Ink jet computer printers are the type of printer most commonly sold to the individual computer user. Ink jet technology was allegedly invented by Hewlett-Packard, whose printer division is still the most profitable division.
An ink jet usually works by having a print cartridge with a series of tiny electrically-heated chambers that are constructed by photolithography. To print, the printer runs a pulse of current through the heating elements. A steam explosion in the chamber propels a droplet of ink. The ink's surface tension pumps another charge of ink into the chamber through a narrow channel attached to an ink reservoir.
Older ink jet printers directed ink streams electrostatically; ultrasound was used to induce waves in the ink, which then broke into little droplets that would fall on the right place on the page.
Compared to earlier consumer-oriented printers, ink jets have a number of advantages. Compared to ribbon printers like the old Apple ImageWriter family, for example, they're practically silent. Many are able to produce high resolutions, and color printing of quite reasonable quality is widely available – as of 2003 applicable to photo printing in the home.
Disadvantages of ink jets include flimsy print heads that are prone to clogging, and ink cartridges that are expensive, sometimes costing US$20–$30 or more. This typically leads value minded consumers to consider laser printers for medium to high volume printer applications.
A common business model for ink jet printers is to sell the actual printer nearly at cost, while significantly marking up the price of the (proprietary) ink cartridges. This sometimes generates ire and/or disappointment among ink jet purchasers, who find their "inexpensive" printer turns out to be much more expensive in use than they'd first imagined, Unless they use a recycled ink cartridges.
