Watch this mesmerising video of a gold ferrofluid display
This material, created by Nasa, goes wild in the presence of magnets.
Magnets are cool. Everybody knows this.
But this liquid – known as ferrofluid – is particularly cool, because of the way it moves when you hover a magnet over it.
Ferrofluid, in the presence of a magnetic field, becomes extremely magnetised, thanks to the iron-based nanoparticles inside it.
A clip posted by Dr Raymond Hall, a professor of physics at California State University, Fresno, on his Instagram account @physicsfun shows how waving a magnet around the ferrofluid turns the bulbous liquid into a much spikier structure.
Ferrofluids aren’t strictly a liquid – they are actually a type of colloidal suspension, ie a mixture of particles of one substance distributed throughout a second phase (that may be solid, liquid or gas).
In this case, the gold-coloured ferrofluid is made up of nanoparticles coated in a surfactant to stop them from clumping together by lowering the surface tension – a phenomenon where the elastic tendency of a fluid surface makes it acquire the least surface area possible.
Another example of a colloidal suspension, albeit not a magnetic one, is milk – which is butterfat dispersed in a water-based fluid.
The magnetic field provided by the magnet creates peaks and valleys in the ferrofluid, like a 3D version of the bar magnet and iron filings experiment you did at school.
Invented by Nasa to help move rocket fuel in zero gravity, ferrofluids are now used to form seals in hard drives, and to disperse heat in loudspeakers.
And if you want to bring the science home and have one of these gold ferrofluid displays on your desk, you can get one here.
