Individually-addressable parylene microneedle arrays with integrated microchannels for retinal prosthesis study

Retinal prostheses promise to provide artificial vision to the blind. Retinal implant based on electrical stimulation has limitations such as electrode corrosion, water hydrolysis, and generation of toxic radicals due to the large stimulation current. The more naturalistic chemical stimulation is able to effectively address these limitations of electrical stimulation. This paper reports the development of out-of-plane parylene microneedle arrays that can be individually addressed by integrated microchannels. The individually-addressable microneedle arrays were fabricated using silicon molds formed by DRIE, isotropic silicon etching of XeF₂, and the conformal coating of parylene. Both rigid and flexible devices were developed. These devices enable the delivery of chemicals with controlled temporal and spatial patterns and allow us to study neurotransmitter-based retinal prostheses.