The art of origami usually requires dextrous fingers to turn a flat sheet into an intricate 3D shape. Now it’s got considerably easier, thanks to a material that can fold up on its own.
A team led by Robert Wood of Harvard University and Daniela Rus and Erik Demaine at the Massachusetts Institute of Technology made a square sheet of glass fibre 4 centimetres wide and patterned with 32 triangular tiles. The seams between triangles are made from flexible silicon rubber and a “shape memory” alloy foil.
Each foil was given a memory by folding it in two and holding it in a vice as it is heated to 420 °C for 30 minutes. When unfolded and then allowed to cool, the foils retained a memory of the fold. They would re-adopt the shape when heated above a “transition” temperature of 70 °C.
The researchers used origami simulator software to work out the sequence of folds required to create two simple structures – a paper aeroplane and a boat. They then sent a current through the foils, heating them above their transition temperature and so causing them to fold again. By controlling precisely when a current was applied to each foil, they ensured that the flat sheet folded into its pre-designed shape inside 20 seconds (see video).
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Although the team has so far managed to create only simple origami shapes, they say the technique could make tailor-made objects if the size of the triangles is reduced and their number increased. “Imagine foregoing all the tools in your toolbox and instead using a stack of self-folding sheets to produce the tools and structures you need for a particular job,” says Wood.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0914069107
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