Hydrated ion diffusion-driven interfacial adhesion and failure mechanisms in electroadhesion hydrogels: A digital image correlation-based investigation

The electroadhesion strategy driven by hydrated ion diffusion in functional hydrogels enables controllable soft interface adhesion, offering a new solution for smart interfacial interactions. This is crucial for various engineering applications such as tissue repair, soft robotics, and wearable electronics. However, the intrinsic mechanisms of interfacial adhesion and failure associated with the electroadhesion strategy remain unclear. With an incremental digital image correlation (DIC) technique, we comprehensively investigated the spatiotemporal dynamics of interfacial deformation and failure modulated by electrically controllable hydrated ion diffusion in electroadhesive hydrogels. We also visualized the spatiotemporal evolution of mechanical properties near adhesion interfaces, including interfacial toughness, initial elastic modulus, and nominal secant modulus, under various electrical stimulations. Furthermore, we recognized the transition of adhered specimens from adhesive failure to cohesive failure, driven by the applied external electrical stimulation. This work not only presents a DIC-based characterization method for quantifying the mechanical responses of adhesive interfaces in functional hydrogels, but also provides insights into how electrically regulated hydrated ions dominate interfacial adhesion and failure dynamics in electroadhesive hydrogels, which paves the way to guide the design of future high-performance electroadhesive hydrogels.