Printhead having moving roof structure and mechanical seal

1. A nozzle assembly for an inkjet printhead, said nozzle assembly comprising:

a nozzle chamber having a roof and a floor, said roof having a moving portion moveable relative to a static portion and a nozzle opening defined in said roof, such that movement of said moving portion relative to said static portion causes ejection of ink through the nozzle opening;

a thermal bend actuator defining at least part of said moving portion, said actuator comprising:

an upper active beam for connection to drive circuitry; and

a lower passive beam fused to a lower surface of the upper beam element, such that when a current is passed through the active beam, the active beam expands relative to the passive beam, resulting in bending of the actuator towards the floor; and

a polymeric material covering said moving portion and said static portion,

wherein said polymeric material is selected from the group consisting of: polymerized siloxanes, and

wherein said static portion and said lower passive beam are both comprised of silicon dioxide.

2. The nozzle assembly of claim 1 , wherein said nozzle opening is defined in said static portion.

3. The nozzle assembly of claim 1 , wherein said nozzle chamber comprises sidewalls extending between said roof and a substrate, such that said roof is spaced apart from said substrate.

4. The nozzle assembly of claim 3 , wherein said roof and said sidewalls are comprised of silicon dioxide.