The most interesting technique I hadn't heard of before (there were a couple!) was using a material that, when cooled, turns into a liquid. It is named Pluronic

The most interesting technique I hadn't heard of before (there were a couple!) was using a material that, when cooled, turns into a liquid. It is named Pluronic ink, but they refer to it as 'fugitive ink'. This enables them to print a structure that incorporates this material, cool the whole thing down, and suck out the liquid. They use this technique to lay down 3d channels in printed bio-materials, which they then infuse with endothelial cells to create blood vessels. Amazing! The other ink dispensers would take their turn, laying down a lattice of collagen and fibroblasts that would solidify around the network of fugitive ink, encasing it in tan-colored living tissue. To drain the fugitive ink, Kolesky would place the tissue on a chilled stone cube; this would cause the ink to change from a gel to a liquid, after which he could then extract it with a small suction device. The end result would be a block of living tissue suffused with intricate vessels capable of carrying nutrients to the cells within. The last step was to me the most remarkable. Once the vessels were empty, Kolesky would take a suspension of endothelial cells—the cells that line the insides of blood vessels—and inject it into the vessel network. The cells would settle in and multiply to line the insides of the channels, effectively turning the channels into blood vessels. And then the cells would spread—they would begin to branch off the existing vessels and form new ones. In effect, Lewis and her team have created an environment that the cells consider home—it is far more natural to them than a petri dish or the inorganic scaffolds that had previously played host to cultured tissues.