Mobile Assist | University of Notre Dame

Lab Test

The ROAM team met with Light in 2021 but had to get safety clearance for their work with human test subjects. In May, Light visited the basement lab as the first amputee to test the motorized prostheses that Wensing and Posh had previously tried on themselves.

Adam Waugh, a certified prosthetist with Transcend Orthotics and Prosthetics, joined the Notre Dame researchers to offer advice and assistance. His most important responsibility was to take apart and rebuild Light’s current prosthesis so she could try the experimental one without compromising her safety.

“We were excited for the opportunity to offer our support and assist with this research,” Waugh said. “Every patient who has benefited from any number of complex devices has individuals like Ryan [Posh] to thank for their dedication to the advancement of the technology used within the prosthetic industry.”

“While the research is still in its early stages, I believe it will improve the lives of many people in the future.”—Adam Waugh

Waugh works with amputees regularly and sees how new and improved devices enrich their lives. He said allowing patients to move their own foot more actively would open the door to new activities and help with fatigue. Light agreed, noting that she had torn up the knee of her other leg by overcompensating through the years.

“This will likely increase blood flow to the leg, decrease volume fluctuations with use, and improve sound-side limb health overall,” Waugh said. “While the research is still in its early stages, I believe it will improve the lives of many people in the future.”

Posh first put Light’s shoe on the experimental prosthesis and taped a microcontroller to the socket of the prosthesis. He attached the electrode sensors that would register her muscle contractions in different spots on her residual calf.

The first step was calibration, testing whether the computer could pick up signals of extension and flexion in her muscles. The signals didn’t show up on a video screen as hoped, but the computer did register them at 250 readings per second.

Ryan Posh, a Ph.D. student in the ROAM Lab in Notre Dame’s College of Engineering, attaches sensors to the left leg of Laura Light.
Detail of sensors on a amputated leg  connect to a powered prosthetic lower-leg.
Sensors attached to Light’s residual limb connect to a powered prosthetic lower leg and foot.

As the device took control based on her muscles, it made a quick pop into position. Light gasped and said it felt “like having a frog in my foot.” She soon figured out how to position her leg to minimize the foot jump.

“That’s so weird,” she exclaimed. “I don’t know how to get it (the foot) where I want it to go.”

Posh and Wensing assured Light that it takes time to learn how to send the muscle signals to control movement, something Light had never had reason to try.

“I’m not used to firing that muscle; I’ll have to build it up,” she said. “I bet people who had a more recent amputation would know how to do it easier.”

Light hooked into a safety harness before standing and performing the three walking tests. Adjustments were made so that the motorized push off the heel would occur at the right moment in her walking gait. The motor made a whirring noise almost like a chipmunk squeak.

Light practiced rolling the foot forward and back, standing on tiptoes and sitting with it flat on the floor. “I like that this ankle rolls,” she said. “I don’t want to go back to my old foot.”

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