A Bioinspired Hydrogel with Balanced Adhesion and Compliance for Reversible Underwater Adhesion

Abstract

Achieving strong yet reversible underwater adhesion while maintaining low mechanical stiffness remains a key challenge for hydrogel adhesives, especially for temporary stabilization of fragile submerged objects. Here, we report a bioinspired ternary hydrogel in which hydrophobicity is functionally balanced to reconcile adhesion, compliance, and salt tolerance. By systematically tuning hydrophobic content within a cationic polymer network, we construct a hydrogel framework that suppresses salt-induced swelling and restructures hydrogen-bonded water populations, facilitating interfacial dehydration and reversible physical interactions. The resulting hydrogel adopts a tough yet compliant architecture (elastic modulus on the order of 100 kPa) that sustains large stresses while remaining mechanically conformable, enabling stable underwater adhesion (~0.3 MPa) without chemical curing. Importantly, the adhesion is residue-free, reversible, and repeatable across cycles, demonstrating that high interfacial strength can be achieved without sacrificing detachability. Demonstrated under the stringent conditions of in situ stabilization of submerged cultural heritage, this work establishes a composition-balancing strategy for designing tough yet compliant hydrogel adhesives for reversible underwater applications.