Single‐Fiber Design for Higher Performance Artificial Muscles

Artificial muscles are essential components in the advancement of next-generation soft robotics, biomedical devices, and adaptive wearables. While conventional fiber-based actuators often rely on multi-material assemblies and complex interfacial engineering, their performance is limited by structural heterogeneity and low-efficient energy coupling. This review highlights the emerging paradigm of single-fiber or in-fiber artificial muscle design, where actuation functionality is intrinsically encoded within the molecular architecture of individual fibers. We comprehensively examine state-of-the-art material systems such as phase-transition materials, block copolymer self-assemblies, mechanically interlocked polymers, covalent supramolecular hybrids, and woven polymer networks. Particular emphasis is placed on the structure-property-function relationships that govern the actuation strain, stress output, response speed, and long-term durability. We also propose a unified framework for evaluating single fiber actuator performance based on key metrics and critically discuss manufacturing challenges, scalability, and integration with smart sensing system. This review provides a roadmap for molecular design of the high-performance artificial muscle, offering new strategies for intelligent actuation and soft material systems in real-world applications.