A self-healing and wearable hydrogel sensor with a dynamic physical cross-linking structure can detect strain stimulus in a wide temperature range

Traditional hydrogel sensors can easily freeze or evaporate under extreme conditions, resulting in their performance degradation. At the same time, the low strength/toughness and high resistance of hydrogels hinder their practical applications in different fields. In this work, we report a simple and effective strategy to prepare mechanically strong and conductive nanocomposite hydrogels by covalent interaction of acidified carbon fibers and various ions. In this paper, a wearable strain sensor with high sensitivity and flexibility and self-healing, anti-freezing and anti-drying properties was prepared using polyacrylic acid, sodium alginate and acidified carbon fibers as raw materials. The hydrogel has an interpenetrating cross-linked network structure. The interpenetrating cross-linking structure makes the hydrogel sensor exhibit excellent ductility, remarkable repeatability and stable sensing performance. The hydrogel can be used as a human strain sensor for the real-time detection of human movement, including joint movement and speech. The hydrogel strain sensor shows low strain detection limit (3% strain), fast response time (∼100 ms), high sensitivity factor and excellent stability. The hydrogel has good self-adhesion with various substrates (such as copper, glass, plastic and skin). The hydrogel has good strain sensing performance at different strains (1–200%). In addition, the hydrogel can maintain excellent flexibility, extensibility and conductivity in a wide temperature range from −20 °C to 50 °C, effectively improving the practicability and durability of the hydrogel in practical applications. Therefore, the hydrogel has a good application prospect in wearable devices, soft robot systems and health monitoring applications.