Lignosulfonate sodium and ionic liquid synergistically promote tough hydrogels for intelligent wearable human-machine interaction

Flexible wearable devices are garnering significant interest, with conductive hydrogels emerging as a particularly notable category. While many of these hydrogels offer impressive conductivity, they often lack the innate ability to adhere autonomously to human skin. The ideal hydrogel should possess both superior adhesion properties and a wide responsive range. This study introduces a novel double-network conductive hydrogel, synthesized from lignosulfonate sodium and ionic liquid using a one-pot method. The gel's mechanical robustness (fracture elongation of ∼3500 % and tensile strength of ∼130 kPa) and exceptional conductivity sensing performance arise from the synergistic effects of electrostatic interactions, dynamic hydrogen bonding, and a three-dimensional network structure. Additionally, the phenolic hydroxyl and sulfonic groups from lignosulfonate sodium imbue the hydrogel with adhesive qualities, allowing it to easily bond with varied material surfaces. This hydrogel excels in human physiological signal detection and wireless monitoring, demonstrating a rapid response time (149 ms) and high sensitivity (a maximum gauge factor of 10.9 for strains between 400 and 600 %). Given these properties, the flexible, self-adhesive, and conductive hydrogel showcases immense promise for future applications in wearable devices and wireless transmission sensing.