Origami — the Japanese art of folding paper — could be at the next frontier in innovative materials.
Practiced in Japan since the early 1600s, origami involves combining simple folding techniques to create intricate designs. Now, Georgia Tech researchers are leveraging the technique as the foundation for next-generation materials that can both act as a solid and predictably deform, “folding” under the right forces. The research could lead to innovations in everything from heart stents to airplane wings and running shoes.
Recently published in Nature Communications, the study, “Coarse-grained fundamental forms for characterizing isometries of trapezoid-based origami metamaterials,” was led by first author James McInerney, who is now a NRC Research Associate at the Air Force Research Laboratory. McInerney, who completed the research while a postdoctoral student at the University of Michigan, was previously a doctoral student at Georgia Tech in the group of study co-author Zeb Rocklin. The team also includes Glaucio Paulino (Princeton University), Xiaoming Mao (University of Michigan), and Diego Misseroni (University of Trento).
“Origami has received a lot of attention over the past decade due to its ability to deploy or transform structures,” McInerney says. “Our team wondered how different types of folds could be used to control how a material deforms when different forces and pressures are applied to it” — like a creased piece of cardboard folding more predictably than one that might crumple without any creases.
The applications of that type of control are vast. “There are a variety of scenarios ranging from the design of buildings, aircraft, and naval vessels to the packaging and shipping of goods where there tends to be a trade-off between enhancing the load-bearing capabilities and increasing the total weight,” McInerney explains. “Our end goal is to enhance load-bearing designs by adding origami-inspired creases — without adding weight.”
The challenge, Rocklin adds, is using physics to find a way to predictably model what creases to use and when to achieve the best results.
Deformable solids
Rocklin, a theoretical physicist and associate professor in the School of Physics at Georgia Tech, emphasizes the complex nature of these types of materials. “If I tug on either end of a sheet of paper, it's solid — it doesn’t separate,” he explains. “But it's also flexible — it can crumple and wave depending on how I move it. That’s a very different behavior than what we might see in a conventional solid, and a very useful one.”
But while flexible solids are uniquely useful, they are also very hard to characterize, he says. “With these materials, it is often difficult to predict what is going to happen — how the material will deform under pressure because they can deform in many different ways. Conventional physics techniques can't solve this type of problem, which is why we're still coming up with new ways to characterize structures in the 21st century.”
When considering origami-inspired materials, physicists start with a flat sheet that's carefully creased to create a specific three-dimensional shape; these folds determine how the material behaves. But the method is limited: only parallelogram-based origami folding, which uses shapes like squares and rectangles, had previously been modeled, allowing for limited types of deformation.
“Our goal was to expand on this research to include trapezoid faces,” McInerney says. Parallelograms have two sets of parallel sides, but trapezoids only need to have one set of parallel sides. Introducing these more variable shapes makes this type of creasing more difficult to model, but potentially more versatile.
Breathing and shearing
“From our models and physical tests, we found that trapezoid faces have an entirely different class of responses,” McInerney shares. In other words — using trapezoids leads to new behavior.
The designs had the ability to change their shape in two distinct ways: "breathing" by expanding and contracting evenly, and “shearing" by deforming in a twisting motion. “We learned that we can use trapezoid faces in origami to constrain the system from bending in certain directions, which provides different functionality than parallelogram faces,” McInerney adds.
Surprisingly, the team also found that some of the behavior in parallelogram-based origami carried over to their trapezoidal origami, hinting at some features that might be universal across designs.
“While our research is theoretical, these insights could give us more opportunities for how we might deploy these structures and use them,” Rocklin shares.
Future folding
“We still have a lot of work to do,” McInerney says, sharing that there are two separate avenues of research to pursue. “The first is moving from trapezoids to more general quadrilateral faces, and trying to develop an effective model of the material behavior — similar to the way this study moved from parallelograms to trapezoids.” Those new models could help predict how creased materials might deform under different circumstances, and help researchers compare those results to sheets without any creases at all. “This will essentially let us assess the improvement our designs provide,” he explains.
“The second avenue is to start thinking deeply about how our designs might integrate into a real system,” McInerney continues. “That requires understanding where our models start to break down, whether it is due to the loading conditions or the fabrication process, as well as establishing effective manufacturing and testing protocols.”
“It’s a very challenging problem, but biology and nature are full of smart solids — including our own bodies — that deform in specific, useful ways when needed,” Rocklin says. “That’s what we’re trying to replicate with origami.”
This research was funded by the Office of Naval Research, European Union, Army Research Office, and National Science Foundation.
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By unlocking a new type of origami-inspired folding, a recent physics study could lead to advances in everything from heart stents to airplane wings. (Adobe Stock)
