Thermal ink jet printhead with symmetric bubble formation

An inkjet printhead nozzle arrangement includes side walls provided on a wafer substrate and a roof layer deposited on said side walls to define an ink chamber, the roof layer defining a nozzle aperture; an inlet defined in the substrate to supply the ink chamber with printing fluid; and at least one heater element having two opposite sides parallel to a plane of the ejection aperture, the heater element adapted to generate a gas bubble at both of said opposite sides. The heater elements and associated electrodes are arranged in the chamber to be non-coincident and have an annular shape facilitating a point of collapse of the bubble near a center thereof. The heater element has a mass of less than 10 nanograms.