Purdue University engineers have developed a thermal switch proof-of-concept using compressible graphene foam to moderate heat in electronics, including electric vehicles and smartphones.
Devices that use lithium-ion batteries are susceptible to extreme heat and cold and can malfunction and perform poorly in such conditions.
Purdue researchers reported their work in the journal Nature Communications on Friday.
In their experiment, they placed a 1.2 mm thick piece of graphene foam between a heater and heat sink, then used an infrared microscope to measure the temperature and heat flow. When they fully compressed the foam to 0.2 mm, the thermal conductance skyrocketed by eight times.
They received a similar result in a special Flex Lab.
The research indicates that the amount of heat conducted out of an electronic device can be fully adjustable to improve performance and energy efficiency.
Purdue’s Office of Technology Commercialization has filed a patent application based on the thermal switching capability. The team has developed a continuously tunable thermal switch based on compressible composite foam. “This thermal device is promising for dynamic control operating temperatures in battery thermal management, space conditioning, vehicle thermal comfort and thermal energy storage,” the researchers said in the journal. It could be used in cell phones, as well as electric car batteries, space vehicles and biomedical devices.
Xiulin Ruan, a professor of mechanical engineer at Purdue, and Amy Marconnet, an associate professor there, oversaw the solution from postdoctoral researcher Tingting Du and master’s students Zixin Xiong and Luis Delgado. “Our goal is to use thermal switches to keep devices functioning effectively in varying environments and improve their overall energy efficiency,” Ruan said in a statement from Purdue. He noted that most existing electronics use passive thermal management such as conduction or convection to move excess heat, which isn’t tunable or adjustable and doesn’t work in the cold.
The researchers described open-pore graphene foam composites as analogous to a variable electrical resistor. Unlike conventional thermal switches, with only off and on states, partial compression of the foam provides access to an intermediate amount of conductance.
Graphene foam is commercially available and is built from nanoscopic particles of carbon deposited in a specific pattern with voids of air in between. When not compressed, it acts as an insulator with the air pockets keeping the heat in place. When compressed, the air escapes and more heat is conducted out through the foam. Depending on how much the foam is compressed, the amount of heat transfer can be controlled.
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