Simple technique results in surprising repellency results

Dec 02, 2011 by Bob Yirka report

(PhysOrg.com) -- Anyone who has ever worn eyeglasses for any length of time can surely attest to the annoyance of constantly having to clean off the oil left behind by finger touching. Not only does it dirty the lens, but removal requires a solvent, rather than a simple tissue. Doris Vollmer can relate, and that’s just what got her thinking about the soot given off by her Christmas candles. As a polymer research scientist with the Max Planck Institute in Germany, she knew the soot was water resistant, but what she wanted to know was whether it was oil resistant as well. So, she and her colleagues held a glass slide over a candle and then tested it. In doing so, as she and her team describe in Science, they found that after some tweaking, the result was a truly remarkable repellency material.

After discovering that the soot that showed up on the glass slide not only coated the glass in black, making it impossible to see through, they also found that it wasn’t very stable either. Water dripped on it rolled right off, but carried some of the soot with it, which would mean constant reapplication if trying to use it as a repellant. To counter the instability, they coated they soot with silica using a chemical vapor process. Then, to make the black coating clear, the whole works was calcined (heated to bring about a thermal decomposition). The result was a clear omniphobicity (repels both oil and water) coating that could have many uses in commercial products.

It turns out the soot is naturally water resistant due to the way its carbon particles align themselves on a surface, much like a fractal type network, where there just isn’t enough space for or other liquids to pass through. The team found that the bonds were so strong that the material retained its repellency qualities even when blasted with sand or abused in other ways.

It’s not clear just yet if the coating will indeed one day be applied to , forever relieving wearers from the vagaries of fingerprints, but the results thus far look promising for treating various metals or to create non-stick surfaces for use in a variety of industrial applications.

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More information: Science DOI: 10.1126/science.1207115

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User comments : 11

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antialias_physorg
3.8 / 5 (4) Dec 02, 2011
I'd love to see this on eyeglasses (or more precisely: not see this on eyeglasses)
PinkElephant
5 / 5 (2) Dec 02, 2011
the bonds were so strong that the material retained its repellency qualities even when blasted with sand or abused in other ways
Could be good on car windshields...
stealthc
not rated yet Dec 02, 2011
silica using cvd is one way, but even easier to do at home is to buy a can of spray-on-glass. I wouldn't mind finding details on this process that makes the soot clear and more stable. any ideas?
Isaacsname
not rated yet Dec 02, 2011
silica using cvd is one way, but even easier to do at home is to buy a can of spray-on-glass. I wouldn't mind finding details on this process that makes the soot clear and more stable. any ideas?


Talk to the " wizard ". One of my secret sources for any glass cold-working supplies, he's also one of the world's foremost experts on cold-working and many other related areas in glass working.

http://www.hisglassworks.com/
PinkElephant
not rated yet Dec 02, 2011
I wouldn't mind finding details on this process that makes the soot clear and more stable.
Well, to quote the article:
to make the black coating clear, the whole works was calcined (heated to bring about a thermal decomposition)
So... a blowtorch? Or maybe a high-energy laser? Or just plain-old stick-it-in-a-furnace? Wonder how they got around the issue of the glass substrate melting and warping in the process...or did they...
Isaacsname
not rated yet Dec 02, 2011
Says 600C, probably just regular borosilicate glass, they used a 25nm coating of silica, maybe using nanospheres, sodium silicate or something similar.

http://www.bangsl...ospheres

http://en.wikiped...silicate

Just a layman's guess, I do have some experience with glassworking, but still probably completely off-course :P
I did have the same thoughts as you guys though, how can it be done at home (?). I wear glasses also and having stood over fuming oils and fire for 20 years as a chef, I know firsthand it's very hard on lenses, I'd love a coating like this, especially if I can do it at home.
Telekinetic
1 / 5 (2) Dec 02, 2011
Remember this stuff? It was supposed to spread like wildfire-
http://www.physor...039.html
Isaacsname
not rated yet Dec 02, 2011
edit
Chromodynamix
not rated yet Dec 03, 2011
Whatever you do, do not use acetone based nail varnish remover, ot any ketone on plastic lenses!
MNIce
not rated yet Dec 03, 2011
The coating needs to be applied on the inside of the lens - my greatest annoyance with safety glasses is sweat and skin oil on the lenses near the nasal bridge.
Isaacsname
not rated yet Dec 04, 2011
I get it now, this is fairly simple, but brilliant, I'm definitely going to play around with it.

It's identical to, or almost identical to, silica gel that's used for water retention, soaking up fluid spills, diaper fillings, etc.

It's a fluid-loving material that soaks up a hydrophobic substance, the process is finished by heat-driven silanization.

Given my rudimentary workshop, I doubt I could produce the same quality finish they did in the original work, but the concept is simple and straight-forward.

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