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American Association for the Advancement of Science

Invisibility 'cloak' hides objects from microwaves

Ground plane cloak, zoomed in on bump showing unit cells.

Researchers have created an invisibility cloak of sorts, though it looks more like a yellow bathmat than Harry Potter's famous cloth.

The material doesn't actually hide things from the visible light portion of the electromagnetic spectrum. But, it can conceal an object from electromagnetic radiation in the microwave range.

Ground plane cloak, zoomed in on bump showing unit cells.

David Smith of Duke University, one of the scientists who developed this material, hopes that someday his team can adapt this type of material to work against visible light.

A cloaking device that just works against microwaves could still be very useful, though. For example, it might eventually be possible to cover objects that block cell-phone RF signals with this type of material, allowing the signals to reach their destination.

The researchers' setup includes a flat mirror, which by itself would reflect a beam of incoming microwaves. A small object, also covered in a mirror-like coating, is placed on the mirror, creating a reflective bump. Then, the cloaking material covers the whole surface, like a rug.

Without any cloaking device, this bump in the rug would cause a beam of microwaves to scatter. But, the cloaking material, which is called a "metamaterial" has special properties that reflect the beam as if it had hit a flat surface instead of a bump.


The researchers describe this cloaking device in the 16 January 2009 issue of the journal Science.