December 2005

Demo: Sensing Success

Continued from page 2

By David Rotman

Of course, it's one thing to design such a device; it's quite another to get it working reliably at the limits of its sensitivity. Burg, now a postdoc, developed the device for his doctoral thesis and has solved many of the problems of how the tiny suspended microchannel interacts with the outside world.

Manalis and Burg hope one day to build the detector into a small handheld device that could be used to detect pathogenic viruses or for a quick and easy cancer test in a doctor's office.

But for now, the chip that Burg is testing is hooked up to a tangle of electrical wires and held tightly by several small clamps at the end of a lab bench. A laser is aimed at the chip to measure precisely the vibrational frequency of the suspended microchannels. Plastic tubes protrude from holes dotting the chip and run to an automated liquid-handling instrument.

For physicists like Manalis and Burg, who are used to working with precise semiconductor technology, optimizing the chemistry and the flow of the liquids is the trickiest part of the experiments. The researchers first treat the inner walls of the microchannel with specific antibodies that will selectively bind to the target biomolecules, such as a particular type of protein.

The chemistry is not novel, says Burg, but because it's affected by temperature and other factors, it's unpredictable. For that reason, the group gathers seemingly endless data (the automated experiment runs through the night) to ensure that the microchannel is accurately and consistently detecting the targeted biomolecules.

If all goes well, though, within the next year the experimental device could move from all-nighters in the MIT lab to testing out in the real world. At that point, Innovative Micro Technology, a foundry in Santa Barbara, CA, will take over the production of standardized versions of the highly sensitive detectors.