Patent ID: 7712884

Claim:
An inkjet printhead comprising: a wafer substrate defining a planar support surface; an array of nozzles adjacent the planar support surface of the wafer substrate, the array having corresponding thermal actuators for ejecting ink through the nozzles, the nozzles being arranged in rows such that the nozzle centres are collinear and the nozzle pitch along each row is greater than 1000 nozzles per inch; a plurality of ink chambers defined by sidewalls extending between a nozzle plate and the underlying wafer substrate, one of the sidewalls of each chamber having an opening to allow ink to refill the chamber, each of the ink chambers housing one of the thermal actuators respectively; an ink conduit between the nozzle plate and underlying wafer, the ink conduit being in fluid communication with the openings of a plurality of the ink chambers; a plurality of ink inlets defined in the wafer substrate, each of the ink conduits being in fluid communication with at least one of the ink inlets for receiving ink to supply to the ink chambers, each of the ink inlets having an ink permeable trap and a vent sized so that the surface tension of an ink meniscus across the vent prevents ink leakage; wherein during use, the ink permeable trap directs gas bubbles to the vent where the gas bubbles vent to atmosphere; drive circuitry for providing the thermal actuators with electrical pulses for actuation, the drive circuitry being complementary metal oxide semiconductor (CMOS) circuitry formed on the planar support surface by a plurality of patterned metal layers interleaved with dielectric layers, the CMOS circuitry having an outer metal layer furthest from the planar support surface which defines a plurality of electrodes arranged in pairs; and, a trench etched into the drive circuitry extending between the electrodes; wherein, the thermal actuators each have a heater element extending between two contacts, the contacts each overlaying and directly contacting one of the electrodes respectively such that the heater elements are each powered by one of the pairs of electrodes respectively, the heater element being suspended over the trench and the thermal actuator being a unitary planar structure.