Mass production method could open up nano-fibre applications

Engineers and researchers at North Carolina State University and one of its start-ups have reported a method that can produce unprecedented amounts of polymer nanofibres, which have potential applications in filtration, batteries and cell scaffolding.

In a paper published online in Advanced Materials, the NC State researchers and colleagues from industry, including NC State start-up company Xanofi, describe the method that allows them to fabricate polymer nanofibres on a massive scale.

The method – fine-tuned after nearly a decade of increasing success in producing micro- and nanoparticles of different shapes – works as simply as dropping liquid solution of a polymer in a beaker containing a spinning cylinder.

Glycerin is used to shear the polymer solution inside the beaker along with an anti-solvent like water. When you take out the rotating cylinder, said Dr. Orlin Velev, Invista Professor of Chemical and Biomolecular Engineering at NC State and the corresponding author of the paper describing the research, you find a mat of nanofibres wrapped around it.

When they first started investigating the liquid shearing process, the researchers created polymer microrods, which could have various useful applications in foams and consumer products.

“However, while investigating the shear process we came up with something strange. We discovered that these rods were really just pieces of ‘broken’ fibres,” Velev said in a statement. “We didn’t quite have the conditions set perfectly at that time. If you get the conditions right, the fibres don’t break.”

NC State patented the liquid shear process in 2006 and in a series of subsequent patents while Velev and his colleagues continued to work to perfect the process and its outcome.

First, they are said to have created microfibres and nanoribbons as they investigated the process. “Microfibres, nanorods and nanoribbons are interesting and potentially useful, but you really want nanofibres,” Velev said. “We achieved this during the scaling up and commercialisation of the technology.”

Velev engaged with NC State’s Office of Technology Transfer and the university’s TEC (The Entrepreneurship Collaborative) program to commercialise the discoveries. They worked with entrepreneur Miles Wright to start Xanofi to advance the quest for nanofibres and the most efficient way to make mass quantities of them.

“We can now create kilograms of nanofibres per hour using this simple continuous flow process, which when scaled up becomes a ‘nanofibre gusher,’” Velev said. “Depending on the concentrations of liquids, polymers and anti-solvents, you can create multiple types of nanomaterials of different shapes and sizes.”

“Large quantities are paramount in nanomanufacturing, so anything scalable is important,” said Wright, the CEO of Xanofi and a co-author on the paper. “When we produce the nanofibres via continuous flow, we get exactly the same nanofibres you would get if you were producing small quantities of them. The fabrication of these materials in liquid is advantageous because you can create truly three-dimensional nanofibre substrates with very, very high overall surface area. This leads to many enhanced products ranging from filters to cell scaffolds, printable bioinks, battery separators, plus many more.”

The research – described in a paper titled Scalable Liquid Shear-Driven Fabrication of Polymer Nanofibreswas funded by the US National Science Foundation’s Accelerating Innovation Research program.

NC State’s researchers Stoyan Smoukov, Tian Tian and Eunkyoung Shim co-authored the paper, as did Narendiran Vitchuli, Sumit Gangwal, Miles Wright and Pete Geisen from Xanofi Inc.; Manuel Marquez from Ynano Llc.; and Jeffrey Fowler from Syngenta Co.