Please note, I have NOT built one of these yet and you will need a HEATED BUILD PLATFORM to print this object.Here is a pump that can be used for liquid or air. A piece of 3/8" diameter surgical tubing is looped through the 2 holes on the left side of the pump base around a 4 point rotor that compresses the tubing pushing the liquid or air ahead. This technique isolates the material being pumped from the mechanism itself. The rotor design could be improved greatly by placing wheels at the end of each point pushing against the tubing.UPDATE on 05/31/10: The STL files below look like they need something 'added' in order for SkeinForge to generate the GCODE. I have spent days trying to figure out why and how to fix it. I thought an STL file was mostly a list of ASCII lines and did not realize centering and size info are not being saved to the files.A user selected motor is mounted on the cover piece with the motor shaft attached to the 4 point rotor inside the base with 2 set screws. The builder would scale the 3 pieces to suite the end application. The cover is fastened to the base using #8-32 nuts and bolts on the corners of the 2 mating pieces. Using a stepper motor would allow the user to meter out a liquid while a brushless motor would provide a fairly quiet continuous flow of liquid or air.