A printhead for an inkjet printer comprises a wafer assembly defining a plurality of spaced apart groups of ink supply channels and a plurality of groups of ink ejection nozzle arrangements. Each ink ejection nozzle arrangement comprises a nozzle chamber structure mounted to the wafer assembly. Each ink ejection nozzle arrangement further comprises an anchor extending from the wafer assembly in a location external to the nozzle chamber; and an elongate thermal actuator mechanism extending from the anchor and into the nozzle chamber. The thermal actuator mechanism comprises an elongate arm which terminates in a free end within the nozzle chamber, and a pair of layers of conductive material located on either side of the elongate arm. One of the layers is connected to a current supply for causing a differential thermal expansion in the elongate thermal actuator mechanism. A pit is defined adjacent each nozzle chamber structure for catching ink. The ink ejection nozzle arrangements of each group are arranged in a pair of rows, with the elongate thermal actuator mechanism of ink ejection nozzle arrangements of a first row extending away from those of ink ejection nozzle arrangements of a second row.
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