Ian Hua scratched at the joint on a green dismembered finger. His friend Christian Santilli held the remaining four fingers and a hand as he watched Hua, 13, work.

“We’re trying to get these fingers on the hand, but they won’t fit,” said Santilli, 12, of Shirley. His grandfather William McLeod, also of Shirley, added that excess plastic in the joints was making it difficult to put the prosthetic together.

Their project was one of 15 3-D printed prosthetic hands assembled Wednesday at the Mastics-Moriches-Shirley Community Library. They will be donated to disabled children around the globe as part of the “Hand Challenge.”

The Raptor Reloaded open-source prosthetics, printed on-site with library equipment, are a cheaper alternative to custom-fitted prosthetic hands, which can cost up to $10,000. It takes about 10 hours to print all the components, and then about two hours to put them together in the workshops. Once assembled, the hand is capable of basic movements and can grasp objects.

Recipients get paired with their prosthetics through Prosthetic Kids, the parent company for the South Carolina-based Hand Challenge. The group finds matches to nearby volunteer chapters worldwide.

Christian Santilli, left, and Ian Hua, both of Shirley, recently made a prosthetic hand using a 3-D printer at the Mastics-Moriches-Shirley Community Library. The limb will be donated to a child in need. Photo Credit: Newsday / Christopher Cameron

“Children grow out of prosthetics like they grow out of clothes — really quick,” said Stephen Burg, head of digital services at the library. “The [Prosthetic Kids] Hand Challenge organization, they take that prosthetic we make and match it with a child in need.”

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Burg and Nick Tanzi, assistant director of technology services at the library, said they heard about Prosthetic Kids when they began acquiring 3-D printers for the library, and decided to participate once they knew the printers’ capabilities and how to use them.

The library provides the prosthetics at a fraction of the cost of more sophisticated models, using only about $48 in materials, said Tanzi. He added that the hands, printed in bright-colored plastic, are designed to improve the recipient’s self-esteem.

“Missing a limb can really damage your self-confidence,” Tanzi said. “All of a sudden they have the Captain America hand and they’re the cool kid in the class.”

Tanzi said the library plans to expand its contribution to the Hand Challenge, hosting the event again during the school year with the offer of community credit for participating students. The library will hold a second Hand Challenge on July 12 from 3 to 5 p.m.