Lignosulfonate-enhanced dispersion and compatibility of liquid metal nanodroplets in PVA hydrogel for improved self-recovery and fatigue resistance in wearable sensors

Stretchable and resilient conductive hydrogels, incorporating flowable liquid metals (LM) into polyvinyl alcohol (PVA), have emerged as promising materials for wearable sensors due to their exceptional mechanical properties and sustainability. However, the fluidity and compatibility of LM with the hydrogel matrix limit the construction and performance of LM/PVA conductive hydrogels. This study aimed to develop a flexible, high-performance hydrogel for advanced wearable sensors by introducing LM nanoparticles encapsulated in sodium lignosulfonate (LS-LM) into the PVA matrix. The renewable natural macromolecule LS, rich in functional groups, enhanced the compatibility between LM and the PVA matrix. Moreover, LS formed a stable shell around the LM droplets, preventing rupture and leakage of LM, ensuring uniform dispersion within the hydrogel and significantly improving its durability by preventing phase separation. The optimized conductive lignosulfonate-liquid metal/polyvinyl alcohol hydrogel (LS-LM/PVA) exhibited a tensile stress of 1.60 MPa, a compressive strength of 0.53 MPa under 70 % strain, and electrical conductivity (4.87 S m −1 ). The hydrogel-based sensor demonstrated excellent sensitivity (GF = 2.40) and outstanding fatigue resistance (over 500 cycles). A Life Cycle Assessment (LCA) was conducted to evaluate the environmental impacts of LS-LM/PVA hydrogel production. The composite hydrogel-based sensor shows significant promise for advancing human motion tracking and information recognition.