Lignin-enabled ultra-stretchable eutectic gels for multifunctional sensors.

Eutectic gels as important conductive polymers have promising practical applications in wearable electronic devices. However, the development of the ultra-stretchable and self-adhesive eutectic gel for multifunctional flexible sensors remains a challenge. Here, a lignin-enabled ultra-stretchable eutectic gel (LEG) integrating with excellent self-adhesion and high conductivity is prepared through polymerizable deep eutectic solvents (PDES) treated lignin followed by in-situ polymerization. In this LEG, the lignin macromolecules are utilized as important mediators to build dynamic crosslinking points in the polyacrylic acid (PAA) networks via hydrogen bond interactions. The dynamic disruption and reconstruction of the hydrogen bonds between the mobile PAA chain and dynamic crosslinking points ensure the high integrity of the crosslinking network to realize the ultra-stretchability (about 4845 %). Additionally, the abundant phenol groups of lignin endow the LEG with robust self-adhesion, which allows the LEG to seamlessly adhere to the different substrates. Based on these features, the LEGs are assembled as wearable strain sensors with high sensitivity, fast response time, and long-term sensing stability, and this wearable strain sensor demonstrates promising applications in human motion monitoring and information encryption systems. This work develops an effective pathway to design lignin-enabled ultra-stretchable eutectic gels for multifunctional sensors.