Scaffold-microenvironment decoupling opens new path for chitosan hydrogels in flexible electronics

A study published in the Journal of Bioresources and Bioproducts presents a breakthrough design paradigm for chitosan-based conductive hydrogels aimed at sustainable flexible electronics. The research team introduced a scaffold-microenvironment decoupling approach that constructs a hierarchically tough yet open polymer scaffold while independently programming the internal aqueous phase into a highly conductive and cryo-tolerant microenvironment through tailored ion hydration and salting-out. The resulting hydrogel, designated WCPBH-Li, was fabricated using wood vinegar as a biomass-derived green medium to dissolve and functionalize chitosan, combined with polyvinyl alcohol, boric acid, and lithium chloride treatment. The material exhibited integrated properties including high mechanical strength with tensile strains up to 500%, ultra-high ionic conductivity of 68.6 mS/cm at room temperature and 14.85 mS/cm at –20°C, and a freezing point below –85°C. The hydrogel also demonstrated inherent antibacterial, antioxidant, and biocompatible properties derived from wood vinegar phenolics. Its practical efficacy was validated across three demanding electronic applications: serving as an ultra-stable gel electrolyte for flexible supercapacitors with over 10,000-cycle durability, functioning as a high-fidelity wearable strain sensor for physiological signal monitoring and gesture-based encrypted communication, and operating as an effective component in triboelectric nanogenerators for mechanical energy harvesting.
Chitosan, a cationic polysaccharide derived from chitin, has long been regarded as a promising building block for sustainable electronics due to its renewability, biodegradability, and biocompatibility. However, conventional approaches face a persistent materials dilemma: enhancing mechanical integrity through crosslinking or crystallization inevitably sacrifices ionic mobility and environmental stability, leading to poor conductivity and dehydration susceptibility. The new strategy overcomes this trade-off by first constructing a robust scaffold through freeze-thaw cycling and dynamic borate ester cross-links, then engineering the internal microenvironment via concentrated LiCl immersion. This salting-out treatment triggers polymer chain aggregation while creating a percolating ionic pathway, with strongly hydrated ions reorganizing water states to suppress ice formation. The research demonstrated that the hydrogel maintains stable electrochemical performance under bending, compression, and load-bearing conditions, and can be assembled in series or parallel configurations. The work establishes an innovative design route for next-generation sustainable soft materials where traditionally conflicting properties can be harmoniously integrated without relying on expensive ionic liquids or complex multi-step synthesis.