but idk about that pair of bellows, how to "drive" it and about its "fixed" volume with its flexible parts.
Not find; make. It just needs a couple of paddles hinged together with a plastic bag trapped between them. I see this as being literally a five minute job to get something working.
What is important is repeatabilty, so it should always be those 40ml/ 4cm pushing and pulling.
even if it works with bellows, isnt this still the easiest approach with some guarantuee about precision/repeatability compared to bellows?
Does it work the way i imagine it?
But what happens if the stepper misses one or more steps (or oversteps)?
Is the "forward" and "reverse" movement of steppers/gearmotors usually done with relays