14 DAY TRIAL // Researchers at Duke University who are currently working on new ways of diverting large portions of the visible light spectrum through artificial so-called “invisibility cloaks,” announced recently that a functional prototype could be available in less than six months, if the pace of their innovation continued to remain high. They are currently playing with metamaterials, which are fabrics endowed with special properties that derive directly from their physical structures. It makes no difference what chemical materials the compounds are made of, as long as a few basic principles are followed strictly.
"I think that within six months it's certainly viable [a cloak for visible light]. A large number of folks are looking at it, and I think it's a matter of coupling the right material to the right device," says DU professor David Smith, the lead author of a new paper published in the journal Science.
He explains that the microscopic surface of a material being used has to be much smaller than that of the light wavelength it's being subjected to, in order for invisibility to occur. Basically, the smaller the surface of materials, the shorter wavelengths of light it can deflect. In their experiences with microwaves and infrared lighting, small waves of light simply float around the cloaked object, and then meet up on the other side, creating an optical illusion that tells the brain the object is not there.
Because visible light has very short wavelengths, it's technological limitations that prevent the construction of suitable materials to be used as cloaking devices. But advancements in nanotechnology make it easier to construct ever smaller structures, which could, in theory, be able to shine light away from them, and back to the source. If that happens, the eye perceives a bump, for example, as a flat surface, and the optical illusion is extremely convincing, especially if you don't know what's there.
"We are just scratching the surface. There are hundreds of possible applications for this. We just need to think creatively about how it can be used," concludes Boston College professor William Padilla, who is currently working on developing a metamaterial capable of hiding objects in the terahertz range.
The main advantage of the new technology is that it's very cheap. To cover an object the size of a cell phone, the circuitry involved costs only tens of dollars, and not millions, as it would be expected. However, there are also limitations to the new concept. The objects can currently be hidden in just 2 dimensions, and all their sides must be covered in metamaterials. But these limitations could soon go away, opening the door for a brand new class of applications.