"Stevenson is handicapped in a small way, in a way that's not as bad as some of the other children. Yet his hands are holding him back," Mr Marshall said. "He can do so much more. He has the potential."
When he returned home to California, Mr Marshall came across an article about Richard van As, a South African carpenter who had lost some of his fingers in a sawing accident in 2011. Mr van As had built himself a plastic prosthetic using a 3D printer, which he named "Robohand".
After making contact, the two men worked together to create a Robohand for Stevenson, which was shipped to Haiti and fitted by Mr Iwalla's team last month.
Staff at the orphanage for disabled children say the prosthesis has enabled the 12-year-old to take part in previously impossible activities such as playing catch. Thanks to his new hand he may even go on to be able to write.
3D printing has already been used to build clothing, cars, guns and musical instruments, and Stevenson is one of many children to have benefited from Mr van Ass invention: the first recipient of a Robohand was a five-year-old South African boy, Liam Dippenaar, who had been born without fingers on his right hand. Printing each prosthetic costs only around £180.
Last year, in Southern Sudan, a 16-year-old refugee named Daniel, who had lost both his arms in an explosion, was fitted with a 3D-printed prosthetic limb that allowed him to feed himself for the first time in two years. The organisers of "Project Daniel" hope to bring the Robohand to as many as 50,000 amputees affected by wars in Africa.
Stevenson told Reuters that his new hand, which is articulated by movements in his wrist, is "great".
He explained: "Now I can take a balloon with it. I can score at basketball. I can hold a TV remote and push my friends on their wheelchairs. I can hold a water bottle, a bag. I like it a lot."
Mr Iwalla said, "Some patients care more about cosmetics. But for Stevenson function is the most important criteria. That's what is in his mind. His robot hand makes him happy, makes us happy."
- The Independent