GETTING CARRIED AWAY Ionized air molecules move from one electrode to the others, carrying with them a steady flow of warm air, much like a running brook carries leaves downstream. Image: © TESSERA, INC.
Anyone who has worked on a laptop resting on their thighs for more than a few minutes has probably wondered whether there is a better way to keep it from overheating than with tiny internal fans. (The bad news: the problem will be aggravated as faster, and thereby hotter processors are crammed into ever-shrinking electronics.)
The answer may lie in electro-hydrodynamic cooling, a technique where the air inside electronic devices is electrically charged so that heat disperses more efficiently.
Both academic and commercial researchers are pursuing technology that enables electro-hydrodynamic cooling, which uses an electrode to create a high-intensity electrical field that ionizes (electrically charges) the air molecules around it in tandem with a second set of electrodes to attract those charged particles. As the ionized air molecules move from one electrode to the others, they carry with them a steady flow of air, much like a running brook carries leaves downstream.
This may pave the way to quieter, lighter, smaller laptops, for example, that can utilize the latest microprocessors, which are superfast but also generate more heat than their predecessors, says Alex Mamishev, a professor of electrical and mechanical engineering at the University of Washington in Seattle who has since 1999 been developing an electrostatic fluid accelerator (EFA) that can provide fan-free cooling.
Mamishev's EFA technology has been tested by tech firm Tessera, Inc., in San Jose, Calif. "In the lab we've been able to show that we can remove the same amount of heat [as a fan does] using half as much power," says Craig Mitchell, senior vice president of Tessera's Interconnect, Components and Materials division. He says the company could by the beginning of next year start building prototype products that use the technology—which Tessera plans to dub Silent Air Cooling Technology (ACT)—although the company still has to work out some kinks, such as how to mass produce it.
Electronics typically include a metal heat sink that collects heat generated by the operation of the device and a mechanical fan to blow hot air out through a vent. Tessera envisions Silent ACT as being both a heat sink and a way to dissipate heat. Mitchell says that Silent ACT could eventually also be used to cool computer servers, video game consoles, projectors and other devices.
There are still many questions about the technology, Mamishev says. An initial concern was that devices using an EFA might produce excessive ozone, a compound that if inhaled can damage a person's respiratory system. This is a problem that retailer The Sharper Image ran into with its Ionic Breeze Quadra Silent Air Purifier, which Consumer Reports in 2003 claimed released potentially unhealthy levels of ozone. Sharper Image sued Consumer Reports for libel that year, but the case was dismissed in 2005. The negative publicity, combined with lagging sales of its high-end electronics, led the company to file for bankruptcy last year. (The company still sells some of its products through other retailers.)