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Bruce W. McKee, Marcus D. Gingerich, Stuart F. Cogan, Douglas B. Shire, John L. Wyatt, Joseph F. Rizzo, III; A Microfabricated Chronic Percutaneous Penetrating Electrode Array for a Subretinal Prosthesis. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5545. doi: https://doi.org/.
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This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind. The specific purpose of this presentation is to describe our efforts to develop microfabricated chronic percutaneous penetrating electrode array on polyimide-based flexible carriers that will place the stimulating electrodes nearer the target cells and thereby potentially decrease the threshold current. The hypothesis was that such penetrating structures could be realized using microfabrication technology.
A chronic percutaneous electrode array was designed in CAD based on our experimental design parameters and the need to elevate sputtered iridium oxide film (SIROF) stimulating electrodes above the polyimide carrier. The penetrating electrode microfabrication process was based on prior successful Boston Retinal Implant processes for creating polyimide-based electrode arrays, encapsulating these arrays in silicon-carbide (SiC), and depositing SIROF stimulating electrodes. The overall process involves spin coating of photoresists and polyimide, microlithography, physical vapor deposition (PVD), plasma enhanced chemical vapor deposition (PECVD), wet and dry etching, and electroplating. These devices are fabricated on standard 500 micron-thick Si carrier substrates and then removed upon process completion.
A set of microfabrication processes was successfully engineered to integrate SU-8 posts to elevate the SIROF electrodes above the flexible polyimide carrier with SiC wrapped conductor metal. Histology studies with similar configurations have shown good biocompatibility with Yucatan mini-pig retinal tissue.
A means of fabricating a SiC-protected, flexible polyimide-based penetrating electrode array has been developed. This microfabrication technology may provide the basis for a future in vivo component of the Boston retinal prosthesis.
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