Ferrofluids are known for their fascinating behaviors when subjected to magnetic fields, especially for the distinctive peaks they can form. In this video, we see a very thin ferrofluid drop on a pre-wetted surface just as a uniform perpendicular magnetic field is applied. Immediately the droplet breaks up into tiny isolated peaks that migrate out to the circumference. The interface breaks down from center, where the drop height is largest, and moves outward. Simultaneously, the diffusion of ferrofluid from the circumferential droplets into the surrounding fluid lowers the magnetization of those droplets, making it more difficult for them to repel their neighbors. As a result, they drift outward more slowly and get caught by the faster-moving droplets from within. (Video credit: C. Chen)
Breaking Up a Ferrofluid
