PRINTHEAD INTEGRATED CIRCUIT WITH A SOLENOID PISTON

1 . A printhead integrated circuit comprising:

a wafer substrate defining a nozzle outlet port;

an electromagnetic piston mounted to the wafer substrate via torsion springs, said piston operatively forced towards the outlet port when activated; and

a solenoid coil positioned on the wafer substrate about the piston to activate the piston when a current is passed through the coil, wherein.

the piston is magnetised during a final high temperature step in a fabrication process of the nozzle apparatus to ensure that the Curie temperature is not exceeded after magnetisation.

2 . The printhead integrated circuit of claim 1 , wherein the current to the coil is provided via aluminium connectors which interconnect the coil with a semi-conductor drive transistor and logic layer located on the substrate.

3 . The printhead integrated circuit of claim 1 , wherein the magnetic piston is manufactured from neodymium iron boron.

4 . The printhead integrated circuit of claim 1 , further comprising a nozzle chamber in which the piston is disposed, the nozzle chamber being slightly wider than the piston with a gap between the piston and the nozzle chamber dimensioned to ensure that the piston does not contact the nozzle chamber when said piston is activated.

5 . The printhead integrated circuit of claim 4 , wherein the nozzle chamber is dimensioned to have a depth so that air ingested through the outlet port when the piston returns to a quiescent state does not extend to the piston.

6 . The printhead integrated circuit of claim 1 , wherein the solenoid coil is a double layer spiral coil of copper to obtain suitably high field strength with a relatively small radius.