Microstructure-Wettability Relationships on Arrays of Electrodeposited Re-entrant Copper Micromushrooms

Abstract

Omniphobic antiwetting surfaces could play an essential role in enhancing performance in certain nonaqueous electrochemical systems, and a possible route to achieve durable repellency is the scalable fabrication of metallic re-entrant microstructures. This study systematically investigates the microstructure-wettability relationships of arrays of electrodeposited copper micromushrooms. Singly and doubly re-entrant architectures were fabricated using a combination of photolithography and electrodeposition. The impact of geometric parameters, including pillar diameter, center-to-center spacing, and overhang width, on the measured contact angle was evaluated across a range of solvents with varying surface tensions. An optimized singly re-entrant geometry maximized contact angle for high- and intermediate-surface-tension liquids but failed to prevent the wetting of low-surface-tension solvents like methanol. Synergistic effects were observed when combining these microstructures with perfluoroalkyltrichlorosilane coatings, which significantly reduced surface energy and enabled repellency for even low-surface-tension fluids. While doubly re-entrant structures were successfully fabricated, their rounded cap morphology limited additional antiwetting benefits compared to singly re-entrant designs. These findings provide design guidelines for developing robust, scalable, and conductive antiwetting surfaces suitable for gas diffusion electrodes and other electrochemical applications.