[Christ]

Any chance that you could just place the acrylic panel in a clear vacuum bag, then lay out your cells face down on it, and vacuum laminate them to the acrylic? That way, there would be no way for the capillary effect to take place, since there wouldn't be a gap between the cells and the acrylic.

Another option might be to slather petroleum jelly on the cells before placing the acrylic back on top (after drying it all out). No idea what reactions might occur, though.