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Y. Xu, R.B. Katragadda1, G.W. Abrams, R. Iezzi; Fabrication of Stimulating Electrodes With Integrated Microfluidic Channels for Retinal Prostheses . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3173.
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© ARVO (1962-2015); The Authors (2016-present)
To develop an integrated electrical/microfluidic retinal prosthesis device that combines patterned electrical stimulation with the concomitant patterned microfluidic release of neuromodulators.
Surface micromachining techniques were employed to fabricate retinal prosthesis devices. 5 µm parylene C was deposited upon silicon at room temperature using a highly conformal, vapor phase process. Next, 20 µm photoresist (AZ4620) was patterned to form the microchannel sacrificial layer followed by the deposition of a second layer of parylene C. A gold layer was then evaporated upon a chromium adhesion layer and patterned to form traces and circular electrodes with diameters of 50 µm, aligned with the microfluidic channels. Electrical traces and electrodes were then insulated using another thin layer of parylene C. In the next step, releasing holes were formed by patterning parylene to expose a photoresist sacrificial layer. Note that gold electrodes were exposed in this step as well. The photoresist sacrificial layer was then dissolved in acetone to render free standing channels. Exploiting the properties of stiction in microstructures, we accelerated the photoresist dissolution process by adding self–sealing structures along the length of the channels. These structures were are open during the dissolution of photoresist and sealed once they were removed from the solution. This method can be used to fabricate very long microchannels, easily. Finally, the device was separated from the silicon wafer by HF dip.
Parylene microfluidic/electrode devices were chemically inert and demonstrated no observable swelling in water. Electrical contacts were intact along their length. Microfluidic structures permitted spatially and temporally controlled ejection of fluorescein as observed using an inverted microscope.
Stimulating electrodes with integrated microfluidic channels were successfully fabricated. Such devices will permit patterned electrical stimulation, concomitant with the spatially and temporally controlled release of neuromodulators.
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