Magnets Help Improve Control Of Bionic Prosthetic Devices

MIT researchers are working on methods that help people dealing with amputation to control high-tech bionic prosthetic limbs. There are several major challenges to bringing bionic prosthetic limbs to people worldwide, and one of the most challenging is improving the controllability of the prosthetics. Currently, typical prosthetic limbs use electromyography for control.

The control method records electrical activity from the muscles but can only provide limited control of the bionic limb. Researchers at MIT have devised an alternate control method that relies on magnets they believe can provide significantly improved control. Researchers insert small magnetic beads into muscle tissue near the amputation site.

The magnetic beads can precisely measure the length of the muscle when it contracts, and feedback is sent to the prosthesis within milliseconds. The speed of relaying muscle measurements to the bionic prosthetic devices gives smoother and significantly more precise control. The new strategy is called magnetomicrometry (MM), and it has shown it can provide fast and accurate measurements of muscle in animals.

Currently, the technique has only been trialed in animal testing. MIT researchers hope to move to human trials with amputees within the next few years. Researchers believe MM will replace electromyography as the most common control method for bionic prosthetic devices in the future. MM can provide high signal strength, is minimally invasive, has low regulatory requirements, and is low cost.

MIT researchers say with electromyography, information sent to the prosthetic limb is only about the electrical activity of the muscle, not length or speed. They describe the signal received using electromyography as an intermediate signal showing what the brain tells the muscle to do rather than what the muscle is doing. MM shows what the muscle is doing.