The dc invisibility cloak has a thickness of just one unit cell and can cloak an object nearly perfectly. The inset shows an enlarged view of the cloak’s resistor network. Credit: Wei Xiang Jiang, et al. ©2013 American Institute of Physics

Nearly perfect, ultrathin invisibility cloak could have wide practical applications

January 17, 2013 by Lisa Zyga

(Phys.org)—Researchers have created a dc invisibility cloak made of a metamaterial that not only shields an object almost perfectly, but at 1-cm thick is also the thinnest cloak ever constructed, reaching the ultimate limit of thinness for artificial materials. As the first invisibility cloak that combines both near-perfect performance and extreme thinness, it could open the doors to practical applications. In the past, invisibility cloaks have been too large to be used in many real-world applications.

The researchers, led by Tie Jun Cui at Southeast University in Nanjing, China, have published their paper on the ultrathin but nearly perfect invisibility cloak in a recent issue of Applied Physics Letters.

The key to making a material that can prevent another object from being seen—or from being detected by electromagnetic waves in any way—is to control two material parameters: electric permittivity and magnetic permeability. Electric permittivity corresponds to the degree to which a material permits the formation of an electric field within itself, while magnetic permeability corresponds to the degree to which a material can be permeated by a magnetic field.

As the researchers explain, a perfect invisibility cloak must have a permittivity and permeability that are both strongly anisotropic (directionally dependent) and inhomogeneous (made of different materials). A metamaterial with these parameters is currently beyond the reach of current technology. However, by loosening these strict requirements, researchers have been able to fabricate metamaterials that mimic these properties and can be used as imperfect invisibility cloaks.

Read more: Nearly perfect, ultrathin invisibility cloak could have wide practical applications — phys.org.

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