Wearable flexible sensors based on dual-network ionic hydrogels with xanthan gum/sodium alginate/polyacrylamide/gallium indium alloy.

With the rapid development of wearable electronic devices and smart sensors, flexible sensors have received much attention due to their excellent mechanical properties and good adaptability. However, developing a simple method to produce conductive hydrogels with excellent electrical conductivity, mechanical properties, environmental stability, and durability is still a major challenge. In this study, a novel dual-network composite flexible sensor was developed, which was mainly composed of xanthan gum (XG), sodium alginate (SA), polyacrylamide (PAAm), and gallium‑indium alloy (Ga-In). The sensor combined the good biocompatibility and thickening properties of natural polysaccharides, the flexibility of polymers, and the excellent electrical conductivity of conductive metal alloys. The sensors exhibited good mechanical properties (stress ≈ 400 KPa, strain ≈ 540 %), high fatigue resistance, recoverability and excellent environmental adaptability. In addition, the addition of liquid metal could increase the conductivity (1.83 S m) of the hydrogel while maintaining high transparency, and the flexible sensor device constructed from it had high sensitivity to strain (GF = 2.75). Therefore, the hydrogel as a flexible sensor showed promising applications in detecting human movement, which could monitor the movement of human joints, micro-expressions, and handwriting. This will provide new ideas for scientific management of sports and health monitoring.