An engineering undergraduate at MIT, Cory Lorenz, placed a drop of a ferrofluid between two closely-spaced glass plates, applied a constant vertical magnetic field, and then added a horizontal rotating magnetic field producing the interesting spiral design shown in the first group of photos top to bottom on left. But then Lorenz reversed the order of the applied fields, and saw a pattern top to bottom on right , that looked something like Native American art, a completely unexpected result.
Out of this work could emerge possible applications of ferrofluids to tiny machines, on the scale of micrometers or nanometers. Unlike electric fields, magnetic fields cannot produce sparks, so they might provide a good way to produce more reliable micro and nano-machines.
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Ferrofluid Fun Have you ever seen a liquid magnet? Magnetic particles, with surfactant molecules attached, suspended in a fluid to form a ferrofluid. The surfactant prevents clumping of the magnetic particles. Sequences of ferrofluid patterns formed by a series of applied magnetic fields top to bottom on left and with the same fields applied in reverse order top to bottom on right photos courtesy of Cory Lorenz. Latest from Physics in Action. In the video above , we see what happens when you take this glowing liquid, mix it with ferrofluid, dim the lights, and break out the magnets.
I know what I'm about to say makes absolutely no sense, but it looks like a religious experience for aliens. Not only is this chemical reaction incredibly beautiful and weird, it's loaded with fascinating physics, from what's causing those spikes, to why the mixture is organising itself into little worm-like patterns. First off, those spikes don't just form randomly - they all point in the same direction as the magnetic field lines coming from the magnet. You can see these lines in the video as they emanate up over the surface of the magnet, so when you're watching ferrofluid spikes move in response to a magnet, you're actually seeing the strength and direction of its magnetic field.
And what happens when the magnetic field is aligned horizontally to the ferrofluid? Well, as the spikes can only form vertically, you instead get the stunning, wormy patterns in the liquid. But why does ferrofluid react to a magnetic field like this anyway?
When you think about it, ferrofluid is almost an impossible liquid.
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