'Perfect' Invisibility Cloak Hides from Microwaves
Student Nathan Landy holds a model of an invisibility device he made with a Duke University professor, David Smith.
CREDIT: Duke/Pratt School of Engineering
Researchers have created a new "invisibility" device that hides small objects from microwave detectors such as radar. Unlike previous microwave invisibility cloaks, it doesn't reflect of the incoming waves, so the illusion is perfect, the BBC reported.
The device has some limitations. For one, it only makes objects invisible from microwave detectors aimed at one specific angle. "It's like the card people in Alice in Wonderland," David Smith, a Duke University materials scientist, told the BBC. "If they turn on their sides you can't see them but they're obviously visible if you look from the other direction." Smith created the device with a graduate student, Nathan Landy.
The technique for making the device also isn't applicable to a visible light, which means it can't make an invisibility cloak that shields objects from being seen by the naked eye.
Nevertheless, being invisible to microwave sensors could be useful to the military, the BBC reported. Cellphones and radar both detect microwaves, so microwave invisibility would be important to hiding planes, boats and tanks in the future.
The new cloak isn't exactly ready to hide a tank yet, however. So far, Smith and Landy have shown that the device is able to hide a cylinder 3 inches (7.5 centimeters) in diameter and a little less than half an inch (1 centimeter) tall.
The experiment is a step forward in a string of efforts to make a practical invisibility device. In 2006, Smith and a team of physicists were among the first scientists to propose, theoretically, how invisibility devices should work. The team made the world's first, imperfect microwave invisibility device later that year.
"The cloak we demonstrated in 2006 as a kind of microwave device would be very poor, but this one gets us to something that could be potentially useful," Smith said.
Smith and his colleagues published their latest work yesterday (Nov. 11) in the journal Nature Materials.