clipped from: www.abc.net.au   
Julie Steenhuysen
A magnetic sensor smaller than a grain of rice and sensitive enough to detect the brainwave of someone daydreaming has been developed by US scientists who say their research offers the potential for a host of new medical and security uses.
daydream
They says the sensor, described online in the journal Nature Photonics, provides a low-cost and portable way to detect changes in a magnetic field.
"What we've done is demonstrate a very good sensitivity with a very small cell," says Dr John Kitching of the US National Institute of Standards and Technology (NIST), who led the project
The researchers say it's 1000 times more sensitive than NIST's last microchip-sized mini-sensor and can detect magnetic fields down to 70 femtoteslas
"Magnetic fields are all over the place," Kitching says. "Anything that has iron in it has a magnetic field.
Electric currents, such as those from power lines, emit a magnetic field, as do the electrical impulses that make the heart contract or brain cells fire