A hydra tentacle-inspired hydrogel with underwater ultra-stretchability for adhering adipose surfaces

Adhesive hydrogels hold great significance in various biomedical applications. However, the maintenance of high extensibility and adhesion to adipose matters still remain challenging. Inspired by hydra tentacles, we utilise flexible polymeric ionic crosslinkers for constructing densely crosslinked networks. The derived hydrogel was ultra-stretchable (over 54 times) even in the fully swollen state in water. Due to dense electrostatic bonding sites and hydrophobic phases, it displayed fast (-30 sec), repeatable and long-lasting (over 14 days) underwater adhesion to adipose surfaces such as fat, octopus and fish epidermis in aqueous environments. Moreover, the excellent cytocompatibility and antibacterial ability made it suitable for a variety of applications related to biomedicine and flexible electronics. This biomimetic work addresses new possibility for the design rationale for highly stretchable and lipophilic underwater adhesives.