Inkjet printers

An inkjet printer is a type of printer which uses electric charge in its operation. While shuttling back and forth across the paper, the inkjet printer “ejects” a thin stream of ink. The ink is forced out of a small nozzle and breaks up into extremely small droplets. During their flight, the droplets pass through two electrical components, a “charging electrode” and the “deflection plates” (a parallel plate capacitor).

When the printhead moves over regions of the paper which are not to be inked, the charging electrode is left on and gives the ink droplets a net charge. The deflection plates divert such charged drops into a gutter and in this way such drops are not able to reach the paper. Whenever ink is to be placed on the paper, the charging control, responding to computer, turns off the charging electrode.

The uncharged droplets fly straight through the deflection plates and strike the paper. Schematic diagram of such a printer is shown in Figure above. An inkjet printhead ejects a steady flow of ink droplets. The charging electrodes are used to charge the droplets that are not needed on the paper. Charged droplets are deflected into a gutter by the deflection plates, while uncharged droplets fly straight onto the paper.

“lnkjet printers can also produce coloured copies.”