A Highly Tough and Strain-Sensitive MXene Hydrogel Sensor Enabling Integrated Wearable Electronics with Body Conformability and Real-Time Visualization

Hydrogel sensors are emerging as one promising device for wearable electronics by virtue of intrinsic flexibility and stimuli sensitivity. In particular, MXene hydrogel sensors possess superior properties of high sensitivity and wide strain sensing range, because MXene nanosheets have unique flake structure and metal-like electronic conductivity. However, the existing defects of aggregation and oxidation in MXene nanosheets would easily weaken the toughness and conductivity of hydrogel matrices, thus compromising the mechanical flexibility and strain sensitivity of hydrogel sensors. Here a class of MXene hydrogel sensors is proposed by in situ polymerization and non-covalent interactions. These hydrogel sensors exhibit high stretchability and high toughness simultaneously, reaching stretchability of 1100% and fracture energy of 5374 J m^-2. Meanwhile, the introduced catechol groups of dopamine-grafted carboxymethyl cellulose sodium （DA@CMC） endow the hydrogel sensor with excellent anti-oxidation, adhesion, and long-term conductivity, enabling this sensor to show desirable strain sensitivity with a fast response time of 102 ms and a wide sensing scope of 0-800% strain. Moreover, the integration of a strain-sensitive hydrogel sensor with a multicolor display demonstrates system-level applications for real-time visual motion monitoring. This work paves the way for the development of body-conformable monitoring devices, holding great potential in wearable electronics that require visual functionalities.