List of Publications Dr. Peter Koltay

• Journal Articles
• Reviews
• Book chapters
• Short communications
• Talks
• Conference papers
• Other publications

Journal Articles

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2025

• D. Straubinger, P. Koltay, R. Zengerle, S. Kartmann, Z. Shu
  Versatile Selective Soldering via Molten Metal Printing for Heat-Sensitive 3D Electronics and Smart Wearables
  2025 Adv. Funct. Mater., page: 2419653

2024

• V. Zieger, E. Woehr, S. Zimmermann, D. Frejek, P. Koltay, R. Zengerle, S. Kartmann
  Automated Nanodroplet Dispensing for Large-Scale Spheroid Generation via Hanging Drop and Parallelized Lossless Spheroid Harvesting
  2024 Micromachines, volume: 15, page: 231
• D. Straubinger, P. Koltay, R. Zengerle, S. Kartmann, Z. Shu
  Bulge-Free and Homogeneous Metal Line Jet Printing with StarJet Technology
  2024 Micromachines, volume: 15, page: 743
• Z. Khan, D. Gururajan, P. Koltay, S. Kartmann, R. Zengerle, Z. Shu
  Hybrid 3D Printing of Molten Metal Microdroplets and Polymers for Prototyping of Printed Circuit Boards Featuring Interdigitated 3D Capacitors
  2024 EEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, IEEJ Trans 2024
• Z. Khan, A. Saphala, S. Kartmann, P. Koltay, R. Zengerle, O. Amft, Z. Shu
  Hybrid Printing of Conductive Traces from Bulk Metal for Digital Signals in Intelligent Device
  2024 Micromachines, volume: 15, page: 750
• Z. Khan, D. Gururajan, S. Kartmann, P. Koltay, R. Zengerle, Z. Shu
  Iterative printing of bulk metal and polymer for additive manufacturing of multi-layer electronic circuits
  2024 npj Adv. Manuf., volume: 1, issue: 1
• V. Zieger, D. Frejek, S. Zimmermann, G. A. A. Miotto, P. Koltay, R. Zengerle, S. Kartmann
  Towards Automation in 3D Cell Culture: Selective and Gentle High-Throughput Handling of Spheroids and Organoids via Novel Pick-Flow-Drop Principle
  2024 Adv Healthc Mater, page: e2303350

2023

• J. Weygant, F. Koch, K. Adam, K. Tröndle, R. Zengerle, G. Finkenzeller, S. Kartmann, P. Koltay, S. Zimmermann
  A Drop-on-Demand Bioprinting Approach to Spatial Arrangement of Multiple Cell Types and Monitoring Their Cell–Cell Interactions towards Vascularization Based on Endothelial Cells and Mesenchymal Stem Cells
  2023 Cells, volume: 12, issue: 4, page: 646
• P. Sardana, M. Zolfaghari, G. Miotto, R. Zengerle, T. Brox, P. Koltay, S. Kartmann
  DropletAI: Deep Learning-Based Classification of Fluids with Different Ohnesorge Numbers during Non-Contact Dispensing
  2023 Fluids, volume: 8, page: 183
• D. Grijalva Garces, S. Strauß, S. Gretzinger, B. Schmieg, T. Jüngst, J. Groll, L. Meinel, I. Schmidt, H. Hartmann, K. Schenke-Layland, N. Brandt, M. Selzer, S. Zimmermann, P. Koltay, A. Southan, G. E. M. Tovar, S. Schmidt, A. Weber, T. Ahlfeld, M. Gelinsky, T. Scheibel, R. Detsch, A. R. Boccaccini, T. Naolou, C. Lee-Thedieck, C. Willems, T. Groth, S. Allgeier, B. Köhler, T. Friedrich, H. Briesen, J. Buchholz, D. Paulus, A. von Gladiss, J. Hubbuch
  On the reproducibility of extrusion-based bioprinting: round robin study on standardization in the field
  2023 Biofabrication, volume: 16, page: 015002
• Z. Khan, P. Koltay, R. Zengerle, S. Kartmann, Z. Shu
  One-Stop Hybrid Printing of Bulk Metal and Polymer for 3D Electronics
  2023 Advanced Engineering Materials, page: 2300922
• V. Zieger, D. Frejek, S. Zimmermann, G. A. A. Miotto, P. Koltay, R. Zengerle, S. Kartmann
  Towards Label-Free Standardization in 3d Cell Culture: Automated, Selective and Gentle High-Throughput Handling of Spheroids and Organoids via Novel Pick-Flow-Drop Principle
  2023 Adv Healthc Mater, page: e2303350

2022

• K. Tröndle, G. Miotto, L. Rizzo, R. Pichler, F. Koch, P. Koltay, R. Zengerle, S. S. Lienkamp, S. Kartmann, S. Zimmermann
  Deep Learning-Assisted Nephrotoxicity Testing with Bioprinted Renal Spheroids
  2022 Int. J. Bioprint, volume: 8, issue: 2, page: 528
• V. Burchak, F. Koch, L. Siebler, S. Haase, V. K. Horner, X. Kempter, G. B. Stark, U. Schepers, A. Grimm, S. Zimmermann, P. Koltay, S. Strassburg, G. Finkenzeller, F. Simunovic, F. Lampert
  Evaluation of a Novel Thiol–Norbornene-Functionalized Gelatin Hydrogel for Bioprinting of Mesenchymal Stem Cells
  2022 Int. J. Mol. Sci., volume: 23, page: 7939
• F. Koch, O. Thaden, S. Conrad, K. Tröndle, G. Finkenzeller, R. Zengerle, S. Kartmann, S. Zimmermann, P. Koltay
  Mechanical properties of polycaprolactone (PCL) scaffolds for hybrid 3D-bioprinting with alginate-gelatin hydrogel
  2022 J. Mech. Behav. Biomed. Mat., volume: 130, page: 105219
• S. Hennig, Z. Shu, L. Gutzweiler, P. Koltay, F. von Stetten, R. Zengerle, S. M. Früh
  Paper-based open microfluidic platform for protein electrophoresis and immunoprobing
  2022 Electrophoresis, volume: 43, issue: 4, pages: 621 - 631

2021

• T. Gross, C. Jeney, D. Halm, G. Finkenzeller, G. B. Stark, R. Zengerle, P. Koltay, S. Zimmermann
  Characterization of CRISPR/Cas9 RANKL knockout mesenchymal stem cell clones based on single-cell printing technology and Emulsion Coupling assay as a low-cellularity workflow for single-cell cloning
  2021 Plos One, volume: 16, issue: 3, page: e0238330
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  Abstract

  The homogeneity of the genetically modified single-cells is a necessity for many applications such as cell line development, gene therapy, and tissue engineering and in particular for regenerative medical applications. The lack of tools to effectively isolate and characterize CRISPR/Cas9 engineered cells is considered as a significant bottleneck in these applications. Especially the incompatibility of protein detection technologies to confirm protein expression changes without a preconditional large-scale clonal expansion creates a gridlock in many applications. To ameliorate the characterization of engineered cells, we propose an improved workflow, including single-cell printing/isolation technology based on fluorescent properties with high yield, a genomic edit screen (Surveyor assay), mRNA RT-PCR assessing altered gene expression, and a versatile protein detection tool called emulsion-coupling to deliver a high-content, unified single-cell workflow. The workflow was exemplified by engineering and functionally validating RANKL knockout immortalized mesenchymal stem cells showing bone formation capacity of these cells. The resulting workflow is economical, without the requirement of large-scale clonal expansions of the cells with overall cloning efficiency above 30% of CRISPR/Cas9 edited cells. Nevertheless, as the single-cell clones are comprehensively characterized at an early, highly parallel phase of the development of cells including DNA, RNA, and protein levels, the workflow delivers a higher number of successfully edited cells for further characterization, lowering the chance of late failures in the development process.
• F. Koch, O. Thaden, K. Tröndle, R. Zengerle, S. Zimmermann, P. Koltay
  Open-source hybrid 3D-bioprinter for simultaneous printing of thermoplastics and hydrogels
  2021 HardwareX, volume: 10, page: e00230

2020

• Z. Shu, M. Fechtig, F. Lombeck, M. Breitwieser, Roland Zengerle, Peter Koltay
  Direct Drop-on-Demand Printing of Molten Solder Bumps on ENIG Finishing at Ambient Conditions through StarJet Technology
  2020 IEEE Access, volume: 8, pages: 210225 - 210233
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  Abstract

  In this paper, we report on a detailed experimental study carried out with the StarJet technology to investigate the mechanical adhesion properties of directly printed solder bumps on electroless nickel immersion gold (ENIG) plated PCB boards. The aim of this study is to determine the maximum bond strength achievable by this method and to find suitable printing parameters that allow for the production of reliable and consistent solder bumps by non-contact printing of molten solder (type SAC305). Molten solder droplets of about 250 μm diameter were printed at melt temperatures between 250 and 400 °C onto ENIG surfaces kept at temperatures in the range of 100 to 200 °C. Using shear force tests, the adhesion of the printed bumps was investigated as a function of the main process parameters: 1. printhead temperature, 2. substrate temperature, and 3. substrate preheating time. The formation of an intermetallic compound (IMC) between the solder and the ENIG was confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) measurements. As a result of the comprehensive experimental parameter study, suitable printing parameters for establishing bond strengths corresponding to maximum shear force values of 3000 to 4000 mN could be found, i.e. high printhead temperature of 400 °C, short preheating and time of < 2 min, and substrate heating at 180 °C The use of flux was found to slightly improve the bond strength and to improve the consistency of the printing results for extended operation times. The achieved high bond strength and the reasonable reproducibility of the printing results qualify the StarJet technology for further investigations regarding applications in the field of direct soldering of microelectronic chips and devices to PCB boards as well as other micro-assembly tasks in the future.
• F. Koch, K. Tröndle, G. Finkenzeller, R. Zengerle, S. Zimmermann, P. Koltay
  Generic method of printing window adjustment for extrusion-based 3D-bioprinting to maintain high viability of mesenchymal stem cells in an alginate-gelatin hydrogel
  2020 Bioprinting, page: e00094
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  Abstract

  Over the last decade, bioprinting of artificial tissues has been developed into a significant field of research. With an increasing number of printing technologies and bioinks used in bioprinting, its complexity increases as both the printing technology and the properties of the bioink influence the cell biological functionality and printing accuracy of the printed tissue. Therefore, optimization of bioprinting processes often remains a challenge, which could be solved by a smart fine-tuning of the process parameters. We present a novel method to adjust the printing window for extrusion-based bioprinting on the basis of a two-step assessment to determine process parameters such as nozzle size, extrusion flow rate, and printing temperature. First, a suitable printing temperature is deduced from the bioink properties and second nozzle size and extrusion flow rate is selected in a way that the immediate cell damage after printing is reduced. For both steps only basic rheological properties of the bioinks need to be known as well as detailed knowledge of the cell survival in the bioink for different shear stresses. This method is applied to an exemplary alginate-gelatin hydrogel to show how the printing temperature affects the achievable printing accuracy. For this bioink, viability of immortalized mesenchymal stem cells (iMSC) decreases with about 4% per thousand Pascal increase in maximum shear stress. For different combinations of flow rate, nozzle size and nozzle shape it is shown, that only the maximum shear stress experienced by the iMSCs influences average cell viability. Factors like flow rate, nozzle size and shape only play an indirect role by influencing the maximum shear stress and individually have no significant influence on cell viability. The experimental results allow a direct adjustment of printing parameters for the presented combination of hydrogel and cell type but are not limited to it. For other bioinks, the described generic method can be easily used to systematically adjust the printing parameters. For this purpose, only the basic rheological properties and the influence of shear stress on cell survival need to be known and process parameters can be set concerning the respective application.
• P. Rukavina, F. Koch, M. Wehrle, K. Tröndle, G. B. Stark, P. Koltay, S. Zimmermann, R. Zengerle, F. Lampert, S. Strassburg, G. Finkenzeller, F. Simunovic
  In vivo evaluation of bioprinted prevascularized bone tissue
  2020 Biotechnol Bioeng, pages: 1 - 10
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  Abstract

  Bioprinting can be considered as a progression of the classical tissue engineering approach, in which cells are randomly seeded into scaffolds. Bioprinting offers the advantage that cells can be placed with high spatial fidelity within three‐dimensional tissue constructs. A decisive factor to be addressed for bioprinting approaches of artificial tissues is that almost all tissues of the human body depend on a functioning vascular system for the supply of oxygen and nutrients. In this study, we have generated cuboid prevascularized bone tissue constructs by bioprinting human adipose‐derived mesenchymal stem cells (ASCs) and human umbilical vein endothelial cells (HUVECs) by extrusion‐based bioprinting and drop‐on‐demand (DoD) bioprinting, respectively. The computer‐generated print design could be verified in vitro after printing. After subcutaneous implantation of bioprinted constructs in immunodeficient mice, blood vessel formation with human microvessels of different calibers could be detected arising from bioprinted HUVECs and stabilization of human blood vessels by mouse pericytes was observed. In addition, bioprinted ASCs were able to synthesize a calcified bone matrix as an indicator of ectopic bone formation. These results indicate that the combined bioprinting of ASCs and HUVECs represents a promising strategy to produce prevascularized artificial bone tissue for prospective applications in the treatment of critical‐sized bone defects.
• J. Riba, J. Schoendube, S. Zimmermann, P. Koltay, R. Zengerle
  Single-cell dispensing and ‘realtime’cell classification using convolutional neural networks for higher efficiency in single-cell cloning
  2020 nature scientific reports, volume: 10, page: 1193
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  Abstract

  Single-cell dispensing for automated cell isolation of individual cells has gained increased attention in the biopharmaceutical industry, mainly for production of clonal cell lines. Here, machine learning for classification of cell images is applied for ‘real-time’ cell viability sorting on a single-cell printer. We show that an extremely shallow convolutional neural network (CNN) for classification of lowcomplexity cell images outperforms more complex architectures. Datasets with hundreds of cell images from four different samples were used for training and validation of the CNNs. The clone recovery, i.e. the fraction of single-cells that grow to clonal colonies, is predicted to increase for all the samples investigated. Finally, a trained CNN was deployed on a c.sight single-cell printer for ‘real-time’ sorting of a CHO-K1 cells. On a sample with artificially damaged cells the clone recovery could be increased from 27% to 73%, thereby resulting in a significantly faster and more efficient cloning. Depending on the classification threshold, the frequency at which viable cells are dispensed could be increased by up to 65%. This technology for image-based cell sorting is highly versatile and can be expected to enable cell sorting by computer vision with respect to different criteria in the future.

2019

• K. Tröndle, F. Koch, G. Finkenzeller, G. B. Stark, R. Zengerle, P. Koltay, S. Zimmermann
  Bioprinting of high cell density constructs leads to controlled lumen formation with self‐assembly of endothelial cells
  2019 Journal of Tissue Engineering and Regenerative Medicine, volume: 13, issue: 10, pages: 1883 - 1895
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  Abstract

  Active nutrient supply and waste product removal are key requirements for the fabrication of long term viable and functional tissue constructs of considerable size. This work aims to contribute to the fabrication of artificial perfusable networks with a bioprinting process, based on drop‐on‐demand (DoD) printing of primary endothelial cell (EC) suspension bioink (25 · 106 ± 3 · 106 cells/ml). The process results in prescribed lumen between two hydrogel layers, allowing its integration in common layering based bioprinting processes. Low volume bioink droplets (appr. 10 nl) as building blocks, were deposited between two fibrin or collagen I layers to realize shapeable, cell‐rich aggregates. Unattainable with manual positioning, DoD printing allowed precise fabrication of various designs, such as spheroidal‐, line‐shaped and Y‐branch cellular structures, with a mean lateral extension of 285 ± 81 μm. For basic characterization, the cell suspension building blocks were systematically compared to preformed spheroids of the same cell type, passage and number. Post printing investigations of initially loose cell arrangements showed self‐assembly and formation of central lumen with a mean cross‐sectional area of Ølumen = 6400 μm2 at day 3, lined by a single layer of CD31 positive ECs, as evaluated by confocal microscopy. Originating from this main lumen smaller, undirected side‐branches (Øbranches = 740 μm2) were formed by sprouting cells, inducing a first step towards a simplistic hierarchically organized network. These lumen could prospectively help for tissue construct perfusion in vitro or, potentially, as niche for angiogenesis of host vascularization in implants.
• M. Wehrle, F. Koch, S. Zimmermann, P. Koltay, R. Zengerle, G. B. Stark, S. Strassburg, G. Finkenzeller
  Examination of Hydrogels and Mesenchymal Stem Cell Sources for Bioprinting of Artificial Osteogenic Tissues
  2019 Cellular and Molecular Bioengineering, pages: 1 - 15
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  Abstract

  Mesenchymal stem cells (MSCs) represent a very important cell source in the field of regenerative medicine and for bone and cartilage tissue engineering applications. Three-dimensional (3D) bioprinting has the potential to improve the classical tissue engineering concept as this technique allows the printing of cells with high spatial control of cell allocation within a 3D construct. In this study, we systematically compared different hydrogel blends for 3D bioprinting of MSCs by testing their cytocompatibility, ability to support osteogenic differentiation and their mechanical properties. In addition, we compared four different MSC populations isolated from different human tissues for their osteogenic differentiation capacity in combination with different hydrogels. The aim of this study was to identify the best MSC source and the most suitable hydrogel blend for extrusion-based bioprinting of 3D large-scaled osteogenic constructs.

2018

• B. Gerdes, M. Breitwieser, T. Kaltenbach, M. Jehle, J. Wilde, R. Zengerle, P. Koltay, L. Riegger
  Analysis of the metallic structure of microspheres produced by printing of aluminum alloys from the liquid melt
  2018 Mater Res Express, volume: 6, page: 036514
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  Abstract

  This work presents an analysis of the metallic structure of microspheres produced by drop-on-demand printing of the aluminum alloy AlSi12 directly printed from the liquid melt via StarJet technology. AlSi alloys are commonly used in casting processes, but microdroplets from these materials could potentially be used for additive manufacturing of metal and composite parts. Recently, several printing technologies were presented that enable the drop-on-demand printing of Al-alloy microdroplets. However, the material distribution and metallic structure inside of printed droplets is expected to be significantly different from the bulk material properties, and hardly any data on the microscopic structure of small droplets that have undergone rapid solidification has been published so far. Therefore, a microscopic in-depth study of microdroplets printed directly from the metal melt has been carried out: By the means of energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and optical microscopy the material properties as well as the droplet morphology are investigated for the first time. The analysis demonstrates that the Al alloy droplets printed via StarJet technology exhibit almost no oxidation during the printing process and can therefore potentially be used for additive manufacturing of metal parts. Moreover, the metallurgical structure inside the droplets is analyzed. It exhibits significant difference to the bulk material in terms of the average secondary dendrite arm spacing.
• C.H. Tsai, X. Wu, D.H. Kuan, S. Zimmermann, R. Zengerle, P. Koltay
  Digital hydraulic drive for microfluidics and miniaturized cell culture devices based on shape memory alloy actuators
  2018 J Micromech Microeng, volume: 28, page: 084001
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  Abstract

  In order to culture and analyze individual living cells, microfluidic cell culture and manipulation of cells becomes an increasingly important topic. Such microfluidic systems allow for exploring the phenotypic differences between thousands of genetically identical cells or pharmacological tests in parallel, which is impossible to achieve by traditional macroscopic cell culture methods. Therefore, plenty of microfluidic devices have been developed for cell biological studies like cell culture, cell sorting, and cell lysis in the past. However, these devices are still limited by the external pressure sources which most of the time are large in size and have to be connected by fluidic tubing leading to complex and delicate systems.&#13; In order to provide a miniaturized, more robust actuation system a novel, compact and low power consumption Digital Hydraulic Drive (DHD) has been developed that is intended for use in portable and automated systems for microfluidic applications. The DHD consists of a shape memory alloy (SMA) actuator and a pneumatic cylinder. The switching time of the digital modes (pressure ON vs. OFF) can be adjusted from 1 second to minutes. Thus, the DHDs might have many applications for driving microfluidic devices. In this work different implementations of DHDs are presented and their performance is characterized by experiments. In particular, it will be shown that DHDs can be used for microfluidic large-scale integration (mLSI) valve control (256 valves in parallel) as well as potentially for droplet-based microfluidic systems. As further application example high-throughput mixing of cell cultures (96 wells in parallel) are demonstrated employing the DHD and a so called "functional lid" (FL) approach, to enable a miniaturized microbioreactor in a regular 96-well micro well plate.
• B. Gerdes, R. Zengerle, P. Koltay, L. Riegger
  Direct printing of miniscule aluminum alloy droplets and 3D structures by StarJet technology
  2018 J Micromech Microeng, volume: 28, page: 074003
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  Abstract

  Drop-on demand printing of molten metal droplets could be used for prototyping of 3D objects as promising alternative to laser melting technologies. However, up to date only few printheads were investigated for this purpose using only a limited range of materials. The pneumatically actuated StarJet technology presented previously enables the direct and non-contact printing of molten metal microdroplets from metal melts at high temperatures. Printheads according to the StarJet technology utilize nozzle chips featuring a star-shaped orifice geometry that leads to a formation of the droplets inside the nozzle with high precision. In this paper we present a novel StarJet printhead for printing aluminum alloys featuring a hybrid design with a ceramic reservoir for the molten metal and an outer shell fabricated from stainless steel. The micro machined nozzle chip is made from silicon carbide (SiC). This printhead can be operated at up to 950 °C and is capable of printing high melting metals like aluminum (Al) alloys in standard laboratory conditions. In this work, an aluminum-silicon alloy that features 12 % silicon (AlSi12) is printed. The printhead, the nozzle and the peripheral actuation system have been optimized for stable generation of AlSi12 droplets with high monodispersity, low angular deviation and miniaturized droplet diameters. As main result, a stable drop-on-demand printing of droplets exhibiting diameters of ddroplet = 702 µm +/- 1 % was demonstrated at 5 Hz with a low angular deviation of 0.3°, when a nozzle chip with 500 µm orifice diameter was used. Further, AlSi12 droplets featuring ddroplet = 176 µm ± 7 % were printed when using a nozzle chip with an orifice diameter of 130 µm. Moreover, we present directly printed objects from molten aluminum alloy droplets such as high aspect ratio, free-standing walls (aspect ratio 12:1) and directly printed, flexible springs to demonstrate the principle of 3D printing with molten metal droplets.
• B. Gerdes, M. Jehle, N. Lass, L. Riegger, A. Spribille, M. Linse, F. Clement, R. Zengerle, P. Koltay
  Front side metallization of silicon solar cells by direct printing of molten metal
  2018 Solar Energy Materials and Solar Cells, volume: 180, pages: 83 - 90
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  Abstract

  In this work, a new approach for the front side metallization of silicon solar cells is presented. Molten solder (Sn96Ag3Cu) is directly printed in a non-contact manner on solar cell precursors via StarJet technology. The StarJet technology features a pneumatically driven, heatable printhead with a reservoir of molten metal and a star-shaped silicon nozzle chip. Using this printhead, a jet of molten metal with 55 μm ± 5 μm diameter is generated and used to apply busbars as well as contact fingers on prefabricated electroplated seed layers. After deposition via StarJet, printed fingers have a minimum width of 70 μm and a mean aspect ratio of 0.94. The printed metallization is evaluated optically and electrically. Aluminum back surface field silicon solar cells with front side electroplated NiAg seed layers and StarJet metallization (busbars and fingers) show efficiencies of up to 18.1% after degradation. Solder is about 30–40 times cheaper than silver and therefore may allow costefficient solar cell metallization. The StarJet metallization on electroplated NiAg seed layers is fully functional and requires no additional post-processing steps. Only 6 mg of Ag per cell are consumed for the seed layer. As a proof-of-principle, a module is demonstrated, which consists of four solar cells that are metallized via StarJet.

