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0926-CC06-02

Polymer-Based Microelectrode Arrays Scott Corbett1,2, Joe Ketterl1, and Tim Johnson2 1 MicroConnex, 34935 SE Douglas St., Suite 110, Snoqualmie, WA, 98065 2 Advanced Cochlear Systems, 34935 SE Douglas St., Suite 110, Snoqualmie, WA, 98065

ABSTRACT We have developed flexible, polymer-based electrodes for potential medical applications including neural recording and stimulation. Using various combinations of liquid crystal polymer (LCP) substrates, implantable grade silicone and polyimide, we have developed and tested several prototype multi-layer, polymer electrodes. We report here on two specific electrodes. In the first case, a multilayer electrode consisting of high-melt temperature liquid crystal polymer (LCP) material with patterned electrodes of sputter deposited and plated gold, laminated together with a lower-melt temperature LCP, was produced. Iridium oxide was deposited on the exposed electrode sites to facilitate effective charge transfer for neural stimulation. The electrode was designed for acute implantation in a cat cochlea and contained 12 contacts, with a pitch of 200 microns. The small contact spacing allowed testing of electric field focusing techniques both in vitro and in vivo. We subjected the electrodes to electrical and mechanical tests to assess its likely suitability as a long-term biomedical implant. Chronic electrical leakage testing indicated ionic permeability of the low and high temperature LCP interface that was higher than that desired. In a second case, we produced a mock circuit using high-melt LCP and medical grade low durometer silicone in place of the low-melt LCP as the interlayer adhesive. Mechanical and electrical testing of the hybrid design indicated the potential to fabricate cochlear electrodes containing up to 72 contacts with a footprint and mechanical performance similar or better than current commercially available cochlear implant arrays (containing up to 24 elements). Multi-layer polymer electrode technology offers the opportunity to create new electrodes with higher numbers of channels, offering improved performance in neural stimulation applications including cochlear implants, retinal arrays, deep brain stimulators and paraplegic remobilization devices.

INTRODUCTION Neurostimulation systems are an emerging class of medical devices promising miraculous treatments for otherwise intractable medical conditions [1]. The most successful example to date is the cochlear implant, which directly stimulates auditory neurons to partially restore hearing in the deaf [2]. Other emerging treatments include retinal arrays to restore sight, deep brain stimulators to treat Parkinson’s disease and paraplegic remobilization systems [3]. All of these devices rely on electrode arrays to transfer the electrical current that elicits neural responses. To date, most electrodes have been patterned after cardiac pacemaker electrode technology, relying on insulated wires, platinum foil or metal electrodes and medical grade

silicone encapsulation. These mechanical assemblies