Hierarchically Structured Hydrogel Composites with Ultra‐High Conductivity for Soft Electronics

Abstract Conductive hydrogels possessing high conductivity, stretchability, and biocompatibility are promising materials for underwater devices and bioelectronics. However, typical hydrogels often exhibit low electrical conductivity, which is insufficient for applications requiring high electronic communication. A common approach to increase hydrogel conductivity is to introduce conductive fillers; however, this usually implies a partial sacrifice of stretchability, biocompatibility, and water content. In addition, the electrical properties of hydrogels tend to be unstable due to rehydration in aqueous environments. In this study, a conductive hydrogel composite is fabricated from silver nanowires (AgNWs) and poly(vinyl alcohol) (PVA) employing a synergistic method of freezing and salting‐out treatments. This combined method constructs a hierarchical hydrogel structure and increases the local concentration of AgNWs by inducing continuous phase separation. The resultant conductive hydrogel composites exhibit ultra‐high electrical conductivity (≈1739 S cm −1 ) and electrical stability in aqueous environments while maintaining high water content (≈87%), stretchability (≈480%), and excellent biocompatibility. To illustrate the capabilities of the conductive hydrogel composites, they are applied to bionic sharks, underwater soft circuitry, and electrocardiogram electrodes.