I learned OpenScad tonight! Thought I'd try out making an ultra-simple model of a 5-stage disc pump. I drew in some red lines to show the path of the air molecules through the pump. This is massively simplified, and the spacing between the discs has been wildly exaggerated for clarity. In a real pump the discs would need to be MUCH closer together to be effective at all. Additionally, this render just shows one hollow disc per stage. Many more hollow discs could be added adjacent to one another within each stage in order to increase gas throughput.