“Using new, specialized 3D printing technology, engineers were able to deposit a bio-friendly hydrogel into a cantilever design just seven by two millimeters in size, seeded with heart cells from a rat. The cells grew into a matrix and began doing what heart cells do best — beating. By depositing the cells in a particular arrangement throughout the structure, and coaxing them to grow in the desired ways, the beats eventually produced controlled forward movement. After a number of false starts and inferior designs, the researchers were able to build a bio-robot that moved consistently — albeit at only 236 micrometers per second, or 0.00053 miles per hour.”

http://www.extremetech.com/extreme/140627-3d-printed-biobot-track-and-destroy-toxins