Polydopamine-modified MXene toward anti-freezing and self-healing hydrogel flexible sensors

MXene and its modified derivatives exhibit exceptional properties, including outstanding mechanical performance, high electrical conductivity, hydrophilicity, and tunable surface structures, attributable to their unique composition and structure. These characteristics render them highly effective as filler materials within hydrogels. In this study, polydopamine (PDA) was employed to protect MXene against oxidation while simultaneously endowing the hydrogel with adhesion properties. The resulting MXene@PDA is uniformly dispersed within the hydrogel's three-dimensional network, establishing efficient electron transport pathways that confer excellent electrical conductivity to the hydrogel. The hydrogel matrix, composed of xanthan gum (XG) and polyacrylic acid (PAA), was crosslinked and endowed with antifreezing capabilities using phytic acid (PA). Surface-bound hydroxyl (-OH) groups on MXene@PDA dynamically crosslink with the polymer matrix through hydrogen bonding. This synergistic interaction significantly enhances the hydrogel's self-healing efficiency (84.3 %), mechanical strength (1.21 MPa), and stretchability (1180 % strain). The resulting flexible sensor accurately detects and responds to motion signals even at sub-zero temperatures as low as −15 °C, demonstrating exceptional sensitivity and stability. This work establishes a robust methodology for fabricating multifunctional MXene-based composite hydrogel sensors integrating anti-freezing, self-healing, high conductivity, and flexibility.