An ultrasound-enhanced electrospinning for generating multilayered nanofibrous structures

The ability to modify nanofiber diameter on the fly can give an opportunity to create advanced nanofiber materials with complex design. Such flexibility provides possibilities to produce materials with gradient structures (physical and mechanical), desirable in wound healing and tissue engineering applications. We investigated a needleless ultrasound-enhanced electrospinning technique (USES) for generating multilayered nanofiber mats. The aim was to gain understanding of how the process parameters of USES affect the thickness and morphology of nanofibers. Levels of three process parameters were changed in a stepwise manner, permitting us to create multiple layers of nanofibers with different thickness. In the first test we found that by increasing the ultrasound burst rate from 150 Hz to 1800 Hz, the average nanofiber diameter increased by 90 nm. The second test showed a 170 nm decrease in average fiber diameter when ultrasound burst count was increased from 1200 Hz to 10000 Hz. The third set of experiments showed a minimal increase in fiber diameter when the duty cycle was decreased from 11.5% to 1.8%. Fourier transform infrared spectroscopy revealed no process induced transformations when generating nanofibers from aqueous PEO solutions with the USES device. In conclusion, USES enables us to modify nanofiber thickness in real time, and consequently, to generate multiple fiber layers having different average fiber diameter. Therefore, we believe that USES as a novel needleless electrospinning method holds promise for manufacturing of multilayered (gradient) nanofiber structures for wound healing and tissue engineering applications. [Display omitted]