2026-03-102026-03-10https://hdl.handle.net/11420/61945Nanoporous metals, characterized by their high surface-to-volume ratio, have demonstrated promising surface-controlled chemo-mechanical coupling behaviors that can rival or surpass those of bulk functional materials. These behaviors include bidirectional actuation/sensing and switchable elastic compliance. However, there is a trade-off between amplitude and response time. Our goal is to significantly enhance functional performance by designing multiscale hierarchical nanoporous materials that harmonize large amplitude and rapid switching. Nanoscale ligaments at lower hierarchy levels provide high specific surface area for enhanced functional amplitude, while larger pore channels at upper hierarchy levels facilitate efficient mass transport, accelerating response time. Reducing the smallest ligament/pore sizes to single-digit nanometers will create a huge surface area, enabling (1) significant modulation of the elastic modulus and sound velocity in-operando and (2) substantial enhancement of actuation/sensing output signals through reversible electrochemical surface oxidation in an aqueous environment. This provides the basis for sustainable robotic materials for autonomous locomotion and self-reconfiguration. Key scientific questions include: How can we refine and stabilize the microstructure at the lowest hierarchical level while achieving scalable production of these materials in the form of monolithic and mechanically loadable bodies? How can we maximize both the switching kinetics and amplitude of output signals for bidirectional sensing/actuation and switchable mechanical/acoustic properties?