Mechanically and Conductively Robust Eutectogel Fiber Produced by Continuous Wet Spinning Enables Epidermal and Implantable Electrophysiological Monitoring

In recent years, the collection and monitoring of human physiological signals have garnered increasing attention due to their wide-ranging applications in healthcare, human–machine interaction, sports, and other fields. However, the continuous fabrication of flexible gel fiber electrodes with high mechanical performance, high conductivity, and durability for extreme environments using a simple, efficient, and universal strategy remains challenging for physiological signal acquisition. Here, we have employed a strategy of solvent replacement and multi-level hydrogen bond enhancement to construct eutectogel fibers with continuous solid–liquid structure, achieving continuous production of fibers with high strength, high conductivity, and low-temperature resistance. In the fiber, PVA serves as the solid-state elastic phase, DES as the liquid ionic conductive phase, and CNF as the reinforcement phase. The resulting eutectogel fibers exhibit excellent tensile strength (37.3 MPa), good elongation (> 700%), high electrical conductivity (0.543 S/m), and resistance to extreme dry and −60 °C low-temperature environments. Furthermore, these eutectogel fibers demonstrate high sensitivity for monitoring joint movements and effectively detecting in vitro and in vivo signals, show casing their potential for wearable strain sensors and monitoring physiological signals.