Researchers at Shanghai Jiao Tong University in China have developed a coating for electronics that releases water vapour to dissipate heat from electronics.
"The development of microelectronics puts great demands on efficient thermal management techniques, because all the components are tightly packed and chips can get really hot," says senior author Ruzhu Wang, who studies refrigeration engineering at Shanghai Jiao Tong University. "For example, without an effective cooling system, our phones could have a system breakdown and burn our hands if we run them for a long time or load a big application."
Larger devices such as computers use fans to regulate temperature. However, fans are bulky, noisy, and energy consuming and thus unsuitable for smaller devices like mobile phones. Manufactures have been using phase change materials (PCMs), such as waxes and fatty acids, for cooling in phones. These materials can absorb heat produced by devices when they melt. However, the total amount of energy exchanged during the solid-liquid transition is relatively low.
In contrast, the liquid-vapor transition of water can exchange 10 times the energy compared to that of PCM solid-liquid transition. Metal organic frameworks (MOFs) were the most promising because they could store a large amount of water and thus take away more heat when heated.
"Previously, researchers have tried to use MOFs to extract water from the desert air," said Wang. "But MOFs are still really expensive, so large-scale application isn't really practical. Our study shows electronics cooling is a good real-life application of MOFs. We used less than 0.3 grams of material in our experiment, and the cooling effect it produced was significant."
The team selected a type of MOFs called MIL-101(Cr) for the experiment because of its good water-absorbing capacity and high sensitivity to temperature changes. They coated three 16-square-centimeter aluminum sheets with MIL-101(Cr) of different thicknesses--198, 313, and 516 micrometers, respectively--and heated the them on a hot plate.