Integrated circuit device for ink ejection

1. An integrated circuit device which comprises

a substrate;

drive circuitry arranged on the substrate; and

a plurality of micro-electromechanical devices positioned on the substrate, each device comprising:

an actuator connected to the drive circuitry, the actuator including a free end that is displaceable along a path relative to the substrate to perform work, and at least one arm capable of expansion when heated, the arm and the drive circuitry together defining a heating circuit, the arm being configured with respect to the substrate such that when the heating circuit receives an electrical signal from the drive circuitry, the arm expands and thus displace said free end along said path.

2. An integrated circuit device as claimed in claim 1 , in which each micro-electromechanical device includes a fluid ejection member positioned on the free end of the actuator, the integrated circuit device including a plurality of fluid chambers positioned on the substrate, with the substrate defining fluid flow paths that communicate with the fluid chambers, each fluid ejection member being positioned in a respective fluid chamber to eject fluid from the fluid chamber on displacement of the actuator.

3. An integrated circuit device as claimed in claim 2 , in which a sidewall and a roof wall define each fluid chamber, the roof wall defining an ejection port, with the fluid ejection member being displaceable towards and away from the ejection port to eject fluid from the ejection port.

4. An integrated circuit device as claimed in claim 3 , in which each fluid ejection member is in the form of a paddle member that spans a region between the respective fluid chamber and the respective fluid flow path so that, when the heating circuit receives a signal from the drive circuitry, the paddle member is driven towards the fluid ejection port and fluid is drawn into the respective fluid chamber.

5. An integrated circuit device as claimed in claim 4 , in which each paddle member has a projecting formation positioned on a periphery of the paddle member, the formation projecting towards the ejection port so that the efficacy of the paddle member can be maintained while inhibiting contact between the paddle member and a meniscus forming across the ejection port.

6. An integrated circuit device as claimed in claim 1 , in which each actuator includes a heat sink that is positioned on the arm, intermediate ends of that arm, to provide generally uniform heating along the length of the arm.