Abstract
We propose a new method to fabricate micro-apertures for on-chip electrophysiological measurements of living cells. Thermal reflow of phosphosilicate glass (PSG) is applied to funnel- or nozzle-type microstructures to generate very smooth surfaces on the finalized chip. Such 3-dimensional microstructures show close similarities to fire-polished glass pipette tips. Immobilized cells fit perfectly to these structures offering a large contact area for sealing between the cell membrane and the oxide surface. A tight cell/chip-aperture seal is an important requirement for the present application. We demonstrate the formation of stable gigaseals with Chinese hamster ovary (CHO) cells for both types of microstructures without the need of any post-fabrication surface treatment. By adjusting the PSG reflow parameters, the shape of the apertures can be modified and diameters down to the sub-micrometer range may be achieved. The application of PSG reflow to MEMS fabrication is an interesting new option to create unconventional microstructures.
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Acknowledgments
The authors would like to thank Prof. J.-D. Horisberger (Department of Pharmacology and Toxicology, UNIL, CH-Lausanne) for stimulating discussions on issues related to the patch-clamp technique. The authors also thank the EPFL Center of MicroNano Technology (EPFL-CMI), in particular Dr. C. Hibert (dry etching) and Dr. Ph. Langlet (PSG deposition) for help in the process development, as well as Dr. D. Bouvet (EPFL-LEG1, chemical–mechanical polishing) and J. Steen (EPFL-LMIS1, AFM measurements).
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Lehnert, T., Nguyen, D.M.T., Baldi, L. et al. Glass reflow on 3-dimensional micro-apertures for electrophysiological measurements on-chip. Microfluid Nanofluid 3, 109–117 (2007). https://doi.org/10.1007/s10404-006-0111-x
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DOI: https://doi.org/10.1007/s10404-006-0111-x