Engineers at the University of New Brunswick have learned to capture electricity in the body to control the way special artificial limbs, called prosthetic arms, move. This will mean increased freedom and mobility for amputees or people born with a defect.

Advances in prosthetic limb research and design, and improvements in fitting techniques and training, have steadily improved the quality of life for wearers. This progress is due to innovative engineering, improved surgical procedures and new developments in the raw materials used to make prosthetics.

Some prosthetic limbs move, powered by small motors or by the movement of the wearer's muscles. Imagine if the limb could 'learn' to move just the way the wearer wants!

Engineering and technology are making this possible. A group of engineers at the University of New Brunswick's Institute of Biomedical Engineering has been researching control systems for prosthetic limbs since the early 1960s, and have been manufacturing control systems for many years. The technology they have helped to develop involves special computer circuits that control the motors using the very same electric signals generated by the brain to control the wearer's own muscles. These signals are called myoelectric signals ("myo" is a Greek word meaning "from the muscle").

The beauty of myoelectric control is that it increases the range of motion and degree of freedom for an individual fitted with a prosthetic limb. The engineers at the Institute are now using the technology to make these movements more natural. This is a significant advance over traditional prosthetics which tend to work slowly and limit a person's movements.

Wearers of these new prosthetic limbs learn to develop their own myoelectric signatures and program the system to recognize specific muscle contractions. Because the prosthetic can be customized to each wearer, it can accommodate a wide range of muscle control. The various signatures can be based on the strength, the frequency or the speed of specific muscle contractions. With careful training, prosthetic limb functions become 'learned' and easily repeated by the wearer.

As in most engineering work, the Institute is home to a diverse team of professionals. A biomedical engineer leads the team and studies the ability of the wearer to position the arm (such as the elbow and wrist movements), and grasp and hold objects (hand movements).

Chemical engineers determine the kinds of plastics and metals that work best in contact with the skin so that the electrodes can 'read' the small myoelectric signals coming from the body while the plastics keep the wearer comfortable over time.

Electrical engineers develop the tiny computers and motors that are built into the artificial limbs. The computers sense the myoelectric signals and, over time, 'learn' how the wearer wants a certain limb to move.

Mechanical engineers work with medical experts to understand how to make artificial limbs that move more naturally.

So far, 10 myoelectric control system units have been produced, three of which are at the Institute being tested in a clinical setting at the limb fitting centre. Initial reports have been very positive. As a result of this work, the Institute is a vital and innovative contributor to the quality of life of Canadians missing limbs.

Want to learn more about the myoelectric control system? Visit the Institute of Biomedical Engineering at www.unb.ca/web/biomed