Meet the Octobot: a 3D printed autonomous soft robot from a team of Harvard University researchers with a pneumatic-based design. It is powered by gas under pressure, with a small amount of liquid fuel turning into a large amount of gas, which flows into its arms and inflates them.
The team used a microfluidic logic circuit to control the reaction. The entire system can be built using soft lithography, molding and 3D printing. More info is available here.