Inkjet technology

Inkjet technology is a method for depositing liquid droplets on a substrate. It was originally developed for the publishing industry, but has become a popular method in digital fabrication of electronic and mechanical devices. Although both terms, "inkjet technology" and "inkjet printing", are commonly used interchangeably, inkjet printing usually refers to the publishing industry, used for printing graphical content, while inkjet technology usually refers to the general purpose fabrication via inkjetting.

Inks must have high conductivity, high oxidation resistance and low sintering temperature.

Various drop formation technologies exist, and can be classified into two main types: continuous inkjet (CIJ) and drop-on-demand (DOD).

While CIJ has a straightforward drop creation and sophisticated drop trajectory manipulation, DOD has sophisticated drop creation and no trajectory manipulation.

In this method, drops of ink are released individually, on demand, by a voltage signal. Released drops fall vertically without any trajectory manipulation. Commercial printheads can have tens to thousands of nozzles.

The two leading technologies for forcing ink out of a nozzle on demand are thermal DOD and piezoelectric DOD. Additional technologies include electrospray, acoustic discharge, electrostatic membrane and thermal bimorph.

Piezoelectric DOD was invented in the 1970s. One disadvantage of the piezo-DOD method is that jettable inks must have viscosity and surface tension within a relatively strict range.

Thermal DOD was introduced in the 1980s by Canon and Hewlett-Packard.

One disadvantage of this method is that the variety of inks compatible with TIJ is essentially limited, because this method is compatible with inks that have high vapour pressure, low boiling point and high kogation stability. Water being such a solvent, limited the popularity of this method for non-industrial photo printing only, where water-based inks are used.

In this method, a column of ink is released continuously from the nozzle. The ink column spontaneously breaks into separate drops due to the Plateau–Rayleigh flow instability. The formed ink drops are either deflected by an electric field towards the desired location on the substrate, or collected for reuse. CIJ printheads can be either have a single jet (nozzle) or multiple jets (nozzles).

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