Is This 12-layer PCB Coil The Next Step In Ferrofluid Displays?

[Applied Procrastination] is in the business of vertical ferrofluid displays, but struggles somewhat with the electromagnets available off the shelf and the proliferation of wiring that results. [Carl Bugeja] is in the business of making PCB coils, both with rigid and flex PCB substrates, so when the opportunity for a collaboration arose, [AP] jumped at the opportunity.

As [Simen from AP] mentions in the video after the break, they had considered using a large PCB with embedded coils for Fetch their ferrofluid display unit, but the possible magnetic field was just too weak, and attempting to crank up the amps, just overheats them. Some improvements were made, first sticking the coil PCB to a small disk of ferrous metal, which doubled up as a handy heatsink. Next, he tried adding a permanent magnet, which added a bit of bias field. Alone this was not enough to hold the ferrofluid in place, but with the coil powered, it was starting to look encouraging.

Much more progress was made when [Carl] sent over a new design of his, a 12-layer PCB coil. This obviously had a much larger field, but still not enough without the extra boost from permanent magnet.

[Simen] currently doesn’t think the PCB approach is quite there yet, and is looking for help to source PCB-mounted electromagnets of the wired variety. We would imaging prototyping with such a large 12-layer PCB would be rather prohibitively expensive anyway.

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Fetch ferrofluid display

Ferrofluid Display Gets New, Better Driver Circuitry

In 2019 [Simen] and [Amud], two students from the University of Oslo, set out to design a unique open-source display. The result was Fetch, a display that uses electromagnets to suspend ferrofluid on 252 “pixels” across the screen. After some delays due to COVID, they have recently unveiled version 2.0 of the display on their project’s page.

While the duo managed to overcome the mechanical challenges associated with using ferrofluids fairly easily, they were quickly bottlenecked by their electronics. The use of electromagnets holding up a liquid presented a unique challenge; the magnets could not be switched off, even for a millisecond, or else the “pixel” would fall down to the bottom of the screen. That immediately ruled out any sort of multiplexing and meant everything would have to be driven in parallel. As if that wasn’t already difficult enough to work around, the effect of having multiple electromagnets activated next to each other would change how the ferrofluid flows. This meant that the strength of each electromagnet would have to be adjusted based on what is currently being displayed, rather than just being on or off.

The mess of connections were not helped with the layout of the old driver boards shown here. The new design puts the connections closer to each individual electromagnet.

All of this, paired with other overhead like generating pulse-width modulation for the inputs, was just too much for a single microcontroller to handle. So, the pair set out to design a better version of their electronics that would offload a lot of the hard work. At the same time, they decided a bit of mechanical optimization was in order; they redesigned the boards to be longer and thinner, allowing them to fit cleanly behind the row of electromagnets they controlled.

The new boards feature a PCA9685 IC, which allows for the control of up to 16 channels of 12-bit PWM over i2C, perfect for the size of the display. Since this IC can’t source enough current to drive the electromagnets, it was paired with a ULN2803 Darlington Transistor Array, capable of delivering up to 500mA to each electromagnet.

With prototypes in hand (and a few bodge wires here and there), [Simen] and [Amud] had the new driver boards running beautifully, displaying text in a mesmerizing way that no ordinary display could match. Watch the video after the break for a demonstration of the new controllers in action, as well as a deeper dive into the process of developing them.

Want to learn more? Check out our previous article about Fetch! Or if you’re looking for another cool way to use ferrofluids, how about making it dance in a custom speaker!

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Ferrofluid Dances In Custom Bluetooth Speaker

Ferrofluids, as the name implies, are liquids that respond to magnetic fields. They were originally developed for use by NASA as rocket fuel but are available to the general public now for anyone who wants to enjoy their unique properties. For [Dakd Jung], that meant building a special chamber into a Bluetooth speaker that causes the ferrofluid inside to dance along with the rhythm of the music.

This project isn’t quite as simple as pushing the ferrofluid container against a speaker, though. A special electromagnetic device similar to a speaker was used specifically to manipulate the fluid, using a MSGEQ7 equalizer to provide the device with only a specific range of frequencies best tailored for the fluid’s movement. The project includes two speakers for playing the actual music that point upward, and everything is housed inside of a 3D-printed case. There were some additional hurdles to overcome as well, like learning that the glass needed a special treatment to keep the ferrofluid from sticking to it.

All in all it’s a unique project that not only brings sound to a room but a pleasing physical visualization as well. Being able to listen to music or podcasts on a portable speaker, rather than the tinny internal speakers of a phone or laptop, is the sort of thing you think you can live without until you get used to having higher quality sound easily and in every place you go. And, if there’s a way to improve on that small but crucial foundation with something like a dancing ferrofluid that moves with the music the speaker is playing, then we’re going to embrace that as well.