2017

• L. Benning, L. Gutzweiler, K. Tröndle, J. Riba, R. Zengerle, P. Koltay, S. Zimmermann, G. B. Stark, G. Finkenzeller
  Assessment of hydrogels for bioprinting of endothelial cells
  2017 J Biomed Mater Res A, pages: 935 - 947
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  Abstract

  In tissue engineering applications, vascularization can be accomplished by co-implantation of tissue forming cells and endothelial cells (ECs), whereby the latter are able to form functional blood vessels. The use of three-dimensional (3D) bioprinting technologies has the potential to improve the classical tissue engineering approach because these will allow the generation of scaffolds with high spatial control of endothelial cell allocation. This study focuses on a side by side comparisons of popular commercially available bioprinting hydrogels (matrigel, fibrin, collagen, gelatin, agarose, Pluronic F-127, alginate and alginate/gelatin) in the context of their physicochemical parameters, their swelling/degradation characteristics, their biological effects on vasculogenesis-related EC parameters and their printability. The aim of this study was to identify the most suitable hydrogel or hydrogel combination for inkjet printing of ECs to build pre-vascularized tissue constructs. Most tested hydrogels displayed physicochemical characteristics suitable for inkjet printing. However, Pluronic F-127 and the alginate/gelatin blend were rapidly degraded when incubated in cell culture medium. Agarose, Pluronic F-127, alginate and alginate/gelatin hydrogels turned out to be unsuitable for bioprinting of ECs because of their non-adherent properties and/or their incapability to support EC proliferation. Gelatin was able to support EC proliferation and viability but was unable to support endothelial cell sprouting. Our experiments revealed fibrin and collagen to be most suitable for bioprinting of ECs, because these hydrogels showed acceptable swelling/degradation characteristics, supported vasculogenesis-related EC parameters and showed good printability. Moreover, ECs in constructs of preformed spheroids survived the printing process and formed capillary-like cords.
• T. Gleichmann, A. Rostas, J. Wörner, E. Schleicher, L. Gutzweiler, B. Hamouda, R. Zengerle, P. Koltay, L. Riegger
  Atmospheric Photopolymerization of Acrylamide Enabled by Aqueous Glycerol Mixtures: Characterization and Application for Surface-Based Microfluidics
  2017 Macromol Mater Eng, page: 1600518
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  Abstract

  Polyacrylamide usually is the material of choice for electrophoretic separation in slab gels, capillaries, and microfluidic devices. So far its polymerization requires anaerobic environments because oxygen impurities inhibit or even terminate the polymerization reaction of acrylamide. Here, it is demonstrated that gel precursor solutions with glycerol contents above 20 vol% enable direct atmospheric photopolymerization of acrylamide with no need for sealing or degassing the solution in advance. The positive effect of glycerol on the polymerization reaction is proven by simulation-validated electron paramagnetic resonance measurements. Nuclear magnetic resonance reveals that glycerol does not interfere with the reaction indicating that the observed enhancement in polymerization is owed to the low oxygen solubility of aqueous glycerol mixtures. Glycerol concentrations of >60 vol% in the gel precursor solution enable complete polymerization of volumes down to 5 nL within less than 5 s. This enables using liquid handling robots to fabricate channel-free open microfluidic structures of solid polyacrylamide hydrogel in a low-cost automated manner in a standard lab environment.
• L. Benning, L. Gutzweiler, K. Tröndle, J. Riba, R. Zengerle, P. Koltay, S. Zimmermann, G.B. Stark, G. Finkenzeller
  Cytocompatibility testing of hydrogels toward bioprinting of mesenchymal stem cells
  2017 J Biomed Mater Res A, volume: 105, pages: 3231 - 3241
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  Abstract

  Mesenchymal stem cells (MSCs) represent a very attractive cell source for tissue engineering applications aiming at the generation of artificial bone substitutes. The use of three-dimensional bioprinting technologies has the potential to improve the classical tissue engineering approach because bioprinting will allow the generation of hydrogel scaffolds with high spatial control of MSC allocation within the bioprinted construct. In this study, we have performed direct comparisons between commercially available hydrogels in the context of their cytocompatibility toward MSCs and their physicochemical parameters with the aim to identify the most suitable hydrogel for drop-on-demand (DoD) printing of MSCs. In this context, we examined matrigel, fibrin, collagen, gelatin, and gelatin/alginate at various hydrogel concentrations. Matrigel, fibrin, collagen, and gelatin were able to support cell viability, but the latter showed a limited potential to promote MSC proliferation. We concentrated our study on fibrin and collagen hydrogels and investigated the effect of hydroxyapatite (HA) inclusion. The inclusion of HA enhanced proliferation and osteogenic differentiation of MSCs and prevented degradation of fibrin in vitro. According to viscosity and storage moduli measurements, HA-blends displayed physicochemical characteristics suitable for DoD printing. In bioprinting experiments, we confirmed that fibrin and collagen and their respective HA-blends represent excellent hydrogels for DoD-based printing as evidenced by high survival rates of printed MSCs.
• L. Gutzweiler, S. Kartmann, K. Troendle, L. Benning, G. Finkenzeller, R. Zengerle, P. Koltay, B. Stark, S. Zimmermann
  Large scale production and controlled deposition of single HUVEC spheroids for bioprinting applications
  2017 Biofabrication, volume: 9 (2), page: 02502
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  Abstract

  We present 1.) a fast and automated method for large scale production of HUVEC spheroids based on the hanging drop method and 2.) a novel method for well-controlled lateral deposition of single spheroids by drop-on-demand printing. Large scale spheroid production is achieved via printing 1536 droplets of HUVEC cell suspension having a volume of 1 µl each within 3 minutes at a pitch of 2.3 mm within an array of 48 x 32 droplets onto a flat substrate. Printing efficiencies between 97.9% and 100% and plating efficiencies between 87.3% and 100% were achieved. Harvested spheroids (consisting of approx. 250 HUVECs each) appear uniform in size and shape. After incubation and harvesting, the spheroids are deposited individually in user-defined patterns onto hydrogels using an automated drop-on-demand dispenser setup. Controlled by an image detection algorithm focusing the dispenser nozzle, droplets containing exactly one spheroid are printed onto a substrate, while all other droplets are discarded. Using this approach an array of 6 x 3 HUVEC spheroids with intermediate distances of 500 µm embedded in fibrin was generated. Successful progress of spheroid sprouting and merging of neighboring sprouts was observed during the first 72 hours of incubation indicating a good viability of the deposited spheroids.
• L. Gutzweiler, T. Gleichmann, L. Tanguy, P. Koltay, R. Zengerle, L. Riegger, , ,
  Open microfluidic gel electrophoresis: Rapid and low cost separation and analysis of DNA at the nanoliter scale
  2017 Electrophoresis, volume: 38, pages: 1764 - 1770
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  Abstract

  Gel electrophoresis is one of the most applied and standardized tools for separation and analysis of macromolecules and their fragments in academic research and in industry. In this work we present a novel approach for conducting on-demand electrophoretic separations of DNA molecules in open microfluidic (OM) systems on planar polymer substrates. The approach combines advantages of slab gel, capillary- & chip-based methods offering low consumable costs (< 0.1 $) circumventing cost intensive microfluidic chip fabrication, short process times (5 minutes per analysis) and high sensitivity (4 ng/µl dsDNA) combined with reasonable resolution (17 bases). The open microfluidic separation system comprises two opposing reservoirs of 2-4 µl in volume, a semi-contact written gel line acting as separation channel interconnecting the reservoirs and sample injected into the line via non-contact droplet dispensing and thus enabling the precise control of the injection plug and sample concentration. Evaporation is prevented by covering aqueous structures with PCR-grade mineral oil while maintaining surface temperature at 15°C. The liquid gel line exhibits a semi-circular cross section of adaptable width (~200-600 µm) and height (~30-80 µm) as well as a typical length of 15-55 mm. Layout of such liquid structures is adaptable on-demand not requiring time consuming and repetitive fabrication steps. The approach was successfully demonstrated by the separation of a standard label-free DNA ladder (100-1000 bp) at 100 V/cm via in-line staining and laser induced fluorescent end-point detection using an automated prototype.

2016

• J. Riba, T. Gleichmann, S. Zimmermann, R. Zengerle, P. Koltay
  Label-free isolation and deposition of single bacterial cells from heterogeneous samples for clonal culturing
  2016 Scientific Reports, volume: 6, page: 32837
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  Abstract

  The isolation and analysis of single prokaryotic cells down to 1 μm and less in size poses a special challenge and requires micro-engineered devices to handle volumes in the picoliter to nanoliter range. Here, an advanced Single-Cell Printer (SCP) was applied for automated and label-free isolation and deposition of bacterial cells encapsulated in 35 pl droplets by inkjet-like printing. To achieve this, dispenser chips to generate micro droplets have been fabricated with nozzles 20 μm in size. Further, the magnification of the optical system used for cell detection was increased. Redesign of the optical path allows for collision-free addressing of any flat substrate since no compartment protrudes below the nozzle of the dispenser chip anymore. The improved system allows for deterministic isolation of individual bacterial cells. A single-cell printing efficiency of 93% was obtained as shown by printing fluorescent labeled E. coli. A 96-well plate filled with growth medium is inoculated with single bacteria cells on average within about 8 min. Finally, individual bacterial cells from a heterogeneous sample of E. coli and E. faecalis were isolated for clonal culturing directly on agar plates in user-defined array geometry.
• J. Riba, N. Renz, C. Niemöller, S. Bleul, D. Pfeifer, J. M. Stosch, K. H. Metzeler, B. Hackanson, M. Lübbert, J. Duyster, P. Koltay, R. Zengerle, R. Claus, S. Zimmermann, H. Becker
  Molecular Genetic Characterization of Individual Cancer Cells Isolated via Single-Cell Printing
  2016 Plos One, volume: 6, page: 32837
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  Abstract

  Intratumoral genetic heterogeneity may impact disease outcome. Gold standard for dissecting clonal heterogeneity are single-cell analyses. Here, we present an efficient workflow based on an advanced Single-Cell Printer (SCP) device for the study of gene variants in single cancer cells. To allow for precise cell deposition into microwells the SCP was equipped with an automatic dispenser offset compensation, and the 384-microwell plates were electrostatically neutralized. The ejection efficiency was 99.7% for fluorescent beads (n = 2304) and 98.7% for human cells (U-2 OS or Kasumi-1 cancer cell line, acute myeloid leukemia [AML] patient; n = 150). Per fluorescence microscopy, 98.8% of beads were correctly delivered into the wells. A subset of single cells (n = 81) was subjected to whole genome amplification (WGA), which was successful in all cells. On empty droplets, a PCR on LINE1 retrotransposons yielded no product after WGA, verifying the absence of free-floating DNA in SCP-generated droplets. Representative gene variants identified in bulk specimens were sequenced in single-cell WGA DNA. In U-2 OS, 22 of 25 cells yielded results for both an SLC34A2 and TET2 mutation site, including cells harboring the SLC34A2 but not the TET2 mutation. In one cell, the TET2 mutation analysis was inconclusive due to allelic dropout, as assessed via polymorphisms located close to the mutation. Of Kasumi-1, 23 of 33 cells with data on both the KIT and TP53 mutation site harbored both mutations. In the AML patient, 21 of 23 cells were informative for a TP53 polymorphism; the identified alleles matched the loss of chromosome arm 17p. The advanced SCP allows efficient, precise and gentle isolation of individual cells for subsequent WGA and routine PCR/sequencing-based analyses of gene variants. This makes single-cell information readily accessible to a wide range of applications and can provide insights into clonal heterogeneity that were indeterminable solely by analyses of bulk specimens.
• L. Gutzweiler, F. Stumpf, L. Tanguy, G. Roth, P. Koltay, R. Zengerle, L. Riegger
  Semi-contact-writing of polymer molds for prototyping PDMS chips with low surface roughness, sharp edges and locally varying channel heights
  2016 J Micromech Microeng, volume: 26, issue: 4, pages: 45018 - 45027
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  Abstract

  Microfluidic systems fabricated in polydimethylsiloxane (PDMS) enable a broad variety of applications and are widespread in the field of Lab-on-a-Chip. Here we demonstrate semi-contact-writing, a novel method for fabrication of polymer based molds for casting microfluidic PDMS chips in a highly flexible, time and cost-efficient manner. The method is related to direct-writing of an aqueous polymer solution on a planar glass substrate and substitutes conventional, time- and cost-consuming UV-lithography. This technique facilitates on-demand prototyping in a low-cost manner and is therefore ideally suited for rapid chip layout iterations. No cleanroom facilities and less expertise are required. Fabrication time from scratch to ready-to-use PDMS-chip is less than 5 h. This polymer writing method enables structure widths down to 140 μm and controllable structure heights ranging from 5.5 μm for writing single layers up to 98 μm by stacking. As a unique property, freely selectable height variations across a substrate can be achieved by application of local stacking. Furthermore, the molds exhibit low surface roughness (R a   =  24 nm, R RMS  =  28 nm) and high fidelity edge sharpness. We validated the method by fabrication of molds to cast PDMS chips for droplet based flow-through PCR with single-cell sensitivity.
• S. Kartmann, F. Koch, P. Koltay, R. Zengerle, A. Ernst
  Single-use capacitive pressure sensor employing radial expansion of a silicone tube
  2016 Sensor Actuat A-phys, volume: 247
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  Abstract

  This paper reports on a single-use pressure sensor for medical applications. The sensor principle makes use of the radial expansion of a silicone tube which occurs when there is a pressure difference between the inside and the outside of the tube. The change in outer diameter is detected by a capacitive measurement method, whereas the amplification electronics can be separated from the tube being in contact with the fluid. This enables a cross-contamination-free measurement system for patient near application as e.g. within infusion systems. The sensor includes a novel highly sensitive and fast analog amplification circuit in combination with gold electrodes fabricated in PCB technology. This circuit enables to amplify even highly dynamic pressure changes, in the range of a few milliseconds causing capacitive changes on the electrodes in the fF range to a readable voltage level. A functional model is developed based on flex board technology which allows for studying the influence of the electrode geometry as well as the material properties of the silicone tube with respect to the sensitivity of the sensor. The best performing electrode geometry determined by experiments features a sensitivity of 0.195 fF/kPa at a mean coefficient of variation (CV) of 6.4%, considering three individual sensor assemblies. A sensor prototype is designed and fabricated based on the results of the investigated functional model. The performance of the prototype is investigated experimentally in a pressure range from 0 to 40 kPa. As a result a sensitivity of 0.135 V/kPa for DI water as measurement liquid could be achieved and a good linearity of the signal (R² = 0.996) was observed up to 35 kPa.

2015

• S. Kartmann, P. Koltay, R. Zengerle, A. Ernst
  A Disposable Dispensing Valve for Non-Contact Microliter Applications in a 96-Well Plate Format
  2015 Micromachines, volume: 6, pages: 423 - 436
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  Abstract

  We present a miniaturized, disposable, normally-closed electromagnetic dispensing valve for the microliter range to process 96-well plates. The novel injection-molded valve is designed to fit into a 9 mm grid to realize an eight channel dispensing head, enabling the serial processing of well plates row-by-row. The presented dispensing valve design originates from a miniaturization study of a previously developed functional model. The outer diameter of the valve, including all actuating components, was reduced by 8 mm to an overall diameter of 8.5 mm without compromising the performance. Additionally, the actuation current of the valve could be reduced to 5 A. The valve is characterized for a volume range between 840 nL and 5.3 μL. The performance of the injection molded valve is competitive to commercially available dispensing valves, featuring the advantages of low fabrication costs, disposability, low mounting size, easy handling, and super silent actuation.
• I. Leibacher, J. Schoendube, J. Dual, R. Zengerle, P. Koltay
  Enhanced single-cell printing by acoustophoretic cell focusing
  2015 Biomicrofluidics, volume: 9, page: 024109
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  Abstract

  Recent years have witnessed a strong trend towards analysis of single-cells. To access and handle single-cells, many new tools are needed and have partly been developed. Here, we present an improved version of a single-cell printer which is able to deliver individual single cells and beads encapsulated in free-flying picoliter droplets at a single-bead efficiency of 96% and with a throughput of more than 10 beads per minute. By integration of acoustophoretic focusing, the cells could be focused in x and y direction. This way, the cells were lined-up in front of a 40 µm nozzle, where they were analyzed individually by an optical system prior to printing. In agreement with acoustic simulations, the focusing of 10 µm beads and Raji cells has been achieved with an efficiency of 99% (beads) and 86% (Raji cells) to a 40 µm wide center region in the 1mm wide microfluidic channel. This enabled improved optical analysis and reduced bead losses. The loss of beads that ended up in the waste (because printing them as single beads arrangements could not be ensured) was reduced from 52 ± 6% to 28 ± 1%. The piezoelectric transducer employed for cell focusing could be positioned on an outer part of the device, which proves the acoustophoretic focusing to be versatile and adaptable.
• F. Stumpf, J. Schoendube, A. Gross, C. Rath, S. Niekrawietz, P. Koltay, G. Roth
  Single-cell PCR of genomic DNA enabled by automated single-cell printing for cell isolation
  2015 Biosens Bioelectron, volume: 69, pages: 301 - 306
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  Abstract

  Single-cell analysis has developed into a key topic in cell biology with future applications in personalized medicine, tumor identification as well as tumor discovery (Editorial, 2013). Here we employ inkjet-like printing to isolate individual living single human B cells (Raji cellline) and load them directly into standard PCR tubes. Single cells are optically detected in the nozzle of the microfluidic piezoelectric dispenser chip to ensure printing of droplets with single cells only. The printing process has been characterized by using microbeads (10 µm diameter) resulting in a single bead delivery in 27 ou tof 28 cases and relative positional precision of ± 350 µm at a printing distance of 6 mm between nozzle and tube lid. Process-integrated optical imaging enabled to identify the printing failure as void droplet and to exclude it from downstream processing. PCR of truly single-cell DNA was performed without pre-amplification directly from single Raji cells with 33% success rate (N=197) and Cq values of 36.3 ± 2.5. Additionally single cell whole genome amplification (WGA) was employed to pre-amplify the single-cell DNA by a factor of >1000. This facilitated subsequent PCR for the same gene yielding a success rate of 64% (N=33) which will allow more sophisticated downstream analysis like sequencing, electrophoresis or multiplexing.
• J. Schoendube, D. Wright, R. Zengerle, P. Koltay
  Single-cell printing based on impedance detection
  2015 Biomicrofluidics, volume: 9, page: 014117
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  Abstract

  Label-free isolation of single cells is essential for the growing field of single-cell analysis. Here, we present a device which prints single living cells encapsulated in free-flying picoliter droplets. It combines inkjet printing and impedance flow cytometry. Droplet volume can be controlled in the range of 500 pl–800 pl by piezo actuator displacement. Two sets of parallel facing electrodes in a 50 µm x 55 µm channel are applied to measure the presence and velocity of a single cell in real-time. Polystyrene beads with <5% variation in diameter generated signal variations of 12%–17% coefficients of variation. Single bead efficiency (i.e., printing events with single beads vs. total number of printing events) was 73%611% at a throughput of approximately 9 events/min. Viability of printed HeLa cells and human primary fibroblasts was demonstrated by culturing cells for at least eight days.
• J. Schoendube, A. Yusof, K. Kalkandjiev, R. Zengerle, P. Koltay
  Wafer level fabrication of single cell dispenser chips with integrated electrodes for particle detection
  2015 J Micromech Microeng, volume: 25, page: 025008
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  Abstract

  This work presents the microfabrication and experimental evaluation of a dispenser chip, designed for isolation and printing of single cells by combining impedance sensing and drop-on-demand dispensing. The dispenser chip features 50 × 55 μm (width × height) microchannels, a droplet generator and microelectrodes for impedance measurements. The chip is fabricated by sandwiching a dry film photopolymer (TMMF) between a silicon and a Pyrex wafer. TMMF has been used to define microfluidic channels, to serve as low temperature (75 °C) bonding adhesive and as etch mask during 300 μm deep HF etching of the Pyrex wafer. Due to the novel fabrication technology involving the dry film resist, it became possible to fabricate facing electrodes at the top and bottom of the channel and to apply electrical impedance sensing for particle detection with improved performance. The presented microchip is capable of dispensing liquid and detecting microparticles via impedance measurement. Single polystyrene particles of 10 μm size could be detected with a mean signal amplitude of 0.39 ± 0.13 V (n = 439) at particle velocities of up to 9.6 mm s−1 inside the chip.

2014

• D. Liang, J. Zhang, M.T. Govindaiah, L. Tanguy, A. Ernst, R. Zengerle, P. Koltay
  Liquid volume measurement method for the picoliter to nanoliter volume range based on quartz crystal microbalance technology
  2014 Meas Sci Technol, volume: 25, page: 095302
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  Abstract

  In this article, a quantitative liquid volume measurement method for the sub-nanoliter range using a quartz crystal microbalance (QCM) is described and experimentally analyzed. The primary measurement device to determine the volume of small liquid droplets is a QCM sensor coated with a surface-attached hydrogel to improve the mechanical coupling of the liquid to the sensor surface. An experimental evaluation of measured volumes in the range of 3 nl to 15 nl in normal room conditions has been performed with three identical sensors prepared with a PDMAA-1%MaBP hydrogel coating with a thickness of 1.5 µm ± 0.12 µm. A linearity of R2 more than 0.87, an average coefficient of variation (CV) within one experimental run of 5.7%, a mean absolute relative bias of 5.5%, and a sensor-to-sensor variation of 6.3% have been experimentally determined. The feasibility of this method has also been experimentally proven for the picoliter volume range down to 200 pl, with an average CV of 5.3% and a mean absolute relative bias of 6.5%. Furthermore, a stability evaluation consisting of 10 experimental series with approximately 150 measurements over the course of one week has been performed. This evaluation showed that the experimental setup, although exhibiting highly consistent performance within one measurement run, is not yet reproducible enough for long-term and repeated use because of undefined swelling and crack formation in the hydrogel layer. The low reproducibility implies a relatively high expanded uncertainty, with k = 2 according to the JCGM 'Evaluation of Measurement Data—Guide to the Expression of Uncertainty in Measurement' (GUM) for the total measurement method of approximately 3.82 nl when measuring a 10 nl liquid droplet. Nevertheless, the QCM method as described here contributes to significant progress beyond the state-of-the-art that might allow new opportunities for precise measurement of sub-nanoliter liquid volumes.
• K. Mutschler, S. Dwivedi, S. Kartmann, S. Bammesberger, P. Koltay, R. Zengerle, L. Tanguy
  Multi physics network simulation of a solenoid dispensing valve
  2014 Mechatronics, volume: 24, pages: 209 - 221
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  Abstract

  significant effects in a complete technical system. In a solenoid dispensing valve the involved physical effects are electro-magnetic (coil and magnet interaction), fluid flow and fluid structure interaction. It is challenging and time consuming to establish a full model description of these different effects even by using the most up-to-date Computational Fluid Dynamics (CFDs) software tools. This article therefore presents an alternative approach using network simulation methods for modelling of a dispensing valve using the simulation software SABER (Synopsys). To create the model, the different parts of the valve and the relevant physical effects occurring therein are described by partial differential equations and implemented as lumped elements. The lumped elements are then linked together to form a complete model of the dispensing valve including electrical, mechanical and fluid dynamic properties. A comparison with experimental data obtained from a real valve is presented at the end of the paper to discuss and validate the model. In particular the correct prediction of the dispensed liquid volume in dependence of the main parameters like pressure and opening time are considered. Using ab initio simulation deviations of the predicted dispensed liquid volume from the experimental results in the range 0.65–7.4% was found for different actuating pressures at valve opening times larger than 20 ms.

