May 13, 2009
It seems that the old adage ”I’ll believe it when I see it with my own two eyes” is not as reliable as it used to be. A significant amount of research is being conducted into cloaking devices, which will allow objects to become “invisible” at certain frequencies.
Research shows that this can be achieved, at certain frequencies, by guiding the waves around the object and once past, allowing them to resume their original path. This is possible using a new material known as a metamaterial, which can steer light in a predetermined way. Various teams around the world have built invisibility cloaks which hide objects from view in both the microwave and optical bands.
Now, researchers from the Hong Kong University of Science and Technology have taken this research one step further, to create the illusion of one object being another. Imagine trying to make a table look like a chair. The trick is to create a material in which the permittivity (a property which describes a materials ability to affect electric fields) and permeability (how a material reacts to a magnetic field) are complementary to the values in the region containing the object we wish to hide, in this case the table. In this application the term “complementary” means that the material will cancel out the effect the region of space contained within the cloak (containing the table) has on a plane wave passing through it. Therefore, the plane wave incident on the cloak will be bent around the region of space (by the metamaterial) and reconnected on the other side, thus giving the illusion that the table has disappeared – SWEET 
. Now comes the second part of the trick – to make the table look like a chair. This is achieved by have a second material – a transformational material, which will distort the plane wave in the same manner as the chair. Thus, anyone looking at this region would see the chair and not the table, which is contained within the cloak.
This is such a cool idea, and will undoubtedly lead to some crazy applications. Philosophically I’m still not sure of the implications of this type of research. There are so many useful security applications which would benefit this type of technology, but there are also other, less legal applications. Is this really a technology which should be given to the public? In either case, it would be difficult for the technology not to reach the general public. As soon as this technology reaches the security forces or the military it will be replicated and assimilated by countless companies and sold over the internet.
This is a research area which I will keep a keen eye on. The theory is pretty simple, and the idea appealing. It will be interesting to see where this research will lead. For further information, take a read of the research paper.