Pneumatic thought-controlled prosthetic arm created by students
By Ben Coxworth
March 31, 2011
Two undergraduate students from Toronto's Ryerson University have created a prosthetic arm that is controlled by its wearer's brain signals, and powered by compressed air. Not only is the Artificial Muscle-Operated (AMO) Arm said to offer a greater range of movement than traditional prostheses, but it also doesn't require the amputee to undergo invasive surgery, is easy to learn to use, and it is relatively inexpensive to make.
The AMO Arm was designed and built by Ryerson biomedical engineering students Thiago Caires and Michal Prywata. While it took them a year to create the custom software, the prototype itself was assembled in just 72 hours.
Amputee users wear a headset, which detects signals that their brains still produce, even after an arm has been lost. Those electrical signals are sent wirelessly to a microprocessor in the arm, that compares them to an onboard database of established command signals. If there's a match, it actuates the arm accordingly – if the user thinks of "up," for instance, the arm moves up.
While some traditional prosthetic arms move via myoelectric motors and relays, the AMO is pneumatic, using compressed air to simulate the expansion and contraction of muscles. That air comes from a refillable tank located in the user's pocket, although there are plans to move it into the arm itself. The relatively simple technology keeps the production costs of the arm down to about a quarter of those for other functional prosthetic arms, which can sell for up to US$80,000.
Some prostheses may also require the user to undergo muscle re-innervation surgery, in which nerves that formerly controlled the amputated arm are rerouted into a muscle adjacent to the amputation point (such as in the shoulder). Recipients must then undergo several months of training before they become proficient in using the arm. The AMO Arm, by contrast, simply straps on, and can reportedly be mastered in just minutes.
Caires and Prywata are now working on getting the fingers of the arm's hand to move independently – along with giving those fingers a sense of capacitive touch – and on developing an adaptive system that will allow the arm to "learn" from the habits of its user. They anticipate that it could be used not just as a prosthesis, but also as a reach-extending wheelchair attachment, or in military robotic applications.
The duo have formed their own company, Bionik Laboratories Inc., in order to commercialize the AMO. They are also working on artificial lungs, and a non-invasive system for bypassing spinal cord injuries.