2013

• S. Bammesberger, S. Kartmann, L. Tanguy, D. Liang, K. Mutschler, A. Ernst, R. Zengerle, P. Koltay
  A Low-Cost, Normally Closed, Solenoid Valve for Non-Contact Dispensing in the Sub-μL Range
  2013 Micromachines, volume: 4, pages: 9 - 21
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  Abstract

  We present a disposable, normally closed, non-contact dispensing valve for the sub-μL range. The miniaturized solenoid valve (diameter: 8 mm, height: 27.25 mm) is compatible to standard Luer-Lock interfaces. A highly dynamic actuation principle enables opening times down to 1 ms. The dispensing performance was evaluated for water (η = 1.03 mPas) and a 66% (w/w) glycerol/water solution (η = 16.98 mPas), at pressures varying from 200 to 800 mbar. The experimentally determined minimal dispensing volume was 163 nL (CV 1.6%) for water and 123 nL (CV 4.5%) for 66% (w/w) glycerol/water. The low-cost polymer valve enables high precision dispensing of liquid volumes down to the lower end of the sub-μL range comparable to high-end non-disposable micro-dispensing valves.
• S. Bammesberger, I. Malki, A. Ernst, R. Zengerle, P. Koltay
  A calibration-free, noncontact, disposable liquid dispensing cartridge featuring an online process control
  2013 Journal of Laboratory Automation, volume: 27, pages: 394 - 402
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  Abstract

  We present a noncontact liquid dispenser that uses a disposable cartridge for the calibration-free dosage of diverse biochemical reagents from the nanoliter to the microliter range. The dispensing system combines the advantages of a positive displacement syringe pump (responsible for defining the aliquot’s volume with high accuracy) with a highly dynamic noncontact dispenser (providing kinetic energy to detach the liquid from the tip). The disposable, noncontact dispensing cartridge system renders elaborate washing procedures of tips obsolete. A noncontact sensor monitors the dispensing process to enable an online process control. To further increase confidence and reliability for particularly critical biomedical applications, an optional closed-loop control prevents malfunctions. The dispensing performance was characterized experimentally in the range of 0.25 to 10.0 µL using liquids of different rheological properties (viscosity 1.03–16.98 mPas, surface tension 30.49–70.83 mN/m) without adjusting or calibrating the actuation parameters. The precision ranged between a coefficient of variation of 0.5% and 5.3%, and the accuracy was below ±10%. The presented technology has the potential to contribute significantly to the improvement of biochemical liquid handling for laboratory automation in terms of usability, miniaturization, cost reduction, and safety.
• N. Lass, L. Riegger, R. Zengerle, P. Koltay
  Enhanced Liquid Metal Micro Droplet Generation by Pneumatic Actuation Based on the StarJet Method
  2013 Micromachines, volume: 4, pages: 49 - 66
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  Abstract

  We present a novel pneumatic actuation system for generation of liquid metal droplets according to the so-called StarJet method. In contrast to our previous work, the performance of the device has been significantly improved: the maximum droplet generation frequency in continuous mode has been increased to fmax = 11 kHz (formerly fmax = 4 kHz). In addition, the droplet diameter has been reduced to 60 μm. Therefore, a new fabrication process for the silicon nozzle chips has been developed enabling the production of smaller nozzle chips with higher surface quality. The size of the metal reservoir has been increased to hold up to 22 mL liquid metal and the performance and durability of the actuator has been improved by using stainless steel and a second pneumatic connection to control the sheath flow. Experimental results are presented regarding the characterization of the droplet generation, as well as printed metal structures.
• D. Liang, C. Steinert, S. Bammesberger, L. Tanguy, A. Ernst, R. Zengerle, P. Koltay
  Novel gravimetric measurement technique for quantitative volume calibration in the sub-microliter range
  2013 Meas Sci Technol, volume: 24, pages: 025301 - 025311
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  Abstract

  We present a novel measurement method based on the gravimetric principles adapted from the ASTM E542 and ISO 4787 standards for quantitative volume determination in the sub-microliter range. Such a method is particularly important for the calibration of non-contact micro dispensers as well as other microfluidic devices. The novel method is based on the linear regression analysis of continuously monitored gravimetric results and therefore is referred to as ‘gravimetric regression method (GRM)’. In this context, the regression analysis is necessary to compensate the mass loss due to evaporation that is significant for very small dispensing volumes. A full assessment of the measurement uncertainty of GRM is presented and results in a standard measurement uncertainty around 6 nl for dosage volumes in the range from 40 nl to 1 μl. The GRM has been experimentally benchmarked with a dual-dye ratiometric photometric method (Artel Inc., Westbrook, ME, USA), which can provide traceability of measurement to the International System of Units (SI) through reference standards maintained by NIST. Good precision (max. CV = 2.8%) and consistency (bias around 7 nl in the volume range from 40 to 400 nl) have been observed comparing the two methods. Based on the ASTM and ISO standards on the one hand and the benchmark with the photometric method on the other hand, two different approaches for establishing traceability for the GRM are discussed.
• S. Bammesberger, A. Ernst, N. Losleben, L. Tanguy, R. Zengerle, P. Koltay
  Quantitative characterization of non-contact microdispensing technologies for the sub-microliter range
  2013 Drug Discov Today, volume: 18, issue: 9-10, pages: 435 - 446
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  Abstract

  This work describes how to effectively compare non-contact dispensing technologies for automated liquid handling under high-throughput screening (HTS) conditions in the range of 0.05–10 ml. Exemplarily, we characterize five established technologies and categorize them into valve-based and positive displacement-based technologies. Furthermore we introduce dispensing accuracy and precision in an ‘intrarun’, ‘inter-run’ and ‘tip-to-tip’ context as universally applicable performance parameters. A NIST traceable spectrophotometric measurement method is utilized for experimental characterization. It yields an Intra-Run CV (Inter-Run CV) between 0.4% to 7.7% (0.5 to 10.9%) and a Tip-to-Tip CV between 1.4% and 9.9% for target volumes <1 ml. An absolute accuracy of better than 5.0% is generally difficult to achieve in the sub-microliter range.
• A. Gross, J. Schöndube, S. Niekrawitz, W. Streule, L. Riegger, R. Zengerle, P. Koltay
  Single-Cell Printer: Automated,On Demand, and Label Free
  2013 JALA - J Lab Autom, volume: 18, issue: 6, pages: 504 - 518
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  Abstract

  Within the past years, single-cell analysis has developed into a key topic in cell biology to study cellular functions that are not accessible by investigation of larger cell populations. Engineering approaches aiming to access single cells to extract information about their physiology, phenotype, and genotype at the single-cell level are going manifold ways, meanwhile allowing separation, sorting, culturing, and analysis of individual cells. Based on our earlier research toward inkjet-like printing of single cells, this article presents further characterization results obtained with a fully automated prototype instrument for printing of single living cells in a noncontact inkjet-like manner. The presented technology is based on a transparent microfluidic drop-on-demand dispenser chip coupled with a camera-assisted automatic detection system. Cells inside the chip are detected and classified with this detection system before they are expelled from the nozzle confined in microdroplets, thus enabling a “one cell per droplet” printing mode. To demonstrate the prototype instrument’s suitability for biological and biomedical applications, basic experiments such as printing of single-bead and cell arrays as well as deposition and culture of single cells in microwell plates are presented. Printing efficiencies greater than 80% and viability rates about 90% were achieved.

2012

• A. Tropmann, L. Tanguy, P. Koltay, R. Zengerle, L. Riegger
  Completely superhydrophobic PDMS surfaces for microfluidics
  2012 Langmuir, volume: 28, issue: 22, pages: 8292 - 8295
• A. Ernst, K. Mutschler, L. Tanguy, N. Paust, R. Zengerle, P. Koltay
  Numerical Investigations on Electric Field Characteristics with Respect to Capacitive Detection of Free-Flying Droplets
  2012 sensors, volume: 12, pages: 10550 - 10565
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  Abstract

  In this paper a multi-disciplinary simulation of a capacitive droplet sensor based on an open plate capacitor as transducing element is presented. The numerical simulations are based on the finite volume method (FVM), including calculations of an electric field which changes according to the presence of a liquid droplet. The volume of fluid (VOF) method is applied for the simulation of the ejection process of a liquid droplet out of a dispenser nozzle. The simulations were realised using the computational fluid dynamic (CFD) software CFD ACE+. The investigated capacitive sensing principle enables to determine the volume of a micro droplet passing the sensor capacitor due to the induced change in capacity. It could be found that single droplets in the considered volume range of 5 nL < Vdrop < 100 nL lead to a linear change of the capacity up to ΔQ < 30 fC. The sensitivity of the focused capacitor geometry was evaluated to be Si = 0.3 fC/nL. The simulation results are validated by experiments which exhibit good agreement.
• A. Tropmann, N. Lass, N. Paust, T. Metz, C. Ziegler, R. Zengerle, P. Koltay
  Pneumatic Dispensing of Nano- to Picoliter Droplets of Liquid Metal with the StarJet Method for Rapid Prototyping of Metal Microstructures
  2012 Microfluid Nanofluid, volume: 12, pages: 75 - 84
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  Abstract

  This work presents a new, simple and robust, pneumatically actuated method for the generation of liquid metal micro droplets in the nano- to picoliter range. The so called StarJet dispenser utilizes a star-shaped nozzle geometry that stabilizes liquid plugs in its center by means of capillary forces. Single droplets of liquid metal can be pneumatically generated by interaction of the sheathing gas flow in the outer grooves of the nozzle and the liquid metal. For experimental validation, a print head was build consisting of silicon chips with a star-shaped nozzle geometry and a heated actuator (up to 280 °C). The silicon chips are fabricated by Deep Reactive Ion Etching (DRIE). Chip designs with different star-shaped geometries were able to generate droplets with diameters in the range of the corresponding nozzle diameters. The StarJet can be operated in two modes: Either continuous droplet dispensing mode or drop on demand (DoD) mode. The continuous droplet generation mode for a nozzle with 188 µm diameter shows tear-off frequencies between 25 Hz and 120 Hz, while droplet diameters remain constant at 210 µm for each pressure level. Metal columns were printed with a thickness of 0.5 to 1.0 mm and 30 mm height (aspect ratio >30) to demonstrate the directional stability of droplet ejection and its potential as a suitable tool for direct prototyping of metal microstructures.
• A. Gulliksen, H. Keegan, C. Martin, J. O’Leary, L. A. Solli, I. M. Falang, P. Grønn, A. Karlg°ard, M. M. Mielnik, Ib-R.Johansen, Terje R. Tofteberg, T. Baier, R. Gransee, K. Drese, T. Hansen-Hagge, L. Riegger, P. Koltay, R. Zengerle, F. Karlsen, D. Ausen, , , Liv Furuberg2, 4
  Towards a “Sample-In, Answer-Out” Point-of-Care Platform for Nucleic Acid Extraction and Amplification: Using an HPV E6/E7mRNAModel System
  2012 Journal of Oncology, volume: 2012, page: ID 905024
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  Abstract

  The paper presents the development of a “proof-of-principle” hands-free and self-contained diagnostic platform for detection of human papillomavirus (HPV) E6/E7 mRNA in clinical specimens. The automated platform performs chip-based sample preconcentration, nucleic acid extraction, amplification, and real-time fluorescent detection with minimal user interfacing. It consists of two modular prototypes, one for sample preparation and one for amplification and detection; however, a common interface is available to facilitate later integration into one single module. Nucleic acid extracts (n = 28) from cervical cytology specimens extracted on the sample preparation chip were tested using the PreTect HPV-Proofer and achieved an overall detection rate for HPV across all dilutions of 50%–85.7%. A subset of 6 clinical samples extracted on the sample preparation chip module was chosen for complete validation on the NASBA chip module. For 4 of the samples, a 100% amplification for HPV 16 or 33 was obtained at the 1 : 10 dilution for microfluidic channels that filled correctly. The modules of a “sample-in, answer-out” diagnostic platform have been demonstrated from clinical sample input through sample preparation, amplification and final detection.

2011

• Azmi Yusof, Helen Keegan, Cathy D. Spillane, Orla M. Sheils, Cara M. Martin, John J. O’Leary, Roland Zengerle, Peter Koltay
  Inkjet-like printing of single-cells
  2011 Lab Chip, volume: 11, pages: 2447 - 2454
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  Abstract

  Cell sorting and separation techniques are essential tools for cell biology research and for many diagnostic and therapeutic applications. For many of these applications, it is imperative that heterogeneous populations of cells are segregated according to their cell type and that individual cells can be isolated and analysed. We present a novel technique to isolate single cells encapsulated in a picolitre sized droplet that are then deposited by inkjet-like printing at defined locations for downstream genomic analysis. The single-cell-manipulator (SCM) developed for this purpose consists of a dispenser chip to print cells contained in a free flying droplet, a computer vision system to detect single-cells inside the dispenser chip prior to printing, and appropriate automation equipment to print single-cells onto defined locations on a substrate. This technique is spatially dynamic, enabling cell printing on a wide range of commonly used substrates such as microscope slides, membranes and microtiter plates. Demonstration experiments performed using the SCM resulted in a printing efficiency of 87% for polystyrene microbeads of 10 mm size. When the SCM was applied to a cervical cancer cell line (HeLa), a printing efficiency of 87% was observed and a post-SCM cell viability rate of 75% was achieved.
• M. Pospischil, K. Zengerle, J. Specht, G. Birkle, P. Koltay, R. Zengerle, A. Henning, M. Neidert, C. Mohr, F. Clement, D. Biro
  Investigations on Thick-Film-Paste Rheology for Dispensing Applications
  2011 Energy Procedia, volume: 8, pages: 449 - 454
  » show abstract« hide abstract
  Abstract

  In order to establish dispensing as a promising metallization process in silicon photovoltaics, equipment and metal pastes require further optimization. By conducting several rheological experiments based on rotational tests, shear thinning as well as thixotropic behavior of thick-film pastes were investigated. Both are crucial parameters for continuous dispensing of 60 μm fingers with high aspect ratios. Flow rate fluctuations during dispensing though imply stress peaks that may disturb a continuous paste flow. Thus, a comparison of the flow rate of two pastes was conducted. A comparison of dispensed cells with screen-printed reference cells, on multi-crystalline wafer-material, showed an efficiency increase of 0.3%abs. on average. This is mainly caused by reduced finger widths and higher aspect ratios of dispensed fingers.
• K Kalkandjiev, L Riegger, D Kosse, M Welsche, L Gutzweiler, R Zengerle, P Koltay
  Microfluidics in silicon/polymer technology as a cost-efficient alternative to silicon/glas
  2011 J Micromech Microeng, volume: 21, page: 025008 (8p
  » show abstract« hide abstract
  Abstract

  We investigate TMMF photopolymer as a cost efficient alternative to glass for the liquid tight sealing of high density silicon microchannels. TMMF enables low temperature sealing and access to structures underneath via lamination and standard UV lithography instead of costly glass machining and anodic bonding. TMMF is highly transparent and has a low autofluorescence for wavelengths larger than 400 nm. As the photopolymer is too thin for implementing bulky World-to-Chip-interfaces, we propose adhesive bonding of COC modules. All materials were tested according ISO 10993-5 and showed no cytotoxic effects on the proliferation of L929 cells. To quantify the cost efficiency of the proposed techniques, we used an established Si/Pyrex nanoliter dispenser as a reference and replaced structured Pyrex wafers by TMMF laminates and COC modules. Thus, consumable costs and time effort were reduced by 90 % respectively 35 % for the sealing and 80 % respectively 75 % for implementing the World-to-Chip interface. Liquid tightness was proved by applying a pressure of 0,2 MPa for 5 h without delamination or cross talk between neighbouring microchannels separated from each other by 100 µm. In contrast to anodic bonding, the proposed techniques are tolerant to surface inhomogenities. They enable manufacturing of silicon/polymer microfluidics at significantly lower costs and without compromising the performance compared to corresponding silicon/glass devices.
• Ernst, Andreas, Ju, Lin, Vondenbusch, Bernhard, Zengerle, Roland, Koltay, Peter
  Noncontact Determination of Velocity and Volume of Nanoliter Droplets on the Fly
  2011 Ieee Sens J, volume: 11, issue: 8, pages: 1736 - 1742
  » show abstract« hide abstract
  Abstract

  We present a sensor for measuring volume and velocity of dispensed nanoliter droplets in a noncontact manner on the fly. The sensor-setup has a total thickness of 3.2 mm and can easily be mounted underneath any given nanoliter dispenser for continuous online monitoring of its dispensing performance. The principle is based on the interaction of dispensed single droplets of sample liquid passing the electric field of an open plate capacitor. The effect depends on droplet parameters like volume, velocity, and dielectric constant and is discussed in the paper. The presented data analysis enables a velocity independent volume determination of water droplets in the range from 26 to 82 nl with an accuracy of 3 nl. The sensor signal is sensitive to the alignment of the flight path of the nanoliter droplets within the 1.2-mm wide open capacitor and can lead to systematic volume errors of up to Delta V approx. 12 nl. The impact of different dielectric constants can only be differentiated for very high variations; thus, the sensor needs to be calibrated to the different types of liquids.

2010

• Lutz Riegger, Oliver Strohmeier, Bernd Faltin, Roland Zengerle, Peter Koltay
  Adhesive bonding of microfluidic chips: influence of process parameters
  2010 J Micromech Microeng, volume: 20, pages: 087003 - (5pp)
  » show abstract« hide abstract
  Abstract

  In this note, the influence of process parameters for adhesive bonding as a versatile approach for the sealing of polymer microfluidic chips is investigated. Specifically, a process chain comprising pre-processing, adhesive transfer as well as post-processing is presented and parameter recommendations are provided. As a device for adhesive transfer, a modified laminator is utilized which transfers thin layers of adhesive onto the chip surface, only via a silicone roll. Using this device and a high temperature (Tg > 100 ◦C) epoxy adhesive, adhesive layers in the range of 2–4 μm can be reproducibly transferred (CV < 4%). For best bonding results, it is recommended to provide 2.5 μm thin layers of adhesive in combination with a subsequent evacuation step at 10 mbar for 3 h. Further, it is proposed to integrate capture channels near large, featureless areas to compensate for variations in processing and thus prevent clogging of channels.
• Tobias Metz, Nils Paust, Roland Zengerle, Peter Koltay
  Capillary driven movement of gas bubbles in tapered structures
  2010 Microfluid Nanofluid, volume: 9, pages: 341 - 355
  » show abstract« hide abstract
  Abstract

  This article presents a study on the capillary driven movement of gas bubbles confined in tapered channel configurations. These configurations can be used to transport growing gas bubbles in micro fluidic systems in a passive way, i.e. without external actuation. A typical application is the passive degassing of CO2 in micro direct methanol fuel cells (lDMFC). Here, a one-dimensional model for the bubble movement in wide tapered channels is derived and calibrated by experimental observations. The movement of gas bubbles is modelled on straight trajectories based on a balance of forces. The bubble geometry is considered as three dimensional. In the development of the model, the effects of surface tension, inertia, viscosity, dynamic contact angle and thin film deposition are considered. It is found that in addition to viscous dissipation, the dynamics related to the contact line—dynamic contact angle and thin film deposition—are essential to describe the gas bubble’s movement. Nevertheless, it was also found that both of these effects, as modelled within this work, have similar impact and are hard to distinguish. The model was calibrated against experiments in a parameter range relevant for the application of travelling gas bubbles in passive degassing structures for lDMFCs.
• L. Riegger, M.M. Mielnik, A. Gulliksen, D. Mark, J. Steigert, S. Lutz, M. Clad, R. Zengerle, P. Koltay, J. Hoffmann
  Dye-based coatings for hydrophobic valves and their application to polymer labs-on-a-chip
  2010 J Micromech Microeng, volume: 20, page: 045021
  » show abstract« hide abstract
  Abstract

  We provide a method for the selective surface patterning of microfluidic chips with hydrophobic fluoropolymers which is demonstrated by the fabrication of hydrophobic valves via dispensing. It enables efficient optical quality control for the surface patterning thus permitting the low-cost production of highly reproducible hydrophobic valves. Specifically, different dyes for fluoropolymers enabling visual quality control (QC) are investigated, and two fluoropolymer-solvent-dye solutions based on fluorescent quantum dots (QD) and carbon black (CB) are presented in detail. The latter creates superhydrophobic surfaces on arbitrary substrates, e.g. chips made from cyclic olefin copolymer (COC, water contact angle = 157.9◦), provides good visibility for the visual QC in polymer labs-on-a-chip and increases the burst pressures of the hydrophobic valves. Finally, an application is presented which aims at the on-chip amplification of mRNA based on defined flow control by hydrophobic valves is presented. Here, the optimization based on QC in combination with the Teflon-CB coating improves the burst pressure reproducibility from 14.5% down to 6.1% compared to Teflon-coated valves.
• J. Tröndle, A. Ernst, W. Streule, R. Zengerle, P. Koltay
  Non-contact optical sensor to detect free flying droplets in the nanolitre range
  2010 Sensor Actuat A-phys, volume: 158, pages: 254 - 262
  » show abstract« hide abstract
  Abstract

  This paper reports on a non-contact optical sensor for the detection of single droplets in flight. The sensor allows for online process control of non-contact dispensing systems delivering droplets in the nanolitre range. A dispensed liquid droplet, which passes through the optical transducer, leads to a change of the light intensity caused by absorption, reflection and diffraction. The change in light intensity measured by a photo transistor provides information about, e.g. droplet size, velocity and shape. This information is encoded in the time dependent signal shape that yields a characteristic “fingerprint”- signal for each droplet. The fabrication of the sensor is achieved by standard printing circuit board (PCB) technology. Therefore, an easy adaption of the sensor to different kinds of contactless dispensing system and furthermore a very cost efficient production is granted.

2009

• A. Ernst, W. Streule, N. Schmitt, R. Zengerle, P. Koltay
  A capacitive sensor for non-contact nanoliter droplet detection
  2009 Sensor Actuat A-phys, volume: 153, pages: 57 - 63
  » show abstract« hide abstract
  Abstract

  This paper reports on a sensor for the detection of microdroplets in flight. The presented sensor is based on a capacitive principle, which allows for non-contact monitoring of a complete droplet dispensing process. In the presented experiments the change in capacity caused by liquid droplets in the range of a few nanoliters passing through the electric field of the sensor is studied. From the capacitive change the droplet presence can be deduced with a reliability of 100%, which means that every single droplet dispensed within the experiments caused a significant signal change. In addition, the sensor signal is sensitive to the droplet’s volume V, dielectric constant εr (epsilon) and velocity v. It turns out that every specific droplet exhibits a characteristic “fingerprint” signal dependingonthese parameters. Especially the droplet volume correlates very well with the peak value of the extracted signal. Therefore, the calibrated sensor is able to determine the volume of dispensed droplets in the range from20 to 65 nl with a resolution of less than 2 nl. Furthermore, the printed circuit board (PCB) technology applied for fabrication of the sensor enables a very cost efficient and flexible realisation of the whole sensor unit. The non-contact capacitive principle prevents contamination and loss of media. Therefore, the proposed approach is well suited for high precision droplet presence detection and low cost online monitoring of liquid volumes in microdispensing processes for various applications.
• Steigert, Jürgen, Strasser, Monika, Wangler, Nicolai, Brett, Olivia, Streule, Wolfgang, Koltay, Peter, Daub, Martina, Zengerle, Roland
  A modular diffusion barrier based on phase separation for localized delivery of discrete drug volumes in aqueous environments
  2009 Lab Chip, volume: 9, pages: 1801 - 1805
  » show abstract« hide abstract
  Abstract

  We present a new tool for the precisely controlled transfer of individual picoliter (pL) droplets in the range of 150–950 pL at user defined local positions within aqueous liquid environments while avoiding any leakage by diffusion. This is achieved by a low-cost, disposable and biocompatible cap that can be placed on top of any pL-dispenser and generates a phase-gap between dispensing agent and target liquid when the dispenser is dipped into the latter. We developed two different working modes: (i) the standard mode enables an instant injection (<< 1 ms) of the droplet into the liquid environment and (ii) the focus mode further increases the spatial resolution from 100 µm to 50 µm at the cost of slowing down the injection time. For the phase-gap we have proven an excellent long-term stability of more than 30 hours against capillary priming.
• N. Paust, Ch. Litterst, T. Metz, M. Eck, Ch. Ziegler, R. Zengerle, P. Koltay
  Capillary-driven pumping for passive degassing and fuel supply in direct methanol fuel cells
  2009 Microfluid Nanofluid, volume: 7, pages: 531 - 543
  » show abstract« hide abstract
  Abstract

  In this paper we present a new concept of creating and using capillary pressure gradients for passive degassing and passive methanol supply in direct methanol fuel cells (DMFCs). An anode flow field consisting of parallel tapered channels structures is applied to achieve the passive supply mechanism. The flow is propelled by the surface forces of deformed CO2 bubbles, generated as a reaction product during DMFC operation. This work focuses on studying the influence of channel geometry and surface properties on the capillary-induced liquid flow rates at various bubbly gas flow rates. Besides the aspect ratios and opening angles of the tapered channels, the static contact angle as well as the effect of contact angle hysteresis has been identified to significantly influence the liquid flow rates induced by capillary forces at the bubble menisci. Applying the novel concept, we show that the liquid flow rates are up to thirteen times higher than the methanol oxidation reaction on the anode requires. Experimental results are presented that demonstrate the continuous passive operation of a DMFC for more than 15 h.
• Paust, N, Krumbholz, S, Munt, S, Müller, C, Koltay, P, Zengerle, R, Ziegler, C
  Self-Regulating Passive Fuel Supply for Small Direct Methanol Fuel Cells Operating in All Orientations
  2009 J Power Sources, volume: 192, pages: 442 - 450
  » show abstract« hide abstract
  Abstract

  A microfluidic fuel supply concept for passive and portable Direct Methanol Fuel Cells (DMFCs) that operate in all spatial orientations is presented. The concept has been proven by fabricating and testing a passive DMFC prototype. Methanol transport at the anode is propelled by the surface energy of deformed carbon dioxide bubbles, generated as a reaction product during DMFC operation. The experimental study reveals that in any orientation, the proposed pumping mechanism transports at least 3.5 times more methanol to the reactive area of the DMFC than the stoichiometry of the methanol oxidation would require to sustain DMFC operation. Additionally, the flow rates closely follow the applied electric load; hence the pumping mechanism is self-regulating. Oxygen is supplied to the cathode by diffusion and the reaction product water is transported out of the fuel cell along a continuous capillary pressure gradient. Results are presented that demonstrate the continuous passive operation for more than 40 hours at ambient temperature with a power output of p = 4 mW cm-2 in the preferred vertical orientation and of p = 3.2 mW cm-2 in the least favourable horizontal orientation with the anode facing downwards. Keywords: passive DMFC; self-regulating fuel supply; capillary-force-driven bubble pump
• Steinert C.P., Kalkandjiev, K., Zengerle, R., Koltay, P.
  TopSpot® Vario: a novel microarrayer system for highly flexible and highly parallel picoliter dispensing
  2009 Biomed Microdevices, volume: 11, issue: 4, pages: 755 - 761
  » show abstract« hide abstract
  Abstract

  The standard TopSpot® technology has been successfully used in the recent years for the highly parallel nanoliter dispensing of bio-chemical substances for microarray printing. It is based on a pneumatically actuated printhead which enables non-contact microarray fabrication at a pitch of typically 500 μm. This paper reports on a new and improved way of operating the printheads termed TopSpot® Vario technology, using an incompressible material between the piezo actuator and the dispensing medium. The advantage of the incompressible medium is the direct relation between the displacement amplitude and the ejected liquid volume. Earlier reports stated that the filling of the printheads is a key issue. In this paper we report on the implementation and characterization of a new printhead design including microchannels for bubble free priming of blind channels. Microarray fabrication was successfully conducted with four different types of protein.

