Transport of ellipsoid fibers in oscillatory shear flows:Implications for aerosol deposition in deep airways

摘要

It is widely acknowledged that inhaled fibers, e.g. air pollutants and anthropogenic particulate matter, hold the ability to deposit deep into the lungs reaching the distal pulmonary acinar airways as a result of their aerodynamic properties; these particles tend to align with the flow and thus stay longer airborne relative to their spherical counterpart, due to higher drag forces that resist sedimentation. Together with a high surface-to-volume ratio, such characteristics may render non-spherical particles, and fibers in particular, potentially attractive airborne carriers for drug delivery. Until present, however, our understanding of the dynamics of inhaled aerosols in the distal regions of the lungs has been mostly limited to spherical particles. In an effort to unravel the fate of non-spherical aerosols in the pulmonary depths, we explore through numerical simulations the kinematics of ellipsoid-shaped fibers in a toy model of a straight pipe as a first step towards understanding particle dynamics in more intricate acinar geometries. Transient translational and rotational motions of micronsized ellipsoid particles are simulated as a function of aspect ratio (AR) for laminar oscillatory shear flows mimicking various inhalation maneuvers under the influence of aerodynamic (i.e. drag andlift) and gravitational forces. We quantify transport and deposition metrics forsuch fibers, including residence time and penetration depth, compared withspherical particles of equivalent mass. Our findings underscore how depositiondepth is largely independent of AR under oscillatory conditions, in contrastwith previous works where AR was found to influence deposition depth understeady inspiratory flow. Overall, our efforts underline the importance ofmodeling oscillatory breathing when predicting fiber deposition in the distallungs, as they are inhaled and exhaled during a full inspiratory cycle. Suchphysical insight helps further explore the potential of fiber particles asattractive carriers for deep airway targeting.