Patent ID: 7182439

Claim:
An ink jet printhead comprising: a plurality of nozzles, each defining a nozzle aperture with a nozzle axis extending through the center of the nozzle aperture and normal to the nozzle aperture; a bubble forming chamber corresponding to each of the nozzles respectively configured to receive a supply of an ejectable liquid at an ambient temperature; at least one heater element disposed in each of the bubble forming chambers respectively, the heater element configured for heating the heater element to a temperature above the boiling point of the bubble forming liquid to form a gas bubble that ejects a drop of the ejectable liquid through the nozzle corresponding to that heater element; wherein, the gas bubble collapses to a collapse point spaced from the heater element, and the heater element has two planes of symmetry intersecting along the nozzle axis such that the energy required to heat the heater element to form the gas bubble is less than the energy required to heat a volume of the ejectable liquid equal to the volume of the drop, from a temperature equal to the ambient temperature to the boiling point.