To recap, this was a proof of concept for an actuation method using electromagnets to manipulate a small balloon filled with a ferrofluid. After the first iteration of ferrofluid experiments, I refined the mixture and made a larger amount. The second iteration used mineral oil in place of canola oil with a slightly higher magnetite to oil ratio. To make the small casings, I used the finger from a latex glove. when filled this yielded a casing about an inch and half long with a diameter of about 3/4 of an inch. Unfortunately, this turned out not to be great configuration. I think there were two chief issues. The first and more minor was the latex glove was too stiff to deform easily from the relatively small forces exerted by the magnets and ferrofluid. The more significant issue was that the casing was too wide. The magnets only act on a thin layer on the outside of the casing, and so the majority of the ferrofluid does not magnetize and therefore does not deform at all.
So why not make the casing smaller?
The main issue there is practicality. With better equipment it would probably be relatively easy to fill a smaller casing with ferrofluid, but as it is the fluid is extremely thick and requires a large syringe otherwise it stops up. To get a thinner casing would therefore be difficult, the trade off would be a stronger magnet. However, even with permanent magnets which are several times stronger than any electromagnet I could realistically make, the casing was still too thick to react well to the magnets. So since making the casing smaller and thinner is impractical, and making the magnets stronger is probably even more impractical, I decided to move on to other projects.
Any future work?
The only next step that I think I could take on would be a much simpler proof of concept. Rather than try to make something that could be converted into an actual actuator, I had the thought that I could instead put a small amount of ferrofluid into some surgical tubing which would hopefully be thin enough to react to the strength of magnets I have. I could then measure the displacement within the tubing when magnetic force is applied.