Tracking the transport of inhaled particles in a lung-on-a-chip during breathing cycles

Abstract

Understanding the transport behavior of micron-sized particles in the respiratory zone is crucial for assessing health effects of inhaled aerosols, including environmental pollutants and therapeutic drugs. However, experimentally capturing the detailed trajectories of aerosol particles entering the alveoli and understanding the underlying mechanisms of particle transport remain to be further studied. This study experimentally and numerically investigated the detailed trajectories of microparticles transported by alveolar airflows across a range of Reynolds number (Re) conditions. These trajectories clearly illustrate how particles enter and become trapped in the alveoli during both inhalation and exhalation. This study also highlights the critical influence of flow Re, particle diameter, and initial particle position on particle transport behavior. At higher Re, flows tend to drive particles, those near the duct wall, deep towards the alveolar center in spiral paths. Smaller particles (< 1.5 µm) exhibit prolonged suspension, enabling deeper lung penetration. Moreover, in the low-Re alveolar region, particles initially positioned close to the alveoli have an advantage in entering the alveoli and being trapped. This research offers valuable data for improving our understanding of particle transport behavior within the alveolar region, and has potential implications for drug delivery applications.