Back Issues

JUL/AUG 2013  

Follow us:

Find MICROmanufacturing on TwitterFind MICROmanufacturing on FacebookFind MICROmanufacturing on YouTubeMICROmanufacturing RSS feed

Spin controlled: Texas company offers improved way to spin nanofibers

FtrIssueGroup

July/August 2013 Volume 6 Issue 4

FtrAuthorGroup

By William Leventon

Contributing Editor

(609) 926-6447

wleventon@verizon.net

By using force in the same way as a cotton-candy-making machine, a small U.S. firm has become a force in the world of nanoscale fiber fabrication.

At its manufacturing facility in the city of McAllen, at the southern tip of Texas, FibeRio Technology Corp. makes equipment for turning out fibers smaller than 1µm in diameter. Compared to larger fibers, mats of these nanofibers offer much greater surface area, as well as improved properties such as tensile strength, porosity, thermal resistance and electron transfer. These attributes can improve the performance of products used for filtration, drug and cosmetic delivery, wound care and insulation, among others.

L1000.tif

Forcespinning machines use centrifugal force to produce nanofibers. Image courtesy FibeRio Technology.

Nanofibers are typically made using established processes such as electrospinning, which forms fibers using an electric field, and melt blowing, which relies on heated air jets. These processes have significant downsides, reports FibeRio, including high start-up and operating costs and low fiber yields.

Frustrating yields

The journey to improved nanofiber making began some years ago, when the low yields of electrospinning equipment were frustrating the students of Dr. Karen Lozano, a professor at the University of Texas-Pan American (UTPA), Edinburg, Texas. “The yield of a typical lab-scale electrospinning apparatus is like 0.1 gram per hour, and the students were getting a little disappointed,” Lozano said. “So I was thinking, ‘There has to be another way.’” (See Front Page on page 4 for more information on Dr. Lozano.)

Inspiration for “another way” came from an unusual source: cotton candy. The sugary treat caught Lozano’s attention at a circus she attended with her children. Afterwards, she bought a cotton candy machine from a local store and brought it to her lab, where she made some cotton candy and gave it to her students. Besides enjoying the treat, she and her students saw that if they could make nanofibers in the same way that the machine made fine strands of candy, yields would be much higher than those of electrospinning. What’s more, they would no longer have to worry about safety hazards, such as the high voltages and large quantities of corrosive solvents required by the electrospinning process.

With the candy machine in mind, a Lozano-led research team developed a process called Forcespinning. The technology relies on centrifugal force to produce fine strands of material. The force is generated by a motor-driven shaft, which rotates a component called a spinneret on a vertical axis. Orifices dot the outer wall of the spinneret reservoir, which holds material in liquid form.

Dr.%20Lozano.tif

Dr. Karen Lozano, inventor of the Forcespinning process. Image courtesy Josue D. Esparza, UTPA.

When the spinneret is rotated at high speed, centrifugal force and hydrostatic pressure combine to eject jets of liquid material through the orifices. As a jet spray of material exits an orifice, the aerodynamic environment and the inertial force of the rotating spinneret stretch the material into a nanoscale strand. Eventually, a web of nanofibers accumulates in a collector surrounding the perimeter of the spinneret.

Forcespinning users report the creation of fibers with diameters ranging from around 500nm down to 45nm, according to FibeRio.

Birth of a company

To commercialize Forcespinning, FibeRio was founded in September 2009. While retaining her university position, Lozano agreed to serve as the company’s chief technology officer. That left the business side of the operation in the hands of the new CEO, Ellery Buchanan, and the vice president of marketing and business development, Kial Gramley, who learned about Forcespinning while working in UTPA’s technology transfer department.

Having decided that the best course of action was to sell Forcespinning equipment, the two men immediately began the search for funding. The endeavor was made difficult by the poor economic conditions that lingered following the 2008-2009 financial crisis. The funding effort, though lengthy, was successful. FibeRio closed its first round of financing in August 2010.

After that, work on product designs went into high gear. These efforts soon bore fruit, allowing FibeRio to ship its first laboratory and industrial Forcespinning machines in 2011.

‘Groundbreaking’ machines

Buchanan believes the company’s machines are “groundbreaking,” due in part to the rates at which they can turn out tiny fibers. Nanofiber production “is now commercially viable on a cost basis because our machines make enough nanofibers fast enough that they can be used in applications that were unthinkable using electrospinning or other technologies,” he said.

teflon-drops.tif

A superhydrophobic Teflon nanofiber mesh made via Forcespinning. Colored water droplets bead on the nanofiber surface. Image courtesy FibeRio Technology.

PA6-F0828-YB0013.tif

Nylon nanofibers made via Forcespinning. Image courtesy FibeRio Technology.

