Spinning magnetic field creates beautiful vortices out of ferrofluid
Step 1: Attaching Magnets to a Drill
I attached a 5mm cube magnet to a Dremel so that its poles are facing a 90 degree angle with respect of the spinning axle. This creates a spinning magnetic field. Because of the high rpms, magnetic locking isn't enough. Tape adds strength to the connection and makes the experiment more safe. Tape isn't ideal but has worked decently for me before. With the 5mm cube magnet, the desired vortex effect was visible from distance of approx 1 inch. (The magnet is spinning on top of the ferrofluid) I didn't want the spinning magnet to be visible on the video so I added a half inch diameter sphere neodymium magnet on each pole. Then added more tape. Now the distance between the spinning magnet and the ferrofluid ,where the vortex effect could be seen was maybe 2 inches. With this much weight and high rpms the experiment gets hazardous and is not good for a powertool, because the balance isn't perfect and in fact holding the dremel was quite uncomfortable because of rough vibrations.
Step 2: Water, Ferrofluid, Food Dye
Always when working with ferrofluid the first step should be putting on gloves, covering all near surfaces carefully and putting on clothes that wont matter if they stain. Using eye protection is also highly recommended, first of all because the magnets can shoot with a high velocity from the powertool but also because ferrofluid can stain eyeballs. To my knowledge ferrofluid isn't very toxic, but having a black sclera will look super disturbing. I used a big black opened up carbage bag to cover all near surfaces. The stuff is really messy and hard to clean up! This experiment can make ferrofluid splatter all over the place in case the spinning magnet gets too close to the ferrofluid.
I added water and food dye on a disposable plate. At first I was using one plastic container, but cleaning the container in between the shots was pain in the ass so using disposable plates made my life a lot easier. With the mixture of different colored food dyes and water the first drop of ferrofluid spreads out evenly to form a thin layer on the food dye-water mixture after this the second drop will stay together forming a black dot on the liquid. Once this dot is on the liquid it's time to grab a dremel or whatever powertool you are using.
Step 3: Stare Into the Vortex
Turn on your powertool and start to lower the spinning magnet slowly over the ferrofluid drop. Once close enough the ferrofluid will start to spin and form a vortex. Try moving horizontally the spinning magnet to get different patterns to emerge. The vortexes look like waterwhirls, tornados or spiral galaxies and they are really satisfying to look at.