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A Laser Has Been Used to Refrigerate Liquid for the First Time

As they are cooled by the laser, the nanocrystals developed by the UW team emit a reddish-green 'glow' that can be seen by the naked eye. (Image:  Dennis Wise/University of Washington)
As they are cooled by the laser, the nanocrystals developed by the UW team emit a reddish-green 'glow' that can be seen by the naked eye. (Image: Dennis Wise/University of Washington)

Ever since lasers were invented in 1960, they have always given off heat. Now, researchers from the University of Washington have, for the first time, managed to figure out how to refrigerate water and other liquids under real-world conditions with a laser.

In the study, published in the Proceedings of the National Academy of Sciences, the researchers were able to use an infrared laser to cool water by about 36°F, making it a major breakthrough in the field.

Peter Pauzauskie, UW assistant professor of materials science and engineering and senior author said: “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.

“It was really an open question as to whether this could be done because normally water warms when illuminated.”

According to AAAS, the discovery could help industries that need to “point cool” areas with a focused point of light. An example would be using it to cool specific components in computer chips. It could also be used by scientists to cool a portion of a cell as it divides or repairs itself, 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.

This instrument built by UW engineers (from left) Peter Pauzauskie, Xuezhe Zhou, Bennett Smith, Matthew Crane and Paden Roder (unpictured) has used infrared laser light to refrigerate liquids for the first time. (Image: Dennis Wise/University of Washington

This instrument, built by UW engineers (from L) Peter Pauzauskie, Xuezhe Zhou, Bennett Smith, Matthew Crane, and Paden Roder (unpictured), used infrared laser light to refrigerate liquids for the first time. (Image: Dennis Wise/University of Washington)

Pauzauskie said in a statement: “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.

“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 the laser could refrigerate saline solution and cell culture media that are commonly used in genetic and molecular research, according to ECN.

The scientists effectively made the laser run in reverse. By using the infrared laser light to illuminate a single microscopic crystal that was suspended in the water, it caused a glow that has a slightly higher energy than the energy absorbed. This higher-energy glow then directs heat away from the crystal as well as the surrounding water, thus refrigerating the material.

Lead author Paden Roder from Intel Corp said: “The real challenge of the project was building an instrument and devising a method capable of determining the temperature of these nanocrystals using signatures of the same light that was used to trap them.”

So far, the UW team has only demonstrated the cooling effect with a single nanocrystal, as exciting multiple crystals would require more laser power. The laser refrigeration process is currently quite energy intensive, Pauzauskie said, and future steps include looking for ways to improve its efficiency.

“Few people have thought about how they could use this technology to solve problems because using lasers to refrigerate liquids hasn’t been possible before,” he said. “We are interested in the ideas other scientists or businesses might have for how this might impact their basic research or bottom line.”

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