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A loving hand — UND student engineers use microcontrollers, 3D-printed parts to create biomechanical prosthetic for North Dakota man

For their senior engineering project, five UND students built a prosthetic partial hand, shown here. The device is strapped to the hand of the subject, a local man whose left hand lacks a ring and pinky finger. Also shown is the EMG or electromyography sensor that detects signals from the muscles in the man’s wrist, and the detachable sleeve (at left) that can be worn over the forearm sensors. Photo courtesy of UND College of Engineering & Mines.

UND student engineers use microcontrollers, 3D-printed parts to create biomechanical prosthetic for North Dakota man

Last fall, UND senior Sam Dressler was at a picnic for engineering majors in Grand Forks when Megan Larson, a fellow engineering student, ran up to him. “Say, I heard you don’t have a senior project yet,” Larson said. “Do you want to join our group?”

Not sure, Dressler answered. What’s the group going to do?

“Well, we know someone who needs a biomechanical hand,” said Larson. “We’re going to build him one.”

And so they did.

For their capstone project to top off their undergraduate careers, Larson, Dressler and three other seniors at UND built a functioning, prosthetic partial hand. Designed for a North Dakota man who had lost the ring and pinky fingers on his left hand, the device features prosthetic versions of those two fingers attached to a forearm sleeve.

Inside the sleeve are sensors that rest on the man’s forearm. The sensors detect and respond to the muscles that normally would control the man’s ring and pinky fingers. So, when the man moves those muscles, he moves his new fingers, too.

The video below – which the students showed during their final presentation in early May – shows how the device works:

In the video, the man shows both his right and left hands, and successfully moves the same fingers at the same time on each.

First of its kind

“We believe this prosthetic is the first of its kind, because it’s a noninvasive solution for a partial hand and is customizable to the amputation,” said Larson, the project’s student leader and an Electrical Engineering major/Biomedical Engineering minor at UND. In other words, the prosthetic relies on sensors that sit on the surface of the skin, rather than using electrodes implanted in the muscles of the arm.

“In addition, we designed it so it can be adapted for any amputation,” she said. “So if someone has different fingers that are missing, you can make a device for that portion of the hand, and put the sensors on a different location on the forearm. Then you’ll have a whole new prosthetic for that new case.”

The students’ skill and the care with which they’d crafted the device were obvious from the moment he tried the prosthetic on, said the subject, who wishes to remain anonymous.

“Then the moment of truth – trying to move the fingers,” he said.

“We saw results with the pinky almost immediately, and it was actually kind of mind-blowing. Something was happening! Even though you realize what is expected or desired to happen, it was still pretty shocking. The team adjusted the sensor for the ring finger, and after a few minutes had that finger working, too.

“When I made a fist and it actually worked, we all cheered,” he said. “It was so cool!”

From left are Sam Dressler, Jasmyn Loven, Daryl Johnson (attending remotely, on screen), Megan Larson and Jack Neis, the UND seniors who designed and built a functioning, prosthetic partial hand. Photo courtesy of UND College of Engineering & Mines.

A graduate of Jamestown High in Jamestown, N.D., Larson was joined on the project by Dressler, a Computer Science major from Big Lake, Minn.; Jack Neis of Devils Lake, N.D., also a Computer Science major; and Electrical Engineering majors Daryl Johnson of Solon, Ohio, and Jasmyn Loven of Bismarck, N.D., with Loven also, like Larson, minoring in Biomedical Engineering.

And besides her skills with power systems, circuitry and 3D printing, Loven had another talent that proved vital: “I can sew,” she said with a laugh.

That proved handy, she said, “because the sleeve we got turned out to be a little too small. So the night before our final presentation, I had to sew in some extra fabric to make it more comfortable.”

Actually, added Dressler, “there was no shortage of challenges that we faced that night before. For example, one of the strings connecting to the fingers snapped, so we had to replace that.”

Multidisciplinary approach

Solving such problems on the fly is part of the point of capstone projects, said UND Associate Professor Kouhyar Tavakolian, the team’s advisor and the director of UND’s Biomedical Engineering program.

“And so is taking part in multidisciplinary projects such as this one,” he said. “For example, Biomedical Engineering by nature is not an independent discipline. The problems that it tackles do not have just one side to them; they call for people from different areas of engineering, applying all of their skills to solve those problems.”

To develop their prosthetic partial hand, the UND students used an open-source hand model, then brought the model down from five to two fingers, as shown at left in this slide from the students’ final presentation. To the right is a computer-generated illustration of the 3D printing of the device.

Larson and her fellow students showed just how much good can result when different disciplines successfully work together, Tavakolian said.

“Plus, this was an idea that they initiated themselves, and then they saw it all the way through to great success. I’m very proud of them.”

Larson – who knows the man for whom the prosthetic was designed – came up with the proposal and first recruited Loven. Johnson, Dressler and Neis followed, as the team’s need for skillsets from multiple disciplines became clear.

A key step was manufacturing the actual prosthetic – the partial hand. The team did this with a 3D printer at UND, using an open-source model of a full hand that the team edited for their own use.

“That took many hours, just to figure out the printer settings and make sure everything ran smoothly,” Loven said.

Megan Larson, an Electrical Engineering major at UND, holds the prosthetic partial hand that she and the team she led – a group of UND engineering students –built as their senior project. Photo courtesy of UND College of Engineering & Mines.

Testing the sensors – which the team did on each others’ forearms – was another challenge, “especially because the tendons for the ring finger and the pinky finger do a lot of cross-talk,” Larson said.

Even for people with intact hands, the cross-talk makes it hard to move one finger without at least twitching the other. “But we had to be able to distinguish between the signals enough to operate the device,” Larson said.

That’s when she and Loven brought their human-anatomy training – part of UND’s Biomedical Engineering program – to bear, by seeking out the surface manifestations of the complicated layers of muscles in the forearm.

From the president: ‘Well done’

The end result – a fully-functional partial prosthetic hand, one whose fingers respond to the natural muscle movements of the user – won the praise of UND President Andy Armacost himself. “Congrats, Megan, to you and your team!” the president posted, after Larson had published news and photos of the project on LinkedIn.

“People have been talking about your project on campus for the last couple of weeks! Well done,” Armacost continued.

As for the team members, they’re still savoring the project’s most thrilling moments, such as watching the subject put on the sleeve, strap on the prosthetic – and move his new hand’s ring and pinky fingers for the first time.

“If I had the chance to go back in time and tell my high-school self what I would be doing now, I would honestly be amazed,” Neis said. “It has been an incredible experience.”

Dressler agreed. “I get this wide-eyed reaction from my friends who are in non-STEM fields,” he said. “They look at this and say, ‘Wow, that is so cool!’ It’s really exciting, and I’m so happy I was able to be a part of it.”

The prosthetic itself is a prototype, which means it’s not really meant for full-time, day-to-day use, the subject said. But give it a few improvements such as a custom fit, durable materials, a natural look and an app for battery status and other indicators, “then my only question would be, ‘Where can I buy one?’”

All in all, “great job by this team, and it was so much fun working with them,” he said. “Thank you!”

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