Environmentally stable, mechanically flexible, self-adhesive, and electrically conductive Ti3C2TX MXene hydrogels for wide-temperature strain sensing

Conductive hydrogels are promising in the flexible wearable electronic applications due to their unique feature of intrinsic stretchability, reversible flexibility, and high electrical conductivity. However, severely poor adaptability under cold or hot environmental conditions along with inferior adhesiveness to various substrates greatly hinders the potential applications in such emerging field. Herein, we describe a mechanically flexible and electrically conductive nanocomposite hydrogel composed of polyacrylamide-co-acrylic acid/chitosan covalent-network reinforced by Ti3C2Tx MXene nanosheets within water-glycerol binary solvent via a simple one-pot free radical polymerization. Notably, incorporation of a low content (0.1-0.3 wt%) of MXene promotes the rapid gelation of the polymer molecules in only 10 min. The optimized hydrogel containing 0.2 wt% MXene not only possesses excellent mechanical performance (e.g., tensile elongation of similar to 1000%) and improved electrical conductivity (similar to 1.34 S/m), but also shows stable temperature tolerance from - 20 to 80 degrees C and self-adhesion with various substrates (e.g., steel, glass, rubber, plastics and skin) as well as a rapid self-healable feature (similar to 1.3 s). Further, such hybrid MXene hydrogel exhibits dual sensations under different strain (1-600%) and stress (80-3200 Pa) ranges, good applicability for various deformation conditions (tension/bend/compression), and wide temperature adoptability with stable repeatability. Clearly, this versatile MXene nanocomposite hydrogel developed may provide a new route for the rational design and development of advanced skin-like sensor for complex environmental application.