Magnetically responsive intelligent fibers: nano-engineered materials and multifunctional integration for advanced applications.

Magnetically responsive intelligent fibers represent a new class of smart materials that integrate magnetic components into flexible fiber systems, enabling remote actuation, real-time sensing, and self-powered operation under external magnetic fields. With advantages in flexibility, adaptability, and multifunctionality, they hold promise for wearable electronics, soft robotics, biomedical devices, and energy harvesting. This review highlights recent progress in their design, fabrication, and applications. We summarize magnetic materials used in fiber integration-including ferrites, metal alloys, rare-earth compounds, and 2D materials-focusing on structural and magnetic properties. Multi-physics coupling mechanisms such as magneto-mechanical, magnetoelectric, and magneto-optical effects are discussed as the basis of intelligent responses. Fabrication strategies, including extrusion-based printing, magnetic-field-assisted alignment, and surface modification, are evaluated for scalability, resolution, and material integration. Key challenges for commercialization, such as dispersion, biocompatibility, and mechanical stability under dynamic conditions, are also addressed. Finally, future directions are outlined, emphasizing multifunctional fibers with combined stimuli-responsiveness and integration into adaptive systems. This review aims to provide a framework for advancing magnetically responsive fibers and inspiring future innovations in smart fiber technologies.