French Researchers Developing Thermal Cloaking Technology
Posted on March 26, 2012
French researchers are taking concepts used in invisibility cloaking and applying them to heat shielding. They are using an idea dubbed "thermal cloaking" to isolate or cloak objects from sources of heat. The method - reported in the Optical Society's (OSA) open-access journal Optics Express - taps into some of the same principles as optical cloaking.
Invisibility cloaks are based on the physics of transformation optics, which involve bending light so that it propagates around a space rather than through it. Sebastien Guenneau and olleagues at France's Centre National de la Recherche Scientifique (CRNS), decided to investigate whether a similar approach might be possible for thermal diffusion.
Though this technology uses the same fundamental theories as recent advances in optical cloaking, there is a key difference. Cloaking research revolves around manipulating trajectories of waves. The biggest difference in their study of heat is that the physical phenomenon involved is diffusion, not wave propagation.
Guenneau says, "Heat isn't a wave - it simply diffuses from hot to cold regions. The mathematics and physics at play are much different. For instance, a wave can travel long distances with little attenuation, whereas temperature usually diffuses over smaller distances."
To create their thermal invisibility cloak, Guenneau and colleagues applied the mathematics of transformation optics to equations for thermal diffusion and discovered that their idea could work. In their two-dimensional approach, heat flows from a hot to a cool object with the magnitude of the heat flux through any region in space represented by the distance between isotherms. The researchers altered the geometry of the isotherms to make them go around rather than through a circular region to the right of the heat source, so that any object placed in this region can be shielded from the flow of heat. This figure above shows that the object in the center of the cloak stays cold, while the heat diffuses elsewhere. The source of the heat is on the left-hand side and at a constant temperature of 100�C, and the material inside the invisibility region remains cold.
Guenneau says, "We can design a cloak so that heat diffuses around an invisibility region, which is then protected from heat. Or we can force heat to concentrate in a small volume, which will then heat up very rapidly."
Shielding nanoelectronic and microelectronic devices from overheating is one of the biggest challenges facing the electronics and semiconductor industries. The researchers say that on a larger scale this new shielding technology could help in the spacecraft and solar industries. The French researchers are developing prototypes of their thermal cloaks for microelectronics, which they say will be ready within the next few months.