Linda Poon is a staff writer at CityLab covering science and urban technology, including smart cities and climate change. She previously covered global health and development for NPR’s Goats and Soda blog.
A new metamaterial out of Harvard can shrink, expand, and fold completely flat with little outside force and no damage.
A new kind of metamaterial—material that changes how it behaves according to its structural design—created by scientists at Harvard University could change the way we think about pop-up housing. Engineers there used origami to design a sturdy, shape-shifting, 3D material that can shrink, expand, and fold completely flat with little outside force and without getting damaged. (Existing metamaterials inspired by origami are typically created from folding 2D sheets.)
According to Johannes Overvelde, who worked on the project, the material can withstand the weight of an elephant when completely flat. Once all that force is removed, the structure, made of interlocking cubes, pops right back up—no additional energy required.
The secret is in its design, which is inspired by a popular origami technique called “snapology.” Invented by Heinz Strobly, the technique involves weaving thin strips of paper together via connector pieces—or snaps—to create a rigid yet flexible, multi-faceted structure. The structure that Overvelde and his team designed is a 4 x 4 x 4 cube made of 64 individual cells whose edges act as hinges.
When force is applied—in Overvelde’s test case, the force comes from inflating small air pockets embedded on the cells’ hinges, causing them to bend. Depending on how the hinges fold, the shape, stiffness, and volume of the structure can change instantly. The results of this experiment were published last month in the journal Nature Communications.
Although the prototype measures only 50 centimeters square and made of plastic sheets, Overvelde says the design is scalable and would work with other materials. “This could be interesting on a larger architectural scale because, if you start using this material, you might be able to create walls that can open and close,” he tells CityLab.
It could come in handy particularly in building compact and sturdy shelters for disaster victims. “You don’t need to constantly add energy to make it keep its shape; you can just let go and it automatically goes to its expanded state,” he says. Determining exactly what materials (plastic, metal, or something else) are ideal for shelter designs will require further research before the project can be applied to an actual project.
Overvelde and his team aren’t the only researchers experimenting with origami. In September, engineers at Georgia Tech, the University of Illinois, and the University of Tokyo used an origami technique known as Miura-ori to create “zipper tubes” that can also fold flat and withstand a relatively large amount of weight. Indeed, origami, which provides multiple solutions to structural design challenges, has become a popular inspiration for engineers like Overvelde.
“We're trying to come up with new types of material that don't get their properties from its chemistry, but from their shape, their internal geometry,” he says.