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In 2016, an inflatable arch caused a crash at the Tour de France when it unexpectedly deflated and collapsed on Adam Yates, throwing him off his bike. Officials blamed a spectator’s belt buckle for the accident but the real culprit was physics. Let’s take a look at how it happened and what can be done to prevent it.

Loss of pressure caused the accident in 2016

The inflatable structures used nowadays are monostable, which means they need a constant input of air pressure in order to maintain their inflated state. When they lose that pressure, the structure returns to its only stable form, which is flat on the ground. And this is exactly what happened in 2016 at the Tour de France.

Adam Yates riding for Orica–BikeExchange was sent flying off his bike and the supporting Mavic motorbike was also in trouble. The accident caused a delay in the race as officials scrambled to clear the debris from the road.

Origami-inspired invention

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences decided to put an end to this. They have developed bistable inflatable structures inspired by origami as a potential replacement for the current monostable ones.

“This research provides a direct pathway for a new generation of robust, large-scale inflatable systems that lock in place after deployment and don’t require continuous pressure,” said Katia Bertoldi, senior author of the paper.

The research team developed a library of triangular building blocks that can pop up or fold flat and be combined in different configurations to build closed, multi-stable shapes.

“We are relying on the geometry of these building blocks, not the material characteristics, which means we can make these building blocks out of almost any materials, including inexpensive recyclable materials,” said Benjamin Gorissen, co-first author of the paper.

Bistable inflatable structure brought to reality

The researchers weren’t just writing their ideas down. They took to the real world and built a 240×120 cm inflatable shelter out of thick plastic sheets.

For the Tour, disaster zones, and even space

There are many different use cases that the authors are suggesting. Will we see the bistable structures at the next Tour de France?

“We’ve unlocked an unprecedented design space of large-scale inflatable structures that can fold flat and maintain their deployed shape without the risk of catastrophic rupture. By using inflatable, reversible actuation to achieve hard-walled structural enclosures, we see important applications, not only here on Earth, but potentially as habitats for lunar or Mars exploration,” said Chuck Hoberman, co-author of the paper.

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