2008

• Glatzel T, Cupelli C, Lindemann T, Litterst C, Moosmann C, Niekrawietz R, Streule W, Zengerle R, Koltay P
  Computational fluid dynamics (CFD) software tools for microfluidic applications - A case study
  2008 Comput Fluids, volume: 37, issue: 3, pages: 218 - 235
• T. Metz, J. Viertel, C. Müller, S. Kerzenmacher, N. Paust, R. Zengerle, P. Koltay
  Passive water management for µfuel-cells using capillary microstructures
  2008 J Micromech Microeng, volume: 18, issue: 10
  » show abstract« hide abstract
  Abstract

  In this work we present a novel system for the passive water management in polymer electrolyte fuel cells (PEMFC) based on capillary effects in microstructures. The system removes abundant water that occurs at low temperatures at a fuel cell cathode and secures the humidity of the electrolyte membrane on higher temperatures. Liquid water is removed by hydrophilic gas supply channels with a tapered cross section as presented previously, and further transported by a system of capillary channels and a layer of nonwoven material. To prevent the membrane from running dry, a storage area in the nonwoven layer is introduced, controlled by a novel passive capillary overflow valve. The valve controls whether water is stored or finally disposed by gravity and evaporation. Experiments in a model system show that the nonwoven material is capable of removing all liquid water that can be produced by the fuel cell. A miniaturized fuel cell utilizing the novel water removal system was fabricated and experiments show that the system can stabilize the performance during changes of electrical load. Clearing the drowned miniaturized fuel cell flow field was proven and required 2 min. To make the capillary effects available for the originally hydrophobic graphite composite materials that were used to fabricate the flow fields, hydrophilic grafting based on photochemistry was applied to the material and contact angles of about 40° could be achieved and preserved for at least three months.
• Tobias Metz, Wolfgang Streule, Roland Zengerle, Peter Koltay
  StarTube: A tube with reduced contact line for minimized gas bubble resistance
  2008 Langmuir, volume: 24, issue: 17, pages: 9204 - 9206
  » show abstract« hide abstract
  Abstract

  In this work we introduce a novel tubing design for multiphase flow that minimizes gas bubble resistance. The design termed “StarTube” has a lamella-like wall structure and was developed to prevent clogging by gas bubbles. This is performed by forcing gas bubbles into the center of the tube by capillary forces, allowing liquid to bypass in the outer grooves. It was found that the mobility of gas bubbles in such a tube is increased more than 1 order of magnitude. The reason is that the contact line perpendicular to the direction of flow is minimized, reducing resistant effects related to the contact linesin particular, contact angle hysteresis.
• C. Litterst, T. Metz, R. Zengerle, P. Koltay
  Static and dynamic behaviour of gas bubbles in T-shaped non-clogging micro-channels
  2008 Microfluid Nanofluid, volume: 5, issue: 6, pages: 775 - 784
  » show abstract« hide abstract
  Abstract

  Preventing micro-channels from clogging is a major issue in most micro and nanofluidic systems. The T-shaped channel first reported by Kohnle et al. prevents micro-channels from clogging by the aid of the equilibrium bubble position in such a geometry. This work is concerned with the static and dynamic behaviour of bubbles in such T-shaped microchannels. The aspect ratio of a rectangle enclosing the Tshaped channel and the contact angle of the walls are the main parameters influencing the static and dynamic bubble behaviour. It is investigated in this article how these parameters relate to the equilibrium bubble shape and how optimum bubble velocities can be achieved inside the channel. An analytical model depending on the contact angle and the channel geometry is presented that allows to determine the bubble configuration inside the channel by minimizing the bubble’s surface energy. A second model is derived to predict the velocity of gas bubbles driven by buoyancy in vertical T-shaped channels. The model is applied to design T-shaped channels with a maximum mobility of gas bubbles. Experiments with MEMS fabricated devices and CFD simulations are used to verify the models. Furthermore design rules for an optimum nonclogging channel geometry which provides the highest gas bubble mobility are given. Keywords Gas bubble, Micro-channel, Clogging, Interfacial energy

2007

• Hu Min, Lindemann T, Goettsche T, Kohnle J, Zengerle R, Koltay P
  Discrete Chemical Release from a Microfluidic Chip
  2007 J Microelectromech S, volume: 16, issue: 4, pages: 786 - 794
  » show abstract« hide abstract
  Abstract

  We demonstrate a discrete chemical release method, capable of delivering picoliter volumes of chemical solutions with 100 μm of spatial resolution and 20 μs of response time. The releasing mechanism is based on the transfer of pulsed liquid plugs through a hydrophobic air chamber. A microfluidic chip consisting of such a releasing array (2 × 10) is designed and fabricated. Numerical simulation and experimental testing are performed to verify the working principle. Advantages of this release-on-demand technology include leakage-free, fast response and versatile control of release profile. This new method could be a key enabling technology for precisely controlled release of biochemicals for modern pharmacological and biological research. Index Terms: Air gap, discrete chemical stimulation, microfluidic chip, picoliter chemical release, pulsed liquid ejection.
• Zibek S, Stett A, Koltay P, Hu M, Zengerle R, Nisch W, Stelzle M
  Localized functional chemical stimulation of TE 671 cells cultured on nanoporous membrane by calcein and acetylcholine
  2007 Biophys J, volume: 92, issue: 1, pages: L04 - 6L
  » show abstract« hide abstract
  Abstract

  Acetylcholine sensitive TE 671 cells were cultured on nanoporous membranes and chemically stimulated by localized application of i), calcein-AM and ii), acetylcholine, respectively, onto the bottom face of the membrane employing an ink jet print head. Stimulus correlated response of cells was recorded by fluorescence microscopy with temporal and spatial resolution. Calcein fluorescence develops as a result of intracellular enzymatic conversion of calcein-AM, whereas Ca2+ imaging using fluo-4 dye was employed to visualize cellular response to acetylcholine stimulation. Using 25 pl droplets and substance concentration ranging from 10 µM to 1 mM on Nucleopore membranes with pore diameters between 50 nm and 1 µm, a resolution on the order of 50 µm was achieved.
• Lindemann,T., Ashauer,H., Duccio,Y.Y., Sassano,S., Zengerle,R., Koltay,P.
  One Inch Thermal Bubble Jet Printhead With Laser Structured Integrated Polyimide Nozzle Plate
  2007 Journal of Microelectromechanical Systems, volume: 16, issue: 2, pages: 420 - 428
• Metz,T., Paust,N., Müller,C., Zengerle,R., Koltay,P.
  Passive water removal in fuel cells by capillary droplet actuation
  2007 Sensors & Actuators: A.Physical, volume: Special Issue MEMS 2007
• Steigert J, Haeberle S, Brenner T, Mueller C, Steinert C P, Koltay P, Gottschlich N, Reinecke H, Ruehe J, Zengerle R, Ducrée J
  Rapid prototyping of microfluidic chips in COC
  2007 J Micromech Microeng, volume: 17, pages: 333 - 341

2006

• Steigert J, Grumann M, Dube M, Streule W, Riegger L, Brenner T, Koltay P, Mittmann K, Zengerle R, Ducrée J
  Direct Hemoglobin Measurement on a Centrifugal Microfluidic Platform for Point-of-Care Diagnostics
  2006 Sensors and Actuators, pages: 228 - 233
• Litterst C, Eccarius S, Hebling C, Zengerle R, Koltay P
  Increasing µDMFC efficiency by passive CO2 bubble removal and discontinuous operation
  2006 Journal of Micromechanics and Microengineering, volume: 16, issue: 9, pages: S248 - S253

2005

• Jeyaprakash JDS, Steger R, Birkle G, Zengerle R, Koltay P, Ruehe J
  Modification of Micronozzle Surfaces Using Fluorinated Polymeric Nanofilms for Enhanced Dispensing of Polar and Nonpolar Fluids
  2005 Analytical Chemistry, volume: 77, issue: 19, pages: 6469 - 6474
• Bohl B, Steger R, Zengerle R, Koltay P
  Multi-layer SU-8 Lift-Off Technology For Microfluidic Devices
  2005 Journal of Micromechanics and Microengineering, volume: 15, pages: 1125 - 1130

2004

• Streule W, Lindemann T, Birkle G, Zengerle R, Koltay P
  PipeJet: A Simple Disposable Dispenser for the Nano- and Microliter Range
  2004 Journal of the Association for Laboratory Automation (JALA), volume: 9, issue: 5, pages: 300 - 306
  » show abstract« hide abstract
  Abstract

  This paper reports on a simple, disposable non-contact dispenser for the nano- and microliter range. In contrast to other known dispensers manufactured by silicon micromachining the new device simply consists of an elastic polymer tube with a circular cross section. Actuation is done by a piezostack driven piston, squeezing the tube at a defined position near the open end by a significant fraction of the cross section. In contrast to drop-on-demand devices based on an acoustic actuation principle,5 the squeezing of the tube leads to a significant mechanical displacement of the liquid. Our experiments tested a large number of media in the viscosity range from 1 to 27 mPas. Some of our experiments tested up to approximately 2,000 mPas. Frequency characteristics showed an independent dosage volume for water up to a frequency of 15 Hz for tubes with an inner diameter of approximately 200 lm. Standard deviation within 1,000 shots resulted in an excellent CV (standard deviation/ dosage volume) of less than 2% of the dosage volume. Using tubes with an inner diameter of approximately 1,000 µm and a print frequency of 340 Hz, a flowrate of less than or equal to 143 µL/s could be reached. Beyond the possibility to dispense pure liquids, emulsion paints with particles that have a diameter of approximately 40 µm have also been printed successfully.
• Steger R, Bohl B, Zengerle R, Koltay P
  The dispensing well plate: a novel device for nanoliter liquid handling in ultra high-throughput screening
  2004 Journal of the Association for Laboratory Automation, volume: 9, issue: 5, pages: 291 - 299
  » show abstract« hide abstract
  Abstract

  This article reports on a novel dispensing system for the massive parallel delivery of liquid volumes in the range of 50 nL. Due to the similarity of the device to conventional micro-well plates used for the storage of liquids, the device has been termed ‘‘dispensing well plate’’ (DWP). In contrast to other known micro dispensers, the DWP can consist of up to 1,536 dispensing units in parallel, all of which hold different reagents. The dispensing units can be arranged very closely at the pitch of conventional micro-well plates (2.25 mm or 4.5 mm). Driven by pneumatic actuation, a fixed volume of different liquids can be dispensed simultaneously and contact-free into micro-well plates or onto flat substrates. Because of this, the liquid handling in many chemical, biochemical, and pharmaceutical applications—especially within highthroughput screening (HTS)—can be sped up by a factor of 10 to 100. In our article, the basic operation principle of the device is presented, and experimental evidence of its extraordinary performance is given: a reproducibility of 2% to 5% and a homogeneity within individual droplet arrays of 1% to 2% has been measured, as well as viscosity independent performance for liquids in the range from 1 to 5 mPas. The applicability of the DWP technology within HTS is demonstrated by performing a miniaturized kinase assay at 1 lL assay volume in a 1536- well plate format.
• Koltay P, Steger R, Bohl B, Zengerle R
  The dispensing well plate: a novel nanodispenser for the multiparallel delivery of liquids (DWP Part I)
  2004 Sensors and Actuators A-Physical, volume: 116, issue: 3, pages: 483 - 491
  » show abstract« hide abstract
  Abstract

  This paper reports on a novel dispensing system for the massive parallel delivery of liquid volumes in the range of 50 nL. Due to the similarity of the device to conventional microwell plates used for storage of liquids, the device has been termed “dispensing well plate” (DWP). In contrast to other known microdispensers the DWP can consist of up to 1536 dispensing units in parallel all holding different reagents. The dispensing units can be arranged very closely at the pitch of conventional microwell plates (2.25 or 4.5 mm). Driven by pneumatic actuation a fixed volume of different liquids can be dispensed simultaneously and contact free into microwell plates or onto flat substrates. By this the liquid-handling in many chemical, biochemical and pharmaceutical applications—especially within high throughput screening (HTS)—can be speed up by a factor 10–100. In this paper the basic operation principle of the device is presented and experimental evidence is given of its extraordinary performance: a reproducibility of 2–5% and a homogeneity within individual droplet arrays of 1–2% has been measured as well as viscosity independent performance for liquids in the range from 1 to 5mPas. The fabrication of DWP prototypes by different micromachining technologies based on silicon dry etching and SU-8 technology is described and various DWP prototypes with different dosage volumes are presented. © 2004 Elsevier B.V. All rights reserved. Keywords: Non-contact dispenser; Jets; High throughput screening; SU-8
• Koltay P, Kalix J, Zengerle R
  Theoretical evaluation of the dispensing well plate method (DWP part II)
  2004 Sensors and Actuators A-Physical, volume: 116, issue: 3, pages: 472 - 482
  » show abstract« hide abstract
  Abstract

  The “dispensing well plate” (DWPTM) method is a technique to deliver fluidic jets or droplets with volumes of several nanoliters contact free to targets likemicro well plates or slides. A cheap and simple pneumatic actuation mechanism allows for the simultaneous delivery of a large number of different liquids. In this paper the dispensing dynamics of a DWP-type nanodispenser is studied theoretically. The device is modelled using computational fluid dynamics (CFD) simulations which are benchmarked to experimental data. Furthermore an analytical discussion is presented providing some insight into the dispensing dynamics. Based on these modelling approaches the dispensing process is studied in detail. Influence of system parameters like driving pressure, nozzle size, channel layout etc. on the jet formation and dispensed volume are quantified and design rules are given to improve the performance. © 2004 Elsevier B.V. All rights reserved. Keywords: Droplet dispensing; Jets; CFD-simulation; Microfluidics

2001

• Peter Koltay, Bas de Heij, Hermann Sandmaier, Roland Zengerle
  Automatisiertes Liquid Handling im Nanoliterbereich
  2001 “Inno“ Innovative Technik – Anwendungen aus Nordrhein-Westfalen; Nr. 19 (3/01)

Reviews

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2015

• A. Gross, J. Schoendube, S. Zimmermann, M. Steeb, R. Zengerle, P. Koltay
  Technologies for Single-Cell Isolation
  2015 Int J Mol Sci, volume: 16, pages: 16897 - 16919
  » show abstract« hide abstract
  Abstract

  The handling of single cells is of great importance in applications such as cell line development or single-cell analysis, e.g., for cancer research or for emerging diagnostic methods. This review provides an overview of technologies that are currently used or in development to isolate single cells for subsequent single-cell analysis. Data from a dedicated online market survey conducted to identify the most relevant technologies, presented here for the first time, shows that FACS (fluorescence activated cell sorting) respectively Flow cytometry (33% usage), laser microdissection (17%), manual cell picking (17%), random seeding/dilution (15%), and microfluidics/lab-on-a-chip devices (12%) are currently the most frequently used technologies. These most prominent technologies are described in detail and key performance factors are discussed. The survey data indicates a further increasing interest in single-cell isolation tools for the coming years. Additionally, a worldwide patent search was performed to screen for emerging technologies that might become relevant in the future. In total 179 patents were found, out of which 25 were evaluated by screening the title and abstract to be relevant to the field.

Book chapters

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2018

• J. Riba, S. Zimmermann, P. Koltay
  Technologies for Automated Single Cell Isolation
  In: Handbook of Single Cell Technologies
  2018, Springer Nature, T. S. Santra, F.-G. Tseng, T. S. Santra, F.-G. Tseng, ISBN: 978-981-10-4857-9
  » show abstract« hide abstract
  Abstract

  The isolation of individual cells has gained tremendous importance with the advent of new methods for highly parallel single-cell analysis. A prerequisite for effective clonal cultivation or single-cell analysis is the efficient isolation of individual cells from liquid cell suspensions. This review provides an overview of technologies that are used to automate the isolation of single cells for subsequent cultivation or analysis. First, currently available technologies are classified based on their major technical characteristics. Then, the most prominent technologies such as limiting dilution, FACS, single-cell printing, hydrodynamic trapping, droplet microfluidics, and cell manipulation by external forces are described in detail. Furthermore, the individual features of each technology with focus on throughput, isolation efficiency, level of automation, flexibility in terms of cell types, and their suitability for specific downstream processing and analysis methods are discussed. In contrast to previous works, this review provides a classification approach for single-cell isolation technologies according to performance requirements, makes specific reference to methods for the isolation of microbial cells, and discusses sample input requirements, which is an important aspect in particular for diagnostic purposes.

2006

• Koltay P, Ducrée J, Zengerle R
  Microfluidic Platforms
  In: BioMEMS
  2006, Springer Verlag, Gerald A. Urban, pages: 139 - 165, Gerald A. Urban, ISBN: 10 0-387-28731-0
• Ducrée J, Koltay P, Zengerle R
  Microfluidics
  In: MEMS: A Practical Guide to Design, Analysis, and Applications
  2006, William Andrew Publishing, Jan G. Korvink, Oliver Paul, pages: 667 - 727, Jan G. Korvink, Oliver Paul, ISBN: 0-8155-1497-2

2003

• Koltay P, Ducrée J, Zengerle R
  Nanoliter and Picoliter Liquid Handling
  In: Lab-On-A-Chip: Miniaurized Systems for (Bio) Chemical Analysis and Synthesis
  2003, Elsevier Science, Edwin Oosterbroek, Albert van den Berg, pages: 151 - 171, Edwin Oosterbroek, Albert van den Berg, ISBN: 0-444-51100-8

Short communications

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2008

• Andreas Ernst, Peter Koltay
  Auch Mikrotropfen besitzen "Fingerabdrücke"
  2008 A&D Kompendium, pages: 191 - 194

Talks

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2014

• N. Lass, L. Riegger, R. Zengerle, P. Koltay
  Direktes Drucken von metallischer Mikrostrukturen mit der StarJet Technologie
  2014 Clusterkonferenz MicroTEC Südwest, Freiburg, 05.-06.05.2014
• S. Kartmann, A. Ernst, R. Zengerle, P. Koltay
  E-DosiS: Einweg-Dosiersystem mit intelligenter Sensorik
  2014 Clusterkonferenz MicroTEC Südwest, Freiburg, 05.-06.05.2014

2012

• A. Gross, J. Schoendube, W. Streule, L. Riegger, R. Zengerle, P. Koltay 1 3
  Non-contact, label-free printing of single, living cells
  2012 IMTEK Poster Session, Okt. 2012, Freiburg

2001

• Peter Koltay
  A novel Fixed Volume Dispenser for the Massive Parallel Liquid Handling of Nanoliter Volumes. (EuroLabAutomation; 23-25 October 2001; London).
  2001

Conference papers

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2024

• D. Straubinger, Z. Khan, P. Koltay, R. Zengerle, S. Kartmann, Z. Shu
  Investigation of metal jet printing for homogeneous lines with Starjet technology
  2024 MFHS 2024 - The 5th Conference on Microfluidic Handling Systems, Munich, 21-23 February 2024
• Z. Khan, A. Saphala, D. Straubinger, S. Kartmann, P. Koltay, R. Zengerle, O. Amft, Z. Shu
  Towards hybrid printing of intelligent devices: conductive traces from bulk metal for digital signals
  2024 MFHS 2024 - The 5th Conference on Microfluidic Handling Systems, Munich, 21-23 February 2024
• V. Zieger, D. Frejek, S. Zimmermann, P. Koltay, R. Zengerle, S. Kartmann
  Transfer volume modeling for feedback-free, automated single spheroid deposition using droplet-generated microfluidic flow
  2024 MFHS 2024 - The 5th Conference on Microfluidic Handling Systems, Munich, 21-23 February 2024

2023

• V. Zieger, D. Frejek, S. Zimmermann, P. Koltay, R. Zengerle, S. Kartmann
  A novel platform for automated and efficient handling of scaffold-free 3D cell-culture models enables well-controlled large-scale 3D in vitro drug screening
  2023 SLAS 2023 Conference and Exhibition, San Diego, CA, USA, 25.02. - 01.03.2023
• V. Zieger, E. Wöhr, S. Zimmermann, D. Frejek, P . Koltay, R. Zengerle, S. Kartmann
  Automated large scale spheroid generation via hanging drop and efficient transfer into physiological mimicking microenvironment
  2023 Transducers, Kyoto/Japan, May 25-29, 2023
• Z. Shu, S. Hennig, P. Koltay, S. Kartmann, F. von Stetten, R. Zengerle
  Automated sample preparation platform for protein diagnostics based on open microfluidics electrophoresis
  2023 Black Forest Nanopore Meeting, Freiburg, 06.-09.11.2023
• Z. Khan, P. Koltay, R. Zengerle, S. Kartmann, Z. Shu
  Direct conductive metal printing for one step fabrication of hybrid flexible electronics
  2023 inno LAE 2023, Cambridge, UK, 21. – 23. Feb. 2023
• Z. Khan, D. Gururajan, D. Straubinger, P. Koltay, S. Kartmann, R. Zengerle, Z. Shu
  Hybrid 3D-printing of molten metal microdroplets and polymers for prototyping of printed circuit boards with integrated electrical energy storage systems
  2023 Transducers, Kyoto/Japan, May 25-29, 2023
• V. Zieger, D. Frejek, S. Zimmermann, P. Koltay, R. Zengerle, S. Kartmann
  Selective high-throughput deposition of single spheroids towards automated 3D in vitro cell culture
  2023 3D Cell Culture 2023, Freiburg, 17. - 19.04.2023

2022

• Z. Khan, R. Zengerle, P. Koltay, S. Kartmann, Z. Shu
  3D printed single-layer functional PCB via digital hybrid printing of polymer and molten metal
  2022 5th International Conference on 3D Printing & Bioprinting, ΑΙ, Digital and Additive Manufacturing (I3D22)
• L. Riek, F. Koch, D. Frejek, L. Zausch, R. Zengerle, P. Koltay, S. Kartmann, S. Zimmermann
  A Bioprinting Fidelity Imager (BioFI) for a standardized characterization of bioprinting processes
  2022 SLAS Europe 2022 Conference and Exhibition, Dublin, Ireland, May 26, 2022
• Z. Khan, P. Koltay, R. Zengerle, S. Kartmann, Z. Shu
  Direct printing of molten solder via StarJet technology in Flexible Hybrid Electronics
  2022 Flex Conference & Expo, San Francisco, USA, July 11-14, 2022
• V. Zieger, D. Frejek, G. Miotto, L. Riek, S. Zimmermann, P. Koltay, R. Zengerle, S. Kartmann
  Selective and automated high-throughput deposition of spheroids for scalable 3D-bioprinting
  2022 Biofabrication 2022, Pisa, Italy, September, 25-28, 2022
• F. Koch, L. Riek, D. Frejek, L. Zausch, S. Zimmermann, S. Kartmann, R. Zengerle, A. Osorio-Madrazo, P. Koltay
  Towards standardized characterization of droplet-based bioprinting processes
  2022 Biofabrication 2022, Pisa, Italy, September, 25-28, 2022
• T. Lange, T. Groß, Á. Jeney, J. Scherzinger, E. S. C. Niemöller, S. Zimmermann, P. Koltay, F. von Stetten, R. Zengerle, C. Jeney
  Validation of scRNA-seq fold changes by single-cell reverse transcription digital PCR
  2022 Single-Cell Genomics, Gordon Research Conference, Les Diablerets, VD, Switzerland, May 1- 6, 2022
• S. Hennig, Z. Shu, L. Gutzweiler, P. Koltay, F. von Stetten, R. Zengerle, S. M. Früh
  “Paper-based open microfluidics platform for automatic protein analysis
  2022 SLAS Europe 2022 Conference and Exhibition, Dublin, Ireland, May 26, 2022

2021

• J. Weygant, F. Koch, K. Troendle, G. Finkenzeller, R. Zengerle, S. Kartmann, S. Zimmermann, P. Koltay
  Drop-on-Demand Bioprinting Approach For Precise Alignment and Interaction Studies of Different Cell Types
  2021 International Conference on Biofabrication, Australia, 27. – 29.09.2021 (online)
• K. Tröndle, A. Itani, F. Koch, R. Zengerle, P. Koltay, S. Zimmermann
  Drop-on-demand bioprinting solutions for the fabrication of 3D cell culture systems
  2021 DECHEMA 3D Cell Culture Freiburg (online), 05.-07.05.2021
• Z. Khan, Z. Shu, R. Zengerle, P. Koltay
  Hybrid 3D printing of polymer and solder to create functional 3D electronics
  2021 EPoSS Annual Forum 2021, Freiburg, 04.-07.10.2021
• F. Koch, K. Tröndle, G. Finkenzeller, P. Rukavina, R. Zengerle, P. Koltay, S. Zimmermann
  Hybrider 3D-Biodruck zur künstlichen Herstellung von Knochen / Using hybrid processes for 3D-bioprinting of artificial bone tissue
  2021 MST-Kongress, Ludwigsburg, 08.-10.11.2021

2020

• A. Brunauer, B. Breiner, S. Hennig, D. Kainz, R. Verboket, B. Johannsen, D. Baumgartner, K. Mitsakakis, L. Gutzweiler, Z. Shu, P. Koltay, T. Hutzenlaub, N. Paust, R. Zengerle, F. von Stetten, S. M. Früh
  Actuation principles for bioanalytical platforms to combat infectious diseases
  2020 Virtual EMBL Conference: Microfluidics: Designing the Next Wave of Biological Inquiry 2020, 13.-15.07.2020
• K. Tröndle, A. Itani, F. Koch, R. Zengerle, S. Zimmermann, P. Koltay
  Fabrication and fluidic integration of self-assembled cellular microtubules for nephron-on-chip applications
  2020 MicroTAS 2020, 04.-09.10.2020, virtual

2019

• S. Kartmann, D. Kopp, M. Masoumi, R. Zengerle, H. Zappe, P. Koltay
  Thermischer Einweg-Strömungssensor auf Basis einer flexiblen Polyimid-Folie
  2019 MicroTEC Südwest Clusterkonferenz, Freiburg, 20.-21.03.2019
  » show abstract« hide abstract
  Abstract

  ---
• C. Siber, L. Lautscham, J. Schoendube, P. Reichert, F. Stumpf, S. Zimmermann, R. Zengerle, P. Koltay
  Effective acoustic field generation in diposable dispensing cartridges for acustophoretic particle focusing
  2019 Transducers 2019, Berlin, 23.06. - 27.06.2019
• Z. Shu, B. Gerdes, M. Fechtig, R. Zengerle, P. Koltay
  Highly conductive flexible and 3D metallization on flexible and textile substrates via StarJet Technology
  2019 12th International Symposium on Flexible Organic Electronics (ISFOE19) 1-4 July 2019, Thessaloniki, Greece
  » show abstract« hide abstract
  Abstract

