May 12, 2013
Researchers Demonstrate Thermal Invisibility Cloak
redOrbit Staff & Wire Reports — Your Universe Online
A team of French and German researchers has designed and successfully tested a prototype “invisibility cloak” capable of hiding objects from heat, according to research published in Friday´s edition of Physical Review Letters.
Robert Schittny of the Karlsruhe Institute of Technology in Germany, one of the researchers behind the project, explained to BBC News that the device is designed so the heat has an easier time travelling around the object rather than moving into the center. However, rather than simply insulating the center of the device from heat, it is designed to make it appear as if it simply is not there.
“You want the heat flow to look as if there were no disturbance at all in the middle, and basically if you want to guide the heat around the central part, it takes a detour, a longer time to go around there,” Schittny told the British media outlet. “Each ring is made so that it specifically compensates exactly this detour that the heat has to make.”
While similar devices have attempted to make objects invisible to light and sound waves, this is the first so-called invisibility cloak to focus on heat. The device was initially outlined by researchers last year, and according to Schittny, the researchers believe it is operating as well as they predicted it would.
“The researchers manipulated heat flow by cutting grooves and holes in a copper sheet and filling them with a rubbery thermal insulator,” explained Don Monroe of the American Physical Society (APS) website Physics. “Their structure consisted of a 5-centimeter-diameter copper disk — the cloaked object — surrounded by concentric copper rings. Each ring was connected to its neighbors by a few thin spokes of copper. This structure allows heat to flow easily around the rings but much more slowly in the radial direction.
“Over large distances, the patterned sheet acts as a ℠metamaterial,´ with average properties that are different from pure copper and that vary in a prescribed way with position,” Monroe added. “The team simultaneously submerged one side of their structure in hot water and the other side in room-temperature water. They used an infrared camera to make a temperature ℠movie´ of the heat flowing across the structure and confirmed the time-varying temperature distribution away from the disk was precisely what would be expected for an unaltered copper sheet.”