Inkjet printhead having convex wall bubble chamber

In an inkjet printhead, a substantially rectangular heater element has a length and width dimension defining an aspect ratio of more than about 2.0. A bubble chamber with a curved or convex wall portion partially surrounds the heater element. A radius of an arc defining the convex wall portion is greater than one-half the width dimension while less than one-half the length dimension and none of the convex wall portion overlies a periphery of the heater element. An ink ejection orifice exists through a thickness of a nozzle plate covering the bubble chamber and resides above the heater element. Additionally, the bubble chamber may have a rectangular wall portion connected to the convex wall portion and either portion may occupy a terminal end of the bubble chamber. Preferred length and width dimensions include 35 and 13 or 40 and 10 microns with a radius of about 16 microns.