# Ferrofluid Display Cell construction- hydrophilic surface application help

1. Jun 26, 2011

### taylaron

Greetings everyone,
I'm constructing a ferrofluid display cell using FerroTech EFH1 ferrofluid inside of a round bottom pyrex beaker. The ferrofluid is oil based, so it is not hydrophilic. The liquid that the ferrofluid will be suspended in is Magnesium Citrate (a household laxative... and no, i did not have this on hand!)

I've attached photos of my round bottom beaker filled with Magnesium Citrate (clear fluid) with about 15ml of black ferrofluid. Unforunately the ferrofluid has stuck to the surface of the glass. My suspicion is the ~10 nm size iron oxide particles are clinging to the imperfections in the glass. As you can see in the picture, this clinging action is unacceptable.

The best solution i've come up with involves finding and purchasing some kind of surface coating that I can apply to the inside of my beaker. The coating would need to be hydrophilic (not hydrophobic since the ferrofluid is oil based and it will completely coat the surface brown).

I need some help or advise on where I can find a hydrophilic surface coating that doesn't require baking my jar at some absurd temperature like 400 degrees Celsius. I've done some research and the compounds i've found that are used commercially utilize either titanium dioxide or silicon dioxide

info:
1. titanium dioxide: http://www.gotowti.com/Hydrophilic-Glass.htm [Broken]
2. Silicone dioxide: http://www.toolbase.org/Technology-Inventory/Windows/high-performance-glass product name: LoE2

Superhydrophilicty: http://en.wikipedia.org/wiki/Super_hydrophilicity

The best, or closest commercial product that might work is a window defogger. The last link says they're used in defogging windows. i'm going to try that out.

Can anybody offer a better solution?

Regards,
-Tay

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2. Jun 26, 2011

### SpectraCat

I am not that familiar with ferrofluids, but I think the problem might be one of incompatible materials. The few ferrofluids I seen or worked with could be placed in glass containers without showing any sticking to the walls.

If you put the fluid in the glass *without* the magnesium citrate solution, do you get the same coating issues?

Have you worked with this particular ferrofluid in aqueous magnesium citrate solutions before? The tech sheet says that the EFH1 is suspended in light hydrocarbons. Citrate can act as a surfactant, so what might be happening is that you are emulsifying your ferrofluid ... emulsions can definitely have undesirable properties when it comes to sticking to containers (think soap scum).

Why do you want to put your oil-based ferrofluid into an aqueous solution in the first place? (There may be a perfectly good reason to do that .. I just don't have much experience with these systems, so I am curious).

3. Jun 27, 2011

### taylaron

You make a good point SpectraCat.
When I first started this project my greatest concern would be finding a suitable fluid to emmerce the ferrofluid in. What I proceeded to do was go around various stores in town purchasing different kinds of fluids from pharmsutical departments. I tried kerosene, ammonia, oleic acid, water, rubbing alcohol, nail polish remover and magnesium citrate. While the kerosene, ammonia and alcohol dissolved my ferrofluid, I believe it was the water, nail polish remover, and magnesium citrate that showed promise. The water I used was Reverse Osmosis filtered water. The reason I didn't use water was because the spike formations when a magnet was applied were not as impressive as with the magnesium citrate. That, I did not photograph.

My primary disappointment with the water was the bubbles that formed when I shook the container. While in a perfect laboratory environment with ideal equipment I would apply a vacuum to the display cell before capping it; I do not have a vacuum pump. I admit the container shouldn't be shook in the first place...

The ferrofluid display cells that are sold for about $20 online can be found here: http://www.teachersource.com/ElectricityAndMagnetism/Ferrofluid/FerrofluidPreformDisplayCell.aspx or my favorite here: http://www.czferro.com/ They appear to have a new model out- the Klock, which is very similar to my desired product... I may just purchase one.$30.

I've read the MSDS on the CZ Ferro display cell and It says it's a alcohol-water combination. However, I suspect the ferrofluid used in the display is not EFH1 by Ferrotech. I suspect they use Ferrotech's R&D ferrofluid which is rumored to be used in display cells. Except it's about 4x as expensive as EFH1 with a minimum $100 order. By the way, the window defogger did indeed help, but it did not completely solve my sticking problem. Last edited: Jun 27, 2011 4. Jun 27, 2011 ### SpectraCat Well you didn't really answer my question about whether or not the pure ferrofluid sticks to the glass or not. Assuming it doesn't, and from what you wrote above, I would say that it may well be the surfactant nature of the mag citrate that is causing your issues. The reason the spikes were not as pronounced in water is probably because the interfacial tension between the oil-based ferrofluid phase and the water is too high. Adding a surfactant reduces the interfacial tension, allowing the spikes to become more pronounced, however it will also have the tendency to emulsify your ferrofluid if you agitate it too much. One way to try to control this would be to modify the concentration of the mag citrate. Do you have any idea what the concentration of your mag citrate solution is? I am not sure that the window defogger is really going to help. It is probably helpful for keeping the emulsion from sticking to the flask, but I think once you start emulsifying the ferrofluid, your display cell will be toast anyway. 5. Jun 27, 2011 ### chemisttree I'd apply a 'perfluoro functionalized reactive silane' (Great GOOGLE termage!). Heat the beaker with some strong KOH, rinse well with water and dry. Apply the silane (in freon) and let it drip dry. Heat briefly to 60C and you have a perfluoro coated beaker. Neither water nor oil will stick to it... only perfluro compounds and freons. 6. Jun 27, 2011 ### taylaron Correct, the ferrofluid adheres to the surface of a clean beaker without any carrier liquid. I do not know the concentration of the mag citrate unfortunately... It's a cheap Walgreen's product. So i've learned... I'm also thinking that the glass used in the commercial display cells is of higher quality than my pyrex beaker. The containers i'm looking at on those links look extremely well polished. Does anyone have any ideas on how I can seal my container without any air bubbles? A decent vacuum pump is going to cost me at least$150 on eBay it looks like. Purchase doesn't look worth it.

