Thermal invisibility cloak

Heat is passed around the central area of a structured silicon and copper plate from left to right.

BY means of special metamaterials, light and sound can be passed around objects. Researchers at Karlsruhe Institute of Technology (KIT) have now succeeded in demonstrating that the same materials can also be used specifically to influence the propagation of heat. A structured plate of copper and silicon conducts heat around a central area without the edge being affected. The results are presented in the Physical Review Letters.

“For the thermal invisibility cloak, both materials have to be arranged smartly,” says Robert Schittny from KIT. Copper is a good heat conductor, while the silicon material used, called PDMS, is a bad conductor. “By providing a thin copper plate with annular silicon structures, we produce a material that conducts heat in various directions at variable speeds. In this way, the time needed for passing around a hidden object can be compensated.”

If a simple, solid metal plate is heated at the left edge, heat migrates uniformly to the right side. The temperature of the plate decreases from the left to the right. Exactly the same behaviour is exhibited by the new metamaterial outside of the annular structure. No heat penetrates inside. Outside, there is no indication of what happens inside.

“These results impressingly reveal that transformation optics methods can be transferred to the highly different area of thermodynamics,” says Martin Wegener, Head of the Institute of Applied Physics of KIT. Thermal invisibility might be applied in areas needing effective heat management, such as in microchips, electric components, or machines.