Sheath-Free E-Yarns through yarn covering for enhanced knittability

Abstract

Recent advancements in electronic textiles have enabled the integration of sensing, illumination, and communication functions directly into fabrics, opening new possibilities in healthcare, sports, and wearables. A key innovation in electronic textiles is the development of electronic yarns, which embed miniature electronic components, such as LEDs, within textile-compatible yarns. Traditional E-yarn fabrication includes a sheathing step using knit braiding to protect electronic components and interconnects; however, this process significantly increases yarn diameter, introduces stiffness and requires specialized machinery, thus limiting compatibility with fine textile structures. This study proposes a simplified fabrication approach that eliminates the conventional sheathing stage by using an alternative yarn covering technique that still provides necessary mechanical and environmental protection to the embedded LEDs before knitting. Even without the sheathing process, the developed E-yarns remain compatibility with standard knitting processes, as experimentally demonstrated using a computerized flatbed knitting machine with standard yarn feeders and tensioning devices. Experimental validation further demonstrated significant reductions in yarn diameter (down to ~1.3mm from ~1.5–2mm in prior work), improved flexibility, and simplified manufacturing without compromising mechanical durability or LED functionality. The proposed technique offers a viable pathway for scalable, comfortable, and mechanically robust integration of smart functionality seamlessly into textile systems.