Biomimetic Construction of Adhesive, Self-Healing and Antifatigue Hydrogels via Galactomannan-Induced Double-Network Cross-Linking for Flexible Strain Sensors

Hydrogels endowed with adhesive and self-healing properties are eagerly anticipated in the realm of flexible sensors. However, the current single-network structure of these hydrogels often struggles to withstand significant mechanical loads, forming a major limitation hindering their broad application. To address this, a three-dimensional network was created using P(NIPAM-co-DMAPAA) through free-radical polymerization of the cross-linked monomers N,N-dimethylaminopropylacrylamide (DMAPAA) and N-isopropylacrylamide (NIPAM), along with the incorporation of natural galactomannan (GM), which forms hydrogen bonds as sacrificial bonds to build flexible and stretchable secondary cross-linked networks. The proposed double-network (DN) structure significantly enhances the mechanical strength of the material. The cooperation of DMAPAA and GM also conferred excellent adhesion and self-healing capabilities to the material, which could reach an adhesive strength of 23 kPa and a self-healing efficiency of 80%. Notably, the GM hydrogel can be stretched by 420%, with a corresponding stress of 53 kPa and an electrical conductivity measured at 0.2 S/m. As a result, biomimetic GM-induced DN hydrogels equipped with adhesion, self-healing and fatigue resistance were developed, which were applicable as flexible sensors and wearable electronic devices.