for more matter & energy stories,
visit www.sciencenews.org
By Rachel Ehrenberg
An X-ray for the
cell’s machinery
new laser method can probe
single molecules in action
Invisibility goes
macroscopic
new approach can conceal
objects big enough to see
By Daniel Strain
Professor Snape beware — invisibility
cloaks aren’t just for the microscopic
anymore.
Using natural crystals, two independent research teams have designed
“carpet cloaks” that can abracadabra
3-D objects as big as an ant or a grain of
sand seemingly into nothing. Up to now,
making things invisible has relied on tiny
structures called metamaterials. These
fabrications are often a mix of stacks
and crisscrosses of nanosized metals and
other materials that can guide electromagnetic rays, such as microwaves or
infrared and visible light, around objects.
If researchers tweak metamaterials just
right, they can make tiny things disappear — at certain light wavelengths and
from certain angles, at least.
But now two teams, an MI T group that
published its results in Physical Review
Letters in January and another from
England and Denmark that published
February 1 in Nature Communications,
don’t bother with metamaterials. They
use calcite prisms, a type of naturally
occurring crystal that shares some optical properties with metamaterials, to
build carpet cloaks.
Carpet cloaks aren’t true now-you-see-them-now-you-don’t apparatuses. The
bottom of the cloaking device is notched
with a small triangle that’s coated with
silver so that it works like a bent mirror.
Thanks to calcite’s optical properties,
the bent mirror can look like a flat plane
when viewed from some angles. Anything hiding in the notch vanishes.
This low-tech design sidesteps some
of the limitations of metamaterial invisibility cloaks, says Ulf Leonhardt, a
physicist at the University of St. Andrews
from top: Janos HaJdu/uppsala univ.; tHomas wHite/des Y
www.sciencenews.org
