First ultrathin invisibility cloak created to hide arbitrarily shaped 3D objects

A real-life invisibility cloak may be just five to 10 years away, according to researchers who have made a small object of arbitrary shape disappear using an ultra-thin cloak that looks like a coat.

In recent years, scientists have continued to make advances to the invisibility cloak concept. However, existing designs have substantial limitations that render them unwieldy, unadaptable to different environments, or limited to cloaking only very tiny objects.

In the new study, researchers devised a "skin cloak" barely 80 nanometers in thickness, or only one thousandth of a human hair thickness, using brick-like blocks of gold nanoantennas.

The "skin cloak" can conform to the shape of a three-dimensional object about the size of a few biological cells and conceal it from detection with visible light, they reported Thursday in the U.S. journal Science.

Although this cloak is only microscopic in size, the principles behind the technology should enable it to be scaled-up to conceal macroscopic items as well, said Xiang Zhang, professor of the University of California Berkeley and a world authority on metamaterials -- artificial nanostructures engineered with electromagnetic properties not found in nature.

"This is the first time a 3D object of arbitrary shape has been cloaked from visible light," Zhang, also director of U.S. Department of Energy's Lawrence Berkeley National Laborator Materials Sciences Division, said in a statement.

"Our ultra-thin cloak now looks like a coat. It is easy to design and implement, and is potentially scalable for hiding macroscopic objects."

Zhang told Xinhua by phone that "we are perhaps just five to 10 years away from the practical realization of a real-life invisibility skin cloak."

Invisibility skin cloaks may find potential applications in technologies such as high resolution optical microscopes and superfast optical computers. On the microscopic scale, they may prove valuable for hiding the detailed layout of microelectronic components or for security encryption purposes. At the macro scale, they could prove useful for 3D displays.

"The fact that we can make a curved surface appears flat also means that we can make a flat surface appear curved," Zhang said. He also noted that with ultrathin metasurface skin masks, wrinkles, pimples and even belly fat could be made to disappear.

It is the scattering of light -- be it visible, infrared, X-ray, etc., -- from its interaction with matter that enables us to detect and observe objects. The rules that govern these interactions in natural materials can be circumvented in metamaterials whose optical properties arise from their physical structure rather than their chemical composition.

For the past ten years, Zhang and his research group have been pushing the boundaries of how light interacts with metamaterials, managing to curve the path of light or bend it backwards, phenomena not seen in natural materials, and to render objects optically undetectable. In the past, their metamaterial-based optical carpet cloaks, however, were bulky and hard to scale-up.

In the Berkeley study, when red light struck an arbitrarily shaped 3D sample object measuring approximately 1,300 square microns in area that was conformally wrapped in the gold nanoantenna skin cloak, the light reflected off the surface of the skin cloak was identical to light reflected off a flat mirror, making the object underneath it invisible even by phase-sensitive detection.

The cloak can be turned "on" or "off" simply by switching the so-called polarization of the nanoantennas, Zhang added. Endit