image: (a) Schematic diagram of the freeze-thaw assisted wet annealing synthesis strategy for tough, recyclable and bio-friendly IL/PVA hydrogels. (i) PVA/H2O homogeneous solution with disordered pre-dispersed network. ii) Crosslinking of PVA with BMIMBF4 to form IL/PVA hydrogels precursor. iii) Wet annealing to adjust macromolecular conformation in precursors. iv) IL/PVA hydrogels with high macromolecular entanglement and crystallinity obtained by cyclic freeze-thaw strategy (PVA: polyvinyl alcohol; BMIMBF4: 1-butyl-3-methylimidazolium tetrafluoroborate). Photographs show the state of the hydrogels during their formation. (b) Photograph of PIWF3 hydrogel under heating and freezing states. Scale bar, 1cm. (c) Photographs demonstrating the mechanical robustness of IL/PVA hydrogels and their ability to suspend 2.5 kg of water. Scale bar, 1 cm. (d) Tensile stress-strain curves of PHF1, PIWFx and recycled IL/PVA hydrogels. (e) Elastic modulus and toughness of PHF1 hydrogel, PIWF1, PIWF3 and recycled hydrogels calculated from (d). Error bars represent the SD of the measured values (n = 3). (f) Strength comparison of PIWF3 hydrogel (solid pentagram) and recycled IL/PVA hydrogel (hollow pentagram) with representative IL-based, organic/inorganic filler PVA hydrogels.
Credit: ©Science China Press
Background：
Soft electronics have gained significant attention due to their lightweight, mechanical flexibility, and biocompatibility, making them ideal for applications such as health monitoring, human-machine interfaces, and augmented reality/virtual reality communications. However, challenges remain in simultaneously achieving high mechanical performance, electrical conductivity, and environmental sustainability in ionic liquid-based conductive hydrogels. While ILs possess unique properties such as high ionic conductivity, non-volatility, and thermal stability, existing hydrogel preparation methods often struggle to balance toughness and conductivity with biocompatibility and recyclability. To address these issues, this study introduces a novel ionic liquid/polyvinyl alcohol conductive hydrogel that leverages a combination of wet annealing and freeze-thaw strategies. By optimizing the preparation process and material design, the developed hydrogel achieves exceptional mechanical performance, electrical conductivity, and environmental friendliness, offering a promising solution for flexible and sustainable electronics.
Conclusion：
This study presents a highly tough and multifunctional ionic liquid/polyvinyl alcohol conductive hydrogel with outstanding mechanical properties, electrical conductivity, and environmental sustainability. Through the synergistic combination of wet annealing and freeze-thaw strategies, the hydrogel exhibits exceptional tensile strength, elongation at break, toughness, and electrical conductivity. The ionic liquid/polyvinyl alcohol hydrogel demonstrates excellent stability under repeated mechanical deformation and can be recycled without significant loss of performance, reducing electronic waste and enhancing its eco-friendly profile. Furthermore, the prepared hydrogel exhibits excellent antibacterial properties and multifunctional applications, including use in strain sensors and supercapacitors. These features highlight its potential for flexible electronic devices and wearable technologies. By balancing mechanical strength, conductivity, and biocompatibility, this work advances the design of green and sustainable soft electronic materials, paving the way for future innovations in flexible electronics.