Skin-inspired laminated liquid metal doped hydrogel with mechanical toughness and high electrical conductivity†

Abstract

Developing a simple method to prepare conductive hydrogels with both mechanical toughness and high electrical conductivity remains a significant challenge. Here, a laminated conductive hydrogel was engineered, featuring a unique composition with EGaIn micro/nanodroplets concentrated on one side and polyvinyl alcohol (PVA) hydrogel on the other. To achieve high electrical conductivity in the liquid metal (LM) conductive layer, while preventing the aggregation of liquid metal particles (LMPs) within the PVA hydrogel, PEDOT:PSS nanoparticles with an electrical potential opposite to that of the LMPs were introduced. Under the combined effects of gravitational settling and electrostatic-assisted settling, the LM conductive layer forms a network of large liquid metal particles as the primary framework, with smaller particles serving as network interconnectors. This configuration offers excellent electrical conductivity (1.67 × 10⁵ S m⁻¹) and maintains stable resistance under 617% tensile strain. Due to multiple cross-linking mechanisms, the prepared conductive hydrogel exhibits high Young's modulus (∼178.14 MPa), stretchability (∼818%), and toughness (∼185.9 MJ m⁻³), outperforming most existing tough gels, biological tissues, and natural rubber. The conductive hydrogel enables the creation of ultra-thin capacitive sensors with high sensitivity (0.05 g) and rapid response (20 ms). These devices enable accurate monitoring of human motions and bioelectrical signals, highlighting their immense potential in the fields of soft electronics and wearable technology.