A lignin-based multifunctional elastomer via facile fabrication for wearable strain sensors

Elastomer-based electronics have the potential to maintain both electrochemical conductivity and mechanical properties simultaneously, paving the way for the development of stretchable sensors. However, creating sensors that are extremely stretchable, wearable, and highly sensitive remains a significant challenge. In this work, we present a novel fully bio-based multifunctional polymer (FPL/PTA) designed using thioctic acid (TA) and formaldehyde-protected lignin (FPL). The FPL serves as both a cross-linking agent and a free radical quenching agent. The FPL/PTA features an adaptive polymer network cross-linked by dynamic covalent disulfide bonds and enhanced by multiple non-covalent interactions. This unique structure imparts the material with stretchability, self-healing properties, hydrophobicity, swelling resistance, self-adhesion, and fully recyclable, degradable characteristics. In addition, the simple preparation route, multiple functions, and green characteristics give the elastomer and choline chloride combination as a strain sensor. The sensor exhibits exceptional sensitivity to strain, repeatability, and durability, enabling it to monitor a wide range of human movements, including joint articulation, speech, and swallowing. We believe that the overall performance and feasibility of manufacturing the developed FPL/PTA marks it as a promising multifunctional strain sensor for applications in flexible wearable electronic devices and humanoid robots.