A smaller magnetometer

A sensor the size of a rice grain can detect magnetic fields as small as those produced by brain waves, researchers report.

John Kitching of the National Institute of Standards and Technology in Boulder, Colo., and his colleagues filled a millimeterwide silicon cylinder, sealed by glass at both ends, with a gas of about 100 billion rubidium atoms. Under normal conditions, shining a laser through the container causes the spins of the atoms to line up.

The presence of a magnetic field, however, tips the atoms out of alignment. The disoriented atoms absorb some of the light from the laser beam, so by measuring how much light passes through the cylinder, the scientists can infer how misaligned the rubidium atoms are. The misalignment provides a measure of the strength of the magnetic field, the researchers report in the November Nature Photonics.

Kitching says these tiny sensors could be used noninvasively to measure brain waves or fetal-heart waves.

The detectors “are small, can run on low power, and could be very low cost,” he says. “That’s what gives them such great possibility for applications.”

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