In drop-on-demand inkjet printers, the printing heads eject discontinuous droplets onto the printing substrate to produce the image by means of the heat-induced explosion of ink bubbles (e.g. in bubble jet printers and thermal inkjets).
In the drop-on-demand technique, the ink in the tiny print cartridge chambers is first heated until it vaporises. Bubbles of ink are formed that expand and inject a small drop of ink through a nozzle onto the printing surface.
In the case of drop-on-demand printers, each nozzle is individually controlled. The advantages of the system are the simplicity of the concept and the low cost. Particularly large size fonts can be printed because of the relatively large diameter of the nozzles. The resultant printed image is clean and readily legible. It is also possible to produce good quality printed images on sensitive and uneven surfaces. There are special inks in various colours for use on porous surfaces (paper, cardboard, wood etc.) and smooth, impermeable surfaces (plastic, metal, glass etc.).