Ultrasound-Enhanced Electrospinning (USES) is a needle-free electrospinning technique, that employes focused ultrasound to generate fibers with tunable diameters. The focused ultrasound creates one or multiple acoustic protrusions on the surfaces of polymer solutions that act as the initiation sites for the electrospinning process. The present work investigates the possibility to vary the mesh porosity (fibers’ spatial density) of the USES-spun fibers. The USES experiments were conducted by using two polymers (polycaprolactone [PCL] and polyvinylpyrrolidone [PVP]), and by comparing electrospinning with low cycle number (low-energy per pulse) and high pulse repetition frequency (PRF) vs. high cycle number (high-energy per pulse) and low-PRF. The USES process was recorded with a high-speed camera, the results of which showed a distinction between the fiber jet branching at low-intensity vs. high-intensity. Scanning electron microscopy (SEM) images of the fiber matrices also showed that the fiber samples spun at high-intensity were visually more porous than at low-intensity. The differences in porosity will be quantified with a mercury porosimeter.
