Nann, T. Small 2008, 4 (7), 883–887. [5] Ouyang et at. J. Phys. Chem. C 2008, 112, 13805-13811. [6} Riehle et al. Nano Lett. 2009, 9 (2), 514-518
Dame G, Enderle B, Olcaytug F, Ledernez L, Yasuda H, Urban G
Biocompatible Sensor Coatings for Enzyme Based Biosensors by Means of Magnetron Enhanced Plasma-Polymerization
2010 44. DGBMT, Rostock, Germany
Krueger M, Urban G, Zhou Y
Bulk-Heterojuction Solar Cells Based on Nanocrystal-Polymer Hybrid Materials
2010 International Conference on Molecular Electronics, January 2010, Emmetten, Switzerland
KurzfassungOrganic solar cells have the promising advantages of low-cost and large-area fabrication on flexible substrates. State-of-the-art organic solar cells based on blends of conjugated polymers and fullerene derivatives achieve efficiencies up to 5-6%. Inorganic semiconductor nanocrystals (NCs) e.g. out of CdSe, with tunable bandgaps and high intrinsic carrier mobilities, can be incorporated into conjugated polymers e.g. poly(3-hexylthiophene) (P3HT) to form bulk-heterojunction hybrid solar cells (Fig.1 left). Based on a highly reproducible synthesis method for CdSe NCs leading to monodisperse NCs with excellent photophysical properties, solar cells based on bulk-heterojunction CdSe NCs/P3HT hybrid materials have been fabricated and characterized. Devices using spherical NCs capped with organic ligands exhibit power conversion efficiencies up to 2% and above under standard measurement condition Air Mass (AM) 1.5 global illumination, after applying a novel surface modification step (Fig.1 right). This is among the highest reported values for spherical CdSe quantum dots. Further investigations to improve the materials and device performance are currently in progress as well as the incorporation of NCs of different shapes and compositions.
Riehle F, Yuan Y, Thomann R, Krueger M
CdSe Nanocrystals Grown by Aggregation: Evidence for a New Shape Mechanism
2010 EMPA Students Symposium, EMPA Akademie, Dübendorf, Schweiz
KurzfassungControlling the size and shape of inorganic materials in the size regime of a few nanometers is one of the most challenging tasks in modern nanotechnology. In the case of CdSe nanocrystals (NCs) a fundamental discovery was made in Alivisatos’ lab, when certain impurities were found to catalyze the growth of wurtzite-type CdSe NCs along the c-axis resulting in elongated rod-like structures [1]. Since then different synthesis strategies have been developed leading to more sophisticated morphologies such as tetrapods and multipods, which have shown considerably better performance in e.g. photovoltaic devices compared to their spherical counterparts [2]. In the current models shape control takes place during the crystal growth and strongly depends on the ability of the ligands to bind preferably to certain crystal surfaces as well as on the active ‘’CdSe’’ monomer concentration [3]. In our experiments we found, that the decision about the shape of CdSe NCs is already made in the nucleation stage of their synthesis and we assume that ultra-small CdSe nanoclusters, which tend to aggregate due to their higher surface reactivity, act as nuclei for CdSe NCs [4]. At lower temperatures this aggregation process becomes dominant resulting in the growth of elongated CdSe nanostructures. References: [1] “Shape control of CdSe nanocrystals”, X. Peng, L. Manna, W. Yang, J. Wickham, E. Scher, A. Kadavanich and P. Alivisatos, Nature 404, 59-61 (2000). [2] “Photovoltaic Devices using Blends of Branched CdSe Nanoparticles and Conjugated Polymers”, B. Sun, E. Marx and N.C. Greenham, NanoLett 3, 961-963 (2003). [3] X. Peng, ’’Mechanisms for the shape control and shape evolution of colloidal semiconductor nanocrystals’’, Adv. Mater. 15, 459-463 (2003) [4] “Blue Luminescence and Superstructures from Magic Size Clusters of CdSe”, F.S. Riehle, R. Bienert, R. Thomann, G. Urban and M. Krüger, NanoLett 9, 514-518 (2009).
Riehle F, Yuan Y, Thomann R, Krueger M
CdSe Nanocrystals Grown by Aggregation: Evidence for a New Shape Mechanism
2010 Nano Isarel 2010: 2nd International Nanotechnology Conference & Exhibition. Tel Aviv 2010
KurzfassungControlling the size and shape of inorganic materials in the size regime of a few nanometers is one of the most challenging tasks in modern nanotechnology. In the case of CdSe nanocrystals (NCs) a fundamental discovery was made in Alivisatos’ lab, when certain impurities were found to catalyze the growth of wurtzite-type CdSe NCs along the c-axis resulting in elongated rod-like structures [1]. Since then different synthesis strategies have been developed leading to more sophisticated morphologies such as tetrapods and multipods, which have shown considerably better performance in e.g. photovoltaic devices compared to their spherical counterparts [2]. In the current models shape control takes place during the crystal growth and strongly depends on the ability of the ligands to bind preferably to certain crystal surfaces as well as on the active ‘’CdSe’’ monomer concentration [3]. In our experiments we found, that the decision about the shape of CdSe NCs is already made in the nucleation stage of their synthesis and we assume that ultra-small CdSe nanoclusters, which tend to aggregate due to their higher surface reactivity, act as nuclei for CdSe NCs [4]. At lower temperatures this aggregation process becomes dominant resulting in the growth of elongated CdSe nanostructures. Fig. 1: Different morphologies of CdSe NCs synthesized at different temperatures (from left to right: 300°C, 250°C and 200°C after 60min)
Yuan Y, Riehle F S, Krueger M
Controlling the Shape and Optical Properties of Colloidal CdTe Nanocrystals by the Variation of Simple Reaction Parameters
2010 E-MRS 2010 Fall Meeting, Warsaw, Poland
KurzfassungWe present several novel synthesis approaches for colloidal CdTe nanocrystals. By varying simple synthesis parameters such as reaction temperature, reaction time, precursor concentrations and the type of organic capping agents, different nanocrystal shapes and morphologies such as quantum dots, rods and tetrapods are obtainable. Results on optical and electron microscopical investigations will be presented. Surface ligand exchange processes during and after the nanocrystal formation can influence the optical properties dramatically with consequences for various applications in material science. The dedicated integration of such adjustable and complex CdTe nanocrystal structures into novel all inorganic based photovoltaic devices might lead to improved power conversion efficiencies compared to bulk CdTe photovoltaic systems.
Einwaechter S, Krueger M
Ein fernsteuerbarer Mikrowellensynthesereaktor zur Herstellung von Nanopartikeln mit integrierter Online Analytik
2010 19. FMF Kolloquium Schluchsee 2010
KurzfassungBasierend auf einer Labormikrowelle und Absorptions – und Photolumineszenz-Spektrometern wird per fiberoptischen Sonden und der Vernetzung von Steuercomputern ein remote-steuerbares Reaktionssystem aufgebaut und etabliert. Der BW-eLabs Remote-Laboraufbau ist ein mikrowellenbasiertes, vollautomatisiertes Reaktionssystem für die kolloidale Synthese von Nanopartikeln. Die Online-Integration von Absorptions - und Photolumineszenz- Spektroskopie erlaubt eine schnelle und zeitlich hoch aufgelöste Analyse der Wachstumsprozesse verschiedener Nanopartikel zu jeder Phase der Reaktion, was bei manueller Probenentnahme und -aufarbeitung kaum möglich ist. Dies ist insbesondere in den ersten Sekunden der Reaktionen von hohem Interesse, da sich hier die Möglichkeit ergibt, Nukleationsprozesse und deren Bedingungen zu studieren. Neben dem Potential mechanistischer Untersuchungen ergibt sich aus der guten Kontrollierbarkeit dieses Systems eine hohe Reproduzierbarkeit. Eine systematische Variation der Reaktionsparameter lässt sich mit dem automatischen Probenwechsler in einer Serie von Reaktionen zuverlässig und einheitlich durchführen und analysieren. Durch einen online-Zugang zu der Reaktionssteuerung, inklusive Datenverarbeitung, -Visualisierung und -Speicherung soll eine weltweite Nutzbarkeit gewährleistet werden. Die Leistungsfähigkeit des Systems wird am Beispiel der CdSe-Nanopartikelsynthese als Modellsystem demonstriert und soll auf weitere metallische und halbleitende Nanopartikel ausgeweitet werden.
Stevens G, Zhou Q, Krueger M, Urban G
Glo Assay for Botulinum Neurotoxin Type A
