Ferrofluids were developed by NASA in the 1960s. The space agency wanted a way to move liquid fuel through a rocket in space, in the absence of Earth’s gravitational pull. They proposed a liquid that could be controlled with magnets. NASA eventually shifted its focus from liquid to solid fuels, so ferrofluids never took off. But engineers have found many other uses for them.
For example, a magnetic field holds ferrofluid in place around the spinning center of a computer’s hard drive, which stores data. The fluid prevents debris from getting into the drive’s interior, which could cause it to malfunction. Ferrofluids are also used in audio technology and aviation, and researchers are exploring possible applications in medicine and astronomy.
Scientists have discovered that in the presence of a magnet, a ferrofluid’s surface forms spikes. “The shapes result from the balance of forces acting on the fluid,” says Isaac Torres Díaz, a chemical engineer at the University of Alabama in Huntsville who studies magnetic fluids. One of those forces is surface tension, resulting from attraction among molecules at the fluid’s surface. Then there’s the magnetic force, which pushes and pulls on particles in the fluid. Together, they cause sharp peaks to jut out from its surface.