MIT researchers led by Hugh Herr have demonstrated a wireless magnetic tracking technique that measures muscle movement to improve prosthetic limb control. Published in Nature Sensors on October 29, 2026, the study evaluated sesame-seed-sized magnetic beads implanted in ankle muscles of three below-knee amputees. In virtual tasks, this magnetomicrometry provided more accurate control signals than traditional surface electrodes. Researchers are now conducting larger trials to advance commercial neuroprosthetic development.
Development of magnetic tracking
- ▪MIT researchers published a study in Nature Sensors on October 29, 2026, demonstrating that magnetic beads implanted in muscles can accurately track muscle movement for prosthetic limb control.
- ▪In 2021, research led by Cameron Taylor in Hugh Herr's laboratory at MIT first demonstrated the magnet-based tracking technique in animal models.
How magnetomicrometry tracks muscle movement
- ▪Customized external sensors worn over the skin can detect signals from the magnetic bead implants at muscle depths of up to 6 centimeters.
- ▪In magnetomicrometry, pairs of 3-millimeter magnetic beads implanted into muscles allow external skin sensors to calculate muscle length and velocity by measuring changes in magnetic distance during muscle contraction.
- ▪The implanted magnetic beads are constructed from a neodymium, iron, and boron alloy, and are coated with gold and parylene C polymer to ensure biocompatibility.
Human trial setup and performance
- ▪In virtual neuroprosthetic tasks controlling an on-screen cursor, magnetomicrometry provided more accurate and stable control signals than both surface electromyography and implanted electromyography electrodes.
- ▪Surgeons at Brigham and Women's Hospital implanted magnetic beads into up to four ankle joint muscles in the trial participants, while also implanting intramuscular electrodes for comparative testing.
- ▪In October 2026, MIT researchers led by Hugh Herr, Christopher Shallal, and Cameron Taylor evaluated magnetomicrometry in three human participants with below-knee amputations who had previously undergone agonist-antagonist myoneural interface surgery.
Advantages over implanted wiring
- ▪Wireless tracking of magnetic implants through the body allows external sensors to measure specific mechanical muscle outputs without requiring invasive physical wiring through the skin.
- ▪The magnetic tracking interface requires placing two sesame-seed-sized beads in the target muscle, offering a less invasive alternative to bionic limb approaches that rely on fully implanted electrode systems.
Limitations of electromyography in neuroprosthetics
- ▪Skin surface electromyography measures electrical activation alone, which cannot directly determine mechanical control signals such as joint position, torque, or impedance necessary for safe walking with a neuroprosthetic leg.
- ▪For four decades, standard neuroprosthetic limb control has relied on skin surface electromyography electrodes, which often yield unreliable measurements due to signal fading during sustained contraction, muscle signal cross-talk, and sweat interference.
Future Research and commercial goals
- ▪The MIT development team aims for the improved accuracy and stability of the magnetic tracking system to enable commercial production of advanced neuroprosthetic artificial limbs.
- ▪MIT researchers are conducting a larger follow-up clinical study to evaluate how effectively amputees can directly control physical robotic prosthetic limbs using magnetic bead measurements.
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