  Highly conductive metallizations are crucial for large area organic and printed electronics. State-of-the-art printing technologies such as inkjet printing and screen printing are still facing critical challenges regarding achieving high electrical conductivity and reducing the manufacturing costs. Moreover, additional post-processes such as thermal, photonic or laser sintering are either not compatible with the flexible substrates or expensive. On the contrary, the non-contact StarJet printing technology provides direct metallization from molten metal microdroplets and continuously Jet. It bases on a pneumatically driven printhead that features a heatable reservoir and an interchangeable nozzle chip with a star-shaped orifice geometry. Thanks to the pneumatic driven mechanism, materials with high melting temperature such as solder or aluminium alloys can be printed. Single-pass conductive features, printed via StarJet, exhibit high electrical conductance (7.5 Ω/m for 250 μm linewidth), high aspect ratio, i.e. high layer thickness (70 – 300 μm), and require no post-treatment. Examples of electrically functional, direct metallization were demonstrated on silicon solar cells and PCB boards. In this contribution, we demonstrate that the StarJet technology is also compatible with temperature sensitive flexible substrates such as polymer foils and textiles. The printed solder lines exhibit not only high electrical conductance but also high mechanical stability (i.e. adhesion) and high flexibility. The printed solder lines on polymer foils and textile can stand shear forces of up to 3000 mN and at the same time tolerate substrate bending at the radius of 5 mm. Furthermore, because the printed solder droplets fuse together, freestanding structures with different angles can also be printed via controlling process parameters. In summary, the StarJet technology shows high potential in direct metallization for large area flexible and wearable electronics and 3D electronic applications.
• F. Koch, M. Wehrle, K. Tröndle, P. Koltay, G. Finkenzeller, R. Zengerle, S. Zimmermann
  Rapid assessment of combined drop on demand and extrusion-based bioprinting with controlled shear stress and high shape fidelity
  2019 Transducers 2019 - EUROSENSORS XXXIII 23. -27. Juni 2019 - Berlin, Germany
  » show abstract« hide abstract
  Abstract

  We present a novel combination of drop on demand (DoD) and extrusion-based bioprinting to generate highprecision patterns of cells inside large hydrogel volumes. Extrusion-based bioprinting has the great advantage of enabling a fast deposition of high viscous cell-loaded hydrogel with reasonable precision. Compromises between high shape fidelity and cell viability, as well as short process times often require many iterations of optimizing process parameters and varying compositions of the hydrogel. To limit the multitude of parameters during extrusion-based bioprinting, a method for rapid process assessment was developed. This enables to define limits for printing temperature, flow rate and nozzle size from basic rheological measurements with regard to the biological and mechanical requirements. The combination of extrusion-based bioprinting with DoD bioprinting allows for precise deposition of low viscous cell suspension and adjustable concentrations of crosslinking agent. Together, the technologies were used to print a bone replacement model by using the predefined process parameters. Adiposed-derived stem cells (ASC) prone to osteogenic differentiation were homogenously extruded in a cuboid structure of 10x10x5 mm. Human umbilical vein endothelial cells (HUVEC) were printed as highly dense cell suspension lines inside the extruded hydrogel to allow a potential vascularization of the structure in vivo.
• F. Koch, M. Wehrle, K. Tröndle, P. Koltay, G. Finkenzeller, R. Zengerle, S. Zimmermann
  Rapid assessment of extrusion based bioprinting by controlling shear stresses on cells
  2019 Transducers 2019, Berlin, 23.06. - 27.06.2019
• P. Koltay
  Towards a generic 3D-Bioprinting Platform
  2019 IS2M Annual Meeting, 3D & 4D printing in Upper Rhine Valley, Mulhouse/France, 06. - 07. 06. 2019

2018

• C.-H. Tsai, D.- H. Kuan, S. Zimmermann, J. Schoendube, A. Gross, R. Zengerle, P. Koltay
  A highliy parallel microbioreactor for cell line development based on a microtiter plate with functional microfluidic lid
  2018 MicroTAS 2018, 11. -15. November 2018, Kaohsiung / Taiwan
• K. Tröndle, S. Kartmann, L. Gutzweiler, R. Zengerle, P. Koltay, S. Zimmermann
  Bioprinting with spheroids: Automated large-scale production and deposition
  2018 3D Cell Culture 2018, 5. - 7. Juni 2018, Freiburg
• Z. Shu, B. Gerdes, M. Fechtig, L. Riegger, R. Zengerle, P. Koltay
  Direct Printing of Conductive Metal Lines from Molten Solder Jets via StarJet Technology on Thin, Flexible Polymer Substrates
  2018 NIP & Digital Fabrication Conference, Printing for Fabrication 2018, Dresden, 23. – 27.09.2018 Society for Imaging Science and Technology.
• Z. Shu, B. Gerdes, M. Fechtig, L. Riegger, R. Zengerle, P. Koltay
  Direct Printing of Conductive Metal Lines from Molten Solder Jets via StarJet Technology on Thin, Flexible Polymer Substrates
  2018 NIP & Digital Fabrication Conference, Printing for Fabrication 2018 Society for Imaging Science and Technology, volume: 2018, issue: 1, pages: 72 - 75
  » show abstract« hide abstract
  Abstract

  We present the direct printing of thin (linewidth of 70 μm) conductive lines from molten solder on thin, flexible substrates. The lines are generated via the so-called StarJet technology that enables the printing of micro jets from molten metal. In this work, metal lines are printed for the first time on flexible substrates, possibly enabling applications in the field of printed electronics. The printed lines are evaluated regarding their mechanical and electrical properties. To the knowledge of the authors, this is the first time that direct printing of a functional metallization, requiring no further treatment, on a flexible polymer substrate was demonstrated. The lines exhibit a low ohmic resistance and can endure shear forces of up to 3.5 N on polyethylene terephthalate (PET) substrates.
• P. Koltay
  Towards a generic 3D-Bioprinting Platform
  2018 International Conference on Biofabrication, Würzburg, 28. – 31.10.2018
  » show abstract« hide abstract
  Abstract

  ; “”, (2018), International Conference on Biofabrication, Würzburg, 28. – 31.10.2018
• C. Siber, F. Stumpf, J. Schöndube, S. Zimmermann, P. Koltay, L. Lautscham
  Velocity field analysis of acoustophoretic focusing in a single-cell printing system
  2018 Acoustofluidics, Lille/France, 29. – 31.08.2018

2017

• S. Zimmermann, J. Riba, R. Zengerle, P. Koltay
  A single-cell printer as a versatile tool for cell line development and single-cell analysis
  2017 LAPASO - Microfluidics for label-free particle sorting, Lund / Sweden, 05. - 06.09.2017
  » show abstract« hide abstract
  Abstract

  Single-cell analysis emerged as a promising approach to decipher the heterogeneity of complex cell populations such as tumors. Furthermore, the proof of monoclonality is a regulatory requirement in cell line development, where a cell population producing a therapeutic protein in a bioreactor has to originate from a single cell. Within the advent of such diverse applications, a number of single-cell isolation technologies have been developed and adapted for different requirements [1]. Limitations of these technologies regarding the uniqueness and the integrity of the cells can be overcome by a single-cell printer (scp), a laboratory device developed by the University of Freiburg and commercialized by the spin-off company cytena.
• S. Kartmann, F. Koch, A. Ernst, R. Zengerle, P. Koltay
  A single-use in-line flow sensor fore closed-loop controlled precise non-contact liquid dispensing
  2017 MFHS, Twente / The Netherlands, 04. - 06.10.2017
  » show abstract« hide abstract
  Abstract

  This paper reports on a closed-loop controlled non-contact liquid dispensing system. The system employs a control algorithm and consists of a single-use in-line flow sensor and a disposable electromagnetic dispensing valve. By measuring the flow rate in real time, the system can control the opening time of the valve and is thus able to react to potential environmental influences such as pressure or temperature fluctuations. Furthermore, the system has the advantage that all fluid-carrying components can be exchanged after use, therefore cost intensive cleaning steps can be avoided. The precision of the system was demonstrated experimentally for different volumes in the range of 2:8 ml to 4:9 ml. The resulting coefficient of variation (CV) was below 2 %.
• C.H. Tsai, S. Zimmermann, R. Zengerle, P. Koltay
  An autonomous microbioreactor based on a functional lid in 96-well microplate format
  2017 MFHS, Twente / The Netherlands, 04. - 06.10.2017
  » show abstract« hide abstract
  Abstract

  We have developed an integrated microbioreactor (MBR) based on a disposable functional lid (FL) and a standard microtiter plate (MTP), which only requires one pressure source for parallel and reciprocal mixing of cells cultured in suspension in the MTP as a prerequisite in pharmaceutical cell line development (CLD). The mixing principle of the FL does not only allows for working with significantly smaller culture volumes (30 μl), but also reduces the requirements of external processing stations.
• J. Riba, H. Becker, P. Koltay, R. Zengerle, S. Zimmermann
  Assay miniaturization for the genetic analysis of individual cells enabled by single-cell printing and nanoliter liquid handling
  2017 Keystone Symposia Conference – Single Cell Omics, Stockholm, Sweden, 26. -30.May 2017
  » show abstract« hide abstract
  Abstract

  Automated single-cell isolation and low volume liquid handling for reagent cost reduction are needed to mature single-cell sequencing assays into routine clinical analysis methods. Here, we combine our single-cell printer (scp) for the isolation and deposition of individual cells with non-contact dispensing for reagent dosage in the nanoliter range. This enables us to downscale the reaction volumes of a single-cell whole-genome-amplification (WGA) assay from 50 µl to 2.5 µl using standard 384-well PCR plates.
• S. Zimmermann, J. Schoendube, A. Gross, B. Steimle, L. Lautscham, K. Pfleghar, T. Christmann, B. Werdelmann, F. Koch, J. Riba, P. Koltay, R. Zengerle, M. Pirsch
  Cell line development by single-cell printing and cell imaging
  2017 Cell Line Development & Engineering, Amsterdam, 23.-25. April 2017
  » show abstract« hide abstract
  Abstract

  In biopharmaceutical production the proof of monoclonality is a regulatory requirement for the development of clonal cell lines. A complementary approach based on a single-cell printer (scp, cytena GmbH) and a NYONE cell imager (SYNENTEC GmbH) is used to produce truly monoclonal cell lines and compared to standard single-cell isolation technologies like limited dilution and FACS. Different CHO cell lines were used on different microtiter plate types in addition to cell-equivalent beads for testing the system.
• C.H. Tsai, X.Y. Wu, S. Zimmermann, R. Zengerle, P. Koltay
  Digital Hydraulic Drive For Microfluidic Large-scale Integration System Based On Shape Memory Alloy Actuators
  2017 Transducers 2017, Kaohsiung/Taiwan, 18.-22.06.2017,
  » show abstract« hide abstract
  Abstract

  We present a small size and low power Digital Hydraulic Drive (DHD) intended for use in miniaturized and portable control systems for microfluidic large-scale integration (mLSI) chips. The main components of a DHD are a pneumatic cylinder and a shape memory alloy (SMA) actuator. Depending on different types of SMA actuators, the DHD is not only able to provide digital hydraulic pulses (switching time smaller 1 s), but can maintain a steady state up to 24 hours. A single DHD enables to control 256 valves in parallel.
• B. Gerdes, M. Jehle, M. Domke, R. Zengerle, P. Koltay, L. Riegger
  Drop-on demand generation of aluminium alloy microdroplets at 950 °C using the Strarjet technology
  2017 Transducers 2017, Kaohsiung/Taiwan, 18. – 22.06.2017
  » show abstract« hide abstract
  Abstract

  We present the drop-on-demand generation of liquid microdroplets from aluminum alloy melts with minimum diameters of 235 μm. The so-called StarJet technology, used to generate the droplets features a pneumatically actuated printhead that has been used to print microdroplets from solder (Tmelt 220 °C) before. In this work a novel StarJet printhead is presented that can be operated at up to 950 °C and thus allows for printing of aluminum alloys. The printhead is compatible with chemically aggressive metal melts and can be operated in a standard laboratory environment. Experimental results regarding the generation of droplets and a printed aluminum structure are presented. To the knowledge of the authors this is the first time that aluminum alloy microdroplets of such small size (d = 235 μm) have been produced by drop-on-demand.
• J. Riba, J. C. Niemöller, N. Renz, S. Bleul, J. M. Stosch, P. Koltay, R. Zengerle, R. Claus, H. Becker, S. Zimmermann
  Genetic Analysis of Individual Cancer Cells Isolated via Single-Cell Printing
  2017 Single-Cell Genomics Workshop Paris, Paris/France, 27. - 28.06.2017
  » show abstract« hide abstract
  Abstract

  Single-cell genomics emerged as a promising tool to analyze the heterogeneity of complex cancer cell populations by characterizing the genome of each individual cell. In acute myeloid leukemia (AML), single-cell sequencing in addition to bulk next generation sequencing (NGS) is particularly useful for deciphering complex clonal architectures. Here, we present an efficient workflow based on an advanced Single-Cell Printer (scp) for the study of gene variants in single cancer cells. The ejection efficiency was 99.7% for fluorescent beads (n = 2304) and 98.7% for human cells (U-2OS or Kasumi-1 cancer cell line, or AML patient; n = 150). Per fluorescence microscopy, 98.8% of beads were correctly delivered into the wells. A subset of single cells (n = 81) was subjected to whole genome amplification (WGA), which was successful in all cells. On empty droplets, a PCR on LINE1 retrotransposons yielded no product after WGA, verifying the absence of free-floating DNA in SCP-generated droplets. Representative gene variants identified in bulk specimens were sequenced in single-cell WGA DNA. In U-2 OS, 22 of 25 cells yielded results for both an SLC34A2 and TET2 mutation site, including cells harboring the SLC34A2 but not the TET2 mutation. In one cell, the TET2 mutation analysis was inconclusive due to allelic dropout, as assessed via polymorphisms located close to the mutation. Of Kasumi-1, 23 of 33 cells with data on both the KIT and TP53 mutation site harbored both mutations. In the AML patient, 21 of 23 cells were informative for a TP53 variant; the identified alleles matched the loss of chromosome arm 17p. The advanced SCP allows efficient, precise and gentle isolation of individual cells for subsequent WGA and routine PCR/sequencing-based analyses of gene variants.
• S. Kartmann, F. Koch, R. Zengerle, P. Koltay, A. Ernst
  Single-use flow sensor based on the differential pressure principle employing the radial expansion of a low-cost silicone tube
  2017 Transducers 2017, Kaohsiung/Taiwan, 18. – 22.06.2017
  » show abstract« hide abstract
  Abstract

  For the first time, we present a flow sensor consisting of low-cost consumable parts, to minimize the risk of cross-contamination in medical applications, for example. For our sensor, the consumable component consists of two simple silicone tubes and a capillary, which can be exchanged easily and cost-effectively after use. We characterized the flow sensor in the range from 0 up to 50 μL/s. The sensor showed a good consistency with the reference sensor, a linear correlation coefficient of minimal R(x,y) = 0.98 and a sensor resolution of 0.4 μL/s.
• F. Koch, S. Kartmann, R. Zengerle, A. Ernst, P. Koltay
  Viscosity determination by the in-line measurement of liquid flow time through a cylindrical tube
  2017 MFHS, Twente / The Netherlands, 04. - 06.10.2017
  » show abstract« hide abstract
  Abstract

  This paper demonstrates a novel in-line viscosity measurement concept, with reduced effort compared to common approaches. It determines the transition-time of a liquid/gas front to fill a well-defined capillary. In contrast to previous work [1] this paper measures the transition-time for the first time in a non-contact capacitive way. The method enables to determine the dynamic viscosity with a mean coefficient of variation (CV) of 8.4% for a measuring range between 1 and 20 mPa s and showed to be valuable as a fast viscosity calibration for flow sensors using the differential pressure principle.

2016

• T. Gleichmann, B. Hamouda, L. Gutzweiler, M. A. Graewert, R. Zengerle, P. Koltay, L. Riegger
  Analytical protein affinity chromatography in nl volumes in on-demand written liquid lines
  2016 20th International Conference on Miniaturized Systems for Chemistry and Life Sciences, µTAS 2016, Dublin / Irland, 09. – 13.10.2016
• S. Zimmermann, J. Schoendube, A. Gross, B. Steimle, T. Christmann, B. Werdelmann, P. Koltay, M. Pirsch
  Establishing clonal cell lines by single-cell printing and cell imaging
  2016 Cell Line Development & Engineering, Wien (AU), 11. - 13.04.2016
  » show abstract« hide abstract
  Abstract

  The proof of monoclonality is a regulatory requirement for the development of clonal cell lines for biopharmaceutical production. Here we describe a complementary approach based on a single-cell printer (SCP, cytena GmbH) and a NyONE cell imager (SynenTec GmbH) to produce truly monoclonal cell lines derived from CHO-K1 cell progenitors with high efficiencies.
• L. Gutzweiler, T. Gleichmann, P. Koltay, R. Zengerle, L. Riegger
  Open Microfluidics for Lab-on-a-Chip Applications
  2016 2016 International Conference of Microfluidics, Nanofluidics and Lab-on-a--Chip, Dalian/China, June 10-12, 2016
  » show abstract« hide abstract
  Abstract

  In this work we introduce bioanalytical applications previously realized on lab-on-chip devices that have been successfully transferred to the field of open microfluidics (OM). Open microfluidic systems are microfluidic networks on planar substrates without being enclosed by solid interfaces and thus not having rigid boundaries [1]. Applications in open microfluidic systems can be conducted on-demand with often less amounts of reagents required. Furthermore, time consuming & cost intensive fabrication of microchips can be omitted using planar low-cost polymer substrates. In this work, we present DNA and protein electrophoresis as well as microbatch protein crystallization in an open microfluidic environment.
• J. Riba, J.C. Niemöller, J. Schoendube, A. Gross, S. Bleul, R. Claus, J. Duyster, H. Becker, P. Koltay, R. Zengerle, S. Zimmermann
  Single-Cell Printing for the genomic analysis of eukaryotic and prokaryotic cells
  2016 Single Cell Biology, Hinxton, UK, 8-10 March 2016
  » show abstract« hide abstract
  Abstract

  Single-cell genomics emerged as a promising tool to analyze the heterogeneity of complex cell populations by characterizing the genome of each individual cell. Prerequisite for precise single-cell genomic analysis is an efficient cell isolation. Conventional isolation workflows or instruments are often not able to isolate both eukaryotic and prokaryotic cells or require complex and cost-intensive devices. We previously demonstrated that the Single-Cell Printer (SCP) allows for isolating and depositing individual mammalian cells with high viability rates for monoclonal culturing. Similar to an inkjet printer, the SCP uses a piezo-driven dispenser chip to generate free-flying micro-droplets. A camera system coupled with computer-assisted image processing enables the detection of cells in the chip nozzle and the printing of droplets containing exactly one cell. Here, we demonstrate an advanced SCP that is capable of isolating individual eukaryotic and prokaryotic cells down to 1 µm in size for subsequent single-cell genomic analysis. Using a commercially available whole-genome amplification (WGA) kit (Qiagen REPLI-gTM) with reduced reaction volumes, the genomes of 25 individually printed mammalian cancer cells (U2OS osteosarcoma cell line) were amplified with 100 % success rate as quantified with a QubitTM assay. Eight representative WGA samples were analyzed by Sanger sequencing revealing the U2OS-specific mutations in the SLC34A2 (c.1538G>T) and TET2 (c.1394C>T) genes. We further amplified the genome of 14 individual bacteria cells (E.coli and E.faecalis) with 93 % success rate. Finally, we sequenced part of the 16S rRNA gene of individual bacteria cells enabling the successful taxonomic classification on a phylum level. In conclusion, we show that the SCP allows for efficient and highly automated single-cell deposition of both eukaryotic and prokaryotic cells. Furthermore, the data demonstrate the applicability of the SCP for the analysis of genetic aberrations in single cancer cells at the base pair level and for 16S rRNA-based taxonomic classification of individual microorganisms.

2015

• J. Riba, T. Gleichmann, P. Koltay, R. Zengerle, S. Zimmermann
  A new tool for label-free isolation and deposition of single bacteria cells
  2015 New Approaches and Concepts in Microbiology, EMBL Heidelberg, Germany, 11.-14. October 2015
  » show abstract« hide abstract
  Abstract

  Increasing interest in single-cell analysis throughout life sciences and industry has aroused demand for technologies to separate and handle individual cells. We previously demonstrated that the Single-Cell Printer (SCP) can be used to sort and deposit single mammalian cells onto various substrates for subsequent monoclonal culturing and single-cell genomics. The SCP exploits drop-on-demand printing and automatic image recognition to print 35-200 pl droplets containing single-cells. Compared to other technologies like FACS systems the SCP can address various substrates with high precision and employs a disposable cartridge to prevent cross-contamination. Here, we present an advanced version of the instrument with high-resolution optical detection that has been developed with the aim to detect and deposit bacterial cells. For the first time, we show label-free deposition of single bacterial cells using the SCP. By printing single-cell arrays of GFP expressing E. coli we found that the single-cell printing efficiency of our first prototype yields 78 %. We further demonstrate that the instrument can be used to separate individual cells from a heterogeneous sample followed by clonal culturing. Therefore, we deposit arrays of 100 individual cells from a mixture of E. faecalis and E. coli directly on agar plates for subsequent incubation overnight. After 10 hours we count on average 66 clearly visible clonal cultures. Using light microscopy we show that the two strains were evenly printed and resulted in clonal colonies. In the future we aim to apply the technology to enable highly automated single-cell genomics for phylogenetic studies of environmental samples and to finger-printing of rare bacterial species from clinical samples via mass spectroscopy.
• B. Gerdes, N. Lass, M. Jehle, L. Riegger, R. Zengerle, P. Koltay
  Direct printing of molten metal lines using the StarJet technology
  2015 Swiss ePrint, Neuchatel, Switzerland, 01. - 02. October 2015
  
   
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• N. Lass, B. Gerdes, M. Jehle, L. Riegger, R. Zengerle, P. Koltay
  Generation of High Aspect Ratio Metal Microstructures Exhibiting Low Surface Roughness by Drop-wise Printing of Liquid Metal
  2015 Eurosensors 2015, Freiburg, 06.- 09.09.2015 Procedia Engineering, volume: 120, pages: 1103 - 1106
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  Abstract

  This paper presents the results of parameter studies for the drop-wise generation of metal microstructures from liquid metal. In this context, thin walls (170 μm---180 μm thickness) featuring aspect ratios of over 50 are printed from solder droplets to identify the correlation between printing parameters and resulting material properties. Droplet spacing as well as substrate temperature are varied and the resulting surface quality in terms of roughness is evaluated. Best results, for given boundary conditions, are achieved with a relative droplet spacing of 0.65 in combination with a substrate temperature of 140 °C. Based on printing with droplets of 170 m diameter a printed area surface roughness of 9.35 m is achieved.
• S. Kartmann, P. Koltay, R. Steger, R. Zengerle, A. Ernst
  Injection-molded, consumable, non-contact dispensing valve applicable for 96-well plate processing
  2015 SLAS 2015, 4th Annual Conference and Exhibition in Washington, DC, USA, 07.-11.02.2015
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  Abstract

  The presented work focusses on the fabrication by an injection molding process of a cost-effective, disposable, non-contact dispensing valve for cross-contamination free applications. The valve allows a super silent multi-channel processing of well plates in standard 96-well format. The implementation of a design capable for the fabrication in injection molding could be realized with performance improvements concerning reproducibility and with enhanced handling properties. The requirements of industry and research on the dispensing performance of liquid handling systems in terms of minimal dosing volume, precision and accuracy as well as throughput and analysis costs are increasingly growing. Also the risk of cross-contamination implies the demand of disposable components and non-contact technologies. Since such systems are hardly available on market, we focus on the implementation of a system providing a comprehensive solution for the entire set of industrial specifications. The developed functional model of the valve presented in [1] was fabricated by a 3D printing process to approach the given requirements. This valve revealed several disadvantages, like it’s large outer diameter with an overall size of 16 mm, the huge temperature coupling into the fluid induced by required high coil currents (I = 10 A) which affects the viscosity of the fluid and leakage problems of the two-part valve body assembly for actuation pressures above 1.5 bar. To enable a multichannel application for parallel filling of 96-well plates, the dimensions of the valve were optimized to fit in a 9 mm pitch. Therefore, the outer diameter of the valve including external actuating coil was reduced from 16 mm to 8.5 mm. The smaller dimensions allowed a reduction of the actuation current by 60%. Consequently, the heat transfer, thus the effect on the dispensing performance, could be reduced enormously. In contrast to the functional model, the novel valve consists of a one-part valve body, which solves the previous leakage problem. An inserted stopper defines the maximum plunger movement. The entire valve design is adapted to the fabrication by an injection molding process in polypropylene to implement cost effectivity and the compatibility to medical applications. It is now possible to dispense target volumes with CV’s less than 2% for a volume range between 230 nL and 2 µL and CV < 1% for a volume range between 2 µL and 20 µL. Furthermore, we were able to adjust the desired volume range and flow rate by using nozzles with different dimensions. In conclusion, the performance is very comparable to similar commercially available systems with the advantage, that the material costs stay under 1 €. The reduced size and the standard Luer-Lock interface make the dispensing valve compatible to a wide range of applications in biomedical technology.
• J. Riba, T. Gleichmann, R. Zengerle, P. Koltay
  Label-free sorting and deposition of single bacterial cells using the Single-Cell Printer technology
  2015 6th International conference on analysis of microbial cells at the single cell level, Retz/Austria, 19. - 22. Juli 2015
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  Abstract

  We present a modified Single-Cell Printer (SCP) for sorting and deposition of individual bacterial cells by: •Label-free optical cell detection •Confinement of single cells in 35 picoliter droplets •Non-contact drop-on-demand deposition onto a variety of substrates We show that Escherichia coli cells can be deposited with a single cell printing efficiency of 78 %. Further, we deposited individual cells from a heterogeneous sample directly onto agar plates for subsequent clonal culturing.
• T. Gleichmann, J. Kottmeier, P. Koltay, R. Zengerle, L. Riegger
  Open Surface Batch Crystallization of Proteins on an Automated Non-Contact nL-Dispenser Setup
  2015 19th International Conference on Miniaturized Systems for Chemistry and Life Sciences October 25-29, 2015, Gyeongju, KOREA
• S. Kartmann, P. Koltay, R. Zengerle, A. Ernst
  Pressure transducer for medical applications
  2015 BMT 2015 (49. Jahrestagung der Deutschen Gesellschaft für Biomedizinische Technik (DGBMT) im VDE), 16.-18. September, Lübeck
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  Abstract

  Particularly in the field of medical applications, full- or partly disposable pressure sensors are needed to implement cross-contamination-free monitoring solutions e.g. for infusion systems or process control for in vitro diagnostic (IVD) applications. The demand for reliable, single-use technologies increases rapidly, driving forward the investigation of innovative measuring principles.
• S. Kartmann, P. Koltay, R. Zengerle, A. Ernst
  Pressure transducer for medical applications employing radial expansion of a low-cost polymer tube
  2015 Eurosensors 2015, Freiburg, 06.- 09.09.2015 Procedia Engineering, volume: 120, pages: 1213 - 1216
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  Abstract

  We present a low-cost pressure transducer for medical applications. It’s based on the radial expansion of a liquid filled elastic tube, which is detected by a capacitive measuring principle in a non-contact manner. For optimization we investigated the influence of the number and arrangement of the measurement electrodes, their length as well as the gap separating them. The optimized electrode geometry features a sensitivity of 0.195 fF/103 Pa and a corresponding mean coefficient of variation (CV) of 6.4% considering three individual transducer assemblies. The transducer performance was investigated applying pressures up to 50 x 103 Pa. Due to a viscoelastic behavior of silicone material we determined a hysteresis effect which implied a maximum error of 1.13 fF implying a pressure error of 5.8 x 103 Pa.
• J. Riba, J. C. Niemöller, S. Zimmermann, J. Schoendube, S. Bleul, P. Koltay, R. Zengerle, R. Claus, H. Becker, A. Gross
  Single-cell printing for the genetic analysis of cancer cells
  2015 Single cell genomics 2015, Utrecht, The Netherlands, 16. – 18. September 2015
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  Abstract

  We present a workflow for the isolation and genetic analysis of single cancer cells based on a Single-Cell Printer (SCP): • Printing of single cells from the osteosarcoma cell line U2OS in wells of a 384-well microtiter plate (MTP) • Whole genome amplification (WGA) of single-cell DNA at reduced reagent volumes • Multiplex PCR on LINE1 retrotransposons • Analysis of U2OS-specific mutations Following this workflow, a single-cell printing efficiency of 98% and uniform DNA yields after WGA were achieved. LINE1 retrotransposons could be detected in all WGA samples, and mutations in the TET2 and the SLC34A2 gene, respectively.

