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X. Sui, Y. Xie, Y. Li, T. Liang, G. Li, G. Zhou, Q. Ren; Fabrication and in vitro Biocompatibility of Flexible Polyimide-Based Microelectrode Array for Visual Prosthesis. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3010.
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To fabricate and encapsulate multi-channel flexible polyimide-based microelectrode array and to evaluate the in-vitro biocompatibility with optic glial cells for visual prosthesis.
A low-cost MEMS process was utilized to fabricate the flexible microelectrode array. The 1µm aluminum was evaporated on the polished surface of silicon wafer as a sacrificial layer. The lower 5µm photosensitive polyimide was spin-coated onto the aluminum for insulation. Sputtering and lift-off techniques were applied to form the Ti/Pt thin film for stimulation sites, connecting line, and the bonding pads. The upper 5µm polyimide was obtained to insulate the connecting lines with windows opened to expose the stimulating sites and the bonding pads. The 5µm-deep recess was formed to define the configuration of the microelectrode. The aluminum layer is etched by electrochemical method, and the microelectrode was then released using the recess. The microelectrode array by MEMS technology was encapsulated for in-vitro biocompatibility. Enameled wires were utilized as the lead cables to electrically connect each bonding pad with an 18-pin connector. Based on a custom mold, the medical-grade silicone gel was used to seal the bonding pad area and the wire bundle to improve the biocompatibility. Four 3-day SD rats were selected as the experimental animal. Astroglias grew from the cut 2mm-length optic nerves of the rats. Number and modality of astroglias were contrasted each other between with and without micro-current stimulation by microelectrode array in the culture chamber
In-vitro biocompatibility results showed that proliferation and differentiation of the glial cells did not affected by the polyimide material without electrical stimulation. The micro-current stimulation do not inhibit growth of the glial cells at first and the number reduced gradually with time going on. With further in-vitro experiment, optimum stimulation conditions can be determined to realize biocompatibility with the glial cells.
Fabrication and encapsulation of the multichannel flexible polyimide-based microelectrode array were presented and in-vitro biocompatibility with optic glial cells was evaluated. Study results can supply effective design requirements for microelectrode array.
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