What is Ferrofluid?
In short, it is a liquid that responds to magnets and magnetic fields. The longer answer is ferrofluid is an extremely fine powder, coated with a soap-like material called a surfactant, suspended in a mineral oil liquid base. The resulting magnetic suspension is called a ferrofluid. When no magnetic field is present, ferrofluid behaves and flows like a normal liquid. However, when a magnet or magnetic field is introduced, the ferrofluid is attracted to the field. Spikes then form along the magnetic field lines when the magnetic surface force exceeds the stabilizing effects of fluid weight and surface tension. The results are spectacular and sometimes other-worldly. The photos below show a 7/16″ diameter x 1.5″ neodymium cylinder magnet with ferrofluid on the north pole. The first picture shows the early formation of magnetic spikes. As more fluid is carefully added, the spikes become more pronounced, forming a ferrofluid “tree” as seen below. This photo shows a ferrofluid “acorn”. The
A ferrofluid is a liquid which contains incredibly small pieces of a magnetic substance. Common metals used are cobalt, magnetite and iron. It is important that these pieces of metal be small enough that they remain in a liquid state when exposed to a magnet. This threshold is somewhere on the order of ten nanometers. When many people use the term ferrofluid, they are also referring to magnetorheological fluid, a fluid similar in all ways to a ferrofluid, except that the size of the particles is larger. This difference in size means that the fluid becomes solid when exposed to a magnetic field, then reverts to a fluid when the magnetic field is removed. The particles in a ferrofluid may be suspended in one of many different substances. The most common fluids used are water and oil. Added to this basic fluid is some sort of surfactant to make the fluid more stable. One of the most important military applications of a ferrofluid was in the late 1980s as a form of radar-repulsion. Painted
