I've only skimmed the article/paper and I also dont' understand, so I'm just as ignorant as you, but there is such a thing as a Tesla valve that is a static obj

I've only skimmed the article/paper and I also dont' understand, so I'm just as ignorant as you, but there is such a thing as a Tesla valve that is a static object that allows water to flow in one direction [0]. I would assume that maybe they can make little vortices of air/liquid (as the comment by kylebenzle suggests) that are dynamic and create a similar structure as it evolves. [0] https://en.wikipedia.org/wiki/Tesla_valve https://en.wikipedia.org/wiki/Tesla_valve