Five-year-old Katelyn Vincik was born without a fully formed left arm. The young girl, whom her parents describe as “very determined,” had been waiting for a functional prosthetic arm for quite a long time, after trying a cosmetic one that just wasn’t a good fit for her. 
Kimberly Vincik, Katelyn’s mother, spent countless hours on the Internet trying to find a solution for her daughter. She stumbled upon the Harris County Public Library in Clear Lake, Texas, which had a 3D printer available for public use. And although it had only really been used previously for science projects and other small items, the family set out to meet Jim Johnson, branch librarian, and Patrick Ferrell, who supervises the 3D printer, to see if the magic could be done.
“We were pretty upfront with the family. None of us had any experience with prosthetics. We know how to make 3D prints, and we know how to build things. But none of us have specific experience with prosthetics. And the family was willing to go along with it, even though none of us really knew exactly what we were doing. We were confident that we could make one. We’d just never done it before.” stated Ferrell on the initial meeting. 
Ferrell and his team took measurements for Katelyn’s arm and downloaded a design that had already been made by the online e-NABLE community. This means that the design for Katelyn’s arm, though not FDA approved, has already been tested and used by many people all over the world, upping his confidence that he could create something functional for the spirited little girl.
Katelyn’s prosthetic is made from non-toxic plastic polylactic acid and is pink and purple, her 2 favorite colors. She can control the arm by bending her elbow. When she bends her arm, the hand close, and when she straightens her arm, the hand opens.
Ferrell delivered the hand himself to Katelyn during a family gathering, stating that he was very honored to get to play a special kind of Santa Claus. 
Jim Johnson, branch librarian, says of the story:
“We help patrons every day find books or this, that or the other. And to some extent, we may get involved with them personally, just hearing their stories. But … to really make a true difference in someone’s life, in this case a little girl’s life, is just incredibly satisfying.” 
 Washington Post