Core-sheath polymer nanofiber formation by the simultaneous application of rotation and pressure in a novel purpose-designed vessel

Forming polymeric core-sheath nanofibers is gaining prominence owing to their numerous potential applications, most notably in functional scenarios such as antiviral filtration, which is attracting significant attention due to the current COVID pandemic. This study has successfully designed and constructed a novel pressurized gyration vessel to fabricate core-sheath polymer nanofibers. Several water-soluble and water-insoluble polymer combinations are investigated. Both polyethylene oxide and polyvinyl alcohol were used as the core while both poly(lactic acid) (PLA) and poly(caprolactone) (PCL) were used as the sheath; PLA and PCL were used as core and sheath, in different instances; respectively. The fluid behavior of the core-sheath within the vessel was studied with and without applied pressure using computational fluid dynamics to simulate the core-sheath flow within the chamber. A high-speed camera was used to observe the behavior of jetted solutions at core-sheath openings, and the best scenario was achieved using 6000 rpm spinning speed with 0.2 MPa (twice atmospheric) applied pressure. The surface morphology of core-sheath fibers was studied using a scanning electron microscope, and focused ion beam milling assisted scanning electron microscopy was used to investigate the cross-sectional features of the produced fibers. Laser confocal scanning microscopy was also used to verify the core-sheath structure of the fibers, which were further characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. Thus, using a variety of polymer combinations, we show, both theoretically and experimentally, how core-sheath fibers evolve in a vessel that can serve as a scalable manufacturing pressurized gyration production process.