Publikationsliste Dr. Michael Jehle

• Originalarbeiten in wissenschaftlichen Fachzeitschriften
• Konferenzbeiträge

Originalarbeiten in wissenschaftlichen Fachzeitschriften

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2020

• M. Schulz, S. Calabrese, F. Hausladen, H. Wurm, D. Drossart, K. Stock, A. M. Sobieraj, F. Eichenseher, M. J. Loessner, M. Schmelcher, A. Gerhardts, U. Goetz, M. Handel, A. Serr, G. Haecker, J. Li, M. Specht, P. Koch, M. Meyer, P. Tepper, R. Rother, M. Jehle, S. Wadle, R. Zengerle, F. von Stetten, N. Paust, N. Borst
  Point-of-care testing system for digital single cell detection of MRSA directly from nasal swabs
  2020 Lab Chip, Band: 20, Seiten: 2549 - 2561
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  Kurzfassung

  We present an automated point-of-care testing (POCT) system for rapid detection of species- and resistance markers in methicillin-resistant Staphylococcus aureus (MRSA) at the level of single cells, directly from nasal swab samples. Our novel system allows clear differentiation between MRSA, methicillin-sensitive S. aureus (MSSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS), which is not the case for currently used real-time quantitative PCR based systems. On top, the novel approach outcompetes the culture-based methods in terms of its short time-to-result (1 h vs. up to 60 h) and reduces manual labor. The walk-away test is fully automated on the centrifugal microfluidic LabDisk platform. The LabDisk cartridge comprises the unit operations swab-uptake, reagent pre-storage, distribution of the sample into 20 000 droplets, specific enzymatic lysis of Staphylococcus spp. and recombinase polymerase amplification (RPA) of species (vicK) – and resistance (mecA) -markers. LabDisk actuation, incubation and multi-channel fluorescence detection is demonstrated with a clinical isolate and spiked nasal swab samples down to a limit of detection (LOD) of 3 ± 0.3 CFU μl−1 for MRSA. The novel approach of the digital single cell detection is suggested to improve hospital admission screening, timely decision making, and goal-oriented antibiotic therapy. The implementation of a higher degree of multiplexing is required to translate the results into clinical practice.

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, Band: 6, Seite: 036514
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  Kurzfassung

  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.
• 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, Band: 180, Seiten: 83 - 90
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  Kurzfassung

  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.

Konferenzbeiträge

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2020

• P. Koch, O. Barth, M. Meyer, R. Streller, R. Zengerle, M. Rombach, M. Jehle
  Microthermoforming: Enhancing blister technology to introduce microstructures in functional packaging
  2020 12. European Thermoforming Conference, Geneva, Switzerland, 18.-20.03.2020

2017

• 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
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  Kurzfassung

  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.

2015

• 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, Band: 120, Seiten: 1103 - 1106
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  Kurzfassung

  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.