In the final stage, these tagged markers are captured by a different set of antibodies, which hold them in place so they can be measured. This is done with a separate device called a fluorescence reader, commonly found in hospitals, which illuminates the chip and measures the amount of fluorescent light given off by the markers. The work is published in the latest issue of the journal Lab on a Chip.

"This work is very interesting," says Juan Santiago, head of the Stanford Microfluidics Laboratory. Not only have the IBM researchers shown that their device can cope with filtering blood, but given the chip's precise control over the liquid, it might also carry out multiple tests in parallel, or even in series of multistage reactions, he says.

IBM is working with Belgian diagnostics firm Coris BioConcept to assess the accuracy of the chips by comparing them directly with traditional laboratory-based testing. "The next step is to develop a pilot series of maybe a thousand devices and test them on samples from hospitals," says Delamarche.