How to create shapes from a single sheet of paper? Origami folders know that precise sets of valley folds and mountain folds allow such exploits. “Exploits”, because everyone knows that it is impossible to cover a sphere with a sheet of paper without tearing or bending it. Cartographers also know that it is not possible to draw continents on a globe without distorting them. Going from flat to volume means cheating by bending, bending, deforming…
Physicists from the Paris School of Industrial Physics and Chemistry (ESPCI) have just achieved this performance, but in a way without hands. By inflating a sandwich made up of two planes of inextensible fabric, inside which small channels are cleverly drawn, they obtain a whole catalog of shapes, like this kind of sand rose, but also domes, helices, cylinders , evoking cooling towers of nuclear power plants, gutters, accordions, craters, etc. It is obviously different from the trampoline castles for children on the beaches, because here the uninflated object is very flat at the start.
It’s the researchers’ third technique in the category of generating 3D shapes from flat surfaces. In 2018, their art of inflation was applied in elastomer “sandwiches”. When a long canal is inflated, its walls expand, but its length does not change. If two channels are side by side, they push against each other and absorb this stress by creating a bump or a hollow: the surface deforms. By performing more complex configurations, it is possible to shape the surface as desired. The team had thus created “masks” with nose, mouth and eyes. “But these shapes remained soft, and you couldn’t make them large, because they collapsed under their weight”remember Jose Bicoprofessor at ESPCI.
Collaborations with civil engineering
Two years later, scientists traded elastomers for inextensible waterproof fabrics, which stick together when heated. They draw the channels with a hot tip, which sticks the two planes together. Inflation twists, deforms, curves the surface. Pressure regulates stiffness. They even make a domed “tent” four meters in diameter ! “Of course, our structure was more rigid, but the result is sometimes unpredictable: instead of making a dome, it can swell into a vase! »says José Bico.
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