The first invisibility cloak has been demonstrated by David Schurig of Duke University and colleagues. This is the first practical realization of a theoretical concept proposed earlier this year by John Pendry from Imperial College London (see CERN Courier September 2006 p11).
The team created a shield in the form of a "metamaterial" made of 10 concentric fibreglass rings, each printed with a copper pattern. Working in the microwave region, the cloak interacts with electromagnetic waves to give the impression that both the cloak and the object within are nothing more than free space. It reduces both the shadow of the object and the radiation reflected, basically bending the incoming microwaves to make it appear that the shielded object is not there. The effect is rather like when water flows round a smooth rock and no disturbance is visible downstream.
The device tested was some 12 cm across and provided invisibility in two dimensions. Now the team plans to work towards a 3D device. So far the technique works only in a narrow frequency band in the microwave region, but shorter wavelengths could follow.
Further reading
D Schurig et al. 2006 Science 314 977.