Autonomously self-healing and elastic hydrogel sensor with long-chain colloidal scaffold

Physical hydrogels, hydrophilic polymer networks with reversible crosslinks, have drawn attention in cutting-edge applications due to high tunability and biocompatibility. The self-healing capability and elasticity are crucial to ensure the robustness and lifespan of the hydrogel, but achieving these exclusive properties remains challenging. Herein, fully self-healable and elastic hydrogel is achieved through long-chain polyacrylic acid (PAA) scaffold and follow-up polymerization of polyacrylamide (PAM). PAA, with the molecular weight of 240,000 self-entangles into interconnecting nanofibers above colloidal concentration, simultaneously providing reversibility and holding surrounding entangled PAM chains. The resultant hydrogel has 100 % healing capability within 5 h at room temperature and retains over 86 % of toughness and near 100 % of elastic recovery during cyclic loading, which is unprecedented in previous literature. This physical hydrogel also shows a wide detection range of 1200 % and highly stable electrical response over 3000 successive loading cycles at 100 % strain. Such strategy to utilize long-chain colloidal scaffold sheds the light in the modulation of hydrogel microstructure and broadens the versatility in applications.