Paper memory

''“What we are doing is exploiting the memory effect,” Martins explains. “We have a sort of type of integrated foam composed of fibers set up that increases the capability of storing carriers – or charges – in our paper.” These charges allow the paper to display information that is also erasable – and the paper is rewritable so that additional information can be added.
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“If I want my paper to catch information,” he explains, “I can apply a signal of, say, five volts. And it writes on the paper. If I want to erase the information, I basically apply minus five volts – the opposite. But, at the same time, I can write another layer of information using 10 volts. The paper can distinguish between the two, and even if I erase the five volt information, the 10 volt information remains.”
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“You can have multiple layers of information on a product label,” he says. “Instead of just the expiring date, you can have more than this, including information about when it went on the shelves.” However, Martins also sees the potential for this paper’s use in books. “You can create a display, bringing a new dimension to the paper,” he says. “You push a button and it changes. You can see a static or dynamic picture, or even another page.” '' [source, article]