Undoubtedly, paper has tremendously contributed to the development of our civilization by reinventing the way we record history, communicate, and write down our thoughts. Despite the obvious advances in digital technology, our world still greatly relies on paper. The consumption of paper globally has been continuously growing during last three decades, with 300 million tons of paper currently being produced on an yearly basis.
Unfortunately, the use of paper comes at the cost of deleterious environmental consequences. The paper industry has evolved into a major contributor to environmental problems due to deforestation, chemical use and disposal, energy and water consumption. This has intensified the exploration of alternative solutions that have recently led to the exemplary concept of rewritable paper based on functional materials and systems.
As the term indicates, the concept precisely relies on the fact that rewritable paper can be reused multiple times based on a “write-erase-write” cycle, therefore, reducing the demands of paper consumption. Reversible writing and erasing occurs through coloration or de-coloration of materials. With this in mind, functional materials with chromogenic properties that demonstrate a design-driven reversible chromism (change of color as a response to external stimuli), have recently received significant attention as potential candidates for rewritable paper.
In their review in Advanced Materials, Prof. Kim and co-authors from the Institute of Nano Science and Technology – INST in Korea, present a detailed overview of concepts, design principles and examples of rewritable paper applications. Depending on the stimulation protocol and mechanistic description of chromism, the article categorizes the approaches depending on the type of materials such as hydrochromic, photochromic, mechanochromic, thermochromic, halochromic, redox dyes and photonic crystals.
The authors of the review say, “As it is highly likely that practical applications of rewritable paper will emerge in the future after considerable effort is given to addressing the various key issues, we hope that this review article will serve as stimulus for future research in this area.”