2010 BIOSENSORS 2010: 20th Anniversary World Congress on Biosensors Glasgow, UK | 26-28 May 2010
KurzfassungBotulinum NeuroToxin (BoNT) Type A is a protein produced by a species of bacteria called Clostridia Botulinum. It is considered to be a potential terrorist weapon of mass destruction because it is the most potent toxin known which could be made relatively easily in large quantities. Current tests for BoNT can only be performed by trained laboratory staff and take several hours or days to complete. In order to improve the speed and sensitivity of assays for the detection of low levels of BoNT Type A, a new approach with kind of two-stage amplification was employed. The method utilizes the enzyme activity of BoNT on a substrate which becomes enzymatically active in its presence. BoNT consists of a 100 kDa translocation and binding domain (HCC and HCN fragments) which enable the toxin to attach and gain entry to neuronal cells, and a 50 kDa catalytic domain (L domain) which is a potent Zn2+ endopeptidase that cleaves a peptide called SNAP25 that makes up part of the SNARE complex within the cell, and which is essential for acetylcholine release at the neuromuscular junction. DNA encoding the cutting and recognition sequence of SNAP25 was designed and inserted into a genetically engineered firefly (Photinus pyralis) luciferase. The toxin, suspended in 50 mM HEPES buffer at pH 7.4, could be detected in less than 30 minutes with a limit of detection of at least 70 nM. Preliminary investigations indicate that it should be possible to improve the sensitivity of this assay by varying the structure of the protein substrate. Further developments envisaged to make the assay suitable for detecting BoNT in blood using a portable detection system include use of microstructured materials such as magnetic particles to minimize diffusion distances, and absorbent materials to incorporate advantages inherent in lateral flow assays.
Zhou Y, Eck M, Riehle F, Yuan Y, Urban G, Krueger M
Hybrid Solar Cells Based on CdSe Quantum Dots and Conjugated Polymer
2010 25th European Photovoltaic Solar Energy Conference and Exhibition (25th EU PVSEC) / 5th World Conference on Photovoltaic Energy Conversion (WCPEC-5),Valencia, Spain
KurzfassungOrganic or organic/inorganic hybrid solar cells based on solution-processable conjugated polymers have the promising advantages of potentially low-cost, easy to process, and large-area fabrication on flexible substrates. Inorganic semiconductor nanocrystals (NCs) such as CdSe, with tunable bandgaps and high intrinsic charge carrier mobilities act in a similar manner as good electron acceptors and can also be incorporated into conjugated polymers such as e.g. poly(3-hexylthiophene) (P3HT) to form bulk-heterojunction hybrid solar cells. In our group, highly reproducible synthesis methods for CdSe quantum dots (QDs) have been developed, leading to monodisperse QDs with excellent photophysical properties. The photoluminescence emission colors start from blue, resulting from ultrasmall cluster-like CdSe nanoparticles [1] with diameters of about 1.6 nm, to red (ca. 5.5 nm in diameter) [2]. Bulk-heterojunction hybrid solar cells based on blends of spherical CdSe QDs (ca. 5.5 nm in diameter) and P3HT were fabricated and investigated. The QDs were treated after synthesis by a simple, fast and reproducible washing procedure [3]. No additional ligand exchange was performed thus reducing the possibility of post-synthetic surface defects. Solar cells with optimized ratios of QDs to P3HT exhibited the best power conversion efficiencies exceeding 2% under AM1.5G illumination at an intensity of 100 mW/cm2. This is among the highest reported value for a spherical CdSe QDs based photovoltaic device so far. Ref. [1] F. Riehle et al. Nano Lett. 9, 514 (2009). [2] Y. Yuan et al. J. Nanosci. Nanotech. (to be published). [3] Y. Zhou et al. Appl. Phys. Lett. 96, 013304 (2010).
Zhou Y, Riehle F, Yuan Y, Urban G, Krueger M
Improved Efficiency of Hybrid Solar Cells Based on Non Ligand-Exchanged CdSe Quantum Dots and Poly(3-Hexylthiophene)
2010 NaNaX 4 – Nanoscience with Nanocrystals International Conference, April 11-15, 2010, Munich - Tutzing (Germany)
KurzfassungInorganic semiconductor nanocrystals (NCs) such as CdSe, with tunable bandgaps and high intrinsic charge carrier mobilities can act as good electron acceptors and be incorporated into conjugated polymers such as e.g. poly(3-hexylthiophene) (P3HT) to form bulk-heterojunction hybrid solar cells. In our group, highly reproducible synthesis methods for CdSe quantum dots (QDs) have been developed. The photoluminescence emission colors start from blue, resulting from ultrasmall cluster-like CdSe nanoparticles [1] with diameters of about 1.6nm, to red (ca. 5.5 nm in diameter) [2]. The QDs (ca. 5.5 nm in diameter) were treated after synthesis by a simple, fast and reproducible washing procedure [3]. Solar cells with optimized ratios of QDs to P3HT exhibited the best power conversion efficiencies exceeding 2% under AM1.5G illumination at intensity of 100 mW/cm2 after spectral mismatch correction. This is among the highest reported value for a spherical CdSe QDs based photovoltaic device so far. Ref. [1] F. S. Riehle et al. Nano Lett. 9, 514 (2009). [2] Y. Yuan et al. J. Nanosci. Nanotech., accepted (2009). [3] Y. Zhou et al. submitted.
Zhou Y, Eck M, Riehle F, Yuan Y, Urban G, Krueger M
Improved Efficiency of Hybrid Solar Cells Based on Non-Ligand Exchanged CdSe Quantum Dots and P3HT
2010 3th International Symposium on Flexible Organic Electronics (IS-FOE10), Chalkidiki, Greece
Krueger M, Zhou Y, Eck M
Improved efficiencies of bulk-heterojunction hybrid solar cells based on CdSe quantum dots and low-bandgap conjugated polymer PCPDTBT
2010 Nano Isarel 2010: 2nd International Nanotechnology Conference & Exhibition, Tel Aviv 2010
KurzfassungInorganic semiconductor nanocrystals (NCs) such as CdSe, with tunable bandgaps and high intrinsic charge carrier mobilities can act as good electron acceptors and be incorporated into conjugated polymers to form bulk-heterojunction hybrid solar cells. Recently, we have reported on devices based on poly(3-hexylthiophene) (P3HT) and spherical CdSe quantum dots (QDs) with a simple post-synthetic hexanoic acid treatment, exhibiting the highest reported power conversion efficiencies exceeding 2% under AM1.5G illumination after spectral mismatch correction [1]. Here, we demonstrate our extended investigations on hybrid solar cells by using low band gap polymers (e.g. poly[2,6-(4,4-bis-(2-ethylhexy)-4H-cyclopenta[2,1-b;3,4-b]- dithiophene) -alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT)) and CdSe QDs, resulting in enhanced short-circuit currents and power conversion efficiencies of 2.5%, which can be attributed to the better absorption matching of PCPDTBT to the solar emission spectrum. Details on the optimization of PCPDTBT based devices and the comparison with P3HT based devices will be presented. [1] Improved efficiency of hybrid solar cells based on non ligand-exchanged CdSe quantum dots and poly(3-hexylthiophene), Y. Zhou, F.-S. Riehle, Y. Yuan, H.-F. Schleiermacher, M. Niggemann, G. A. Urban, M. Krüger, Appl. Phys. Lett., 96, 0133014 (2010).
Krueger M, Eck M, Zhou Y
Improved efficiencies of bulk-heterojunction hybrid solar cells based on CdSe quantum dots and low-bandgap conjugated polymers
2010 MRS Fall Meeting 2010, Boston, USA
KurzfassungInorganic semiconductor nanocrystals (NCs) such as CdSe, with tunable bandgaps and high intrinsic charge carrier mobilities can act as good electron acceptors and be incorporated into conjugated polymers to form bulk-heterojunction hybrid solar cells. Recently, we have reported on devices based on poly(3-hexylthiophene) (P3HT) and spherical CdSe quantum dots (QDs) with a simple post-synthetic hexanoic acid treatment, exhibiting the highest reported power conversion efficiencies exceeding 2% under AM1.5G illumination after spectral mismatch correction [1]. Here, we demonstrate our extended investigations on hybrid solar cells by using low band gap polymers (e.g. poly[2,6-(4,4-bis-(2-ethylhexy)-4H-cyclopenta[2,1-b;3,4-b]- dithiophene) -alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT)) and CdSe QDs, resulting in enhanced short-circuit currents and power conversion efficiencies, which can be attributed to the better absorption matching of PCPDTBT to the solar emission spectrum. Details on the optimization of PCPDTBT based devices and the comparison with P3HT based devices will be discussed. [1] Y. Zhou et al. Appl. Phys. Lett. 96, 013304 (2010).
