Monday, April 16, 2007


Sheets of plastic that fold into tiny pyramids, boxes and spheres when water is added have been created by French researchers. They think the technique could one day be used to mass-produce the microscopic 3D components used in found inside many different devices from printers to medical sensors.

José Bico and colleagues at the École Supérieure de Physique et de Chimie Industrielles (ESPCI), in Paris, together with a team from the Paris Institute of Technology have shown that water droplets can be used to make flat shapes fold up to create more complex 3D structures.

They add water droplets to flat plastic shapes just a couple of millimetres across. As a droplet evaporates, its volume changes while the surface tension holding it to the sheet remains the same. This pulls the shape into a more complex 3D structure. A time-lapse video shows a triangular shape folding into a pyramid (.mov format).

Bico and colleagues designed sheets to make different shapes. For example, a flower-like pattern produces a sphere, a triangle becomes a tetrahedron and a flat cross shape folds into a cube. They also discovered that varying the thickness of the sheet controls how much a structure folds up and that the effect of surface tension becomes stronger as the size is decreased. Make sure you watch the movie!

[+ movie]
via newscientist

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