Robert J. Lang (US)
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Textes par Julie De Saedeleer
Origami: from airbags to the medical and space industries
1. The purpose of airbags
What do origami and airbags have in common? Much more that you would think!
Vehicle airbags are the result of lengthy research. In the event of a high-speed crash, the occupants of a vehicle can be thrown sideways or towards the windscreen. In airbag-equipped vehicles, as soon as a crash is detected, an electrical sensor activates an explosive charge that inflates airbags, in order to protect the occupants and soften the impact. Fatality and serious injury rates have plummeted since the widespread installation of airbags in vehicles.
Evidently, airbags serve a very important purpose. They must be able to inflate in a few milliseconds and be sufficiently sturdy to stop a rapidly accelerating body.
Smashing against a fully inflated airbag would feel like hitting concrete, and can cause just as much damage as no airbag at all. In addition, these devices must be suitable for a large variety of body sizes, from children to large adults, and for different speeds and impact angles. Indeed, automobile manufacturers need to design airbags that work for a wide range of conditions.
In other words, airbag design is a very precise science which requires extensive testing. Computer simulations are an additional, critical part of the design phase, and key if you want to avoid crashing too many vehicles during tests. Most simulations use a combination of different techniques with unearthly names, such as nonequilibrium thermodynamics (for the detonation).
2. Airbag folding
Folding is done is two stages: going from a 3-dimensional airbag to a flat shape (two dimensions) and then tucking it into the steering wheel.
First, you divide up the surface of the airbag into many tiny triangles, you then calculate the position and orientation of each triangle as the airbag inflates. You need to take into consideration the elasticity of the material, the expansion and cooling of the inflating gases, the shape of the airbag, the external forces exerted upon it, etc. Simulating an inflating airbag is an extremely complex process, and the companies that specialize in it (such as EASi Engineering GmbH) must be experts in computational geometry, physics, engineering, and thermodynamics.
The shape of the airbag is critical; spherical, oblong (like a rugby ball) or even donut-shaped, all these shapes provide different amounts and distribution of cushioning. A significant part of the study of airbags includes determining how efficiently these various shapes work. Of course, all airbag simulations start with the airbag folded up into a small packet and tucked into a simulation steering wheel or dashboard. As a result, the simulation of an inflated airbag needs to start with a simulation of a folded-up airbag.
This is where origami comes in. The fundamental challenge for all origami designers is to go from a 3-D polyhedron to a flat shape. Robert J. Lang has developed this field of study by using computational algorithms. This branch of computational origami is called “tree theory”. The challenge is to flatten a set of polygons so that their edges remain aligned to one another. In origami, the polygons are all part of a single square of paper. The algorithm, called the “universal molecule”, is directly applicable to the airbag problem.
The application of origami for airbags continues to be an active field of study for many research laboratories.
Origami applications left and right…
Problem: How to fold a map so that
- Only a section is visible without having to completely unfold the map?
- And to go from one section to the next in the least amount of folding motions?
A solution: Use a folding technique called “waterbomb base”.
Divide the map into 16 squares and fold each square as shown above.
In 1995, Japanese scientists used origami to fold and unfold solar panel arrays for satellites in the Space Flight Unit (SFU).
The solar array was folded into a parallelogram on land, and then launched and deployed in space. The folding technique used is called MIURA-ORI, in honour of its inventor.
Folded material can be spread out in one motion by pulling on its opposite ends. It is commonly used for road maps.
Given that energy in space is valuable, this technique ensures rapid unfolding in a single motion and, as a result, minimum energy consumption.
Telescopes of the future: Eyeglass
Problem: NASA and ESA aim to send large telescopes (with lenses up to 25 in diameter) into space in order to study faraway galaxies, and astronomical events.
The largest launchers, however, measure five to six meters in diameter.
Solution: Use origami techniques to fold the telescope lens in order to transport it in a launcher and deploy it in space.
Enter Robert J. Lang: he will work closely with the Lawrence Livermore National Laboratory in the United States to build folding models for different-size lenses. The telescope will be named Eyeglass.
In 2002, a telescopic lens measuring over 3 meters in diameter was constructed. When folded origami style, it was 1.2-meter in diameter and shaped like a cylinder. In 2005, another 5-meter prototype lens was constructed.
In the future, it may be possible to fold 100-meter telescope lenses into 3-meter diameter cylinders, all thanks to origami.
Uses in the medical and optical industries
The origami waterbomb folding technique is used to make stents, tiny cylindrical structures that doctors place in a blocked artery or vein in order to enlarge it.
Previously folded and introduced with a catheter, stents are then deployed to improve blood flow.
The first stent was made in 2005 and remained in the patient’s body permanently.