Brainwave sensor
1 min read
A tiny sensor that can detect magnetic field changes as small as 70 femto Teslas (Ft) – equivalent to the brain waves of a person daydreaming – has been demonstrated at the US National Institute of Standards and Technology (NIST).
The sensor, which could be battery operated, may reduce the costs of noninvasive biomagnetic measurements such as foetal heart monitoring and could have applications in security screening.
Its performance is said to put it within reach of superconducting quantum interference devices – SQUIDs – which can sense changes in the 3 to 40fT range, but which must be cooled cryogenically, making them much larger, power hungry and more expensive.
The NIST prototype consists of a low power infrared laser and a container the size of a grain of rice. The container holds about 100billion rubidium atoms in gas form. The transmitted optical power of the laser beam is measured whilst varying the strength of a magnetic field applied perpendicular to the beam. The amount of laser light absorbed by the atoms varies predictably with the magnetic field, providing a reference scale for measuring the field. The stronger the magnetic field, the more light is absorbed.
“The small size and high performance of this sensor will open doors to applications that we could previously only dream about,” said project leader John Kitching.
