Highly Stretchable and Self-Healable MXene/Polyvinyl Alcohol Hydrogel Electrode for Wearable Capacitive Electronic Skin

Capacitive strain sensors could become an important component of electronic skin (E-skin) due to their low hysteresis and high linearity. However, to fully mimic the functionality of human skin, a capacitive strain sensor should be stretchable and self-healable. The development of such a sensor is limited by electrode materials which generally lack self-healability and/or stretchability. A highly stretchable and self-healing MXene (Ti₃C₂T_x)/polyvinyl alcohol (PVA) hydrogel electrode is developed for use in capacitive strain sensors for E-skin. The incorporation of MXene into the PVA enhances the conductivity and self-healability of the hydrogel. The electrode exhibits high stretchability at break (≈1200%) and instantaneous self healing (healing time ≈ 0.15 s). A capacitive sensor based on these electrodes shows high linearity, up to 200%, low hysteresis, a sensitivity of ≈0.40, and good mechanical durability (a 5.8% reduction in relative capacitance change after 10 000 cycles). Moreover, this sensor maintains its performance after a self-healing test, proving its potential for the monitoring of human motion.