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February 09, 2007

Flow of tiny bubbles mimics computer circuitry: Breakthrough for labs on a chip


MIT researchers have developed a computer chip that runs on microbubbles like these. Photo courtesy / Manu Prakash

From physorg, in work that could dramatically boost the capabilities of "lab on a chip" devices, MIT researchers have created a way to use tiny bubbles to mimic the capabilities of a computer.


A colored montage of a ring oscillator used in the microfluidic computer developed by researchers at MIT. Starting with top left image, and reading left to right, the yellow bubble flows around the ring until it reaches and joins a stream of bubbles. Image / Felice Frankel and Manu Prakash, MIT

The team, based at MIT's Center for Bits and Atoms, reports that the bubbles in their microfluidic device can carry on-chip process control information, just like the electronic circuits of a traditional microprocessor, while also performing chemical reactions. The work will appear in the Feb. 9 issue of Science.

It will be possible to create large-scale microfluidic systems such as chemical memories, which store thousands of reagents on a chip (similar to data storage), using counters to dispense exact amounts and logic circuits to deliver them to specific destinations. The speed of operation is about 1,000 times slower than a typical electronic microprocessor, but 100 times faster than the external valves and control systems used in existing microfluidic chips. This will be a powerful technology for the bootstrap development phase of molecular nanotechnology.

"Bubble logic merges chemistry with computation, allowing a digital bit to carry a chemical payload. Until now, there was a clear distinction between the materials in a reaction and the mechanisms to control them," said co-author Neil Gershenfeld, director of the Center for Bits and Atoms and associate professor of media arts and sciences.

The technology has the potential to revolutionize large-scale chemical analysis and synthesis, environmental and medical testing and industrial production processes, but applications outside of the laboratory have been limited so far by the external control systems-valves and plumbing-required for its operation.

Other applications include combinatorial synthesis of many compositions at the same time, programmable print heads that can deposit a range of functional materials, and sorting biological cells.

The researchers modeled their new microfluidic chips on the architecture of existing digital circuits. But instead of using high and low voltages to represent a bit of information, they use the presence or absence of a bubble. They report on nitrogen bubbles in water, but any other combinations of materials that don't mix would work, such as oil and water.

In the Science paper they demonstrate all of the elements needed for any new logic family, including gates, memories, amplifiers and oscillators.

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