Antifreezing\nand Nondrying Sensors of Ionic Hydrogels\nwith a Double-Layer Structure for Highly Sensitive Motion Monitoring

Abstract

Freezing\nand dehydration together with interfacial failure are\ncapable of causing the functional reduction of hydrogels for sensing\napplications. Herein, we develop a multifunctional bilayer that consists\nof a mussel-inspired adhesive layer and a functionally ionic layer\nthat is composed of sodium <i>p</i>-styrene sulfonate (SSS)\nand an ionic liquid of [BMIM]­Cl. The adhesive layer enables the strong\nadhesion of the bilayer to the surface of the skin. The introduction\nof ionic elements of SSS-[BMIM]Cl not only provides the bilayer with\nsensing adaptability in a wide temperature range of −25 to\n75 °C, but also endows it with elastic, stretchable, self-healing,\nand conductive features. These mechanical properties are utilized\nto assemble a wearable sensor that has unprecedented sensitivity and\nreusability in monitoring human motions, including stretching, pulsing,\nfrowning, and speaking. It is thus expected that the concept in this\nwork would provide a promising route to design soft sensing devices\nthat can work in a wide temperature range.