Oh hey! Something that's finally relevant to my life in some way, shape, or form! Ferrofluids are really cool. They're basically small nanoparticles that have been dispersed in a liquid. By using these magnets, you can do cool things. When you use a regular really really strong magnet (neodymium) to influence ferrofluid, it just kinda follows the magnet. But ferrofluid becomes really, really fun when you start using electromagnets to influence them.
When you use a direct current (DC) electromagnet to influence ferrofluid, it does what the ferrofluid in the video is doing--being all spiky and whatnot. That has applications like sealing things or acting as a very fine lubricative agent, which is useful in many manufacturing situations. But where it gets really, really interesting (in my opinion) is when these ferrofluids are influenced by AC magnets. Basically, a direct current makes a current go "one way"--staying positively or staying negatively charged. But an alternating current oscillates between the two, and with it you can do some crazy stuff to ferrofluids. Because the ferrofluids are so small and so, so magnetic and paramagnetic, when influenced by a rapidly oscillating magnetic field, they vibrate because they keep trying to go whichever way the current goes. Basically why the ferrofluids vibrate gets really specific and science-y so I'll clarify only if anyone asks.
The bottom line is what I and many scientists are using this heating property of ferrofluids for: with enough specificity and a big enough magnetic field, ferrofluids can actually be used to thermoablate (break down) cancer tumors. Trials in Germany and European countries have shown this method as feasible; because of the small size, there's a lot of particle uptake by the cancer cells, and because of lower thermoablation point of cancer cells they explode, leaving the surrounding cells intact. My research specifically applies to using this thermoablation and these magnetic nanoparticles in order to break down clots. I've spent the last year and a half researching these things, so if anyone has any questions, AMA and I'll try to answer to the best of my ability :)