A water-jet printer (or waterjet printer) is a

printer Printer may refer to: Technology * Printer (publishing), a person or a company * Printer (computing), a hardware device * Optical printer for motion picture films People * Nariman Printer (fl. c. 1940), Indian journalist and activist * James ...

that makes use of

paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distributed ...

coated with special

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

s and

ink cartridge An ink cartridge or inkjet cartridge is a component of an inkjet printer that contains the ink that is deposited onto paper during printing. Each ink cartridge contains one or more ink reservoirs; certain producers also add electronic contacts ...

s filled with water to print paper copies of documents. Using paper treated with

oxazolidine An oxazolidine is a five-membered ring compound consisting of three carbon atoms, a nitrogen atom and an oxygen atom. The O atom and NH group are the 1 and 3 positions, respectively. In oxazolidine derivatives, there is always a carbon atom betwee ...

, the water jet changes the colour of the chemical to produce a print which fades in about a day, depending on

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

, and the paper can be re-used rather than being disposed of. The print fades away within about 22 hours at temperatures below 35 degrees

Celsius The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...

(95 degrees

Fahrenheit The Fahrenheit scale () is a temperature scale based on one proposed in 1724 by the physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accounts of how he originally defined his ...

) as the water

evaporates Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

. While the chemical treatment makes the paper slightly more expensive, use of water instead of ink in the printer makes it much cheaper overall, and the only change needed to the printer is to replace what's in the cartridge. The

technology Technology is the application of knowledge to reach practical goals in a specifiable and reproducible way. The word ''technology'' may also mean the product of such an endeavor. The use of technology is widely prevalent in medicine, science, ...

for water-jet printing was developed by a team of Chinese scientists led by Sean Xiao-An Zhang, a

chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...

professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who pr ...

at Jilin University in

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. To create rewritable paper the researchers used four

s. Some of the

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

s of these oxazolidines are colourless in the absence of water. But when the paper is wetted the water changes the dyes’ absorption of visible light. The exact

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

s absorbed vary with the compound used, which allows printing in a variety of colours. The rewriteable paper was made by first coating ordinary paper with a layer of

polyethylene glycol Polyethylene glycol (PEG; ) is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine. PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular we ...

(PEG) to prevent it reacting with the dye, before a second layer of PEG containing the chosen dye was laid on top. Finally, another layer of PEG was added to prevent the dye absorbing water from the air or, conversely, losing water too quickly. The team used a commercial inkjet printer and a cartridge filled with water to print trial documents. The printed page is dry to the touch and the print can be rapidly ‘erased’ by heating it to 70 °C. The print remained legible for around 22 hours before evaporation wiped the page clean. Paper prepared in this way can be printed on and then erased more than 50 times.

References

{{reflist Computer printers Non-impact printing Office equipment