There are many commercial applications for ferrofluids--speakers and hard drives being the most common. The oily fluid prevents debris from entering hard drives when a small amount is placed between the magnets and shaft. In the case of speakers ferrofluids remove heat from the voice coils and help dampen the cone movement. My own interest in the black ooze is a desire to create custom cases for electronics. And even more fun can be had making dynamic molds by pouring a hardening agent over the fluids.
If you are still wondering what ferrofluids are take a look at this video:
Controlling the shape of ferrofluids and then "freezing" them in place could be another tool for inexpensive desktop fabrication. Combining two unusual uses of magnetic fluids invites further empowerment for the maker. This French nail polish has magnetic particles that can be triggered into elegant patterns after being applied and before setting up. And Martin Frey has a dynamically controlled ferrofluid art piece titled SnOil that offers 144 pixels that is a low-res display.
I plan to try the chemical ferric chloride approach used in DIY option 2 substituting the kerosene for biodiesel and the oleic acid for citric acid. In order to get a freeze effect I will begin with pouring epoxy resin over the ferrofluid. Then observe the fluid's behavior. Can it hold a shape long enough for the resin to setup? That, we shall see.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.