Look a little closer
See the mechanism
A bubble displaces liquid through a nozzle
Read the diagram steps
Liquid at the nozzle. The thermal chamber contains liquid ink above a small heater. A nozzle provides the exit toward the paper.
Heater pulse ejects a drop. The heater produces a vapor bubble. As it expands, the bubble displaces liquid through the nozzle and launches a drop.
Original functional schematic; dimensions and motion are exaggerated, not measured. Thermal ejection only. The chamber is enlarged and not a fabrication drawing; piezoelectric inkjets use a different actuator.
Diagram basis: Canon: thermal process and FINE ejection mechanism.
Sources: Canon
Heat creates the pressure pulse
Canon's thermal process generates bubbles using a heater. The pressure acts on liquid ink inside a small chamber, pushing some of it through the nozzle. Ink is the marking material; the bubble supplies the displacement that launches it.
Sources: Canon
Two movements place the dots
In a scanning inkjet printer, the printhead travels across the sheet while rollers advance the paper in small steps. Nozzle firing and these movements work together to put drops at chosen positions. A page grows from successive passes rather than arriving in one spray.
Sources: Canon
A piezo head uses another way to push
Not every inkjet needs a heater. A piezoelectric element changes shape when voltage is applied, squeezing ink out. Thermal and piezo systems share the aim of ejecting controlled drops, but they create the pressure pulse in different ways.
Sources: Canon
The thing to remember
For a thermal head, an expanding bubble turns an electrical pulse into a liquid drop.
What this example leaves out
This explains a thermal printhead in a scanning-carriage printer. Stationary arrays and piezoelectric heads use other arrangements.
Sources & further reading
Source access dates are listed below. Manufacturer descriptions and patents support the specific constructions described, not every product.
- Inkjet Printers ↗
Canon · Retrieved 2026-10-18 · Thermal bubble ejection, distinction from piezo actuation, moving printhead and incremental roller paper feed.
Read How inkjet printers work and FINE Ejection Mechanism for Accurate Placement of Ink Droplets. Thermal architecture selected; no claim that all inkjets heat ink. Canon uses air bubbles in overview; article says vapor bubble to avoid implying injected air.
