Swimming microparticles may help improve coolant performance

Your computer, car battery, or cell phone may one day be cooled down by swimming nanoparticles. Jeff Moran, an assistant professor of mechanical engineering at George Mason University’s Volgenau School of Engineering, is investigating an innovative technology that could help remove waste heat from devices as small as cell phones and as large as solar panels.

“This project is about making better liquid coolants,” he says. “Our laboratory focuses on self-propelled microparticles­­­­­–one one-hundredth the size of a human hair–that propel themselves in liquids like microscopic submarines, despite having no moving parts. They’re often called artificial microswimmers. We’re interested to find out whether they might be able to boost the performance of coolants in a new way.”

Moran received an EAGER (Early-concept Grants for Exploratory Research) Award from the National Science Foundation for the project, “Feasibility of Self-Propelled Nanoparticles for Heat Transfer Enhancement.” Moran received an EAGER (Early-concept Grants for Exploratory Research) Award from the National Science Foundation for the project, “Feasibility of Self-Propelled Nanoparticles for Heat Transfer Enhancement,” which he’s working on with Professor Pawel Keblinski of the Rensselaer Polytechnic Institute. The EAGER Award is meant to support bold, potentially transformative research ideas in their early stages of development.

Moran says there’s an urgent societal need for better heat transfer fluids. For example, heat removal is one of the factors limiting the maximum speed of computer chips. All microchips are cooled in some way because the chips overheat and stop working if the heat isn’t removed quickly enough. Some computers are cooled by air, which is why you hear the fan running. High-performance computers, and large data centers, are often cooled by liquid coolants.

The performance of many other devices is limited by the ability to remove heat from critical components, he says. “If we could dramatically improve heat removal technology, it would allow for faster, smaller devices.”

He is studying the effect on heat transfer with the addition of self-propelled microparticles to coolant liquids. One simple way to explain it: When you put cold cream in hot coffee, you want the cream and coffee to mix, and for everything to be at the same temperature. So, you stir it with a spoon. The spoon agitates the liquid, which causes what is called convective mixing. Of course, this requires a human to do the actual mixing, he says.

“In this project, we are trying to see if we achieve the same kind of mixing, but instead of a spoon, we have thousands and thousands of microscopic ‘spoons’ in the form of microswimmers, though they can have a variety of shapes,” Moran says. “We are trying to see if the micro-stirring caused by the swimmers accelerates the transfer of heat from a hot surface, be it a computer chip, an electric vehicle battery, or something else.”

For more than 25 years, researchers have investigated using nanoparticles to improve the performance of liquid coolants, creating what are known as “nanofluids.” But up until now, no one has experimentally quantified the improvements in performance that might happen if the particles can propel themselves through the fluid.

If the technology works, it has widespread applications including in cell phones, electric vehicle batteries, medical devices, and solar panels, which sometimes develop “hot spots” that degrade their performance, Moran says.

He and his team are especially interested in data centers, like those run by Amazon, Google, and Facebook. These generate enormous amounts of heat, and people are actively looking for ways to reduce the carbon footprints associated with managing that heat, he says.

“If we can more efficiently remove heat from data centers, the result is less overall consumption of electricity to cool them, and it will ultimately reduce the carbon footprint of these data centers,” he says. “We are trying to reduce the number of overall coolants that are required.

“Overall, the savings could amount to millions of dollars per year, and the carbon footprint of cooling technologies could be substantially reduced at the same time,” Moran says.

Leigh McCue, associate professor of mechanical engineering, says, “Jeff’s innovative, multi-disciplinary, collaborative research on swimming microparticles has game-changing potential for liquid cooling applications. He is clearly making a big impact. I look forward to seeing where Jeff takes these technologies in the years to come.”

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