[jellis1221]

Hello! I'm new to the forums and saw quite a few ferrofluid topics, but none could quite answer my question. (Hopefully this is posted in the right place.)

I'm working on an interactive electromagnetism project that will ideally allow users to "write" with ferrofluid. The goal is to be able to control ribbon-like ferrofluid strips. This video is my main inspiration.

So my question is: how does this work? Specifically, what possible solvent is the fluid in the above video suspended in to achieve that effect?

As a disclaimer, my background is in art - with pretty much no chemistry training - but I'll do my best to explain things on my end.

Video observations:

• The video shows that the reaction is happening in shallow liquid.
• The ferrofluid is likely denser than the solution its submerged in, given how is rests at the bottom when released from the magnet.
• Could some type of surfactant in the solution be allowing the ferrofluid to rise straight up?
• The tan surface in the video may be hydrophobic (or hydrophilic?). I purchased a teflon sheet that seems to be very similar in color and ferrofluid stain resistance as the surface in the video.
• Though I'm not sure how relevant the surface is to the reaction, as someone else managed to achieve a similar reaction in this video, using a dish.

Here's where I am so far with solvent testing. Note: the tests were performed in a plastic petri dish, and after dropping in 3-4 ferrofluid drops the mix was magnetized from the bottom.

• Isopropyl alcohol | Ferrofluid sank and separated into easily-movable spikes. Small, separate clumps. Solution seemed to crystallize the ferrofluid somewhat.
• Olive oil | Some parts floated, some parts sank. Did not mix. Spikes were generated as predicted.
• Acetone | The ferrofluid went crazy. Tiny droplets continuously moved about the surface several minutes after being added. Compared to normal spike generation, the spikes were fine and hair-like when the magnet was close, and large and claw-like when the magnet was at a distance. Could move with ease but there was some staining. Extremely hard to clean the faint stains, and moving the ferrofluid actually scratched the petri dish.
• Mineral oil | The ferrofluid mostly dissolved upon hitting the solution. No spikes created at all, just magnetic blob. Mixing increased as the ferrofluid moved around.
• Deionized water | Solution dissolved but stayed at the surface. The droplets that made it to the bottom (even when magnetized) were few and far between.
• 75% alcohol, 25% deonized water | Solution sank to the bottom. Remained very movable and the ferrofluid mostly stuck to itself. Probably the closest to what you get with Ferrofluid in a Bottle.
• Hydrogen peroxide | Completely dissolved at the surface. Also seemed to lose its magnetic capabilities.
• Witch hazel | Ferrofluid collected as a soft, concentrated blob when dropped in. Remained floating at the surface until magnetized (then stayed at the bottom). Spikes were soft and clear.
• Bleach | Ferrofluid visually exploded when hitting the surface. Also easily sank when magnetized, creating very small and pointy spikes. Though most of it stayed at the top. ...Honestly it looked like the oil of the ferrofluid began separating from its magnetic filings.
• Butane | Sank to the bottom and seemed to create a stable emulsion - that quickly de-emulsified when magnetized. Spikeless blob similar to the mineral oil mix, but moved easier.
• Given the above evidence, my ferrofluid is most likely non-polar in nature. (If this at all helps)

Any suggestions will be helpful!