New mini sensor can measure brain's magnetic activity

The device could prove useful in brain-computer interfaces, testing for traumatic brain injuries, and more.

Elizabeth Armstrong Moore
Elizabeth Armstrong Moore
Elizabeth Armstrong Moore is based in Portland, Oregon, and has written for Wired, The Christian Science Monitor, and public radio. Her semi-obscure hobbies include climbing, billiards, board games that take up a lot of space, and piano.
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An atom-based magnetic sensor the size of a sugar cube has successfully measured human brain activity, a milestone that could ultimately lead to advancing our understanding of a wide range of neurological conditions and diseases, according to researchers at the National Institute of Standards and Technology (NIST).

The sugar cube-size NIST sensor can measure human brain activity using a gas of rubidium atoms and micro-optics. Knappe/NIST

We first reported on an earlier iteration of the sensor, which has been in development since 2004, back when the team was first able to use the sensor to track a human heartbeat in 2010.

This week, the researchers report in the journal Biomedical Optics Express that their tiny sensor -- which consists of a gas of 100 billion rubidium atoms and fiber optics to detect the light signals that in turn register the strength of magnetic fields -- now uses a new type of optical fiber that improves signal clarity.

"We're focusing on making the sensors small, getting them close to the signal source, and making them manufacturable and ultimately low in cost," says NIST co-author Svenja Knappe in the institute's news release. "By making an inexpensive system, you could have one in every hospital to test for traumatic brain injuries and one for every football team."

The researchers hope the sensor will improve magnetoencephalography (MEG), a technique for measuring the magnetic fields produced by electrical activity in the brain. Applications include testing for traumatic brain injury, screening for visual perception in newborns, and mapping neurological activity before surgeries that, say, aim to treat epilepsy or remove tumors.

The current gold standard MEG is called a superconducting quantum interference device (SQUID), but it works best at just above absolute zero and thus requires heavy helmet-shaped flasks with cryogenic coolants. NIST's sensor, for one, might allow for lighter, cheaper, and less rigid helmets.

As with the tests to detect a human heartbeat, the team worked with German scientists at a lab in Berlin that is described as having the best magnetic shielding in the world to block the Earth's magnetic field from interfering with extremely sensitive measurements. (The sensor measures signals of about a trillionth of a tesla -- called a picotesla; MRIs, by comparison, register closer to 1 to 8 tesla.)

The team says it anticipates being able to improve its sensor's performance another tenfold by upping the amount of light it can detect.