Patent ID: 7771027

Claim:
An inkjet printhead having a high density array of micro-electromechanical nozzles arrangements, each arrangement comprising: side walls located on a wafer substrate with a roof layer deposited on said walls to define an ink chamber, the roof layer defining a nozzle aperture; an inlet defined in the substrate to supply the ink chamber with printing fluid; and at least one heater element having a mass of less than 250 picograms suspended between the side walls in the chamber, the heater element operable to form a vapour bubble when electrical actuation energy of less than 120 nanojoules is applied thereto, said heater element having an annular shape with a point of collapse of the bubble near a centre thereof, wherein said inlet, heater element and nozzle aperture are configured such that substantially all heat generated in the ink chamber by the heater element per actuation is negated between actuations by an intake of unheated ink into the ink chamber through the inlet and an expulsion of heated ink from the ink chamber through the nozzle aperture.