Conductive Ionically Cross-Linked Gluten/Poly(vinyl alcohol) Composite Organohydrogel with Freezing and Water Resistance for Wearable Sensors

Conductive hydrogels have attracted a lot of research interest in artificial intelligence, health monitoring, soft robotics, and more. However, it is still a great challenge to combine the hydrogel platform with electrical conductivity, high tensile strength, self-adhesiveness, low-temperature resistance, and water resistance in a green and low-cost way. As a rich biodegradable plant protein that can be mixed with water and kneaded into highly viscous and stretchable hydrogels, gluten shows great potential in the field of flexible sensing. However, gluten-based hydrogels can be easily deformed under stress, showing low resilience and poor structure stability. Therefore, to solve these problems, poly­(vinyl alcohol) (PVA), glycerol, and different ions were introduced into the gluten hydrogel to improve its mechanical and conductive performances. The as-prepared gluten-PVA-glycerol-LiCl (GPGLi) organohydrogel revealed high stretchability (>743%), high toughness (1.48 MJ/m3), water resistance, frost resistance, and long-term stability, in which abundant hydrogen bonds were formed between PVA and gluten as well as glycerol and water. These characteristics paved the way for the development of a flexible strain sensor with high sensitivity over different stretching ranges for body motion monitoring. In addition, the GPGLi organohydrogel was found to be water-resistant, making it applicable for underwater activity monitoring as well. Finally, the GPGLi organohydrogel was adopted as a wireless sensing component for monitoring real-time pulse, implying the great potential of gluten in flexible sensing.