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David Bradley ISSUE #18
September 2001

Lab-on-a-CD

A medical diagnostics kit based on a compact disk is being developed by scientists at Ohio State University. The CD carries sensors and other devices which medics can use to quickly analyze saliva, blood, urine and other biological samples, according to materials scientist Marc Madou. The instructions for carrying out the test and interpreting the results can also be incorporated into the CD so that they could be displayed using a computer CD drive.

Madou, working with chemical engineer James Lee and Sylvia Daunert at the University of Kentucky, is taking the notion of a lab-on-a-chip a step laterally. The skill in their art is in developing techniques to accurately make tiny reservoirs and channels under the outer surface of a CD to allow samples and reagents to mix while the disc spins in a standard player. Centrifugal action as the disk spins pushes the sample's constituents outwards towards the edge of the disk where they mix with assay chemicals.

The team says that once they have perfected methods the CD could be used to measure anything from glucose to potassium or sodium levels. Optical sensors on the CD would change color during each diagnostic step and reveal information about the concentration of substances in a sample.

Madou's CD"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," says Madou. Importantly, the manufacturing of the raw disks is already a mature technology; it is the chemical aspect that the team is working hard to develop. Indeed, a variation on the theme might also be exploited in drug discovery.

Videos of a laboratory test taking place on a prototype CD can be viewed at:
http://www.acs.ohio-state.edu/units/research/archive/labcdvid.htm