Post by plutronus on Nov 17, 2015 11:08:18 GMT -6
"As
the cells are cooled by the LASER, the nanocrystals developed by the Univ of Washington team
emit a reddish-green "glow" that can be seen by the naked eye. "
Since
the first laser was invented in 1960, they've always given off heat --
either as a useful tool, a byproduct or a fictional way to vanquish
intergalactic enemies.
But those concentrated beams of light have never been able to cool
liquids. University of Washington researchers are the first to solve a
decades-old puzzle -- figuring out how to make a laser refrigerate water
and other liquids under real-world conditions.
In a study to be published the week of Nov. 16 in the Proceedings of the National Academy of Sciences, the team used an infrared laser to cool water by about 36 degrees Fahrenheit -- a major breakthrough in the field.
"Typically, when you go to the movies and see Star Wars laser
blasters, they heat things up. This is the first example of a laser beam
that will refrigerate liquids like water under everyday conditions,"
said senior author Peter Pauzauskie, UW assistant professor of materials
science and engineering. "It was really an open question as to whether
this could be done because normally water warms when illuminated."
The discovery could help industrial users "point cool" tiny areas
with a focused point of light. Microprocessors, for instance, might
someday use a laser beam to cool specific components in computer chips
to prevent overheating and enable more efficient information processing.
Scientists could also use a laser beam to precisely cool a portion of
a cell as it divides or repairs itself, essentially slowing these rapid
processes down and giving researchers the opportunity to see how they
work. Or they could cool a single neuron in a network -- essentially
silencing without damaging it -- to see how its neighbors bypass it and
rewire themselves.
"There's a lot of interest in how cells divide and how molecules
and enzymes function, and it's never been possible before to refrigerate
them to study their properties," said Pauzauskie, who is also a
scientist at the U.S. Department of Energy's Pacific Northwest National
Laboratory in Richland, Washington. "Using laser cooling, it may be
possible to prepare slow-motion movies of life in action. And the
advantage is that you don't have to cool the entire cell, which could
kill it or change its behavior."
The UW team chose infrared light for its cooling laser with
biological applications in mind, as visible light could give cells a
damaging "sunburn." They demonstrated that the laser could refrigerate
saline solution and cell culture media that are commonly used in genetic
and molecular research.
To achieve the breakthrough, the UW team used a material commonly
found in commercial lasers but essentially ran the laser phenomenon in
reverse. They illuminated a single microscopic crystal suspended in
water with infrared laser light to excite a unique kind of glow that has
slightly more energy than that amount of light absorbed.
This higher-energy glow carries heat away from both the crystal and
the water surrounding it.
The laser refrigeration process was first
demonstrated in vacuum conditions at Los Alamos National Laboratory in
1995, but it has taken nearly 20 years to demonstrate this process in
liquids.
Typically, growing laser crystals is an expensive process that
requires lots of time and can cost thousands of dollars to produce just a
single gram of material.
The UW team also demonstrated that a low-cost
hydrothermal process can be used to manufacture a well-known laser
crystal for laser refrigeration applications in a faster, inexpensive
and scalable way.
The UW team also designed an instrument that uses a laser trap --
akin to a microscopic tractor beam -- to "hold" a single nanocrystal
surrounded by liquid in a chamber and illuminate it with the laser. To
determine whether the liquid is cooling, the instrument also projects
the particle's "shadow" in a way that allows the researchers to observe
minute changes in its motion.
As the surrounding liquid cools, the trapped particle slows down,
allowing the team to clearly observe the refrigerating effect. They also
designed the crystal to change from a blueish-green to a reddish-green
color as it cools, like a built-in color thermometer.
"The real challenge of the project was building an instrument and devi....." To continue reading see:
www.ecnmag.com/news/2015/11/team-refrigerates-liquids-laser-first-time?et_cid=4946640&et_rid=45578776&type=cta