Heart model

Print with flexible filament, I used NinjaFlex.

I suggest you print in a flexible filament to keep the valves mobile

There is 0.2mm distance between the flat part and where the valves start. Add a pause on layer before the valves start printing. Then apply a liberal amount of water-soluble gluestick where the valves will later be. After printing wiggle the valves free, wash off the glue and you got yourself some working valves!