Polymeric nanofibers are a fascinating class of material that has been widely used in a myriad of applications, including fiber reinforced composites, protective clothing, and chemical sensors. Here, the science of the combined application of external pressure, controlled infusion of polymer solution and gyration, which allows mass production of uniform polymeric nanofibers in a single step, is uncovered. Using poly(ethylene oxide) as an example this study shows the use of this novel method to fabricate polymeric nanofibers and nanofibrous mats under different combinations of processing parameters such as working pressure (1 × 10 5 to 3 × 10 5 Pa), rotational speed (10 000-36 000 rpm), infusion rate (500-5000 µL min −1 ), and fiber collection distance (4-15 cm). The morphologies of the nanofibers are characterized using scanning electron microscopy and anisotropy of alignment of fiber is studied using 2D fast Fourier transform analysis. A correlation between the product morphology and the processing parameters is established. The produced fibers are in a range of 50-850 nm at an orifice-to-collector distance of 10 cm. The results indicate that the pressure coupled infusion gyration (PCIG) offers a facile way for forming nanofibers and nanofiber assemblies.

This work focuses on forming bead on string poly(caprolactone) (PCL) by using gyration under pressure. The fibre morphology of bead on string is an interesting feature that falls between bead-free fibres and droplets, and it could be effectively controlled by the rheological properties of spinning dopes and the major processing parameters of the pressurised gyration system which are working pressure and rotating speed. Bead products were not always spherical in shape and tender to be more elliptical, therefore both their width and length were measured. The average bead width and length produced spanned a range 145 -660µm and 140 -1060µm, respectively. The average distance between two adjacent beads (i.e. inter-bead distance) and the bead size (width and length) are shown to be a function of processing parameters and polymer concentration. An interesting morphology i.e. beads with short fibre was observed when using a high polymer concentration. Bead on string structure agglomeration was promoted by a low polymer concentration. Formation of droplets or agglomerated bead on string is promoted below 5wt% polymer concentration, and beads with short fibre were present in the microstructure beyond a polymer concentration of 20 wt%.

Several new spinning methods have been developed recently to mass produce polymeric fibers. Pressure-coupled infusion gyration is one of them. Because the fiber diameter plays a pivotal role for the mechanical, electrical, and optical properties of the produced fiber mats, in this work, polyethylene oxide is used as a model polymer, and the processing parameters including polymer concentration, infusion (flow) rate, working pressure, and rotational speed are chosen as variables to control fiber diameters spanning the micro- to nanoscale. The experimental process is modeled using response surface methodology, both in linear and nonlinear fitting formats, to allow optimization of processing parameters. The successes of the fitted models are evaluated using adjusted R 2 and Akaike information criterion. A systematic description of the experimental process could be obtained according to the model in this study. From the analysis of variance, it is concluded that the polymer concentration of the solution and the working pressure affected the fiber diameters more strongly than other parameters.

Front Cover: A novel, commercially viable one‐pot gyratory process which allows polymeric nanofibers to be tailor‐made to structural specifications has been discovered. Its superiority is in the fact that it allows the simultaneous use of four process control parameters; composition, rotation speed, feed flow rate, and pressure. Process design and extensive trials elucidate the very significant prowess and potential of the new process in the production of nano‐fibrous structures for diverse applications where both random and aligned fibrous structures with and without beads are desired. This is reported by Xianze Hong, Suntharavathanan Mahalingam, and Mohan Edirisinghe, in article number https://doi.org/10.1002/mame.201600564.

Pressure-coupled infusion gyration (PCIG) is a novel promising technique for economical and effective mass production of nanofibres with desirable geometrical characteristics. The average diameter of spun fibres significantly influences the structural, mechanical and physical properties of the produced fibre mats. Having a comprehensive understanding of the significant effects of PCIG experimental variables on the spun fibres is beneficial. In this work, response surface methodology was used to explore the interaction effects and the optimal PCIG experimental variables for achieving the desired morphological characteristics of fibres. The effect of experimental variables, namely solution concentration, infusion (flow) rate, applied pressure and rotational speed, was studied on the average fibre diameter and standard deviations. A numerical model for the interactional influences of experimental variables was developed and optimized with a nonlinear interior point method that can be used as a framework for selecting the optimal conditions to obtain poly-ethylene oxide fibres with desired morphology (targeted average diameter and narrow standard deviation). The adequacy of the models was verified by a set of validation experiments. The results proved that the predicted optimal conditions were able to achieve the average diameter that matched the pre-set desired value with less than 10% of difference.