Helical and Crimped Fibers: A Review from a Structure-Property-Application Perspective

Helical and crimped fibers represent a promising class of biomimetic materials owing to their unique nonlinear geometry and the resulting superior properties. However, a systematic understanding of how their structural features-ranging from regular three-dimensional helices to imperfect helices (irregular 3D crimped morphologies)-translate into functional advantages remains limited. This review establishes an integrated framework linking the structure, advantages, and applications of these two related yet distinct fiber families. Key fabrication strategies are briefly outlined, followed by a discussion of the unique structural features including coiled geometry, spring-like structure, and chirality, and their corresponding performance advantages. Furthermore, we highlight their representative applications across sensing, soft robotics, biomedicine, energy, thermal management, filtration, and functional materials to demonstrate the translation of structural advantages into specific functions. Critical challenges are identified, including improving preparation methods, optimizing structure-performance coordination, and developing green, interdisciplinary approaches. Finally, future research directions are proposed to guide the rational design and practical utilization of helical fibers in advanced functional materials. This review provides a clear roadmap for researchers aiming to exploit the full potential of these bio-inspired nonlinear fibers.