MXene-Enhanced Hydrogels for Wearable Strain Sensors and Triboelectric Human–Machine Interfaces

Flexible sensors have become indispensable components of wearable electronics and real-time health-monitoring systems. Conductive hydrogels, owing to their synergistic mechanical-electrical properties, are emerging as ideal candidate materials. In this study, a covalently cross-linked network was constructed via esterification between poly(vinyl alcohol) (PVA) and acrylic acid (AAc), and ethylene glycol (EG) was introduced to form hydrogen bonds with the network, enhancing mechanical strength and freeze resistance. MXene nanosheets were incorporated to form hydrogen bonds between their surface functional groups and the polymer chains, enabling reversible physical cross-linking. This strategy simultaneously provides mechanical reinforcement and establishes a 3D conductive superporous network, yielding PVA-AAc-EG-MXene (PAEM) hydrogels. The resulting hydrogel exhibits outstanding mechanical and electrical performance with tensile strain >700%, a maximum tensile stress of 620 kPa, and a gauge factor of 2.2, while both response and recovery times are as short as 100 ms. Based on the PA 0.3 EM 0.8 hydrogel, strain sensors were fabricated to precisely capture facial microexpressions and joint motion signals, and triboelectric nanogenerator (TENG) sensors were constructed and integrated with circuit systems to achieve human–machine interaction, thereby demonstrating its potential as a versatile material for next-generation wearable electronics.