2014

• L. Riegger, A. Ernst, P. Koltay
  A dispensing system for sedimenting metal microparticle solutions based on a circulation mixer method
  2014 2nd MFHS Conference 2014, Freiburg, 08 - 10.Okt. 2014 , pages: 81 - 83
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  Abstract

  We present a novel method for the ejection of sedimenting microparticle solutions by a non-contact drop-on-demand dispensing system with integrated mixing technology. The system enables the generation of single liquid droplets in the nanoliter range containing similar amounts of solids. The system is evaluated for a process time of more than 4 h and is applied to produce particle layers with homogeneous layer thicknesses in the micrometer range.
• S. Kartmann, A. Ernst, R. Zengerle, P. Koltay
  A disposable, dispensing valve for non-contact microliter applications in 96-well plate format
  2014 2nd MFHS Conference 2014, Freiburg, 08 - 10.Okt. 2014 , pages: 65 - 68
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  Abstract

  We present a miniaturized, disposable dispensing valve for the microliter range, applicable as consumable to process 96-well plates. The new valve design is adapted to fit into a 9 mm grid and derives from the miniaturization study of a previous functional model [1]. The outer diameter of the valve, including actuating coil, was reduced from 16 mm to 8.5 mm without performance restrictions, thus made compatible for 96-well plate processing. Also the actuation current was reduced from 10 A to 5 A. The valve enables the dosage of target volumes in the range between 230 nL and 5 μL with coefficients of variation (CVs) below 2%. The current performance coincides with similar commercially available systems with the decisive advantage of material costs below 1 €.
• F. Stumpf, L. Gutzweiler, L. Tanguy, P. Koltay, R. Zengerle, L. Riegger
  A flexible method for rapid-prototyping of PDMS microfluidic chips for droplet based applications using direct-written polymer master structures
  2014 Biosensors 2014, Melbourne, Australia, 27.05.2014 – 30.05.2014
• J. Riba, L. Gutzweiler, L. Riegger, P. Koltay, R. Zengerle, A. Gross
  A picoliter dispenser with disposable cartridges for precise and contact-free injection of DNA into open microfluidic structures
  2014 2nd MFHS Conference 2014, Freiburg, 08 - 10.Okt. 2014 , pages: 84 - 87
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  Abstract

  We present a new disposable liquid handling system addressing the lower picoliter volume range and allowing for precise and contact-free injection of biopolymer samples into open microfluidic structures. Droplet placement precision of single stranded DNA (ssDNA) solutions up to 50 μM and a DNA reference ladder is investigated by high resolution optical monitoring. We present three different sample injection methods that account for evaporation protection of picoliter samples. Finally, we show the applicability of the dispenser by a successful electrophoretic separation via injecting ~70 pL of a DNA solution into a 200-300 μm wide gel line.
• A. Madjarov, W. Streule, B. Schaub, R. Zengerle, P. Koltay, A. Ernst
  Going low Volume – A Nanoliter Dispensing Module for Standard Liquid Handling Robots
  2014 Advances in Automation & Robotics (Co-located to 4th European Lab Automation Exhibition), Barcelona, Spain, 13. - 15.05.2014
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  Abstract

  The dispensing system implements a wireless eight channel nanoliter dispenser. It is built at a footprint of just a standard SBS well plate, thus can be placed on available deck-tray positions of existing pipetting workstations as an add-on component. By extending their volume range to the lower end, completely new prospects for high-throughput-screening, miniaturized assays and other applications arise. The droplet ejection method is based a piezo-driven piston squeezing a disposable dispensing tube to eject free flying droplets. This dispensing Technology is called PipeJetTM and to make it ready for automated handling, novel dosage elements (PipeJet-Tip) were developed. These PipeJet-Tips are compatible to standard pipetting interfaces and injection molded including the 650 µm dispensing tube and the reservoir. A new tip generation is completely molded in polypropylene and therefore, a very low cost disposable dispensing element. The plug-in system is able to address eight individual dispensing channels to imprint custom droplet patterns with single droplet volumes down to 20 nl (CV < 5%). Rechargeable batteries as power supply and wireless communication housed inside the system enable the autonomous working principle and therefore easy integrate ability of the dispensing module.
• J. Schoendube, A. Gross, R. Zengerle, P. Koltay
  Label-free Isolation of Single Cells by Inkjet-like Printing
  2014 Single Cell Analysis Europe 2014, Berlin, 10.-11.03.2014
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  Abstract

  Separation and manipulation of individual living cells for single cell analysis remains challenging for many life science applications, including single cell genomics, isolation of circulating tumor cells (CTC) and clonal cell line production. In order to provide a platform technology to feed single living cells into such applications, we have developed a liquid handling instrument termed Single Cell Printer. It is able to print single living cells confined in free flying droplets in an ink-jet like manner into well plates, into microfluidic chips or other substrates for subsequent single cell applications. A machine vision system detects single cells in proximity of the nozzle before droplet ejection. Droplets, predicted to contain no cell or more than one cell, are deflected by a pneumatic shutter system. Only droplets with exactly one single cell are printed onto the substrate.
• P. Koltay
  Metrological Methods for Low Volume Liquid Handling in Drug Delivery and In-Vitro Diagnostics
  2014 8th Workshop Low Flows in Medical Technology, Lübeck, 23. - 24.09-2014
• F. Stumpf, J. Schöndube, A. Gross, G. Roth, R. Zengerle, P. Koltay
  Non-contact single cell printing for single cell real-time PCR
  2014 Biosensors 2014, Melbourne, Australia, 27.05.2014 – 30.05.2014
• L. Gutzweiler, T. Gleichmann, P. Koltay, R. Zengerle, L. Riegger
  Semi-contact writing technology & applications
  2014 2nd MFHS Conference 2014, Freiburg, 08 - 10.Okt. 2014 , pages: 96 - 99
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  Abstract

  We present an adaption of a direct ink writing approach to facilitate prevalent standard applications like fabricating masters for PDMS casting, conducting path structuring and generation of open microfluidic structures towards gel electrophoresis. In all presented applications, flexibility is increased and standard structuring processes can be substituted offering the ability for low-cost fabrication with less required expertise. In contrast to existing approaches low to medium viscous liquids are applied due to passive capillary forces.
• S. Kartmann, M. Kellermann, R. Zengerle, P. Koltay, A. Ernst
  Simulation study of a novel capacitive pressure sensor concept based on the geometrical deformation of an elastic measuring cell
  2014 2nd MFHS Conference 2014, Freiburg, 08 - 10.Okt. 2014 , pages: 118 - 121
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  Abstract

  We present the simulative investigation of design rules for a novel pressure transducer to realize a disposable pressure sensor for medical applications. The presented simulation study is based on a threedimensional CFD-ACE+ model, which describes the expansion behavior of tubular, elastic measuring cells at varying inner hydrostatic pressures for and different boundary conditions like material properties or size. The elastic measuring cell is exposed to an electric field which is sensitive to the implied geometrical deformation, thus transduces a pressure change to a change in capacitance.
• T. Gleichmann, L. Gutzweiler, R. Zengerle, P. Koltay, L. Riegger
  Smart open microfluidics: an automated platform for the dynamic generation of fluidic structures down to the sub nl-range
  2014 2nd MFHS Conference 2014, Freiburg, 08 - 10.Okt. 2014 , pages: 161 - 164
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  Abstract

  We developed an open microfluidic (OM) [1] platform for the computer-assisted generation of fluidic structures virtually on demand. On using a set of piezo-driven dispenser modules, namely PipeJetTM [2] and Nano-Jet [3] (BioFluidix GmbH, Freiburg, Germany), and a peristaltic pump as well the system enables handling of liquids from the mL- down to the pL-range covering up to nine orders of magnitude in volume. The integration of multiple structuring methods like semi-contact writing (SCW) or non-contact dispensing allows for processing droplet arrays or continuous geometries of desired dimension, using low to medium viscous fluids and a number of different substrate materials.
• B. Gerdes, N. Lass, L. Riegger, R. Zengerle, P. Koltay
  StarJet-based, pneumatically actuated liquid metal droplet printing at up to 500 °C
  2014 2nd MFHS Conference 2014, Freiburg, 08 - 10.Okt. 2014 , pages: 57 - 60
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  Abstract

  In this work, we present a novel generation of pneumatically actuated printheads based on the StarJet technology which have been successfully applied for the direct non-contact printing of droplets from molten metal [1, 2]. This paper reports the technological advances of the newly designed printhead V3 which for the first time has been fabricated by selective laser melting (SLM). The StarJet technology features an inert rinse gas that surrounds the droplets inside the nozzle. V3 features an integrated heating for rinse gas which prevents the droplets from fast solidification and oxidation after ejection, as they are surrounded by hot nitrogen gas. The feasibility of the StarJet technology is demonstrated for printing at temperatures up to 500 °C. Moreover, the angular deviation of the droplets’ flight path has been investigated. A maximum angular deviation of 0.89° has been evaluated. The droplets’ velocity after ejection and the influence of the different pressures on this parameter have been investigated.

2013

• S. Bammesberger, I. Malki, A. Ernst, L. Tanguy, P. Koltay, R. Zengerle
  A Calibration-free, Disposable, Non-contact Reagent Dosing Cartridge for the Sub-μl Range
  2013 SLAS 2013, Orlando, Florida/USA, Jan. 12 - 16 2013
• L. Gutzweiler, F. Stumpf, L. Riegger, P. Koltay, R. Zengerle, L. Tanguy
  A flexible method for rapid-prototyping of PDMS microfluidic chips using direct-written polymer-master-structures
  2013 MicroTAS 2013, Freiburg, 27.10.- 31.10.2013 , pages: 1409 - 1411
• L. Tanguy, S. Bammesberger, A. Ernst, R. Zengerle, P. Koltay
  Autonomously compensated pressure controlled and driven dispenser for the IVD industry
  2013 European Lab Automation 2013 (ELA2013), Hamburg, 06. – 07.06.2013
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  Abstract

  The presented system is a novel, sensor controlled, non-contact fluid dispenser applicable down to the sub-microliter domain. A disposable syringe is filled with fluid and connected through a T-connector to a pressure sensor, which is separated from the liquid by an enclosed and defined gas volume. The other end of the T-connector is linked to a normally-closed solenoid dispensing valve. By displacement of the syringe plunger a defined pressure inside the enclosed gas volume can be established and controlled by the pressure sensor’s signal. The valve is opened to release a pressure driven liquid jet until a certain, pressure-dependent value A is reached. The ejected volume is linearly dependent on A and the dispensed volumes can be estimated with the pressure difference, before and after the dispensing. Thus the influence of temperature and viscosity variations can be compensated autonomously and in-between each dispense. The system was tested and used with several fluids exhibiting different viscosities in the sub-microliter domain with viscosities varying from 1 mPas to 16.69 mPas. Volumes range covered was from 500 nanoliter to 10 microliter. The standard deviations measured were 1.1% for water at 500 nanoliter and 0,8% for mixture water/glycerol 66 %wt at 1 microliter.
• D. Liang, J. Zhang, M. T.Govindaiah, L. Tanguy, A. Ernst, R. Zengerle, P. Koltay
  Benchmark of seven calibration technologies for non-contact micro liquid handling devices
  2013 European Lab Automation 2013 (ELA2013), Hamburg, 06. – 07.06.2013
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  Abstract

  The miniaturization of liquid handling devices is facing demanding requirement of accurate and standardized calibration methods for smaller volume range. For the first time seven different calibration technologies with the potential to be new standards in the nano-liter and sub-µl range have been benchmarked. In order to compare their efficiency on the same liquid aliquot, a novel, fully automated and multiple principles integrated calibration system has been developed. Single liquid aliquots in the range from pl to µl from a non-contact dispenser are characterized simultaneously with four online methods (the imaging, the flow sensing, the capacitive sensing and the optical sensing method) and one of the three offline methods (the dual-dye photometric, the gravimetric regression and the quartz crystal microbalance (QCM) method). Besides quantitative comparison all these methods are also benchmarked in a qualitative manner in concerning of working range, readability, user-friendliness, liquid suitability, integration size, tractability, cost of equipment and single calibration as well as handling steps etc. This comprehensive work provides the researchers and engineers in the liquid handling field the best overview of different calibration technologies and could support to establish a universal low volume liquid calibration standard for everyday lab situations.
• K. Mutschler, L. Tanguy, N. Weber, A. Ernst, R. Zengerle, P. Koltay
  Characterization of liquid jet injection into tissue based on optical coherence tomography
  2013 Transducers 2013, Barcelona, Spain, 16. – 18.06.2013 , pages: 1675 - 1678
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  Abstract

  We present the combination of high speed video monitoring, force measurement and Optical Coherence Tomography (OCT) as a new method for the characterization of liquid jets for needle-free tissue injection applications. It is well known that physical parameters, such as jet velocity and jet diameter determine the penetration characteristics of liquid micro-jets into a specific tissue [1]. The optimum injection parameters vary significantly for different types of tissues. Therefore, we have used high speed video monitoring and force sensor measurements to characterize the liquid jet. The penetration into the tissue is then analyzed by Optical Coherence Tomography (OCT) [2]. This enables the general description of the specific jet’s physical properties as well as the penetration characteristics with respect to a specific tissue. In the experimental study, jets with diameters of 100 μm and jet lengths from 6 to 18 ms (~ 2 to 9 μl) have been injected into colon tissue from pigs.
• L. Gutzweiler, L. Riegger, P. Koltay, R. Zengerle, L. Tanguy
  DNA Gelelektrophorese in offenen mikrofluidischen Systemen
  2013 Microsystemtechnik (MST) Kongress 2013, Aachen, 14. - 16.10.2013 , pages: 380 - 383
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  Abstract

  In diesem Beitrag wird die elektrophoretische Trennung von DNA in digital gedruckten offenen mikrofluidischen Linien präsentiert. Im Gegensatz zur gängigen, Chip-basierten Kapillarelektrophorese in mikrostrukturierten Glas-Chips, kommen bei diesem Ansatz mit Platin-Elektroden versehene, planare Polyimid-Substrate zum Einsatz. Eine mittels Teilkontaktverfahren generierte 200 μm breite Gellinie verbindet die Elektroden und fungiert als Trennkanal, in wel-chen kontaktfrei 500 pL der zu untersuchenden Probe dosiert werden. Um Verdunstungseffekte zu unterbinden wird das Gel bis zum Taupunkt gekühlt und mit Mineralöl überschichtet. Durch das Anlegen eines elektrischen Feldes an den Elektroden für 80 s konnte die Trennung der DNA-Fragmente (56 bp-Cy5 und 112 bp-Cy5, 10 μM) erfolgreich gezeigt werden.
• A. Gross, R. Zengerle, P. Koltay
  Exploitation and Commercialization within the EU FP7 Project PASCA
  2013 10th International Conference on Wearable Micro and Nano Technologies for Personalized Health. Tallin, 26.-28.06.2013 IOS Press, B. Blobel, pages: 167 - 178
• D. Liang, J. Zhang, T. G. Muniyogeshbabu, L. Tanguy, A. Ernst, P. Koltay, R. Zengerle
  Novel automated multi-principle volume calibration system for non-contact micro and nano liter liquid handling devices
  2013 Society for Laboratory Automation & Screening (SLAS) 2013: 2nd annual Conference & Exhibition in Orlando, FL, USA, 12.01. – 16.01.2013
• L. Tanguy, L. Gutzweiler, P. Koltay, R. Zengerle, L. Riegger
  On-demand electrophoretic separation of DNA in written gel lines on planar substrates
  2013 Transducers 2013, Barcelona, Spain, 16. – 18.06.2013 , pages: 1223 - 1226
  » show abstract« hide abstract
  Abstract

  We report a new approach to perform on-demand electrophoretic separation of DNA. In contrast to standard chip-based capillary electrophoresis in micromachined glass chips, we apply a planar polyimide substrate, write 200 μm wide gel lines bridging two Pt-electrodes and inject 500 pl sample volumes in non-contact manner. The gel is covered with mineral oil to inhibit evaporation. Subsequently, an electrical field is applied for 80 s and the separation of the DNA molecules (56 bp-Cy5 and 112 bp-Cy5, 10 μM) is successfully demonstrated.
• L. Tanguy, S. Bammesberger, A. Ernst, R. Zengerle, P. Koltay
  Smart pressure driven and regulated dispenser for the nanoliter and microliter range
  2013 Society for Laboratory Automation & Screening (SLAS) 2013: 2nd annual Conference & Exhibition in Orlando, FL, USA, 12.01. – 16.01.2013
• A. Madjarov, W. Streule, B. Schaub, A. Ernst, R. Zengerle, P. Koltay
  Wireless Eight Channel Printhead for Non-Contact Nanoliter Droplet Ejection
  2013 European Lab Automation 2013 (ELA2013), Hamburg, 06. – 07.06.2013
  » show abstract« hide abstract
  Abstract

  The new developed system is based on a highly integrated actuator which implements an eight channel nanoliter dispenser. It is built at a footprint of a standard SBS well plate, thus can be placed on available deck-tray positions of existing liquid handling platforms to extend their volume range to the lower end. Considering the application of the presented dispensing device, completely new prospects for high-throughput-screening, miniaturized assays and other applications using standard liquid handling platforms arise. The droplet ejection method is based on the PipeJetTM-technology. This method uses a piezo-driven piston squeezing a disposable dispensing tube to eject free flying droplets. To make this technology ready for automated handling, novel dosage elements (PipeJet-Tip) were developed. These PipeJet-Tips are compatible to standard pipetting interfaces and are molded in polypropylene including the 650 µm dispensing tube and the reservoir. Therefore, a low cost disposable dispensing element is implemented enabling the ejection of single droplets with volumes down to 20 nl (CV < 5%). The new actuator is able to address eight individual dispensing channels to imprint custom droplet patterns. Rechargeable batteries as power supply and wireless communication housed inside the system enable the autonomous working principle of the dispensing module.

2012

• S. Bammesberger, A. Ernst, L. Tanguy, R. Zengerle, P. Koltay
  A calibration-free, disposable, non-contact reagent dosing cartridge for the sub-µl range
  2012 Microfluidic Handling Systems, MFHS 2012, Enschede, The Netherlands, 10.10. – 12.10.2012 , pages: 54 - 57
• S. Bammesberger, S. Kartmann, L. Tanguy, D. Liang, K. Mutschler, A. Ernst, P. Koltay, R. Zengerle
  A low-cost, normally closed, solenoid valve for non-contact dispensing in the sub-µL range
  2012 1st International Conference on Microfluidic Handling Systems, October 2012, Enschede, The Netherlands , pages: 156 - 159
• A. Madjarov, W. Streule, P. Prokopp, R. Zengerle, P. Koltay
  A novel technology for automated liquid handling with disposable tips for the sub microliter range
  2012 SLAS 2012, San Diego, USA, February 4-8, 2012
• J. Schoendube, D. Wright, A. Yusof, R. Zengerle, P. Koltay
  CellJet: Label-Free Cell Printing via Real-Time Impedance Flow Cytometry for Single Cell Analysis
  2012 MicroTAS 2012, Okinawa/Japan, 28.10. - 01.11.2012 , pages: 419 - 421
• L. Tanguy, D. Liang, R. Zengerle, P. Koltay
  Droplet generation at the critical Weber numbers
  2012 65th Annual Meeting of the American Physical Society Division of Fluid Dynamics, 2012, San Diego, California USA, 18th - 20th November 2012
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  Abstract

  The ejection of liquid droplets from a nozzle is highly important for physics of fluid. The Weber number describes how much kinetic energy is needed to overcome the surface tension and create a free-flying droplet. According to literature Weber numbers above 12 assure the creation and safe break up of a liquid droplet. However, even when this number goes down below 8, it is still possible to observe droplet break-up but with particular effects. We present here experimental results and CFD simulations for droplet break-up at low Weber number where the droplet is generated with negative kinetic energy. Such droplet generation is characterized by the droplet breaking up and then returning back into the nozzle. This is due to the fact that during the droplet formation the surface tension begins to slow down the flow velocity inside the droplet and then finally inverts the flow direction, while the droplet tail still breaks off from the nozzle. Thus after the break up the droplet momentum is oriented toward the nozzle. It is therefore possible to observe the droplet returning into the bulk fluid. High-speed images of this particular phenomenon are shown and simulation results are presented to illustrate the break up dynamics and the local velocities in the droplet.
• K. Mutschler, W. Kunert, R. Ingenpaß, K. E. Grund, L. Tanguy, A. Ernst, R. Zengerle, P. Koltay
  EndoMediskop: Trans-Endoscopic Microinjection for Flexible Endoscopy
  2012 BMT 2012 - Biomedical Technology Congress in Jena, Germany, 16.09. – 19.09.2012 Biomed Tech, volume: 57, supplement: 1, pages: 361 - 364
• N. Lass, L. Riegger, A. Ernst, R. Zengerle, P. Koltay
  Enhanced liquid metal micro droplet generation by pneumatic actuation based on the StarJet Method
  2012 1st International Conference on Microfluidic Handling Systems, October 2012, Enschede, The Netherlands , pages: 38 - 41
• D. Liang, J. Zhang, T. G. Muniyogeshbabu, S. Bammesberger, L. Tanguy, A. Ernst, P. Koltay, R.Zengerle
  Multi-principle droplet calibration technology
  2012 MicroTEC Südwest Clusterkonferenz 2012, Stuttgart, Germany, 14. - 15. May 2012
• A. Madjarov, W. Streule, P. Prokopp, A. Ernst, R. Zengerle, P. Koltay
  Nanoliter Dispensing on Pipetting Workstations by Disposable PipeJet-Tips
  2012 Actuator 2012, Bremen, Germany, June 18-20 , pages: 430 - 433
• D. Liang, J. Zhang, L. Tanguy, A. Ernst, P. Koltay, R. Zengerle
  Nanoliter droplet characterization using vibrating crystal sensor with surface-attachedpolymer hydrogel coating
  2012 Eurosensors XXVI, Krakow/Poland, 09. - 12. September 2012 Procedia Engineering, volume: 47, pages: 1017 - 1020
• J. Schöndube, F. Stumpf, A. Gross, R. Zengerle, G. Roth, P. Koltay
  Non-Contact Single Cell Printing For Single Cell Real-time PCR
  2012 EMBL Conference Microfluidics 2012, Heidelberg, Germany, July 25-27 , page: p185
• P. Koltay
  Non-contact micro dispensing technologies for science and industry
  2012 Actuator 2012, Messe Bremen, Germany, June 18 - 20, 2012
• D. Liang, L. Tanguy, A. Ernst, R. Zengerle, P. Koltay
  Novel gravimetric calibration method for nanoliter liquid handling devices
  2012 1st International Conference on Microfluidic Handling Systems, October 2012, Enschede, The Netherlands , pages: 144 - 147
• D. Liang, T.G. Muniyogeshbabu, L. Tanguy, A. Ernst, R. Zengerle, P. Koltay
  Online liquid calibration technologies
  2012 1st International Conference on Microfluidic Handling Systems, October 2012, Enschede, The Netherlands , pages: 95 - 98
• J. Schöndube, A. Yusof, D. Wright, K. Kalkandjiev, R. Zengerle, P. Koltay
  Picoliter Droplet Dispenser with Integrated Impedance Detector for Single-cell Printing
  2012 Actuator 2012, Bremen, Germany, June 18-20 , pages: 418 - 421
• L. Tanguy, A. Ernst, S. Bammesberger, R. Zengerle, P. Koltay
  Pressure driven and regulated dispenser for the microliter range
  2012 Microfluidic Handling Systems, MFHS 2012, Enschede, The Netherlands, 10.10. – 12.10.2012 , pages: 50 - 53
• A. Yusof, K. Kankandjiev, J. Schöndube, R. Zengerle, P. Koltay
  Wafer Level Fabrication of an Integrated Microdispenser with Electrical Impedance Detection for Single-cell Printing
  2012 Proc. Of Smart Systems Integration, Zürich, Switzerland, March 21-22, 2012 , volume: paper 99, page: 4pp

