High-Density Flexible Parylene-Based Multielectrode Arrays for Retinal and Spinal Cord Stimulation
Novel flexible parylene-based high-density electrode arrays have been developed for functional electrical stimulation in retinal and spinal cord applications. These electrode arrays are microfabricated according to single-metal-layer and, most recently, dual-metal-layer processes. A new heat-molding process has been implemented to conform electrode arrays to approximate the curvature of canine retinas, and chronic implantation studies have been undertaken to study the mechanical effects of parylene-based prostheses on the retina, with excellent results to date. Electrode arrays have also been implanted and tested on the spinal cords of murine models, with the ultimate goal of facilitation of locomotion after spinal cord injury; these arrays provide a higher density and better spatial control of stimulation and recording than is typically possible using traditional fine-wire electrodes. Spinal cord stimulation typically elicited three muscle responses, an early (direct), a middle (monosynaptic), and a late (polysynaptic) response, classified based on latency after stimulation. Stimulation at different rostrocaudal levels of the cord yielded markedly different muscle responses, highlighting the need for such high-density arrays.
Additional Information© 2007 IEEE. This work was supported in part by the Engineering Research Centers Program of the National Science Foundation under NSF Award Number EEC-0310723, and by a fellowship from the Whitaker Foundation (D.R.). The authors especially wish to thank Mr. Christian Gutierrez and Ms. Ronalee Lo for their help with the fabrication of the PDMS washers used with the retinal tacks, Mr. Andrew Pullin for his help with fabrication of the heat-forming mold, and Mr. Trevor Roper for his always valuable assistance.
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