Free-Standing 3D Invisibility Cloak Made
Researchers have successfully cloaked a three dimensional object, specifically a cylindrical tube, according to the Institute of Physics. Invisibility cloaks and other items have been described in myth and legend for thousands of years, but only recently with metamaterials has this seemed possible. Metamaterials are man-made materials with properties not found in nature, such as a negative index of refraction. The first invisibility cloak used these to hide an area from microwaves, and this new creation also operates on microwaves, but uses a different approach.
Normally an object is visible because light hits it and is scattered, or reflected, back to our eye which perceives the signal. The traditional metamaterial hid an area by bending light around it, like a highway going around a city instead of through it. This new cloak though uses plasmonic metamaterials which do not redirect the light around the object. Instead the light which reflects off the object and the cloak cancel each other out.
This is a major step towards real 3D invisibility cloaks, but for now is more a proof-of-concept for the regular person. As stated earlier, this only will hide an object from microwaves, specifically those around 3.1 GHz. Fortunately the use of plasmonic metamaterials gives the cloak a moderately broad bandwidth, which is not the case with regular metamaterials. Also, the effect is not limited to the specific shape of a cylinder but should also work on asymmetric and other oddly shaped objects. The size of the cloak though is limited by the wavelength of the light it operates on. An invisibility cloak using this technology that works on visible light would only be micrometers in size. This could still be useful for hiding microscope tips, like those used in biomedicine, but won’t hide a house or person.