We have seen many 3D printed working engines in the past, but all of these required some other mechanics in order to run. Now a man named Don Clucas has designed what is believed to be the first fully 3D printed engine. Best of all, it runs on water as fuel. This means it is completely "green." These 3D printable Stirling engines are being made available to anyone free of charge. You can download the files from Clucas' website and print one yourself. All that is needed in additional to the 3D printed parts is some glue, and some other tools to assemble it. Then in order to run, it only requires a bowl of hot water, and some ice water on top. Check out details, pictures, and video in the full article: http://3dprint.com/21213/3d-printed-working-engine/ ‎
Below is a photo of a 3D printed Stirling cycle engine: