While researching a new project (as us mad-scientists-types are prone to do), I found this amazing video. It’s basically a clear chemical that undergoes a reaction in the presence of UV light that makes it very quickly turn green. But, the key here is that the reaction is also quickly reversible – in about a half second after the light is removed, the liquid reverts back to the clear state.
This reminds me of a fictional Dr. Seuss invention, the “flash-dark” (from “The Cat’s Quizzer“), that’s like a flashlight except it shines a beam of darkness instead of a beam of light.
Practical uses? I can imagine this being used with large video projectors.
Traditional projectors are neat because it’s easy to make large images – just use a large screen. A major drawback, though, is that the darkest color that they can produce is the color of the screen — and that screen is usually white to reflect the most light. As a result, projectors must be used in low-light situations, or with exceedingly bright bulbs.
Reflective LCD displays (like the kind found in watches, not TVs) work differently – instead of creating light, they just block out the ambient light in areas to create dark spots – as a result, they are low-power and work great in bright light. But, LCD displays don’t scale up to large sizes easily because they can’t be projected.
I think that you could get the benefits of both of these technologies by painting this chemical on a wall. An ultraviolet projector would project an inverse image, creating a large dark green image that is visible even in bright light. There are two main drawbacks, though, that would probably limit the use of this technique to informational and artistic displays: First, the very slow response time (600 msec, which is slower than eink) prevents it from displaying full motion video. Second, it’s only one color – turning it in to a full-color display will require a lot more work.
So, what would you do with something like this?
- Research report: “Photochromism of a Radical Diffusion-Inhibited Hexaarylbiimidazole Derivative with Intense Coloration and Fast Decoloration Performance”
(restricted access, but I included the link because I love the title)
- Wired Science Blog
- The Chem Blog