Inkjet nozzle arrangement incorporating thermal differential actuator

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

a wafer substrate defining an inlet channel;

a nozzle chamber wall and a roof wall positioned on the wafer substrate to define a nozzle chamber in fluid communication with the inlet channel, the roof wall defining an ink ejection port in fluid communication with the nozzle chamber;

a paddle positioned in the nozzle chamber and reciprocally displaceable to eject ink from the ejection port; and

an actuating arm extending through the nozzle chamber wall and connected to the paddle, the actuating arm comprising an actuating portion having a pair of actuating members, one of the actuating members including a heating circuit, wherein

on receipt of an electrical signal to the exclusion of the other actuating member, the actuating arm is displaced in a first direction, and further wherein

the actuating arm is comprised of a resiliently flexible material, whereby on cessation of the electrical signal, the actuating arm is displaced in a second direction opposite to the first direction.

2. A nozzle arrangement as claimed in claim 1 , wherein the actuating members are oriented with one actuating member interposed between the substrate and the other actuating member, whereby said reciprocal displacement is with respect to the substrate.

3. A nozzle arrangement as claimed in claim 1 , wherein the actuating members are arranged to define a gap therebetween, whereby buckling of the actuating arm is avoided.

4. A nozzle arrangement as claimed in claim 1 , wherein a raised formation is positioned on an upper surface of the paddle to inhibit the paddle from making contact with a meniscus formed at the ejection port.

5. A nozzle arrangement as claimed in claim 1 , wherein a nozzle rim is positioned about the ejection port.