Eco glass cleans itself with Sun

From: sid myers (gloopencrotum_at_hotmail.com)
Date: 06/13/04 

Date: 13 Jun 2004 07:12:42 -0700

my meager understanding of chemistry suggests that once a chemical
reaction occurs that to reverse it or alter it would require a lot of
energy and appropriate quantities of chemicals and yet this process
appears to be perpetual.

also, sounds a bit like bad news for window cleaners.

-------------------------------------------------------------
Source: http://news.bbc.co.uk/1/hi/technology/3770353.stm

Eco glass cleans itself with Sun

By Jo Twist
BBC News Online science and technology staff

A revolutionary kind of glass that needs little cleaning could mean
soap
and chamois are binned for good.

The Pilkington Activ glass has a special nano-scale - extremely thin -
coating of microcrystalline titanium oxide which reacts to daylight.

This reaction breaks down filth on the glass, with no need for
detergent.
When water hits it, a hydrophilic effect is created, so water and dirt
slides off.

It is one of four finalists for the eminent MacRobert engineering
award.

The prize is given out by the UK's Royal Academy of Engineering for
technological and engineering innovation.

'Nano' cleaning

"Pilkington Activ is based on titanium dioxide, which is used in
foodstuffs, toothpastes, and sun cream," explained Dr Kevin Sanderson,
one
of the team members who developed Activ at Pilkington's technical
research
centre.

"But usually it is a white powder which is not ideal for glass because
you
can't see though it.

"So we used it in a thin film form - 15 nanometres thick - so that it
appears as close to normal glass as it can."

Although not strictly nanotechnology, the special coating and the
chemical
reactions happen at the nano-scale (one thousand millionth of a
metre).

The titanium dioxide coating on the glass has two properties that make
it
special, said Dr Sanderson.

Click here to see how the glass works

It absorbs sunlight - ultraviolet radiation - which causes what is
called
a photocatalytic effect.

Through this process, the coating reacts with light which then breaks
down
organic dirt.

Secondly, the coating makes the surface of the glass hydrophilic. This
means that when water hits the surface of the coated glass the water
droplets attract each other forming a sheet, rather than individual
droplets.

"It destroys the organic dirt, and destroys it naturally, as well as
reduces the glue that other dirt can stick to on the surface," said Dr
Sanderson.

With the photocatalytic effect of the coating constantly working in
the
background, the glass dries cleanly, an effect he and his team like to
call the "invisible squeegee".

Natural breakdown

The environmentally-friendly innovation is a result of a long process
of
research and development, starting from the early 1990s, into "thin
film"
technologies.

"When we realised we could get these properties with it, that is when
it
really drove through," said Dr Sanderson.

"It took five to seven years to take that from lab samples to putting
it
on the coating production line."

Activ glass clearly has several benefits, argued Dr Sanderson.
Although he
promises it will not put window cleaners out of business, it will cut
down
on the need to clean windows so often, and it will reduce the need for
obnoxious detergents.

"Each time harsh chemicals are used, they are washed off into ground,
which produces contamination.

"What we say here is that you can just spray water on top."

There is an additional safety benefit too, Dr Sanderson said.

"Each year people are killed using ladders to clean windows. What we
are
saying is that that should be reduced because you can use a hose pipe
to
reach the first story."

£50,000 prize

Although it is slightly more expensive that conventional glass, adding
about 15 to 20% to the cost of installation, the technology is already
being used in sheltered housing windows where easy cleaning is
important.

But Dr Sanderson said it could potentially be used to break down
E-coli or
other bacterial infections on surfaces.

It could also be used to naturally decompose pollutants in the air,
like
formaldehyde, and ground level ozone.

The other finalists for the award include switchable 2D-3D displays,
an
eco-friendly fuel injection system, and software which connects
multiple
system computer platforms.

The winner of the £50,000 prize money, handed over by HRH the Duke of
Edinburgh, is announced on 10 June.

Relevant Pages

  • Re: polycarbonate with a weak prescription
    ... wearing) is that your lenses don't have an AR coating. ... > quality, and am considering going to cr39 or glass. ... > an issue for a prescription as weak as mine. ...
    (sci.med.vision)
  • Re: UNcoated mirror for lunar observing?
    ... The glass is formed and figured as it is, ... We want the coating to conform to the supporting structure. ... It is the coating which does the reflecting, ... standard telescope mirror is not one of those applications. ...
    (sci.astro.amateur)
  • MIT research could clear up foggy problem
    ... The transparent coating can be applied to eyeglasses, camera lenses, ... Glass containing titanium dioxide also shows promise for reduced fogging, but the method only works in the presence of ultraviolet light, researchers say. ... Coated glass appears clearer and allows more light to pass through than untreated glass while maintaining the same smooth texture, said Rubner, who collaborated on the work with Robert Cohen, the Raymond A. and Helen E. St Laurent Professor of Chemical Engineering. ... causing the surfaces to become translucent or foggy. ...
    (sci.physics)
  • Eco glass cleans itself with Sun
    ... Eco glass cleans itself with Sun ... coating of microcrystalline titanium oxide which reacts to daylight. ... special, said Dr Sanderson. ... "Each time harsh chemicals are used, they are washed off into ground, ...
    (sci.physics)
  • Re: Crazy Clean or other cleaner on the backside of a backglass?
    ... glass isn't lifting or peeling at all (and I'd like to keep it that ... Probably won't work too well given the tar film. ... Crazy Clean sprayed on a cotton rag and light rub. ... Please do NOT spray any chemicals on the backside of a painted glass. ...
    (rec.games.pinball)