Highly sensitive and wearable gel-based sensors with a dynamic physically cross-linked structure for strain-stimulus detection over a wide temperature range

Abstract

Traditional hydrogel sensors can only be applicable in a limited temperature range, such as ambient temperature, since water is easily frozen or evaporated under extreme conditions, which seriously affects their practical application. Here, a highly sensitive wearable strain sensor is fabricated from a flexible, self-healing, anti-freezing and anti-drying gel with a physical cross-linking structure, which is composed of polyacrylic acid, chitosan, and graphene oxide in a mixed solvent of water and glycerol. The dynamic cross-linking enables the network structure and ion channels of the gel to be rapidly recovered and reconstituted, thereby allowing the gel-based strain sensor to display excellent stretchability (more than 1000%) and outstanding sensing performance with a rapid response time of 40 ms, and remarkable repeatability and stability. As a result, the gel can be applied as an epidermal strain sensor for real-time detection of human motions, including joint motions, speaking and breathing. Moreover, the gel can maintain excellent flexibility, stretchability and conductivity over a wide temperature range from −20 °C to 70 °C, which effectively improves the practicality and durability of the gel in practical applications. Therefore, such flexible, conductive, anti-freezing and anti-drying gel may have promising applications in the field of wearable devices, soft robot systems and other applications that need to be applied under changeable conditions.