We have been seeing these gifs for some time now... often called 'science gifs' and 'amazing.' But what is the science behind ferrofluids? Ferrofluids are actually ferromagnetic particles (particles which can be magnetized) by means of an external field - often forming permanent magnets. At slightly larger than 15 nanometers, these particles act as domains and individual atoms clump together to display magnetism.
But smaller than 15 nm, the particles do not retain any alignment to an externally applied field. They 'flip' once the external magnetic field is removed. A ferrofluid uses this effect of superparamagnetism and once nano-sized particles of a ferromagnetic material are suspended in a surfactant, you have a fluid which can be easily magnetized and demagnetized.
Superparamagnets: Superparamagnets have fluctuating magnetic moments with no applied field, but with an applied external magnetic field they become magnetized easily. This effect is size dependent. What are magnetic moments? These are nothing but the spin of the electrons in a material.
Uses: Ferrofluids are made up of tiny magnetic fragments of iron suspended in oil (often kerosene) with a surfactant to prevent clumping (usually oleic acid). There are many commercial applications for ferrofluids--speakers and hard drives being the most common. The oily fluid prevents debris from entering hard drives when a small amount is placed between the magnets and shaft. In the case of speakers ferrofluids remove heat from the voice coils and help dampen the cone movement. They are also being studied as a contrast agent in MRI scans.
But smaller than 15 nm, the particles do not retain any alignment to an externally applied field. They 'flip' once the external magnetic field is removed. A ferrofluid uses this effect of superparamagnetism and once nano-sized particles of a ferromagnetic material are suspended in a surfactant, you have a fluid which can be easily magnetized and demagnetized.
Superparamagnets: Superparamagnets have fluctuating magnetic moments with no applied field, but with an applied external magnetic field they become magnetized easily. This effect is size dependent. What are magnetic moments? These are nothing but the spin of the electrons in a material.
Uses: Ferrofluids are made up of tiny magnetic fragments of iron suspended in oil (often kerosene) with a surfactant to prevent clumping (usually oleic acid). There are many commercial applications for ferrofluids--speakers and hard drives being the most common. The oily fluid prevents debris from entering hard drives when a small amount is placed between the magnets and shaft. In the case of speakers ferrofluids remove heat from the voice coils and help dampen the cone movement. They are also being studied as a contrast agent in MRI scans.
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