American researchers have developed a magnetic sensor, which is smaller than a grain of rice yet sensitive enough to detect a fetal heartbeat. Thanks to this futuristic device, potential exists for a plethora of medical and security uses. The journal Nature Photonics carries a report on the device, which can detect changes in a magnetic field. It reports the device benefits as low-cost and easy-to-carry. "What we've done is demonstrate a very good sensitivity with a very small cell," says John Kitching of the Department of Commerce's National Institute of Standards and Technology (NIST), the team leader.
The device happens to be 1,000 times more sensitive than NIST's last microchip-sized mini-sensor. Though still in its formative stage, Kitching says the device could be used in a range of applications. This includes fetal heart monitoring and screening for explosives, among others. This is not all. Its small size permits it to function on a single AA battery, even for weeks.
"Magnetic fields are all over the place," Kitching informs. "Anything that has iron in it has a magnetic field."
A magnetic field can be emitted from electric currents, such as those from power lines. Even electrical impulses that make the heart contract or brain cells fire, do so. The sensor works basically by detecting such fields.
On a larger scale, bigger magnetometers are used by geologists to find iron deposits and by archeologists to find buried objects. Satellites to track the Earth’s magnetic field can also use these devices.
The most sensitive magnetic sensors are known as superconducting quantum interference devices, or SQUIDS. While these can detect very weak changes in magnetic fields their drawback is that they must be kept very cold, making them much bigger and far more power-hungry. The NIST device in place for a bit of that sensitivity makes up for it by its portability.
The prototype has a tiny container holding about 100 billion atoms of rubidium. The NIST researchers aim an infrared laser beam through the container and then measure how much light the atoms absorb. The formula is that higher the absorption the stronger the magnetic field is. Kitching vouches that the device is highly adaptable. It could be used to measure electrical activity in the brain, thereby spotting tumors or monitor brain function. It could also be used in war zones to detect bombs that may not have exploded.