Philip Bradford: Putting Nanofibers to Work in Novel Ways
By Alyson Tuck
The average person would look at the bag of carbon nanotubes in Dr. Philip Bradford’s office at the Wilson College of Textiles and see an unimpressive pile of black powder. But to Bradford, associate professor of Textile Engineering, Chemistry and Science, those nanofibers are a treasure trove of untapped applications. Bradford’s research aims to make carbon nanotubes in unique ways for novel applications, making fighter jets stronger, batteries more conductive and air filters more effective. And that’s just the beginning.
Carbon nanotubes — hollow, tube-shaped nanofibers made of pure carbon — carry properties that make them a superstar among fibers. As if being ultralight, flexible and among the strongest man-made materials weren’t enough, they have a secret weapon: They are electrically conductive. This unique trait for a fiber, Bradford explained, opens up new areas of research and a world of interesting applications where electrical conductivity would create a superior product.
From Carbon to Fabric
In his Wilson College of Textiles lab, Bradford (B.S. Textiles Engineering ’05, M.S. Textiles Engineering ’07, Ph.D. Materials Science and Engineering ’10) and his team of graduate students, postdocs and undergraduate lab assistants grow carbon nanotubes to use in their research. While producing carbon nanotubes isn’t groundbreaking, Bradford’s process and the characteristics of his particular fibers are.
Bradford has developed a technique for making extremely long nanotubes, up to 5 mm. Though that doesn’t sound long, this diameter-to-length ratio is similar to that of a 30-foot long human hair. This impressive length allows Bradford to make fabric-like material from these fibers without adding binders that would dilute their exceptional properties. In addition to being long, Bradford’s carbon nanotubes are very clean, which allows the nanotubes to stick together in strong sheets, and eventually fabric as large as 15 square inches.
The ability to make these nanotubes that we can draw into sheets has been critical for our research because it really does set us apart from other research groups.
Bradford’s advances in carbon nanotube production leave him with an intriguing question: How can we use it? His research group is currently exploring a number of areas — composites, sensors, electrodes, filtration and foam-like material — that take advantage of the fiber’s special mechanical and conductive properties. This work is funded by the Air Force Office of Scientific Research, American Chemical Society, Eastman Chemical and the North Carolina Space Grant.
Because carbon nanotubes are extremely expensive to produce, Bradford doesn’t expect to see his materials popping up in his bike frame, the battery inside his laptop or in his home air filters. Instead, he imagines carbon nanotubes included in composites that construct the wing of a fighter jet, making it stronger, lighter and more resistant to lightning strikes. He imagines barrier fabrics made from carbon nanotubes effectively filtering aerosol nano-particles. He imagines electrically conductive carbon nanotube fabrics used as a scaffold for more efficient batteries in critical medical devices.
“Nanotechnology is currently being integrated into many of the things that we use every day,” said Bradford. “As the price of carbon nanotubes goes down, they will start showing up in many more applications.”
In 2016, Bradford received funding from the Young Investigator Research Program (YIP), administered by the Air Force Office of Scientific Research to help explore the uses of foam-like structures made from carbon nanotubes. This award aims to assist outstanding early career investigators in creatively pursuing science and engineering research. Bradford is the first researcher in the Wilson College of Textiles to receive this prestigious award. Over the next three years his research team will be experimenting with production and treatment of the foam and how it can be used in aircrafts for energy absorption, filtration, vibration dampening and thermal protection.
Driving Creative Research
Bradford expects — and receives — results from the six graduate students and postdoctoral researchers in his group. Aside from being the manpower that drives his research areas, his students help fuel the creativity behind their solutions. They all work with carbon nanotubes as their base material, but they are focused on different applications. Bradford uses weekly meetings as a forum for his students to present their findings and challenges, to bounce ideas off each other and to look at their base material from a fresh perspective.
Bradford gives his students enough direction to keep them on task, but enough freedom to explore. Because he knows from experience that sometimes novel discoveries are the result of a curiosity-driven side experiment.
“I try to get them to think outside the box and try to be creative and try new things,” Bradford said. “A lot of times you find something most interesting when you’re not meaning to.”
The foam-like material Bradford is now researching was one of those creative surprises. A graduate student was experimenting with carbon nanotube sheets and decided to see what happened if he started winding the material around and around on top of itself. To his delight, it got thicker with each layer. The team then developed a process to carbon treat the resulting structure and found it had remarkable resiliency, while still keeping its multifunctional properties.
That’s how you learn about the new material or new process that you started making. Sometimes we make a hypothesis and try something, and it gives us a good result. Sometimes we try to get creative and try something new and then try to explain why it happened.
Developing Tomorrow’s Problem Solvers
Bradford has been a leader in the Wilson College of Textiles since he entered as a Centennial Scholar his freshman year. Now with three NC State degrees and tenure under his belt, Bradford is committed not just to his research, but to teaching the next generation of problem solvers. In the Summer Textile Exploration Program, which first introduced Bradford to the College when he was a teenager, he aims to pass along his passion for textiles to high school students. And whether it is in his undergraduate classes, his lab, or as advisor to the Textile Engineering Society, Bradford gives his students the tools to solve problems they might face in any field.
“If you develop someone who knows how to solve problems the right way and knows how to think critically, they can solve any problem,” he said. “Figuring out how to solve a problem is sometimes more important than the final result.”
Bradford was named Outstanding Teacher for the Wilson College of Textiles in 2013.