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.) Tessera says it has in the lab “demonstrated ozone levels substantially below [U.S. Environmental Protection Agency] guidelines,” although the company would not elaborate on how it has done this.
Among other unanswered questions: the price tag of the technology–and how long the tiny electrodes needed to move the air will function before they become oxidized, contaminated or in some other way damaged.
Mamishev and his colleagues continue to develop the technology so it can remove larger quantities of heat without taking up additional space. He says he cannot elaborate more on his work, given the competitive environment emerging for the technology.
Purdue University’s Cooling Technologies Research Center in West Lafayette, Ind., headed by mechanical engineer Suresh Garimella, for the past six years has also been developing technology to cool electronics without any moving parts. Researchers there have received funding for this work from the National Science Foundation, Semiconductor Research Corp. and, more recently, Intel, Garimella says. (The NSF created a video demonstrating the technology.) Two of Garimella’s PhD students, Dan Schlitz and Vishal Singhal, set up Thorrn Micro Technologies, Inc., in Marietta, Ga., a few years ago to commercialize the technology (the company has since changed its name to Ventiva).
For the computer industry to continue to advance at the pace of Moore’s Law—which states that processing technology, including hard disks, microprocessors and networks, will improve exponentially over time as the cost of the technology drops—it will need a way to control potentially damaging side effects such as heat. One way to do this, Mamishev says, is to develop newer, faster processors that are shaped like a cube, rather than flat like those produced now. (IBM and DARPA—the U.S. Defense Advanced Research Projects Agency—are both working on this new technology.) Electrodes could then be built right into the cube to whisk away heat as it is generated.
Improved cooling technology will come to market too late to help the now infamous, yet unnamed, Swedish scientist whose genitals were badly burned in 2002, reportedly after keeping his laptop on his lap for an hour. Regardless of whether the story is true or an urban myth, it highlights a problem that is being addressed by some very real advances in ways to keep increasingly powerful gadgets cool.
