Here is more about ferrofluid, made by suspending nanoscale ferromagnetic particles in a carrier liquid. It was originally invented in 1963 by NASA as a way to pump fluids with magnetic fields. Here is a page describing the work on ferrofluid thrusters at Michigan Technological University, “Spiky Ferrofluid Thrusters Can Move Satellites”.
The technology is the subject of U.S. Patent 10,330,090 [PDF] “Generating electrospray from a ferrofluid”, granted in June 2019.