2011

• N. Lass, A. Tropmann, L. Riegger, R. Zengerle, P. Koltay
  3D Rapid-Prototyping durch Drucken von flüssigem Metall unter Verwendung der StarJet Technologie
  2011 Mikrosystemtechnik-Kongress, Darmstadt, Deutschland, October 10-12 , pages: 193 - 196
  » show abstract« hide abstract
  Abstract

  In dieser Arbeit präsentieren wir einen neuen Ansatz für das direkte 3D-Prototyping von Metallstrukturen basierend auf der StarJet Technologie [1]. Im Gegensatz zu dem früheren Funktionsmuster (V0) verfügt die neue Version des Druckkopfs (V1) über hitzebeständigere Komponenten, die es erlaubt den Dispenser bei Temperaturen bis Tmax = 500°C zu betreiben (früher Tmax =_250°C). Dies ermöglicht das Dispensieren einzelner Tropfen aus Metall wie z.B. ZAMAK (Schmelztemperatur Tmelt = 450°C). Gleichzeitig wurde das Design und der Herstellungsprozess der sternförmigen Düsenchips optimiert. Die maximale Dosierfrequenz konnte somit um einen Faktor 10 auf fmax_=_4_kHz erhöht werden. Darüberhinaus konnte die Abweichung der Tropfenflugbahn von der Symetrieachse des Düsenchips auf unter deg_=_0,28° minimiert werden. In diesem Artikel berichten wir über die Ergebnisse der ersten experimentellen Versuche und präsentieren verschiedene 3D Metallstrukturen die damit gedruckt wurden.
• A. Gross, J. Schöndube, S. Rubenwolf, A. Yusof, G. Roth, R. Zengerle, P. Koltay
  Automatic Single Cell Printing for Tissue Engineering and Stem Cell Research
  2011 45. Deutschen Gesellschaft für Biomedizinische Technik (DGBMT), September 27-30, Freiburg
  » show abstract« hide abstract
  Abstract

  We present a novel method for automatic non-contact printing living single cells currently being developed within the PASCA project (www.pasca.eu). A microfluidic dispenser [1] with optical feedback prints single cells confined in free flying droplets of only hundreds of picoliter volume onto arbitrary substrates. Single yeast, cancer (HeLa) and stem cells (fibroblasts, keratinocytes) have been successfully printed with this method at viabilities of up to 95 %. Apart from applications in research and diagnostics the technology can also be used for tissue engineering. To show the feasibility an extra cellular matrix comprised of collagen and alginate has been printed.
• J. Schöndube, A. Yusof, A. Gross, S. Rubenwolf, D. Liang, G. Roth, R. Zengerle, P. Koltay
  Automatisiertes Drucken einzelner Zellen mittels eines kontaktfreien Druckverfahrens im Picoliterbereich
  2011 Mikrosystemtechnik-Kongress, Darmstadt, Deutschland, October 10-12 , pages: 902 - 905
  » show abstract« hide abstract
  Abstract

  Wir präsentieren einen Einzelzellmanipulator (EZM) zum automatisierten Drucken und Sortieren von Zellen. Der EZM ist Teil eines Projekts zur Realisierung einer „Platform for Advanced Single Cell-Manipulation and Analysis“ (PASCA, www.pasca.eu). Zellen werden in einem mikrofluidischen Tropfenerzeuger (NanoJet-Chip, [1]) von einer Kamera erkannt und mit hohen Überlebensraten einzeln in Pikoliter großen Tropfen auf beliebige Substrate kontaktfrei gedruckt [2]. Im Rahmen dieser Arbeit wurden Hefe-Zellen, Krebszellen (HeLa-Zellen) und Stammzellen (Fibroblasten, Keratinozyten) gedruckt. Zusätzlich wurden Überlebensraten von bis zu 95% und Einzelzellraten von bis zu 84% experimentell bestimmt.
• K. Mutschler, A. Ernst, N. Paust, R. Zengerle, P. Koltay
  Capacitive detection of nanoliter droplets on the fly - investigation of electric field during droplet formation using CFD-simulation
  2011 16th International Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 5-9 June 2011, Beijing China , pages: 430 - 433
  » show abstract« hide abstract
  Abstract

  Recently we presented a capacitive droplet sensor that enables the characterization of volume and velocity of dispensed nanoliter liquid droplets on the fly in a contact free manner [1]. In this work we perform a multi-physics simulation study to understand the physical effects behind the sensor signal. We combine a two-phase fluid dynamics model for droplet generation and droplet flight with an electrostatic model for analyzing the electric field distribution inside an open plate capacitor while the droplet is passing through. Beside droplet volume and velocity, also droplet tear-off point as well as droplet oscillations are reflected in the electric field distribution. The characteristic negative dip of the transient sensor signal which was observed in experiments can be explained by capacitive coupling of the liquid column with the sensor and is correctly reflected by the model. The detected changes in charge on the sensor capacitor, are in the range of 2 – 28 fC and correspond to droplet volumes in the range of 5 nl < Vdrop < 100 nl. This is in good agreement with experimental findings and analytical approximations.
• S. Bammesberger, A. Ernst, D. Liang, S. Kartman, L. Tanguy, R. Zengerle, P. Koltay
  Characterization of Dispensing Technologies in the sub-µl range
  2011 MicroTEC Südwest Clusterkonferenz 2011, Karlsruhe, Germany, July 5 and 6, 2011:
• Stefanie Rubenwolf, Sonja Niekrawietz, Jonas Schöndube, André Gross, Azmi Yusof, Dong Liang, Peter Koltay, Roland Zengerle, Günter Roth
  Digitaler Druck einer Hydrogelmatrix für das Einbetten von Zellen in künstlichen Zellverbänden
  2011 Mikrosystemtechnik-Kongress, Darmstadt, Deutschland, October 10-12 , pages: 879 - 882
  » show abstract« hide abstract
  Abstract

  Rapid Prototyping Verfahren auf Basis der Tintenstrahl-Drucktechnologie sind vielversprechende Ansätze zur Erzeu-gung dreidimensionaler heterogener Zellverbände als Organmodelle. Mit Hilfe der PipeJet™-Technologie konnte eine mehrschichtige Costruktur aus Collagen und Alginat gedruckt werden, die als Hydrogelmatrix zum Einbetten von Zellkulturen geeignet ist. Die hierzu aufgebaute automatisierte Plattform erlaubt steriles Arbeiten für synchrones Drucken von Zellen und Hydrogelmatrix zu künstlichen Zellverbänden.
• Artur Tropmann, Nils Lass, Nils Paust, Christoph Ziegler, Roland Zengerle, Peter Koltay
  Erzeugung monodisperser Mikropartikel aus wässrigen Lösungen Monodisperse Microparticle Generation from Aqueous Solutions
  2011 Mikrosystemtechnik-Kongress, Darmstadt, Deutschland, October 10-12 , pages: 941 - 944
• D. Liang, A. Gross, J. Schöndube, S. Rubenwolf, A. Yusof, A. Ernst, R. Zengerle, G. Roth, P. Koltay
  Improved Machine Vision for Single Cell Printing
  2011 Mikrosystemtechnik-Kongress, Darmstadt, Deutschland, October 10-12 , pages: 891 - 894
  » show abstract« hide abstract
  Abstract

  We present an improved application of novel machine vision in single cell printing. Biological cells are optically im-aged inside a microfluidic dispenser chip by a monochrome smart camera with digital signal processor (DSP) for real-time processing. Coaxial illumination and parallel image acquisition make high speed cell selection possible. In our first experiment the maximal selection rate reached 125Hz, which is about 16 times faster than previous work [1]. The successful selection rate in the first experiment reaches 89%.
• J. Schöndube, A. Gross, S. Rubenwolf, S. Niekrawitz, P. Koltay, R. Zengerle, G. Roth
  Integrated Instrument for Printing Single Cells and Hydrogel Matrices for Future Tissue Engineering
  2011 NanoBioTech 2011, Montreux, Switzerland, November 14-16
• A. Ernst, R. Zengerle, P. Koltay
  Kontaktfreie quantitative Volumenbestimmung dispensierter Nanolitertropfen mittels eines kapazitiven Tropfensensors
  2011 Mikrosystemtechnik-Kongress, Darmstadt, Deutschland, October 10-12 , pages: 799 - 802
• Kiril Kalkandjiev, Ludwig Gutzweiler, Roland Zengerle, Peter Koltay
  Kostengünstige Fertigung großflächiger Druckköpfe durch Lamination von Trockenlacken auf vorstrukturierte Polymersubstrate
  2011 Mikrosystemtechnik-Kongress, Darmstadt, Deutschland, October 10-12 , pages: 883 - 886
  » show abstract« hide abstract
  Abstract

  In diesem Beitrag wird ein mikrofluidischer Kunststoff-Druckkopf als Alternative zu seinem etablierten Silizium/Glas-Äquivalent beschrieben. Der Druckkopf wurde durch die Kombination spanabhebender und lithographischer Verfahren hergestellt, welche für großflächige Bauteile mit mikrostrukturierten Durchgangsöffnungen besonders geeignet sind. Er beinhaltet 24 Düsen mit einem Durchmesser von 50 μm, die über mikrofluidische Kanäle mit jeweils einem Reservoir verbunden sind. Alle Mikrostrukturen wurden im Trockenlack TMMF strukturiert, das Druckkopfinterface besteht aus PMMA. Die verhältnismäßig große Grundfläche von 36 x 18 mm wird durch die standardisierte Anordnung der Reser-voire im Rastermaß der 384er Mikrotiterplatte und die notwendige Interaktion mit einem externen Piezoaktor vorgege-ben. Grundlegende Anforderungen wie die leckagefreie Verbindung zwischen den Reservoiren und den entsprechenden Düsen, die Realisierung eines gedeckelten mikrofluidischen Kanalsystems sowie die Durchgängigkeit und Homogenität der Düsen wurden reproduzierbar umgesetzt. Durch entsprechende Nachbehandlung wurden die mikrofluidischen Strukturen mit entsprechenden Oberflächenfunktionalitäten versehen, die eine kapillare Befüllung der Düsen und den parallelen Ausstoß von Einzeltropfen nach dem etablierten TopSpot® Verfahren ermöglichen.
• A. Tropmann, N. Lass, N. Paust, C. Ziegler, R. Zengerle, P. Koltay
  Monodisperse microparticle generation from aqueous solutions
  2011 Proc. of 16th International Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 5-9 June 2011, Beijing China , pages: 1460 - 1463
  » show abstract« hide abstract
  Abstract

  We present a new approach for the generation of monodispersed droplets and tailor-made microparticles of complex liquids from a star-shaped nozzle that precisely defines the dispensed droplet sizes. From two aqueous polymer solutions: 30w% Polyvinylpyrrolidone (PVP) (viscosity η ≈ 105 mPas) and 40w% PVP (η ≈ 490 mPas) droplet volumes of 3.9 nl and 3.2 nl respectively were generated employing a star-shaped silicon nozzle with a diameter of 183 μm. From 1w% Mannitol (η ≈ 1 mPas) droplets (100 pl) and particles (22 μm) were generated from a 59 μm nozzle. These results show for the first time particle generation with the StarJet method that could be applicable for the generation of monodispersed powders for use in healthcare, food and home care products.
• N. Lass, A. Tropmann, A. Ernst, R. Zengerle, P. Koltay
  Rapid prototyping of 3D microstructures by direct printing of liquid metal at temperatures up to 500°C using the starjet technology
  2011 16th International Solid-State Sensors, Actuators and Microsystems Conference (TRANSDUCERS), 5-9 June 2011, Beijing China , pages: 1452 - 1455
  » show abstract« hide abstract
  Abstract

  We present a novel approach for 3D-prototyping of porous metal structures by direct non-contact liquid metal printing, based on the StarJet technology [1]. In contrast to our previous work, the presented droplet generator features an improved nozzle chip design and actuator housing that allows operation at temperatures up to Tmax = 500°C (formerly Tmax = 250°C). This enables the ejection of single droplets of metals with higher melting points like for example magnesium or zinc alloys like ZAMAK. The droplet generation frequency could be increased by a factor of 10 to fmax = 4 kHz. Furthermore, deviations of the droplet trajectory from the symmetry axis of the nozzle are reduced to Δdeg = 0.28° by the new design. This paper reports on experimental results obtained with the improved device and presents 3D metal structures with various porosities.
• Azmi Yusof, Roland Zengerle, Peter Koltay
  TMMF dry film resist as masking layer in deep etching of Pyrex-glass for microfluidic chip fabrication
  2011 Proc. Eurosensors XXV, September 4-7, Athens, Greece, Volume 25 , pages: 827 - 830
  » show abstract« hide abstract
  Abstract

  We present the application of dry film resist (TMMF) as new masking technology to process glass wafers using standard wet etching. The considered microfluidic chip features patterned metal electrodes for impedance sensing and hydraulic access holes fabricated on a Pyrex wafer. Therefore, deep etching of through holes, while protecting the deposited metal structures on the Pyrex glass wafer, is required. To achieve this, amorphous silicon (a-Si) was used as masking layer on one side and unexposed TMMF dry film resist was used as mask on the other side of the wafer. The a-Si and TMMF are excellent masking layers in deep-wet etching for Pyrex wafers with etch duration more than 1 hour in 49% hydrofluoric (HF) acid.
• A. Yusof, R. Zengerle, P. Koltay
  Towards a microfluidic dispenser chip for printing of single cells
  2011 24th IEEE International Conference on Micro Electro Mechanical Systems.IEEE MEMS 2011 Conference - January 23 - 27, 2011 - Cancun, MEXICO
• K. Kalkandjiev, A. Yusof, J. Schöndube, R. Zengerle, P. Koltay
  Wafer-Level Fabrication of Microfluidic Sensors for Impedance Spectroscopy with Integrated Opposing Electrodes
  2011 Proc. Eurosensors XXV, September 4-7, Athens, Greece , page: ID 1202
  » show abstract« hide abstract
  Abstract

  We present the fabrication of microfluidic sensors with opposing electrodes for impedance spectroscopy. The sensors are fabricated by sandwiching TMMF dry photopolymer between two substrates, each with one electrode patterned on its fluid-contacting side. In this configuration, TMMF becomes a permanent part of the microfluidic device and has a twofold purpose: it defines the microfluidic network, and it is used as a patterned adhesive for low-temperature full-wafer silicon to glass bonding. According to the requirements of single cell dispensing, the opposing electrodes are placed between a hydrodynamic flow focusing for aligning the cells in a single file and a dispensing nozzle for printing the detected cells.

2010

• A. Yusof, L. Riegger, N. Paust, A. Ernst, R. Zengerle, P. Koltay
  A Non-Invasive Single Cell Dispensing Approach for 2-Dimensional Micro-Patterning
  2010 Actuator 2010, Bremen, Germany, 14.-16. June , pages: 1033 - 1036
  » show abstract« hide abstract
  Abstract

  We present a computer vision-based approach for detection of micro-beads and cells combined with a noncontact liquid dispensing system to pattern single polystyrene-beads and yeast cells in a 2-dimensional array. A so called NanoJet dispenser for dispensing liquid borne particles features the average droplet volume of 150pL to 950pL and a reproducibility of (CV) < 3%. The computer vision set-up consists of a CCD camera coupled with a magnifying lens, which was employed to detect the micro-beads close to the dispenser’s orifice prior to dispensing. A real-time sequential image analysis was carried out by using a simple temporal differencing detection algorithm to identify single cells or particles in the proximity of the orifice that would be ejected with the subsequent dispense. Using this process arrays of polystyrene-beads and yeast cells were deposited onto glass slides attached to a programmable motorized stage. The overall deposition efficiency obtained was 70% with 58% of the spots contained single polystyrene-beads or cell respectively. Keywords: single-cell, computer vision based detection, non-contact droplet dispensing, cell printing
• Kiril Kalkandjiev, Ludwig Gutzweiler, Mathias Welsche, Roland Zengerle, Peter Koltay
  A novel approach for the fabrication of all-polymer microfluidic devices
  2010 roc. of IEEE-MEMS, Hong-Kong, China, January 24-28 , pages: 1079 - 1082
  » show abstract« hide abstract
  Abstract

  This paper describes a process sequence for the fabrication of all-polymer microfluidic chips based on the multilayer lamination of TMMF dry resist (TOK, Japan) on a pre-patterned PMMA substrate. The sequence provides a simple way to meet major microfluidic requirements like the fabrication of embedded microchannels, nozzles and intercon-necting vias as well as their accurate integration into a chip-interface without additional materials and bonding procedures. We demonstrate the appli-cability of the sequence by manufacturing and test-ing a 24-channel TopSpot printhead. Additionally, non-cytotoxicity of TMMF was confirmed in cell culture experiments and different methods for sur¬face modification were investigated.
• Kiril Kalkandjiev, Roland Zengerle, Peter Koltay
  Hybrid fabrication of microfluidic chips based on COC, silicon and TMMT dry resist
  2010 Proc. of IEEE-MEMS, Hong-Kong, China, January 24-28 , pages: 400 - 403
  » show abstract« hide abstract
  Abstract

  We describe the hybrid fabrication of silicon-plastic microfluidic chips based on machining of Cyclic Olefin Copolymer (COC), standard silicon process-ing and TMMF lithography. The combination of different processes enables an individual material selection leading to significant reduction of the manufacturing costs. We demonstrate the potential of the hybrid technology by manufacturing and testing a 24-channel TopSpot dispenser [1] which consists of an intermediate silicon layer, a COC interface and a TMMF sealing lid. Characterization studies show that TMMF lamination is ideally suited for the sealing of silicon microchannels showing numerous advantages over adhesive-based approaches, thermal and anodic bonding.

2009

• N. Paust, S. Krumbholz, S. Munt, C. Müller, R. Zengerle, C. Ziegler, P. Koltay
  Design of a passive and portable DMFC operating in all orientations
  2009 Proc. IEEE-MEMS; 25 – 29 January 2009, Sorrento, Italy , pages: 1091 - 1094
  » show abstract« hide abstract
  Abstract

  A microfluidic layout concept for passive and portable Direct Methanol fuel Cells (DMFCs) is presented. We proofed this concept by developing a DMFC that continuously runs for 40 hours in all orientations without the need for any active components such as pumps or valves. In contrast to our previous work [1], the system now is truly portable. In any orientation of the DMFC, a bubble driven self regulating supply mechanism safely removes carbon dioxide and transports at least 3.5 times more methanol to the anode than critically needed to sustain DMFC operation. On the cathode, diffusive oxygen supply and the transport of the reaction product water along a capillary gradient out of the DMFC ensures a stable performance. Compared to our previous work [1], the power output was increased by a factor of 2.5 and reached p = 5.5 mW cm-2. A stable power output for 40 hours of p = 4 mW cm-2 was achieved for the preferred vertical position with bubbles moving against buoyancy forces. In the most challenging horizontal position with the anode facing downwards, a power output of at least p = 3.1 mW cm-2 was reached for the same period of time.
• Kiril Kalkandjiev, Roland Zengerle, Peter Koltay
  Fertigung von Hybriddruckköpfen aus Silizium und Kunststoff
  2009 Tagungsband Mikrosystemtechnik-Kongress, Berlin, 12.-14. Oktober , page: P7.1
  » show abstract« hide abstract
  Abstract

  Wir präsentieren einen Ansatz für die hybride Fertigung von mikrofluidischen Produkten durch die Integration von Sili-zium und Kunststoff. Der Ansatz ist besonders für die kostengünstige Herstellung von Produkten geeignet, in welchen hochpräzise Siliziumstrukturen mit anderen, großflächigen Komponenten verbunden werden sollen. Wir zeigen das Po-tential dieser Technik durch die Fertigung eines 24-kanaligen Dispensers für die Herstellung von Microarrays mittels der TopSpot Technologie. Der Hybriddruckkopf ist dreilagig aufgebaut und besteht aus einer Reservoirplatte aus Cyclo-Olefin-Copolymer (COC), einem Siliziumchip mit mikrofluidischen Strukturen und einer Deckelschicht aus Epoxy-basiertem Trockenresist (TMMF). Diese Materialkombination führt zu einer Reduzierung der Herstellungskosten um mehr als 50 % bei gleichbleibender Performance im Vergleich zu den kommerziell verfügbaren Dispenser in Silizium-Glas-Technik [1]. Der hybride Fertigungsansatz kann somit als eine vorteilhafte Alternative und Ergänzung zu den klas-sischen Materialien und Prozessen der Mikrosystemtechnik angesehen werden.
• Ernst A, Streule W, Zengerle R, Koltay P
  Quantitative volume determination of dispensed nanoliter droplets on the fly
  2009 Proc. Transducers, Denver, USA , pages: 1750 - 1753
  » show abstract« hide abstract
  Abstract

  In this paper we present a sensor for non-contact monitoring of dispensed micro-droplets on the fly. In extension to our previous work [1], the sensor now allows for a direct, quantitative volume determination of single liquid droplets in the volume range from 20 to 100 nl. The improved electronic transducer enables to measure the droplet volume with an accuracy of ΔV ± 3 nl. The sensor signal provides a variety of information about the monitored droplet like for examples droplet velocity. This paper considers in particular the influence of the droplet velocity on the volume measurement. It turned out that the velocity effect can be fully compensated, if the signals are interpreted correctly.
• T. Metz, G. Birkle, R. Zengerle, P. Koltay
  StarJet: Pneumatic dispensing of nano- to picoliter droplets of liquid metal
  2009 Proc. IEEE-MEMS; 25 – 29 January 2009, Sorrento, Italy , pages: 43 - 46
  » show abstract« hide abstract
  Abstract

  In this work we present a novel, simple and robust, pneumatically actuated dispenser for nano- to picoliter sized droplets of liquid metals. The so called StarJet dispenser utilizes a star-shaped nozzle geometry that stabilizes plugs of liquid in the centre of the nozzle by capillary force. This minimizes the wall contact of the liquid plug and reduces contact line friction. Individual droplets of liquid metal can be pneumatically generated by interplay of the sheathing gas flow in the outer grooves of the nozzle and the liquid metal. The working principle was first discovered and studied by Computational Fluid Dynamic (CFD) simulations. For experimental validation silicon chips with the star-shaped geometry were fabricated by Deep Reactive Ion Etching (DRIE) and assembled into a printhead. With different nozzle chips volumes between 120 pl and 3.6 nl could be generated at natural frequencies of 90 Hz and 400 Hz. The StarJet can either be operated as drop on demand or as continuous droplet dispenser. We printed columns of metal with 0,5 to 1,0 mm width and 40 mm height (aspect ratio >40) to demonstrate the directional stability of the ejection.
• Tobias Metz, Gerhard Birkle, Christoph Ziegler, Roland Zengerle, Peter Koltay
  StarJet: Pneumatische Erzeugung von Nano- bis Picoliter Tropfen flüssigen Lötzinns in einer sternförmigen Düse
  2009 Tagungsband Mikrosystemtechnik-Kongress, Berlin, 12.-14. Oktober , page: P 81
  » show abstract« hide abstract
  Abstract

