One-step coaxial spinning of core-sheath hydrogel fibers for stretchable ionic strain sensors

High-strength, highly conductive, and stretchable conductive fibers are essential for the development of flexible electronic devices. Here, we develop a continuous coaxial wet-spinning method to fabricate stretchable, conductive, and freeze-resistant hydrogel fibers with a core-sheath structure. The core is a supramolecular hydrogel, poly (APhe-co-AAm) (PAPAM), obtained by radical polymerization of acrylamide (AAm) and acryloyl-l-phenylalanine (APhe), and the sheath consists of PVDF-HFP and PU with hydrochloric acid as the coagulation bath. The hydrogel fibers exhibit excellent mechanical properties with a tensile strength of 3.1 MPa and elongation at a break of 750 %. Hydrochloric acid plays two roles in this system: one is to promote hydrophobic association and hydrogen bond formation and improves mechanical properties, and the other is to provide plentiful ions to confer excellent electrical conductivity (10.59 S m−1) and freezing resistance (-20 °C). The application of fiber strain sensors for detecting human motion and pressure sensing demonstrates great potential as wearable electronic devices.