THE LATEST RESEARCH AND DEVELOPMENT NEWS IN MANUFACTURING AND TECHNOLOGYTECH FRONT
First Chilling Laser Developed for Bio Research (Not Supervillainy)
t S
ince the fi rst laser was invented in 1960, they’ve almost always given off heat—either as a useful tool, a byproduct, or a fi ctional way to vanquish intergalactic
enemies. Until now, however, those concentrated beams of light have never been able to cool liquids. University of Washington researchers are the fi rst to solve a decades-old puzzle—fi guring out how to make a laser refrigerate water and other liquids under real-world conditions. In a study published in the Proceedings of the National Academy of Sciences, the team used an infrared laser to cool water by about 36°F—a major break- through in the fi eld. “Typically, when you go to the movies and see
Star Wars laser blasters, they heat things up. This is the fi rst example of a laser beam that will refrig- erate 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 specifi c components in computer chips to prevent overheating and enable more effi cient 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 research- ers 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 pos- sible before to refrigerate them to study their properties,” said Pauzauskie, who is also a scientist at the US DoE’s Pacifi c
Northwest National Laboratory in Richland, WA. “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 burn cells. They demonstrated that the laser could refrigerate sa- line solution and cell culture media that are commonly used in genetic and molecular research.
Laser-cooled nanocrystals emit a reddish-green glow that can be seen by the naked eye.
To achieve the breakthrough, the UW team used a mate- rial 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 fi rst demonstrated in vacuum conditions at Los Alamos National Laboratory in 1995, but it has taken nearly 20 years to demonstrate this process in liquids.
January 2016 |
AdvancedManufacturing.org 31
Photo courtesy University of Washington
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