(ORDO NEWS) — A group of researchers from the University of California at Riverside has developed a unique light ink. Under certain conditions, they can darken or wear out.
According to the source, the ink is based on titanium nanocrystals. Their interaction with ultraviolet makes them darken, and oxidation with oxygen makes them disappear.
Details of the invention
- According to the authors, the new ink is designed to reduce the amount of paper waste.
- The material is made from three non-toxic components.
- Semiconductor TiO 2 darkens when irradiated with ultraviolet due to charge separation and reduction of titanium atoms.
- The oxygen in the air re-oxidizes the titanium, thus reversing the reaction.
- Seeing this as a perspective, the researchers decided to continue darkening the TiO 2 and support the color change.
- They used nitrogen from urea as a dopant, and a non-toxic substance called diethylene glycol was added to the nanocrystals – it retained TiO 2 in a darkened state.
- The crystals were then applied to glass and paper to form a uniform coating that could be written on with ultraviolet light.
- Now all that was needed to create the inscription was 30 seconds of UV rays with a wavelength of less than 400 nanometers. The scientists emphasized that this does not require a strong light source – it is the necessary range that is important.
- The result was a high-contrast pattern that only disappeared when heated or oxidized.
During the experiments, the authors created patterns or printed text. They also recorded by hand with a laser pen.
Both options produced a high contrast pattern that remained stable for many hours. It only disappeared when heated, or slowly faded due to oxidation.
The team notes that the life of the print can be extended by coating the surface of the film with a protective layer of non-toxic polymer, which will protect the surface from oxygen.
In general, the new technology provides up to 50 write and erase cycles without loss of contrast. It will be needed in areas where reusable surfaces are in demand or information needs to be rewritten several times, for example, transport tickets, coupons and information boards.
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