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Nanotechnology

Cool News:
Nanotubes Could Improve Thermal Management

New research suggests that carbon nanotubes may soon be integrated into ever-shrinking cell phones, digital audio players, and personal digital assistants
to help ensure the equipment does not overheat, malfunction, or fail.

The chips inside an electronic device give off heat as a byproduct of power consumption when the object is on or being used. To reduce high temperatures, heat sinks—finned devices made of conductive metal such as aluminum or copper — are attached to the back of the chips to “pull” thermal energy away from the microprocessor and transfer it into the surrounding air.

Using microfin structures made of aligned multiwalled carbon nanotube arrays mounted to the back of silicon chips, researchers from Rensselaer and the University of Oulu in Finland have proven that nanotubes can dissipate chip heat as effectively as copper — the best known, but most costly, material for thermal management applications. And the nanotubes are more flexible, resilient, and 10 times lighter than any other cooling material available.

“When reduced to sub-millimeter sizes, the integrity of materials typically used for cooling structures breaks down. Silicon becomes very brittle and easily shatters, while metallic structures become bendable and weak,” says Robert Vajtai, a researcher with the Rensselaer Nanotechnology Center and corresponding author on the paper.

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Image by Robert Vajtai
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Carbon nanotubes, however, maintain their impressive combination of high strength, low weight, and excellent conductivity, and the coolers can be manufactured very cost effectively, Vajtai says.

The researchers have developed a simple and scalable assembly, using an innovative processing and transfer technique to integrate the nanotube structures on the chip. Compared to a chip with no cooling source, 11 percent more power was dissipated from the chip mounted with the nanotube cooler. Under forced nitrogen flow, the cooling performance with the fins was improved by 19 percent. “These numbers are consistent with the heat dissipated by the best thermal conditions and demonstrate the possibility of a lightweight, solid-state add-on structure for an on-chip thermal management scheme which works without involving heavy-metal block and fan or fluid-flow procedures for heat removal which can greatly increase the weight of electronic devices,” Vajtai says.

The researchers are continuing to explore a variety of techniques to further optimize the nanotube’s cooling capabilities by improving the thermal interface between the chip and the nanotube, enlarging the cooler’s surface area, and perfecting the fin-array geometry.

The research is funded by the Academy of Finland, the Nokia Scholarship, and the Focus Center-New York for Electronic Interconnects.

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Rensselaer (ISSN 0898-1442) is published in Spring, Summer, Fall, and Winter by the Office of Strategic Communications and External Relations, Rensselaer Polytechnic Institute, Troy, NY 12180-3590. Opinions expressed in these pages do not necessarily reflect the views of the editors or the policies of the Institute. ©2007 Rensselaer Polytechnic Institute.