Numerical simulation of the physical parameters for stable drop-on-demand inkjet performance

Piezoelectric inkjet (PIJ) printing, an emerging technique in printed electronics, has driven substantial advancements in the fabrication of various functional components. However, achieving jetted droplets with a targeted volume, a stable velocity, and high reliability remains a time-consuming and labor-intensive challenge when utilizing diverse ink types for successful conductive line printing. To address these problems, a computational fluid dynamics (CFD) model was established to analyze how fluid properties affect the mechanism of single droplet formation. Firstly, the entire jetting process was simulated smoothly, encompassing four stages: ejection initiation, outlet pinch-off, front-end pinch-off, and tail breakup. Subsequently, experimental validations were performed on the droplet jetting process, jetting velocity and jetting radius based on the simulated results. Finally, the spreading process of the droplets diameter on poly-ether-ether-ketone (PEEK) substrates was also investigated. Results indicate that the number of satellite droplets can be reduced and the roundness of the droplets can be improved when the ink exhibits a viscosity greater than 5 mPa s, a surface tension less than 30 mN/m and a density greater than 1500 kg/m 3 . The simulations show qualitative agreement with the experimental results, with the maximum relative errors of 10.8 % for jetting velocity and 14.43 % for jetting radius. Additionally, the adhesive force between deposited droplets and the PEEK substrate initially increases by 4.6 % and ultimately increases by 1.3 % with the coated CT-PT layers. These findings offer a deeper and clearer insight into the rapid determination of fluid physical parameters, which is critical for manufacturing high-resolution printed patterns.