[Editors] MIT designs portable 'lab on a chip'

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT designs portable 'lab on a chip'
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For Immediate Release
MONDAY, OCT. 16, 2006
Contact: Elizabeth A. Thomson, MIT News Office
Phone: 617-258-5402
Email: thomson at mit.edu

IMAGES AVAILABLE

CAMBRIDGE, Mass.--Testing soldiers to see if they have been exposed 
to biological or chemical weapons could soon be much faster and 
easier, thanks to MIT researchers who are helping to develop a tiny 
diagnostic device that could be carried into battle.

By tweaking the design of a tiny pump, researchers affiliated with 
MIT's Institute for Soldier Nanotechnologies have taken a major step 
towards making an existing miniature "lab on a chip" fully portable, 
so the tiny device can perform hundreds of chemical experiments in 
any setting.

"In the same way that miniaturization led to a revolution in 
computing, the idea is that miniature laboratories of fluid being 
pumped from one channel to another, with reactions going on here and 
there, can revolutionize biology and chemistry," says Martin Bazant, 
associate professor of applied mathematics and leader of the research 
team.

Within the lab on a chip, biological fluids such as blood are pumped 
through channels about 10 microns, or millionths of a meter, wide. (A 
red blood cell is about 8 microns in diameter.) Each channel has its 
own pumps, which direct the fluids to certain areas of the chip so 
they can be tested for the presence of specific molecules.

Until now, scientists have been limited to two approaches to 
designing labs on a chip, neither of which offer portability. The 
first is to mechanically force fluid through microchannels, but this 
requires bulky external plumbing and scales poorly with 
miniaturization.

The second approach is capillary electro-osmosis, where flow is 
driven by an electric field across the chip. Current electro-osmotic 
pumps require more than 100 volts of electricity, but the MIT 
researchers have now developed a micropump which requires only 
battery power (a few volts) to achieve similar flow speeds and also 
provides a greater degree of flow control.

The key to boosting energy efficiency is altering the electric field 
in the channel, Bazant said. Instead of placing electrodes at each 
end of the channel, as in capillary electro-osmosis, the voltage can 
be lowered substantially with alternating current (AC) applied at 
closely spaced microelectrode arrays on the channel floor. Existing 
AC electro-osmotic pumps, however, are too slow for many 
applications, with velocities below 100 microns per second.

In the new system, known as a three-dimensional AC electro-osmotic 
pump, tiny electrodes with raised steps generate opposing slip 
velocities at different heights, which combine to push the fluid in 
one direction, like a conveyor belt. Simulations predict a dramatic 
improvement in flow rate, by almost a factor of twenty, so that fast 
(mm/sec) flows, comparable to pressure-driven systems, can be 
attained with battery voltages. Experiments in the lab of Todd 
Thorsen, assistant professor of mechanical engineering, have recently 
demonstrated the effectiveness of the design.

"It's just a huge improvement with a very simple idea," said Bazant.

Thorsen's group is working toward integrating the pumps into a 
portable blood analysis device, which soldiers could carry onto the 
battlefield. If exposure to chemical or biological weapons were 
suspected, the device could automatically and rapidly test a 
miniscule blood sample, rather than sending a large sample to a lab 
and waiting for the results. The chips are so small and cheap to make 
that they could be designed to be disposable, Bazant said, or they 
could be made implantable.

Potential applications are not limited to military use - imagine 
going to a doctor's office and getting test results immediately.  The 
technology could also be useful for first responders. If emergency 
personnel knew immediately whether a person had suffered a heart 
attack or a stroke, they could start the appropriate treatment right 
away.

Labs on a chip can also be used in traditional chemistry or biology 
labs to speed up processes such as DNA testing or screening for the 
presence of certain antigens.  Only tiny amounts of reactants would 
be needed, and experiments could be done more rapidly and efficiently.

"Instead of a thousand people pouring test tube A into test tube B in 
different laboratories, you've got a tiny little chip with thousands 
of experiments all going on at once," Bazant said.

Bazant and former MIT postdoctoral associate Yuxing Ben published an 
article on the theoretical work in the online edition of the journal 
Lab on a Chip, and a related experimental paper will appear in an 
upcoming edition of Applied Physics Letters. Co-authors on that paper 
with Bazant and Thorsen are graduate student J.P. Urbanski and 
postdoctoral associate Jeremy Levitan.

The research was funded by the U.S. Army through the Institute for 
Soldier Nanotechnologies.

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Written by Anne Trafton, MIT News Office