Closed-Loop Recyclable Anti-Swelling PVA/AgNWs Hydrogels for Sustainable Flexible Electronics

Hydrogel flexible sensors have demonstrated significant potential in human motion and health monitoring applications; however, their practical implementation is constrained by poor anti-swelling performance and limited recyclability. In this study, a gradient assembly strategy combining freeze-thaw, salting-out, and swelling (FSS) was developed to fabricate an anti-swelling PVA/AgNWs hydrogel with closed-loop recyclability. This synergistic phase separation approach enables simultaneous optimization of mechanical properties, electrical conductivity, and anti-swelling performance. Relative to control hydrogels undergoing solely freeze-thaw cycles, the FSS-processed PVA/AgNWs hydrogel exhibited a 61-fold increase in bulk toughness (from 0.031 MJ/m 3 to 1.9 MJ/m 3 ) and a 6-fold enhancement in conductivity (from 0.041 S/m to 0.25 S/m). Moreover, after 15 days of water immersion, the hydrogel maintained exceptional stability: mass change remained below 5%, while tensile strain, bulk toughness, and electrical conductivity exhibited over 95% retention after both 7 and 15 days. Leveraging the physical nature of cross‑links (hydrogen bonds and crystals), we established a complete closed-loop recycling system. After three cycles of recycling, the hydrogel retained 95% tensile strain, preserved 91.52% of the original tensile stress, and maintained 97.71% of the initial conductivity. Additionally, the hydrogel exhibited excellent biocompatibility and antibacterial properties. Sensors based on this hydrogel achieved underwater biomimetic motion monitoring, while biological electrodes performed comparably to commercial Ag/AgCl electrodes in human physiological signal acquisition. The green, low-cost, sustainable gradient assembly strategy provides a universal methodology for balancing mechanical robustness, electrical conductivity, and environmental adaptability in next-generation wearable electronics, thereby advancing technological breakthroughs and industrial upgrades in sustainable flexible electronics.