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from the I-see-what-you-did-there-but-my-windows-fog-at-night dept.
An article published this month describes A new transparent metasurface that uses sunlight to counteract fogging of surfaces.
Fogging glass affects a variety of things such as glasses, cars, spacesuits and the mirror in the bathroom. Fogging can be inconvenient, dangerous or even deadly depending on the circumstances.
That's why cars and space suits have their own air-conditioning systems to remove or prevent fogging.
But air-conditioning is expensive, bulky, and environmentally unfriendly. So engineers and materials scientists are keen to find a way to prevent fogging more effectively.
To that end, researchers from Eidgenössische Technische Hochschule University in Zürich (ETH), engineered the new material layering gold nanoparticles between Titanium Dioxide on top of a glass substrate. The nanoparticles absorb sunlight raising the glass' surface temperature up to 10 °C. This causes water to either not condense or to evaporate much more quickly from the surface.
The surface is robust and relatively easy to make. When compared with conventional superhydrophilic and superhydrophobic antifogging surfaces:
The researchers say their new metasurface significantly reduces the rate of condensation and increases the rate of evaporation compared with other materials.
The researchers mention performance gains for various applications such as "windows, windshields, electronic displays, cameras, mirrors, and eyewear."
(Score: 0) by Anonymous Coward on Monday April 15 2019, @01:06PM (3 children)
My how soon history is forgotten.
Cars, up until until the late 60's to early 70's timeframe, commonly did not have air conditioning. Yes, the first car A/C was in 1933 (https://en.wikipedia.org/wiki/Automobile_air_conditioning) but A/C in a car was a luxury item that few could afford up until the later part of the 60's.
Cars do have defogging/defrosting vents, which blow air across the windshield, for the purpose of defogging and/or defrosting the windshield. But the A/C unit is present first for passenger comfort purposes, its use for defogging happens to be a happy secondary effect, not its primary reason for being in the car.
(Score: 2) by Immerman on Monday April 15 2019, @01:20PM (2 children)
Is air conditioning involved at all? I could have sworn the defogging vents blew warm or ambient air across the glass - cooling it down would seem like it would aggravate the problem.
Certainly the anti-fogging vents worked just fine in cars where the A/C has stopped working. In fact I could swear that fogging is primarily an issue when it's cold out - but maybe that's just the climate I'm in.
(Score: 1, Insightful) by Anonymous Coward on Monday April 15 2019, @01:32PM (1 child)
In humid climates (Washington DC area during summer) it can work wonders. In humid climates, esp. on cool, drizzly days, the windows can fog up even though the ambient temp is 70 or 80 degrees overall.
Having A/C works wonders in these situations because by engaging the refrigeration unit (the part that cools the air) one also gets a huge dehumidification effect. With the result that instead of blowing air at 100% humidity (saturated, so can't dry off any fog, and ignoring at the moment any drying effect from turning on the heat at the same time) one is blowing air at only 50% humidity (not saturated, so it can dry the fog off the windows). The fog disappears because of the reduction in humidity level of the vent air moving across the glass, rather than because of the temperature difference in the air.
Yes, heating the air also has a humidity reducing effect (because warmer air can hold more water vapor, so 80 degree air at 100% becomes 120 degree air at 95% humidity). But the effect is less pronounced because the A/C cooling drys the air out more than the drying effect of warming it from 80 to 130 or so. Also, in these same climates, when the air temp is 85-90, and the humidity is 100%, one does not want to engage the heat part of the defrost cycle, because one is already sweltering under 80 degrees and 100% humidity, and the additional heat from the defrost cycle simply results in extreme levels of discomfort.
(Score: 1, Informative) by Anonymous Coward on Monday April 15 2019, @02:32PM
In addition to that, in my old Datsun from the mid-seventies you could run both at once. It was set-up so that air went through the air conditioner first, then through the heater, then into the cabin through whatever vents you selected. You could run either AC or heater or both or neither.
Hot dry air would de-fog the windows in seconds.