Ledernez L, Olcaytug F, Urban G
Independent Influence of the Inter-Electrode Distance in Paschen Curves
2010 ESCAMPIG, Novi Sad, Serbia
Enderle B, Dame G, Ledernez L, Olcaytug F, Yasuda H, Urban G
Magnetron Enhanced Plasma-Polymerization as a Biocompatible Sensor Coating for Enzyme Based Biosensors
2010 Biosensors, Glasgow, United Kingdom
Albrecht B, Hautzinger D, Krüger M, Elwenspoek M, Müller K M, Korvink J G
Metal Nanoparticles Patterned on Self-Assembled DNA Origami and Adsorption on Silicon Dioxide
2010 19. FMF Kolloquium, Schluchsee2010
KurzfassungSelf-assembled DNA nanostructures promise low-cost ways to create nanoscale shapes. Em-ploying the DNA origami method1, it is possible to design and produce arbitrarily shaped two-dimensional DNA nanostructures about 100×100 nm² in size by self-assembly. Further-more, self-assembled DNA nanostructures can be used to position nanoparticles with nanometer precision for nanophotonics and nanoelectronics applications. Yet, reliable and low-cost ways of integrating the structures with MEMS technology still have to be developed and innovations are of great interest to the field. The figure shows AFM images of the adherence of DNA origami tiles on silicon dioxide surfaces of silicon wafers in dependence on pH-value and magnesium ion concentration. Different routs exist to link gold nanoparticles on DNA origami. 1 Paul W. K. Rothemund, "Folding DNA to create nanoscale shapes and patterns," Nature, vol. 440, no. 7082, pp. 297-302, 2006.
Horak J, Enderle B, Bakirci H, Urban A
Micro-Immunoassay for Rapid Quantification of Substance-P in Biological Fluids
2010 BMT, Rostock, Germany
Krueger M, Yuan Y, Riehle F S, Nitschke R
Nanocrystal-Polymer Hybrid Materials as Calibration Standard for Confocal Laser Scanning Microscopy
2010 MRS Fall Meeting 2010, Boston, USA
KurzfassungThe resolution of three dimensional fluorescent microscopical imaging strongly depends on the calibration of the instrument. This requires highly photostable fluorophores, therefore standard organic dyes cannot be utilized. Semiconductor nanocrystals are promising fluorophores due to their high brightness, photostability and quantum yield. We present novel CdSe NC-polymer hybrid materials with high quantum yields based on CdSe core quantum dots (QDs). Highly luminescent core NCs are incorporated in-situ into the polymer network during the polymerization reaction. The NCs are fixed and “frozen” into the polymeric network leading to a homogeneous distribution within the polymer maintaining their excellent photoluminescent properties. The hybrid materials can be further processed from the liquid phase leading to various desired forms and shapes. Laser scanning microscopical investigations revealed a high photostability of various polymer hybrids with different emission colors over a wide range of light exposure conditions such as time, laser power etc.. They were superior compared to polymer hybrids based on commercially available core shell CdSe/ZnS QDs which were unstable under the same experimental conditions. The potential of CdSe polymer hybrid materials for the establishment of a calibration standard for confocal laser scanning microscopy will be demonstrated and highlighted.
Yuan Y, Riehle F, Krueger M
Nanocrystal-Polymer Hybrid Materials for Tailored and Effective Energy Conversion
2010 EMPA Students Symposium, EMPA Akademie, Dübendorf, Schweiz
KurzfassungThe improvement of energy conversion and storage is one of the major tasks to achieve further optimization of the global energy management. In addition self-sufficient energy harvesting technologies are currently developed to obtain autonomous and flexible small devices harvesting energy from the environment similar to photosynthesis. We present a novel CdSe NC-polymer hybrid material for tailored and effective energy conversion. The CdSe NCs with quantum yields of about 70% are incorporated in-situ into the Nylon polymer network during the polymerization reaction. The NCs are fixed and “frozen” into the polymeric network leading to a homogeneous distribution within the polymer maintaining their excellent photoluminescent properties (QY of up to 65 %). It can be processed from the liquid phase leading to various desired forms and shapes. Such systems have high-potential as optical filters, detectors, UV absorbing layers and effective light converting systems in which the out coming energy can be adjusted to the specific needs eg. for the optimized growth of algae to produce biofuels.
Yuan Y, Riehle F S, Urban G A, Krueger M
Nanocrystal-Polymer Hybrid Materials for Tailored and Effective Energy Conversion
2010 NaNaX 4 – Nanoscience with Nanocrystals International Conference, April 11-15, 2010, Munich - Tutzing (Germany)
KurzfassungThe improvement of energy conversion and storage is one of the major tasks to achieve further optimization of the global energy management. In addition self-sufficient energy harvesting technologies are currently developed to obtain autonomous and flexible small devices harvesting energy from the environment similar to photosynthesis. We present a novel CdSe NC-polymer hybrid material for tailored and effective energy conversion. The CdSe NCs with quantum yields of about 70% are incorporated in-situ into the Nylon polymer network during the polymerization reaction. The NCs are fixed and “frozen” into the polymeric network leading to a homogeneous distribution within the polymer maintaining their excellent photoluminescent properties (QE of up to 65 %). It can be further processed from the liquid phase leading to various desired forms and shapes. Such systems have high-potential as optical filters, detectors, UV absorbing layers and effective light converting systems in which the out coming energy can be adjusted to the specific needs eg. for the optimized growth of algae to produce biofuels. They can be additionally utilized in solar concentrator cells. Approaches to improve long term stability and transparency of the NC-polymer hybrid-films are currently under investigation.
Krueger M, Yuan Y, Riehle F S
Nanocrystal-Polymer hybrid materials for tailored and effective energy conversion
2010 Nanotchday Nordwestschweiz, 11.Mai 2010, Basel
Eck M, Zhou Y, Krüger M
Nanohybrid Solarzellen von CdSe Nanostrukturen und halbleitenden Polymeren
2010 19. FMF Kolloquium Schluchsee 2010
KurzfassungOrganische Solarzellen sind ein hochaktuelles Forschungsgebiet in der Photovoltaik. Sie stellen eine potentiell kostengünstige Alternative dar, die ein großes Entwicklungspotential hat, und sich bereits auf dem Weg zur Marktreife befindet. In der Regel setzt sich die photoaktive Schicht aus einem Elektronen Donor sowie einem Elektronen Akzeptor Material zusammen. Ersetzt man die Fullerne basierten Elektronenakzeptoren durch halbleitende Nanopartikel, wie z.B. CdSe Quantum Dots und Rods erhält man sogenannte hybride Solarzellen. Durch den Einsatz von Nanopartikeln verspricht man sich eine verbesserte Elektronenextraktion und eine erhöhte intrinsische Elektronenleitfähigkeit. Jedoch besitzen Nanopartikel eine isolierende Ligandenschutzhülle die den Ladungsübergang zwischen den Nanopartikeln und die Ladungsextraktion aus dem Polymer erschwert. Es wird ein Waschprozess für sphärische und elongierte Nanopartikel beschrieben durch den diese Ligandenhülle entscheidend verringert und damit die Effizienz der entsprechenden photovoltaischen Zelle entscheidend gesteigert wird. Beleuchtet wird auch der Einfluss des Polymers auf hybride Solarzellen. Optimierte Solarzellen liefern Effizienzen bis zu 2.7% basierend auf CdSe Quantum Dots und dem Polymer Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']-dithiophen)-alt-4,7-(2,1,3-benzothiadiazol)] (PCPDTBT).
Krueger M
Nanosensoric Systems for Applications in Biology and Medicine
2010 BMT Jahrestagung 2010: 44. DGBMT JAHRESTAGUNG 3-LÄNDER-TAGUNG D-A-CH, Rostock-Warnemünde, Deutschland
