A team of materials scientists in China has created a ‘rewritable’ paper that can be drawn or printed on over and over again; the messages can last more than half a year, compared to other rewritable papers whose messages fade after a few days or a few months. The team’s work was published in the journal ACS Applied Materials & Interfaces.
Chen et al’s rewritable paper demonstrates excellent rewriting performances (legible time > 6 months and reversibility > 100 times); its color rapidly changes from blue to colorlessness when the temperature is higher than 149 degrees Fahrenheit (65 degrees Celsius), and the colorless state can be maintained at room temperature; the color returns to blue when the temperature is lower than 14 degrees Fahrenheit (minus 10 degrees Celsius). Image credit: Chen et al, doi: 10.1021/acsami.8b14625.
Although we live in a digital age, there is still a huge need for traditional printing materials.
Unfortunately, most of the printing materials are only used for one-time reading before being disposed of, which leads to a huge environmental problem, such as solid waste and chemical pollution.
Therefore, rewritable paper, thermochromic displays, photonic crystal materials and shape memory polymers are alternative approaches to solve this problem.
“The idea for rewritable paper isn’t new, with several research groups pursuing different development strategies over the past few decades,” said Fujian Normal University researcher Luzhuo Chen and co-authors.
“But many of these approaches have drawbacks, such as complex fabrication, chemistry that relies on UV light to erase the writing or a constant need for energy to maintain the document.”
To overcome these limitations, the scientists wanted to develop a simple method for making long-lasting rewritable paper that can be wiped clean simply by changing the temperature.
“The new material consists of three layers in a sandwich-like structure,” they explained.
“We painted one side of a piece of paper with a blue dye that becomes colorless upon heating, just like the t-shirts popular in the 1990s that changed color when they were touched with a warm hand.”
“Then, the other side of the paper was coated with a black toner layer that produces heat upon excitation with light.”
Using an electrothermal pen, a thermal printer or a source of near-IR light, the researchers created images and words that remained legible for more than six months. They also produced a rewritable cell phone case.
To reset the paper, the team cooled it down to 14 degrees Fahrenheit (minus 10 degrees Celsius). This process could be repeated more than 100 times.
“This rewritable paper is easy for large-scale production and will have promising opportunities in practical applications, such as long-lasting information recording and reading, rewritable label, reprintable displays, and so on,” Dr. Chen and colleagues said.
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Luzhuo Chen et al. 2018. Long-Lasting and Easy-to-Use Rewritable Paper Fabricated by Printing Technology. ACS Appl. Mater. Interfaces 10 (46): 40149-40155; doi: 10.1021/acsami.8b14625
