Effects of membrane surface pretreatment on ionic polymer-metal composite (IPMC) actuation and scanning electrochemical microscopy (SECM) analysis

Abstract This study investigates how membrane surface pretreatment, including sanding and chemical cleaning, affects the electrochemical and mechanical performance of ionic polymer–metal composites. IPMC samples fabricated under varying surface pretreatment conditions were characterized in terms of electrode morphology, surface resistance, water uptake, electrode thickness, and actuation behavior. Scanning electrochemical microscopy (SECM) was employed to visualize cross-sectional electrode architecture and assess local electrochemical activity. Results show that surface roughening promotes thicker, more continuous platinum electrode layers with deeper membrane penetration, reduced surface resistance, and more stable and amplified actuation. While cleaning alone decreased water uptake, it enhanced surface conductivity and actuation compared to uncleaned samples. The fully treated IPMC, which combined sanding and cleaning, exhibited the largest and most stable tip displacement. SECM imaging provided direct spatial mapping of electrochemically active regions, distinguishing the electrode and membrane domains. These findings underscore the critical role of membrane surface pretreatment in optimizing IPMC performance and highlight the potential of SECM for advancing the fundamental understanding and design of high-efficiency ionic soft actuators.