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Techno Trends

The big ideas that are changing everything

Rewriteable “Paper”

Somehow the dawn of the computer era fell woefully short of the promise for a “paperless society.” In fact, by some estimates, ninety percent of the information shared day-to-day in businesses is still printed on paper, the bulk of which is discarded after a single use.

Sure…paper can be recycled, but in addition to the expense of the process alone, a lot of time and effort goes into protecting the information on that paper, before it even leaves a facility. Wouldn’t it be nice to be able to recycle and reuse printed materials yourself? Well, that’s the basic idea behind a new rewriteable medium being developed with some help from the U.S. Department of Energy.

A glass or plastic substrate is coated with a commercial redox (color-switching) dye (either blue, red or green) to form an imaging layer. Titania nanocrystals are added as catalysts and hydroxyethyl cellulose is used as a thickening agent. When a photomask is placed over the film, exposure to ultraviolet (UV) light bleaches the dye, except where the mask prevents it. The resulting image will be retained for about three days under normal ambient conditions – long enough to be practical for a variety of printed materials, such as newspapers – and the current films can be re-written up to twenty times without loss of contrast or resolution. Heating the material to 115 degrees Centigrade re-oxidizes the dye to its original color.

To expand the potential applications, researchers are currently exploring ways to increase the image life and number of print-erase cycles, as well as paper and multi-color options.

For information: Yadong Yin, University of California Riverside, 900 University Avenue, Chemistry Department, 0302 Pierce Annex, Riverside, CA  92521; phone: 951-827-4965; fax: 951-827-4713; email: yadong.yin@ucr.edu; Web site: www.ucr.edu/  

   

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