The phenom known as wizard Harry Potter may be coming to the end of its book and movie run, but one special effect from the series could become reality in a future theater of war. “Cloak of invisibility” technology is undergoing R&D by the U.S. Army Research Office (ARO).
In his article “Scientists Seek to Hide Combat Forces“ in this month’s issue of SIGNAL Magazine, Technology Editor George I. Seffers discusses metamaterials—artificial, manmade materials with properties designed to avoid detection.
Scientists can use nano-sized metal rods implanted into silicon and arranged to manipulate electromagnetic waves, including light waves in the visible spectrum, and microwave or infrared signals, which are not visible to the human eye. Natural materials like water, glass and air have a refractive index greater than one. Metamaterials have a negative refractive index.
Dr. Richard Hammond, a theoretical physicist leading the ARO’s invisibility effort, says these negative-index materials have opened up a whole new world of physics research:
We realized that if we can make negative-index materials, we can make light behave in almost any way we want. Now, we can do all kinds of things we couldn’t do before.
Through two multidisciplinary university research initiatives, the ARO is working with two scientific teams from Duke University and Purdue University. Duke is studying cloaking materials that work with waveforms outside the visible spectrum, like microwaves or infrared. Purdue is creating an invisibility device for the visible spectrum.
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