Magnetoresistance is the change in a material's resistance to electrical current when an external magnetic field is applied to the material. That change usually is not more than 1 percent. But some multilayer materials display a change in resistance of as much as 80 percent. That is giant magnetoresistance.
Porter and Granger created a prototype reader that uses this phenomenon to detected changes in GMR caused by the presence of spots along the sensor. By swiping the sensor along the GMR reader, the sequence of spots (arguably the presence of some pathogen) creates a unique signature that gets interpreted as a diagnostic identifier. The device is currently PC sized but the team is working on miniaturizing the components for portability.
This is a pretty interesting approach to diagnostics and I wonder if it offers an alternative to the advances of lap on a chip technology, or if will become another form of diagnostic vacuum tubes.
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