Unfortunately, a Harry Potter-style invisibility cloak capable of concealing whoever wears it from human eyes has yet to be realized. As the BBC noted, current “invisibility cloak” designs can obscure objects only at certain wavelengths of light or microwaves. But researchers in Canada have developed a method that makes a range of objects undetectable to radar – something that could be practical for concealing things like military tanks.
The device, developed by scientists at the University of Toronto, is actually a very thin cloak made of tiny antennas that radiate an electromagnetic field. According to Nature World News, the radar invisibility cloak works by canceling out radio waves bouncing off the object. The system essentially “tricks” radar into overlooking an object it would normally detect.
"We've demonstrated a different way of doing it," George Eleftheriades, a professor at the Edward S. Rogers Sr. Department of Electrical & Computer Engineering at University of Toronto, told Nature World News. "It's very simple: Instead of surrounding what you're trying to cloak with a thick metamaterial shell, we surround it with one layer of tiny antennas, and this layer radiates back a field that cancels the reflections from the object."
To test their invisibility cloak, Eleftheriades and his colleagues successfully concealed a metal cylinder from radio waves with one thin layer of the antenna-laced material. According to researchers, the cloak could eventually be printed to lay flat like a sheet.
"There are more applications for radio than for light," Eleftheriades said. "It's just a matter of technology -- you can use the same principle for light, and the corresponding antenna technology is a very hot area of research."
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Scientists in the U.S. are experimenting with a similar invisibility cloak material. According to the BBC, researchers at the University of Texas at Austin are developing a “broadband” cloak that would conceal objects over a wide range of frequencies using an ultrathin electronic system. But they’re finding that making objects “invisible” isn’t as easy as they’d like it to be.
"When you add material around an object to cloak it, you can't avoid the fact that you are adding matter, and that this matter still responds to electromagnetic waves," Professor Andrea Alu told the BBC. "For example, you might make a cloak that makes an object invisible to red light. But if you were illuminated by white light you would actually look bright blue, and therefore stand out more."