Write With Heat, Cool And Repeat

Chinese researchers have developed paper that can be written or drawn on using heat, then returned to a blank slate by cooling.

AsianScientist (Dec. 20, 2018) – Researchers in China have developed a rewritable paper that can be drawn or printed on reversibly. They published their findings in the journal ACS Applied Materials & Interfaces.

Paper is still widely used in this digital age. Often, printed materials get used once and are then discarded, creating waste and potentially pollution. Over the past few decades, several research groups have pursued different development strategies for producing rewritable paper.

However, many of these approaches have drawbacks, such as complexity in fabrication, chemistry that relies on ultraviolet light to erase the writing, or the need for a constant energy source to maintain the contents of the document.

To overcome these limitations, Dr. Chen Luzhuo and colleagues at Fujian Normal University, China, have invented long-lasting rewritable paper that can be wiped clean simply by changing the temperature. The paper consists of three layers in a sandwich-like structure.

One side of the paper was painted with a dye that rapidly changes from blue to colorless when the temperature is higher than 65 degrees Celsius. The colorless state can be maintained at room temperature.

Meanwhile, the other side of the paper was coated with a black toner layer that produces heat upon excitation with light. The team could thus create images and words using various heat sources, such as a ‘pen’ with a heated tip, a thermal printer or a source of near-infrared light. Importantly, the images and words remained legible for more than six months, much longer than other rewritable papers whose messages fade after a few days or weeks.

To reset the paper, the researchers cooled it down to 14 degrees Fahrenheit, or -10 degrees Celsius. This process could be repeated more than 100 times. The team also produced a rewritable cell phone case, demonstrating that their technique is versatile and amenable to large-scale production.

The article can be found at: Chen et al. (2018) Long-Lasting and Easy-to-Use Rewritable Paper Fabricated by Printing Technology.


Source: American Chemical Society.
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