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Sandia
creates motion detector 1,000 times more sensitive
than any known
Device allows naked
eye to see motion of 10 nanometers
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ALBUQUERQUE,
N.M. - A new class of very small handheld devices can
detect motion a thousand times more subtly than any
tool known.
"There was nothing in the [optics] literature to
predict that this would happen," says Sandia National
Laboratories researcher Dustin Carr of his group's device,
which reflects a bright light from a very small moving
object.
Sandia is a National Nuclear Security Administration
laboratory.
Carr, who earlier gained fame as a graduate student
at Cornell for his creation of a nanoguitar, was selected
this week by MIT's science magazine Technology Review
as one of the year's top 100 researchers under the age
of 35.
The patent-applied-for device will be the subject of
an invited talk at the SPIE Optics East convention in
Philadelphia in October, delivered by Sandia team member
Bianca Keeler.
Like shadow pictures projected onto a wall by shining
light through the fingers of one hand moving over the
fingers of the other, the relatively simple measuring
device depends upon a formerly unrecognized property
of optics: light diffracted from very small gratings
that move very small lateral distances undergoes a relatively
big, and thus easily measurable, change in reflection.
A motion of 10 nanometers can be seen by the naked eye,
says Carr.
A nanometer is one-thousandth of a micron, which is
one millionth of a meter.
As for the device, size matters and small is crucial.
"In standard MEMS [microelectromechanical] applications,
though the devices are small, very few things that sell
are dominated by a search for further miniaturization.
There's not a motivation in MEMS to make things still
smaller as a matter of cost. Economics of scale for
integrated circuits just don't apply to MEMS. But our
device couldn't exist unless you made it this small,"
he says. Features are in the 100-200 nanometer range,
with 300 nm between top and bottom combs and 600 to
900 nm between comb teeth.
Sub-wavelength interference effects cause the visual
display.
"Making use of the effect is fairly obvious once
you realize it happens," he says.
Fabricated out of polysilicon by standard lithography
techniques like those used to make MEMS devices, the
Sandia system uses two tiny comb-like structures (instead
of fingers) laid one over each other. The bottom comb
is locked rigidly in place. The top comb is secured
only by horizontal springs. Any tiny motion sends the
top comb skittering over the bottom comb, laterally
deforming the grating. A very tiny disturbance changes
by an unexpectedly large amount the amplitude of light
- in the visible to near-infrared range - diffracted
from a tiny laser beam shining upon the apparatus.
The measuring device, still in the laboratory stage,
is in effect a kind of accelerometer, about the size
of the inexpensive microelectromechanical devices that
open automobile air bags. Fabricated by the same processes
that mass-produce silicon computer chips, the device
has multiple possible uses.
"If you can make very sensitive detectors very
cheaply and very small, there are huge applications,"
says Carr. "Made small, synchronized, cheap, and
placed on every block, we could take data from all these
sensors at once and measure the motion of the earth
when there's not an earthquake. So we could learn what
leads up to one."
Another use would be for skid and traction control in
cars, detecting if the back end of the car is moving
in a different direction from the front end.
"Such devices also could take the place of inertial
navigation systems," Carr says. These typically
require large gyroscopes to keep commercial airplanes
moving on a preset course. "We could have handheld-sized
devices on Volkswagens that would work even in a tunnel."
Other defense applications are possible, he says.
He sees a time frame of three to five years before the
devices are available for use.
Says James Walker, former Director of Advanced Technologies
at Tellium, Inc., former manager of the MEMS Network
Element Sub-systems Group at Lucent, Bell Laboratories,
and now an independent consultant and patent agent,
"To my understanding, it is the first time anyone
has tried to manipulate the optical near-field region
in order to affect changes to the far-field characteristics
of a grating. The ability to do this is a direct result
of the nano-scale nature of the device. Due to its high
responsivity-to-displacement ratio, I see it having
significant, far-reaching application in areas as diverse
as chemical sensing, infrared imaging, accelerometry,
and displays."
Sandia is a multiprogram laboratory operated by Sandia
Corporation, a Lockheed Martin company, for the U.S.
Department of Energy's National Nuclear Security Administration.
With main facilities in Albuquerque, N.M., and Livermore,
Calif., Sandia has major R&D responsibilities in
national security, energy and environmental technologies,
and economic competitiveness.
Sandia media contact: Neal Singer, nsinger@sandia.gov,
505-845-7078
Sandia National Laboratories' World Wide Web home page
is located at http://www.sandia.gov. Sandia news releases,
news tips, science photo gallery, and periodicals can
be found at the News Center button
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This
story has been adapted from a news release -
Diese Meldung basiert auf einer Pressemitteilung -
Deze
tekst is gebaseerd op een nieuwsbericht - |
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