This Harvard-made 3D printer can create complex metallic objects other printers can't. See, instead of spitting out one layer over another, the machine was designed to ooze out metal that immediately freezes solid. That allows it to print free-form patterns that look like they're suspended in air, like coils. Created by the university's Wyss Institute for Biologically Inspired Engineering and the John A. Paulson School of Engineering and Applied Sciences (SEAS), the printer uses "ink" composed of silver nanoparticles. A focused laser then heats the material and solidifies it as it comes out.