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AL Lagman, MR Safadi, CA Jaboro, S George, P Siy, R Iezzi, JP McAllister, GW Abrams, GW Auner; Characterization of Nano- and Micro- System Neuro Interfacing Electrode Arrays for the Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4479.
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Purpose: To characterize a multiplexed integrated stimulating/sensing retina implant microarray and its interaction with the retinal neural tissue. Methods: A 10x10 prototype and 64x64 layout of a retinal neuron implant array has been developed. Integrated into the microarray is a single crystal SiC based microbump frontend for interface with neural tissue. The electrode microarray consists of a 6H-SiC single crystal embedded with conductive (10e-4 Ω-cm) zones that match the geometry of our retina chip array. The SiC crystal is epitaxially coated with a wide bandgap nitride semiconductor layer that acts as a 10e12 Ω-cm insulator as well as a biocompatible encapsulation. A unique Excimer laser micro-machining method was used to ablate through the insulating layer aligned to the SiC conductive zones. This controlled energy micro- machining method results in the development of controllable nano- and micro- bump formation ideally suited for a biological interface. We are currently using a measurement set-up that allows us to characterize the array by concurrently stimulating and recording with a multi-electrode array (MEA). A linear stimulus isolator provides the stimuli. In vitro studies using mounted neural tissue on the MEA is used to characterize the stimulus behavior of the retina implant microarray. Results: We have developed a 10x10 and a 64x64 retinal neural implant microarray with neural interfacing consisting of anatomically distributed electrodes containing nano- and micro-bumps tipped with a functionally graded IrO2 alloy. The electrical characterization of the microarray indicates a well-defined stimulatory electric charge that can be produced within a defined spatial region. Conclusion: The electrical and structural characterization of this novel microarray indicates a well-defined neural stimulatory device for the stimulation of retinal tissue.
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