Researches in Illinois have used 3D printing to help in the creation of what they refer to as Bio-bots. They are biological robots that use 3D printed hydrogels and real muscle in order to move via electric impulses. The 3D printing allowed them to make the hydrogel backbones which the muscle is anchored to. This is really incredible. They plan to next use neurons in order to allow the bio-bots to respond to stimuli.

Read more about this at http://3dprint.com/7907/3d-printed-bio-bots/