Nozzle apparatus for an inkjet printhead with a solenoid piston

1. A nozzle apparatus for an inkjet printhead, the apparatus comprising:

a wafer substrate defining a nozzle chamber and a nozzle outlet port;

an electromagnetic piston inside the chamber, the 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.

2. The nozzle apparatus 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 nozzle apparatus of claim 1 , wherein the magnetic piston is manufactured from neodymium iron boron.

4. The nozzle apparatus of claim 3 , 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.

5. The nozzle apparatus of claim 1 , wherein the nozzle chamber is 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.

6. The nozzle apparatus of claim 5 , 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.

7. The nozzle apparatus 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.