KurzfassungNanoparticles and nanostructured materials in general demonstrate a high potential for the integration into fast, specific and highly sensitive nanosensoric systems. Different examples are presented based on nanomaterials and nanostructures demonstrating their use as markers and probes as well as in optical and electrochemical sensing of local changes of the environment such as pH and oxygen concentration. Their use and suitability to be integrated into highly-sensitive bioanalytical tests will be demonstrated as well.
Wang B, Lenz D, Krueger M, Rodriguez M, Ditengou F, Wang D, Verdaguer S, Herlin-Boime N, Urban G, Li X, Bottaro T, Uhl R, Palme K
Perspectives in Nanoparticle Imaging of Living Cells
2010 AIP Conference Proceedings, American Institute of Physics, Band: 1275, Seiten: 162 - 165
Krueger M, Yuan Y, Riehle F S, Nitschke R
Photostable Nanocrystal-Polymer Hybrid Materials as Calibration Standard for Confocal Laser Scanning Microscopy
2010 19. FMF Kolloquium Schluchsee 2010
KurzfassungThe resolution of three dimensional fluorescent microscopical imaging strongly depends on the calibration of the instrument. This requires highly photostable fluorophores, therefore standard organic dyes cannot be utilized. Semiconductor nanocrystals are promising fluorophores due to their high brightness, photos-tability and quantum yield. We present novel CdSe NC-polymer hybrid materials with high quantum yields based on CdSe core quantum dots (QDs). Highly luminescent core NCs are incorporated in-situ into the polymer network during the polymerization reaction. The NCs are fixed and “frozen” into the polymeric network leading to a homogeneous distribution within the polymer maintaining their excellent photoluminescent properties. The hybrid materials can be further processed from the liquid phase leading to various desired forms and shapes. Laser scanning microscopical investigations revealed a high photostability of various polymer hybrids with different emission colors over a wide range of light exposure conditions such as time, laser power etc.. They were superior compared to polymer hybrids based on commercially available core shell CdSe/ZnS QDs which were unstable under the same experimental conditions. The potential of CdSe polymer hybrid materials for the establishment of a calibration standard for confocal laser scanning microscopy will be demonstrated and highlighted.
Horak J, Bakirci H, Urban G
Rapid quantification of neuropeptide levels in body fluids with capillary immunochip
2010 Biosensors Conference, Glasgow, UK,
Horak J, Dincer C, Bakirci H, Urban G
Rapid quantification of neuropeptide levels in body fluids with capillary immunochip
2010 Biosensors, Glasgow, UK
Razum M, Einwaechter S, Fridman R, Herrmann M, Krueger M, Pohl N, Schwichtenberg F, Zimmermann K
Research Data Management in the Lab
2010 5th International Conference on Open Repositories 2010, July 6-9, 2010, Madrid
KurzfassungResearch, especially in science, is increasingly data-driven (Hey & Trefethen, 2003). The obvious type of research data is raw data produced by experiments (by means of sensors and other lab equipment). However, other types of data are highly relevant as well: calibration and configuration settings, analyzed and aggregated data, data generated by simulations. Today, nearly all of this data is born-digital. Based on the recommendations for “good scientific practice”, researchers are required to keep their data for a long time. In Germany, DFG demands 8-10 years for published results(Deutsche Forschungsgemeinschaft, 1998). Ideally, data should not only be kept and made accessible upon request, but be published as well – either as part of the publication proper, or as references to data sets stored in dedicated data repositories. Another emerging trend are data publication journals, e.g. the Earth System Science Data Journal.In contrast to these high-level requirements, many research institutes still lack a well-established and structured data management. Extremely data-intense disciplines like high-energy physics or climate research have built powerful grid infrastructures, which they provide to their respective communities. But for most „small sciences“, such complex and highly specialized compute and storage infrastructures are missing and may not even be adequate. Consequently, the burden of setting up a data management infrastructure and of establishing and enforcing data curation policies lie with each institute or university. The ANDS project has shown that this approach is even preferable over a central (e.g., national or discipline-specific) data repository (The ANDS Technical Working Group, 2007). However, delegating the task of proper data curation to the head of a department or a working group adds a huge workload to their daily work. At the same time, they typically have little training and experience in data acquisition and cataloging. The library has expertise in cataloging and describing textual publications with metadata, but typically lacks the discipline specific knowledge needed to assess the data objects in their semantic meaning and importance. Trying to link raw data with calibration and configuration data at the end of a project is challenging or impossible, even for dedicated ‘data curators’ and researchers themselves. Consequently, researchers focus on their (mostly textual) publications and have no established procedures on how to cope with data objects after the end of a project or a publication (Helly, Staudigel, & Koppers, 2003). This dilemma can be resolved by acquiring and storing the data automatically at the earliest convenience, i.e. during the course of an experiment. Only at this point in time, all the contextual information is available, which can be used to generate additional metadata. Deploying a data infrastructure to store and maintain the data in a generic way helps to enforce organization-wide data curation policies. Here, repository systems like Fedora2 (Lagoze, Payette, Shin, & Wilper, 2005) or eSciDoc3(Dreyer, Bulatovic, Tschida, & Razum, 2007) come into play. However, an organization-wide data management has only a limited added-value for the researcher in the lab. Thus, the data acquisition should take place in a non-invasive manner, so that it doesn’t interfere with the established work processes of researchers and thus poses a minimal threshold to the scientist.
Riehle F, Stevens G B, Urban G, Krueger M
Towards a Highly Sensitive Multiplexed Immunoassay Using Fluorescent and Magnetic Nanoparticles
2010 CLINAM: 3rd European Conference for Clinical Nanomedicine, Basel, Switzerland
KurzfassungAt the Institute for Microsystems Technology (IMTEK) at the University of Freiburg, interdisciplinary research is performed combining engineering and medical aspects. The development of new lab on the chip based mobile systems for the detection of toxins and bacteria is one example. The interaction of scientists with various background from microsystems engineering, physics, chemistry, biology and material science allows a high degree of multidisciplinary exchange. The miniaturisation of various devices including medical devices is an important field which is addressed at the IMTEK as well. One example here is the development of autonomous implantable devices such as e.g. a pacemaker which harvests the energy needed for its operation directly from the environment. The development of a glucose fuel cell connected to a pacemaker allows e.g. the utilization of the sugar and the oxygen in blood to be the energy source for implantable devices. This development includes research on novel efficient nano-catalytic systems as electrodes for biocompatible fuel cells. In collaboration with the Freiburg Materials Research Centre (FMF) new synthesis routes for magnetic and fluorescent nanoparticles are developed with nanosenoric functionalities. The aim here is to develop a sensor toolkit to detect multiparametric parameters on the cellular level. Local changes of ph, oxygen concentration and other highly important metabolites are aimed to be detected in order to investigate the development of diseases on the cellular and molecular level. Progress in this field will enable the detection of diseases at a much earlier stage and suitable tests can be developed. On the other hand a new door will be opened to develop novel treatments of e.g. cancer. The overlap of Microtechnology with Nanotechnology is higly desired to promote and enhance the suitability of nanotechnology especially in the field of medicine.

