An update on the ongoing efforts to create invisibility technology has been bearing some pretty interesting fruit. Earlier this year, scientists at Berkeley announced that they were working on a suit that would be capable of bending light around it. Unlike adaptive camouflage, this technology would not merely broadcast a background image to conceal a soldier, but would render them virtually invisible to the naked eye.
Well guess what? Scientists at Duke University have finally created a cloak that works. Granted, it is only capable of concealing objects on the centimeter-scale, it is the only cloak of its kind that is capable of channeling incident light around itself, creating perfect invisibility. In all previous cases, the devices created reflected a certain degree of incident light, leaving the concealed object disguised but discernible.
In addition to the small scale on which it functions, the cloak has a few additional drawbacks. For now, the Duke invisibility cloak only works with microwave radiation; and perhaps more importantly, the cloak is unidirectional, meaning it only provides invisibility from one very specific direction. But that should hardly matter, seeing as how such a device even exists. With a little time, development, and a big fat DARPA contract, soon we may be seeing cloaking devices that are capable of concealing something as large as a person, a vehicle or even a building.
The Duke cloaking device, pictured at left, is composed of metamaterials – an artificial, man-made material that almost always have a negative refractive index. A negative refractive index allows for the creation of some interesting things, such as superlenses that go beyond the diffraction limit; or in this case, invisibility cloaks. Due to their unusual index, they are capable of refracting light around an object so a viewer does not see the object, but what is behind the object.
But in addition to metamaterials, the compositional materials also need a to be arranged in such a way that the illusion is perfect. After all, a 3D object has multiple sides, and the wearer has to be expected to turn a corner and change direction at some point. All previous designers in this case have struggled to fashion metamaterials that bend waves around corners without causing reflections. In this case, it was researcher Nathan Landy, a Duke University student, who arranged the metamaterials into the shape of a diamond to acheive the desired effect, since diamonds are apparently the best shape for minimizing reflections.
According to the Duke team, the next step is to expand on their design and make their cloak omnidirectional, meaning that it can bend light around the object from all directions. Don’t worry, I’m thinking some rather interested parties (i.e. every high-tech developer and military on the planet) is likely to be knocking on their door real soon!
Source: Extreme Tech