Utah Bionic Leg Project Awarded Grants

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Finn was one of ten participants who tested the self-powered prosthetic limb.

Photograph courtesy of Mark Helzen Draper/University of Utah College of Engineering.

University of Utah mechanical engineering assistant professor Tommaso Lenzi, PhD, has received two new grants to further advance the technology in development of the Utah Bionic Leg. One is a $2.2 million award from the National Institute of Health, and the other is a $600,000 grant from the National Science Foundation.

The prosthetic leg has sensors, motors, a computer processor, and artificial intelligence that work in conjunction to give the user more power to walk with less stress on the body than with a standard prosthesis. That means people with amputations, particularly elderly individuals, can walk much longer with the new leg, says Lenzi.

"If you walk faster, it will walk faster for you and give you more energy. Or it adapts automatically to the height of the step. Or it can help you cross over obstacles," Lenzi says.

The leg uses custom-designed force and torque sensors as well as accelerometers and gyroscopes to help determine the leg's position in space. Those sensors are connected to a computer processor that perceives the environment and determines the user's rhythmic motions, step length, and walking speed. Based on that real-time data, it then provides power to the motors in the joints to assist in walking, standing up, walking up stairs, or maneuvering around obstacles.

"Every time you take a step, it's powered, and it gives a certain kick. It also gives me the ability to take two steps at a time going up stairs," says Kerry Finn, one of the testers. "With this leg, it's less strain on my stump. You don't have to work as hard. And it takes a lot of the stress off the body."

The leg is designed to weigh about six pounds, half the weight of other bionic legs under development, say the researchers, a benefit for elderly people or those who, like Finn, lost a lower limb to vascular disease.

While the prosthesis is made mostly of aluminum and titanium, the lightweight construction is more due to the leg's design, Lenzi says. "We have a unique way of designing the systems."

For example, the leg uses a smart transmission system connecting the electrical motors to the joints. This optimized system intuitively knows what kind of activity the user wants to do and automatically adapts to it, like shifting gears on a bike. The leg also uses smaller batteries to power the motor that are built into the leg.

Lenzi and his team received the government grants to research how the leg enables a user to move better and do more. The team will also study how it could be designed to better anticipate a user's movements by tracking muscle activity in the person's residual limb.

"The ability to walk is essential to your life and being able to pursue whatever you want to do. When just standing up is a pain and when walking means being afraid of falling, you just don't go on with your life and you are stuck at home," Lenzi says. "This is about making bionics accessible for all people and not just those who are young and high performing."

Editor's note: This story was adapted from materials provided by the University of Utah.