A Liquid Metal-Embedded Sheath-Core Fiber with Internal Helical Structure for Strain-Insensitive Electronics

Stable conductivity is crucial for flexible wearable devices, ensuring reliable signal transmission, sensing accuracy, optimal display performance, and overall device reliability. However, simultaneously achieving high elasticity, superior conductivity, and robust stability remains a formidable challenge. This study presents a novel core-sheath fiber with an internal helical structure as the core layer and an intrinsic elastic material as the sheath layer, which combines the intrinsic elastic material and extensile spiral structure to realize high stretchability, ultra-conductivity, and strain-insensitivity. The hollow fiber with helical channel is fabricated via coaxial wet-spinning technology by adjusting the flow velocity, with an elongation at break of ≈1440%. Subsequent infusion of liquid metal into the channel endows the fiber with outstanding conductivity, reaching 1.94 × 10⁵ S m^-1. Benefiting from the helical structure, the obtained fibers exhibit outstanding strain-insensitivity with a high Q value of 62.5 (resistance variation <1.6%) under 100% strain and show only 30% resistance change even at 600% elongation. The fibers exhibit superior stability against bending, twisting, and compressive deformations. The PU sheath provides excellent waterproof properties, enabling reliable operation in aqueous environments. Moreover, these fibers can be woven into fabrics, exhibiting outstanding performance in joule heaters, near-field communication, and wireless charging applications.