NC State Researchers Develop Technique To Scale Up Nanofiber Production

Researchers at North Carolina State University (NC State) have developed a nanofiber production
technique that can significantly increase output compared with traditional needle electrospinning
(TNE) and allow industrial-scale production of nanofibers comparable in quality to those formed
using TNE.

The research team includes Dr. Russell E. Gorga, associate professor, Textile Engineering,
Chemistry and Science, and program director of Textile Engineering; Dr. Laura I. Clarke, associate
professor, Physics; Dr. Jason Bochinski, research assistant professor, Physics; and Nagarajan
Thoppey Muthuraman, graduate research assistant. The team reported its findings in a paper titled
“Edge electrospinning for high throughput production of quality nanofibers,” published in the
journal “Nanotechnology.”

Nanofibers can be integrated in nonwoven fabrics used in filtration, energy storage, tissue
regeneration and other applications. TNE creates high-quality, relatively inexpensive nanofibers,
but the process is time-intensive and not very efficient. More efficient technologies are
available, but Gorga said there have been limitations, including inconsistent nanofiber diameters,
associated with various methods.

“We have been trying to come up with a process that is not sensitive to the type of solvent
or polymer system used,” Gorga said. In experiments conducted using equipment designed and
fabricated in-house, the team worked with two polymer types that had different viscosities and
solvent volatility.

The technique involves electrospinning from the edge of a bowl filled with a polymer
solution whose surface is hit with a short, high-voltage burst that causes simultaneous formation
of jets that migrate to approximately equidistant positions on the bowl’s edge and spin nanofibers
onto a cylindrical collector surrounding the bowl. The technique produced 40 times the number of
nanofibers produced using TNE and showed potential for even higher output.

Nanofibers produced ranged from 100 to 200 nanometers (nm) in diameter, and Gorga said the
process can be tuned to produce a specified diameter. “One caveat of high-throughput technologies
is that some of the data show they’re not really producing submicron-diameter fibers. We don’t want
to compromise the diameter because there’s a push to go even smaller – to 50 nm or even 10 nm.”

The project received funding from the National Science Foundation and NC State’s Faculty
Research and Professional Development Fund.

September/October 2011