This is fantastic, but another approach would be to use the things that are already small and learn how they work, and then maybe reprogram them (i.e. bacteria)

This is fantastic, but another approach would be to use the things that are already small and learn how they work, and then maybe reprogram them (i.e. bacteria). Also, as Richard Feynman pointed out (https://www.youtube.com/watch?v=4eRCygdW--c https://www.youtube.com/watch?v=4eRCygdW--c) at small scales water is thick like honey so it's probably more efficient to use a rotating turbine mechanism (i.e. flagella) for propulsion rather than trying to shrink paddles down to micron sizes. And almost foreign material that you put in your body will eventually be covered in bacterial biofilms. So might as well learn how to program and control the bacteria in the first place.