Behold ferrofluid, nanoparticles of iron coated in a surfactant and suspended in a solution of oil or water.
The surfactant can be citric acid or soy lecithin, among other things, and is used to stop them sticking together
It’s like magnetic dust.
Put a magnet under some ferrofluid and the particles align themselves in patterns to show the field.
The magnetic attraction is so strong, the ferrofluid will stick to a magnet and then you’ll never get all the iron particles off it. They’re stuck for good.
To prevent that happening, people usually play with ferrofluid inside a sealed container.
And play it is, this stuff is fun.
A friend of mine put a magnet above some ferrofluid with the lid off, and was abruptly COVERED in black gunk which stuck to him despite three showers. He wasn’t too happy, I think it smelled pretty bad. Hardcore.
Like most hardcore stuff, it’s been turned into kickass art. This video pretty well blew my mind.
Sachiko Kodama and Yasushi Miyajima created the piece, two ferrofluid sculptures which move synthetically to music. The two towers are iron cores of electromagnets sitting in a pool of ferrofluid. Etched with a helix pattern, the ferrofluid can move up the tower if the magnetic field is strong enough, stretching out in spikes as it goes.
The strength of the electromagnet is linked to metadata in the music controlling the voltage and AC pattern. To correct for the time delay, the electromagnet controls starts early so the maximum size of spikes coincides with beats of the music.
The result is a choreographed pattern that dances and winds like a living thing.
You can buy ferrofluid from Emovendo.
Hat tip to @DrSkySkull, who bought some ferrofluid as a classroom demo and supplied the picture at the top of the article.