Medical 3D Printing & Bioprinting
With 3D Printing already into use in every sector, researchers are now experimenting 4D Printing that involves 3D-printing items that are designed to change shape after they are printed. Lewis and team, Harvard University, have evolved 3D-printed structures made of stiff cellulose fibers embedded in a soft hydrogel, whose orientation can be controlled after they swell up on immersing in water.
Source: http://www.livescience.com/53477-shape-shifting-4d-printed-objects.html