Method of fabricating printhead for ejecting ink supplied under pulsed pressure

1. A method of fabricating a printhead for ejecting ink supplied under pulsed pressure, comprising the steps of:

depositing sacrificial material on a drive circuitry substrate;

etching the sacrificial material to define first deposition zones;

depositing thermally expandable first material on the first deposition zones;

etching the first material and the substrate to define second deposition zones;

depositing conductive material on the second deposition zones so that the conductive material is on the etched first material and substrate;

etching the conductive material to define heating circuitry and connections between the heating and drive circuitry;

depositing thermally expandable second material to embed the heating circuitry in the first and second materials;

etching the second material to define thermally expandable actuator arms and associated closure members;

depositing and etching third material so as to form nozzle chambers having inkjet ports and associated ones of the actuator arms and closure members;

etching the sacrificial material so that each actuator arm has one end connected to the substrate and the other end connected to the associated closure member; and

etching the substrate to form ink supply channels in fluid communication with the nozzle chambers for supply of the ink under pulsed pressure which is ejected from the inkjet ports when the respective closure members are moved under thermal expansion of the respective actuator arms from a position at which the inkjet port is closed to a position at which the ink jetport is open.

2. A method as claimed in claim 1 , in which the first and second materials are polytetrafluoroethylene and the conductive material is copper.

3. A method as claimed in claim 1 , in which the nozzle chambers are deposited and etched so that the associated actuator arms and closure members are positioned within respective ones of the nozzle chambers.

4. A method as claimed in claim 1 , in which the second material is etched so that each actuator arm is shaped so that, in a rest condition, the actuator arm encloses an arc with the heating circuitry positioned so that, when the first and second materials are heated, differential thermal expansion of the first and second materials causes the actuator arm to at least partially straighten and subsequent cooling of the first and second materials causes the actuator arm to return to the rest condition thereby displacing the closure member between the closed and open positions.

5. A method as claimed in claim 4 , in which the first and second materials are etched to so that each actuator arm defines a coil that partially uncoils when the first and second materials undergo the differential thermal expansion.

6. A method as claimed in claim 5 , in which the conductive material is etched so that the heating circuitry includes a heater positioned proximate an inner edge of the actuator coil and a return trace positioned outwardly of the heater, so that an inner region of the actuator coil is heated to a greater extent with the result that the inner region expands to a greater extent that a remainder of the actuator coil.

7. A method as claimed in claim 6 , in which the conductive material is etched so that a serpentine length of conductive material defines each heater.