Multifunctional ion-conductive hydrogels with self-healing, antifreeze, and water-retention capabilities for robust wearable sensing

Abstract

Conductive hydrogels have attracted attention in the field of wearable electronics due to their softness, biocompatibility, and ionic conductivity. However, challenges such as poor signal stability, limited environmental tolerance, and mechanical fragility hinder broader applications. Here, we report a multifunctional ionically conductive hydrogel (Li-gel) synthesized via a two-step process, featuring a polyvinyl alcohol/polyacrylamide (PVA/PAAm) dual network crosslinked with dynamic boronate ester bonds and doped with lithium chloride (LiCl). The hydrogel demonstrates self-healing capability under ambient conditions, and its mechanical strength can recover up to 80% of the original value. It achieves high ionic conductivity (1.1 S m⁻¹) through LiCl-mediated ion transport. LiCl also depresses the freezing point to −13.5 °C and enhances water retention, enabling over 90% mass retention after thermal dehydration and strong resistance to ambient water evaporation. Li-gel exhibits excellent transparency (>90%) and adheres firmly to skin, glass, and plastic, which ensures robust interface stability. Strain-sensing tests yield a gauge factor of 2.00 at 100% strain, with rapid response speed, good strain rate adaptability, and high durability over 1000 stretching–releasing cycles. Altogether, Li-gel combines mechanical resilience, environmental adaptability, and reliable strain-sensing performance, providing a simple and multifunctional hydrogel design for wearable sensing applications.