Stretchable, Biodegradable Dual Cross-Linked Chitin Hydrogels with High Strength and Toughness and their Potential Applications in Flexible Electronics

Sensors, displays, and energy storage devices utilized in electronics are undergoing a rapid transition from rigid to flexible and stretchable materials. Traditional electronics-material substrates (metals and semiconductors) have several flaws, including insufficient softness and flexibility and high fragility, resulting in breakage upon stretching and folding. In addition, these materials have limited biodegradability for recycling. Thus, natural polymer hydrogels, with intrinsic biodegradability and biocompatibility, have been recently used to fabricate eco-friendly sensors and flexible energy storage devices. These hydrogels exhibit a vast range of tunable mechanical properties, making them suitable for the fabrication of flexible electronics. Here, dual cross-linked chitin hydrogels with high strength, flexibility, and biodegradability were synthesized using a sequential chemical and physical cross-linking strategy. The dual cross-linked chitin hydrogels exhibited a more comprehensive energy dissipation mechanism than hydrogels that were only physically or chemically cross-linked. Additionally, they could be used as flexible substrates for screen printing, with immense potential applications in the fields of wearable sensors and flexible supercapacitors. Furthermore, the hydrogel-based flexible electronics can be biodegraded in soil or easily recycled in Chitinase solution. This strategy provides a promising route for creating high strength, toughness, and biodegradable chitin hydrogels, which may contribute to the sustainable development of flexible electronics.