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

[Display omitted] •Carboxylate modified cellulose nanofibril efficiently improved the strength and resilience of supramolecularly cross-linked hydrogels.•Self-repairing flexible strain sensors possessing integrated high performances were fabricated based on the composite hydrogels.•Whole-body motion and physiological activity monitoring were achieved utilizing the flexible strain sensors. 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∼800 %), low response time (0.25 s), high sensitivity (strain 0∼300 %, gauge factor = 1.9; strain 400 %∼800 %, gauge factor = 4.4) and excellent durability (∼1000 cycles) for guaranteeing their potential applications in whole-body monitoring.