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

## TL;DR

Researchers developed antibacterial electrodes for neural devices by combining laser restructuring and zinc oxide coatings, improving both electrochemical performance and infection resistance.

## Contribution

A novel two-step fabrication method for antibacterial electrodes with enhanced electrochemical performance through hierarchical restructuring and ZnO deposition.

## Key findings

- ZnO thin films deposited on hierarchical platinum–iridium electrodes improved electrochemical performance.
- ZnO films showed antibacterial activity against Escherichia coli and Staphylococcus aureus in vitro.
- ZnO recrystallized on the electrode surface after 1,500 electrochemical cycles.

## Abstract

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 Escherichia coli and Staphylococcus
aureus bacterial strains in vitro. The findings of this work highlight a promising strategy for developing
multifunctional, electrochemically active antibacterial electrodes
for next-generation neural interfacing electrodes.