Self-healing and toughness cellulose nanocrystals nanocomposite hydrogels for strain-sensitive wearable flexible sensor

Recently, self-healing and high mechanical strength hydrogels have aroused much research due to their potential future in strain-sensitive flexible sensors. In this manuscript, we successfully designed self-healing and toughness cellulose nanocrystals (CNCs) nanocomposite hydrogels by grafted polypyrrole (PPy) on the surface of CNCs to enhance electrical conductivity. The obtained nanocomposite hydrogels exhibit outstanding self-healing and mechanical behaviors, and the optimal mechanical strength, toughness and self-healing efficiency can be up to 5.7 MPa, 810% and 89.6%, respectively. Using these functional nanocomposite hydrogels, strain-sensitive wearable flexible sensors were designed to monitor finger joint motions, bending of knee, and even the slight pulse beating. Surprisingly, the flexible sensors could evidently perceive body motions from large movements (knee bending) to tiny signals (pulse beating). In addition, it exhibited excellent durability after repeated cycles. This method of prepared self-healing nanocomposite hydrogels will have a potential prospect in the design of biomedical, biosensors, and flexible electronic devices.