2009

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Riehle F, Galvez E M, Graeber P, Urban G, Krueger M
A new type of ultra-small fluorescent nanoparticle as promising tool for the labeling of the H+-ATPase
2009 Nano 2009 Israel - The International Nano Technology Conference, Jerusalem, Israel
KurzfassungSince the first successful bio-labeling experiments with fluorescent nanocrystals NCs) in the late 90s many efforts have been undertaken to push the research on this rapidly growing field of nano-biotechnology. It is principally envisaged to replace conventional fluorophores such as organic dyes or fluorescent proteins by advanced nano-materials due to their superior optical properties, e.g. higher photo-stabilities and broad excitation spectra. Especially, the simultaneous observation of different biological processes over a long period of time would become possible, giving a deeper insight into complex biological mechanisms. However, one major drawback of biocompatible nano-materials, besides their intrinsic cytotoxity, is their large size, which limits their use for biological applications. For instance, FRET experiments, which require a short distance between the involved fluorophores would become possible, if smaller stable nano-materials were available. The H+-ATPase is a well-known protein of the respiratory chain located in the cell membrane, which uses a proton gradient as driving force for the production of ATP, the biological energy currency. During this reaction process, the rotor part of the ATPase is rotating within the enzyme. However, very little is known about the long time stability of rotation in ATP synthesis direction, which is important for the better understanding of the underlying mechanism. So far, interpretation of results from FRET studies using conventional nanocrystals as fluorescence donors is difficult due to their large hydrodynamic particle size (approximately 10-20 nm). Here, we present a new type of ultra-small fluorescent nanoparticle, which could be an appropriate candidate for the specific labeling of enzymes like the H+-ATPase.
Horak J, Enderle B, Bakirci H, Urban G A
Amperometric Micro-Immunosensor for Rapid Substance-P Quantification in Biological Fluids
2009 IEEE Sensors, Christchurch (New Zealand)
Horak J, Enderle B, Bakirci H, Urban G
Amperometric Monitoring of Substance-P and proSubstance-P Levels in Biological Fluids
2009 IEEE Eurosensors, Lausanne (Switzerland)
Horak J, Enderle B, Bakirci H, Urban G
Amperometric Monitoring of Substance-P and proSubstance-P Levels in Biological Fluids
2009 World Congress on Medical Physics and Biomedical Engineering, Munich (Germany)
Vulto P, Zahn P, Maier U, Dame G, Urban G
Automated RNA Isolation By Electrophoretic Purification And Thermo-Electric Lysis
2009 MSB 2008/ Berlin , Band: 1, Seite: 39
Riehle F, Bienert R, Thomann R, Urban G, Krueger M
Blue Luminescence and Superstructures from Magic-size Clusters of CdSe
2009 MRS Meeting 2009, Boston, USA
KurzfassungRecently we found a new kind of CdSe nanocluster with exceptional opto-physical and chemical properties such as strong blue band-gap luminescence and the ability to form highly ordered one-dimensional superstructures. These interesting features make the nanoclusters appropriate candidates for potential applications in the fields of bio-imaging, laser and display technology. Furthermore their involvment in the crystallization process as well as the elucidation of their internal structure is a topic of our current research
Zhou Y, Urban G, Krueger M
Bulk-Heterojuction Solar Cells Based on Nanocrystal-Polymer Hybrid Materials
2009 DPG Tagung Dresden, TU Dresden
KurzfassungOrganic solar cells have the promising advantages of low-cost and large-area fabrication on flexible substrates. State-of-the-art organic solar cells based on blends of conjugated polymers and fullerene derivatives achieve efficiencies up to 5-6% [1, 2]. Inorganic semiconductor nanocrystals (NCs) e.g. out of CdSe, with tunable bandgaps and high intrinsic carrier mobilities, can be incorporated into conjugated polymers e.g. poly(3-hexylthiophene) (P3HT) to form bulk-heterojunction hybrid solar cells[3]. In our group, a highly reproducible synthesis method for CdSe NCs has been developed, leading to monodisperse NCs (Fig.1) with excellent photophysical properties. Current research is performed to control the shape and the lattice structure of the NCs within the same synthesis approach. Solar cells (Fig.2) based on bulk-heterojunction CdSe NCs/P3HT hybrid materials have been fabricated and characterized. Devices using spherical NCs capped with aromatic ligands and appropriate thermal annealing treatment exhibit power conversion efficiencies over 0.8% (Fig.3) under standard measurement condition Air Mass (AM) 1.5 global illumination, which is among the highest reported values for spherical CdSe quantum dots. Further investigations to improve the materials and device performance are currently in progress. References [1] J. Peet, J. Y. Kim, N. E. Coates, W. L. Ma, D. Moses, A. J. Heeger, G. C. Bazan. Nature Mater. 6, 497, (2007). [2] G. Li, V. Shrotriya, J. Huang, Y. Yao, T. Moriarty, K. Emery, Y. Yang, Nature Mater. 4, 864 (2005). [3] W. U. Huynh, J. J. Dittmer, A. P. Alivisatos, Science 295, 2425 (2002).
Zhou Y, Urban G, Krueger M
Bulk-Heterojuction Solar Cells Based on Nanocrystal-Polymer Hybrid Materials
2009 Nano 2009 Israel - The International Nano Technology Conference, Jerusalem, Israel
KurzfassungTremendous efforts are currently undertaken to enlarge the percentage of environmental green energy sources to satisfy the future world energy demand. Photovoltaics (PV) are one of the prominent technologies able to match the boundary criteria. The main applications in PV are based on silicon technology, additionally the dye sensitizes solar cells might become important for large-scale applications as well since they will soon approach commercialization. Potential alternatives to batteries for running small self–sustaining devices are organic solar cells. They have the promising advantages of low-cost and large-area fabrication on flexible substrates and are able to work under low light conditions. State-of-the-art organic solar cells based on blends of conjugated polymers and fullerene derivatives achieve efficiencies up to 5-6%. Inorganic semiconductor nanocrystals (NCs) e.g. out of CdSe, with tunable bandgaps and high intrinsic carrier mobilities, can be incorporated into conjugated polymers e.g. poly(3-hexylthiophene) (P3HT) to form bulk-heterojunction hybrid solar cells. In our group, a highly reproducible synthesis method for CdSe NCs has been developed, leading to monodisperse NCs with excellent photophysical properties. Current research is undertaken to control the shape and the surface functionalization of NCs. Various solar cells based on bulk-heterojunction nanocomposite materials have been fabricated and characterized. The nanocomposite photoactive layer consists out of conjugated polymer (P3HT) as electron donor and semiconducting CdSe NCs as electron acceptor. We systematically checked how the solar cell device performance is affected by different NC ligands and different thermal annealing treatments. Devices using spherical NCs capped with aromatic ligands exhibit so far power conversion efficiencies around 1% under standard measurement condition (Air Mass (AM) 1.5 under global illumination). Further investigations to improve the materials and device performance are currently in progress using elongated structures of various NCs based on CdSe, CdTe, PbS, PbSe etc. and by controlling the surface properties of NCs.
Zhou Y, Yuan Y, Urban G, Krueger M
Bulk-Heterojuction Solar Cells Based on Nanocrystal-Polymer Hybrid Materials
2009 E-MRS spring Meeting 2009, Strasbourg, France
