An ink jet printhead includes a plurality of nozzles each having a nozzle aperture; a plurality of bubble forming chambers, each corresponding respectively to one of the plurality of nozzles; an inlet for communicating printing fluid between the nozzle aperture and a printing fluid supply, the inlet and the nozzle aperture being aligned along a common central axis; and a heater element disposed in each of the bubble forming chambers. Each heater element has two bubble nucleation regions suspended within the bubble forming chamber in a plane parallel to that of the nozzle aperture. The two bubble nucleation regions are laterally offset from the central axis, such that the lateral offset of one of the bubble nucleation regions is equal and opposite to the lateral offset of the other bubble nucleation region. The bubble nucleation regions are spaced from each other such that bubbles nucleated at each will grow until they unite to form the gas bubble that causes the ejection of a drop of ejectable liquid.