In bioengineering it is important to have the ingredients to grow an organ, the correct environment for which those ingredients to grow, and of course a blueprint for them to grow on. Scaffolds have always been a hard obstacle to overcome due to the necessity of them to disappear after the growth has ceased. There have been many advances in that field: organic structures that will decay, and easily removable structures that act as molds for growth. Both of these are viable options, and both provide a different way of building organic structures. However when using a printer it is difficult to place a scaffold layer-by-layer, let alone have the printer lay cells out around an obstruction. Luckily, researchers have come up with a brilliant gel that will act as a place holder for the cells and tissues as they grow. Miranov et al. managed to produce a reverse-thermal gel that allows the printer to place cells whereever it is supposed to and have a gel wash over it before and after. This gel hardens immediately, rooting those cells in place and providing nutrients for them to grow, align, and attach. 
As you can see this process is much easier for a printer to achieve, and is the basis of scaffolding in bioprinting. The gel is solid at 37 degrees celsius, but becomes a liquid at 20 degrees celsius; therefore once growth is complete, the gel can simply be cooled and removed through dripping.
This, in a nutshell is the future of bioprinting scaffolds, and is going to form the basis of many other technologies.
Source: http://www.newscientist.com/article/dn3292-inkjet-printing-creates-tubes-of-living-tissue.html
Scaffolds: Holding an Organ Together
