A Laptop Cooled with Ionic Wind

The thin and efficient technology could replace bulky cooling fans.

Anyone who uses a laptop will be familiar with the whir that the fan makes as it kicks in when the processor's temperature reaches around 100 °F. As laptops and other electronics have gotten smaller and thinner, researchers have begun searching for alternative cooling methods that add less bulk and are quieter.

Cooling: These infrared images show Tessera's ionic-cooling system in action. After the device is turned on, a plume of air carries heat away from the system. Credit: Tessera

One novel idea is to cool a system by using ions to push air molecules across a hot microprocessor, thereby creating a cooling breeze. So-called ionic-cooling systems have been demonstrated in research labs before, but now Tessera, an international chip-packaging company based in San Jose, CA, has demonstrated an ionic-cooling system integrated into a working laptop.

Researchers from Tessera and the University of Washington presented details of the ionic-cooling system at the IEEE Semi-Therm Symposium in March. The system can extract roughly 30 percent more heat from a laptop than a conventional fan can, and lab tests show that it could potentially consume only half as much power, the company says.

The ionic-cooler is based on work originally done in 2006 by Alexander Mamishev, a professor of electrical engineering at the University of Washington, and his colleagues. Last year, Tessera licensed the technology, and the company has since modified it to fit into a laptop. In addition to removing heat more efficiently than a fan, "it has silent operation--no moving parts," Mamishev says. "This is a big milestone."

"The early work focused on principles," says Ken Honer, director of research and development at Tessera. "We're now focused on optimizing it and fitting it into small form factors." This includes not only notebooks, but also game systems, projectors, and servers, he says.

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"Tessera's developments certainly show the potential for EHD cooling," says Suresh Garimella, who is a professor of electrical engineering at Purdue and director of the university's Cooling Technologies Research Center. "Their results are a positive step for this technology."

Tessera's ionic cooler sits near a vent inside the laptop. Heat pipes, which transfer heat using the evaporation and condensation of a fluid, draw heat away from the computer's processing units and toward the ionic-cooling system. Inside the ionic-cooling device are two electrodes: one that ionizes air molecules such as nitrogen, and another that acts as a receiver for those molecules. When a voltage is applied between the two electrodes, the ions flow from the emitter electrode to the collector. As they move, their momentum pushes neutral air molecules across a hot spot, cooling it down.