Self-repairing flexible strain sensors based on nanocomposite hydrogels for whole-body monitoring

Flexible strain sensors based on extensible hydrogels are extensively investigated for human motion monitoring, but the performances of such strain sensors are limited by failure or high residual strain of hydrogels. Herein, self-repairing flexible strain sensors are fabricated with poly(AA-co-SMA)/c-CNF/Fe3+ nanocomposite hydrogels (AA: acrylic acid, SMA: stearyl methacrylate, c-CNF: carboxylate modified cellulose nanofibril). Because the nanocomposite hydrogels are fully supramolecularly cross-linked by hydrophobic association and ionic interaction, the flexible strain sensors can repair themselves upon damage and recover their sensing ability. Compared with other hydrogel-based self-repairing sensors, the flexible strain sensors in this work have intrinsically reversible sensing ability based on the improved resilience of the nanocomposite hydrogel by introducing c-CNF. In addition, such sensors also have integrated large sensing range (0 similar to 800 %), low response time (0.25 s), high sensitivity (strain 0 similar to 300 %, gauge factor = 1.9; strain 400 %similar to 800 %, gauge factor = 4.4) and excellent durability (similar to 1000 cycles) for guaranteeing their potential applications in whole-body monitoring.