That invisibility cloak Harry Potter throws around himself to hide in plain sight soon may be fact, rather than fiction. Researchers at the University of Texas in Austin have demonstrated one — sort of.
The researchers hid an 18 cm cylindrical tube from microwaves by putting it in a shell of plasmonic metamaterial.
Metamaterials are artificial materials engineered to have properties that may not occur in nature.
Plasmonic metamaterials are negative index metamaterials, meaning they are, in essence, invisible at a certain frequency range.
How You See It, How You Don’t
When light strikes an object, it bounces off the object’s surface. We see an object when the light bouncing off its surface reaches our eyes.
However, plasmonic metamaterials circumvent that process by scattering light at a frequency that cancels out the rays of light bouncing off them. That means the light from a surface covered with a plasmonic metamaterial won’t reach your eyes from any angle.
The researchers cloaked the tube used in the test with a shell of plasmonic metamaterial, then directed microwaves toward it and mapped the resulting scattered light both around the tube and further away.
The cloak was most effective when the microwaves were at a frequency of 3.1 GHz and issued over a moderately broad bandwidth.
Rushing Toward Invisibility
The experiment follows on from a similar one conducted at the university in August.
The next step for the researchers is to succeed in cloaking a three-dimensional object in visible light. However, that may be much more difficult.
“The object concealed was 18 cm, and the length of a microwave is from 1 mm to one meter, and the wave was tuned to the object in order to get it to vanish,” Rob Enderle, principal analyst at the Enderle Group, told TechNewsWorld.
“If you need to have that much control over an object, it likely would be just as easy and far cheaper to have people look at something else,” Enderle said. “You should hire a magician and not a scientist.”
A research team member did not respond to our request for further details.
For Whose Eyes Only?
Research into methods of rendering objects invisible has been going on for years, and efforts in this field appear to have speeded up.
Earlier this month, researchers at Cornell University demonstrated a way to cloak an event in time.
In October, scientists from the University of Texas in Dallas demonstrated a cloaking device that works best underwater and has an on/off switch. They used sheets of carbon nanotubes — sheets of carbon one molecule thick shaped into cylindrical tubes.
There’s considerable interest in this field because “there’s massive defense money available for technology like this, and research lives off defense spending,” Enderle said.
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One afternoon in 2005 I was driving south between Austin and San Marcos, Tx on Interstate 35 and saw the reflection of an airplane in the distance in front of me. As I continued driving I would see it intermittently. It was flying slower than I (70 mph) off to the side of the highway about a hundred feet high, and as I slowly caught up with it it I could sometimes see its outline but only when it turned slightly. I realized that it was smaller than a conventional airplane, maybe 10′ long, and that it was almost invisible! It had to be a remotely operated drone. I mentioned this to a friend who is a US Air Force pilot and he just changed the subject!