KurzfassungOrganic solar cells have the promising advantages of low-cost and large-area fabrication on flexible substrates. State-of-the-art organic solar cells based on blends of conjugated polymers and fullerene derivatives achieve efficiencies up to 5-6% [1, 2]. Inorganic semiconductor nanocrystals (NCs) e.g. out of CdSe, with tunable bandgaps and high intrinsic carrier mobilities, can be incorporated into conjugated polymers e.g. poly(3-hexylthiophene) (P3HT) to form bulk-heterojunction hybrid solar cells[3]. In our group, a highly reproducible synthesis method for CdSe NCs has been developed, leading to monodisperse NCs (Fig.1) with excellent photophysical properties. Current research is performed to control the shape and the lattice structure of the NCs within the same synthesis approach. Solar cells (Fig.2) based on bulk-heterojunction CdSe NCs/P3HT hybrid materials have been fabricated and characterized. Devices using spherical NCs capped with aromatic ligands and appropriate thermal annealing treatment exhibit power conversion efficiencies over 0.8% (Fig.3) under standard measurement condition Air Mass (AM) 1.5 global illumination, which is among the highest reported values for spherical CdSe quantum dots. Further investigations to improve the materials and device performance are currently in progress. References [1] J. Peet, J. Y. Kim, N. E. Coates, W. L. Ma, D. Moses, A. J. Heeger, G. C. Bazan. Nature Mater. 6, 497, (2007). [2] G. Li, V. Shrotriya, J. Huang, Y. Yao, T. Moriarty, K. Emery, Y. Yang, Nature Mater. 4, 864 (2005). [3] W. U. Huynh, J. J. Dittmer, A. P. Alivisatos, Science 295, 2425 (2002).
Hussein L, Feng Y, Habrioux A, Servat K, Kokoh B, Alonso-Vante N, Urban G, Krüger M
Decorated Nanotube Buckypaper as Electrocatalyst for Glucose Fuel Cells
2009 IEEE Transducers 2009 (Denver), USA
Hussein L, Urban G, Krüger M
Decorated Nanotube Buckypaper as Electrocatalyst for Glucose Fuel Cells
2009 6. Deutsches Biosensor Symposium, Freiburg
Stevens G B, Zhou Q, Urban G, Krueger M
Development of an In-Vitro Assay for Botulinium Toxin Type A
2009 18. FMF Kolloquium, Schluchsee
KurzfassungA sensitive assay based on firefly luciferase has been developed for detecting the proteolytic activity of L domain of botulinum toxin type A (BoNT/A-L) suspended in 50 mM HEPES buffer at pH 7.4. After preparing the assay, a test for BoNT/A can be performed in less than one hour with a limit of detection of at least 70 nM. Preliminary investigations indicate that it should be possible to improve the sensitivity of this assay. Further developments needed to make the assay suitable for detecting BoNT/A in blood using a portable detection system are discussed.
Krueger M, Zhou Y, Hussein L, Urban G
Energy Harvesting based on Nano-Hybridmaterials
2009 18 FMF Kolloquium, Schluchsee
KurzfassungSince recently nanoparticles are widely explored in nano-hybridsystems for generating new energy harvesting systems and are believed to have high potential in future energy supplying devices as well as for novel and efficient energy storage systems. Two different examples will be demonstrated: 1) The use of semiconducting nanoparticles in inorganic-organic hybrid solar cells and, 2) the use of nanoparticle or enzyme decorated MWNT based hybrid systems for novel fuel cell electrodes.
Cubukcu A, Urban G
Frequency Response of a 2D Flow and Thermal Property Sensor
2009 IEEE EuroSimE, Delft (Netherlands)
Zhou Y, Yuan Y, Riehle F S, Urban G A, Krueger M
Hybrid Solar Cells Based on CdSe Quantum Dots and Poly(3-Hexylthiophene)
2009 IC4N 2009: 2nd International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems (IC4N), Rhodes Island, Greece
KurzfassungOrganic or organic/inorganic hybrid solar cells based on solution-processable conjugated polymer have the promising advantages of potentially low-cost, easy to process, and large-area fabrication on flexible substrates. Inorganic semiconductor nanocrystals (NCs) such as CdSe, with tunable bandgaps and high intrinsic carrier mobilities, can also be incorporated into conjugated polymers e.g. poly(3-hexylthiophene) (P3HT) as good electron acceptors to form bulk-heterojunction hybrid solar cells [1]. Here we report on improved efficiencies of bulk-heterojunction hybrid solar cells based on a blend of spherical CdSe quantum dots (QDs) and P3HT. The QDs are post-synthetic modified without ligand exchange, instead of applying routine treatment by refluxing the NCs in pyridine solution. Solar cells with optimized ratios of QDs to P3HT exhibited power conversion efficiencies over 2.0%, which is the highest reported value for spherical CdSe QDs based photovoltaic device, under AM1.5G illumination at an intensity of 100 mW/cm2. Further investigations to improve the materials and device performance are currently in progress using elongated structures of various NCs based on CdSe, CdTe, PbS, PbSe etc. and by controlling the surface properties of NCs. Fig. 1 (a) Device structure, (b) TEM image of CdSe QDs Fig. 2 Device performance References: [1] “Hybrid Nanorod-Polymer Solar Cells”, W. U. Huynh, J. J. Dittmer, A. P. Alivisatos, Science, 295, 2425 (2002).
Krueger M, Zhou Y, Yuan Y, Riehle F, Urban G A
Hybrid Solar Cells Based on CdSe Quantum Dots and Poly(3-hexylthiophene)
2009 Nano Materials 09, Bonn, Germany
Zhou Y, Riehle F, Yuan Y, Urban G, Krueger M
Hybrid Solar Cells Based on Non-ligand Exchanged CdSe Quantum Dots and Poly(3-hexylthiophene)
2009 MRS Meeting 2009, Boston, USA
Krueger M, Zhou Y, Riehle F, Yuan Y, Urban G A
Hybrid Solar Cells based on CdSe Quantum Dots and Poly(3-hexylthiophene)
2009 FRIAS 2nd Black Forest Focus Treffen
KurzfassungOrganic or organic/inorganic hybrid solar cells based on solution-processable conjugated polymers have the promising advantages of potentially low-cost, easy to process, and large-area fabrication on flexible substrates. Inorganic semiconductor nanocrystals (NCs) such as CdSe, with tunable bandgaps and high intrinsic charge carrier mobilities act in a similar manner as good electron acceptors and can also be incorporated into conjugated polymers such as e.g. poly(3-hexylthiophene) (P3HT) to form bulk-heterojunction hybrid solar cells. In our group, highly reproducible synthesis methods for CdSe quantum dots (QDs) have been developed, leading to monodisperse QDs with excellent photophysical properties. The photoluminescence emission colors start from blue, resulting from ultrasmall cluster-like CdSe nanoparticles [1] with diameters of about 1.6nm, to red (ca. 5.5 nm in diameter) [2]. Current research is undertaken to control the shape and the surface functionalization of NCs. Bulk-heterojunction hybrid solar cells based on blends of spherical CdSe QDs (ca. 5.5 nm in diameter) and P3HT were fabricated and investigated. The QDs were treated after synthesis by a simple, fast and reproducible washing procedure [3]. No additional ligand exchange was performed thus reducing the possibility of post-synthetic surface defects. Solar cells with optimized ratios of QDs to P3HT exhibited power conversion efficiencies of 1.7%-1.8% under AM1.5G illumination at intensity of 100 mW/cm2. This is among the highest reported value for a spherical CdSe QDs based photovoltaic device so far. Further investigations to improve the materials and device performance are currently in progress using elongated structures of various NCs based on CdSe, CdTe, PbS, PbSe etc. and by controlling the surface properties of NCs. [1] F. S. Riehle et al. Nano Lett. 9, 514 (2009). [2] Y. Yuan et al. J. Nanosci. Nanotech., accepted (2009). [3] Y. Zhou et al. submitted.
Enderle B, Dame G, Bieser U, Zahn P, Ledernez L, Olcaytug F, Keck D, Von Dobschuetz E, Yasuda H, Urban G
Improving Biocompatibility of Miniaturized Multiparameter Sensors for Implantation in Intraabdominal Areas
2009 World Congress on Medical Physics and Biomedical Engineering, Munich, Germany
Ledernez L, Olcaytug F, Yasuda H, Urban G
Influence of Cathode Material on Breakdown Current of Abnormal Glow Discharges
2009 ICPIG-19, Cancun, Mexico
Ledernez L, Olcaytug F, Yasuda H, Urban G
Influence of Inter-Electrode Distance on the Breakdown Voltage of Argon
2009 ICPIG-19, Cancun, Mexico
Enderle B, Olcaytug F, Ledernez L, Dame G, Bieser U, Zahn P, Keck D, Von Dobschütz E, Yasuda H, Urban G
Magnetron Enhanced Plasma-Polymerization for Biocompatible Sensor Coatings and Membranes on Polymeric Based Materials
2009 World Congress on Medical Physics and Biomedical Engineering, Munich, Germany
Ledernez L, Olcaytug F, Urban G, Yasuda H
Magnetron Race Track in Plasma Polymerization Processes
2009 ISPC-19, Bochum, Germany
Kieninger J
