I would like to 3d-print a structure made of two connected compartments and fill the whole thing with a liquid. Both compartments are approximately spherical but one is about 1mm3 and the other 1cm3. They will be connected by a hole of about 1 mm diameter.

I will replace the solution every two days and it's crucial that the solution I put in the big one, will also move to the small one.

Will diffusion of the solution from the large compartment to the small be severely limited when I replace it (for example, because of huge pressure on the hole which will essentially shut the small compartment)? Or is this non-sense and the solution will spread to the small compartment without problems?


There are a couple of reasons why you might get trapped air (surface tension and viscosity, e.g.), but you can bleed it out through a strategic exit route. Can you add a vent to the small volume? Even then, if you cannot see in there, precise weighing may be the only way to satisfy yourself of complete filling.

  • $\begingroup$ I can definitely make sure there is no air trapped but do you think a similar 'trap' for liquid instead of gas is nonsense? (given that the liquid will be of the same kind in the small compartment, not more viscous or anything) $\endgroup$ – matteoeoeo Mar 18 '18 at 17:00
  • $\begingroup$ I slightly misunderstood your question. Are you worried that you cannot remove all the old solution from the small compartment at replacement time, and so you want the new solution in the large one to diffuse with that in the small one so that they are they same concentration? $\endgroup$ – Tom B. Mar 18 '18 at 18:21
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    $\begingroup$ My guess is that diffusion will not be impeded in that case, but I don't know enough to guarantee it. $\endgroup$ – Tom B. Mar 19 '18 at 23:26

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