Lignin-coated liquid metals-induced synthesis of deep eutectic solvent-based hydrogels with environmentally tolerant for strain sensors

In the work, alkali lignin (AL) was used as a coating layer for dispersing liquid metals (LM) in a ternary DES (choline chloride/ethylene glycol/water) system and generating free radical-catalyzed acrylic acid (AA) polymerization. The preparation of flexible sensors had high electrical conductivity (0.33 S<middle dot>m(-1)), excellent self-healing and mechanical properties (84.7 KPa). The presence of AL facilitated the dispersion of LM in the DES system and the formation of a flexible hydrogel without the addition of an initiator. Moreover, DES was used as the liquid component of the PAA-AL(2)@LM2 hydrogel made it more environmentally tolerant and had better water retention. Even at -20 degrees C, the hydrogel exhibited low electrical resistance (131.4 Omega). The moisture loss of the prepared hydrogel was only 9 % after 7 days at room temperature. This work exploited the significant advantages of DES and lignin-based materials in dispersing LM to provide a new technique for the preparation of metal-polymer composite hydrogels, which has great potential in the field of flexible sensors.