Microfluidic Fabrication of High-Strength Eutectogel@Poly(vinyl alcohol) Core–Shell Helical Fibers toward Sensing Applications

Functional helical ionogel fibers have demonstrated considerable promise for use in sensing and smart wearable devices owing to their unique spiral architecture. However, conventional helical ionogel fibers currently encounter several challenges, including complicated preparation processes, insufficient control over the helical morphology, and a suboptimal mechanical performance, which seriously constrains their practical deployment. Here, a series of core–shell helical ionogel fibers are conveniently fabricated by using a coaxial microfluidic spinning technique. The fiber shell consists of poly(vinyl alcohol) (PVA), which is rapidly solidified during the spinning process via solvent exchange. The ionogel core of the fiber is constructed through in situ polymerization of a polymerizable deep eutectic solvent, milk powder, and metal salt (Li+, Tb3+, or Eu3+). The as-prepared core–shell helical ionogel fibers present remarkable flexibility, mechanical strength (6.1 MPa), and elongation (2352%) attributed to the synergistic effect of the PVA shell with high strength and the ionogel core featuring multiple physical interactions (including hydrogen bonds and metal coordination). Notably, the Eu3+-containing ionogel fiber possesses distinct red fluorescence, ion conductivity, and solvent-responsive characteristics. More importantly, the strain-sensing behavior of the fiber enables its application in wearable sensors for monitoring human motion signals. This study explores a feasible solution for fabricating high-strength, stretchable, and functional helical ionogel fibers suitable for application in flexible wearable devices.