Highly stretchable, durable, and transient conductive hydrogel for multi-functional sensor and signal transmission applications

Conductive hydrogel has attracted immersive attentions as the most promising candidate for the fabrication of next-generation wearable and soft electronics due to its diverse characteristics. However, simultaneously embodying integrated characteristics, including mechanical durability, electrical sensitivity, environmental stability, and disintegration after service, into a single hydrogel system is still a grand challenge. This work proposed an interfacial engineering strategy to fabricate a transient conductive hydrogel with well-balanced properties, addressing the long-lasting issue of interfacial incompatibility between solid conductive fillers and soft polymer matrix. Using TEMPO-oxidized cellulose nanofibrils (CNFs) as the interfacial stabilizer, a stable CNF encapsulated liquid metal nanoparticles (LMNPs) is synthesized, which can initiate free-radical polymerization of acrylic acid (AA) monomers, forming an entirely physically crosslinked PAA-CNF-LMNPs hydrogel. This hydrogel features several advantages that have not been realized in a single hydrogel, including, environmentally friendly fabrication without addition of chemical initiators and crosslinkers, superb stretchability, satisfied solvent independent conductivity, high strain sensing sensitivity, stable signal transmission, as well as crack insensitive, self-healing, anti-freezing, and transient properties. Owing to these all-round superb properties, this resultant hydrogel is considered a sustainable, durable, and high-performance platform for soft and wearable electronics.