Improved electrode stimulation stability of Utah arrays.

BACKGROUND: The Utah electrode array (UEA) is a promising microelectrode technology with potential applications to assist patients with sensory loss, spinal cord injuries, and limb loss serving as neural prosthetics and brain-computer interfaces. Performance lifetime of microelectrodes, particularly when used for stimulation, remains one of the challenges for their clinical translation. METHODS: This study characterizes the stimulation stability of an optimized iridium oxide (IrOx) research metallization for the UEA in comparison to the Blackrock standard practice metallization. The stimulation stability (Stim-Stab) protocol used electrochemical characterization and either 106 or 4 × 106 pulses at 2,100 µA (420 nC/ph) with longitudinal voltage transient measurements and physical characterization to quantify electrode lifetime. RESULTS: Approximately 50% of electrodes using the Blackrock standard practice process electrical failed during 106 pulses, whereas no electrical failures were observed from 4 × 106 pulses for the research metallization. Backscattered scanning electron microscopy (BSEM) determined that all electrodes with electrical failures during Stim-Stab testing had complete loss of metallization. Of electrodes with good electrical outcomes from Stim-Stab testing 80% and 50% of those had notable metallization damage for BRM and research metallization, respectively. CONCLUSIONS: These results suggest that the research metallization makes important steps for improving electrode metallization lifetime of Utah arrays. Additionally, the Stim-Stab method provides valuable feedback for engineering improved electrode metallization.