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.