Prosthetic limbs have vastly improved the quality of life for those with amputations, but the greatest challenge remains: to have a more reliable, human-like control of the prosthesis. So far, electromyography (EMG) is the main technique to control the prosthetic limb. However, EMG-controlled bionic limbs can only offer limited control. They tell us about the message the brain sends to the muscle, not what the muscle is doing in real time. If we can find out what the muscle is actually doing, we can have an almost human-like experience with bionics.
Researchers at the Media Lab of Massachusetts Institute of Technology (MIT) have made some great development in this domain. They have introduced a new strategy—magnetomicrometry (MM)—to attain a more precise control of prosthetic limbs.
In a study published in Science Robotics, MIT researchers have tested a new MM approach to control bionic limbs in turkeys. They inserted pairs of tiny magnets (3mm in size) in the calf muscles of turkeys. Using an array of sensors on the outside of turkeys’ legs during movement, the researchers were able to determine the location of magnets with high precision. The great deal about this experiment is that these measurements were obtained within three milliseconds, thus resolving the problem of long time-lag with an MM-controlled prosthesis.
A fast measurement means that the patients could imagine a more precise location of their prosthetic device as they move. Magnetomicrometry could help them move with greater accuracy regarding how and where they want to position their bionics.
Another great feature of this approach is its minimal invasion. The existing way of measuring the electrical activity of the muscles is through electrodes that are either attached to the patient’s skin surface or surgically implanted in the muscle. The latter provides more accurate measures, but clearly, it is an invasive and costly method.
MIT researchers believe that the sensors used to control bionic limbs with the MM approach are minimally invasive and could even be placed on clothing or attached to the outer surface of a prosthesis or a subject’s skin.
Success with the MM approach in animal-based research has encouraged scientists to conduct human trials within the next few years. These trials may change the reliability and comfort of prosthetic limbs forever.