“The Flow II” film by Bose Collins and colleagues features a ferrofluid, a magnetically-sensitive liquid made up of a carrier fluid like oil and many tiny, ferrous nanoparticles. Although ferrofluids are known for many strange behaviors, their most distinctive one is the spiky appearance they take on when exposed to a constant magnetic field. This peak-and-valley structure is known as the normal-field instability. It’s the result of the fluid attempting to follow the magnetic field lines upward. Gravity and surface tension oppose this magnetic force, allowing the fluid to be drawn upward only so far until all three forces balance. (Video credit: B. Collins et al.)
“The Flow II”
