A thermal switch to moderate heat of electronic devices

It functions as a resistor in an electrical circuit.

Engineers at Purdue University have developed a thermal switch using compressible graphene foam to maintain the consistent thermal management of electronic devices.

Devices that run on batteries are pretty robust. But, when you use such devices in extreme heat or cold temperatures, you realize their susceptibility to malfunctions.

Most devices use passive thermal management, such as conduction and convection, to move excess heat. But this system isn’t tunable or adjustable and doesn’t help at all in cold conditions.

A newly developed thermal switch comes as a solution to this problem. The graphene foam that scientists used dynamically adjusts to temperatures both inside and outside the device.

When graphene foam is uncompressed, it acts as an insulator, with the air pockets keeping the heat in place. But when the foam is physically compressed, the air escapes, and more heat is conducted through the foam. Depending on how much the foam is compressed, heat transfer can be precisely dialed in.

Scientists also measured the thermal conductance of the foam. They sandwiched a 1.2-millimeter-thick sample of graphene foam in between a heater and heat sink. They placed the system under an infrared microscope to measure the temperature and heat flow. When fully compressing the foam to a thickness of 0.2 millimeters, the thermal conductance went up by a factor of 8.

Amy Marconnet, associate professor of mechanical engineering, said, “When the ambient is very hot, our thermal switch can transfer heat out to cool the batteries down, and when the ambient is too cold, our thermal switch can turn off heat transfer to keep the batteries warm.”

Journal Reference:
  1. Du, T., Xiong, Z., Delgado, L. et al. Wide range continuously tunable and fast thermal switching based on compressible graphene composite foams. Nat Commun 12, 4915 (2021). DOI: 10.1038/s41467-021-25083-8

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