Medicine: A quantum-mechanical effect used in hard disks may hold the key to the development of a hand-held biology laboratoryrnBiotechnologists have long dreamed of creating a "lab on a chip" that would pack the power of a full-scale analytical laboratory into an object as small and as easy to use as the hand-held scanners familiar to fans of science-fiction. Such a device might detect biological weapons, run genetic tests or sniff out contaminants. Staff at clinics could use it to screen people for infectious diseases.rnMany designs have been proposed for such a device, but none has really taken off. The latest, though, sounds promising. It uses a quantum-mechanical effect called giant magnetoresistance (gmr), which is also the basis of modern hard-disk drives. Prototypes made in Europe and America have indeed been able to detect everything from deadly toxins to illegal drugs and markers of disease.
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