Thursday, October 26, 2006

Tiny Pumps for Diagnostic Chips

Continued from page 1

By Jennifer Chu

The whole design has proved effective and efficient. Using a one-volt AC battery to power the tiny electrodes, the team observes improvements of flow speeds up to 20 times those of chips with only a two-dimensional electrode array. These flow speeds also matched those of conventional chips powered with 100-volt electrodes.

However, Bazant says there are still some things to work out before such a design can be taken into the field. The team was able to successfully pump diluted blood, as well as deionized water and a number of other diluted buffer solutions However, more concentrated solutions like undiluted blood could not be pumped by ACEO, for reasons currently under investigation.

Additionally, contamination of electrodes in real-life scenarios is also a concern, cautions Carl Meinhart, director of the Microfluidics Laboratory at the University of California, in Santa Barbara. "Circulation allows you flexibility in the design of the chip," he says. "If someone can develop a low-voltage electro-osmotic pump, and is able to do that with fluids in a robust environment with dirt involved or high-conductivity fluids like blood, then that's a huge step--that's very important."

In fact, Bazant says his design was able to pump some "dirty" fluids through the chip in biological assays, as long as those fluids were not too highly concentrated in electrolytes. Meanwhile, he has teamed up with his colleague Jeremy Levitan, visiting scholar in MIT's mathematics department. They are business partners in a company called ICEO Technologies, which explores potential lab-on-a-chip applications. According to Bazant, there is one idea that may be closer to being realized than battlefield applications: cooling portable electronics.

"If you could pass a fluid like water over the chip and dissipate the heat somewhere else without running out your battery," he says, "I believe this could be an interesting application."