Knitting RFID yarns towards smart fabrics for motion sensing and identification

Smart textiles integrate fabric comfort and flexibility with electronic functionality, offering transformative potential in healthcare, sports monitoring, and human-machine interfaces. However, most existing wearable systems rely on external circuit boards that compromise comfort, washability, and mechanical robustness. Here, we present a scalable textile-electronics integration strategy based on custom-engineered ID-Yarns ( ~ 500 μm in diameter) that embed semiconductor Radio-Frequency Identification (RFID) chips and antennas and can be seamlessly incorporated into fabrics using standard knitting processes. Using parameterized knitting geometries, we demonstrate two functional fabrics: a stretchable, interference-resistant Sensing-Fabric for precise motion detection, and a stretchable, deformation-insensitive Identification-Fabric (ID-Fabric) for stable passive wireless communication. Both fabrics exhibit strong mechanical endurance, maintaining functionality after more than 10,000 stretching and twisting cycles and over 20 machine washes while preserving consistent wireless performance. This work establishes a passive, yarn-level fiber-chip integration framework and provides a scalable solution toward soft, durable, and high-performance e-textiles through the synergistic design of yarn architecture and knitting-based antenna engineering.