These materials morph into 3D shapes in ways that aren’t usually physically possible.
Researchers at Carnegie Mellon University and the Swiss Federal Institute of Technology are working on a technique to use origami-like folding to take advantage of the unique physical properties of auxetic materials, which stretch in two dimensions.
Most materials behave like rubber bands when stretched: they may expand in one direction, but must contract in the other. Auxetic materials stretch uniformly in two dimensions, enabling researchers to create devices that expand in ways that can be useful in medical and other applications. For example, they can form 3D surfaces such as spheres from pieces that are flat.
“We’re taking a flat piece of material and giving it the tendency, or even the desire, to bend into a certain 3D shape,” said Keenan Crane, assistant professor of computer science and robotics at Carnegie Mellon.
In order to do it, they needed to use computation to map how the auxetic materials expand. PhD student Mina Konaković used a 3D digital model and conformal geometry to predict how the auxetic materials would move. She cut hexagonal slits into metal and plastic sheets, giving them auxetic capabilities. A computational tool and a laser cutter were used to determine the right configuration and size of the pieces. After it was done, 3D shapes could be built out of the sheets. The hexagonal slits created triangular elements that rotated relative to the other pieces around them.
It’s still difficult to get the materials to automatically take the shape that they need. Keenan Crane, assistant professor of computer science and robotics at Carnegie Mellon, said in a press release that the ability to get the shapes to automatically expand is still a work in progress. In these initial experiments, the material needed to be pressed into the shape it needed to take.
The researchers suggest that the technique could be used to build medical devices that unfold within the site of a surgery, or solar arrays that can be folded up for their launch into space and then expand on their own. So far, the team has used it to make a high-heeled shoe, a lampshade, a sculpture, and other artistic and functional objects.
The technique will be detailed at the International Conference on Computer Graphics and Interactive Techniques (SIGGRAPH) in California on July 27.
Filed Under: Rapid prototyping