Algae-mussel-inspired hydrogel composite glue for underwater bonding

Inspired by the adhesive strategies of brown algae and marine mussels, we developed a novel hydrogel composite glue formed from initially separate adhesive and polymer precursors. These components then formed a network during application by coordinating with ferric ions. This approach enabled us to turn a non-adhesive polymer, alginate, into an adhesive gel with good performance, which was not possible with conventional methods utilizing chemical conjugation of catechol functionality. Sequential deposition of precursors, mimicking algae, was found to outperform the direct mixing of components before application. The resulting glue does not require chemical conjugation, and yet can strongly bond dissimilar materials completely submerged in water.