For those interested in a (easier to read) write up, see [1]

[1] https://physicsworld.com/a/feynmans-ratchet-is-built-at-last...

>Although the device has a very low efficiency, its creators believe it could have a number of applications, such as providing a better understanding of molecular motors that drive living cells.

Feynman always scoffed at the inevitable journalistic grab for 'applications' even in the realms of the purest of fields, and this feel like a rather ironic treatment - the 'application' is merely understanding! It's not an application - it's the entire point of the exercise!

Scientific tools such as microscopes are an application of the scientific theories that govern their operation.