Microbiosensor-Systems for Cellular Monitoring
2009 SENSOR+Test Conference 2009, 26.-28.05.2009
Yuan Y, Riehle F, Urban G, Krüger M
Nanocrystal-Polymer Hybrid Materials for Tailored and Effective Energy Conversion
2009 Nano 2009 Israel - The International Nano Technology Conference, Jerusalem, Israel
KurzfassungHere we present a novel method for the incorporation of highly luminescent CdSe NCs in Nylon using an in-situ incorporation approach of NCs into the polymeric network already during the polymerization reaction. The NCs are fixed and “freezed” into the polymeric network, which takes part at least partially in the stabilization of the NCs as well, leading to well distributed NCs within the polymer network while maintaining their excellent photoluminescent properties. The functionalized hybrid polymer can be further processed from the liquid phase leading to various desired forms and shapes. Such systems might become important as optical filters, UV absorbing layers and as highly effective light converting systems in which the out coming energy can be tailored and adjusted to the needs.
Jeschke S, Burr B, Hahn J U, Helmes L, Kriha W, Krüeger M, et al
Networking Resources for Research and Scientific Education in BW-eLabs
2009 In 10th ACIS International Conference on Software Engineering, Artificial Intelligences, Networking and Parallel/Distributed Computing IEEE Computer Society , Band: 1, Seiten: 47 - 52
Jeschke S, Burr B, Hahn J U, Helmes L, Kriha W, Krueger M
Networking Resources for Research and Scientific Education in BW-eLabs
2009 In 10th ACIS International Conference on Software Engineering, Artificial Intelligences, Networking and Parallel/Distributed Computing IEEE Computer Society , Band: 1
Hussein L, Jensen K, Alia S, Contreras C, Yan Y, Urban G, Krüger M
Novel Nanotube Buckypaper as Electrode Material for Fuel Cell Applications
2009 Proc.PowerMEMS, December 01-04, 2009, Washingtion, USA , Seiten: 112 - 115
Hussein L, Jensen K, Alia S, Contreras C, Yan Y, Urban G, Krüger M
Novel Nanotube Buckypaper as Electrode Material for Fuel Cell Applications
2009 Power Mems 2009: 9th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, Washington, USA
KurzfassungWe present novel supported electro-catalytic systems based on metallic/bimetallic (Pt, Au-Pt) nanoparticles decorated carbon nanotubes Buckypaper (BP), and Bilirubin Oxidase (BOD) decorated Buckypaper-based biocathodes in neutral medium for direct glucose fuel cell. The electrodes have been tested for their suitability in mixed-reactant biofuel cell applications in a phosphate buffer solution (0.2 M PBS, pH 7.4) containing 10 mM glucose by applying a Potentiodynamic polarization method. High efficiency, stability and catalytic activity are observed for the Oxygen Reduction Reaction (ORR) that resulted in a high limiting current density for this biocathode. The ability to catalyze electrode reaction via a mediatorless (direct) electron transfer has been demonstrated. The electron is transferred directly from the BP-based electrode to the substrate molecule (O2) via the active site of the enzyme (BOD). Furthermore, enhanced glucose-tolerance and catalytic properties are demonstrated in regards to ORR for abiotic (Pt nanoparticles) BP-based cathode in comparison to AuPt/BP-based electrode. Our decorated-BP exhibits superior properties making it a promising support material for biofuel cell electrodes to power small devices and biosensors.
Aravindalochanan K, Kieninger J, Sandvik A, Pettersen E O, Urban G A
Optimizing a Nitric Oxide Sensing Technique for Hypoxic Tumor Cell Cultures
2009 IEEE Transducers, Denver (USA)
Riehle F, Yuan Y, Thomann R, Urban G, Krueger M
Self-Aggregation of Small Nanoparticles: a New Approach Towards Shape Control
2009 IC4N 2009: 2nd International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems (IC4N), Rhodes Island, Greece
KurzfassungControlling the structure and shape of inorganic materials in the size regime of a few nanometers is one of the most challenging tasks in modern nanotechnology. In the case of semiconductor nanocrystals (NCs) a fundamental discovery was made in Alivisatos’ lab, when certain impurities were found to catalyze the growth of wurtzite-type CdSe NCs along the c-axis resulting in elongated rod-like structures [1]. Since then different synthesis strategies have been developed leading to more sophisticated morphologies such as tetrapods and multipods, which have shown considerably better performance in e.g. photovoltaic devices compared to their spherical counterparts [2]. In most of the CdSe NCs syntheses shape control takes place during the crystal growth and strongly depends on the precursor concentration as well as on the ability of the ligands to bind to the crystal surface. In our work we found, that the decision about the shape of CdSe NCs is already made in the nucleation stage of their synthesis and that at high monomer concentration the formation of spherical particles is favored. We assume that ultra-small CdSe nanoparticles, which tend to aggregate due to their higher surface reactivity, act as nuclei for CdSe NCs [3]. At low monomer concentration the aggregation process becomes more dominant resulting in the growth of elongated nanostructures. Fig. 1: Different morphologies of CdSe NCs synthesized at different temperatures References: [1] “Shape control of CdSe nanocrystals”, Peng et al., Nature 404, 59-61 (2000). [2] “Photovoltaic Devices using Blends of Branched CdSe Nanoparticles and Conjugated Polymers”, Sun et al., NanoLett 3, 961-963 (2003). [3] “Blue Luminescence and Superstructures from Magic Size Clusters of CdSe”, Riehle et al., NanoLett 9, 514-518 (2009).
Aravindalochanan K, Kieninger J, Urban G, Jobst G
Simulation and Design of A Nitric Oxide Sensor Array for Cell Cultures
2009 IEEE Sensors, Christchurch (New Zealand)
Cubukcu A, Urban G
Simulation and fabrication of a 2D-Flow Sensor for Thermal Characterization of Fluids and for Flow Speed Measurements
2009 IEEE Transducers, Denver (USA)
Cubukcu A S, Urban G A
Simulation and fabrication of a 2D-Flow Sensor for Thermal Characterization of Fluids and for Flow Speed Measurements
2009 IEEE Eurosensors, Lausanne (Switzerland) Procedia Chemistry, Band: Vol. 1, Nummer: 1, Seiten: 887 - 890
Krueger M, Darbandi M, Yuan Y, Urban G
Tuning of the Size and the Optical Properties of Silica Coated CdSe/ZnS Nanoparticles
2009 International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems (IC4N), Rhodes Island (Greece)
KurzfassungOver the recent decades, luminescent semiconductor nanocrystals (so called “Quantum Dots” or QDs) have been attracted a lot of interests because of remarkable size and shape-dependent properties. Nonetheless, QDs cannot be used directly because of certain limitations in practical application such as toxicity, hydrophobicity, interactions with oxygen, etc. Therefore further development of applications of semiconductor nanoparticles requires their incorporating into various matrixes (e.g. protective shells out of large-band-gap semiconductor material, polymer shells, or into insulators like silica). In this work a new method for the preparation of single Quantum Dots (QDs) in silica spheres with tunable size and optical property has been developed by a novel approach. The work is based on a water in oil microemulsion system. A time interval addition of silica precursors has been used to increase the size of the silica shell and in parallel tuning the photoluminescence properties of the resulting CdSe/ZnS/SiO2 nanocomposites. Characterization was performed by transmission electron microscopy, photoluminescence spectroscopy and zeta-potential measurements. For the different applications of silica coated core–shell nanoparticles, the control over the silica shell thickness as well as the tuning of the optical properties is required. Therefore our study could open new possibilities of applications for this nanocomposites in different fields like photonic crystals, biolabeling, biosensing etc..
Kieninger J, Marx A, Spies F, Weltin A, Urban G A, Jobst G
pH Micro Sensor with Micro-ﬂuidic Liquid-junction Reference Electrode On-chip for Cell Culture Applications
2009 IEEE SENSORS 2009 Conference

