Developing Tough, Fatigue-Resistant and Conductive Hydrogels by In-Situ Growing Metal Dendrites

Developing hydrogels with high conductivity and toughness via a facile strategy is important yet difficult. Here, we propose a new strategy to develop conductive hydrogels by growing metal dendrites. The water soluble Sn2+ ions are soaked into gel and then converted to Sn dendrite via electrochemical reaction; the excessive Sn2+ ions are finally removed by water dialysis, along with dramatic shrinkage of gel. Based on in-situ transformation from metal ion to dendrites, the method integrates the advantages of ionic conductive filler like LiCl (uniform dispersion) and electrical filler like metal particles (high conductivity). Besides, the morphology of metal dendrites takes advantages of 1D nanowires (large aspect ratio of branches) and 2D nanosheets (large specific surface area of skeleton). The strategy is effective on diverse gel systems (non-ionic/anionic/cationic/zwitterionic). The dense, highly conductive and branched Sn dendrites not only connect to form conductive pathway, but contact with polymer network to transfer stress and dissipate energy. The resultant gel exhibits high conductivity of 12.5 S m-1, fracture energy of 1334.0 J m-2, fatigue threshold of 720 J m-2. Besides, the gel exhibits excellent sensitivity when applied as wearable strain sensor and bioelectrodes. We believe the strategy offers new insights into developing conductive hydrogels.