David Aguilar was born in Andorra, the tiny mountain country wedged between Spain and France, with a rare genetic condition that left him without a right forearm. Growing up, he felt the difference sharply, especially around other boys, and he wanted to look in the mirror and see two hands like everyone else.
The tool he reached for was the one he loved most. At nine years old he built a simple arm from ordinary LEGO bricks. When those turned out to be too fragile for opening doors and gripping objects, he moved on to LEGO Technic, the line built around beams, gears and axles.
Over the following years he dismantled helicopters, jets and cranes from his sets and rebuilt their parts into a series of arms, each one more capable than the last. At 18 he completed a version he called the MK-I, after the suits in Iron Man, with an elbow that bent and a grabber that could pick things up. Guinness World Records named it the first functional LEGO prosthetic arm.
Later models added electric motors, and one has five moving fingers. Aguilar went on to study bioengineering at university, with the goal of making working prosthetic arms cheap enough for people who can’t afford conventional ones.
The boy who once wanted to look like everyone else ended up building arms for other children who felt the way he had.