A bionic strong and tough amphibious adhesive inspired by barnacles and articular cartilage

Developing strong and tough amphibious adhesives that can achieve high adhesion strength in both dry and wet environments remains a major challenge. Herein, inspired by the hydrophobic–hydrophilic adhesion strategy of barnacle cement proteins and the fibre-reinforced load-bearing structure of articular cartilage, a bioinspired polyurethane adhesive (TA@WS₂/PU) with strong, tough, and durable underwater adhesion was developed. In this system, catechol-containing chain extenders were introduced to provide robust substrate anchoring, while fluorinated polyimide segments induced pronounced microphase separation and generated low-surface-energy hydrophobic nanodomains for interfacial dewetting. Furthermore, tannic-acid-modified tungsten disulfide nanosheets (TA@WS₂) were incorporated into the optimized polyurethane matrix to construct a cartilage-mimetic reinforcing network, in which high-aspect-ratio nanosheets acted as load-bearing skeletons and tannic-acid-rich surfaces formed dense hydrogen-bonding interactions with polyurethane chains. The resulting 10%-TA@WS₂/PU adhesive (the addition of TA@WS₂ is 10 wt%) exhibited a tensile strength of 108 MPa, elongation at break of 1150%, and toughness of 371 MJ·m^-3, together with a dry lap-shear strength of 9.6 MPa on Fe substrates. More importantly, it achieved an underwater lap-shear strength of 4.2 MPa and maintained excellent interfacial stability during prolonged aqueous exposure. Multiscale analyses across molecular, microscopic, and macroscopic scales revealed that the superior underwater adhesion originated from the cooperative effects of hydration-layer disruption, exposed adhesive groups, compact microphase-separated packing, and nanosheet-induced diffusion barriers. This dual-bioinspired strategy provides a promising route for developing strong, tough, durable, and recyclable amphibious adhesives.