Principal Investigator Gareth McKinley
Project Website http://web.mit.edu/nnf/ferrofluids.htm
Ferrofluids are the world's first succesful nanotechnology. First invented by R. E. Rosensweig in the early 1960's, these remarkable fluids are a continuous suspension of permanent nano-magnets. Synthesized by either chemical or physical processes, Ferrofluids can either be an aqeuous or organic suspension of magnetite, maghemite, and other hard magnetic materials. Current applications included liquid rotary o-rings for hard disc drives and vacuum systems, as well as voice coil coolants. Ferrofluids are researched here at HML for their applications in microfluidics and nano-liquid technology. The limitations of micro-fabrication can be avoided throigh the use of magnetic liquid micro-pumps, valves and other fluidic control hardware. The dificulty actually lies within the creation of the magnetic field. To that end, much NNF research is devoted to low-power, coil-less magnetic field generators.
Ferrofluid puddle undergo a normal field instability that is induced by magnets below the petri dish. The magnets are moved upwards to the dish at a slow enough rate so that the instability peaks can be seen as they form. The inter-peak spacing is approximately given by the Taylor wave-length for regular hydrodynamic instabilities, but the peak amplitude is a function of field intensity. Notice that as the magnets get closer, there is a change in the peak distribution from a hexagonal to square array. As the name implies, this instability is induced by the existence of a mgnetic field that is normal to the fluid surface. The field intensity ranges from zero (quiescent pool) to about .3T at the end of the movie.