Academic and industrial research on nanofibres is an area of increasing global interest, as seen in the continuously multiplying number of research papers and patents and the broadening range of chemical, medical, electrical and environmental applications. This in turn expands the size of the market opportunity and is reflected in the significant rise of entrepreneurial activities and investments in the field. Electrospinning is probably the most researched top-down method to form nanofibres from a remarkable range of organic and inorganic materials. It is well known and discussed in many comprehensive studies, so why this review? As we read about yet another "novel" method producing multifunctional nanomaterials in grams or milligrams in the laboratory, there is hardly any research addressing how these methods can be safely, consistently and cost-effectively up-scaled. Despite two decades of governmental and private investment, the productivity of nanofibre forming methods is still struggling to meet the increasing demand. This hinders the further integration of nanofibres into practical large-scale applications and limits current uses to niche-markets. Looking into history, this large gap between supply and demand of synthetic fibres was seen and addressed in conventional textile production a century ago. The remarkable achievement was accomplished via extensive collaborative research between academia and industry, applying ingenious solutions and technological convergence from polymer chemistry, physical chemistry, materials science and engineering disciplines. Looking into the present, current advances in electrospinning and nanofibre production are showing similar interdisciplinary technological convergence, and knowledge of industrial textile processing is being combined with new developments in nanofibre forming methods. Moreover, many important parameters in electrospinning and nanofibre spinning methods overlap parameters extensively studied in industrial fibre processing. Thus, this review combines interdisciplinary knowledge from the academia and industry to facilitate technological convergence and offers insight for upscaling electrospinning and nanofibre production. It will examine advances in electrospinning within a framework of large-scale fibre production as well as alternative nanofibre forming methods, providing a comprehensive comparison of conventional and contemporary fibre forming technologies. This study intends to stimulate interest in addressing the issue of scale-up alongside novel developments and applications in nanofibre research.

A new route consisting of simultaneous centrifugal spinning and solution blowing to form polymer nanofibers is reported. The fiber diameter (60–1000 nm) is shown to be a function of polymer concentration, rotational speed, and working pressure of the processing system. The fiber length is dependent on the rotational speed. The process can deliver 6 kg of fiber per hour and therefore offers mass production capabilities compared with other established polymer nanofiber generation methods such as electrospinning, centrifugal spinning, and blowing.

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Solvent–polymer interactions critically influence not only the viscoelasticity and the critical minimum solution concentration required for electrospinning but also the diameter, crystallinity, tensile strength, aspect ratio, and morphology of the electrospun fibers. Hence, a good understanding of the solvents and nonsolvents available and electrospinnable for a polymer of interest is important. The electrospinnability–solubility map uniquely presents the solubility and the electrospinnability of all solvents for a polymer in a single figure. Poly­(ε-caprolactone) (PCL), an important polymer in biomedical applications, has been electrospun in a few conventional solvent systems, but a comprehensive mapping of its solvents for electrospinning has not been performed. Based on 49 common solvents of diverse solubility parameters and functional groups, the spinnability–solubility graph for electrospinning PCL solutions was mapped for the first time to enable a comprehensive understanding of the processability of all solvent choices for electrospinning PCL solutions. Furthermore, to date, many studies have demonstrated the importance of the dielectric constant (relative permittivity) of solvents in solution electrospinning, but few have systematically investigated its influence for a broad range of solvent systems. Based on the comprehensive PCL solvent map, this work studies the influence of dielectric constant of solvent systems on the electrospinning of PCL solutions. PCL (M n = 80 000 g/mol) fiber diameters <100 nm were achieved when the dielectric constant of a solvent system was ∼19 and above, below which fibers or relics of diameters from submicrometer to millimeter range were produced. A detailed investigation was carried out on solvent systems with a calculated range of dielectric constants by mixing acetic acid and formic acidtwo solvents with significantly different dielectric constants but the same functional group and comparable in other physical properties influential in electrospinning. With increasing dielectric constant, the required applied voltage to achieve stable jetting increased, the frequency of bead-on-string morphology decreased, and the interfiber spacing increased without affecting the total mass of fibers spun per unit time. In addition, the dissolution and electrospinnability of poor or nonsolvents of PCL were tested at temperatures 10 °C or higher than the ambient temperature. A unique and novel morphology of electrospun fibers within electrosprayed relics was generated for the first time when electrospinning PCL in 2-ethoxyethyl acetate, a nonsolvent at an ambient temperature of 20–22 °C and a partial solvent of PCL at an elevated temperature of above 30 °C.