UF Research: Cheap Electronic Displays Possible On Many Products
GAINESVILLE, Fla. — It won’t be in time for this Christmas this year, but electronic displays may soon migrate from computer screens and television sets to such inexpensive consumer products as coffee machines, toys and even greeting cards.
A University of Florida chemistry professor has designed and successfully tested a new concept in “all polymer electrochromic devices” – dime-thick, flexible sheets of plastic that change color or become opaque or clear when an electrical current is applied. The technology isn’t yet mature, but the achievement suggests the possibility that future electronic displays could be produced in mass quantities using established plastics manufacturing techniques — and then applied like stickers to a wide range of consumer products, said chemistry Professor John Reynolds.
The first applications for the technology might be a greeting card that, for example, would appear one color in one instant but then flash “Happy Birthday” the next, with the words moving across the display, Reynolds said. As the films become more advanced, advertisers could use them to describe or depict a product’s features right on the package. They could also prove useful on appliances such as coffee makers, which could depict color images of the desired brewing strength of a given pot of coffee.
“You could use these displays as advertising tools, making them part of the packaging of products,” he said. “You could put them on the cover of a book or magazine. You might also see them on inexpensive appliances.”
Reynolds group has applied for several patents on the research, which has received approximately $3.5 million in funding from a number of agencies including the National Science Foundation, the U.S. Department of Defense and many companies over the last decade. In addition to the many commercial uses these electrochromic polymers may have, the U.S. Air Force is interested in using the films to create automatically tinting windows for jets and other applications.
The UF group has spent several years investigating what is called the electrochromic effect, or the process through which certain molecules change color when subjected to an electric current. His latest effort, “complementary electrochromic polymers,” is twin polymer films sandwiched together. The films undergo concurrent changes that allow colors to be mixed and matched. Like batteries with their positive anodes and negative cathodes, they work in tandem based on opposite charges. Depending on the charge each film receives, the films can change from clear to opaque, opaque to clear or from one color to another.
Reynolds’ group has slowly increased the number of colors the films can display to a broad color palette, as well as the speed at which they transition. Until recently, however, he and his colleagues had only achieved the results on glass, which limited their applications because glass is heavy, inflexible and breakable.
But in a paper published earlier this year in the journal Advanced Materials, Reynolds described putting the polymers on plastic for the first time. The key step, he said, was replacing a traditional electrode with a commercial conducting polymer electrode that is coated onto sheets of plastic.
Reynolds has used the new technique to build small card-sized electrochromic devices. The films are flexible, with Reynolds showing they still exhibit color changes when wrapped around a marker-sized cylinder. In his related research, Reynolds has demonstrated he can use an airbrush spraying-technique combined with a porous reflective gold-coated film to create a “rapid switching effect” in the film, with two colors rapidly flashing back and forth.
The flash occurs about 10 times per second, too slow for video, which must change colors at least 33 times per second to fool the human eye into perceiving motion, but there is nothing to suggest a faster switch can’t eventually be achieved with more research, Reynolds said.
“This technology is rapidly moving from an interesting concept into something that is really more complete,” he said.