Supramolecular Hydrogel Showing Mechanical Robustness and Good Adhesion Underwater.

Underwater adhesive materials hold significant application value in fields such as biomedicine and marine engineering. The core performance of these materials lies in the synergistic optimization of their mechanical properties and interfacial adhesive strength. Although supramolecular hydrogels have achieved initial breakthroughs through dynamic bond design, they fail to be mechanically tough and favorably adhesive underwater at the same time. To address this challenge, a strategy to fabricate a supramolecular hydrogel with high crosslinking density using 3D printing technology is proposed. The obtained hydrogel demonstrates excellent mechanical strength due to its high-density hydrogen bonding crosslinks that it retains a tensile stress of 4 MPa and can support a 20 g load without deformation after submersion in water for 30 min. Meanwhile, it displays remarkable self-adhesion property underwater, achieving an interfacial adhesion strength of 690 kPa following 20 min of contact duration. Notably, the hydrogel manifests versatile underwater adhesion capabilities to various substrates. Therefore, a supramolecular hydrogel that integrates both good mechanical performance and adhesion underwater characteristics is successfully developed. In addition, modular soft robots are also constructed using this hydrogel, which is able to successfully complete various underwater missions.