NC State Researchers Develop Technique To Scale Up Nanofiber Production

Researchers at North Carolina State University (NC State), Raleigh, N.C., have developed a
nanofiber production technique that will enable significantly increased output compared with the
traditional needle electrospinning (TNE) method and allow industrial-scale production of nanofibers
comparable in quality to those formed by needle electrospinning.

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, a graduate research assistant working with Gorga and Clarke. The team reported
their findings in a paper titled “Edge electrospinning for high throughput production of quality
nanofibers,” published last month in the journal “Nanotechnology.”

Nanofibers can be incorporated into nonwoven fabrics used in filtration, energy storage,
tissue regeneration and other applications. The TNE production method creates high-quality,
relatively inexpensive nanofibers, but the time-intensive process is somewhat inefficient. Other
technologies have been developed that provide a more efficient production method, but, according to
Gorga, there have been limitations associated with various methods, including inconsistencies in
the diameters of the nanofibers produced.

“We have been trying to come up with a process that is not really sensitive to the type of
solvent or polymer system used,” Gorga said, noting that any solution should be able to work using
the process developed by the NC State research team. 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 newly developed technique involves electrospinning from the edge of a bowl filled with a
polymer solution whose surface is hit with a short, very high-voltage burst that causes the
simultaneous formation of jets that then migrate to the edge of the bowl to approximately
equidistant positions and spin nanofibers onto a cylindrical collector surrounding the bowl. The
technique produced 40 times the number of nanofibers produced using TNE and demonstrated the
potential for even greater production volumes.

Gorga said the technique produced nanofibers ranging in diameter from 100 nanometers (nm) to
200 nm and added that the process can be tuned to produce a specified diameter. “One of the caveats
of high-throughput technologies is that some of the data show they’re not really producing fibers
at submicron diameters. We don’t want to compromise the nanofiber diameter because there’s a large
push to go even smaller — to 50 nm or even 10 nm.”

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

August 16, 2011