  In dieser Arbeit zeigen wir einen einfachen und robusten, pneumatisch aktuierten drop-on-demand Dispensierer (StarJet) zur Generierung von Tropfen flüssigen Lötzinns im Nano- bis Pikoliterbereich. Das System basiert auf einer sternförmigen Düsengeometrie, die das flüssige Metall im Zentrum der Düse durch Kapillarkräfte stabilisiert. Dabei ist der Wandkontakt und damit die Wandreibung zwischen dem Flüssigkeitstropfen und der Düse minimiert. Die sternförmige Geometrie ermöglicht in einem selbstorganisierten Wechselspiel mit der Strömung des Schutzgases (N2) in den Fingern des Sternprofils einen pneumatisch erzeugten Tropfenabriss. Dabei stellt sich bei konstanter Aktuation eine natürliche Eigenfrequenz der Tropfengenerierung ein. In Experimenten wurden Tropfen flüssigen Lötzinns, die beispielsweise für das Flip-Chip Bonding genutzt werden können, mit Volumen von 450 pl und 7.2 nl bei natürlichen Frequenzen zwischen 30 und 400 Hz erzeugt. Einzeltropfen konnten durch Aktuationszeiten im Bereich der Eigenfrequenz generiert werden. Durch kontinuierliche Aktuation konnten Säulen flüssigen Lötzinns mit einer Höhe bis zu 30mm bei einer Breite von 500µm erzeugt werden.
• Riegger L, Mielnik MM, Mark D, Streule W, Clad M, Zengerle R, Koltay P
  Teflon-carbon black as new material for the hydrophobic patterning of polymer labs-on-a-chip
  2009 Proc. Transducers '09, Denver, USA , pages: 2026 - 2029
  » show abstract« hide abstract
  Abstract

  We provide a new method for the selective surfacepatterning of microfluidic chips with hydrophobicfluoropolymers which is demonstrated by the fabricationof hydrophobic valves. It enables efficient optical qualitycontrol for the surface patterning thus permitting the lowcostproduction of highly reproducible hydrophobicvalves. Specifically, a fluoropolymer-solvent-dye solutionbased on carbon black (CB) is presented which createssuperhydrophobic surfaces (contact angle = 157.9°) onchips made from cyclic olefin copolymer (COC). It furtherprovides good visibility for the quality control (QC) inpolymer labs-on-a-chip and increases the burst pressure ofhydrophobic valves. Finally, an application which aims forthe amplification of mRNA on-chip and relies on thedefined flow control by hydrophobic valves is presented.Here, the QC in combination with the Teflon-CB coatingimproves the average standard deviation of the burstpressures from 14.5% down to 6.1 % compared to solelyTeflon-coated valves

2008

• J. Steigert, M. Strasser, O. Brett, N. Wangler, W. Streule, P. Koltay, M. Daub, R. Zengerle
  A modular dispensing system for leakage-free picoliter droplet release in liquid environments
  2008 Proceedings of The 12th International Conference on Miniaturized Systems for Chemistry and Life Sciences (µTAS 2008) , pages: 360 - 362
  » show abstract« hide abstract
  Abstract

  We present a new tool that can be positioned accurately next to any individual cell for the precisely controlled transfer of individual picoliter (pL) droplets in the range of 150-950 pL (CV < 3.5%) in liquid environment while avoiding any leakage. This is achieved by a low-cost, disposable and biocompatible cap that is placed on top of any pL-dispenser and generates a phase-gap between dispensing agent and target liquid when the dispenser is dipped into the latter thus avoiding diffusive transport. We developed two different working modes: (i) the standard mode enables an instant injection (<< 1 ms) of the droplet into the liquid environment and (ii) the focus mode further increases the spatial resolution from 100 μm to 50 μm. For the phase-gap we have proven an excellent long-term stability of more than 30 hours against capillary priming and a maximum volume ejection rate of up to 137 nL/s without flooding.
• Peter Koltay, Roland Zengerle, Christoph Ziegler
  Coarse grid modelling of capillary driven two-phase flow in direct methanol fuel cells
  2008 Proceedings of the 1st European Conference on Microfluidics (Microfluidics), Bologna, December 10-12
• S. Lutz, P. Lang, L. Riegger, W. Streule, M. Daub, P. Koltay, F. von Stetten, R. Zengerle, J. Ducrée
  Contact-Free Dispensing of Living Cells in Nanoliter Droplets
  2008 Actuator 2008 / Bremen Messe Bremen
  » show abstract« hide abstract
  Abstract

  We present a novel method for automated dispensing of living cells in nanoliter range droplets using a disposable pipette tip combined with an elastic polymer tube. After introduction of an unmetered suspension of cells into a reservoir connected to the pipette tip, a tuneable volume of 10 - 80 nL of cells suspension is issued in a non-contact procedure. Droplet ejection is enabled by a piezostack driven piston squeezing the tube at a defined position. We achieve a reproducibility of the printed cell culture medium volumes better than 5% and survival rate of the cells of 97% directly after dispensing. In addition we demonstrated good culturability and cell differentiation in order to consider potential long term effects of the dispensing process that could harness the cells. Keywords: nanoliter dispensing, cells, piezo actuation
• Paust, Nils, Litterst, Christian, Metz, Tobias, Zengerle, Roland, Koltay, Peter
  Fully passive degassing and fuel supply in direct methanol fuel cells
  2008 Proc. IEEE-MEMS 2008, Tucson, USA , pages: 34 - 37
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  Abstract

  In this paper a micro direct methanol fuel cell (μDMFC) is presented, which is operated in a completely passive way, i.e. the cell does not require an external pump for fuel supply. The surface energy of deformed CO2 bubbles, generated as a reaction product during DMFC operation, is employed to supply methanol to the anode. In contrast to a digital valve based approach presented earlier by Meng et. al. [1], a tapered channel is applied to achieve a pumping mechanism. This way the pump rates can be adapted to the requirements of a specific cell. The presented study reveals that this concept is able to maintain the supply for all typical DMFC operation conditions. Experimental results are presented that demonstrate the continuous operation of a passive μDMFC for more than 15 hours.
• Andreas Ernst, Wolfgang Streule, Roland Zengerle, Peter Koltay
  Kontaktfreie Detektion von frei fliegenden Nanoliter-Tropfen
  2008 Tagungsband Sensoren und Messsysteme 2008, 14. Fachtagung Ludwigsburg, 11.-12. März, ISBN 978-3-18-092011-5 VDI Wissensforum GmbH, pages: 881 - 889
  » show abstract« hide abstract
  Abstract

  Im Folgenden wird ein Sensor zur kontaktfreien Detektion von frei fliegenden Tropfen mit Durchmessern im Bereich von 200 – 500 µm vorgestellt. Der Signalgeber basiert auf einem kapazitiven Prinzip und kann problemlos in die Flugbahn des dispensierten Mediums eingebracht werden. Durch die kleine Bauform kann dies auch bei kleinen Abständen (~ 3 mm) der Dispenserdüse zum Substrat umgesetzt werden. Ein Hauptaugenmerk dieses Sensors ist seine kontaktfreie Arbeitsweise, durch welche die Kontamination der dispensierten Flüssigkeit und somit der Verlust einzelner Tropfen vermieden wird. Der Sensor ist in konventioneller Lieterplattentechnologie (engl. PCB-Technologie ) hergestellt und kann in seiner momentanen Form zur direkten Prozesskontrolle eingesetzt werden. Durch Vergleichen der aktuellen Sensorsignale mit spezifischen „Fingerprint“ Signalen der dosierten Flüssigkeiten können Volumenänderungen und Geschwindigkeitsabweichungen im Dosierprozess festgestellt werden.
• T. Metz, L. Riegger, C. Ziegler, R. Zengerle, P. Koltay
  Pressure characteristics modelling for rapid design of capillary microfluidic systems
  2008 Proceedings of The 12th International Conference on Miniaturized Systems for Chemistry and Life Sciences (µTAS 2008) , pages: 1354 - 1356
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  Abstract

  This work presents a novel compact modelling approach for microfluidic systems which rely on the control of plugs or gas bubbles by capillary forces. A generic network model is derived to calculate the capillary pressure of such systems. By applying the model the behaviour of liquid plugs or gas bubbles can be analyzed. This is simply performed by shifting “virtual” volumes along the volume scale at the xaxis of the graph and deducing pressure drops. Pressure characteristics are calculated for two systems and the predicted behaviour is compared to experiments. The approach is simple but efficient and enables a rapid design of capillary micro fluidics for μTAS.

2007

• Paust,N., Litterst,C., Metz,T., Eck,M., Zengerle,R., Koltay,P.
  Capillary driven fuel supply in direct methanol fuel cells with double tapered t-shaped channel flow fields
  2007 Proceedings of PowerMEMS, Freiburg, Germany, 28-29 November 2007 , pages: 185 - 188
• Schuhmacher,D., Scheithauer,H., Alavi,M., Niekrawietz,R., de Heij,B., Zengerle,R., Koltay,P.
  Erzeugung von Mikrotropfen aus flüssigem Lötzinn mittels einer hochparallelen und kontaktlosen Drucktechnik
  2007 MikroSystemTechnik Kongress, Dresden, Germany, 15.-12. Oktober 2007 Proceedings, VDE, pages: 655 - 658
• Paust,N., Litterst,C., Metz,T., Zengerle,R., Koltay,P.
  Gasblasengetriebene Pumpe für Mikroreaktoren
  2007 MikroSystemTechnik Kongress, Dresden, Germany, 15.-12. Oktober 2007 Proceedings, VDE, pages: 481 - 484
• Metz,T., Paust,N., Müller,C., Zengerle,R., Koltay,P.
  Micro structured flow field for passive water management in miniaturized PEM fuel cells
  2007 MEMS 2007, Kobe, Japan, 21-25 January 2007 Proceedings of the 20th IEEE International Conference on Micro Electro Mechanical Systems, MEMS
• Metz,T., Paust,N., Müller,C., Zengerle,R., Koltay,P.
  Mikrostrukturierte Gasverteilerstrukturen für den passiven Wasseraustrag aus PEM Brennstoffzellen
  2007 MikroSystemTechnik Kongress, Dresden, Germany, 15.-12. Oktober 2007 Proceedings, VDE, pages: 913 - 916
• Steinert,C.P., Mueller-Dieckmann,J., Weiss,M., Roessle,M., Zengerle,R., Koltay,P.
  Miniaturized and Highly Parallel Protein Crystallization on a Microfluidic Disc
  2007 MEMS 2007, Kobe, Japan, 21-25 January 2007 , pages: 561 - 564
• Ernst,A., Streule,W., Koltay,P., Zengerle,R.
  Non-contact detection of free flying nanoliter droplets
  2007 11th International Conference on Solid State Sensors, Actuators and Microsystems, Lyon, France, June 10-14, 2007 , pages: 751 - 754
• Koltay,P., Zengerle,R.
  Non-contact nanoliter & picoliter liquid dispensing
  2007 11th International Conference on Solid State Sensors, Actuators and Microsystems, Lyon, France, June 10-14, 2007 , pages: 125 - 129
• Wangler,N., Zengerle,R., Koltay,P.
  Optische Qualitätskontrolle für hoch parallelen TopSpot® Microarray Printer
  2007 MikroSystemTechnik Kongress, Dresden, Germany, 15.-12. Oktober 2007 Proceedings, VDE, pages: 869 - 872
• Metz,T., Kerzenmacher,S., Paust,N., Mueller,C., Zengerle,R., Koltay,P.
  Passive water management system for pem fuelcells using microstructures
  2007 Proceedings of PowerMEMS 2007, Freiburg, Germany , pages: 177 - 180
• Riegger,L., Streule,W., Henze,C., Zengerle,R., Koltay,P.
  PipeJet P4.5 - Kostengünstiger Kompakt-Nanoliter-Dosierer im Mikrotiterplattenformat
  2007 MikroSystemTechnik Kongress, Dresden, Germany, 15.-12. Oktober 2007 Proceedings, VDE, pages: 925 - 926
• Streule,W., Hiltmann,K., Arnold,M., Kück,H, Zengerle,R., Koltay,P.
  PipeJet-Tip - Nanoliter-Dispenser mit kostengünstigen Dosierelementen und eingebautem Reservoir
  2007 MikroSystemTechnik Kongress, Dresden, Germany, 15.-12. Oktober 2007 Proceedings, VDE, pages: 943 - 946
• Schuhmacher,D., Niekrawietz,R., Scheithauer,H., de Heij,B., Alavi,M., Zengerle,R., Koltay,P.
  Production of solder microdroplets using a highly parallel and contact-free printing method
  2007 MEMS 2007, Kobe, Japan, 21-25 January 2007 , pages: 357 - 360
• Metz,T., Streule,W., Zengerle,R., Koltay,P.
  Startube: A novel tube design for bubble tolerant interconnection in fluidic systems
  2007 MicroTAS 2007, Paris, France, 07.10. - 11.10.2007 , pages: 1149 - 1151

2006

• Hu M, Lindemann T, Goettsche T, Kohnle J, Zengerle R, Koltay P
  Discrete chemical release from a microfluidic chip
  2006 Proc. IEEE-MEMS 2006; Istanbul, Turkey, pages: 28 - 31
• Steger R, Mehne C, Wangler N, Heckele M, Zengerle R, Koltay P
  Drop In Drop Nanoliter Kinase Assay Made With Hot Embossed Disposable Multi Channel Dispenser
  2006 Proc. of the 10th International Conference on Miniaturized Systems for Chemistry and Life Sciences (Microtas 2006), Tokyo, Japan, pages: 999 - 1001
• Litterst C, Eccarius S, Hebling C, Zengerle R, Koltay P
  Novel Structure for Passive CO2 Degassing in µDMFC
  2006 Proc. IEEE-MEMS 2006; Istanbul, Turkey, pages: 102 - 105

2005

• Zibek S, Goettsche T, Hu M, Kentsch J, Kohnle J, Koltay P, Martin D, Zengerle R, Stett A, Stelzle M
  Artificial Synapse – Nanofluidiksystem zur lokalen Substanzapplikation mittels nanoporöser Membran mit schaltbarer Permeabilität
  2005 Freiburg, Germany Proceedings Mikrosystemtechnik-Kongress 2005, VDI/VDE/IT
• Lindemann T, Ashauer H, Goettsche T, Sandmaier H, Yu Y, Peters R, Sassano D, Bellone A, Zengerle R, Koltay P
  Bubble Jet Printhead with Integrated Polyimide Nozzle Plate
  2005 Miami Beach, Florida, USA Proceedings of 18th IEEE International Conference on Micro Electro Mechanical Systems, MEMS, volume: 1, issue: 1, pages: 560 - 563
• Cupelli C, Koltay P, Santer M, Zengerle R
  Compact Model of a Laminar Micro Mixer
  2005 Technical Proceedings of the 2005 Nanotechnology Conference and Trade Show, pages: 724 - 727
• Goettsche T, Ruddy C, Heller U, Stehr M, Ashauer H, Lindemann T, Koltay P, Yu Y, Peters R, Soriani P, Bellone A
  Development of highly precise bonding procedures for structured polyimide films on silicon substrates
  2005 Karlsruhe, Germany Proc. 4M Conference
• Streule W, Storz M, Gracki S, Ashauer H, Zengerle R, Koltay P
  Kontaktfreie und medienunabhängige Volumenbestimmung in Nanoliter Dispensern
  2005 Freiburg, Germany Proc. Mikrosystemtechnik-Kongress 2005, VDI-VDE-IT
• Koltay P, Steger R, Streule W, Zengerle R
  Mikrodosiertechnik für die Biotechnologie und industrielle Anwendungen
  2005 Freiburg, Germany Proc. Mikrosystemtechnik-Kongress 2005, VDI-VDE-IT
• Koltay P, Steger R, Streule W, Zengerle R
  Nanoliter Liquid Handling enabled by Microsystem Technology
  2005 Lab Automation 2005; San Jose, CA, USA
  » show abstract« hide abstract
  Abstract

  In this paper we report on micro dispensing devices for precise and highly parallel liquid handling of nanoliter quantities. Two different microfluidic systems are presented: The so called Dispensing Well Plate (DWP) is a device similar to a standard micro well plate which is able to fill aliquots of about 50 nL contact-free into 384 and 1536 well plates. To do so the DWP-device comprises of 384 micromachined dispensing units, each consisting of a reservoir, a supply channel and a nozzle. The whole DWP can be actuated pneumatically by a simple external driving unit to provide 384 different liquids simultaneously to a well plate or any other substrate within a tenth of a second. Characterization experiments performed with water and DMSO prove a homogeneity and reproducibility of better 5%. The so called PipeJet dispenser is a novel single channel dispenser which consists merely of a simple polymer tube with a few hundred microns diameter. In contrast to syringe solenoid dispensers or similar the PipeJet does not require any valve which makes it extremely robust and insensitive to clogging. Single droplets can be ejected from the tube’s orifice by squeezing a certain section of the fluidic line with an external actuator with high dynamics. In this way droplets with volumes between 1.5 nL and 100 nL can be delivered contact-free. In particular the systems is able to cope with difficult liquids like protein solutions of high concentration, DMSO, methanol, ethanol and bead solutions with excellent CVs between 1% and 5%.
• Steger R, Streule W, Zengerle R, Koltay P
  Novel Disposable Devices for precise Nanoliter Liquid Handling
  2005 SBS 11th Annual Conference & ExhibitionDrug Discovery: From Targets to Candidates, September 11-15,
• Litterst C, Eccarius S, Hebling C, Zengerle R, Koltay P
  Novel Structure for Passive CO2 Degassing in µDMFC
  2005 Tokyo Proc. of PowerMEMS 2005, pages: 194 - 197
• Litterst C, Streule W, Koltay P, Zengerle R
  Simulation Toolkit for Micro-Fluidic Pumps using Lumped Models
  2005 Anaheim Technical Proceedings of the 2005 Nanotechnology Conference and Trade Show, pages: 736 - 739
• Eccarius S, Litterst C, Wolff A, Tranitz M, Koltay P, Agert C
  Systemaspekte in planaren Mikrobrennstoffzellensystemen
  2005 Freiburg, Germany Proc. of Mikrosystemtechnik-Kongress 2005
• Cupelli C, Koltay P, Zengerle R, Santer M
  Systembeschreibung und Modellierung von Mischprozessen
  2005 Freiburg, Germany Proc. Mikrosystemtechnik-Kongress 2005, VDI-VDE-IT
• Koltay P, Zengerle R
  The TopSpot - Microarrayer: An example for high priced micromachined components creating added value"; "
  2005 10th International Conference on the Commercialization of Micro and Nano Systems (COMS-05); Baden-Baden; Germany , pages: 364 - 367
• Steinert C, de Heij B, Koltay P, Sandmaier H, Zengerle R
  TopSpot Vario: New Method for Parallel Nanoliter Dosing by Direct Liquid Displacement
  2005 Freiburg, Germany Proc. Mikrosystemtechnik-Kongress 2005, VDI-VDE-IT
• Cupelli C, Koltay P, Ducrée J, Zengerle R, Santer M
  Towards a Modular Split & Recombine Micro Mixer
  2005 IMRET, Atlanta, USA Proc. 8th international Conference on Microreaction Technology (IMRET)

2004

• Steger R, Bohl B, Neurath A, Messner S, Sandmaier H, Zengerle R, Koltay P
  A Highly Parallel Nanoliter Dispensing SystemFabricated by High-Speed Micromilling of Polymers
  2004 Actuator, Bremen, Germany, 14-16 June Proc. ACTUATOR 2004, pages: 545 - 548
• Steger R, Bohl B, Zengerle R, Koltay P
  Dispensing Well Plate: A Highly Parallel Nanoliter Liquid Handling Device for HTS
  2004 3. – 6. May, Basel, Switzerland Proc 7th MIPTEC conference
• Steger R, Bohl B, Steinert C, Zengerle R, Koltay P
  Fixed Volume 384 channel NANOLITER DISPENSER for highly parallel and simultaneous liquid transfer into well plates
  2004 MicroTAS 2004, Malmö, Sweden, September 26-30 Proceedings of MicroTAS 2004, pages: 518 - 520
• Litterst C, Kohnle J, Ernst H, Messner S, Sandmaier H, Zengerle R, Koltay P
  Improved Gas Bubble Mobility in CHIC-Type Flow Channels
  2004 Actuator 2004, Bremen; Germany; 14-16 June Proc. ACTUATOR 2004, pages: 541 - 544
• Zengerle R, Ducrée J, Koltay P
  Microfluidics - An Enabling Technology for the Life Sciences
  2004 International Symposium on Micro-Nanomechatronics and Human Science (MHS 2004), Nagoya University, Japan, pages: 1 - 6
• Daub M, Kaack RM, Gutmann O, Steinert C, Niekrawietz R, Koltay P, de Heij B, Zengerle R
  Microfluidics and Beyond - Devices for Applications in Biotechnology
  2004 San Francisco, USA Proc. MRS Symposium R 2004
• Litterst C, Kohnle J, Ernst H, Messner S, Sandmaier H, Zengerle R, Koltay P
  Mobility of Gas Bubbles in CHIC-type Flow Channels
  2004 Proc. ACTUATOR 2004; Bremen; Germany , pages: 541 - 544
• Lindemann T, Streule W, Birkle G, Zengerle R, Koltay P
  PipeJet™ – A Simple Disposable Dispenser for the Nanoliter Range
  2004 Bremen; Germany; 14-16 June Proceedings of Actuator 2004, volume: 1, issue: 1, pages: 224 - 227
• Lindemann T, Ashauer H, Goettsche T, Sandmaier H, Yu Y, Peters R, Sassano D, Bellone A, Scardovi A, Zengerle R, Koltay P
  Thermal Bubble Jet Printhead with Integrated Nozzle Plate
  2004 International Conference on Digital Printing Technologies, Salt Lake City, Utah, United States Proceedings of NIP20, volume: 1, issue: 1, pages: 834 - 839
• Lindemann T, Sassano D, Bellone A, Zengerle R, Koltay P
  Three-Dimensional CFD-Simulation of a Thermal Bubble Jet Printhead
  2004 March 7-11, Boston, Massachusetts, U.S.A. Proc. MSM 2004, volume: 2, pages: 227 - 230

2003

• Steger R, Bohl B, Moosmann C, Birkle G, Zengerle R, Koltay P
  A highly integrated nanoliter dispensing systemfor fast liquid handling
  2003 October 14-15, Munich, Germany Proc Micro.tec 2003, pages: 563 - 566
• Koltay P, Steger R, Bohl B, Taoufik S, Messner S, Sandmaier H, Zengerle R
  DISPENSING WELL PLATE (DWP): A Highly Integrated Nanoliter Dispensing System
  2003 Boston, USA Transducers '03 Digest of Technical Papers, volume: 1, pages: 16 - 19
• Eberhardt W, Kück H, Koltay P, Sandmaier H, Spritzendorfer M, Steger R, Willmann M, Zengerle R
  Low Cost Fabrication Technology for Microfluidic Devices Basedon Micro Injection Moulding
  2003 October 14-15, Munich, Germany Proc. Micro.tec 2003, pages: 129 - 134

2002

• Steger R, Koltay P, Birkle G, Strobelt T, Sandmaier H, Zengerle R
  A Two-Dimensional Array of Piezostack Actuated Nanoliter Dispensers
  2002 8th International Conference on New Actuators, Bremen, Germany Proc. Actuator 2002, pages: 537 - 541
• Comley J, Koltay P, Steger R, Zengerle R, Sandmaier H, Knebel G, Gerlach A, Gottschlich N
  DWPTM - A new Nanoliter Liquid Handling Tool For uHTS
  2002 8th Annual Conference and Exhibition of the Society for Biomolecular Screening; The Hague, The Netherlands
• Ernst H, de Heij B, Koltay P, Storz M, Sandmaier H, Zengerle R
  Liquid Handling für Life Science Anwendungen
  2002 GMM-Workshop: „Mikrosystemtechnik auf dem Gebiet Life Science”, Jena, Germany
• Koltay P, Birkenmaier B, Steger R, Sandmaier H, Zengerle R
  Massive Parallel Liquid Dispensing in the Nanoliter Range by Pneumatic Actuation
  2002 8th International Conference on New Actuators, Bremen, Germany Proc. ACTUATOR 2002, pages: 235 - 239
• Koltay P, Daub M, Steger R, Birkle G, Birkenmaier B, Zengerle R
  Miniaturized screening using a Dispensing Well Plate
  2002 San Diego, USA Proc High-Throughput Screening & Miniaturization Technologies (screentech)
• Koltay P, Moosmann C, Litterst C, Streule W, Birkenmaier B, Zengerle R
  Modelling free jet ejection on a system level – an approach for microfluidics
  2002 April 22-25, San Juan, Puerto Rico, USA Fifth International Conference on Modeling and Simulation of Microsystems (MSM), pages: 170 - 173
• Koltay P, Moosmann C, Litterst C, Streule W, Zengerle R
  Simulation of a micro dispenser using lumped models
  2002 April 22-25, San Juan, Puerto Rico, USA Fifth International Conference on Modeling and Simulation of Microsystems (MSM), pages: 112 - 115
• Koltay P, Taoufik S, Litterst C, Hansen-Schmidt J, Zengerle R
  Simulation of micro dispensing devices
  2002 Friedrichshafen, Germany Proc. of 20th CAD-FEM Users´ Meeting, International Congress on FEM-Technology

2001

• Peter Koltay, Gerhard Birkle, Reinhard Steger, H. Kuhn, M. Mayer, Hermann Sandmaier, Roland, Zengerle
  Highly parallel and accurate nanoliter dispenser for High Throughput Synthesis of chemical compounds.
  2001 Proc International MEMS Workshop (I-MEMS) 2001 (Singapore, July 4-6, 2001); pp 115-124
• Peter Koltay, Reinhard Steger, Gerhard Birkle, Hsi-Che Huang, Hermann Sandmaier, Roland Zengerle
  Microdispenser array for highly parallel and aqccurate liquid handling.
  2001 SPIE’s International Symposium on Microelectronics and Micro-Electro-Mechanical Systems; (Adelaide, Australia; December 17-19, 2001)

Other publications

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2007

• P. Koltay
  Frei fliegende Mikrotröpfchen
  labor & more, volume: 02/07, page: 60, 2007