Designing Bio-Inspired Wet Adhesives through Tunable Molecular Interactions

Marine organisms, such as mussels and sandcastle worms, can master rapid and robust adhesion in turbulent seawater, becoming leading archetypes for the design of underwater adhesives. The adhesive proteins secreted by the organisms are rich in catecholic amino acids along with ionic and amphiphilic moieties, which mediate the adaptive adhesion mainly through catechol chemistry and coacervation process. Catechol allows a broad range of molecular interactions both at the adhesive-substrate interface and within the adhesive matrix, while coacervation promotes the delivery and surface spreading of the adhesive proteins. These natural design principles have been translated to synthetic systems toward the development of biomimetic adhesives with waterresist adhesion and cohesion. This review provides an overview of the recent progress in bio-inspired wet adhesives, focusing on two aspects: (1) the elucidation of the versatile molecular interactions (e.g., electrostatic interactions, metal coordination, hydrogen bonding, and cation-pi/anion-pi interactions) used by natural adhesives, mainly through nanomechanical characterizations; and (2) the rational designs of wet adhesives based on these biomimetic strategies, which involve catechol-functionalized, coacervation-induced, and hydrogen bondbased approaches. The emerging applications (e.g., tissue glues, surgical implants, electrode binders) of the developed biomimetic adhesives in biomedical, energy, and environmental fields are also discussed, with future research directions proposed.

Automated summary

Marine organisms like mussels and sandcastle worms have the ability to adhere rapidly and strongly in turbulent seawater, making them ideal models for underwater adhesive design. The adhesive proteins they secrete contain catecholic amino acids, as well as ionic and amphiphilic components, which enable adaptive adhesion through catechol chemistry and coacervation. These natural principles have been applied to the development of biomimetic adhesives with water-resistant adhesion and cohesion.