(Real fast)
To what degree, if any, has ferrofluid been tested for holding pressure against vacuum when applied between a centrifuge and fixed axis hub (Nautilus-X style, but seen on deep space designs like HOPE) ?
Any pointers to thermal constraints, electrical constraints, toxicity constraints.
( Is it purely theoretical ? )
Constraints would be inherent to the difficulty of exposing any fluid to a vacuum will result in loss of the fluid to space due to the vapor pressure of the liquid.
Are you basically looking for a ferrofluid to be a magical liquid seal against the vacuum of space? I don't see that ferrofluids have any special properties in this regards.
A magnetic field, of any strength, acting upon ferrofluid, in any manner, is not a force strong enough to counteract the natural tendency of a fluid, even of this kind, to evaporate into the vacuum.
Is that the essense?