Ultra‐Tough, Freeze‐Tolerant Hydrogel Fibers via Synergistic Freeze‐Spinning and Salting‐Out

ABSTRACT Hydrogel fibers, which merge the inherent softness and biocompatibility of hydrogels with the high aspect ratio and flexibility of a fibrous structure, are highly sought after for next‐generation fibrous devices. However, their applications suffer from trade‐offs in mechanical robustness, environmental tolerance, and scalable production. Here, we introduce a synergistic freeze‐spinning and salting‐out strategy to overcome these intertwined challenges simultaneously. Freeze‐spinning aligns polyvinyl alcohol chains, enabling continuous production of oriented fibers. Subsequent salting‐out in sodium citrate/glycerol/H 2 O solution synergistically enhances properties: citrate ions induce physical crosslinking to boost strength, orientation, and crystallinity, while glycerol provides freeze resistance and moisture retention. The resulting fibers exhibit an unattainable combination of ultrahigh elongation (1779.08 % ± 130.33 %) and tensile strength (20.50 ± 0.52 MPa), breaking through the performance boundaries of traditional hydrogel fibers. Furthermore, embedded silver nanowires endow the fibers with stable electrical conductivity and strain‐sensing even at −40°C. This work integrates ultra‐high strength, toughness, broad‐temperature environmental tolerance, and electronic functionality into a single hydrogel fiber, opening new avenues for high‐performance fibrous devices.