Patent ID: 7328977

Claim:
An inkjet printhead comprising a plurality of micro-electromechanical ejection devices for ejecting ink onto print media, at least some of the devices comprising: a substrate; a semiconductor layer positioned on the substrate, the substrate and the semiconductor layer defining a fluid inlet chamber; a nozzle chamber defining structure positioned on the substrate to define a nozzle chamber in fluid communication with the fluid inlet chamber and a fluid ejection port in fluid communication with the nozzle chamber; an actuator that is fixed, at one end, to the substrate, the actuator incorporating a heating circuit electrically connected to the semiconductor layer, the heating circuit being configured to generate thermal differential expansion and contraction upon excitation and de-excitation by the semiconductor layer so as to effect displacement of the actuator relative to the substrate; a fluid ejection member fixed to an opposite end of the actuator and positioned with respect to the nozzle chamber so that resultant displacement of the fluid ejection member causes fluid to be ejected from the fluid ejection port; and a movement sensor that is positioned on the actuator to determine an extent of movement of the actuator.