Ferrofluid - The Magnetic Liquid

with Mark Miodownik

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Dripping with Magnetism.

Materials scientist and Christmas Lecturer Mark Miodownik demonstrates some of the weird properties of ferrofluid. This liquid is literally 'dripping with magnetism', containing a suspension of ferromagnetic nanoparticles that make the liquid responsive to external magnetic fields, generating unusual patterns, shapes and motion.

Using a strong neodymium magnet and a large steel bolt, Mark demonstrates the strange and beautiful patterns the fluid forms in response to the magnetic field.

Ferrofluids do not tend to maintain their magnetic behaviour in the absence of an external magnetic field and are therefore known as superparamagnets.

You can also watch liquid oxygen exhibit its paramagnetic behaviour here.

Find out more about other unusual and strange materials in Mark's Friday Evening Discourse here.

Mark also gave the 2010 Christmas Lectures which are available to stream in full on the Ri Channel.

Music: Latché Swing - Menilmontant




Professor Mark Miodownik
Royal Institution, London
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The Royal Institution

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It's a very weird liquid, this.

On the scale of 1 to 10 of weirdness this comes about 433.

Is it the blood of some strange machine, you ask? Do you ask that? I ask that. No, it's not.

This stuff is very odd. It's called a ferrofluid, or a magnetic liquid, and what's happening here is there's a magnet down there and a bolt in which the magnetic field's been channelled through. And the liquid is reacting to the magnetic field. That's really odd. Not many liquids do that.

That's because this liquid has got tiny nanoparticles, magnetite, in it. Now, normally if you put that kind of particle in a water solution, it'll just get ripped out by the magnetic field.

In this case, it's been coated with a surfactant, and that surfactant is an interface with the water, which loves the water. So they're held into the water, and that makes the liquid behave as if it's magnetic. It's pulled along with the particles and so it's kind of channelled into these different shapes, which are all defined by the magnetic field.

So you can confine a liquid with a magnetic field just by putting these tiny little magnetic particles in there. So nanotechnology, at its most beautiful.

Car manufactures have used it because, in a way, what you can do is you can kind of confine a liquid and make it either viscous or quite runny with just controlling an electromagnet. And that means you can make a car suspension either very hard or very soft at the touch of a button.

Now, that sound's like quite a cool application, I agree, but, I think, we can come up with something better. Although personally, I haven't yet, except for the bolt. It's pretty cool.


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