The Origami of Thin Films
March 17, 2015, Fargo, N.D. — While many of us crumple up a sheet of paper into a ball in frustration, physicist Andrew Croll views it as something quite different. The structure of the bends and folds created, as well as those found in origami—the art of folding paper into beautiful objects—may help solve a larger scientific puzzle. Instead of paper, Croll and his research team at NDSU use polymer films known as “thin films,” or extremely thin slivers of layers of material—tens of nanometers thin. A nanometer is 10,000 times smaller than the width of a human hair.
The research team is examining how randomly crumpled and purposefully folded polymeric materials could eventually be used as lightweight structural components in aerospace applications. The secrets of these bends and folds could provide information that leads to lightweight and strong components to make aircraft and spacecraft more efficient. Determining what happens when thin films bend or fold are complex questions.
To investigate these questions, Croll, assistant professor of physics, is receiving a $305,046 three-year award from the U.S Air Force Office of Scientific Research (AFOSR). The competitive award is being made through the prestigious Young Investigator Research Program. The grant also will provide funds for undergraduate and graduate students to work as part of the research team. A North Dakota Governor’s School student also may be selected to participate in the research.
Croll’s proposal is titled “Crumpled and Prescriptively Folded Polymer Films for Advanced Lightweight Materials.” If more efficient aircraft and spacecraft are to be manufactured, new materials that are both rigid and lightweight must be developed. The structure and properties of the materials must be defined. The stuff they are made of is studied. Scientists probe and measure how the materials respond to various forces to determine how they might respond in real world applications. The research by Croll and his team is being conducted to establish a basic understanding of the focused bending and stretching that leads to high strength-to-weight ratios in folded polymer films.
Carbon fiber composites and nanocomposites are currently one of the leading light-weight, yet rigid, materials available for aircraft design. Goals of the research by Croll include determining the basic physics behind the growth of more complex crumpled objects that can easily hold considerably higher loads.
“The research has the potential to shift development from costly new materials to the creative use of existing materials,” said Croll.
“We are trying to build an understanding of how and why thin polymer films feel strong when bent in particular ways,” said Croll. “For example, a piece of paper is flimsy, but if crumpled into a ball, it can be surprisingly strong. Paper can also be folded into intricate, functional shapes, as any origami artist knows. If the strength of the bends making up origami and crumpled balls of paper, for example, were completely understood, then engineers can use bends as ‘structural building blocks,’” he said.
The research holds potential for military and other applications. Crumpled films form a very strong, light-weight building material with the potential for 'active' material responsiveness. Lightweight materials drive down fuel costs.
Materials that are responsive could create new technologies. The advanced materials that could be created might be the stuff of science fiction movies brought to life. Applications could include solar cells that deploy themselves in space, materials that are rigid in one direction and soft in another, or materials that can fold up and “hide” or walk.
“For these advanced materials to be a reality, the basic building blocks must be completely understood,” said Croll.
He also is examining the connections between bending and failure of thin polymer systems. Potential applications for this research might include flexible electronic systems. Such systems could be embedded in wearable performance monitoring equipment. Conformal antennas that are used to conform into the curving skin of an airplane, ship or other vehicle, are another potential application. Folded, deployable solar panels could be another eventual outcome of this research.
The award funding to Croll announced by the U.S. Air Force Office of Scientific Research is one of 57 grants at 43 research institutions and small businesses. Croll’s work was selected out of 200 proposals. The Young Investigator Research Program is open to researchers in the early stages of their careers who show exceptional ability and promise for conducting basic research.
Other awardees include representatives from Princeton, California Institute of Technology, Stanford University, Arizona State University, Cornell University and Rensselaer Polytechnic Institute, among others.
Croll joined the faculty at NDSU in 2010. He completed a post-doctoral fellowship at the University of Massachusetts. He was awarded his Ph.D. in polymer physics from McMaster University, Hamilton, Ontario, Canada. Croll received a bachelor’s degree in physics from the University of Waterloo, Ontario, Canada.
While physics might not be the topic of everyday conversation, Croll makes efforts to bridge that gap. He previously spoke at a Science Café, discussing Why Stuff Sticks: geckos, bugs, nanotechnology and the quest for really good duct tape.
Sharing research information with the public is important, Croll said. He also finds it fun. “I do it to excite people, to try to share the joy I find in seeing something new. I do it for fun, so I can act ‘not’ my age.”