Necking Created Nano‐Assembly for Super Strong and Tough Hydrogel Fibers

Hydrogel fibers are promising candidates for artificial tissues, yet achieving high mechanical robustness with high water content remains challenging. Here, we report a deformation‐driven strategy that converts strain localization into a controllable pathway for necking created in a nano‐assembly in single‐component hydrogel fibers. By integrating wet spinning and confinement‐assisted drying to form an oriented densified core‐sheath structure, followed by programmed necking and salting‐out treatment, super strong and tough poly(vinyl alcohol) hydrogel fibers are fabricated. This structure enables spatially confined necking to generate amplified local strain, thereby accelerating chain disentanglement and orientation and promoting nanofibrillar assembly and refined nanocrystalline organization. The resulting fibers exhibit exceptional mechanical performance, reaching a maximum tensile strength of 122.5 MPa, a maximum toughness of 350.4 MJ m −3 , and a high water content of 67.9%, comparing favorably with previously reported hydrogel fibers. Moreover, the fibers maintain their shape, sustained mechanical performance, and long cyclic life under simulated body‐fluid conditions for 7 days, demonstrating promising potential for artificial ligament application. This study provides a scalable route to high‐performance hydrogel fibers and offers new insights into harnessing deformation‐enabled structural programming for soft yet robust tissue‐mimetic materials.