Interfacially Engineered MXene Hydrogel with Dual-Conductive Networks for High-Performance Multifunctional Sensing via a Green and Sustainable Strategy

The development of high-performance conductive hydrogels through green and sustainable strategies remains a pivotal challenge in flexible electronics. Conventional methods often rely on toxic crosslinkers, energy-intensive processes, or excessive metal ions, limiting their environmental compatibility and scalability. Furthermore, susceptibility to freezing at sub-zero temperatures poses a major obstacle for their use in extreme climates, typically addressed by organic antifreezes that compromise mechanical integrity. Herein, we report a green and efficient strategy for fabricating a multifunctional polyacrylamide/polyvinyl alcohol/CaCl₂/AgNPs/proanthocyanidins/MXene (PPCAPM) composite hydrogel using natural proanthocyanidins (PA) as a multifunctional green mediator. Molecular dynamics simulations reveal that PA enhances interlayer electrostatic repulsion between MXene nanosheets, effectively suppressing van der Waals-driven restacking and increasing the diffusion coefficient by 48%. Notably, PA and MXene synergistically catalyze the in-situ reduction of AgNPs at ultralow Ag⁺ concentrations, avoiding the use of conventional toxic reductants. Crucially, the incorporation of CaCl₂ serves as a green and potent antifreeze, enabling exceptional cryoresistance (-40 °C) by significantly lowing the freezing-point of the solution, thereby eliminating the need for environmentally harmful organic antifreeze agents. The resulting hydrogel exhibits autonomous moisture retention, high conductivity (1.84 S/m), excellent impact factor (GF=3.73), and intrinsic adhesion, enabling high-fidelity monitoring of both large-scale joint movements and subtle physiological signals such as EMG and ECG. This work demonstrates a green and sustainable paradigm for designing multifunctional hydrogel sensors via natural polyphenol-mediated interfacial engineering and ion-regulated antifreezing, offering a promising platform for nextgeneration wearable diagnostics and human-machine interfaces operable under harsh conditions.