Until now, physicists have been unable to fabricate a cloak that could hide macroscopic items at visible wavelengths. Two independent groups have now achieved this feat, by building transparent 'carpet cloaks', made from calcite crystals, that lie over the object to be hidden.
Physicists Shuang Zhang at the University of Birmingham, UK, and John Pendry from Imperial College London has built a calcite cloak that can work in air, hiding objects a few centimetres high.
Nature - Baile Zhang and his colleagues at the Singapore–MIT Alliance for Research and Technology (SMART) Centre in Singapore have built a calcite carpet-cloak that can shield a steel wedge that is 38 millimetres long and 2 millimetres high from red, green and blue visible light3. The team designed their cloak to work under water. "I think that governments could make a lot of use out of a cloak that can hide objects on the seabed — although I won't speculate on exactly what they may want to hide," says team member George Barbastathis, a mechanical engineer also at the SMART Centre.
Both of the calcite carpet-cloaks are much cheaper to make than previous invisibility carpets, which were built using intricately fabricated silicon microstructures and could only conceal microscale objects, says Baile Zhang. "Because they were so difficult and expensive to construct they are difficult to scale up," he says. But the calcite cloak uses naturally occurring materials that cost only about US$1,000 to make and are easy to manipulate. "It's not quite easy enough to make at home, but it's not too far off," says Baile Zhang.
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