This Rewritable Paper Can Be Used More Than 40 Times

Scientists have developed a low-cost, environmentally friendly way to create printed material with rewritable paper that can reduce paper wastage. Even in the present digital age, the world still relies on paper and ink, most of which ends up in landfills or recycling centers. Researchers made the new material by mixing low-toxicity tungsten oxide and polyvinyl pyrrolidone, a common polymer used in medicines and food. To “print” on it, they exposed the material to ultraviolet light for 30 seconds, and it changed from white to a deep blue. To make pictures or words, a stencil can be used so that only the exposed parts turn blue. To erase them, the material can be put in ambient conditions for a day or two. To speed up the erasing, the researchers added heat to make the color disappear in 30 minutes. Alternatively, adding a small amount of polyacrylonitrile to the material can make the designs last for up to 10 days. Tests showed that the material can be printed on and erased 40 times before the quality started to decline. More paper is now recovered for recycling than almost all other materials combined, researchers said. The new material saves energy, water, and landfill space and greenhouse gas emissions.