http://www.scientificamerican.com/articl...d-windpipe
Quote: Problems with the trachea, however, lend themselves to 3-D printed solutions because the organ's ridged tubelike structure is simple. After testing their idea in piglets, Green and his colleagues were confident a printed device would work. Scott Hollister, a professor of biomedical engineering at Michigan was in charge of designing sleeve that would wrap around the outside of the floppy airway. The sleeve's structure allows it to expand as the airway grows and develops while simultaneously resisting spasms that pull inward, thereby collapsing the airway.
The team first used a computed tomography (CT) scan to sketch out Kaiba’s airways. From those images, they then sculpted a three-dimensional printed cast that had the same shape as Kaiba’s collapsed bronchus. Using that cast they created the sleeve or splint that would wrap around the bronchus. It took several tries but the researchers were eventually able to create a perfect fit. The next step was to sew the tissue of Kaiba’s bronchus to the inside of the sleeve. The team needed to obtain an emergency-use approval from the U.S. Food and Drug Administration before they could implant the device. "When we put the splint on, we saw his lungs move for the first time," Green says. As Kaiba grows, the device should expand with him.
The tube itself was printed in layers of a biocompatible plastic called polycaprolactone. The 3-D printer heats up a powdered form of the plastic until it melts and can be extruded in a paste. After a few years inside a body the tube will dissolve—it is made of the same material used for sutures—and by that time his bronchus should have grown strong enough to function normally.
