Winding-Locked Carbon Nanotubes/Polymer Nanofibers Helical Yarn for Ultra-Stretchable Conductor and Strain Sensor.

ABSTRACT：Wearable and stretchable electronics including various conductors and sensors are featured with their light weight, high flexibility and easy integration into functional devices or textiles. However, most flexible electronic materials are still unsatisfactory due to their poor recoverability under large strain. Herein, we fabricated a carbon nanotubes (CNTs) and polyurethane (PU) nanofibers composite helical yarn with electrical conductivity, ultra-stretchability and high stretch sensitivity. The synergy of elastic PU molecules and spring-like microgeometry enable the helical yarn excellent stretchability, while CNTs are stably winding-locked into yarn through simple twisting strategy making for the good conductivity. By virtue of interlaced conductive network of CNTs in micro-level and the helical structure in macro-level, the CNTs/PU helical yarn achieves well recoverability within 900% and maximum tensile elongation up to 1700%. With these features, it can be used as a super-elastic and highly stable conductive wire. Moreover, it also can monitor the human motion as a rapid-response strain sensor by adjusting the content of CNTs simply. This general and low-cost strategy is of great promise for ultra-stretchable wearable electronics and multifunctional devices. KEYWORDS: stretchable electronics • nanofibers • carbon nanotubes • helical yarn • strain sensor.