Hierarchically Restructured Antibacterial Electrodes for Neural Interfaces: Electrochemical and Microstructural Evolution under Extended Cycling

Hierarchically restructured platinum-iridium electrodes offer high electrochemical performance for neurostimulation and cardiac rhythm management devices but require added antibacterial functionality to reduce postsurgical infection risks. In this work, electrochemically active antibacterial platinum-iridium electrodes were developed using a two-step process. First, the electrodes were restructured using a femtosecond laser hierarchical surface restructuring. In the second step, reactive magnetron sputtering from a pure zinc target in an Ar/O₂ gas mixture was employed to deposit antibacterial zinc oxide (ZnO) thin films onto the hierarchical surface structure of the electrodes, thereby imparting antibacterial properties. X-ray diffraction and X-ray photoelectron spectroscopy confirmed the formation of ZnO. The electrochemical performance of the electrodes increased with the ZnO film deposition time. This enhancement is attributed to the nonconformal nature of the ZnO layer over the complex electrode topography, as revealed by scanning electron microscopy (SEM). SEM imaging combined with energy-dispersive spectroscopy (EDS) mapping after electrochemical cycling revealed the gradual dissolution of ZnO into the electrolyte and the recrystallization of ZnO on the electrode surface after 1,500 cyclic voltammetry (CV) cycles (24 h), likely due to the confined electrolyte environment. Electrodes coated with ZnO films exhibited significant antibacterial activity against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> bacterial strains <i>in vitro</i>. The findings of this work highlight a promising strategy for developing multifunctional, electrochemically active antibacterial electrodes for next-generation neural interfacing electrodes.