Enhanced multifunctional liquid metal-based hydrogels with vinyl silica nanoparticles for advanced strain sensing applications

Abstract

Conductive hydrogels have garnered considerable interest for their applications in wearable electronic skins, owing to their superior properties. Nevertheless, challenges persist, including low sensitivity, poor cyclic stability, and limited tolerance to extreme conditions. This study develops a novel liquid metal-based conductive hydrogel with a dual cross-linked polyacrylic acid (PAA) matrix, employing both “soft” coordination and “hard” covalent cross-linking mechanisms. This hybrid network is formulated using guar gum (GG)-stabilized gallium (Ga) droplets, which catalyze the copolymerization of vinyl-hybrid silica nanoparticles (VSNPs) and acrylic acid (AA). The resultant Ga³⁺ ions interact with carboxyl groups in the PAA, forming soft coordination links that enhance the hydrogel’s rapid gelation. The incorporation of VSNPs significantly enhances the hydrogel’s elasticity, toughness, and low-temperature resilience without glycerol. Notably, its intrinsic moldability, adhesion, and self-healing properties are retained. Applied as a strain sensor, this hydrogel demonstrates a high gauge factor (GF) of 17.4, responsive time of 250 ms for both activation and recovery, an ultra-low detection limit of 0.1%, and excellent durability over 800 cycles at 100% strain. Short-term immersion in a glycerol solution (20 min) further augments its stretchability to 2688% and GF to 28.1 across a strain range of 1325%–1450%, broadening its operational ranges to 0–1450% at −18°C. Prolonged exposure (4 h) also improves water retention and high-temperature resistance, making this hydrogel a promising material for sustainable, high-performance wearable electronics.