Deep eutectic solvents based ionic conductive gel fibers

Abstract

Fiber-based devices have been the focus for the development of next-generation wearable electronics due to their unique characteristics in lightweight, omnidirectional flexibility, and ability to be flexibly integrated into various types of textiles. They can serve as the fundamental components of wearable electronics for the applications of human healthcare monitoring and human-machine interfaces. Despite these merits, the majority of currently available conductive fibers, which are the building blocks of fiber-based devices, exhibit properties of opacity, relative rigidity, and electron conductivity, thereby significantly limiting the performance of fiber-based actuators, sensors, and interconnects as integral components of flexible and stretchable electronics. Considering these limitations, transparent, stretchable, and ionic conductive hydrogel fibers have garnered significant interest, exhibiting a broad range of prospective applications relating to artificial muscles, skins, and axons. However, hydrogel fibers are still confronted with performance instability at both high temperatures and sub-zero environments. To date, the development of conductive and stretchable gel fibers with high strength and excellent stability remains a significant challenge. To address this challenge, this work proposes to utilize deep eutectic solvents (DESs) for the spinning of ionic conductive gel fibers. DESs are known for their remarkable advantages stemming from good thermal stability, lower price, and ease of synthesis. The non-aqueous nature of DESs can endow gels (named eutectogels) with high dynamic mechanical stability in a broad range of temperatures. Through the incorporation of lithium salts into DESs to fabricate eutectogel fibers, the gel fibers can be significantly toughened, demonstrating exceptional mechanical performance characterized by breaking stress of 15.5 MPa, Young's modulus of 103.8 MPa, and toughness of 38 MJ/m3. Such tough eutectogel fibers exhibit multifunctions in terms of shape-memory behavior, strain sensing, and recyclability. This straightforward and adaptable strategy represents a promising avenue toward the development of sturdy eutectogel-based fibrous materials for a broad spectrum of intelligent applications.