Patent ID: 6877842

Claim:
A bubble-jet inkjet printhead, comprising: a substrate having a hemispherical ink chamber formed therein to hold ink supplied from a manifold; a nozzle plate supported by said substrate and perforated by a nozzle through which said ink is ejected, said nozzle having a central axis that coincides with a central axis of said hemispherical ink chamber; a heating element having an inner edge and an outer edge, said inner edge of said heating element surrounding said nozzle, said heating element having a plurality of high resistance portions and a plurality of low resistance portions, wherein said low resistance portions and high resistance portions are positioned alternately along a circumference of said heating element; and a pair of electrodes electrically connected to said heating element to apply current to said heating element when electricity is applied to said pair of electrodes, wherein said inner edge of said heating element has an essentially circular shape, said outer edge of said heating element has a polygonal shape and, said heating element is continuous and closed.