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Acoustical and optical characterization of air entrapment in piezo-driven inkjet printheads

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  • Musicology
  • Physics


Title Acoustical and Optical Characterization of Air Entrapment in Piezo-Driven Inkjet Printheads J. de Jong, M. Versluis, G. de Bruin, D. Lohse Faculty of Science and Technology University of Twente Enschede, The Netherlands Email: [email protected] H. Reinten, M. van den Berg, H. Wijshoff Oce´ Technologies B.V., Venlo, The Netherlands N. de Jong Exp. Echocardiography Thoraxcentre, Erasmus MC, Rotterdam, The Netherlands Abstract— Air bubbles can cause nozzle failures in piezo-driven inkjet printheads [1]. The time development of the entrapped air bubbles has experimentally been studied [2]. It was found that the air bubble has a radius of 5µm just after the entrapment. The bubble then grows by rectified diffusion due to the applied pressure field, used for jetting droplets. Bjerknes forces drive the displacement of the air bubble. First, the bubble is pushed into the channel. After reaching the resonance size, given by the characteristic printhead frequency, the Bjerknes force reverses sign, pushing the air bubble towards the nozzle. At this time the air bubble has grown so large that it is not possible to jet it out, resulting in a nozzle failure. I. INTRODUCTION Air entrapment leads to malfunctioning of jet formation in a piezo-driven inkjet printhead. The entrapped air bubbles disturb the acoustics and in many cases cause the droplet formation to stop [1]. The nozzle diameter is 30µm or less. Droplets are jetted every 50µs and it is essential that the droplet formation remains stable for an extensive period. Though the droplet forming process is very stable for literally millions of droplets, from one to the next actuation cycle there may be an occurrence giving rise to a malfunctioning of the droplet formation. The time development of the entrapped air bubbles has experimentally been studied [2]. II. METHODS The acoustical signal is monitored by using the piezo actuator as a sensor to measure the pressure in the channel after the pulse is applied [1]. This

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