(489b) CFD Investigation of Nozzle Configuration and Interface Tension Effects on Core-Shell Droplet Formation in Coaxial Electrohydrodynamic Atomization Process

Core-shell microspheres have shown particular advantages in drug delivery application as drug carriers, such as preventing burst release of drug, improving drug stability and achieving synergistic therapeutic effects. Coaxial electrohydrodynamic atomization (CEHDA) is an emerging technique having several advantages in fabrication of core-shell micropaticles, such as uniform size distribution, effective protection of bioactivity and high encapsulation efficiency. However, the complex physics behind the process is still one of the challenges in the development of CEHDA. In addition, the productivity is limited by the flow rate especially for fine particles production. In order to better design the microparticle structure, improve the productivity of CEHDA process and further facilitate the scale-up of the fabrication process to industry, a computational fluid dynamic (CFD) model was developed to simulate and provide a better understanding of the CEHDA process. A volume of fluid model (VOF) was employed to simulate the liquid cone-jet mode and droplet formation. The electric body forces were included into the Navies-Stokes equations using user-defined function (UDF). The effects of nozzle configurations on the cone-jet formation and droplet formation which had not been systematically studied in literatures were investigated.. Furthermore, the effects of interface tension between core and shell fluids were investigated. The results showed that the configurations of nozzle tip have significant effect on the droplet production. Possible mechanisms were proposed to illustrate the differences of core-shell droplet formations with various nozzle configurations. The results also showed that using specific nozzle configuration, the limitation of flow rate on the productivity can be further overcome for the production of micro-/nano- particles.