When 9-year-old Matthew Shields started third grade at a new school last year, he was hounded by questions.
“What’s wrong with your hand?” his classmates asked him. “How did it get like that?”
Matthew, who was born without fingers on his right hand, became insecure.
“My little guy, who had always been so confident, started hiding his hand in his shirt,” says his mother, Jennifer, 44, a special-needs teacher and single mom living in Miami County, Kansas.
“He was starting to withdraw,” she says. “It was heartbreaking.”
So last fall she turned to a family friend, Mason Wilde, 17, who had a passion for dismantling and rebuilding things.
She asked him if he could build Matthew a new hand. His answer? No problem!
“I have a mechanical mindset,” says Wilde.
“I was the type of kid that could take a shoulder socket from a LEGO dinosaur,” he says, “and use it to make a boat.”
Since Jennifer was unable to afford the thousands of dollars for a typical prosthesis, she researched options online and found a design that could be built using a 3-D printer instead. But it looked too complicated to do it herself. So she asked Mason.
“I knew about 3-D printers,” says Wilde. “I keep up with a tech online forum. And we were designing some stuff for them at school.
“But that was just theoretical,” he says. “So when this opportunity came forward, I was really stoked.”
Working from the online instructions for a plastic prothesis called Robohand, Mason spent hours adapting the design.
After another eight hours to print 20 pieces on a 3-D printer at the public library, he put them together using screws, nylon string, a drill and pliers.
And then Matthew had his hand.
“It’s the coolest thing ever,” says Matthew.
His fingers open and close by movement of the wrist, allowing him to pick up a pen, play two-handed catch and high-five his brothers.
“Every kid in my class wants one,” he says. “And I want to have a whole bunch of my own. In every color.”
Wilde is equally excited.
“This has been a dream come true,” he says. “I got to help somebody, and I got to use one of the new 3-D printers.”
Perhaps just as significant: The project cost about $60, an “exciting” development, especially for adolescents who need frequent replacements as they grow, says Dr. Charles A. Goldfarb, chief hand surgeon at Shriners Hospital for Children in St. Louis.
“It can be created cheaply, and over and over again, by anyone,” he says.
Indeed, that was the vision of Ivan Owen when he co-created the Robohand prototype in 2012 with a South African carpenter, Richard Van As, who wanted to make a mechanical finger for himself after a workshop accident.
“It’s truly uplifting to see the level of involvement and the number of people out in the world who have taken this idea as their own and are using it to help others,” says Owen, a special-effects artist and puppeteer from Bellingham, Wash.
The pair deliberately posted their D.I.Y. blueprint for free online so others could copy and adapt it, says Owen.
“Mason already has a vision for how he’d like to modify it further,” he says. “That’s just so beautiful.”
But the mechanics matter less to Matthew than the striking red color of his hand, and the fact that it now invites only amazing wonder, not ridicule.
“I’m like Superman,” he says. “Everybody at school thinks I’m so cool. Mason is awesome.”
More Heroes Among Us:
Know a hero? Send suggestions to firstname.lastname@example.org. For more inspiring stories, read the latest issue of PEOPLE magazine