Researchers at Purdue University’s College of Engineering have developed a continuously tunable thermal regulator that could improve battery safety and performance in electronic devices and systems. The patent-pending, solid-state, continuously tunable thermal devices are based on compressible graphene foam composites that can insulate against cold, dissipate heat and function across a wide range of temperatures. The invention has the potential to provide a solution for the crucial issue of managing heat in electronic devices and batteries as they become more powerful.
The Need for Improved Thermal Regulation
As batteries and electronic devices become more powerful, managing heat becomes a crucial issue. Batteries have a narrow temperature range to function appropriately and are even more ‘picky’ than humans. Batteries perform poorly if they are too hot, and as they heat up, chemical reactions occur that cause them to heat up even faster. This unstable reaction progression is called ‘thermal runaway’ and can even lead to fires and explosions. On the other hand, if the temperatures are too low, batteries suffer internal damage, leading to poor performance like shorter driving ranges for electric vehicles and less cellphone usage time.
The Solution: Continuously Tunable Thermal Regulators
The Purdue University researchers have developed a new continuously tunable thermal regulator that can solve these problems. Conventional thermal switches can tune a battery’s heat dissipation pathways only by changing the conduction between on and off states. The Purdue-invented thermal regulators improve upon this technology by changing the thickness of the material inside the regulators, which helps batteries continually adjust to different climates and seasons.
The commercially available compressible graphene foam used by the researchers is built from nanoscopic particles of carbon deposited in a specific pattern with small voids of air in between. When uncompressed, the foam acts as an insulator, keeping heat in place. When compressed, air escapes, and heat is conducted throughout. The amount of heat transfer can be precisely dialed in depending on how much the foam is compressed.
Marconnet and Ruan measured the foam’s thermal conductance at Purdue’s Birck Nanotechnology Center. They sandwiched a 1.2-millimeter-thick sample of graphene foam in between a heater and heat sink and placed the system under an infrared microscope to measure the temperature and heat flow. When they fully compressed the foam to a thickness of 0.2 millimeters, the thermal conductance went up by a factor of 8. They also conducted an experiment in a chamber at Purdue’s Flex Lab that can create specific environmental conditions and achieved similar results with ambient temperatures from zero degrees Celsius (32 degrees Fahrenheit) to 30 degrees Celsius (86 degrees Fahrenheit).
The same approach could be applied to sensors and detectors for scientific or industrial applications that need to be maintained at precise temperatures, as well as electronic devices across a range of applications. It may also help maintain appropriate temperature for space vehicles, which face harsh environments of extreme heat and cold.
The Purdue thermal regulators have the potential to revolutionize battery safety and performance in electronic devices and systems. The researchers are looking to improve the range of thermal conductances achievable with the regulator and automate the process. The Purdue Research Foundation Office of Technology Commercialization applied for patent protection on the intellectual property. The battery application research was published in Nature Communications, and the fundamental research was published in ACS Applied Materials & Interfaces.
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