Study of micro-droplet behavior for a piezoelectric inkjet printing device using a single pulse voltage pattern

Abstract

The aim of this study is to investigate the formation and ejection behavior of droplets created by a squeeze mode piezoelectric inkjet printing device using a single pulse voltage pattern. The test liquids are de-ionized (DI) water and ethylene glycol. The experimental results and acoustic wave theory are used to discuss the effects of operating frequency, positive voltage keeping time and pulse voltage magnitude on the volume and velocity of the droplets. For this study, a squeeze mode piezoelectric printhead is employed. By coordinating an LED flash with droplet ejection, a CCD camera could be used to capture images of the droplets at different points in the formation and ejection process. These images were then used to estimate the volume and velocity of the droplets. The experimental results are consistent with the propagation theory of acoustic waves. The maximum allowable pulse frequency in DI water and ethylene glycol are 1500 Hz and 14000 Hz respectively. If the positive voltage keeping time equals the time required for the acoustic wave to propagate through the printhead, optimal ejection behavior is achieved. As the pulse voltage increases, both the velocity and volume of the droplet become larger.