Fully Physically Cross-Linked, Highly Sensitive, and Nanofiber-Reinforced MXene Conductive Hydrogels for Flexible Wearable Sensors

Conductive hydrogels have great potential as flexible sensors in wearable devices. However, it remains a challenge to integrate excellent mechanical properties, high conductivity, and sensitivity into hydrogels using simple green methods. Here, cellulose nanofibers (CNFs) and MXene were introduced into a polyvinyl alcohol (PVA) hydrogel system based on the multi-scale synergistic enhancement mechanism of nanocomposites. By forming interfacial hydrogen bonds and entanglement of molecular chains, a nanofiber-reinforced PVA/CNF/MXene (PCM) hydrogel was developed. MXene enhances the electrical conductivity of the hydrogel, reaching 0.175 S/m, which represents a 191.7% increase compared to the hydrogel without MXene. The synergistic enhancement between CNF and MXene confers the PCM hydrogel with high mechanical strength (334 kPa) and high stretchability (339%). Moreover, PCM hydrogel serves as a strain sensor with outstanding strain sensitivity (GF = 3.25), wide dynamic detection range (0%–220%), and low detection threshold (0.3%), demonstrating excellent stability and durability in response to stimulus signals. The hydrogel sensor enables accurate detection of subtle human movements and synchronized control of robotic arms, demonstrating its broad applicability in motion monitoring and human–machine interaction (HMI).