Fiber-reinforced tough and ultrathin composite hydrogel interfaces for advanced human-machine interaction.

Hydrogels have emerged as transformative materials in human-machine interfaces due to its similarity to natural biological tissues. However, existing hydrogels generally suffer from inherent drawbacks such as low mechanical strength, insufficient conformability, and poor environmental tolerance, which severely limit long-term, reliable, and seamless interactions between humans and machines. In this study, a synergistic strategy of fiber reinforcement and solvent displacement is employed to develop an ultrathin, tough, anti-freezing, and anti-dehydration composite hydrogel interface. Benefiting from the efficient energy dissipation and stress transfer mechanisms of the styrene ethylene butylene styrene/polyurethane (SEBS/PU) composite fibers, the resulting 20 μm ultrathin hydrogel exhibits exceptional mechanical properties, with a fracture elongation of 676.7 %, toughness of 2.78 MJ m, and Young's modulus of 544.7 kPa, enabling conformal interfacing with multiple human skin regions. Furthermore, the glycerol/water binary solvent system, through hydrogen bonding with water molecules, imparts the hydrogel with excellent anti-freezing and anti-dehydration properties. Notably, epidermal electrodes designed from this hydrogel achieve seamless integration with human skin, enabling long-term, high-fidelity (31.41 dB) electrophysiological signal monitoring, demonstrating significant potential for applications in wearable health monitoring, medical diagnostics, and augmented reality systems.