Tiny channels carved in plastic enable medical tests on a CD

September 20, 2000

COLUMBUS, Ohio - Research at Ohio State University is paving the way for doctors to conduct blood tests and other diagnostics using a compact disc (CD) and a CD player.

One day, patients may be able to own a CD that contains sensors and other devices that can analyze drops of their blood, said Marc Madou, professor of materials science and engineering at Ohio State. The same CD could provide information on how to run medical tests and how to interpret the tests based on their own medical history.

Madou described his latest research efforts in a keynote address at the Eurosensors XIV conference in Copenhagen, Denmark, on August 28.

With L. James Lee, professor of chemical engineering at Ohio State, Madou is perfecting the shape of tiny reservoirs and channels on the surface of a CD to allow medical samples and other chemicals to mix while the disc spins.

"With this technology, a user would only have to put a drop of blood or urine on a CD, and a computer in the CD player would do the rest of the work," Madou said. "Patients could also have the CD player connect via the Internet to the doctor's office for a medical consultation or for storing the data in a central data bank."

As the CD spins inside a CD player, centrifugal force pushes liquid medical samples from the inner channels out to the edge, where it mixes with tiny pools of chemicals for testing. All types of analytical functions necessary for the test take place at that time.

"We found that if you control the size of the channels and the chambers you micromachine inside the plastic surface of the CD, you can basically build any analytical laboratory on a CD," said Madou.

The CD can do something that has never been done before, Madou said: merge medical information and diagnostic equipment in one fluidics platform. Once perfected, the disc could measure glucose levels in diabetics and store that information, for example. It could measure the concentration of potassium or sodium, or any substance of interest to doctors or hospitals, he said. The tool is also being investigated for use in the discovery process of new drugs. In one new development, the researchers crafted a sensor calibration unit into the surface of the CD. Madou and his colleagues designed the pools and channels in the CD so that steps to carry out such a sensor calibration can be controlled by changing the speeds at which the CD spins.

In his keynote address, Madou played a video of a prototype CD spinning slower and then faster to accurately time the release of the different chemicals required for calibrating an optical sensor also fitted on the CD. The optical sensor on the CD changed color during each step, revealing information about the concentration of substances within it. Sylvia Daunert, professor of chemistry at the University of Kentucky, collaborated with Madou for the chemical part of this work, which was sponsored by NASA.

Madou explained that a computer could be designed to "read" the color of the sample with a laser to measure the amount of a substance in a patient's blood, saliva, or urine.

What really makes this technology special, Madou said, is that such CDs could store not only medical samples and chemicals to analyze those samples, but also digital information - a person's medical history.

To prove the concept, Madou sometimes makes presentations on his laptop computer, using the same prototype CD that contains the microchannels to run the slideshow.

Madou thinks this technology may be available to the public as quickly as two years from now, in no small part because the techniques needed for creating and reading compact discs already exist.

"CDs have become so easy to fabricate they're almost disposable," Madou said. "Microchip companies have already perfected techniques for micromachining. Most important of all, electronics manufacturers have put millions of dollars into developing machines that read CDs. We just need to take advantage of all that."
Written by Pam Frost, (614) 292-9475, Frost.18@osu.edu

Ohio State University

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