Liquid-filled chips cool like mini-fridges

Purdue University researchers are testing a tiny device that Mr. Freeze would have loved: a square-inch refrigerator.

Purdue University can put a refrigerator in the palm of your hand.

Researchers at the West Lafayette, Ind., university's mechanical engineering department are testing out "microchannel heatsinks" that could cool components inside lasers, weapons or future computers with a series of channels filled with chilled, circulating fluids.

The newfangled heatsinks only take up about 1 square inch of space, meaning that several could fit into tight spaces to draw away heat. The channels inside the device that carry the liquid measure about 300 microns in diameter.

Microfluidics--making chips, or chip-size devices, with small coils for circulating liquid--is moving from a futuristic curiosity toward a compelling potential market.

ST Microelectronics, Intel and Pria Diagnostics have created microfluidic chips for preparing patient biological samples that could replace today's expensive lab procedures and equipment.

"Some of these microfluidic devices are little chemistry laboratories on a chip," Intel co-founder Gordon Moore said in a recent interview.

Purdue's heatsinks work like refrigerator coils. Cool liquid circulates toward a hot spot, absorbs heat, and then leaves, only to circulate back after a trip through a compressor. (Using a similar technology but in a very different way, Boston Microsystems has created a chip with microchannels that can heat up to 1,100 Celsius in 1/1,000th of a second.)

One of the challenges in the Purdue project was that materials behave differently inside a small device. Fluids flow differently in microchannels than they do in larger tubing, and bubbles form differently, which changes how heat is dissipated.

"You have to design new systems to pump coolants through these microchannels and develop new mathematical tools to predict how well designs will perform," Issam Mudawar, a professor of mechanical engineering, said in a statement.

Removing heat from PCs has become a major problem for chipmakers and PC manufacturers. The latest Apple G5 desktop comes with a liquid cooling system. However, the system adds about $50 to the cost of a computer, said Dan Hutcheson, CEO of market research company VLSI Research. Start-up Cooligy is creating a similar system for PCs that use chips from Intel and Advanced Micro Devices.

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