Thermal DOD Ink Jet Printing

Thermal (thermal DOD inkjet)

A Canon inkjet with CMYK cartridges

Most consumer inkjet printers, from companies including Canon, Hewlett-Packard, and Lexmark (but not Epson), use print cartridges with a series of tiny chambers each containing a heater, all of which are constructed by photolithography. To eject a droplet from each chamber, a pulse of current is passed through the heating element causing a rapid vaporisation of the ink in the chamber to form a bubble, which causes a large pressure increase, propelling a droplet of ink onto the paper (hence Canon's tradename of Bubble Jet). The ink's surface tension, as well as the condensation and thus contraction of the vapor bubble, pulls a further charge of ink into the chamber through a narrow channel attached to an ink reservoir.
The inks used are usually water-based (aqueous) and use either pigments or dyes as the colourant. The inks used must have a volatile component to form the vapour bubble, otherwise droplet ejection cannot occur. As no special materials are required, the print head is generally cheaper to produce than in other inkjet technologies. The thermal inkjet principle was discovered by Canon engineer Ichiro Endo in August 1977.
Thermal inkjet printers are not the same as thermal printers, which produce images by heating thermal paper, as seen on older fax machines, cash registers, ATM receipt printers, and lottery ticket printers.