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Elena Semouchkina holds the ceramic resonators that enable her to make objects appear invisible in microwave frequencies.
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From
Tolkien’s ring of power in The Lord of the Rings to Star Trek’s
Romulans, who could make their warships disappear from view, from Harry
Potter’s magical cloak to the garment that makes players vanish in the
video game classic “Dungeons and Dragons, the power to turn someone or
something invisible has fascinated mankind. But who ever thought that a
scientist at Michigan Technological University would be serious about
building a working invisibility cloak?
That’s
exactly what Elena Semouchkina, an associate professor of electrical
and computer engineering at Michigan Tech, is doing. She has found ways
to use magnetic resonance to capture rays of visible light and route
them around objects, rendering those objects invisible to the human eye.
Semouchkina
and colleagues at the Pennsylvania State University, where she is also
an adjunct professor, recently reported on their research in the journal
Applied Physics Letters, published by the American Institute of
Physics. Her co-authors were Douglas Werner and Carlo Pantano of Penn
State and George Semouchkin, who works at Michigan Tech and Penn State.
They
describe developing a nonmetallic cloak that uses identical glass
resonators made of chalcogenide glass, a type of dielectric material
(one that does not conduct electricity). In computer simulations, the
cloak made objects hit by infrared waves—approximately one micron or
one-millionth of a meter long—disappear from view.
Earlier
attempts by other researchers used metal rings and wires. “Ours is the
first to do the cloaking of cylindrical objects with glass,” Semouchkina
said.
Her
invisibility cloak uses metamaterials, which are artificial materials
having properties that do not exist in nature, made of tiny glass
resonators arranged in a concentric pattern in the shape of a cylinder.
The “spokes” of the concentric configuration produce the magnetic
resonance required to bend light waves around an object, making it
invisible.
Metamaterials,
which use small resonators instead of atoms or molecules of natural
materials, straddle the boundary between materials science and
electrical engineering. They were named one of the top three physics
discoveries of the decade by the American Physical Society. A new
researcher specializing in metamaterials is joining Michigan Tech’s
faculty this fall.
Semouchkina
and her team now are testing an invisibility cloak re-scaled to work at
microwave frequencies and made of ceramic resonators. They’re using
Michigan Tech’s anechoic chamber, a cave-like compartment in an
Electrical Energy Resources Center lab, lined with highly absorbent
charcoal-gray foam cones. There, antennas transmit and receive
microwaves, which are much longer than infrared light, up to several
centimeters long. They have cloaked metal cylinders two to three inches
in diameter and three to four inches high.
“Starting
from these experiments, we want to move to higher frequencies and
smaller wavelengths,” the researcher said. “The most exciting
applications will be at the frequencies of visible light.”
So
one day, could the police cloak a swat team or the Army, a tank? “It
is possible in principle, but not at this time,” Semouchkina said.
Her work is supported in part by a grant from the National Science Foundation.
Original article
