A Microphase Engineering Strategy for Spider Silk‐Inspired Fibers With Exceptional Strength, Toughness, and Damping Capacity

ABSTRACT Spider silk exhibits exceptional mechanical properties, inspiring the development of diverse biomimetic fibers. However, spider silk‐inspired fibers typically introduce β‐sheet‐like domains while neglecting microphase structure regulation, failing to overcome inherent strength‐toughness conflict. Herein, a spider silk‐inspired fiber is fabricated through a microphase engineering strategy by mimicking spidroin assembly process and microphase structure evolution during natural spider silk spinning. Polyurethane (PU) serves as raw material because its molecular structure closely resembles that of nature spidroin's architecture. Through a solvent exchange‐induced phase separation process, the long‐range oriented microphase structures are constructed. The as‐spun fiber achieves a high toughness of 626.14 ± 38.01 MJ m −3 , surpassing that of the strongest natural spider silk. Subsequently, post‐treatment is applied to induce crystallization, further increasing the tensile strength to 418.21 ± 9.56 MPa while maintaining a high toughness of 333.09 ± 20.64 MJ m −3 . Notably, the spider silk‐inspired fiber can be used as an energy‐absorbing layer in a ballistic board due to its excellent energy dissipation capabilities, reducing deformation by 36.5% compared with a ceramic‐aramid control upon impact with a ∼730 m s −1 bullet. This work highlights the microphase engineering strategy in enhancing mechanical properties of fibers, offering a simple pathway to fabricate high‐performance spider silk‐inspired fibers.