Hierarchical Coaxial Elastic Fibers Enabled by Porous Crack‐Evolution Mechanisms for Highly Sensitive Ultrabroad‐Range Strain‐Sensing

Broad‐range strain‐sensing is significant for emerging applications in human motion detection, physiological monitoring, and robotic manipulation. Fiber‐based stretchable strain sensors are particularly attractive owing to their intrinsic flexibility, weavability, and compatibility with complex deformation modes. However, achieving both ultrahigh sensitivity and broad sensing ranges remains challenging because conductive networks within elastic fiber systems often undergo uncontrolled structural disruption under large deformation. Herein, a hierarchical coaxial strain‐sensing fiber (HCSF) is developed through a synergistic porous crack‐evolution mechanism enabled by a hierarchical core–sheath architecture and an engineered composite sensing layer. The porous conductive network provides stable electron transport at low strains, while the progressive evolution of microcracks under increasing deformation generates amplified resistance variations across a broad strain regime. The optimized HCSF delivers an ultrahigh gauge factor of 233 549, an ultrabroad sensing range of 426.4%, a low detection limit of 1% strain, and a fast response time of 45 ms. Benefiting from their outstanding flexibility and mechanical robustness, the HCSFs can be readily integrated into textiles and soft pneumatic actuators for real‐time physiological signal monitoring and large‐deformation motion sensing. This work establishes a crack‐evolution‐guided electromechanical coupling strategy for high‐performance strain‐sensing fibers, offering new opportunities for wearable electronics, intelligent textiles, and soft robotics.