Fabrication of continuous electrospun nanofiber yarns with direct 3D processability by plying and twisting

Abstract

Nanofiber yarns were continuously manufactured by a homemade plying and twisting device using nanofiber filaments, and the structures of the nanofibers were examined. A twist setting process was performed on the yarns following the plying and twisting process, and the influences of temperatures and times on twist setting effects and mechanical properties of the as-treated yarns were studied. Meanwhile, the effects of plies and twists on structures and mechanical properties of the yarns were also investigated. The results show that the structures of the nanofibers were demonstrated to have a skin-core structure, and the optimum twist setting temperature and time were determined to be 90°C and 30 min, respectively. With more filaments plied into a yarn, the measured values of yarn diameters were all smaller than the theoretical ones, the yarn-diameter uniformities improved, the nanofiber diameters decreased, and the alignment degree of nanofibers along the twist direction (ADT) improved. The breaking stress and initial modulus increased when the number of plies increased from 1 to 4, but when more than four filaments were plied into a yarn, both of them decreased, while the breaking strain increased. With increasing yarn twists, both nanofiber and yarn diameters decreased, but the ADT increased. The breaking stress and initial modulus initially increased as the twists increased to 2500 twists per meter before decreasing, while the breaking strain kept increasing. Meanwhile, the breaking strength of the plied yarns was considerably greater than that of the non-plied ones, which ensured the possibility of subsequent 3D manufacturing.

Continuous manufacturing of nanofiber yarn with the assistance of suction wind and rotating collection via needleless melt electrospinning

“…Also, the lateral pressure contributed to the straightening of the bent and hooked nanofibers in the twisting direction during the nanofiber twisting process. Meanwhile, when the bent and hooked nanofibers were twisted to the oblique locations, the large twisting angle resulted in a long straightening process; this provided more time for the nanofibers to be straightened . As more bent and hooked nanofibers were straightened along the twist direction, the ADT increased.…”

“…The structure of electrospun nanofiber yarns is an ordered structure of assembled electrospun nanofibers . The continuous nanofiber M‐ESP process could be divided into three parts: (1) the production of aligned nanofiber bundles by the suction wind apparatus, (2) the collection of bundles on a collecting roller, and (3) the simultaneous drawing and twisting of the bundles by the coaction of the collecting roller and the rotating disk.…”

Long Path Towards to Success in Electrospun Nanofiber Yarn Production Since 1930’s: A Critical Review

“…However, some of the available attempts mainly present basic conceptual ideas; therefore, it is difficult to talk about real nanofiber yarn production or nanofiber yarn structures [6][7][8][9][10][11][12], while some works present only images [63] belong to fiber webs or oriented fiber arrays [18,19,23]. On the other hand, some studies, although they are valuable attempts for further works, do not present a real yarn spinning system because they mainly produce nanofiber web strips at a certain length first, followed by twisting or plying of these strips at a next step, therefore, being a discontinuous process rather than a real spinning system [1,32,38,39,59,60,61,63]. There are also attempts that can produce real twisted nanofiber yarns continuously; however, there is usually no information about the stability of the spinning system or yarn length that can be spun without any break.…”

“…In another approach, the fibrous strips are produced first and then these are converted into yarn by plying [32]. In this approach, both spinneret and the auxiliary electrode were connected to the cathode of high power supply, while the anode was inserted into the bottom of the bath (Table 3d).…”

Conjugate Electrospinning Construction of Microyarns with Synchronous Color-Tuned Photoluminescence and Tunable Electrical Conductivity

“…[44][45][46] However, most of the current electrospun nanofibers are collected in the shape of conventional non-woven membranes with relatively disordered structure and weak mechanical properties, which has limited the applications of nanofibers. [47][48][49][50] Recently, many researchers have shifted their attention from unordered nanofiber membranes to oriented nanofiber bundles or yarns in order to overcome this obstacle and open up new application areas for nanofibers. [51][52][53] Several efforts have been reported for fabricating nanofiber yarns with highly aligned structure, unique performance and new applications.…”