"It's a gel that can shrink or expand so you have this layered sort of system and the fact that it has layers which have different optical properties causes light to be reflected from these layers," says Thomas.
Thomas says that the gel can be fine-tuned for many different uses. He says it could be tailored to respond to moisture and could be used in the food processing and distribution industries to monitor food safety and quality.
"They don't require any power. You just look at them, you see a color, and you then translate the color into whether or not you've got a lot or a little [of the stimuli being measured.]," explains Thomas.
With funding from Defense Advanced Research Projects Agency (DARPA), he has more high-tech ideas in mind, like aircraft stability.
"An alternative would be to coat this wing with a layer a thin layer of the polymer which would have a particular color when it's relaxed with the air--no airflow. When you turn on the airflow the pressure in the different parts of the wing would cause lesser or greater extensive compression. This would change the color say from red in some areas to green in others to blue in the areas where it's most compressed. And you could optically read out continuously over the surface what the local pressures were," says Thomas.
But Thomas also explains that the advantage of his gel is that it is an inexpensive, tunable visual indicator. If high accuracy is needed, other existing products would be more appropriate.
"So I think a lot of the applications for our gels are going to be those in which you're interested in whether things are in the safe range or they've gone beyond what your tolerance is," says Thomas.
Thomas says novelty items such as color changing clothes or umbrellas will probably be developed before the more large-scale applications like food safety.
The study was published online in Nature Materials, October 21, 2007 (Study Authors: Youngjong Kang, Joseph J. Walish, Taras Gorishnyy and EdwinL. Thomas); it was funded by the National Science Foundation and Defense Advanced Research Projects Agency (DARPA).