Printhead integrated circuit having suspended heater elements

1. An inkjet printhead integrated circuit comprising:

a multi-layer substrate that defines a plurality of ink inlet passages and incorporates drive circuitry;

side walls extending from the substrate;

a nozzle plate positioned on the side walls and, together with the side walls, defines a plurality of nozzle chambers in fluid communication with respective ink inlet passages and nozzles in fluid communication with respective nozzle chambers; and

at least one heater element suspended in each nozzle chamber and connected to the drive circuitry to be heated on receipt of an electrical signal from the drive circuitry to form a gas bubble in ink in the nozzle chamber so that a drop of ink is ejected from the nozzle chamber.

2. An inkjet printhead integrated circuit as claimed in claim 1 , in which at least the nozzle plate is the result of a chemical vapour deposition and etching process.

3. An inkjet printhead integrated circuit as claimed in claim 1 , in which the heater elements each define at least one elongate loop.

4. An inkjet printhead integrated circuit as claimed in claim 3 , in which two heater elements are suspended in each nozzle chamber.

5. An inkjet printhead integrated circuit as claimed in claim 4 , in which the heater elements in each nozzle chamber are substantially the same length, but one of the heater elements is twice the width of the other heater element.

6. An inkjet printhead integrated circuit as claimed in claim 1 , in which the heater elements are suspended in each nozzle chamber to be substantially completely immersed in ink.

7. An inkjet printhead integrated circuit as claimed in claim 1 , in which the heater elements are suspended in each nozzle chamber to be positioned at the surface of the ink, so that the ink is only below the heater elements.

8. An inkjet printhead integrated circuit as claimed in claim 1 , in which the heater elements are suspended, cantilever fashion, in the respective nozzle chambers.