High-strength self-healing multi-functional hydrogels with worm-like surface through hydrothermal-freeze-thaw method

Soft self-healing materials are promising candidates for flexible electronic devices due to their exceptional compatibility, extensibility, and self-restorability. Generally, these materials suffer from low tensile strength and susceptibility to fracture because of the restricted microstructure design. Herein, we propose a hydrothermal-freeze-thaw method to construct high-strength self-healing hydrogels with even interconnected networks and distinctive wrinkled surfaces. The integration of the wrinkled outer surface with the three-dimensional internal network confers the self-healing hydrogel with enhanced mechanical strength. This hydrogel achieves a tensile strength of 223 kPa, a breaking elongation of 442%, an adhesion strength of 57.6 kPa, and an adhesion energy of 237.2 J m^-2. Meanwhile, the hydrogel demonstrates impressive self-repair capability (repair efficiency: 93%). Moreover, the density functional theory (DFT) calculations are used to substantiate the stable existence of hydrogen bonding between the PPPBG hydrogel and water molecules which ensures the durability of the PPPBG hydrogel for long-term application. The measurements demonstrate that this multifunctional hydrogel possesses the requisite sensitivity and durability to serve as a strain sensor, which monitors a spectrum of motion signals including subtle vocalizations, pronounced facial expressions, and limb articulations. This work presents a viable strategy for healthcare monitoring, soft robotics, and interactive electronic skins.