Ferrofluids can be used to form liquid seals around the spinning drive shafts of motors found in a variety of devices, such as hard drives and servos.
Ferrofluids can be used in the production of audio speakers to remove heat from the voice coil and passibely dampen the movement of the cone.
The friction-reducing capabilities of ferrofluids when applied to a strong magent (for example neodymium) can create materials with very low friction.
Materials science research
Ferrofluids can be used to create images of ferromagnetic materials using a range of techniques.