Self-Cleaning Glass

Chris writes "Consumers across Europe can now purchase self-cleaning glass that promises to keep windows free from dirt. The key to Activ glass is an ultra-thin coating only 40nm thick applied to the glass surface during the manufacturing process. The coating, which is based on titanium dioxide, works by combining the two beneficial effects. First, the ultraviolet wavelengths in sunlight react with a photocatalyst to break down organic debris on the glass. The second feature is that the coating is hydrophilic, meaning that when rain hits the glass, it doesn't form droplets. Rain water flows down the glass in a sheet and washes the dirt away."

Comments

Re:Does this mean...

[srmalloy]

The glass could kill, or at least damage me, if I hold on to it for too long?

Unfortunately for us all, if you're holding on to the glass, you're blocking the sunlight necessary for the reaction to work -- and while it may work well for the typical dust and grime particle, I'm sure you'll admit that you're _considerably_ thicker than a layer of dust.

HydroPHOBIC methinks.

[Stavr0]

The second feature is that the coating is hydrophilic, meaning that when rain hits the glass, it doesn't form droplets.

That would be a hydrophobic coating. Hydrophilic attracts moisture.

Re:HydroPHOBIC methinks.

[zeus_tfc]

That would be a hydrophobic coating. Hydrophilic attracts moisture.

You're on the right track, but reaching the wrong conclusion. A hydrophobic material would cause water to bead up on the surface, as the adhesiveness of the material would be much less than the cohesiveness of the water. This is a hydrophilic material, at least in a sense, because the water adheres to the surface so well that it counters the cohesiveness of the water. I say in a sense, because I think a hydrophilic material usually absorbs water.

Of course, I could be totally off.

Nope, hydrophilic it is

[David Ziegler]

No, I'm pretty sure that it is hydrophilic. Hydrophobic means it repels water, which would cause the water to form droplets, in order to reduce the surface area. Since it's hydrophilic, the water is attracted to the coating, which makes the water sheet.

This has been available in the US for years...

[bad-badtz-maru]

PPG is one of the largest manufacturers of residential windows and they have produced windows using the self-cleaning coating for several years now.

http://www.ppg.com/gls_sunclean/

maru

Its quite widespread already

[sh0rtie]

According to Google there are over 1500 references to self cleaning glass, quite a few manufacters are already selling it, Pilkinton (uk glass company) and Sunclean seem to be the market leaders though Pilkington seem to claim "the worlds first". The BBC reported this technology in 2001, in 2002 Saint-Gobain Glass won a Siemens Award for innovation for their version

http://www.ppgsunclean.com/
http://www.activglass.com/
http://www.afgglass.com
http://www.saint-gobain-glass.com

Re:Bad Idea 4 solar cells blocks UV

[dmadole]

Solar cells unfortunately need the UV light to fuction properly

That's not true. The spectra of radiation that can be converted to energy by a solar cell is directly related to the bandgap energy of the material the cell is made from, and there is an optimum (for efficiency) bandgap that corresponds to the visible spectrum of light. Most solar cells do not convert significant energy in the UV area of the spectrum

That's part of the reason that solar cells are quoted as being only 10-15% efficient. That's of the total solar spectrum. Most are better than 50% efficient within the relatively narrow part of the spectrum that they are tuned for.

For a little more information, see the ever popular How Stuff Works.