[D3MON]

Liquid crystals need current and complex polarization to work, and I really want to keep the window simple in design.    I guess I never really thought about how hard the liquid choice would be, but this is actually turning into quite a challenge.  So to once again add onto the long list of characteristics this liquid must have, no it can not freeze in the winter.

For those who feel like reading and want to hear my whole story:
I guess Ill go ahead and divulge my entire pipe dream idea for an easily marketable "smart" window.  Im currently working as a residential appraiser while still attending college, and I noticed that in many homes it would be really nice to have a window that you could change the opacity to, without hampering some of the great views.  In theory it would be an adjustable window tint that could block light like a blind, but still be easy to see through.  I started thinking that LCD technology applied to an entire window would be perfect, as Ive seen the technology used perfectly in welders masks.  In my search for information on how to do this I found that one company already makes glass containing liquid crystals and has dubbed the windows "privacy" glass because of its ability to go from completly clear to a frosty white non see through look.   Well, this wasnt the use I was looking for in my application, so I continued looking.  This is when I came accross the electrochromic "smart" windows, and found that this nearly finished technology worked exactly how I invisioned and even more by actually using a tinting film that can be manipulated by electricity.  However, its now almost 6 months after the companys have rolled the electrochromic windows out to consumers and only a handful of companys can actually afford to use it.  The technology is currently too expensive and complicated to implement, and therefore I see a need for simplification.  I believe that a simple dark liquid solution sandwiched between an already existing two pane window structure may be the realistic solution that the mass market needs.  This would only require a simple handcrank, at the cheapest end of the structure, in order to work.  Now I realize that acutally marketing an idea and getting it out there is usually nothing but a pipe dream, but I figure I might at least see if this one is possible.  So what do you guys think?

[mike]

This is a tricky one. Apart from just getting some of the liquids I first mentioned and trying them between two panes of glass, I am not sure wht you can do. How are you going to qualitatively determine how much light is actually blocked out?

Another idea is something along the lines of using an equilibrium reaction such as nitrogen dioxide and dinotrogen tetroxide, the former is dark in colour and the latter is colorless. The equilibrium (essentially the amount of the dark gas or light gas) can be shifted by altering the pressure or the temperature (or both) so in essence this would do exactly what you want. The problem here is that the gas is quite noxious and would not at all be suitable for buildings due to its toxicity. This is just an idea to get people thinking along the lines of equilibrium reactions...

[Donaldson Tan]

Another means is by selective polarisation of glass.

[mike]

Another means is by selective polarisation of glass.

No kidding

Hey geo, what about my thoughts on some sort of equilibrium chnaged by temp or pressure? What are your thoughts?

[Donaldson Tan]

.. be able to control sun throughput by changing the distance between the panes.  Therefore, the liquid must be thin enough to move easily between the glass, not have any particles that can get stuck when the panes are at 0 distance in order to give completly clear visibility through the glass...

If he intends to adjust sunshine penetration by adjusting the space between the glass panes, he must have a pump to pump in additional liquid when the space is expanded, and a suction to remove some liquid when the space is contracted

If chemical equilibria is used, it is not necessary to slide the glass panels at all. The opacity of the chemical system within the glass panel can be tuned to the sunlight. One such known system is NO₂ / N₂O₄ (suggested by Mike), and we know toxicity is a safety issue in using this substance. Increased in sunlight leads to temperature increment inside the glass panel. However, given the low thermal conductivity of glass, time delay becomes an operating issue. This time delay problem must be overcome too.

[D3MON]

I assume if the window had a connected flexible vaccum pouch for the liquid to be displaced to, you would not need any sort of pump.  The simple act of creating more area between the panes would draw  the liquid in to the window, and by moving the window together the liquid would evacuate to the pouch.

Also, I would not want any sort of reaction to light, because I want to be able to let the user change the darkness according to their preference.  The system should work like blinds do, and not just change on their own without the users control.

So, has anyone come up with a generally accepted solution?  I would think some kind of clear oil that could mix with dyes would be best, but what?

[Borek]

Go for ethanol. Oils have too high viscosity and pumping them will require substantially more energy.

No idea about the dye though, that's not my specialty.

[D3MON]

Woohoo.  I finally put together a proof of concept, and it actually worked quite well.  All I did was take 2 panes of plexiglass, seperate them by about 2mm, and put plastic all around the edges, and then taped the plastic to the sides to make a seal.  I then filled the gap in between the panes with a clothes dye and water mixture, and I could not believe how dark the mixture was!  With just a little dye in the mixture I could hardly see through the glass at all!  One of the things I was really worried about was the darkness of the mixture, but now I know that that is the easy part.  Only problems I encountered was the plexiglass being to flexible (so I really do need to use glass, which isnt a problem), also the color was blackish blue but caused some light to come through red (not a huge problem),  and an actual problem of getting the water to completly evacuate from between the glass by just pushing them together (Oh, and one more problem of part of my hand being black now...)  Still, this was a super simple test and it worked out really quite well.

So, anyone know a good way to get this patented?

[mike]

So, anyone know a good way to get this patented?

Don't forget to add me to the patent.

Go for ethanol.

Can you imagine a whole office buidling with windows full of ethanol catching on fire?

[D3MON]

LOL, good point.  At least youd know the building would be a complete write off in a fire, instead of the insurance company wanting to rebuild     Hehe, might be a good selling point.

[Borek]

Go for ethanol.

Can you imagine a whole office buidling with windows full of ethanol catching on fire?

Yeah. Looks bright

[limpet chicken]

Iodine in carbon tet will work, although it will focus sun rays, and burn things, given half a chance.

[Borek]

it will focus sun rays

Please elaborate.

[mike]

Iodine in carbon tet will work, although it will focus sun rays, and burn things, given half a chance.

uuum, I was under the impression that carbon tetrachloride had been widely abandoned for almost all commercial uses due to its toxicity