I wonder why that is. Given that the container is sealed properly, and they use electronics with magnets, I just don't see any part that is subject to such massive wear.
EDIT: Thanks, jpatokal, that cleared things up.
EDIT: Thanks, jpatokal, that cleared things up.
https://en.wikipedia.org/wiki/Ferrofluid#Description
As a practical demonstration of this, there's an ancient ferrofluid exhibit (80's?) at a local science museum. While the fluid itself kinda-sorta "works" in that you get the pretty spiky shapes when zapped with an electromagnet, the edges and bottom of the glass case are thickly coated in viscous black gunk.
I think that the ferrous particles in ferrofluids are mere particles. They'd have to be very, very small to be classified as nano, and we've seen before that making particles of an ordinary material that small can change its properties, ala "transparent titanium dioxide".