Share it! Science : Rewritable "Paper" Uses Light, Not Ink

What if we could print and reuse the same piece of paper without the recycling process or any ink? This could be a reality in the near future. Scientists have developed a process to print words on a "paper" using light. The surface that they have experimented on is a type of plastic, however, further work will be done to use the same principles to print on our traditional paper. The process involves a reaction between dyes that are added to the paper and UV light.

One-use newspaper could be a thing of the past!

The rewritable plastic film, or "paper", is made by adding a dye, a catalyst and a thickening agent. The film is exposed to UV light and words that are printed on a stencil are transferred onto the film. The main idea behind this reaction is that electrons are moved around when exposed to UV light and oxygen. This is an example of a redox, or oxidation-reduction reaction. The paper is colored by the dye, and when it is exposed to the UV light the dye gains electrons (this is the reduction reaction) and the color disappears. When exposed to oxygen in the air, the dye loses electrons (the oxidation reaction) and the color reappears. Cellulose is added to the paper to slow the reaction. Otherwise, the words would fade away much more quickly than we could read them! So far, the researchers are able to print on the paper up to 20 times without losing contrast and resolution. The printing remains on the paper for several days. It is possible to speed up the "erasure" of the words on the paper by exposing it to a heat source. This type of printing would be best for periodicals, such as a newspaper where it is read and then discarded as the writing is only temporary. The long term goal of the project is to develop the process on traditional paper that would be able to rewritten up to 100 times.

See the process here:

Although this technology is not practical for household use yet, it seems that it could be a viable option in the future to reduce waste and cost of printing on paper. According to the EPA, we use an average of 69 million tons of paper and paperboard in the U.S. each year and more than 2 billion books, 350 million magazines and 24 billion newspapers are published each year. If we could revolutionize how we print on paper, some of these numbers would definitely decline. It also sparks the imagination for fun, but perhaps less practical uses- spy messages, pirate treasure maps, scavenger hunts...

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