Abstract: A MEMS vapour bubble generator that uses a heater in thermal contact with a liquid to generate a bubble. The heater is energized by an electrical pulse that is shaped to have a relatively low power, sub-nucleating portion and a high power portion that nucleates the bubble. The thermal energy transferred to the liquid by the sub-nucleating portion speeds up the nucleation of the bubble across the surface of the heater during the nucleating portion. This produces larger, more stable bubble having a regular shape.

Abstract: An inkjet printhead with an array of nozzles 26 and corresponding heaters 10 configured for heating printing fluid 20 to nucleate a vapor bubble 12 that ejects a drop 24 of the printing fluid through the nozzle. Drive circuitry 22 generates an electrical drive pulse to energize the heaters 10 and is configured to adjust the drive pulse power to vary the vapor bubble nucleation time. By varying the power of the pulse used to generate the bubble, the printhead can operate with small, efficiently generated bubbles during normal printing, or it can briefly operate with large high energy bubbles if it needs to recover decapped nozzles.