Engineering Reversible Wet Adhesion: Physicochemical Principles from Molecular Interactions to Functional Biointerfaces

Interfacial hydration fundamentally constrains adhesion in aqueous and physiological environments by preventing intimate contact, competing for binding sites, and weakening the load-bearing interfaces. Although wet adhesives have been extensively designed for durable fixation, emerging technologies in soft robotics, wearable bioelectronics, and minimally invasive medicine require interfaces that can form adhesion, recover after reuse, or detach on-demand under hydrated conditions. This Review discusses reversible wet adhesion through two operational modes: Mode I, cyclic reusability through repeated restoration of adhesion over attachment-detachment cycles, and Mode II, on-demand detachability through trigger-induced conversion of a stable adhesive state into a weakly adherent state through a controlled, low-damage release pathway. We examine supramolecular interactions, dynamic covalent chemistry, mesoscale architectures, biomimetic designs, and hybrid strategies as complementary routes for regulating hydration, interfacial binding, mechanical dissipation, and adhesive state transitions at wet interfaces. We analyze how contact formation, hydration history, fracture pathways, loading history, test geometry, and biofluid exposure shape the measured performance. We further assess current methods for quantifying reusability, switching, durability, and biofluid tolerance, emphasizing failure mode-informed evaluation and standardized reporting criteria. Integrating hydration thermodynamics, binding kinetics, mechanical dissipation, and stimulus-gated interfacial transitions, this Review develops design and evaluation principles for reversible wet adhesive systems in complex aqueous and biointerfacial environments.