Researchers develop low-cost heat flow sensor

Researchers from the University of Tokyo have found a way to monitor the flow of heat in electronic or mechanical devices and improve their efficiency using embedded sensors.

University of Tokyo, Department of Physics Project Associate Professor Tomoya Higo and Professor Satoru Nakatsuji, worked with their team of researchers and a corporate partnership to track excess heat from electronic or mechanical devices – often a sign or cause of inefficient performance.

“The amount of heat conducted through a material is known as its heat flux,” Higo says. “Finding new ways to measure this could not only help improve device efficiency, but also safety, as batteries with poor thermal management can be unsafe.”

But finding a sensor technology to measure heat flux while also satisfying a number of other conditions such as robustness, cost efficiency, ease of manufacture and so on, was not easy.

“Typical thermal diode devices are relatively large and only give a value for temperature in a specific area, rather than an image of the heat flux across an entire surface,” Higo says.

The team explored the way a heat flux sensor consisting of certain special magnetic materials and electrodes behaves when there are complex patterns of heat flow.

“The magnetic material based on iron and gallium exhibits a phenomenon known as the anomalous Nernst effect (ANE), which is where heat energy is unusually converted to an electrical signal,” Higo says.

“This is not the only magnetic effect that can turn heat into power, though. There is also the Seebeck effect, which can actually create more electrical power, but it requires a large bulk of material [which is] brittle and hard to work with. ANE, on the other hand, allowed the team to engineer their device on an incredibly thin and malleable sheet of plastic.

“By finding the right magnetic and electrode materials and then applying them in a special repeating pattern, we created microscopic electronic circuits that are flexible, robust, cheap and easy to produce, and are very good at outputting heat flux data in real time.”

The method involves rolling a thin sheet of clear, strong and lightweight PET plastic as a base layer, with magnetic and electrode materials sputtered onto it in thin and consistent layers. We then etch our desired patterns into the resultant film, similar to how electronic circuits are made.

“I envisage seeing downstream applications such as power generation or data centres, where heat impedes efficiency,” says Prof. Nakatsuji. “But we might see these kinds of sensors in increasingly automated manufacturing environments where they could improve our ability to predict machine failures, certain safety issues, and more.

“With further developments, we might even see internal medical applications to help doctors produce internal heat maps of specific areas of the body, or organs, to aid in imaging and diagnosis.”

More information on the work is available at the University of Tokyo website.

Image courtesy of University of Tokyo.

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