2008

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Vulto P, Kuhn P, Urban G
A Micro-Electrophoresis Cell With Integrated Bubble-Free Electrodes
2008 MSB 2008/Berlin , Band: 2, Seite: 271
Vulto P, Zahn P, Dame G, Urban G
Automated RNA isolation on-a-chip
2008 BioSensors 2008 Proc. BioSensors 2008, Seite: O62
Kahlert U, Kieninger J, Papazoglou A, Urban G, Nikkah G
Characterisation of menchymal stem cells (MSC)
2008
Yuan Y, Riehle F, Urban G, Krueger M
Critical Parameters for Nanocrystal Synthesis: Impurities, Thermal Fluctuation and Injection Rate
2008 Nanax 3 Conference: Nanoscience with nanocrystals
KurzfassungThe spectroscopic properties of semiconducting nanocrystals (NCs) strongly depend on the synthesis conditions which includes the quality of the chemicals. We developed a novel approach allowing the preparation of NCs with a high control over chemical and physical parameters. Here we report about the effects of impurities, thermal fluctuation and the injection rate on the photoluminescence behaviour of CdSe NCs.
Hussein L, Urban G, Krueger M
Novel Ultra-Small Nanoparticles on Nanotube Buckypaper as Electrocatalyst for Implantable Glucose Fuel Cells
2008 Faraday Discussion 140: Electrocatalysis, University of Southampton, GB
Cubukcu A, Urban G
Sensitivity-Maximizing and Error-Reducing Design of a Flow and Thermal Property Sensor
2008 IEEE EuroSimE, Freiburg (Germany) , Seiten: 147 - 152
Vulto P, Kuhn P, Urban G
Silver/Silver Chloride Electrodes For Bubble-Free Actuation In A Micro-Electrophoresis Cell
2008 BioSensors 2008/ Shanghai, China , Seite: 139
Vulto P, Kohlheyer D, Urban G, Schasfoort R B M
Sweeping Flow Electrophoresis (SFE): a New Continuous Separation Technique
2008 microTAS/ San Diego, USA Proc. microTAS, Seiten: 823 - 825

2007

nach oben zur Jahresübersicht

Kieninger J, Dannenberg A, Aravindalochanan K, Jobst G, Pettersen E O, Urban G A
Amperometric oxygen sensor array with novel chronoamperometric protocols
2007 Transducers 2007/Eurosensors XXI/ Lyon, France Proc. of Transducers `07/Eurosensors XXI; Vol. 2, Band: 2, Seiten: 1907 - 1910
Vulto P, Igel G, Urban G
Full Waver fabrication process for microfluidic glass chips with electroplated electrodes
2007 Transducers '07/Eurosensors XXI/ Lyon, France Proc. Transducers '07/Eurosensors XXI
Vulto P, Weidmann M, Klaunick C, Urban G A
Fully automated RNA extraction on-a.chip by combined thermoelectric lysis and eletrophoretic purification
2007 BMT/Aachen , Ergänzungsband: 15690507
Ledernez L, Olcaytug F, Urban G, Yasuda H
Magnetron Design for AF Plasma Polymerisation of Dielectric Films
2007 ISPC-18, Kyoto, Japan
Aravindalochanan K, Kieninger J, Jobst G, Igel G, Urban G A
Micro Electrode Array for Sensing Nitric Oxide in Hypoxic Cell Culture Environment
2007 IEEE Sensors, Atlanta (USA) , Band: 1, Seiten: 111 - 116
Fleischauer B, Mueller C, Reinecke H, Kloke A, Rubenwolf S, Stetten F von, Zengerle R, Schuh K, Schlipf C, Prucker O, Rühe J, Krüger M, Woias P
MikroSystemTechnik KONGRESS 2007
2007 Mikrosystemtechnik Kongress 2007 in Dresden GMM, VDE, VDI
Ledernez L, Yasuda H, Olcaytug F, Urban G
Surface-State Electron Transfer: an Alternative Breakdown Model
2007 IVC-17, Stockholm, Sweden
Yasuda H, Ledernez L, Olcaytug F, Urban G
Surface-state Equilibration Principle in Dielectric Breakdown of Gas Phase
2007 IVC-17, Stockholm, Sweden

2006

nach oben zur Jahresübersicht

Ledernez L, Yasuda H, Olcaytug F, Urban G
Pressure Dependence of Plasma Polymerization of Methane at Constant W/FM
2006 PSE 2006, Garmisch, Germany

2005

nach oben zur Jahresübersicht

Woias P, Manoli Y, Nann T, von Stetten F
Energy Harvesting for Autonomous Microsystems
2005 NanoEurope, St-Gallen (Switzerland)
Kieninger J, Aravindalochanan K, Jobst G, Igel G, Urban G
Electro Chemical Oxygen Sensor Array for Hypoxic Environment
2005 Sensors, Nürnberg, Germany Sensors Proceedings, Band: II, Seiten: 259 - 262

Festschriften

Jahre: 2010

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2010

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Krueger M
Nanotechnologie im Fokus
2010 FMF Festschrift zum 20 jährigem Bestehen des FMF, Seiten: 56 - 62

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2020

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Behrmann O, Bachmann I, Hufert F, Dame G
Schnellnachweis von SARS-CoV-2 mit recombinase polymerase amplification
BIOSpektrum, 2020

2019

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Bucher V, Weinmann M, Bergmann M, Stieglitz T, Urban G
Polymere Barriereschichten für Elektronik in harscher Umgebung
WOMag, Band: 6, 2019

2011

nach oben zur Jahresübersicht

Gueder F, Yang Y, Krueger M, Stevens G, Zacharias M
A Novel approach for the fabrication of sub-100nm planar nanochannels and applications to template assisted material nanosythesis
Posterbeitrag MRS Sanf Francisco 2011, 2011
Stevens G, Zgaga-Griesz A, Silver D, Urban G, Krueger M
An Assay for Automated Rapid, Sensitive Detection of Clostridium botulinum Neurotoxin in the Field
Medical Biodefecnee Conference 2011, 25-28 Oct 2011, Munich, Germany, Poster presentation, best poster award (2nd prize), 2011
Krueger M, Einwaechter S, Yuan Y
Automated synthesis of nanomaterials at Freiburg Materials Research Center (FMF)
http://www.youtube.com/watch?v=mxAI_G0sT8c, 2011
Krueger M, Einwaechter S, Yuan Y
BW-eLabs: Automated Synthesis of Nanoparticles
, 2011
Zhou Y, Eck M, Krueger M
Polymer-Inorganic Hybrid Materials for Light Harvesting and Photovoltaic Applications in Hybrid Solar Cells
Light Harvesting Processes LHP Conference, Banz Monastery April 10-14, 2011, - Poster presentation-, 2011

2010

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Krueger M, Zhou Y, Eck M
Elektrizität aus Sonnenlicht
Labor Praxis, Band: Juni 2010, 2010

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