The Dot Matrix Display
this is the project, I initially started with. Each of four displays consists of 3 droplets in a row x 5 droplets in a column. The difference to a LED matrix is, that the droplets can't be turned off, instead they have to be hidden. As you can see on the old picture, the first idea was, to hide the droplets by moving them outside under a mask on top of the upper glass plate. This solution looked terribly, because the mask is shadowing the whole display.
New approach:
I use a bi-colored dielectric. The droplets that should be visible are over a white part of the dielectric and to hide them, they are moved over a dark part of the dielectric. The droplets are yellow, dark parts of the dielectric are blue. Because you would always see the bi-colored dielectric, the display is filled with blue colored oil as a filler liquid. I found out, that it is everything but trivial coloring a hydrocarbon with high color saturation. I successfully use a color that is made for coloring the wax of candles.