thumb|205px|Laptop-sized Canon BJ-10v Lite introduced in 1993. It has the same appearance as the first Canon inkjet printer, the BJ-10v introduced in 1990. The inner cover with setting instructions is also displayed.

Inkjet printers operate by propelling variably-sized droplets of liquid or molten material (ink) onto almost any sized page. They are the most common type of computer printer for the general consumerFact: date=November 2007 due to their low cost, high quality of output, capability of printing in different colors, and ease of use.

Like most modern technologies, the present-day inkjet has built on the progress made by many earlier versions. Among many contributors, Epson, Hewlett-Packard and Canon can claim a substantial share of the credit for the development of the modern inkjet. In the worldwide consumer market, four manufacturers account for the majority of inkjet printer sales: Canon, Hewlett-Packard, Epson, and Lexmark.

The emerging ink jet material deposition market also uses ink jet technologies, typically piezoelectric jets, to deposit materials directly on substrates.

Technologies

There are three main technologies in use in contemporary inkjet printers: thermal, piezoelectric, and continuous.

Thermal inkjets

Most consumer inkjet printers (Lexmark, Hewlett-Packard, and Canon) use print cartridges with a series of tiny electrically heated chambers constructed by photolithography. To produce an image, the printer runs a pulse of current through the heating elements causing a steam explosion in the chamber to form a bubble, which propels a droplet of ink onto the paper (hence Canon's tradename of Bubblejet for its inkjets). 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 ink used is known as aqueous (i.e. water-based inks using pigments or dyes) and the print head is generally cheaper to produce than other inkjet technologies. The principle was discovered by Canon engineer Ichiro Endo in August 1977.

Note that thermal inkjets have no relation to thermal printers, which produce images by heating thermal paper, as seen on older fax machines, cash register, ATM receipt, and lottery ticket printers.

Certain Epson printers use special Durabrite Ultra ink which is a type of thermal ink.

Piezoelectric inkjets

Most commercial and industrial ink jet printers use a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element. When a voltage is applied, the piezoelectric material changes shape or size, which generates a pressure pulse in the fluid forcing a droplet of ink from the nozzle. This is essentially the same mechanism as the thermal inkjet but generates the pressure pulse using a different physical principle. Piezoelectric (also called Piezo) ink jet allows a wider variety of inks than thermal or continuous ink jet but the print heads are more expensive. Piezo inkjet technology is often used on production lines to mark products - for instance the use-before date is often applied to products with this technique; in this application the head is stationary and the product moves past. Requirements of this application are a long service life, a relatively large gap between the print head and the substrate, and low operating costs. There is a drop-on-demand process, with software that directs the heads to apply between zero to eight droplets of ink per dot and only where needed. As of November 2008, the fastest cut-sheet inkjet printer on the market is the RISO HC5500, which prints 120 full-color pages per minute 1.