From the article: "The "nano-ear," a microscopic particle of gold
X-UID: 1270
Status: O
It's still at the experimental stage, but this could lead to far more
sensitive surveillance microphones in the future. The required laser
beam could be carried by a difficult-to-detect optical fiber strand
to the sensor. Combined with DSP and advanced acoustic signal
processing algorithms, this could represent a major security threat.
-bernieS
http://news.sciencemag.org/sciencenow/2012/01/scientists-create-worlds-tiniest.html?ref=hp
Scientists Create World's Tiniest Ear
by Tim Wogan on 13 January 2012
Sciencemag.org
(Graphic) Shaky idea. The movement of a gold nanoparticle (left) in a
set of optical tweezers was used to detect sound waves triggered by
the expansion of other nanoparticles nearby.
Credit: Ohlinger et al., Phys. Rev. Lett. 108, 018101 (2012)
Have you ever wondered what a virus sounds like? Or what noise a
bacterium makes when it moves between hosts? If the answer is yes,
you may soon get your chance to find out, thanks to the development
of the world's tiniest ear. The "nano-ear," a microscopic particle of
gold trapped by a laser beam, can detect sound a million times
fainter than the threshold for human hearing. Researchers suggest the
work could open up a whole new field of "acoustic microscopy," in
which organisms are studied using the sound they emit.
The concept of the nano-ear began with a 1986 invention known as
optical tweezers. The tweezers use a laser beam focused to a point
with a lens to grab hold of tiny particles and move them around.
They've become a standard tool in molecular biology and
nanotechnology, helping researchers inject DNA into cells and even
manipulate it once inside. Optical tweezers can also be used to
measure minuscule forces acting on microscopic particles; once you've
grabbed hold of your particle with the laser beam, instead of moving
it yourself, you simply use a microscope or other suitable monitoring
apparatus to watch whether it moves of its own accord. That's where
the nano-ear comes in.
Sound waves travel as a forward and backward displacement of the
particles of the medium they pass through. So to detect sound, you
need to measure this back-and-forth motion. Optical physicist Jochen
Feldmann and colleagues in the Photonics and Optoelectronics Group at
the University of Munich in Germany used a particle of gold 60
nanometers in diameter, immersed in water, and held in optical tweezers.
Feldmann's team recorded and analyzed the movements of this particle
in response to acoustic vibrations caused by the laser-induced
heating of other gold nanoparticles in the water nearby. As well as
having unprecedented sensitivity, their nano-ear could also calculate
the direction the sound had come from. They suggest three-dimensional
arrays of nano-ears working together could be used to listen in on
cells or microorganisms such as bacteria and viruses, all of which
emit very faint acoustic vibrations as they move and respire. "There
are definitely medical opportunities which we can tackle together
with the right people," Feldmann says, "but we just have to see how
it works first."
Biophysicist Lene Oddershede of the Optical Tweezer Laboratory at the
Niels Bohr Institute in Copenhagen is impressed and suspects the
paper will inspire others in the field to look for sound waves when
studying microorganisms. "It's a really interesting idea, and we
could easily do that, but we have never made any attempt to do so,"
she says. "I would say this paper's very inspiring in that sense."
She cautions, however, that the experimental setup will need to be
significantly refined to improve its ability to separate sound waves
from random molecular movement before the suggested acoustic
microscope can become a reality. But she is optimistic: "I do believe
they can relatively quickly improve the equipment."
Received on Sat Mar 02 2024 - 00:57:20 CST