Print your own prosthetic: 3-D printing lends a hand to affordable adaptive equipment (PHOTOS, VIDEO)

With a knife, a lighter, a screwdriver and some corn-based plastic, Dawson Riverman assembled himself a hand.

Strapped to the 13-year-old's left forearm, its modular blue fingers open and close as he extends and flexes his wrist. Tiny wire tendons articulate two Lego-like knuckles on each finger, grasping baseball bats and bike handlebars in place of the fingers he was born without.

Prosthetic hands like Dawson's are increasingly accessible thanks to the wonders of 3-D printing. The technology turns computerized design files into tangible objects, layer by razor-thin layer. Using heat as a hot glue gun does, 3-D printers spew out molten plastic, each coat corresponding to a thin cross section of the digital design.

When bolted, melted and strung together, the printed parts of Dawson's prosthetic create a functional, yet remarkably simple hand. Its mechanics are not unlike those of a toy robot arm one might win as a prize at the arcade.

"It's a lot like a screwdriver. It's something that's good for particular tasks," said Ivan Owen, a 3-D printing project manager at the University of Washington Bothell.

Drawing from his background in mechanical special effects, Owen co-designed one of the first printable hand prosthetics in January 2013. He later co-designed, printed and helped Dawson build his own hand in June 2014 after connecting with the Rivermans through a group called e-NABLE.

Now a global network of engineers, designers and 3-D printer owners, e-NABLE shares free downloadable prosthetic designs that can print a customizable hand for the cost of materials: about $50. Most of these volunteer-made hand, finger and arm prosthetics go to recipients for free, according the group's website.

Owen said comparable prosthetics made via traditional manufacturing usually cost $1,000-$3,000. "Our network is just approaching the same problem in a different way," he said.

Dawn Riverman's dream

Now that her son Dawson has a prosthetic hand created via 3-D printing, Dawn Riverman hopes to share the gift. She said she's collaborated with Dawson's school,

in Aloha, to raise money to buy the school a 3-D printer. She plans to help develop a curriculum around 3-D prosthetic printing, allowing students to manufacture a stock of prosthetics for donation on school mission trips.

For Dawn Riverman, Dawson's mother, that approach was a welcome one. She had searched since his birth for a practical and affordable solution for the unformed fingers that bulge gently from Dawson's otherwise typical left palm.

Riverman recalls a 5-year-old Dawson asking, "Mommy, why am I different? Why is my hand different?" Doctors couldn't explain it, she said. And neither could she, except to say that God makes each person special, and that Dawson's difference just happened of the visible kind.

After a bout of crying on the floor together, Riverman said, "I vowed I would find something for him."

Though he's soft-spoken and reserved, Dawson doesn't shy away from showing off that something.

"It was kind of confusing and tough at first, trying to understand how to move it and pick things up with it," he said, repeatedly opening and closing his plastic fist while seated in the kitchen of his family's Forest Grove home.

Now on his second such prosthetic, his affectionately named "little hand" has become an all-terrain-vehicle-steering, pencil-lifting, soccer-ball-stopping machine.

And while Dawson's new dexterity aid elicits a matter-of-fact "I want one" from his younger brother, Seth, it has its downfalls. The hand's not strong enough to apply the breaks on his bike or ATV, for example, and lifting small objects takes deliberate effort. Besides, there are certain things he's simply learned to do without two sets of fingers.

"I think because he's grown up his whole life without it, that it's sometimes awkward for him to put it on or think, 'Oh, I've got to put my hand on,'" Riverman said.

"At 4 and 5 years old, if we'd had this, he'd probably be wearing this all the time. Now, at 13, it's a little hard to change what he's done his whole life," she said.

Dawson said he thinks the prosthetic will be good for him in the long run, though he's still working out the kinks. In the meantime, he said he's happy to be able to swing a bat hard enough to get through a few bases in a neighborhood baseball game.

According to Owen, Dawson's experimenting with the hand has a happy byproduct: better design.

"Feedback from the end users has been one of the most useful and critical components of the design process," Owen said. "They're test pilots," he said, and their unique insight "has a larger impact than just the way they decide to use [their prosthetics]."

Owen predicts the functionality of prosthetics made on 3-D printers will only continue to improve as the e-NABLE community keeps throwing energy into making it so. People go into design and engineering because they want to have an impact, he said, and this is an avenue for it.

--Dillon Pilorget