(230c) Particle Scale Study of the Dispersion of Dry Powder In Pharmaceutical Aerosol Inhalers
Inhalation aerosols offers a simple and useful technique for efficient drug delivery Current designs of dry powder inhalers (DPIs) are rather poor in performance due to the strong cohesion between pharmaceutical particles which are usually less than 5 micron and hence are difficult to disperse. Dispersion of dry powder in an inhaler is a dynamic process which involves multiple physical factors due to particle-device interaction as well as particle-particle and particle-fluid interactions. To understand the dispersion mechanisms, microscopic information at a particle scale is required. Here we present a numerical study of powder dispersion by combining computational fluid dynamics (CFD) for gas phase and discrete element method (DEM) for particle phase. A series of simulations were performed to quantify the roles of different interactions in powder dispersion. The results indicated that the dispersion is mainly governed by particle–particle cohesion (agglomerate strength) and particle–device impaction, while the particle-particle impaction plays a secondary role. On the other hand, the dispersion caused by the internal shearing induced by air flow is small and the increase in flow rate mainly increases the kinetic energy of agglomerates which may lead to stronger particle-device and particle-particle interactions. By analyzing the various types of energy in dispersion, we correlated the dispersion efficiency with the ratio of the impact energy (particle-device and particle-particle) and agglomerate strength. Simulations were also extended to the dispersion in a commercial inhaler, where the fundamental findings were used to understand the complicated dispersion process involving all kinds of interactions.