With growing interest in flexible and wearable devices, the demand for nature-inspired soft smart materials, especially intelligent hydrogels with multiple perceptions toward external strain and temperatures to mimic the human skin, is on the rise. However, simultaneous achievement of intelligent hydrogels with skin-compatible performances, including good transparency, appropriate mechanical properties, autonomous self-healing ability, multiple mechanical/ thermoresponsiveness, and retaining flexibility at subzero temperatures, is still challenging and thus limits their application as skinlike devices.Here, conductive nanocomposite hydrogels (NC gels) were delicately designed and prepared via gelation of oligo(ethylene glycol) methacrylate (OEGMA)-based monomers in a glycerol−water cosolvent, where inorganic clay served as the physical cross-linker and provided conductive ions. The resultant NC gels exhibited good conductivity (∼3.32 × 10 −4 S cm −1 , akin to biological muscle tissue) and an autonomously self-healing capacity (healing efficiency reached 84.8%). Additionally, such NC gels displayed excellent flexibility and responded well to multiple strain/temperature external stimuli and subtle human motions in a wide temperature range (from −20 to 45 °C). These distinguished properties would endow such NC gels significant applications in fields of biosensors, human−machine interfaces, and soft robotics.

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The advocacy of smart living results in a high demand for wearable and flexible sensors to monitor human motions. Among these, sensors based on strain−optics conversion are attractive due to their inherent electrical safety and electromagnetic immunity in comparison to strain−electricity conversion sensors. Particularly, hydrogel-based optical fiber sensors are biocompatible, flexible, and stretchable and thus are potentially applicable to health monitoring, human−machine intelligence, and soft robots. Nonetheless, hydrogelbased optical fibers still demonstrate challenges such as limited stretch ratios from chemical cross-linking networks and insufficient light transmittance from dehydration or nucleation of water. Herein, flexible and stretchable strain sensors based on glycerol-introducing nanocomposite hydrogel fibers (GN-Fibers) were achieved via dynamic stretching of a reactive pregel from monomer/nanoparticle hybrid precursors in a glycerol−water cosolvent. The resultant GN-Fibers evolved with anisotropic microstructures, displaying excellent tensile strength (9.76 MPa), high elastic modulus (32.63 MPa), low light propagation attenuation (0.26 dB cm −1 ), and broad strain range. Owing to the use of glycerol−water, such GN-Fibers also exhibited long-term moisture-retaining and antifreezing properties. In addition, GN-Fibers functioned well as sensors based on strain−optics conversion to monitor stretching and compressing behaviors. It is believed that such an optical fiber based strain sensor is a gateway to fabrication of next-generation wearable and flexible devices for health monitoring or artificial intelligence.

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