Interfacial Molecular Lock: A Universal Strategy for Hydrogel Adhesion

Hydrogel adhesion is fundamental to a large number of established and emerging fields. The existing adhesion methods have some problems, such as the limited penetration ability of polymers in hydrogels, the interface hardening caused by in situ monomer polymerization, the secondary damage caused by covalent strong bonding during detachment, the need for complementary techniques to induce adhesion, and the complex and impractical operation. Inspired by the adhesion mechanism of mussels, we propose a universal strategy of interfacial molecular lock (IML) for hydrogel adhesion, which is simple to operate. IML is composed of organic (low-molecular-weight) molecules containing catechol groups, which are easy to penetrate into hydrogels. The principle of IML relies on the combination of a dynamic covalent bond, coordination bond, hydrogen bond, pi-pi interaction, and cation-pi interaction. IML can adapt to interfacial chemistry of hydrogels on different substrates and achieve reversible adhesion without external regulation. The molecular micro-polymerization further enhances the stability and strength of hydrogel adhesion. IML is expected to expand hydrogel adhesion in various applications, especially tissue adhesives, wound sealants, wearable devices, and hydrogel-on-metal protection.