Environment-Tolerant and Ultra-Tough Hydrogel for Wearable Strain Sensors in Human Motion Monitoring

In this study, we developed a novel environment-tolerant ultra-tough hydrogel-based flexible sensing material through a photopolymerization cross-linking strategy combining metal ion coordination bonds, the Hofmeister effect, and solvent exchange. The resulting poly(vinyl alcohol)/acrylic acid/zirconium oxychloride/gelatin/glycerol (PAZrGG) hydrogel exhibited an outstanding tensile strength of 12.77 MPa, elongation at break of 476.05%, toughness of 39.69 MJ/m³, compressive strength of 23.78 MPa, and electrical conductivity of 0.36 S/m. Furthermore, the PAZrGG hydrogel displayed superior moisture retention, antiswelling behavior, as well as freeze resistance and high-temperature stability. Additionally, the PAZrGG hydrogel-based sensor exhibited good linear response over a wide strain range (0-80% tensile strain, 5-50% compression), excellent cyclic stability (>1000 cycles), and rapid dynamic response (∼250 ms). Additionally, the sensor provided real-time, high-precision monitoring of diverse human joint movements, ranging from finger and wrist motions to elbow and knee movements. This study provides a new and effective strategy for designing high-performance tough hydrogels, paving the way for next-generation flexible electronics and wearable sensing technologies.