http://www.sciencemag.org/news/2019/11/liquid-liquid-printing-method-could-put-3d-printed-organs-reach

3D-printed tissues and organs could revolutionize transplants, drug screens, and lab models—but replicating complicated body parts such as gastric tracts, windpipes, and blood vessels is a major challenge. That’s because these vascularized tissues are hard to build up in traditional solid layer-by-layer 3D printing without constructing supporting scaffolding that can later prove impossible to remove.

One potential solution is replacing these support structures with liquid—a specially designed fluid matrix into which liquid designs could be injected before the “ink” is set and the matrix is drained away. But past attempts to make such aqueous structures have literally collapsed, as their surfaces shrink and their structures crumple into useless blobs.