Progress in polysaccharide-based conductive hydrogels: Natural sources, functional types, and their roles in energy and biomedical applications

Polysaccharides, as the most abundant and renewable natural polymers, serve a crucial role in the advancement of hydrogel materials due to their inherent biodegradability, biocompatibility, and functional modifiability. Polysaccharide-based conductive hydrogels have attracted significant popularity within the field of flexible electronics as a result of their excellent electrical conductivity, mechanical flexibility, environmental sustainability, and ability to interface seamlessly with biological tissues. This review offers an in-depth discussion of recent developments in this rapidly evolving area, beginning with an introduction to commonly used polysaccharide materials such as chitosan, cellulose, starch, carboxymethyl cellulose, agarose, and carrageenan. It reviews their molecular structures, functional groups, and modification strategies that enable electrical conductivity, including blending with conductive fillers (e.g., carbon nanotubes, graphene, and metal nanoparticles) and chemical doping. Furthermore, the review examines various preparation methods such as physical crosslinking, chemical crosslinking, and freeze-thaw techniques and their impact on hydrogel performance. It explores critical properties such as mechanical strength, stretchability, self-healing ability, environmental resistance (e.g., anti-freezing and anti-drying), ionic/electronic conductivity, and transparency. The multifunctionality of these hydrogels is emphasised by their wide range of applications, including but not limited to: wound healing, wearable sensors, artificial skin, energy storage devices (such as supercapacitors and batteries), fuel cells, solar cells, and gas sensors. Finally, the paper discusses existing problems and suggests future research directions for polysaccharide-based conductive hydrogels in flexible electronics.