Charged Particle Dynamics in Dry Powder Inhalers.

Mechanisms for the growth of particles in a stream of aerosolised inhalation powders have been investigated computationally using experimentally measured stream compositions. Many-body electrostatic theory has been incorporated into classical particle dynamics simulations to describe the aggregation of charged, fine powder particles in the single and dual stream geometry of an inhaler. The simulations use experimental bipolar charge measurements recorded using a Dekati BOLAR as input. Evidence of a subtle relationship between charge and the dynamics of particle growth contributes to our understanding of the electrostatics and many-body interactions in inhalation powders. It is found that certain combinations of particle size and charge result in a scavenging process whereby small particles, which may be therapeutic, aggregate with large particles to become ineffective due to an overall increase in size. This process may have important implications for design of dry powder inhaler devices.