Tunable Atomization of Viscous Liquids in the Production of Amorphous Solid Dispersions

Atomization of bulk liquids into droplets underlies several critical properties of amorphous dispersions of pharmaceuticals such as dry particle size, morphology, bulk density, physical stability, and dissolution behavior. Because these properties must often be maintained throughout the life cycle of a compound, a comprehensive understanding and control of atomization is required over a range of process scales. Droplet sizes of low viscosity Newtonian fluids are relatively well predicted by several empirical and semi-empirical correlations in the literature. However, viscous and / or non-Newtonian fluids, such as the polymer-rich solutions used to create amorphous solid dispersions, deviate significantly from these historical correlations. This work will present an atomization model for high viscosity liquids that derives its functional form from first principles of fluid dynamics for a pressure-swirl atomizer. The model is subsequently tuned to match experimental data using a small number of empirically determined free parameters. This methodology allows droplet size to be reliably predicted from controllable process parameters such as atomization nozzle geometry, solution flow rate, and liquid properties.