Mussel-inspired strong and tough hydrogel with self-adhesive properties based on dynamic interactions for flexible wearable electronics†

Abstract

Emerging conductive hydrogels showcase profound potential for sophisticated manipulation and various sensing applications. However, it remains challenging to prepare conductive hydrogel materials that combine mechanical toughness, reliable healability, and high adhesion strength for skin comfort. Inspired by the robust adhesive mechanisms of mussel proteins, we present an innovative adhesive hydrogel (PVA–DBA) with exceptional adhesive properties, elasticity, and self-healing capabilities, achieved through the integration of a PVA–DOPA copolymer and Fe³⁺ ions within a PAM-PAA hydrogel. The DOPA groups provide strong interfacial adhesion, yielding an adhesion strength of 63.0 kPa on porcine skin (simulating human skin) under ambient conditions. This adhesion remains repeatable across 6 cycles without residual interfacial traces. Catechol–carboxyl interactions, enhanced by Fe³⁺ coordination, impart the hydrogel with high tensile strength, stretchability, and toughness while accelerating gelation kinetics. The unique structural composition of the hydrogel provides multiple functional groups (–NH₂, –COOH, and catechol), collectively reinforcing mechanical stability and self-healing performance, achieving an impressive strain self-repair rate of 81.2%. The resultant PVA–DBA hydrogel demonstrates mechanical robustness, adhesive functionality, and sensitive conductivity, which make it highly suitable for integration into sensing devices that detect bodily motions such as finger, elbow, and knee bending, with a response time of 400 ms. Furthermore, this hydrogel holds potential in sports applications, effectively recording stretching and bending movements, marking a significant advancement in the development of intelligent and responsive material systems.