A unit cell of a printhead is provided having a multi-layer substrate defining an ink inlet, one or more side walls extending from the substrate around the ink inlet, a nozzle plate supported by the side walls to define a chamber in fluid communication with the ink inlet, where the nozzle plate defines an aperture through which ink in the chamber can be ejected, and a looped and elongate heater element suspended within the chamber, which can be heated so that bubbles are generated in ink within the chamber and ink is ejected from the aperture. The nozzle plate defines a protruding rim bounding the aperture.