Invisibility Cloak Steps Closer to Harry Potter


Advances in cloaking keep moving this field closer to reality. A team of researchers at Duke University  have managed to make a small cylinder invisible to microwave radiation. Because this device doesn't reflect any of the microwaves, as other devices do, the illusion is perfect. The technique could be useful to the military for hiding objects that are transmitting microwaves and could also work to improve radio communications.

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The researchers, Nathan Landy and David R. Smith, created a material, called a metamaterial, that bends long-wavelength light -- radio waves -- along its edges so that anything behind it is visible, but anything surrounded by it isn't. In 2006, Smith and his colleagues were among the first scientists to propose a theoretical cloaking device and then later that same year, built an imperfect invisiblity device.

In this latest work, Smith and Landy created a surface with tiny corrugations that bend the radio waves in such a way that when the waves hit an object, they are bent around it, rather than reflecting or getting absorbed. The technique makes the object invisible to microwave sensors.

Although the device doesn't reflect back any microwaves, it still has room for improvement. The light corrugations bend the microwaves in such a specific way that if one rotated the device, more of the cylinder would come into view. (The cylinder would appear two-dimensional from some angles). Landy told Discovery News that you wouldn't really be able to see the cylinder (or any other object) at all because there would be a lot of reflections from inside the "cloak." So it would probably look more like a bright mirror.

That means that for radar, it isn't very useful, since the orientation is so specific. Making this kind of metamaterial work in visible light would also be very hard to do, because the tiny corrugations would have to be a lot smaller.

Credit: Duke University

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