Coaxial Printing Strategy for Fabricating Hydrogel-Based Fiber Sensors with High Flexibility and Consistency

Abstract Hydrogel fibers are of great interest in soft bioelectronics due to their miniature size, high flexibility, and excellent compatibility with biological tissues. However, it remains challenging to maintain structural and sensing performance stability during large-scale fabrication. Here, we integrate coaxial extrusion with an “in situ crosslinking” approach inside a light-transmitting capillary to continuously fabricate elastic, conductive core–shell hydrogel fiber sensors. The sheath comprises methacrylated recombinant human collagen (RHC-MA), whereas a thixotropic nanoclay/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) composite forms the conductive core. Rapid photocrosslinking stabilizes the low-viscosity RHC-MA sheath during extrusion, while the nanoclay network limits interlayer mixing and supports a distinct core–shell geometry. Adjusting the core flow rate enables a transition from linear to helical core architectures without nozzle rotation or a coagulation bath. Meter-scale fibers were fabricated and integrated with a wireless acquisition system and a multilayer perceptron for gesture recognition, achieving an accuracy of 95.1%. This strategy broadens the processing window for low-viscosity photocrosslinkable biomacromolecular inks and provides a scalable route to structurally tune hydrogel fiber sensors (HFSs).