Structural analysis of explanted microelectrode arrays

Structural analysis of explanted and Utah microelectrode arrays (MEA) was performed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) to determine the impact of prolonged exposure to the in vivo environment. The MEAs, one designed for recording and one designed for stimulation, had been implanted in the pre- and postcentral gyri, respectively, of a rhesus macaque for 362 days, prior to explantation. Possible processing, handling or implantation damage was observed on individual electrodes on each MEA. Metal degradation/delamination was observed on the stimulating MEA while residual carbon-based matter on the electrode sites and small fissures in the insulation were observed on the recording MEA. The electrode area of the recording MEA had a 5.0x range and the stimulating MEA had a 7.6x range, which did not appear to be related to long-term exposure to tissue.