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This Idea should be seen as an extension of the "Ultraviolet Bathroom Sanitizer" and "UV Kitchen Sterilizer" Ideas. Because those are about germs while this one is about dirt.
There is a simple inorganic compound, titatanium dioxide (the whitest substance known, in powder form) that interacts with
dirt and ultraviolet light in a unique way. Some places are already using this property in special coatings, to reduce cleaning costs (activated by the UV in sunlight). Some windows are also for sale that use this phenomenon (the outsides are coated with titanium dioxide, again activated by sunlight).
So far I have not seen a suggestion to use those coatings indoors, combined with appropriately used "black lights". Some researchers are trying to modify the phenomenon to work with ordinary light, but if we have to wait for them to succeed, we might still be cleaning houses the hard way next century.
The easy way is this: With the right kind of coating of titanium dioxide on a wall, any particle of dirt can stick to the wall in the usual way. But when an ultraviolet photon comes along and gets absorbed by the TiO2, it reacts with the dirt particle in a way that encourages oxygen in the air to "burn" the portion of the dirt particle that attaches it to the wall. So the dirt falls off and the TiO2 just sits there nice and clean. If the place where the particle lands is also coated with TiO2, then gradually the whole particle will be oxided, burned up slowly.
So imagine the whole inside of your house coated with that special layer of titanium dioxide (it can exist in transparent form and, since it works on windows, we know it's still useful here), not greatly affecting the chosen color scheme for the house.
When the last person leaves a room (or if the house is wired with sensors and intelligence, and determines that a room is empty), Black Lights can be turned on in that room. These emit ultraviolet light, just like sunlight, and so can activate the TiO2 coatings, and start the automatic cleaning process. No more scrubbing in kitches and bathrooms! Even the fixtures in those rooms can be coated, to both kill germs and to clean. No more scrubbing crayons from walls!
The likeliest side-effect is unwanted "aging" of stuff in the house. Most plastics are susceptible to degradation under UV light, and lots of stuff is plastic these days. Oh, well, the obvious solution is to not leave those black lights on all the time, and certainly not when people are in a given room (UV can damage eyesight, if you are exposed to it long enough).
Ultraviolet Bathroom Sanitizer
As mentioned in the main text [Vernon, Jun 12 2006]
UV Kitchen Sterilizer
As mentioned in the main text. [Vernon, Jun 12 2006]
Popular Science Article
Describes the self-cleaning property of TiO2, and the effort to make it work with ordinary light. Does NOT mention using black lights. [Vernon, Jun 13 2006]
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||Why not high energy gamma radiation? This will sterilize more than just the surfaces, and if the thing can only run when the room is empty anyway...
||And with all those black lights those posters we collected in the early 80s would ROCK!
||Your walls are already coated with titanium dioxide. It is the base pigment in pretty much all modern house paint. (If your house has not been painted in the last twenty years, the base pigment will be white lead instead).
||[Galbinus_Caeli], yes, most paints these days use titanium dioxide. However, the particles are suspended in latex paint in a way that you cannot really say that a lot of the TiO2 particles are actually at the surface of the dried paint. Kind of like, on a sidewalk made of concrete, you know that there are rocks, gravel, in the concrete, but you hardly see any of them at the surface of the sidewalk.
||For the titanium dioxide to be effective, it must be AT the surface of anything that gets coated with it.
||[Vernon] Your ideas are sooooo cute when they are brief! (+)
||My Idea is the combining of the TiO2 thing with black lights, so that we don't have to wait for the ordinary-light version to be developed. I admit being inspired by the article, but since they didn't mention black lights, I felt I could post here without getting into trouble about it.