Ultra-Robust Conductive Hydrogels Enabled by a Gradient Bond-Breaking Pseudo-Drying Strategy

Hydrogels, hydrophilic polymer networks mimicking biological tissues, hold great potential in biomedical applications such as electronic skin, tissue engineering, and biosensors. However, conventional hydrogels often struggle to concurrently achieve high strength, modulus, toughness, and fracture resistance, while dehydration and low-temperature crystallization further limit their utility. Here, a biomimetic gradient bond-breaking strategy is proposed to address these challenges. By constructing a hydrogel with covalently crosslinked hierarchical reinforcing phases-crystalline domains and self-assembled aramid nanofibers (ANFs) networks-within the aqueous-poor phase, preferential covalent bond rupture is enabled to enhance modulus, while hydrogen bond-rich nanocrystalline domains and ANFs networks synergistically improve toughness. This mechanism yields fracture-resistant properties akin to dry-state materials, achieving a modulus of 12.4 MPa, toughness of 73.66 MJ m^{- 3}, and fracture toughness of 268.8 kJ m^{- 2} at 70% water content-surpassing all reported PVA-based hydrogels and even natural structural materials like tendon and spider silk. The mechanical properties are tunable via fabrication parameters, and the hydrogel exhibits broad-temperature stability, high conductivity, and cytocompatibility. Leveraging these attributes, a low-temperature-operable strain sensor is developed for real-time, accurate monitoring of human motion. This work advances the design of hydrogels with exceptional mechanical and functional properties for flexible electronics.