According to Science and Technology Daily news on November 22, on November 16, Professor Zhang Xiaoan's research team of the College of Chemistry of Jilin University and the State Key Laboratory of Supramolecular Structure and Materials made a breakthrough in inkless water-jet printing, and its innovation results were published again in the journal Nature Communications. Ink-free water-jet printing technology is a technology that replaces ink with water to achieve printing, and the core technology is printing paper, which not only helps to solve the problems of ink cartridge blockage and frequent replacement of ink cartridges faced by inkjet printing consumers, but also helps to reduce environmental pollution and waste of resources.

The original technology was fraught with difficulties

In January 2014, Nature Communications magazine reported for the first time the ink-free water-jet printing technology of Professor Zhang Xiaoan's research team, which has attracted high praise and widespread attention from experts and scholars at home and abroad, industry peers and international and domestic mainstream media.

Although ink-free water-jet printing technology has many advantages, however, because the previous water-chromic repeatable printing paper is based on a single water-chromic dye system, whenever a new color of repeatable printing paper is needed, it is often necessary to design and synthesize a new water-chromic dye, which is followed by more complex synthesis technology, higher cost and longer cycle.

Among them, the development of black hydrochromic dyes is particularly difficult. In addition, the short writing retention time and the water resistance of the substrate are also the technical bottlenecks restricting the practical application of this technology.

New technology has many benefits

In view of the bottleneck of the original technology, Zhang Xiaoan's research team, inspired by the living system, cleverly expanded the single water-chromic dye system into a bimolecular water-collaborative color-changing system composed of acid-chromic dyes and color developing agents. Before encountering water, the dye and developer do not develop color, and after encountering water, the developer interacts with the dye to display color (Figure a). Different colors of water color can be achieved by selecting different colors of human acid chromic dyes, which simplifies the color expansion of repeatable erasable paper (Figure b).

Figure a: The mechanism intention of the hydrochromic rewritable paper (right) and the previous work (left); Figure b: Spray printing with different colors shows the actual picture

"Because most of the acid-chromic dyes and developers used have been industrialized, they can be purchased directly, eliminating the complicated synthesis process and greatly reducing the cost of water-chromic repeatable erasing paper." "The project leader introduced that, especially through the purchase of commercially available black dye, it can be very simple to achieve the long-awaited black spray printing display."

The color degree and color purity of the black obtained by water-jet printing are very high, basically comparable to the existing black inkjet printing, and the writing retention time can be several months to half a year. Of course, during this period, information can also be erased at any time through the printer's heating program.

Black water jet printing process and printing effect

Industrialization will not be a dream

In order to rapidly promote the industrialization process of ink-free water-jet printing technology and realize the product market promotion at an early date, Zhang Xiaoan scientific research team has carried out in-depth cooperation with Lucai Medical Technology Company under China Aerospace Science and Technology Corporation, and achieved the preparation of water-chromic reusable erasable paper based on high strength and strong water resistance, which significantly improves the recycling performance of paper. And can achieve large-scale mechanized production.

Workshop photo and black spray print effect

In addition, this research progress has laid a solid foundation for the completion of green inkless printing technology from the laboratory to the market. Related technologies have been declared and authorized by domestic invention patents and United States invention patents.