Electrochemical investigation of platinum electrode corrosion under neurostimulation protocols

Abstract The long-term stability of the electrode-tissue interface is crucial for neural implant longevity. Platinum is the most commonly used material for stimulation electrodes. To investigate electrode corrosion in neurostimulation, we developed an automated setup combining a preclinically used neurostimulator, a potentiostat, and an oscilloscope to monitor electrode surface state over billions of pulses. Using thin-film platinum electrodes allowed nanometer-scale tracking of material loss via profilometry. Comparing clinically relevant protocols with pulse widths in the microsecond-scale revealed the driving process behind accelerated electrode corrosion to be cyclic oxidation and subsequent reduction of the previously formed surface oxide. Our findings indicate that current-controlled neurostimulation can lead to platinum corrosion, also within common limits of safe stimulation, dependent on the occurring faradaic processes. In situ monitoring of potentials with respect to the electrochemical potential scale and tracking of electrode surface state are crucial for understanding and ultimately preventing electrode corrosion during long-term neurostimulation.