So while Robinson's myoelectric arms were more complex than the body-powered ones that most kids with upper-limb differences use, they left a lot to be desired. The arm with an automatically closing hand, for example, is also known as a “cookie crusher” in the prosthetics community because kids who are not careful might accidentally crush something they forgot they were holding. The arm that came with a hand that opened when he lowered his arm made it difficult for him to pick up anything that dropped on the floor. When asked what he wanted out of a prosthetic, Robinson said, “When I’m doing my pushups, I want to open my hand. I don’t want to [have to] balance on it.” Two years ago, he stopped wearing his prosthetic altogether.

Even without the prosthetic, Robinson does many of the things kids his age like to do—play on the computer, compete on the swim team, study karate (he’s a green belt), and even throw perfectly round bowls on the pottery wheel. But in the coming weeks, Robinson’s prosthetic-free streak may come to an end. Last July, Robinson attended Superhero Cyborg Camp, a one-week design education workshop for kids with varying degrees of upper-limb loss. At camp, which was run by the San Francisco nonprofit KIDmob, Robinson and nine other students learned problem-solving, design and prototyping skills, and used them to design a new arm with its own superpowers.

For Robinson, being able to hold a Wii remote controller was an important power to acquire. Using old toys and parts donated from a hardware store, he fashioned together a prosthetic prototype made of a threaded metal rod onto which he could screw on different parts: his Wii remote, a fork, and a life-size version of the hands found on LEGO figurines.

One of the volunteers, a prosthetist named Erik Tompkins, helped him attach the rod to his arm by embedding it into a socket made of Aquaplast, a type of plastic that stays hard at room temperature but becomes gooey and moldable when heated to 140 degrees Fahrenheit, and securing it with masking tape. Though the prototype was less sophisticated than the prosthetics he had used, Robinson was much more excited to wear it and dream up fun, new ideas for his prosthetic.

In its short existence, KIDmob has been honing a design education curriculum that teaches “21st Century Skills”—a term that encompasses everything from problem solving to reasoning to communications. In the case of Superhero Cyborg Camp, KIDmob wanted to give its students a new framework for thinking about their limb difference. “Part of our intent was to invite them to consider the possibility that they’re not just limited to the prosthetic set on the market,” said KIDmob co-founder (and college friend of mine) Kate Ganim. “As the end user of the prosthetics, if they have an idea that’s not on the market, they could make it themselves.”