Ferrofluids - magnetically controllable fluids

Complex fluids with a flow behaviour differing significantly from the behaviour of normal liquids like water or oil exhibit numerous fascinating flow effects. This becomes especially interesting if the fluids properties and flows can be controlled by external forces.

Prominent examples for fluids allowing such an external control are suspensions of magnetic nanoparticles commonly known as ferrofluids. They exhibit normal liquid behaviour coupled with superparamagnetic properties leading to the possibility to control their flow and change their properties by means of moderate magnetic fields in the order of 10mT. With such fields, which can be produced easily with small electromagnets or by means of commercial permanent magnets, forces comparable to - for example - the gravitational force, can be exhibited to ferrofluids. The comparably easy magnetic control gave rise to the development of numerous applications of ferrofluids in various technical and medical areas which partly gained importance in everyday life.

Within the talk the origin of the magnetic influence, its fluid mechanical consequences as well as the application possibilities in mechanics, medicine and other fields will be outlined and illustrated with a couple of experiments.