An ink drop ejection device with a bubble forming chamber for holding an ejectable liquid, a nozzle in fluid communication with the bubble forming chamber, and at least one heater element in the bubble forming chamber for thermal contact with the bubble forming liquid. Heating the heater element to a temperature above the boiling point of the bubble forming liquid forms a gas bubble to eject a drop of the ejectable liquid through the nozzle. The bubble forming chamber has a circular cross section and the heater element has arcuate sections that are concentric with the circular cross section.