Mass production of stretchable conductive wrapped yarns for strain sensors: a parametric study of outer-inner twist ratio

Abstract

Stretchable conductive yarns are gaining increasing prominence in smart wearable electronics, facilitated by the scalable hollow-spindle wrap spinning technique. Yet, for double-sheath yarns with equal sheath densities, the influence of the outer-inner twist ratio on yarn structure and properties remains largely unexplored. Herein, stretchable conductive wrapped yarns (SCWYs) were fabricated with varying outer-inner twist ratios, employing elastane filament (EF) as the core and silver-plated nylon filaments (SPNFs) as the dual helical sheaths. The twist ratio significantly affects both yarn structure and properties. Optimal ratio of 1.0 was determined via technique for order preference by similarity to ideal solution (TOPSIS). The resulting SCWY exhibits an elastic stretchability exceeding 150 % and demonstrates excellent stability under cyclic loading. Moreover, the yarn is capable of effectively monitoring human movements and transmitting Morse-code signals in emergency scenarios. Such work presents a feasible strategy for mass production of stretchable conductive yarns for advanced wearable electronics.