7. Jun 27, 2011

### taylaron

Interesting Chemistree, but doesn't freon destroy the ozone layer??

-Tay

8. Jun 27, 2011

### taylaron

9. Jun 27, 2011

### chemisttree

Last edited by a moderator: Apr 26, 2017
10. Sep 9, 2011

### caseyrocks

Hey, great work so far. I am working on a very similar project and strangely enough I too have tried magnesium citrate as a secondary solution. With the EFH1 ferrofluid (FF) I had different results - the FF immediately started to breakdown and stick to the glass while in the magnesium citrate. The problem is not with the glass. There should be no issues with FF sticking to any half decent glass container as long as the suspension fluid is of a good quality. That's the trick, finding a good carrier solution. I am still working on some mixtures however I am very close to finding something that works well without disturbing the composition of the FF. A mixture of alcohol and water is a good start. I will update this post as I progress. Let me know how things are going for you :)

11. Sep 9, 2011

### taylaron

Thanks caseyrocks,
I've experienced mostly failure in my attempts, which sound similar to your efforts. In the end i've largely given up. I found the glass bottle I've been using is of a low grade quality (on top of being used) and the ferrofluid nanoparticles tend to adhere to the abrasions in the surface. Seeing how they stick in the same locations every time. After toroughly cleaning the glass, trying different hydrophobic coatings (like rainX) and researching different hydrophillic solutions online I found the displays constructed commercially are of high quality, highly polished glass on the inside which are baked in an oven at ~2000deg F and are coated with a some sort of titanium dioxide (or something) which acts as an extremely durable and effective hydrophobic (or hydrophillic, i cant remember) surface for the ferrofluid to repel.
I also found that there is a reason the commercial display units eg; "nano drop" are so small. you cannot shake the containers without causing your ferrofluid and suspension liquid to become an emulsion. Once it's emulsified, you cannot easily fix it. The larger the container and the more ferrofluid there is, the easier it is to emulsify your mixture.
I also found that the round bottom flask I was using acted as a refracting lens and adversely affected my ability to observe the ferrofluid, other than looking up at the bottom (which is pointless...). the "nano drop" company's use of perfume bottle which are essentially highly polished ovals work great for observation as there is little lensing.
for \$30 you can buy one you can hold in your fist. http://shop.czferro.com/Ferrofluid-Klock-Klock-Ferrofluid.htm [Broken]

Also, with the magnesium citrate, you need to apply a hard vacuum to evacuate all the air out of the solution otherwise bubbles form in your display which are detrimental to the ferrofluid and your container surface.
Also, with the suspension liquid, try to find a liquid with as close a density as possible to the ferrofluid. Unfortunately most of the fluids that are appropriate for the job are hazardous.
Info I collected:

FerroTec EFH1 ferrofluid has density of 1.21gm/ml
Liquids with same density:
Benzoyl chloride (hazmat)
Formic acid (hazmat)
Close density:
Dimethyl sulfoxide (1.100 gm/ml) HAZMAT . Data from http://www.simetric.co.uk/si_liquids.htm
Benzil (1.08 g/ml) )(hazmat)
Beer: around 1010 at 20 deg C

Last edited by a moderator: May 5, 2017
12. Sep 9, 2011

### taylaron

In the end, I spent more money trying to figure out how to do it and construct one than does the actual product! evidently this is usually the case in home-projects

13. Sep 25, 2011

### caseyrocks

I have made some progress in my two part display. I am using untreated food grade glass bottles soaked overnight in the mixture before adding the FF.

The secondary fluid is 50% Methyl Hydrate (99% pure) and 50% distilled H2O

There is some sticking to the glass only where the FF rests for a long period of time however I am working on this. I suspect that some of the FF breaks down and sticks so I am cleaning the area of the bad sticky FF while holding the good FF away with a magnet. It seems to be working however I am sure there is an easier way. I am going to try transferring to another bottle and letting it rest.

http://www.imagehosting.com/photo/dsc00833-1/
http://www.imagehosting.com/photo/dsc00836-1/

http://www.imagehosting.com/photo/dsc00833-1/
http://www.imagehosting.com/photo/dsc00836-1/

14. Sep 25, 2011

### msbe

Are you guys purchasing ferrofluid or synthesizing it yourselves?

15. Jul 22, 2012

### clevertrevor

@caseyrocks,

Have you made any progress on your suspension fluid? I am very interested in ferrofluid and just ordered 1L of FerroTec EFH1:

http://www.ferrotec.com/index.php?id=audioFluid&vfp_id=125

from:

http://www.teachersource.com/product/bulk-ferrofluid-100ml-1000ml/

I will start with your recommendation for methyl hydrate and water. I also plan to try commercial anti-fog coatings on the glass such as FogTech anti-fog solution. Has anyone applied titanium oxide as a DIY? If so, how? Any further info is appreciated. Thanks!

16. Jul 26, 2012

### clevertrevor

I just tried an over the counter anti-fogger called FogTec and it seems to work pretty well. I have a few test tubes that I applied the defogger to, let them dry, filled slowly with plain ol' tap water, and added some ferrofluid. Compared to the test tubes without the fogger, there is a big difference. The glass remains clean, stain free, and the ferrofluid does not stick to it. Also, the test tubes are brand new and free of any scratches, which helps alot too.

Next step, DIY TiO2 glass coating:

http://www.solideas.com/solrcell/coatglas.html