Liquid Metal Reinforced Double-Network Hydrogels for Flexible and Stretchable Strain Sensors

To meet the demands of wearable flexible electronics, a xanthan gum (XG)-stabilized liquid gallium (Ga) nanoparticle-reinforced poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) double-network conductive hydrogel (Ga-PXA) was developed. XG enables uniform dispersion of Ga nanoparticles via coordination stabilization. Under thermal initiation with APS, and potentially assisted by Ga itself, the system subsequently forms a synergistically strengthened dual-network conductive nanocomposite structure. The rigid chemically cross-linked PAA network interpenetrated with the soft physically cross-linked PVA network, endowing the hydrogel with high stretchability (>500%), toughness, and excellent cyclic stability and fatigue resistance through efficient energy dissipation. Uniformly distributed liquid-metal nanoparticles established continuous conductive pathways, achieving an electrical conductivity of 0.9 S m^-1. The reversible deformation of the double-network structure enabled strain sensors with high sensitivity (GF = 4.8), a wide sensing range, and fast response. Abundant -OH and -COOH groups imparted strong adhesion to substrates such as porcine skin (68.04 kPa). The hydrogel also exhibited favorable biocompatibility and antibacterial activity. This strategy demonstrates the synergistic enhancement of mechanical, electrical, and interfacial properties of hydrogels via double-network design coupled with functional nanoparticle incorporation, showing promise for electronic skin and wearable health monitoring applications.