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The race to produce a high-resolution, full-color printer that is economical and reliable enough to use with a personal computer has prompted a great deal of research on "drop-on-demand" ink-jet printing.

Conventional ink-jet printers currently in use produce a steady stream of ink droplets. Some of these droplets are electrostatically attracted to a paper surface to form printed characters from an array of dots, while the bulk of the ink is recirculated. In the newer, "drop-on-demand" technology, high-frequency impulses force the ejection of ink drops only when the ink is needed. This greatly simplifies the printer's inner workings, and with the use of four separate ink cartridges (for cyan, magenta, yellow and black ink) and an array of nozzles, it also allows the possibility of full-color printing.

Nevertheless, technical difficulties remain. The frequency at which drops are ejected in a regular pattern has an upper limit. To achieve rapid, high-resolution color printing that packs 240 dots into an inch of space, a large array of nozzles must be used. Recently, researchers at NEC in Japan designed a 96-nozzle head that shows promise. However, print quality is still uneven because of variations in drop size and errors in paper feeding and positioning. Although a few companies are already marketing low-resolution "drop-on-demand" ink-jet printers, commercial, high-resolution printers are still several years away.

Ivars Peterson, ScienceNews, 1984