| dc.description.abstract | In the literatures many exposure systems were proposed to study inhalation toxicology, however, the particle deposition flux or the exposed dose had not been well defined in these exposure systems. Moreover, Particle trajectory and deposition were highly depending on operation conditions. Therefore, in this study, we developed a new ESP type air-liquid interface (ALI) cell exposure system and numerically characterized its performance. The commercial CFD software, COMSOL Multiphysics, was coupling the fluid field and the electric field to simulate dynamic trajectory of charged particles in the system and to determine the particle deposition flux. The aim of this study was to establish a numerical simulation scheme to design and to develop an ESP type ALI system. Based on the numerical simulation it was found decreasing expanded degree of the upper exposure chamber would reduce reflux and mitigate unwanted particle loss. Therefore, the new configuration of the exposure chamber was re-designed by considering smoother streamline and particle trajectory to reduce unnecessary spaces and particle loss. The original design, Model A, needs 6 kV to achieve 100% collection of 100 nm particles, but the revised design, Model B, only requires 1 kV. In other words, Model B is more effective than Model A on particle collection.
To further systematically evaluate the performance of the system, three indicators, including total penetration (P), region deposition ratio (f) and relative deposition density in region 2, were introduced. Higher flow rate would case lower total penetration because of more significant re-circulated flow. Although in 0 kV the region deposition ratio was not obviously changing with particle size, the size effect was not negligible when applying voltage. In addition, the applied electric field would increase particle deposition in region 2 and result in more uniform particle depositasion pattern. | en_US |