Magnetomyography

Magnetomyography (MMG) is a technique for mapping muscle activity by recording magnetic fields produced by electrical currents occurring naturally in the muscles, using arrays of SQUIDs (superconducting quantum interference devices).[1] It has a better capability than electromyography for detecting slow or direct currents. The magnitude of the MMG signal is in the scale of pico (10−12) to femto (10−15) Tesla (T). Miniaturizing MMG offers a prospect to modernize the bulky SQUID to wearable miniaturized magnetic sensors.[2]

Two key drivers for the development of the MMG method:[3] 1) poor spatial resolution of the EMG signals when recorded non-invasively on the skin where state-of-the-art EMG measurements are even using needle recording probes, which is possible to accurately assess muscle activity but painful and limited to tiny areas with poor spatial sampling points; 2) poor biocompatibility of the implantable EMG sensors due to the metal-tissue interface. The MMG sensors have the potential to address both shortcomings concurrently because: 1) the size of magnetic field reduces significantly with the distance between the origin and the sensor, thereby with MMG spatial resolution is uplifted; and 2) the MMG sensors do not need electrical contacts to record, hence if fully packaged with biocompatible materials or polymers, they can improve long-term biocompatibility.

MMG using conventional SQUIDs[1] (top) and miniaturised implantable magnetic sensors[2] (bottom).
  1. ^ Cohen, David; Givler, Edward (1972). "Magnetomyography: magnetic fields around the human body produced by skeletal muscles". Applied Physics Letters. 21 (3). AIP Publishing: 114–116. Bibcode:1972ApPhL..21..114C. doi:10.1063/1.1654294. ISSN 0003-6951.
  2. ^ Heidari, Hadi; Zuo, Siming; Krasoulis, Agamemnon; Nazarpour, Kianoush (2018). CMOS Magnetic Sensors for Wearable Magnetomyography. 40th Int Conference of the IEEE Engineering in Medicine and Biology Society. Honolulu, HI, USA: IEEE. doi:10.1109/embc.2018.8512723. ISBN 978-1-5386-3646-6.
  3. ^ Zuo, Siming; Heidari, Hadi; Farina, Dario; Nazarpour, Kianoush (2020). "Miniaturized magnetic sensors for implantable magnetomyography". Advanced Materials Technologies. 5 (6). Wiley. doi:10.1002/admt.202000185. hdl:10044/1/82414.