Interfacially engineered MXene hydrogels with dual-conductive networks for high-performance multifunctional sensing via a green and sustainable strategy

Abstract

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 antifreeze agents that compromise mechanical integrity. Herein, we report a green and efficient strategy for fabricating a multifunctional polyacrylamide/polyvinyl alcohol/CaCl₂/AgNP/proanthocyanidin/MXene (PPCAPM) composite hydrogel using natural proanthocyanidins (PAs) as a multifunctional green mediator. Molecular dynamics simulations reveal that PAs enhance interlayer electrostatic repulsion between MXene nanosheets, effectively suppressing van der Waals-driven restacking and increasing the diffusion coefficient by 48%. Notably, PAs and MXenes 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) through a colligative freezing-point depression mechanism, thereby eliminating the need for environmentally harmful organic antifreeze agents. The resulting hydrogel exhibits autonomous moisture retention, high conductivity (1.84 S m⁻¹), 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 next-generation wearable diagnostics and human–machine interfaces operable under harsh conditions.