Just simple bee queen excluder sheets. At 4.1 mm grid size it will allow for worker bees to move freely within the hive (i.e. between supers) while limiting the queen to the nest. Queen excluders have a number of advantages but also a few drawbacks. The main issue with printed queen excluders is that you are limited in size to whatever your printer can print.

The queen excluder comes in 2 flavors, one is 20x20 cm (which should roughly fit a Mini+ hive), the second is round (20 cm diameter). The way to use these on larger size supers/hives (e.g. Langstroth or Dadant) would be to insert a wooden board with a 18x18 (round or square) hole in the center covered by the excluder.

Hope your bees like it. Here is a collection of some of my Beekeeping Designs on Thingiverse.

Should be an easy print. Print with 100% infill and 0.28 mm layer height. No supports or plate adhesion needed. Make sure to remove any sharp edges so the bees won't hurt themselves.

Enjoy!