Hemicellulose-lignin complex reinforcing deep eutectic solvent gels for wearable strain sensing and fire warning monitoring

With the rapid development of new electronic technologies, flexible electronic devices based on conductive gels have emerged and are widely used in wearable electronic devices, electronic skins, electronic fabrics and other fields. However, traditional deep eutectic solvent polymer (PDES) gels face many problems in terms of mechanical strength and conductive properties. In this study, hemicellulose-lignin complex (HLC) extracted from straw was used as a physical cross-linker (additive) to prepare polymethacryloxyethyltrimethyl ammonium chloride-Glycerol (PDMC-Gly) gel. With the addition of 2 wt% HLC, the tensile strength and elastic modulus of HLC/PDMC-Gly gel were 846.2 kPa and 290.0 kPa respectively, both of which were significantly higher than pure PDMC-Gly gel. The introduced HLC with lignin benzene ring structure units gave the gel excellent light transmittance and ultraviolet blocking properties. In addition, the incorporation of HLC reconstructed the hydrogen bonding network within the gel, resulting in the release of free Cl⁻ ions. Consequently, the ionic conductivity of gels was significantly enhanced, reaching of 1.61 × 10³ mS/cm. This gel has excellent sensing sensitivity, humidity responsiveness and thermal stability, and has potential application prospects in the fields of real-time human body detection, environmental detection and fire early warning.