Electrochemical stability and neural recording with sputtered ruthenium oxide electrodes subchronically in rat motor cortex.

. To investigate sputtered ruthenium oxide (RuO) as a low impedance coating for recording neural activity with intracortical microelectrode arrays (MEAs).RuOwas sputtered onto active sites of amorphous silicon carbide (a-SiC) MEAs and evaluated electrochemically and as a recording electrode coating over 6 weeks in rat motor cortex. The RuOwas 250 nm thick with a 200mgeometric electrode surface area. We performed weekly electrochemical impedance spectroscopy and cyclic voltammetry (CV) measurements and single-unit action potential recordings.From 1 to 6 weeks post-implantation, we observed that median 1 kHz impedance decreased from 1.06 MΩ to 0.68 MΩ, median 1 Hz impedance decreased from 24.5 MΩ to 20.7 MΩ, and median 30 kHz impedance remained constant at 0.19 MΩ. Linear regression fits indicated that the 1 kHz and 1 Hz impedance exhibited small decreases whereas the 30 kHz impedance values had no discernible trend. The CV-based charge storage capacity (CSC) also exhibited consistency over time. The median CSCat 50 mV swas 24.3 mC cmon week 1 and 20.1 mC cmat week 6. At 50 000 mV ssweep rate, the median CSCwas 2.4 mC cmat 1 week and 2.8 mC cmat 6 weeks. Regressions for both sweep rates exhibited no significant slope deviations from zero. Neural recordings spanning 6 weeks demonstrated consistent single unit action potential with a 75% single unit active-electrode-yield over 6 weeks. Medianvalues on week 1 were 97.6V and 105V by week 6. The median and quartile signal-to-noise ratio (SNR) was 12 at week 1 and 12 at week 6. There were no deviations from zero on the regressions for bothand SNR.The findings suggest that RuOis stable over subchronic implantation periods. Future research will explore long-term chronic performance and broader applications of RuOin neural interface devices.