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Published June 16, 2008 | metadata_only
Journal Article

Flexible parylene-based multielectrode array technology for high-density neural stimulation and recording


Novel flexible parylene-based high-density electrode arrays have been developed for functional electrical stimulation in retinal and spinal cord prosthetics. These arrays are microfabricated according to a single-metal-layer process and a revolutionary dual-metal-layer process that promises to meet the needs of extremely high-density stimulation applications. While in many cases thin-film platinum electrodes in parylene C would be sufficient, high surface-area platinum electroplating has been shown to extend the lifetime of stimulated electrodes to more than 430 million pulses without failing. Iridium electrode arrays with higher charge delivery capacity have also been fabricated using a new high-temperature stabilized parylene variant, parylene HT. In addition, a new heat molding process has been implemented to conform electrode arrays to approximate the curvature of canine retinas, and a chronic implantation study of the mechanical effects of parylene-based electrode arrays on the retina over a 6-month follow-up period has provided excellent results. Retinal stimulation from these parylene-based electrode arrays in an isolated tiger salamander preparation was shown to be comparable to light stimulation in terms of generation of action potentials in the inner retina. Finally, 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 Elsevier. Available online 12 November 2007. 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 Dr. Jack Whalen and Ms. Aditi Ray for their help with the electroplating and electrochemical testing experiments, Dr. Saloomeh Saati for her help with the in vivo canine studies, Mr. Matthew Behrend for his work on the isolated retina setup, Ms. Ronalee Lo for her 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.

Additional details

August 22, 2023
August 22, 2023