Provided is a nozzle arrangement for an inkjet printhead. The nozzle arrangement includes a substrate defining an ink inlet, a roof portion defining an ejection port, the roof portion supported on said substrate by posts, and an actuator arranged between the posts and having four iris vanes each respectively arranged to form a wall of a chamber, said iris vanes operating in an iris-type manner to reduce a volume of the chamber to eject ink from the chamber via the ejection port.