Patent ID: 7520594

Claim:
An inkjet printer comprising: a plurality of nozzles, each nozzle having a nozzle aperture; a chamber corresponding to each of the nozzles respectively; a heater corresponding to each of the nozzles respectively, the heater having a heater element and a pair of electrodes, the heater element being disposed in the bubble forming chamber for heating a printing fluid to form a gas bubble that causes the ejection of a drop of the printing fluid through the nozzle corresponding to that heater element; wherein, the heater element has a double omega shape with a first omega shape extending between the pair of electrodes positioned adjacent each other in a side wall of the bubble forming chamber, the pair of electrodes being separated by a first gap, and a second omega shape is inverted relative to the first and extending between a second gap in the first omega shape, the second gap in the first omega being positioned diametrically opposite the gap between the pair of electrodes, such that the heater element generates the gas bubble substantially symmetrically about an axis extending normal to the plane of the nozzle aperture.