Invented in 1963 by NASA’s Steve Papell as a liquid rocket fuel that could be drawn toward a pump inlet in a weightless environment by applying a magnetic field, a ferrofluid is basically a liquid that becomes strongly magnetized in the presence of a magnetic field. They are colloidal liquids made of nanoscale ferromagnetic, or ferrimagnetic, particles suspended in a carrier fluid (usually an organic solvent or water). Each tiny particle is thoroughly coated with a surfactant to inhibit clumping. Continue reading for five more interesting things you may not have known about ferrofluids.
5. They Need Magnets to Work
Ferrofluids usually do not retain magnetization in the absence of an externally applied field and thus are often classified as “superparamagnets” rather than ferromagnets.
4. Rock Band Featured Material in Music Video
The Australian electronic rock band Pendulum used ferrofluid for the music video for the track, Watercolour. The design house Krafted London was responsible for the ferrofluid FX in the video. The post-metal band Isis also uses a ferrofluid in the music-video for 20 Minutes/40 Years.
3. Cools Voice Coils
Ferrofluids are commonly used in loudspeakers to remove heat from the voice coil, and to passively damp the movement of the cone. They reside in what would normally be the air gap around the voice coil, held in place by the speaker’s magnet. Since ferrofluids are paramagnetic, they obey Curie’s law and thus become less magnetic at higher temperatures. A strong magnet placed near the voice coil (which produces heat) will attract cold ferrofluid more than hot ferrofluid thus forcing the heated ferrofluid away from the electric voice coil and toward a heat sink. This is a relatively efficient cooling method which requires no additional energy input.
2. Used in Hard Disks
Ferrofluids are used to form liquid seals around the spinning drive shafts in hard disks. The rotating shaft is surrounded by magnets. A small amount of ferrofluid, placed in the gap between the magnet and the shaft, will be held in place by its attraction to the magnet.
1. Can Self Assemble
Ferrofluids can be made to self-assemble nanometer-scale needle-like sharp tips under the influence of a magnetic field. When they reach a critical thinness, the needles begin emitting jets that might be used in the future as a thruster mechanism to propel small satellites such as CubeSats.