Methods for detecting air bubble in piezo inkjet dispensers

Two different measurement techniques, piezo self-sensing signals and meniscus motion, are proposed to monitor inkjet operating conditions and detect possible causes of piezo inkjet malfunction. Both measured signals are related to the pressure wave in the ink, which causes the ink jetting. The experimental results demonstrate that air bubbles entrapped in the piezo inkjet dispenser, which is one of the major problems in inkjet printing, can be effectively detected during the piezo actuation by using the proposed schemes. Finally, the drawbacks and merits of the proposed methods will be discussed.