Slashdot Mirror
Nanotech Coating Prevents Fogging
MilSF1 writes "MIT scientists have applied for a patent on a coating process that reduces or eliminates fogging on glass surfaces (car windshields, eyeglasses, etc). The new coating was described today at the 230th national meeting of the American Chemical Society."
Ever wanted a shave in the shower but your hand-held mirror fogs up? Rather than buying this patented glass you can resort to a low-tech solution: Rub a little shaving foam over the glass and the wash the excess off so you have a thin, clear, greasy film on the glass.You'll find that the mirror no longer steams up.
The reason this works is because the greasy film causes much larger drops to coalesce on the mirror than you would normally get. These larger drops don't refract the light nearly and as a result are essentially transparent. This simple trick allows me to insure my sideburns are the same length even when under the most horrendous time presure.
See, who says that Physics can't be useful in everyday situations?
Simon
The people who make rain-x, which works rather well itself to deflect rain, also make fog-x, which I've tested on a steamy bathroom mirror, and it works perfectly.
According to TFA (not that I expect people to actually read the thing):
So far, the coating is more durable on glass than plastic surfaces, but Rubner and his associates are currently working on processes to optimize the effectiveness of the coating for all surfaces. More testing is needed, they say.
It was a joke! When you give me that look it was a joke.
Who do they think they're foolin'?
More light than comes from through the glass??
if it makes a smoother surface, it could allow more light through
...they simply spit in their masks to prevent fogging.
May be this will finally replace the old method of spit and rinse, because all those special glasses on the scuba masks had no effect until now. For those who don't know, if you want your scuba mask to be perfectly clean of fog, you have to spit inside it when it is dry, then rinse very fast with sea water (just to make the glass clear enough but probably without rinsing all the substances in the saliva from the glass) then put it on the face and dive immediately. For those who forgot doing this, even the best tempered glass became foggy in a few minutes in cold water.
Because most of the light that does not pass through the glass is not "absorbed" inside the the glass but instead reflected at the air/glass and glass/air boundary layers.
Coating glass with stuff to minimize the reflection is a really old thing. Ever wonder why the lenses of (good) binoculars seem have a bluish or reddish tint to them ? Because they're coated to increase light transmission.
Their claim is valid. Anytime light passes through an abrupt change in the index of refraction (e.g., from air to glass), a percentage of the light it reflected back. That's why you see a ghost image of yourself in even "transparent" pieces of glass. On ordinary glass, about 4% of the light is reflected (removed) by each air-to-glass or glass-to-air interface (8% for each pane).
Adding a anti-reflective coating that has an intermediate index of refraction can reduce this. Nonlinearities in the reflection process mean that two interfaces of lesser change reflect far less than one big change. Camera lens makers do this all the time because many lens have 6 to 20 pieces of glass and thus a dozen or more interfaces that each would to attenuate light and create multiple internal reflections between the lens elements.
It may not be much, but that antifog coating probably lets a couple extra percent of the light through.
Two wrongs don't make a right, but three lefts do.
It's not just glass that fogs up though. Despite the /. story suggesting that this coating is only for glass, TFA says that this coating can be applied to "virtually any surface", which is great news for motorcyclists with plastic visors that always fog up on cold/wet days. Normally when it is raining, I have three choices,
1. Closed visor, it fogs up within minutes - Can't see a thing.
2. Visor fully open (nothing to fog), subjected to a face full of fast moving water droplets - can't see a thing.
3. Visor open slightly, air can circulate, visor doesn't fog, but water droplets form on the inside of the visor, which severely reduce visibility.
Rain-X is quite destructve on the plastic visor ... and it is not made for anti-fogging. Says so right there on the bottle.
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is it that bad seein a hot chick again? if i see a hot chick walkin down the hall i dont say "repost"
Speaking as an MIT student working on this project, yes it lets more light through- a lot. Uncoated silica reflects about 8% of incident light, as was posted elsewhere. With our coating, this drops below one percent through most of the visible spectrum, and below .2% at a peak wavelength dependent on the number of coating layers (around 550nm for a 14-bilayer coating). It's a pretty nice improvement- you can place a half-coated slide against white paper and the untreated side looks dirty by comparison. I can try to dig up the spectrophotometer measurements I took a few weeks ago, if anyone cares that much.
/.ed. Party in lab today!
Also: Whoa, Rubner got
http://www.cyclegadgets.com/Products/product.asp?I tem=FC
These things are sweet. They don't fog, period, and if you get the UV reactive one, it darkens in sunlight so you don't need to carry two shields. It's not quite as dark a real reflective shield, but it's dark enough.
Chuck Yeager has a lot of anecdotes about his crew chief. The guy was a genius when it came to common sense, solving problems, and getting things done. A true hero behind the scenes, the best there was.
If scientists and normal people would read this stuff, I am sure they would rediscover all sorts of solutions to common problems.
L8,
AC
Firemen and HAZMAT workers have to open a 'de-fogging' vent on their SCBA's to dissipate fog from their facemasks, wasting air. This coating could add minutes to a workers time on scene.