A Hydrophilic Underwater Tissue Adhesive With Interfacial Conformity and Viscoelastic Displacement.

Adhesives that exhibit strong adhesion in wet and underwater environments are valuable in many biomedical applications. However, the presence of water substantially hinders contact between adhesives and substrates, leading to adhesion failure. In this study, a hydrophilic underwater adhesive (HUA) that can instantly adhere to wet and underwater tissues was constructed using a step-by-step photocrosslinking strategy to adjust hydrogel viscoelasticity. The HUA synergistically combined two core functional layers: adaptive fitting with interface morphology (i.e. "interface conformal") and the removal of interfacial bound water by viscoelastic displacement. The HUA could instantly adhere to organs (e.g., heart and esophagus) underwater and to various substrates (e.g., polyimide, iron, titanium, etc.). In this study, the HUA performed well in skin wound closure and repair and markedly reduced blood loss and bleeding time in wounded livers owing to its superior underwater adhesion ability. This study demonstrates a promising strategy to construct instant and strong underwater tissue adhesives in complex physiological environments (e.g., different pH values or types of liquids), which may promote the further development of high-performance underwater tissue adhesives.