Coalescence Dynamics of a Droplet Impacting on a Rectangular Pixel for Inkjet Printing

Abstract

A droplet impacting on a rectangular pixel with an offset is prone to cause the liquid to spread out of the pixel and adhere to adjacent pixels in organic light-emitting diode (OLED) inkjet printing. Therefore, the coalescence of a droplet impacting on a rectangular pixel is crucial in understanding the reliable OLED inkjet printing. In this paper, an assumption is established that the rectangular coalescence process is divided into the fusion part and spread part. On this basis, a dynamics model is introduced to analyze the coalescence behavior of a droplet impacting on a rectangular pixel. According to the law of conservation of mass and energy, dynamic equations are developed to obtain the maximum spread length as a function of time. In addition, the volume of the fluid method is used to simulate coalescence dynamics of a droplet impacting on a rectangular pixel by using the software of FLUENT, and the analytical solutions are consistent with the simulation results. Furthermore, the effects of the positioning error and initial velocity on the coalescence dynamics are analyzed. The results show that small initial velocity and positioning error of the droplet are helpful for the reliable OLED inkjet printing.

Double Droplets Impact an Inclined Superhydrophobic Surface

“…Droplet impact is ubiquitous in daily life and industry, − such as raindrops falling on plant leaves, pesticides spraying on crop surfaces, and ink droplets spraying on papers. Once a droplet impacts a solid superhydrophobic surface, it goes through spreading and retracting, then may rebound from the surface if it has enough energy .…”

Three-Dimensional Morphology and Contour Quality of Conductive Lines Printed by High-Viscosity Paste Jetting

“…Due to the extremely small size and high positioning accuracy, the application of inkjet printing technology is showing a rapid growth trend in various fields, such as electronic circuits, metamaterial absorbers, and biological tissues . To ensure the printing accuracy of the manufactured part, the deposition morphology of a single droplet in inkjet printing requires good shape and size uniformity. , Simultaneously, the printed lines formed by the coalescence of multiple droplets must exhibit regularity morphology and excellent contour quality. − The raw materials used in inkjet printing technology have low viscosities that are usually less than 200 mPa·s, with values such as 110.7 mPa·s, 17.2 mPa·s, and 34 mPa·s . The good liquidity makes the jetting process more stable and controllable, leading to good regularity and consistency of the droplets and printed lines …”