A comparative study of the corrosion behaviour of flexible dry electrodes based on Ti-Cu thin films

Abstract

This work investigates the surface behaviour of Ti-based dry electrodes subjected to artificial sweat corrosion, aiming to assess their suitability for long-term neuromuscular rehabilitation in e-health applications. Three types of dry electrodes were prepared by PVD magnetron sputtering, depositing titanium (Ti), titanium dopped with copper (TiCu_0.34) and Copper (Cu) thin films on flexible polylactic acid (PLA) polymeric substrates. The electrodes were submitted to corrosion resistance testing using electrochemical methods, including open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The results were analysed attending to the films’ chemical composition, crystalline structure, roughness, and morphology. Despite exposure to corrosive environments, Ti and TiCu_0.34 electrodes exhibited minimal surface degradation, with no significant differences in corrosion rate (passivation current densities of approximately 8 and 11 × 10^–6 A·cm^-2, respectively). Importantly, the electrical resistivity of the Ti-based electrodes remained stable, with post-corrosion values (TiCu_0.34: 10 µΩ·m, Ti: 9 µΩ·m) remaining within the pre-corrosion range (< 10.0 µΩ·m), indicating strong surface integrity. The findings underscore the strong corrosion resistance and consistent electrical performance of TiCu_0.34 thin films, making them promising candidates for long-term use in wearable e-health devices.