Artificial leg prostheses are either light but passive, working essentially as springs, or powered but heavy to lug around. There are recent efforts to make electric powered prostheses more energy efficient, and lighter in the process. Yet batteries and the motors they power are still large and heavy when used in power hungry applications.
Researchers from University of Alabama, Vanderbilt University and the Georgia Institute of Technology have teamed up to develop a practical ankle prosthesis that is powered by rocket-like propellant. The technology seems to have had its roots at Vanderbilt, where mechanical engineering professor Michael Goldfarb, while working on an exoskeleton project for DARPA, got the idea of using monopropellants as an energy medium to power prosthetic devices. Monopropellants are so called because they don’t need to be mixed with other gases to be used as fuel, only requiring a bit of catalyst to decompose. The second major advancement in the new prosthetic is the “sleeve muscle actuator”, powered by the monopropellant, that is smaller, more powerful, and weighs less than a comparable electric motor.
More from University of Alabama:
To better guarantee the safety and reliability of the prosthesis, Shen [Dr. Xiangrong Shen, assistant professor of mechanical engineering] plans to explore new approaches in fuel storage, exhaust management, thermal insulation and heat management.
“This is a relatively new system,” Shen said. “There are some problems in putting the prosthesis into clinical use because the components of the prosthesis are still being developed. In our research, the long-term goal is to develop powered prostheses with comparable appearance and functionality as human limbs.”
After the research element of the project is completed, Shen and his team will test the device at Georgia Tech where he will use their multi-camera motion capturing system to measure his subject’s gait. He will also use a force plate to assess the kinetics in the walking as well.
Press release: UA Engineering Professor Developing Better Ankle Prosthesis