Demethylated Lignin@Liquid Metal Nanospheres Enabling Versatile Conductive Hydrogel for Self-Powered Soft Electronics

Conductive hydrogels have become highly attractive in smart, soft electronics. However, it remains a substantial challenge to employ a low-cost and fast gelation technique to proceed with the effective function integration of conductive hydrogels with superior mechanical robustness, high adhesiveness, and impressive self-healable properties. Herein, a versatile biomass-based hydrogel (DLLMH) was synthesized with built-in demethylated lignin (DL) coated liquid metal (LM) (DL@LM) nanospheres to promote polymerization, yielding excellent mechanical (3.77 MJ/m3), exceptional conductivity (2.14 mS/cm), outstanding adhesion (36.47 MPa), and desired self-healing ability. Notably, the LM could significantly accelerate the initiation of free-radical polymerization (280 s) without heating and UV irradiation, while DL acts as a stabilizing agent to prevent hydrogel overpolymerization and inhibit the occurrence of LM precipitation. Meanwhile, the assembled DL@LM also aimed at isotropic extension deformation and multiple interactions within the DLLMH matrix, which greatly conferred its efficient energy dissipation. Considering extraordinary flexibility and conductivity, DLLMH could be assembled as the multimodular sensing paradigm toward strain and temperature. As-a-proof-of-concept, a single-electrode triboelectric nanogenerator (TENG) was constructed for self-powered mechanical energy harvesting and conversion and served as touch panels of the TENG array in a self-powered calculator for applications of human–computer interaction. This work will enrich the exploration of green chemistry and value-added utilization of lignin, providing a sustainable avenue for the untapped potential in design and application of hydrogel-based soft electronics.