Metering pump

[BrianT]

A looped tube, typically wrapping a bit more than 180 degrees and engaged by two roller bearing 'squeegees', is a very repeatable and reliable pumping system for medium temperatures and low pressures. Provided the discharge pressure is constant, typically ambient atmospheric, the volume delivered is very constant. It's called a peristaltic pump and is widely used in laboratories. The great advantage is nothing contacts the fluid except the tubing eliminating oxidation or contamination. The disadvantage is the squeezing action damages blood platelets or similar entrained cells or sacs. Stepper motor drive would probably need a gearbox as the forces to rotate the pump are unexpectedly high.

HTH
Brian

[skimask]

It's called a peristaltic pump and is widely used in laboratories.

Learn something new everyday...
I was trying to think of how the 'gas pump' thing with the 2 opposing pistons could be done, but the peristaltic pump seems like the easiest thing to do in this situation.