A Laminated Gravity-Driven Liquid Metal-Doped Hydrogel of Unparalleled Toughness and Conductivity

Conductive hydrogels have been promising candidates for wearable and flexible electronics due to their high flexibility and biocompatibility. However, the previously reported hydrogels with conductivity over 1000 S m−1 usually have poor mechanical properties including low tensile stress (<5 MPa) and toughness (<2 MJ m−3). Here, a liquid metal-doped polyvinyl alcohol (PVA-LM) hydrogel is presented, which simultaneously combines ultra-high conductivity (maximum of 217 895 S m−1) with excellent mechanical properties, including high tensile stress (15.44 MPa), large tensile strain (704%), high toughness (43.02 MJ m−3) and excellent fatigue resistance. Such extremely high conductivity is afforded by self-sintering behavior of LM at the bottom surface that enables the formation of conductive networks. The formation of polymer crystalline regions and polymer-tannic acid multiple hydrogen bonds are responsible for the impressive mechanical properties of conductive hydrogels. Particularly, the electric LM filler could be recycled in the robust hydrogel by dissociation of multiple dynamic interactions. Most importantly, wearable electrodes and capacitive sensors are developed utilizing PVA-LM hydrogel. These devices enable accurate monitoring of bioelectrical signals and human motions, highlighting their immense potential in the realm of soft electronics and wearable technology.