Invisibility cloak moves a step closer

Light steer

After generations of being effectively invisible to the opposite sex, physicists have finally laid down blueprints for a functioning invisibility cloak. Light or other electromagnetic radiation could be bent around objects covered in exotic materials, making it appear as though they aren't there, a team reports in Science Express.

The theory relies on metamaterials, which get their electromagnetic properties from their structural mix, rather than directly inheriting those of the substances composing them.

The idea is that we now have technology to manipulate the surface of metamaterials on the nano scale, meaning light can be directed very precisely around an object, making it imperceptible to an observer. Researchers at Imperial College and Duke University did the sums, and found that an invisibility cloak should be possible.

Duke professor David R Smith said: "The cloak would act like you've opened up a hole in space. All light or other electromagnetic waves are swept around the area, guided by the metamaterial to emerge on the other side as if they had passed through an empty volume of space."

Invisibility would not be the only application, of course. Metamaterials could be used to improve the transmission of any kind of electromagnetic signal around obstacles, or they could be tuned to steer sound waves for perfect acoustics.

Earlier this month, other researchers detailed an alternative cloaking method using "superlenses", but stressed that their technique would work only for tiny specks of matter.

The metamaterial approach is based on sound, old-school physics. Smith said: "[The maths is] nothing that couldn't have been done 50 or even 100 years ago. The theory has only now become relevant because we can make metamaterials with the properties we are looking for."

The plan now is to validate the predictions with experiment. Smith said the team, funded by Defense Department research organ DARPA, are well on their way.®

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