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Materials

A material that shrinks when heated

Qiming Wang A composite structure that shrinks 0.6% in volume at 282º CelsiusQiming Wang

Scientists joined a stiff, slow-expanding copper-based material and a more elastic, faster-expanding polymer, using a special 3D printing process, and produced tiny star-shaped structures with interconnected struts, each about the size of a sugar cube. The internal struts were made of the more malleable elastic material while the frames were formed from the more rigid one. They then heated the structures to 282º Celsius. The result was surprising: the structures bent in on themselves rather than expanding, which is how most solid materials behave when exposed to heat. The experiment was conducted by engineers from the University of Southern California, the Massachusetts Institute of Technology (MIT), and other U.S. institutions (Physical Review Letters, October 21, 2016). According to the authors, the structures shrank about 0.6% in volume. This change may seem insignificant, but the composite material’s curious property may prove useful in many areas, like the space, construction, and computer industries.

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