For prosthetic legs to really allow amputees to regain their freedom of movement, they’ll need to be lightweight, mimic the natural mechanics of a human leg, and be self-powered and therefore cable-free. Researchers at the University of Utah have been working towards these objectives and are now showing off what they call one of the world’s first truly bionic legs, with an early tester describing it as a Terminator-like experience.

The prosthetic leg was developed by a mechanical engineering team led up by assistant professor Tommaso Lenzi, who set out to develop a tool for elderly amputees. That means the prosthetic was designed to not only help them regain mobility, but also be lightweight and reduce stress on other parts of the body when they are on the move.

Lenzi and his team achieved this by integrating accelerometers, gyroscopes, motors, force and torque sensors along with a computer processor into a largely titanium and aluminum prosthetic, weighing around 6 lb (2.7 kg). With the help of artificial intelligence, this array of sensors allow the leg to identify its position in the environment, while also making adjustments on the fly to match the user’s walking rhythm, speed and distance between steps.

It does this by way of electrical motors hooked up to the artificial joints, and the researchers credit the efficiency of this transmission system for the prosthetic’s ability to dynamically adapt its power distribution to match the user’s activity.

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

The researchers had a group of 10 participants try out the prosthetic, which they have dubbed the Utah Bionic Leg. Among those was retired truck driver Kerry Finn, who lost his leg to vascular disease. In the lab at the University of Utah, it enabled him to walk up two steps at a time, while also placing less stress on his stump compared to a regular prosthetic.

Amputee Kerry Finn tries out the Utah Bionic Leg

Mark Helzen Draper/University of Utah College of engineering

“If you’ve ever seen ‘The Terminator,’ that’s what it was like,” Finn says. “It made me feel like I could do things I could not do before. Every time I made a step, it was an awesome feeling.”

From here, the team hopes to continue improving the leg’s motion, including how it might track muscle activity in the residual limb to anticipate a user’s moves ahead of time, a long-pursued goal in this field of research.

“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.”

You can see Finn try out the Utah Bionic Leg in the video below.

Utah Bionic Leg

Source: University of Utah