David Aguilar, a 19-year-old bioengineering student in Spain born without a right forearm, has built himself a robotic prosthetic arm using Lego bricks. "I wanted to...see myself in the mirror like I see other guys, with two hands," Aguilar said, adding that he aims to design affordable robotic limbs. Aguilar is currently using his fourth model of the prosthetic arm.