Direct electrospinning of highly twisted, continuous nanofiber yarns

Yarns are key building blocks to construct complicated fibrous structures for diverse applications. Although carbon nanotube yarns have been fabricated by a few novel techniques, challenges still remain in processing other nano fibrous materials into yarns, especially during the fiber fabricating process. In this paper, we report a simple but efficient and versatile method to prepare well-twisted continuous nanofiber yarns directly through an electrospinning process. The yarn electrospinning process used two oppositely charged electrospinning nozzles to generate a hollow nanofiber "cone" on an intermediate funnel collector. Continuous nanofiber yarns can be directly withdrawn from the "cone" apex, with up to 7400 turns per meter of twists inserted through the rotation of the funnel. The maximum yarn production rate is 5 m/min, and the yarn twist level and fiber orientation can be controlled by the funnel rotating speed and yarn withdrawal rate. The yarn tensile properties showed dependence on the twist level.