From the New Scientist, a look at the application of inkjet printing technologies to biotechnology and tissue engineering: "droplets placed next to one another will flow together and fuse, forming layers, rings or other shapes, depending on how they were deposited. To print 3D structures, Forgacs and his colleagues alternate layers of supporting gel, dubbed 'biopaper', with the bioink droplets. To build tubes that could serve as blood vessels, for instance, they lay down successive rings containing muscle and endothelial cells, which line our arteries and veins. ... We can print any desired structure, in principle ... Other tissue engineers have tried printing 3D structures, using modified ink-jet printers which spray cells suspended in liquid ... Forgacs and a company called Sciperio have developed a device with printing heads that extrude clumps of cells mechanically so that they emerge one by one from a micropipette. This results in a higher density of cells in the final printed structure, meaning that an authentic tissue structure can be created faster."

Link: http://www.newscientist.com/article/mg19025474.300-print-me-a-heart-and-a-set-of-arteries.html