Continuous inkjet printing is an established technology that has been around for 150 years. Simply put, it is a method of droplet generation where once the print head is running there is a continuous stream of fluid. Although this concept was first patented by Lord Kelvin in 1867, the first commercial devices appeared more than 80 years later, in 1951 by Siemens. Initially the technology was used for high speed, contact-less printing of variable information such as expiration dates, batch codes as well as names and product logos.

Continuous inkjet printing begins with a high-pressure pump that directs liquid from a reservoir to a bank of micrometer-sized nozzles, thus creating a continuous stream of droplets at frequencies determined by the oscillations of a vibrating piezoelectric crystal. For printing applications specifically, ink droplets are being deflected from the continuous stream due to the presence of an external electric field. This generates patterns on the surface of a printing medium. Some of the advantages of this technique are high throughput, high droplet velocities, increased distances from printhead to substrate, and no nozzle clogging due to continuous operation. Thanks to these positive attributes, this technology has, nowadays, evolved from regular printing ink on paper to depositing a variety of materials (even living cells), to creating modern OLED (Organic Light Emitting Diode) displays.