Ph.D Thesis

Ph.D StudentLink Nitzan
SubjectInvestigating the Motion of Drops Generated by
Piezoelectric Actuators
DepartmentDepartment of Chemical Engineering
Supervisor PROFESSOR EMERITUS Raphael Semiat


The creation of a large image concerns the use of large-scale digital printing machines, which are electronically controlled and computerized. This field has advanced greatly and the improvement of product quality as expressed by the accuracy of the printed image is under constant demand.

Drop-On-Demand piezoelectric actuators are investigated. They eject drops by a pressure wave introduced by piezoelectric crystals. The motion of drops ejected is investigated.

The main goal of this work is to determine the optimized operation conditions of the piezoelectric actuators in order to ensure quality printing.

The investigation of the printing head operation and definition of the phenomena involved in the printing process was achieved by an experimental study that included the use of “Laser Doppler Velocimetry” (LDV) and “Image Velocimetry” (IV) techniques. Drop velocity was measured under different operational conditions and trends were revealed. Furthermore, a range of preferred working conditions was recommended.

The second part of the research deals with the theory of drop formation by a 3D CFD simulation. The calculated results were compared to the experimental and a correlation was found. Furthermore, a comparison was made between two nozzle geometries for different fluid properties.

The third part concerns the relative motion of the printing head and the printing media, and the influence of the airflow caused on the ejected drops. This was achieved using the experimental “Particle Image Velocimetry” (PIV) technique and theoretical simulation. The research concluded that airflow does not interfere with drop path. Possible higher media velocities were demonstrated.