Transformation of Crab Shells Into Sustainable Water‐Responsive Re‐Printable Paper

ABSTRACT Cellulose‐based paper has greatly contributed to the development and spread of human civilization. However, its single‐use and massive consumption cause serious environmental problems and deforestation. Here, we report a sustainable re‐printable paper made of chitin fibers, the second most abundant natural polymer, which can be reused and recycled multiple times. We elucidate the molecular mechanisms governing the hydration‐responsive microstructural behavior of the micro‐nanostructured chitin paper. Based on the hydration and surface charge‐induced morphological change, chitin paper can disintegrate the bonding between toner and substrate, allowing toner to be easily removed through ultrasonic cleaning. This in situ unprinting strategy enables the chitin paper to be reused over 10 times without damage, featuring obvious advantages than conventional single‐use cellulose paper. Given its promising attributes, including excellent mechanical properties (67.9 m Pa), wet strength (9.7 m Pa), printability, recyclability, and biodegradability, chitin paper stands out as a promising alternative to traditional cellulose paper on the market.