Verification, electrode activation, and electrical testing of high-channel count microelectrode arrays

The Utah (Slanted) Electrode Array (U(S)EA) provides a high-density, microelectrode interface for neural recording and stimulation. Device efficacy and longevity is crucial to successful implementation. Determining an array's potential efficacy prior to implantation would prevent low-quality arrays from being used. In addition, determining the failure modes of an array would be useful to manufacturers for improving array quality. The array verification process included soaking the arrays in phosphate-buffered saline. Five failure-mode analysis tests were developed to investigate the failure modes of nonimpedance-stable arrays. Also investigated as a potential failure mode was silicone-coated and non-silicone coated array lead wires. Twenty-four of the 40 arrays verified exhibited impedance decreases greater than 15 %. However, array quality improved substantially during the study. Of the arrays investigated for failure modes, the failure-mode analysis tests suggest that changes in front-side insulation tended to dominate the cause of impedance drops, although other failure modes were seen. In some cases, nonsilicone coated leads wires failed quickly and catastrophically, but the alternative silicone-coated lead wires provided improved longevity and starting impedance. Arrays can further be improved by electrochemically activating iridium-tipped electrodes. These microelectrodes provide a low-impedance, high-charge capacity.