Micro-Stereolithography Used to 3D-Print ‘Metamaterial’ Structures that Shrink – Not Expand – When Heated
Interesting bit of reporting here on MIT News about metamaterials whose negative refractive index means they shrink instead of expand as is typical when objects are heated. Researchers at MIT 3D-printed some objects – à la Hoberman spheres – and recognized they shrunk “one part in a thousand, or about 0.6 percent.”
Almost all solid materials, from rubber and glass to granite and steel, inevitably expand when heated. Only in very rare instances do certain materials buck this thermodynamic trend and shrink with heat. For instance, cold water will contract when heated between 0 and 4 degrees Celsius, before expanding.
Engineers from MIT, the University of Southern California, and elsewhere are now adding to this curious class of heat-shrinking materials. The team, led by Nicholas X. Fang, an associate professor of mechanical engineering at MIT, has manufactured tiny, star-shaped structures out of interconnected beams, or trusses. The structures, each about the size of a sugar cube, quickly shrink when heated to about 540 degrees Fahrenheit (282 C).