University Develops Ion Cooling Device: Nano-Lightning to Cool Future Chips

@ 2004/03/29
Purdue University researchers described technology that could be used in future for cooling down computer chips with rapidly growing heat dissipation. Although the technique that uses a sort of nano-lightning to create tiny wind currents looks pretty exotic today, the inventors believe it would be used in future commercially.

Future computer chips will contain more circuitry and components, causing them to generate additional heat and requiring innovative cooling methods. Engineers are studying ways to improve cooling technologies, including systems that circulate liquids to draw heat from chips. Using a liquid to cool electronic circuits, however, poses many challenges, and industry would rather develop new cooling methods that use air.

The new technique developed at Purdue University works by generating ions – or electrically charged atoms – using electrodes placed close to one another on a computer chip. Negatively charged electrodes, or cathodes, are made of “nanotubes” of carbon with tips only as wide as 5nm.

Voltage is passed into the electrodes, causing the negatively charged nanotubes to discharge electrons toward the positively charged electrodes. The electrons react with surrounding air, causing the air molecules to be ionized just as electrons in the atmosphere ionize air in clouds. This ionization of air leads to an imbalance of charges that eventually results in lightning bolts.

The researchers are able to create the ionizing effect with low voltage because the tips of the nanotubes are extremely narrow and the oppositely charged electrodes are spaced apart only about 10 microns, or one-tenth the width of a human hair.

Future cooling devices based on the design will have an “ion-generation region,” where electrons are released, and a “pumping region,” made up of another set of electrodes needed to create the cooling effect.

Clouds of ions created when electrons react with air can then be attracted by the second region of electrodes and “pumped” forward by changing the voltages in those electrodes. The voltages are rapidly switched from one electrode to the next in such a way that the clouds of ions move forward and produce a cooling breeze.

More work must be done to perfect the technique and develop a prototype, the researchers said. Another version of the design might replace the carbon nanotubes with a thin film of diamond, which would be sturdier and easier to fabricate than the nanotubes. The researchers envision cooling devices that are small enough to fit on individual chips, actually making up a layer of the chip.

Most features of the device could be manufactured with conventional silicon fabrication techniques used in the semiconductor industry to make computer chips, according to researchers.

The researchers are to establish how much cooling could be achieved with the technique. New experimental results quantifying the cooling performance may be reported this summer.

There are more innovative cooling mechanisms, like Peltier elements, developed and used in some products. However, so far air-cooling along with heat-pipes have been the most cost-efficient ways for cooling down computers.

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