Skin-inspired MXene-based polyvinyl alcohol/gelatin organic hydrogel with good anti-drying, anti-swelling properties and high sensitivity

Hydrogel-based flexible sensors have recently attracted considerable attention in the field of wearable soft electronics. However, hydrogel-based flexible devices often fail to operate underwater because of their poor stability during swelling. Moreover, it is difficult for conventional conductive hydrogels to simultaneously achieve the desirable mechanical properties, high electrical conductivity, and satisfactory sensitivity to multiple stimuli. To implement a hydrogel-based sensor with high long-term stability, swelling resistance, and multifunctional capability, a fully physically crosslinked MXene-supported polyvinyl alcohol/gelatin dual-network organic hydrogel enhanced by tannic acid (PGTM) was proposed in this study. The unique properties of this hydrogel were inspired by the human skin structure and well-dispersed MXene nanosheets, which endow it with a wide strain range (0.01-400 %), high electrical conductivity (1.4 S m-1), and high sensitivity (gauge factor: 3.15). In addition, PGTM exhibited good biocompatibility, moisturizing, anti-swelling, self-recovery properties, and relative low contact impedance (17.18 +/- 0.93 k Omega at 10 Hz), which enable its electronic skin applications with the ability to detect various electrophysiological signals and monitor human movements underwater. The proposed organic hydrogel can be potentially used in human-machine interactions for multi-application scenarios and personalized multi-signal monitoring.