Sometimes physics imitates art. 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. A video of this transformation won a place in the annual APS Division of Fluid Dynamics Gallery of Fluid Motion, and can be seen with Windows Media Player or Quicktime (click on video in item 1 under V. Ferrohydrodynamics).

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.

 

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)