Abstract: Current research on yarn-based smart wearable devices primarily concentrates on the structure, materials, and preparation methods of individual devices. However, few studies explore design concepts for the geometric structure of yarn-based smart wearables and their impact on various application areas. Based on this, the paper reviewed the geometric structure design ideas, preparation methods, important performance indicators, and application fields of yarn-based smart wearable devices with various structures in recent years. Yarn-based smart wearables are broadly categorized into four main types of geometric structures: coaxial yarns, twisted yarns, parallel-type yarns, and fancy yarns. Among them, coaxial yarns are more suitable for creating energy-harvesting devices like nanogenerators. Twisted structured yarns are better suited for high-response sensing devices because of their exceptional stretch and strength. In comparison, paralleltype and fancy yarns are used less often. This provides references and ideas for the future structural design of yarn-based wearable devices.

Key words: smart wearable devices; core-shell structure yarn; braided structure yarn; helical structure yarn;double-helix structure yarn