Honeycomb Electrode Arrangement Improves Stability of Sputtered Iridium Oxide Electrodes

The stability of thin-film electrodes is critical for the long-term performance of chronic neural implants, specifically, mechanical integrity must be retained. This study systematically evaluated the stability of sputtered iridium oxide film (SIROF) electrodes in a distributed honeycomb arrangement compared to rectangular electrodes. Both electrodes were fabricated to cover equivalent areas of a polyimide (PI) substrate. Electrochemical analysis indicated that both electrodes have comparable electrochemical surface area (ECSA), likely even when coated with PEDOT/PSS, provided the charge density cutoff during electrodeposition is based on ECSA rather than the physical electrode area. The honeycomb electrode demonstrated increased structural integrity in tape tests and in cyclic voltammetry (CV) designed to intentionally induce delamination through gas evolution in water-splitting reactions. These findings suggest that distributing small, interconnected electrodes instead of a large continuous electrode increases stability, making it promising for neural implant applications.