Tracking Wasted Time With A Ferrofluid Clock

We know this project is supposed to be about developing a fine-looking ferrofluid clock, and not about the value of procrastination. But after watching the video below, see if you don’t think that procrastination has taken these two students further than expected.

We first ran into [Simen] and [Amund] several months ago when they launched their ferrofluid project in a fit of “There’s got to be more to life than studying.” It seemed then that building a good-looking, functional ferrofluid display would be a temporary distraction, but the problems posed proved to be far deeper and thornier than either of the electrical engineering students expected. The idea is simple: contain a magnetic fluid between two transparent panels and create pixels using an array of electromagnets to move dots of the fluid around. The implementation, however, was another matter, with the ferrofluid itself proved to be the biggest obstacle. All the formulas they tried seemed to coagulate or degrade over time and tended to stain the glass. While the degradation was never fully sorted, they managed to work around the staining by careful cleaning of the glass and using a saturated brine solution to fill the container.

Backed by 252 electromagnets and drivers on ten custom PCBs, the video below shows the (mostly) finished panel in action as a clock. We’re impressed by the smoothness of the movements of each pixel, even if there’s a bit of drooping at the bottom thanks to gravity. As for the future of the project, that’s unclear since [Simen] is headed off for a NASA internship. We’re not sure if that was despite or because of this procrastination-driven project, but we congratulate him either way and look forward to hearing more from both of them in the future.

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Ferrofluid Display Fuels The Fun, And The Procrastination

When deadlines loom and your future is on the line, do what top college students through the ages have always done: procrastinate! [Simen] and [Amund] did that in grand style by starting a YouTube channel, delightfully and aptly named “Applied Procrastination”, wherein they plan to avoid their responsibilities as long as possible in favor of making a large-scale ferrofluidic display panel. (Video, embedded below.)

We suppose we should encourage them to hit the books, but honestly they look like they’re having much more fun and learning more than they would in class. The idea isn’t new; we’ve seen ferrofluid clocks before, after all. [Amund] and [Simen] have grander plans for their display, but they’re wisely starting small with basic experiments. They had an early great idea to use a double-pane window as a tank for their display, but coatings on the inside of the glass and the aluminum frame conspired to cloud the display. They also did some tests to make sure they can control 252 electromagnets safely. They did manage to get a small test display working, but really the bulk of the video is just them playing with magnets and ferrofluid. And again, we’re OK with that.

It looks like this is going to be an interesting project, with hopefully regular updates to the channel now that summer break is upon us. Unless they find something else to do, of course.

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Failing At Making Ferrofluid

[NileRed] admits that while ferrofluid has practical uses, he simply wanted to play with it and didn’t want to pay the high prices he found in Canada. A lot of the instructions he found were not for making a true ferrofluid. He set out to create the real thing, but he wasn’t entirely successful. You can see the results — which aren’t bad at all — in the video below.

We’ve always said you learn more from failure than success. The process of creating ferrofluid involves two key steps: creating coated nanoparticles of magnetite and removing particles that are too large or improperly coated. After the first not entirely satisfactory attempt, [NileRed] tried to purify the material using solvents and magnets to create better-quality particles. Even the “bad” material, though, looked fun to play with along with a powerful magnet.

You’ll see that the material is clearly magnetic, it just doesn’t spike like normal ferrofluid. [NileRed] had commercial ferrofluid for testing and found that if he diluted it enough, it behaved like his homemade fluid. So while not conclusive, it seems like he diluted the batch too much.

We hope to see a better batch from him soon. The base material he used for the first patch was homemade — he covers that in a different video. However, for the second batch, he is going to start with commercial ferric chloride — what we know as PCB etchant.

Even though the experiment was not entirely successful, we enjoyed seeing the process and watching the performance of both the homemade batch and the commercial ferrofluid. He’s getting a lot of advice and speculation in the video comments, and it is very possible a Hackaday reader might be able to help, too.

We’ve seen other reports of unsuccessful ferrofluid production. If you need a practical reason to make or buy some, how about a clock?

Fail Of The Week: Ferrofluid

It’s more of a half-fail than a full fail, but [Basti] is accustomed to getting things right (eventually) so it sticks in his craw that he wasn’t able to fully realize his ferrofluid dreams (German, translated here). Anyway, fail or demi-fail, the project is certainly a lesson in the reality of ferrofluid.


We’ve all seen amazing things done with ferrofluid and magnets. How hard can it be to make an interactive ferrofluid wedding present for his sister? Where ferrofluid spikes climb up a beautifully cut steel heart in a jar? (Answer: very hard.)

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