The Invisibility Cloak Is Becoming Reality
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Last November, researchers from Duke University reported designing an invisibility cloak that can hide a 7.5-centimeter cylinder, while Nanyang Technological University scientists have shielded a cat and goldfish using cloaking devices made from conventional materials rather than metamaterials. But these cloaks work only in a single 2-D plane, so the object is hidden only to those looking from a certain direction.
So engineers at the University of Toronto designed a cloaking device made of a layer of tiny antennas that collectively radiate an electromagnetic field, cancelling out any waves that reflect off the hidden object over a wide range of wavelengths. Right now, the cloak only works for radio waves, but the antennas could theoretically be re-tuned to cancel out light, sonar and other waves. The cloak can mask objects of any size and can even deceive detection devices by transmitting signals to make the hidden object seem bigger, smaller or in a different location. Besides military applications, such as hiding vehicles or conducting surveillance operations, the technology could also be used to cloak buildings that interfere with cell phone and other signals.It may be years before we see a full-sized cloak that’s truly invisible to the naked eye, experts say. For one thing, the microscopic structures that make up the metamaterial need to be smaller than the type of wave they’re bending. It’s also hard to engineer materials that bend all wavelengths of light.