The Difference Between a Thermal Inkjet & an Inkjet

Inkjet printers are essential computer peripherals in many people's lives, aiding in the creation of everything from letters to life-size posters. However, the term "inkjet printer" covers a few different types of printing mechanisms. Between continuous, thermal and piezoelectric inkjet printers, there are many important distinctions that will provide you with insight into the surprisingly complex world of adding ink onto paper.

An inkjet printer is a printer that forces black or colored ink through a chamber or nozzle onto a medium such as paper. These types of printers are often used in homes, offices and large-scale commercial operations. Commercial inkjet models, while conceptually similar to the home versions, have a few key differences that make them impractical in a consumer environment—namely that they're more complicated, more expensive and less efficient for at-home printing tasks.

There are two types of inkjet printers: continuous inkjet and drop-on-demand. Under the drop-on-demand umbrella are thermal inkjet and piezoelectric inkjet printers, both of which have a strong presence in the consumer market. Continuous inkjet printers are functionally very different from drop-on-demand printers and are used mostly for commercial purposes.

In a continuous inkjet printer, the ink is constantly flowing. As the ink flows through the system, droplets are deflected by a piezoelectric crystal, either into a reservoir to be reused or onto the medium. The advantage of this type of system is that, due to the constant flow of ink, certain types of ink can be used that would clog up a thermal inkjet or piezoelectric inkjet printer; printing also occurs quickly. However, continuous inkjet printers are more expensive than thermal and piezoelectric inkjet printers and tend to waste ink (thermal and piezoelectric inkjet printers are better at spraying ink only where needed).

On the inside of an ink cartridge in a thermal inkjet printer, a resistor is heated that causes an air bubble to form and force a drop of ink onto the waiting medium. The thermal inkjet printer is the most common form of inkjet printer seen in consumer households because it tends to be more affordable (though slower than the commercial inkjet printers). A thermal inkjet printer, however, is not the same as a thermal printer, which heats special paper to form an image on the paper; this type of printer is often used to print receipts and bar codes.

Piezoelectric inkjet printers are consumer-oriented printers like thermal inkjet printers. Functionally, these are almost identical to thermal inkjet printers, except that instead of forming an air bubble in the ink chamber with heat, they cause crystals in the ink chamber to expand with an electric charge, which forces out the ink.