Inspired by the Japanese art of folding: Researchers present a new concept for the production of robust pop-up structures such as shelters. The constructions of connected panels are inflated from the flat state until they lock firmly into place after unfolding. Due to the ingenious arrangement of the elements, the complex constructions then result in stable forms. Compared to previous quick-assembly systems for large structures, the new concept offers decisive advantages and thus has great potential in various areas of application, say the scientists.
Compact and light become large and useful: There are many possible uses for pop-up structures – from mobile shelters and field hospitals to impressive structures at events. However, the previous concepts leave a lot to be desired, as certain properties have so far been difficult to combine. In the case of tent-like structures, the following applies: the more stable and complex the construction, the higher the construction costs. As an alternative, inflatable structures made of flexible materials are therefore already in use. But these structures require constant pressure to maintain their shape. When it falls away, the structure returns to its only truly stable form – limp and flat. The consequences this can have became clear at the Tour de France in 2016: An inflatable decorative arch that spanned the street collapsed due to the loss of pressure due to comparatively slight damage and fell on one of the participants in the bicycle race.
Art of folding cleverly implemented
With this in mind, a team from Harvard University in Cambridge has now devoted itself to developing an alternative concept using compressed air. They were inspired by the Far Eastern art of folding, which had previously served scientists as a model for the design of various structures and processes. The central aspect of origami is that stable three-dimensional objects can be created by cleverly folding flat elements. As part of their study, the scientists have now implemented this system in a clever way.
Using special geometric calculation methods and experiments, the research team developed a system based on triangular basic elements made of solid plastic that are linked by flexible connections. Using special folds, the scientists created constructions from these elements that can assume two stable states: folded flat or unfolded to form a three-dimensional structure. In order to move from one state to the other, a certain resistance has to be overcome. The construction work is done by compressed air, which is fed into the closed structures. It unfolds until the structure locks into a stable state.
Because of the geometric features, air pressure is no longer necessary to maintain the shape. In order to then lay the structure flat again, the researchers suck air out of the construction: With the help of a vacuum pump, the stable 3D state is overcome and the structure can be brought back into its compact form. For demonstration purposes, the team made an inflatable arch that is 60 centimeters high and 150 centimeters wide. They also present the prototype of a tent-like construction that can be unfolded and collapsed using the process. With a width and height of around 2.5 meters, this structure already has practicable dimensions.
“Airy” system with potential
“One can imagine that such accommodations could be used as part of emergency aid in disaster areas,” says first author David Melancon. “They can be stacked flat on a truck and all you need is a source of pressure to set them up. Once they are inflated, you can remove the pressure source and move on to the next tent, ”says Melancon. As a result, shelters can be set up by just one or two people, as opposed to the dozen needed to set up today’s field hospitals, explains the scientist.
As he and his colleagues point out, the elements of the origami structures can be configured to make many different shapes or sizes. There seems to be a lot of leeway when it comes to materials, too: “We rely on the geometric features rather than the material properties, which means we can make these building blocks from many different substances, including inexpensive, recyclable materials,” says co-author Benjamin Gorissen.
Although there is still some development work to be done, the researchers see great potential in their technology: “We have opened up an unprecedented design space for large inflatable structures that can be folded flat and retain their unfolded shape without the risk of catastrophic breakage,” sums up co-author Chuck Hoberman. “We see considerable application potential for these hard-walled coatings, not just on earth. They could also be used, for example, to study the moon or Mars, ”says the scientist.
Source: Harvard John A. Paulson School of Engineering and Applied Sciences, article: Nature, doi: 10.1038 / s41586-021-03407-4