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We present an experimental visualization study of centrifugal spinning, which is a novel method of producing nanofibers. The investigation was conducted using Newtonian and viscoelastic fluids to study the effect of viscoelasticity, driving force, and the flow rate on the initial thinning behavior, jet contour shapes, and radii. Boger fluids based on Newtonian polybutene and viscoelastic polyisobutylene were utilized as test fluids in the current study. Our results reveal that increasing the viscoelasticity leads to a faster initial thinning of the polymer jet. However, the effect is strongly coupled with the rotation speed, and due to a faster increase in extensional viscosity for highly viscoelastic fluids, the thinning slows down with the increase in the angular velocity. Initial thinning is shown to be faster for the lower flow rates. Viscoelasticity and centrifugal force have a significant influence on the jet contour radii. The maximum radius will decrease for more viscoelastic fluids, and with the increase in angular velocity due to the development of the elastic hoop stress. The comparison of experiments with the discretized element modeling with the FENE-P model confirms the model predictive potential for the thinning behavior. Finally, the centrifugal spinning experiments are compared to electrospinning in order to observe a qualitative similarity.

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Employing circumferentially uniform air flow through the sheath layer of the concentric coaxial nozzle, the gas-assisted electrospinning (GAES) utilizes both high electric field and controlled air flow to produce nanofibers. The ability to tailor the distribution of various nanofillers (1.85-12.92 vol% of spherical SiO and Si nanoparticles) in a polyvinyl alcohol jet is demonstrated by varying airflow rates in GAES. The distribution of nanofillers is measured from transmission electron microscopy and is analyzed using an image processing technique to perform the dispersion area analysis and obtain the most probable separation between nanoparticles using fast Fourier transform (FFT). The analysis in this study indicates an additional 350% improvement in dispersion area with the application of high but controlled airflow, and a 75 percent decrease in separation between nanoparticles from the FFT. The experiments in this study are in good agreement with a coarse-grained MD simulation prediction for a polymer nanocomposite system subjected to extensional deformation. Lastly, utilizing the sheath layer air flow in production of Li-battery anode material, a 680 mAh g improvement is observed in capacity for nanofibers spun via GAES compared to ES at the same Si NP loading, which is associated with better dispersion of the electrochemically active nanoparticles.

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