October 12, 2018
A team at the College of Optical Sciences in the University of Arizona has developed a sensor that is able to detect the weak magnetic fields given off by firing neurons. The development team, led by Babak Amirsolaimani, believes that this technology could eventually replace more cumbersome MRI equipment.
This technology is based on the concept that the electrical impulses created by neural activity induce a very small magnetic field. Unlike the electrical impulses, however, the magnetic field can’t be distorted by contact with surrounding tissue. This means it should be possible to measure the magnetic field through the skin.
To accomplish this, the team built a sensor composed of magnetite and cobalt nanoparticles suspended in a polymer. In the presence of a magnetic field, this sensor is able to cause detectible polatization rotation in light. This polarization rotation is then detected using a compact fiber-optic interferometer.
In this paper, the sensors were used to detect the nerve impulses given by a beating human heart. The magnetic signal was clear and, despite the relatively small area of 100 µm
2, detected microsecond fluctuations. These promising results pave the way for further experimentation with this technology.
Also promising is the fact that this system can easily be setup so that it is not adversely affected by environmental aspects such as vibrations or change in temperature. According to Amisolaimani, the sensor itself can also be fabricated on a silicon photonics chip, meaning it could be made as small as 10 microns in diameter and at low cost.
This is in stark contrast with current MRI equipment, which is bulky, difficult to transport, and sensitive to temperature and vibration. Thus, a portable system that can be used to quickly assess trauma to the brain would be invaluable, for instance, in sports and in conflict zones.
The research team says that the next step will be developing a multi-sensor system capable to assessing the magnetic signals emitted by a human brain. If effective, this low-cost, portable technology could soon replace traditional MRI and make such assessments far more affordable for the average person.