The problem of scale is unavoidable when talking about applying materials made in a laboratory into an industrial process. It’s one thing to make small transistors with submicron features, but what if you want to coat the entire surface of a jetliner with a conductive nanomaterial?
That’s the kind of problem Namiko Yamamoto is trying to solve.
“I’m from the Aerospace Engineering Department, and what I want to do is apply nano- and micro-engineered materials to airplanes, satellites, or other large structures,” says the assistant professor.
Engineering materials with high quality and functionality at the scale of a microchip or in a thin film is something materials researchers have the expertise to do well, but scaling those processes up to meter and multi-meter lengths is where these laboratory materials run into problems.
The unique properties that occur at the small scale can disappear at larger scale, or the performance of the material degrades with increasing size.
“A lot of the unique properties are coming from nano-scale organization,” she says. “If you want to make them larger, those are going to become hard to control. When you go to larger scales you can’t enjoy the same degree of performance as the small samples.”
In spring 2016, she was awarded just under $380,000 to study scalable manufacturing of multi-functional polymer nanocomposites by the Office of Naval Research.
Yamamoto has worked extensively with carbon nanotubes (CNTs) as a potential conductive-coating nanomaterial for use in protecting airplanes from lightning strikes. These nanotubes were aligned, and thus become efficient electrical conductors, like tiny lightning rods. This approach could lead to considerable weight savings over the currently used metal mesh layer. She originally fabricated such material by first organizing the nanotubes and then infiltrating with a polymer; however, this method was not the most scalable. Now, she first mixes nanoparticles together with polymer, and then organizes the nanoparticles using external oscillating magnetic fields.
“We’ve gained an understanding of the correlation between particle organization and magnetic field frequency,” she explains. The difficulty of magnetic particle assembly is that magnetic particles want to stick together. To control and tailor particle patterns, a means to separate particles is necessary, which can be provided by low-frequency field oscillation.
“There are major research players at Penn State who work with acoustic and electric assembly. I like magnetic because it requires low power, as long as the particles are magnetically responsive.”
If achieved, the conductive nanoparticle network in such coatings can provide pathways to dissipate current or heat to protect electronics or cargo inside airplanes and buildings. The same network can potentially be used as sensors for nondestructive evaluation and system health monitoring. As an example, in her Ph.D. research, Yamamoto and her colleagues embedded CNT networks in aerospace composites. During their mechanical testing, both the CNT networks and the composites broke. This caused the local electrical and thermal conductivity to change as defects formed. By applying a small current, the defect locations would heat up and could be simply detected using a thermal camera.
Yamamoto speculated on other uses for oriented nanoparticles: “It would be cool to apply our knowledge to biomedical applications, like to deliver drugs or to break blood clots. The magnetic assembly method is non-contact, and we can control particle locations, density, speeds, and so forth.”
Recently, Yamamoto has been thinking about the possibility of using magnetic assembly in 3D printing. “Currently, particles and fibers in the ink are organized by the printer nozzle’s movement. If we could incorporate a magnetic field into the printer nozzle, we could organize them separately from the nozzle movement.”
About Prof. Yamamoto
Namiko Yamamoto left Japan as a teenager to come to school in the U.S.
“It takes a lot of energy and guts to study abroad, so you might as well do it when you’re young,” she says. “Living in a foreign country definitely made me grow a lot as a person. It had not been an easy journey, but I have been extremely lucky with friends, teachers, and colleagues.
“I wanted to come to the U.S. because I wanted to be an astronaut. I didn’t realize that I couldn’t apply for an American astronaut slot, because I am Japanese. It shows how much a 17-year-old knows about the world,” she laughs.
At MIT, she chose aerospace engineering over astrophysics as her major, because she realized that her interested are in making things than in observing far away phenomena.
Yamamoto is the principal investigator for the Advanced Composites and Engineered Materials Group and an assistant professor of aerospace engineering. She received her B.S., M.S., and Ph.D. in Aeronautics and Astronautics from MIT. Her post-doctoral training was at Caltech and NASA’s Jet Propulsion Lab. She joined the Penn State faculty in July 2014.
Contact Prof. Yamamoto at email@example.com.