Patent ID: 7156494

Claim:
An inkjet printhead chip which comprises a wafer substrate; a drive circuitry layer positioned on the wafer substrate; a plurality of nozzle chambers defined in the wafer substrate; a plurality of ink inlet openings defined in the wafer substrate, in fluid communication with respective nozzle chambers; a plurality of nozzle chamber walls opposite respective ink inlet openings and each defining an ink ejection port; and a plurality of ink ejection actuators connected to the drive circuitiy layer, at least one actuator being positioned in each wall and being displaceable into the respective nozzle chamber to reduce a volume of the nozzle chamber and thus to eject ink from the nozzle chamber; each ink ejection actuator having an actuator arm of a material that has a coefficient of thermal expansion which is such that expansion of the actuator arm can be used to perform work and a heating circuit positioned in the actuator arm such that, when the arm is heated, the arm experiences thermal differential expansion and is thus displaced into the nozzle chamber.