Cool breeze

US researchers have demonstrated a new technology using tiny ‘ionic wind engines’ that might improve computer chip cooling.


The Purdue University researchers, in work funded by Intel, have shown that the technology increased the ‘heat-transfer coefficient,’ which describes the cooling rate of the chips, by as much as 250 percent.


‘Other experimental cooling-enhancement approaches might give you a 40 percent or a 50 percent improvement,’ said Suresh Garimella, a professor of mechanical engineering at Purdue. ‘A 250 percent improvement is quite unusual.’


The experimental cooling device, contained a positively charged wire, or anode, and negatively charged electrodes, called cathodes. The anode was positioned about 10 millimetres above the cathodes. When a current was passed through the device, the negatively charged electrodes discharged electrons toward the positively charged anode. Along the way, the electrons collided with air molecules, producing positively charged ions, which were then attracted back toward the negatively charged electrodes, creating an ‘ionic wind.’ This breeze increased the airflow on the surface of the chip.


Conventional cooling technologies are limited by a principle called the ‘no-slip’ effect – as air flows over an object, the air molecules nearest the surface remain stationary. The molecules farther away from the surface move progressively faster. This phenomenon hinders computer cooling because it restricts airflow where it is most needed, directly on the chip’s hot surface.


The new approach potentially solves this problem by using the ionic wind effect in combination with a conventional fan to create airflow immediately adjacent to the chip’s surface.


The device was created at Purdue’s Birck Nanotechnology Center in the university’s Discovery Park. The researchers quantified the cooling effect with infrared imaging, which showed the technology reduced heating from about 60 degrees Celsius – or 140 degrees Fahrenheit – to about 35 degrees C, or 95 F.


The researchers also have developed computational models to track the flow of electrons and ions generated by the device, information needed for designing future systems using the technology.


The next step in the research will be to reduce the size of components within the device from the scale of millimetres to microns,. Miniaturizing the technology will be critical to applying the method to computers and consumer electronics, allowing the device to operate at lower voltage and to cool small hot spots.


Another challenge will be making the technology rugged enough for commercial applications.