AN ILLUSION device that makes one object look like another could one day be used to camouflage military planes or create "holes" in solid walls.

Don’t believe everything you see. Metamaterials could provide the ultimate illusion (Image: Edgar Mueller/Rex Features)

The idea builds on the optical properties of so-called metamaterials, which can bend light in almost any direction. In 2006, researchers used this idea to create an "invisibility cloak" that bent microwaves around a central cavity, like water flowing around a stone. Any object in this cavity is effectively invisible.

Now a group of researchers has gone a step further. "Invisibility is just an illusion of free space, of air," says Che Ting Chan, a physicist at the Hong Kong University of Science and Technology and a co-author of the study. "We are extending that concept. We can make it look like not just air but anything we want."

Instead of bending light around a central cavity, the team has worked out the mathematical rules for bending light in other ways. For example, a material could be designed to bend light in the same way as a spoon would. So the light hitting the material would be distorted to make it look as if a spoon were there.

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