Scalable Layered Heterogeneous Hydrogel Fibers with Strain‐Induced Crystallization for Tough, Resilient, and Highly Conductive Soft Bioelectronics

The advancement of soft bioelectronics hinges critically on the electromechanical properties of hydrogels. Despite ongoing research into diverse material and structural strategies to enhance these properties, producing hydrogels that are simultaneously tough, resilient, and highly conductive for long‐term, dynamic physiological monitoring remains a formidable challenge. Here, a strategy utilizing scalable layered heterogeneous hydrogel fibers (LHHFs) is introduced that enables synergistic electromechanical modulation of hydrogels. High toughness (1.4 MJ m−3) and resilience (over 92% recovery from 200% strain) of LHHFs are achieved through a damage‐free toughening mechanism that involves dense long‐chain entanglements and reversible strain‐induced crystallization of sodium polyacrylate. The unique symmetrical layered structure of LHHFs, featuring distinct electrical and mechanical functional layers, facilitates the mixing of multi‐walled carbon nanotubes to significantly enhance electrical conductivity (192.7 S m−1) without compromising toughness and resilience. Furthermore, high‐performance LHHF capacitive iontronic strain/pressure sensors and epidermal electrodes are developed, capable of accurately and stably capturing biomechanical and bioelectrical signals from the human body under long‐term, dynamic conditions. The LHHF offers a promising route for developing hydrogels with uniquely integrated electromechanical attributes, advancing practical wearable healthcare applications. Layered heterogeneous hydrogel fibers (LHHFs) that are tough, resilient, and highly conductive, are manufactured by a microchannel‐integrated wet spinning method. The uniquely combined electromechanical properties stem from the reversible strain‐induced crystallization and the symmetric layered structure with separated electrical and mechanical functional layers. The LHHFs are directly utilized as soft iontronic sensors and epidermal electrodes for wireless full‐body physiological monitoring.