Liquid metal/polyurethane core-sheath coaxial conductive filaments for human motion detection and thermal management

ABSTRACT Flexible strain sensors have been widely applied in human motion monitoring, healthcare, smart textiles, and wearable electronics. However, existing application-specific technologies face several challenges, including non-uniform distribution of conductive materials within flexible substrates, delamination risks due to modulus mismatch, and inadequate mechanical durability and conductive stability. This study presents a scalable fabrication strategy for core-sheath filaments through wet spinning. The filament design employs liquid metal (LM) as the conductive core, which exhibits exceptional electrical conductivity, fluidity, and long-term durability, while thermoplastic polyurethane (TPU) functions as the protective sheath, offering high elasticity and robust mechanical strength. The TPU layer effectively encapsulates the LM core, endowing the resulting strain sensor with excellent stretchability (0–100%), compressibility (30–240 N), high sensitivity (gauge factor < 8.37), and stable performance over more than 100 cycles. The superior conductivity of the liquid metal enables precise resistance responses to subtle physiological deformations, such as limb movement, respiration, and heartbeat. Furthermore, fabrics woven from LM/TPU filaments demonstrate enhanced thermal insulation and efficient heat dissipation capabilities. This work proposes an efficient and scalable method for the mass production of flexible liquid metal sensors and multifunctional thermally protective textiles.