The prototype cooling chip contains two basic components: an emitter and a collector. The emitter has a tip radius of about 1 micron – so small that up to 300 tips could fit across a human hair. The tip creates air ions, electrically charged particles that are propelled in an electric field to the collector surface. As the ions travel from tip to collector, they create an air jet that blows across the chip, taking heat with it. The volume of the airflow can be controlled by varying the voltage between the emitter and collector.
The findings are significant for future computing applications, which will incorporate denser circuitry to boost computing power. More circuitry equals more heat and a greater need for innovative cooling technologies that go beyond bulky, noisy and relatively inefficient fans and heat sinks – metal plates with fins to increase surface area and help dissipate heat. Circulating liquids among the chips to draw away heat is one possibility, but computer chips and liquids don't mix well; the cost of a cooling system breakdown could be steep.
"Our goal is to develop advanced cooling systems that can be built right onto next-generation microchips," Jewell-Larsen said. "Such systems could handle both the increased heat generation of future chips and the fact that they would be distributed throughout a computer or electronic device." Added Mamishev: "It promises a new dimension in thermal management strategy and design."
A few challenges remain, he added. One involves developing the mathematical models to control vast systems of chips with built-in coolers. "These pumps end up being very complicated, dynamic systems," Mamishev said. "You have flow on a microscale, electrohydrodynamic forces, electrical fields and moving charges."
A second challenge is identifying the best materials to use in building devices that are high-performing and durable. "There is evidence that nanotubes and other nano-structures could give significant performance gains," Jewell-Larsen said. "Those are avenues we are currently pursuing."