Albert Manero, a Fulbright scholar and University of Central Florida mechanical engineer, built the arm. As part of the volunteer group Limbitless Solutions, Moreno and student engineers design affordable prosthetics using 3D printers.

“We were all bound to the belief that no one should profit from a child in need of an arm,” Manero said in a statement. The materials for Alex's new bionic arm cost less than $350.

The artificial limb uses electrical muscular signals from a wearer to guide its movements. After Manero's work drew the attention of Microsoft's The Collective Project, an initiative to spotlight students who do social good, they recruited Downey Jr. to present the final arm, in his Tony Stark persona.