Electro-Chemo-Mechanical Coupling in Electronically Programmable Surface Electrochemical Actuators

Electrochemical nanomembrane actuators offer a route to microscale robots capable of locomotion, interaction, and manipulation. We recently developed platinum (Pt) surface electrochemical actuators (SEAs) that produce large curvature changes through reversible surface oxidation and reduction. Oxide formation during oxidation directly drives the actuator, whereas reduction recovers the initial state. However, the mechanism underlying such self-limited oxidation remains unclear because oxide growth, stress buildup, and bending are intrinsically coupled. Here, we develop an electro-chemo-mechanical model that unifies oxide growth, stress evolution, and curvature generation in Pt SEAs. The model reproduces self-limiting oxidation and identifies two coupled limiting mechanisms: attenuation of the effective electric field as the oxide thickens and compressive stress buildup. We further show that actuation is governed by dynamic stress redistribution within an evolving laminate. With the mapping of the voltage, oxidation time, bilayer geometry, and prestress, the framework defines finite operating windows for efficient, reliable, and programmable microscale actuation.