Researchers at the University of Michigan (UM) ran a light emitting diode (LED) with electrodes reversed in order to cool another device mere nanometers away, according to a news release posted on UM's website Wednesday.
To get enough infrared light to flow from an object into the LED, the two would have to be extremely together, less than a single wavelength of infrared light. This is necessary to take advantage of "near field" or "evanescent coupling" effects, which enable more infrared photons, or particles of light, to cross from the object to be cooled into the LED.
The researchers proved the principle by building a minuscule calorimeter, which is a device that measures changes in energy, and putting it next to a tiny LED about the size of a grain of rice. These two were constantly emitting and receiving thermal photons from each other and elsewhere in their environments.
But once the LED is reverse biased, it began acting as a very low temperature object, absorbing photons from the calorimeter. At the same time, the gap prevents heat from traveling back into the calorimeter via conduction, resulting in a cooling effect.
The researchers demonstrated cooling of 6 watts per meter squared. Theoretically, this effect could produce cooling equivalent to 1,000 watts per meter squared, or about the power of sunshine on Earth's surface.
This could turn out to be important for future smartphones and other computers. With more computing power in smaller and smaller devices, removing the heat from the microprocessor is beginning to limit how much power can be squeezed into a given space.
With improvements of the efficiency and cooling rates of this new approach, the researchers envision this phenomenon as a way to quickly draw heat away from microprocessors in devices. It could even stand up to the abuses endured by smartphones, as nanoscale spacers could provide the separation between microprocessor and LED.
The research is to be published in the journal Nature on Feb. 14.
