Next-generation inflatable buildings keep their shape without constant pressure

In 2016, an inflatable arch caused extensive damage during the Tour de France cycling race when it deflated and collapsed on a cyclist, throwing him off his bike and slowing the race as officials rushed to clear the debris from the road. Officials blamed a passing spectator’s wayward belt buckle for the bow’s collapse, but the real culprit was physics.

Today’s inflatable structures, used for everything from field hospitals to sports complexes, are monostable, meaning they need a constant supply of pressure to maintain their inflated state. Release that pressure and the structure will return to its only stable shape – flat.

But what if these structures had more than one stable state? What if the arc had inflated as steadily as it was flat on the ground?

Now, Harvard researchers at John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed bistable inflatable structures inspired by origami.

The research is published in Nature.

“This research provides a direct path for a new generation of robust, large-scale inflatable systems that remain in place after deployment and do not require continuous pressure,” said Katia Bertoldi, the William and Ami Kuan Danoff professor of applied mechanics at SEAS. and senior author of the article.

Inspired by origami and guided by geometry, the research team developed a library of triangular building blocks that can be flipped or folded flat and combined in various configurations to build closed, multistable shapes.

“We rely on the geometry of these building blocks, not the material properties, which means we can make these building blocks from almost any material, including inexpensive recyclable materials,” said Benjamin Gorissen, a Materials Science and Mechanical Engineering associate at SEAS and co. -First author of the paper.

Bringing their design process to the real world, the researchers designed and built an inflatable shelter measuring 2 by 4 meters from thick plastic sheets.

“You can imagine these shelters being used as part of emergency response in a disaster area,” said David Melancon, a Ph.D. student at SEAS and co-lead author of the paper. “They can be stacked flat on a truck and you only need one source of pressure to inflate them. Once they are inflated, you can remove the pressure source and move to the next tent.”

The shelter can be set up by one or two people, as opposed to the dozens it takes to deploy today’s military field hospitals.

The building blocks of these origami structures can be mixed and matched to create a structure of any shape or size. The researchers built a range of other structures, including an arch, an extendable boom, and a pagoda-style structure. The researchers also designed shapes with more than two stable shapes.

“We’ve unlocked an unprecedented design space of large-scale inflatable structures that can fold flat and maintain their unfolded shape without the risk of catastrophic fracture,” said Chuck Hoberman, the Pierce Anderson Lecturer in Design Engineering at the Graduate School of Design and co-author of the article. “Using inflatable, reversible propulsion to reach hard-walled structural enclosures, we see important applications not only here on Earth, but potentially as habitats for moon or Mars exploration.”