The roles of wettability and surface tension in droplet formation during inkjet printing

TL;DR

This study uses a lattice Boltzmann model to analyze how wettability and surface tension influence droplet formation in inkjet printing, highlighting factors that affect print quality and speed.

Contribution

It introduces a validated binary fluid model with controlled actuation forces to simulate droplet ejection, emphasizing the roles of wettability and surface tension.

Findings

Higher contact angles delay droplet breakup and reduce velocity.

Increased surface tension promotes earlier breakup and faster droplets.

Hydrophilic nozzle modifications and high surface tension inks improve print quality.

Abstract

This paper describes a lattice Boltzmann-based binary fluid model for inkjet printing. In this model, a time-dependent driving force is applied to actuate the droplet ejection. As a result, the actuation can be accurately controlled by adjusting the intensity and duration of the positive and negative forces, as well as the idle time. The present model was verified by reproducing the actual single droplet ejection process captured by fast imaging. This model was subsequently used to investigate droplet formation in piezoelectric inkjet printing. It was determined that wettability of the nozzle inner wall and the surface tension of the ink are vital factors controlling the print quality and speed. Increasing the contact angle of the nozzle inner delays the droplet breakup time and reduces the droplet velocity. In contrast, higher surface tension values promote earlier droplet breakup and faster drop velocity. These results indicate that the hydrophilic modification of the nozzle inner wall and the choice of inks with high surface tensions will improve printing quality.