Jim McMahon/Mapman®

David Aguilar, 19, was born without a right forearm. When he was growing up in Andorra (a tiny country between Spain and France), his rare genetic condition made him feel different around other kids. So at age 9, he used plastic LEGO bricks, his favorite toy, to build his first artificial arm. The design was very basic, but it served its purpose: 

“I wanted to . . . see myself in the mirror like I see other guys—with two hands,” Aguilar told reporters.

Over the years, he has created other prostheses out of LEGO parts, improving the technology with each version. The more recent models rely on motors from various LEGO kits to bend the arm at the elbow joint and flex the fingers. Aguilar wears the prostheses only occasionally. Usually, they’re on display in his dorm room at the university in Barcelona, Spain, where he’s studying bioengineering.

Aguilar hopes his creations will show people with disabilities that nothing is impossible. And after he graduates, he says, he wants to design affordable artificial limbs for people who need them. “I would try to give them a prosthesis,” Aguilar said, “even if it’s for free, to make them feel like a normal person—because what is normal, right?”