I needed a pump for a viscous fluid in one of my projects and it seemed a no brainer to uses ttsalo's version http://www.thingiverse.com/thing:15538 However, I have been hitting a wall in my tests and when discussing the matter it was pointed out that stator should be made of rubber to provide a tight fit with the rotor so cavities are sealed while moving. Not having elastic filament at hand nor experience on how rubbery it might be, I asked around. User A2 suggested on reprap forums http://forums.reprap.org/read.php?180,112397 to use oogoo silicone, which I did not know but it's just a google away. I've built a sample stator and matching rotor pump for a test and it works nicely. I modeled the cavity of the rotor, which can later be screwed it out from the silicone once cured. The funnel-like part can be used to contain the cavity you are modeling with oogoo silicone and act as the stator. These are some videos of its operation (forward) http://www.youtube.com/watch?v=DJLLvQahp9U http://www.youtube.com/watch?v=qcOW9YIsH_U and reverse http://www.youtube.com/watch?v=BdR1VQdDu4c Print both parts. I used the top of a Listerine mouth wash as a container for the stator. I filled it with ooogoo silicone (1 part of corn starch and 1 part of silicone, add a bit of oil-based color if desired). Then I screwed the cavity part out of the cured stator hours later. Now the pump is ready for action: insert the rotor and rotate it. Please note some play is needed so the motor will need to leave some play for the rotor top to go side to side.