An Alabama Teen 3D-Printed a Foot So That a Wounded Marine Could Snowboard
Over the span of a year, 17-year-old Ashley Kimbel went from being a regular teen at Grissom High School in Alabama to a hero for a retired Marine. When the budding engineer met Kendall Bane, a 26-year-old who was critically wounded in Afghanistan, she couldn’t ignore the way his disability left him unable to snowboard and mountain bike without damaging his prosthetic. Quickly mastering a new 3D modeling program, she built him a new foot that let him pursue the activities he loved.
" I came in and it was something fun to do.
Kimbel used Siemens’ Solid Edge computer-aided design software to sketch her idea, customize it to Bane’s needs, 3D print its models, and assemble it using mostly carbon fibre from her school lab.
“I loved doing this,” she tells Inverse. “I loved using Solid Edge and getting to work on this so it didn’t feel like work or a project. I came in and it was something fun to do, so finding something fun that you’re passionate about is the most important thing.”
After retiring, Bane had found himself unable to snowboard and mountain bike without tiring himself out or damaging the prosthetic. He has roughly half a dozen different types of prosthetic feet each for different activities, like one that can be pointed like a ballerina’s foot for swimming and another C-shaped one for sprinting. But he’d had trouble finding the perfect balance between strength and weight for his two favorite outdoor activities.
"I’ve broken several feet trying to snowboard or trying to ride bikes on them.
“I’ve broken several feet trying to snowboard or trying to ride bikes on them,” he said. “I told my prostheticist that I’d like a foot that could survive really high-impact, but what he gave me was really heavy. Even if it’s a couple of pounds heavier than my regular foot, and that’s enough to tire you out a lot over the course of a day.”
Frustrated, Bane discussed the problem with his brother Devon, who just happened to be a mentor for GreenpowerUSA, an after-school program centered on electric car engineering that Kimbel participated in. Devon put the two in touch, and the rest is history.
Kimbel started by virtually testing Bane’s original prosthetic, the Versa Foot, a high-impact foot that weighed two and a half pounds — a little too heavy to be useful. This digital twin allowed her to tweak the original foot to visualize what parts could be cut down or shaved off to reduce weight. In the end, Kimbel’s designs cut the weight down to just more than two pounds.
She only had to test a handful of models before she and Bane decided they had something worth testing physically. At that point, she says, things got a little messy.
She 3D-printed the mold for the reworked prosthetic and began the process of filling it in with carbon fiber, resin, and a high-resistance material called ultem, which is used to create airplane and rocket parts. But after two failed attempts and a malfunctioning pressurized oven, Kimbel was finally able to cast the foot.
“We decided to just do a wet layup, which is when you put dry carbon fibre between two pieces of plastic you pour the resin on it,” she said. “It’s really wet and sticky and pretty gross, but it turned out well.”
After attaching the foot to a stainless steel pylon that would allow Bane to easily swap the foot out, it was time to test. The first few moments were nerve-wracking for Kimbel, who was afraid something might snap or break loose causing Bane to trip or fall. But after a leisurely walk test and a more intense running test, her designed had proven sturdy enough to let Bane begin snowboarding and mountain biking again.
Like any good engineer, Kimbel says there’s room for improvement. She originally wanted the redesigned foot to weight closer to 1.7 pounds, which she believes is still possible by sizing down in a few places, like the top of the foot, and swapping the internal piston for a lighter component. But for now, there are no plans for a second version, and Bane is happy with the result.
Kimbel starts her first year of college soon at the University of Alabama in Birmingham, where she hopes to combine her love for medicine with her newfound passion for engineering. But instead of prosthetics, she wants to take the skills she learned from GreenpowerUSA to specialize in something even more cutting edge.
“I don’t know about making prosthetics but I definitely want to incorporate biomedical engineering and 3D printing in my future career,” said Kimbel. “Being on the forefront of medicine, maybe 3D-printed organs — I think that’s really cool and where I’m aiming to go.”