2, Drexel University, Philadelphia, Pennsylvania, United States
Ultrafine electrospun fibers have been utilized in numerous applications including tissue scaffolding, energy storage, sensing, and water treatment. However, randomly oriented nonwoven fiber mats from conventional electrospinning can be easily tear apart, limiting their broader uses and scaling up. To make it mechanically strong, electrospinning set up was modified in order to align and group single fibers together as a yarn which is knittable, and can be prepared in wide range of complex structures. In this work, continuous electrospun yarns were prepared by electrospinning of Polycaprolactone (PCL) from 2 spinnerets spun toward a rotating funnel. The polymer jets were solidified and assembled at the funnel before it was continuously withdrawn as a long fiber bundle. Beside the setup component position, solvent type was found to have a large effect on polymer jet stability and continuous process of yarn manufacturing. The tensile strength of obtained PCL yarn was significantly higher than that of PCL nonwoven mat, and it could be hand-braided, indicating their potential as a knittable yarn. Plying was applied to PCL yarn to achieve a better mechanical performance, and we found that PCL cords was strong and comparable to commercial yarns. We successfully knitted PCL cords by a computerized knitting machine, fabricated fabrics entirely from nanofibers. With high surface area, high porosity and nanoroughness, these fabrics can enhance functionalities leading to novel wearable technologies such health monitor and energy storage cloth. Furthermore, with a modification of electrospinning setup, we produced core-sheath yarns by inserting a commercial yarn as a core. It provides mechanical robustness which would bring the nanotechnology to human scales.