Three eighth-graders in Arkansas have used a 3D printer to create a prosthetic leg for a duck whose foot had been bitten off by a turtle. It took about 30 tries before students managed to build an appropriate leg. The duck later walked and ran like a normal duck. "I'm just so grateful that there are people that truly care, and they've gone out of their way to do everything they can to make it as comfortable for the duck," Patsy Smith, the duck owner, said this week.