Effect of carrier size and mechanical properties on adhesive unit stability for inhalation: A numerical study

The Discrete Element Method (DEM) was used to investigate the micromechanics of adhesive units, the building blocks of adhesive mixtures, comprising a carrier particle with attached micronised fine particles. Binary head-on collisions between adhesive units was performed in the handling and dispersion velocity regimes, with variations in carrier mechanical properties (mannitol or lactose) and size (50, 100, 200 μm). The system was modeled with spherical particles with interactions represented by Hertz-Mindlin and Johnson-Kendall-Roberts contact models. The results were analysed in terms of stability ratios (retention, loss and transfer) and mechanical properties (restitution coefficient). It was observed that mannitol particles are more stable than lactose with similar dispersion performance and that the 200 μm carrier is the most stable among the particles investigated. The results provide a parametric knowledge about the performance of carrier particles and could be used for development of macro models for particle engineering and optimization of formulations.