According to Buchanan, Forcespinning is the only technology that allows both melt and solution processing to be performed by a single tool. In solution spinning, the material to be spun into nanofibers (usually a polymer) is dissolved in a solvent. Melt spinning, on the other hand, is a solvent-free process used when the material to be spun can be melted. In these cases, heat is applied to the spinneret reservoir. When using the FibeRio machine, melt spinning yield is 100 percent, while solution spinning produces about three times the polymer concentrations of electrospinning, according to Buchanan.

As for cost, Gramley claims Forcespinning is only 10 to 25 percent of the cost of competitive fiber-production techniques. Unlike melt blowing, Forcespinning doesn’t require high-velocity, heated air to form nanoscale fibers, eliminating a significant cost from the manufacturing process. When solution spinning is used, Forcespinning requires much lower concentrations of costly solvents than electrospinning, while also eliminating the ionic additives and dielectric salts needed by the electricity-based technique, thereby increasing material purity.

On the downside, Gramley pointed out that Forcespinning is only in its infancy, so the body of knowledge about the technique is miniscule compared to the knowledge built up over the years about electrospinning and melt blowing. On the other hand, he added, “this can be a great opportunity for our customers to take this new platform and develop new processes or work with materials that have never been spun before, and establish a competitive advantage through intellectual property.”

Industry versus the lab

In industrial settings, Forcespinning machines often apply a nanofiber coating to a substrate that measures at least a meter wide. In many cases, Gramley explained, the substrate provides mechanical strength, while the nanofibers provide enhanced performance characteristics related to their large surface area and improved properties desired by the user. The flat, fiber-coated substrates can be rolled up and also cut into different shapes to produce an end product.

spinneret diagram

How forcespinning works.

Industrial customers use Forcespinning machines in continuous-processing applications. Laboratories, on the other hand, do batch processing, which requires less material.

According to Gramley, FibeRio’s laboratory machines are used to determine if different materials can be turned into nanofibers. To give researchers the ability to work with a range of materials, laboratory machines allow greater variability in operating parameters. For example, Gramley noted, the heating temperature of the lab system can go up to 450° C, while continuous-production equipment can only reach about 350° C.

FibeRio’s laboratory machines start at around $100,000, while the company’s industrial-scale systems can cost up to $5 million, depending on size and configuration.

Possible Forcespinning materials include organic and inorganic polymers, ceramics and metals. Each material requires “a special recipe” to work in a Forcespinning machine, said Lozano, who develops the processes for new materials. This recipe includes ingredients such as process temperature, solvent concentration, and spinneret speed and design. To meet the requirements of different applications, spinnerets vary in size, weight, materials and aerodynamic design, as well as in orifice size, shape and number.

Because each material requires a tailored process, there’s a limit to FibeRio’s ability to develop processes for new materials. Today, the company is focusing mainly on organic polymers. Buchanan said his company is also taking steps toward developing higher-temperature technology for melt spinning polymers that could one day be used to process different types of metals.

Another material-related development involves a high-grade polyester material called polybutylene terephthalate. According to Gramley, FibeRio is working on industrial-scale melt spinning of PBT into nanofibers, which currently can’t be done. He thinks PBT nanofibers will be in demand as a replacement for polyethylene terephthalate in both filtration and nonwoven products, mainly because of its superior chemical and thermal resistance.

More developments

In addition, Buchanan said, FibeRio is trying to boost the capacity of its industrial machines to go after “some very high-capacity markets,” such as filtration, nonwovens and textiles. To meet the needs of these markets, he added, the firm is developing machines that can process substrates up to 5.5m wide at speeds up to 400m/min.

A privately held firm, FibeRio doesn’t reveal specific information about sales or profitability. Buchanan did say, however, that the company is “growing very fast,” adding that it had recently doubled the size of its manufacturing plant.

He also noted the company completed a third round of fundraising that involved all the original investors, including the University of Texas and the state of Texas. “You don’t attract those kinds of investments if your financial future doesn’t look bright,” he said, adding that the firm has raised more than $18 million so far.

To hear Buchanan and Gramley talk, the future of their technology looks bright as well. One application they feel has big potential is tissue engineering. With its porous nature and large surface area, a nanofiber mesh can be used to replicate the extracellular matrix that provides structural support for animal cells.

What else might the future hold for these tiny fibers spun like cotton candy? “If you want to talk about products being worked on in laboratory and academic settings,” Gramley said, “you really wouldn’t believe us if we told you.” µ

FtrAuthorAbout

William Leventon is a New Jersey-based freelance writer. He has a M.S. in Engineering from the University of Pennsylvania and a B.S. in Engineering from Temple University. Telephone: (609) 926-6447. E-mail: wleventon@verizon.net. Telephone: (609) 926-6447. E-mail:  wleventon@verizon.net.