I've built a pressure control unit to keep the right pressure during printing.
I also ordered check valves to flush every printhead which should be delivered by Monday.
When I have everything together I will test the whole system and see whether it works but I think this attempt will be too complicated and expensive to be more than a prototype...
So the next thing I will test will be a printhead printed with a resin 3D printer to utilise the capillary effect and maybe smaller piezo discs.
Today I've ordered an Elegoo Mars so I can start working on 3d printed parts with small channels inside by next week.