A team of experts creates an invisibility cloak
According to an article published on October 19, 2006 in BBC News, a team of British and American researchers has successfully tested a new invisibility cloak in the laboratory. In tests at Duke University in North Carolina, the device concealed a small copper cylinder from microwaves.
Like visible light waves, microwaves bounce when encountering an object, making their presence evident and creating a shadow. The device works by deflecting the microwaves around the object and returning them to their place on the other side, as if they had passed through an empty space. It is a behavior similar to that of river water, which when it encounters a rock surrounds it to rejoin on the other side.
The layer is made up of 10 fiberglass rings covered with copper elements and is classified as a “metamaterial”: a man-made compound that can be engineered to produce a desired change in the direction of electromagnetic waves. In this way, the metamaterial layer channels the microwaves around the object as if it were water.
In statements made in the BBC article, Prof. Pendry, one of the study's co-authors, states: "These materials have inaugurated a new chapter in electromagnetism."
In the experiment, the scientists first measured the microwaves passing through an unobstructed plane. They then placed a copper cylinder on the plane and measured the disturbances and scattering of the microwaves. Finally, they covered the cylinder with the invisibility cloak and did the calculations again. The coating did not totally prevent disturbances, but it greatly reduced the number of microwaves blocked or deflected.
At microwave frequencies, detection has to be done by instruments, rather than with the human eye. However, making an object vanish before a person's eyes is still science fiction (for now).
In principle, the same theory could be used to hide objects from visible light, but this would require much more complex and minute metamaterial structures, something that scientists have yet to figure out.
According to Pendry, perhaps in 5 or 10 years, when nanotechnology is more advanced, it could be achieved, but not yet today.
Regarding the applications of the study, the researchers affirm that if it is possible to hide an object from microwave waves, it can also be hidden from radar, something interesting from a military point of view.
It could also be used to hide objects from terahertz waves, a system that is being used in many sensor detection technologies; and even from mobile phone frequencies and magnetic fields.
Source: BBC Technology News