Antifreezing, Water Retention, and High-Stretch Ionic Conductive Hydrogels for Winter Motion Sensing

Abstract

Conductive hydrogels are promising for flexible electronic device applications, where strain change is converted to electrical signal responses. However, most reported conductive hydrogels are typically frozen around 0°C and dried out limiting their potential applications. Herein, a highly stretchable ionic conductive hydrogel (ICH) with antifreezing and water retention properties was prepared using a natural polymer-based hydrogel (sodium alginate-co-polyacrylamide) as the matrix material. By introducing highly hydrated salt CaCl2 and ethylene glycol via a solvent displacement method, the ICH exhibits high ionic conductivity (0.91S/m at 20°C), high transparency (95%), and antifreezing properties (−43°C). Moreover, the optimized ICH achieves a satisfactory sensitivity toward tension strain (gauge factor = 2.58 at 100% strain). Interestingly, a real-time sensing system for wearable motion based on the resulting ICH is well developed by integrating a wireless transmission platform. It is anticipated that such an ICH sensing system will significantly broaden the opportunities for flexible sensor applications.