Investigation on Microparticle Transport and Deposition Mechanics in Rhythmically Expanding Alveolar Chip

Abstract

: The transport and deposition of micro/nanoparticles in the lungs under respiration has an important impact on human health. Here, we presented a real-scale alveolar chip with movable alveolar walls based on the microfluidics to experimentally study particle transport in human lung alveoli under rhythmical respiratory. A new method of mixing particles in aqueous solution, instead of air, was proposed for visualization of particle transport in the alveoli. Our novel design can track the particle trajectories under different force conditions for multiple periods. The method proposed in this study gives us better resolution and clearer images without losing any details when mapping the particle velocities. More detailed particle trajectories under multiple forces with different directions in an alveolus are presented. The effects of flow patterns, drag force, gravity and gravity directions are evaluated. By tracing the particle trajectories in the alveoli, we find that the drag force contributes to the reversible motion of particles. However, compared to drag force, the gravity is the decisive factor for particle deposition in the alveoli.

Microparticle Transport and Sedimentation in a Rhythmically Expanding Alveolar Chip

“…There were two kinds of experimental platform because of the different ways of placing the alveolar chip. When the alveolar chip was placed horizontally, the high-speed camera was mounted on the microscope (IX73, Olympus, Tokyo, Japan), as shown in Figure 1 C. When the chip was placed vertically, the high-speed camera was fixed on a small anti-vibration platform, and the chip was fixed on the displacement platform ( Figure 1 D), which was similar to the previous published work [ 31 ]. Image-pro plus 6.0 was used for particle tracking in image post-processing.…”

“…However, we also observed that most particles directly settled to the bottom of the alveolus at the last several generations from the 21st generation. We could also find some hints of the irreversibility and gravity effect on the particle transport and deposition from the studies performed by Fishler et al [ 22 ] and Dong et al [ 31 ], showing the trajectory within a limited number of cycles.…”

“…The alveolar chip was mainly composed of a cuboid alveolar duct with a square cross-section (240 μm in side length) lined with a cylindrical alveolus (225 μm in diameter) and a pressure chamber with a rectangular cross-section, and the thickness of the alveolar ductal wall was 90 μm (see Figure 1 A). The alveolar chip had a quasi-three-dimensional structure, similar to in previous research work [ 28 , 31 ].…”

“…The Gravity number characterizes the gravitational sedimentation when particles transport in the fluid. The particle Peclet number characterizes the ratio of the effect of convection to diffusion on particle transport in the fluid [ 11 , 31 ]. Stk , H , and Pe p can be defined as where g is the gravitational acceleration, k B is Boltzmann’s constant, and ; T em is the temperature in Kelvin, and C c is the Cunningham slip correction factor; when , considering , where is the mean free path of molecules in the fluid.…”

“…Understanding the intricate behavior of microparticle transport in the chaotic flow of the alveoli is of great significance [ 29 , 30 ]. Dong et al [ 31 ] revealed the trajectories of silver particles mixed in the glycerol/water solution in the alveoli under gravity with different directions. However, the particles were tracked for only a few breathing cycles, and it is difficult to discover the characteristics of particle transport and deposition in the alveoli.…”