MODELING AND EXPERIMENTAL VALIDATION OF DROPLET GENERATION IN ELECTROHYDRODYNAMIC INKJET PRINTING FOR PREDICTION OF PRINTING QUALITY

摘要

Electrohydrodynamic (EHD) Inkjet printing is one type of micro/nano scale additive manufacturing technique. The droplet generation mechanism plays an important role in electrohydrodynamic (EHD) inkjet printing due to its significant effects on process control, printing quality, and printing performance. The large variation of printing system design used in EHD printing and the limited process optimization techniques resulted in a complex experimental procedure to determine a working condition, and it takes a long time to finish such experiments. It is also challenging to understand the droplet generation mechanism's fluid dynamics under a multiphysical field in EHD printing. The development of computational fluid dynamics (CFD) and the recent advancements in high performance computing can be utilized to alleviate the aforementioned challenges. In this study, a numerical simulation model was developed to model the droplet generation mechanism in EHD printing based on Taylor-Melchar leaky-dielectric model. This model successfully simulated a single printing cycle, including Taylor cone formation, cone-jet generation, jet break, and jet retraction. A further simulation study demonstrated accurate predictions of the droplet volume and the jetting diameter under different working conditions (e.g., voltages and duty ratio of pulsed AC voltage). Experiments validated the simulation model and its prediction results. Such advancement in modeling can be used to optimize the printing process as well as guide the quick selection of printing conditions given a new ink.