Rapid and Controllable Preparation of Multifunctional Lignin-Based Eutectogels for the Design of High-Performance Flexible Sensors

Currently, there is a limited amount of research on PEDOT:LS (poly(3,4-ethylenedioxythiophene):sulfonated lignin)-based hydrogels. While the addition of PEDOT:LS can enhance the conductivity of the gel, it unavoidably disrupts the gel network and negatively affects its mechanical properties. The preparation process and freezing resistance of the hydrogels also pose significant challenges for their practical applications. In this study, we have developed a novel self-catalytic system, PEDOT:LS-Fe3+, for the rapid fabrication of conductive hydrogels. These hydrogels are further transformed into eutectogels by immersing them in a deep eutectic solvent. Compared with conventional hydrogels, the eutectogels exhibit improved elongation, mechanical strength, and resistance to freezing. Specifically, the eutectogels containing 2 wt % PEDOT:LS as conductive fillers and catalysts demonstrate exceptional stretchability (∼460%), self-adhesion (∼14.6 kPa on paper), UV-blocking capability (∼99.9%), and ionic conductivity (∼1.2 mS cm–1) even at extremely low temperatures (−60 °C). Moreover, the eutectogels exhibit high stability and sensitivity in flexible sensing, successfully detecting various human motions. This study presents a novel approach for the rapid preparation of the hydrogels by utilizing lignin in the conductive PEDOT polymerization process and forming a self-catalytic system with metal ions. These advancements make the eutectogels a promising candidate material for flexible wearable electronics.