Bioinspired Biomaterial Composite for All-Water-Based High-Performance Adhesives

Nature has ingeniously developed adaptable adhesive materials by utilizing versatile chemistry centered around two fundamental components: catechols and polypeptides. This chemistry enables adhesive processes even in underwater environments using water-soluble biological substances, presenting a technological challenge that current synthetic adhesives are unable to meet. In this study, we present a bioinspired adhesive composite that aims to integrate the adhesive mechanisms observed in mussels and barnacles. The composite formulation comprises silk, polydopamine, and Fe³⁺ ions, all derived from organic and non-toxic sources in a water-based medium. By combining the adhesive properties exhibited by <i>Mytilus sp.</i> (mussels) and <i>Cirripedia sp.</i> (barnacles), which rely on proteinaceous filaments and proteic cement, respectively, the composite demonstrates remarkable adhesion capabilities in both dry and wet conditions. In lap-shear tests, it outperforms synthetic commercial glues and other adhesives based on natural polymers, rivaling the effectiveness of leading underwater adhesives. It is worth noting that the composite is entirely biologically sourced, eliminating the necessity for synthetic processes. Moreover, the adhesive production method can be extended to utilize proteins beyond silk by fine-tuning the tyrosine:catechol molar ratio to optimize bonding strength. These findings present a cost-effective and sustainable approach that leverages easily accessible raw materials to develop high-performance adhesives suitable for underwater applications.