The Applications Of Ferrofluid

A ferrofluid is a materiel with a particularly interesting property: It is a liquid, and behaves exactly like a liquid, in that it flows and drips etc., but it also has magnetic properties, which are usually consigned only to solids. The magnetic properties are exhibited only when in the presence of an externally-applied magnetic field.

They work by having extremely small (on the nano-scale) particles of a ferrite salt suspended in either water or a solvent. Each particle has previously been coated with what is called a surfactant before being placed in the mixture. Surfactants have many applications, but primarily their job is to allow the easier spreading of a solid through a liquid. In this case, they help to ensure that the ferrite salts do not become too clumped together in the liquid.

NASA discovered these fluids nearly 50 years ago, where the advantages were noted immediately: To have a liquid that can be forced to flow by the application of a variably changing magnetic field has multiple applications.

Its Use In Hard Disks

The most common application, which almost every person in the western world now makes use of, is their use in hard disks and other electronic devices. They are typically forced into the gap around the spindle of a hard disk - they are held in place by the magnetic field, and this protects the interior of the disk from dust (any dust entering the interior of a hard disk is likely to irreparably damage it). They are also used in many mechanical devices to reduce friction.

Use in Loudspeakers

Loudspeakers contain a gap surrounding the audio coil. This gap would normally allow too much movement of the speaker cone when the sounds are loud. This means that modern speakers are filled with a ferrofluid, which is held in place by the magnetic field. An interesting property of this is that the fluid's magnetic attraction reduces as heat increases. This means that, as the speaker cone warms, the fluid closer to it sinks away and the colder fluid flows into its place - this provides an effective cooling system and ensures that the speaker will not have any damage from the heat.

There are multiple other applications of this strange material, which ranges from the electronics industry, to medical; it is used in some art.

Producing the Fluid At Home

If you are interested in this, you will find that ferrofluids can be extremely expensive to purchase unless you happen to own a company that is a able to purchase vast quantities at once. It is fully possible, however, to produce your own fluid, which is of a high enough quality to experiment with at home.

Try this: Purchase some magnetic ink developer, some kerosene and some citric acid. The ink developer acts as the ferrite salt and the citric acid as the surfactant. Mix these two solutions together and then pour into the ink developer until you have a thick mixture. Place a magnet near to the solution and check the effects.

The applications of ferrofluid seem almost endless since its discovery almost 50 years ago people have thought of uses for it in almost every technology, and its use has lowered prices and improved performance of hundreds of technologies.

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