Growing tissues and organs in a bioreactor is a laborious business, but recent improvements in 3D printing offer the tantalising possibility of manufacturing a new heart rapidly and to order. 3D printers work by breaking down a three-dimensional object into a series of thin, two-dimensional “slices”, which are laid down one on top of another. The technology has already been employed to manufacture complex engineering components out of metal or plastic, but it is now being used to generate tissues in the laboratory. To make an aortic valve, researchers at Cornell University took a pig’s valve and X-rayed it in a high-resolution CT scanner. This gave them a precise map of its internal structure which could be used as a template. Using the data from the scan, the printer extruded thin jets of a hydrogel, a water-absorbent polymer that mimics natural tissue, gradually building up a duplicate of the pig valve layer by layer. This scaffold could then be seeded with living cells and incubated in the normal way.
https://www.theguardian.com/science/2017/may/23/robot-hearts-medicines-new-frontier