Extraction and incorporation of cellulose microfibers from textile wastes into MXene-enhanced PVA-borax hydrogel for multifunctional wearable sensors.

Conductive hydrogel has drawn great concern in wearable sensors, human-machine interfaces, artificial intelligence (AI), health monitoring, et al. But it still remains challenge to develop hydrogel through facile and sustainable methods. In this work, a conductive, flexible, bendable and self-healing hydrogel (PBCM) composed of polyvinyl alcohol (PVA), borax, cellulose microfibers (CMFs) and MXene nanosheets was fabricated by a simple and efficient strategy. The carboxylated CMFs were extracted from waste ramie fibers via a one-pot ammonium persulfate oxidation method. The crystallinity and tensile strength were increased 70 % and 4 times due to the addition of CMFs and MXene compared to the pristine PVA-borax hydrogel. The incorporation of MXene nanosheets acts as multifunctional cross-linkers and energy transfer platform, promoting the electrical conductivity, stretchability and bendability of hydrogel remarkably. The PBCM-2 hydrogel exhibited the maximum electrical conductivity of 0.81 S/cm. Additionally, the dynamic borate ester linkage imparts self-healing ability to the hydrogel. The resulting PBCM-2 hydrogel demonstrated excellent resistance to fire and pH response properties. Moreover, it showed sensitivity in monitoring various human physiological movements, including finger, wrist, elbow, knee bending and drinking water, indicating its potential for wearable sensing applications like health care and sports training.