Ferrofluids are known for their fascinatingbehaviors 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)
For a little Friday fun, enjoy this timelapse of magnetic putty consuming magnets. Really this is a bit of slow-motion magnetohydrodynamics. The magnet’s field exerts a force on the iron-containing putty, which, because it is a fluid, cannot resist deformation under a force. As a result, the putty will flow around the magnet, eventually coming to a stop once it reaches equilibrium, with its iron equally distributed around the magnet. Assuming the putty is homogeneously ferrous (i.e. the iron is mixed equally in the putty), that means the putty will stop moving when the magnet is at its center of mass. (Video credit: J. Shanks; submitted by Neil K.)
Here a ferrofluid climbs a spiral steel structure sitting on an electromagnet. Magnetic field lines emanating from the sculpture’s edges tend to push the ferrofluid out into long spikes—part of the normal field instability—but surface tension resists. The short, somewhat squat spikes we see are the balance struck between these opposing forces. Though known for their wild appearance, ferrofluids appear many in common applications, including hard drives, speakers, and MRI contrast agents. Researchers have also recently suggested they might help understand the behavior of the multiverse. (Photo credit: P. Davis et al.)
In “Millefiori” artist Fabian Oefner mixes watercolors with ferrofluids to create bright fluid microcosms. Each photograph represents an area about the size of a thumbnail. Ferrofluids contain iron-based nanoparticles suspended in a carrier fluid and thus respond to magnetic fields. They can form sharp points, labyrinthine mazes, or even brain-like patterns depending on the magnetic field and the substances surrounding them. For more on this art project, see this interview with the artist. (Photo credit: Fabian Oefner)
In “Ferienne” artist Afiq Omar utilizes ferrofluids, magnetism, and vibration to create analog visual effects. Most of the dot and labyrinthine patterns result from the reaction of a ferrofluid submerged in a nonmagnetic fluid to an external magnetic field. Diffusion effects and surface tension instabilities are also visible in the way the darker ferrofluid breaks down in the carrier fluid. Also be sure to check out Omar’s previously featured fluid film “Ferroux”. (Video credit: Afiq Omar)
In this video, artist Afiq Omar mixes ferrofluid with soap, alcohol, milk, and other liquids to create a surrealistic fluidic dance. In addition to using different fluid mixtures, I suspect he accomplishes many effects using several different permanent magnets and electromagnets to vary the magnetic fields around the ferrofluid mixtures. (Video credit: Afiq Omar; via Wired)
Two dark areas of plasma, cooler than the surrounding fluid, dance and intertwine above the sun’s surface. Plasma, a rarefied gas made up of ions, is an electrically conductive fluid, shaped here by the magnetic field of the sun. Note how the strands pass material back and forth along the magnetic field lines. This timelapse video, captured by NASA’s Solar Dynamics Observatory, takes place over the course of a day and is captured in the extreme ultraviolet range.
The motion of ferrofluids in magnetic fields is always mesmerizing. Here a ferrofluid has been submerged in a clear alcohol-based solution in a shallow dish while a permanent magnet is used to perturb the liquid. Instead of forming its distinctive spikes due to the normal-field instability, the fluid forms ribbons and mazes due to the shifting magnetic field and the surrounding fluid.