Scientists create ‘cloak of invisibility’
The “cloak”, based on a British design concept, measures less than five inches across and only responds to radar waves.
But within five years there might be devices powerful enough to make whole vehicles “vanish” — including battlefield tanks.
An invisibility cloak blueprint was produced in May by Professor John Pendry, a physicist at Imperial College London.
Just five months later, scientists working with him in the US have put the idea into practice.
The concept involves bending visible light, or other forms of electromagnetic radiation such as radar, around an object.
An observer looking at the cloaked object will see light deflected from behind, making it ‘disappear’.
Scientists cannot yet steer visible light in this way. But the US researchers at Duke University in Durham, North Carolina, have built a prototype device that is invisible to radar.
The key to the design is “metamaterial” — specially manufactured material that can “grab” electromagnetic radiation and deflect it smoothly.
In the prototype, a series of fibreglass concentric rings embedded with conducting copper wire loops were used.
A 2.5cm wide copper ring at the centre performed the role of the “hidden” object.
Prof Pendry said: “This cloaking device is just a demonstration showing that you can get radiation where you want it to be.
“There’s still some development to do, but I would have thought that in five years you’d be seeing some sort of practical realisation of this technology.
Dr David Schurig, from the university’s electrical and computer engineering department, said: “The waves movement is similar to river water flowing around a smooth rock.”
In order to “tune in” to the radiation, its properties had to vary in specific ways from point to point. A computer was used to calculate the precise pattern of elements.
Prof Pendry’s early work was funded by the US Defence Advanced Research Projects Agency (Darpa).
The technology also has non-military applications, such as manufacturing “perfect” camera and telescope lenses, or protecting sensitive electronic equipment from radio interference.
