Abstract

We report on microfabrication and assembly process development on transparent, biocompatible polymers for patterning electrodes and growing electrically active cells for in vitro cell-based biosensor applications. Such biosensors are typically fabricated on silicon or glass wafers with traditional microelectronic processes that can be cost-prohibitive without imparting necessary biological traits on the devices, such as transparency and compatibility for the measurement of electrical activity of electrogenic cells and other biological functions. We have developed and optimized several methods that utilize traditional micromachining and non-traditional approaches such as printed circuit board (PCB) processing for fabrication of electrodes and growing cells on the transparent polymers polyethylene naphthalate (PEN) and polyethylene terephthalate (PET). PEN-based biosensors are fabricated utilizing lithography, metal lift-off, electroplating, wire bonding, inkjet printing, conformal polymer deposition and laser micromachining, while PET-based biosensors are fabricated utilizing post-processing technologies on modified PCBs. The PEN-based biosensors demonstrate 85–100% yield of microelectrodes, and 1-kHz impedance of 59.6 kOhms in a manner comparable to other traditional approaches, with excellent biofunctionality established with an ATP assay. Additional process characterization of the microelectrodes depicts expected metal integrity and trace widths and thicknesses. PET-based biosensors are optimized for a membrane bow of 6.9 to 15.75 µm and 92% electrode yield on a large area. Additional qualitative optical assay for biomaterial recognition with transmitted light microscopy and growth of rat cortical cells for 7 days in vitro (DIV) targeted at biological functionalities such as electrophysiology measurements are demonstrated in this paper.

Highlights

  • Cell-based biosensors and biofunctional devices such as microelectrode arrays (MEAs, called multielectrode arrays or micromachined probes) have become invaluable tools for scientific discovery, biological multifunctional characterization and medical advancement

  • We expected a thickness of ~5 μm based on a calculation provided by the manufacturer that involved the deposition rate and time but the mean thickness across 18 measurements was closer to 2.39 μm with a standard deviation of 0.29 μm

  • We have developed multiple microfabrication and assembly processes on biocompatible polymers—polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) toward the integration of cell based biosensors such as microelectrode arrays (MEAs)

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Summary

Introduction

Cell-based biosensors and biofunctional devices such as microelectrode arrays (MEAs, called multielectrode arrays or micromachined probes) have become invaluable tools for scientific discovery, biological multifunctional characterization and medical advancement. Since they can actively manipulate and monitor cellular activity both at the single cell and cellular network levels, they provide extraordinary insight into complex neural interactions [1]. Heuschkel et al report the fabrication of three-dimensional (3D) glass MEAs by undercutting a chromium mask with wet etching of glass to create 3D pyramids (less than 100 μm tall) on which metal and SU-8 insulation layers are subsequently defined [18]

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