Photo credit: think.obscure
A ferrofluid is basically a liquid which becomes strongly magnetized in the presence of a magnetic field. They’re mainly composed of nanoscale particles (diameter usually 10 nanometers or less) of magnetite, hematite or some other compound containing iron. Continue reading for more.
Particles in ferrofluids are dispersed in a liquid, often using a surfactant, and thus ferrofluids are colloidal suspensions – materials with properties of more than one state of matter. In this case, the two states of matter are the solid metal and liquid it is in.
True ferrofluids are stable. This means that the solid particles do not agglomerate or phase separate even in extremely strong magnetic fields. However, the surfactant tends to break down over time (a few years), and eventually the nano-particles will agglomerate, and they will separate out and no longer contribute to the fluid’s magnetic response.
3. Babylonian Towers
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.
2. Meat Grinder
Ferrofluids have friction-reducing capabilities. If applied to the surface of a strong enough magnet, such as one made of neodymium, it can cause the magnet to glide across smooth surfaces with minimal resistance.
NASA has experimented using ferrofluids in a closed loop as the basis for a spacecraft’s attitude control system. A magnetic field is applied to a loop of ferrofluid to change the angular momentum and influence the rotation of the spacecraft.