Significance: It is always a challenge to see the deposition of single PM _2.5 particles, the harmful inhalable aerosols in the polluted air, in alveolar region, and their invasion to the extrapulmonary organs. The dynamic deposition process and the nonuniform deposition pattern of PM _2.5 in the alveolar region are revealed using a fluorescent imaging method with high temporal and spatial resolutions. This observation technology would also bring insight in the study of the public health in air pollution and lung administration.

We demonstrate a microfluidic method to first generate double emulsion droplets containing two different inner drops, and to then control the internal coalescence of the encapsulated drops. The advantages of the core-coalescence method are illustrated by fabricating high viscosity particles and by demonstrating the dissolution of cell membranes.

We report the controlled breakup of double emulsion droplets as they flow through an orifice of a tapered nozzle. The results are summarized in a phase diagram in terms of the droplet-to-orifice diameter ratio and the capillary number. We identify a flow regime where the inner aqueous phase is released.

A discrete probability distribution function is used to represent the squared transverse roughness effect in a modified Reynolds equation, and the Reynolds equation is used to calculate the hydrodynamic lubrication in a slider-disk interface compared to the CFD method. When the roughness height is below 1% of the film thickness, the results acquired by the two methods are the same and the surface roughness does not show obvious effect on the lubrication results compared to that on the smooth surface. The load capacity and friction force increase as the roughness height increases when the roughness height exceeds 1% of the film thickness. Moreover, the forces acquired by Reynolds equations are smaller than those acquired by CFD, and the difference between them exceeds 10% when the roughness height is higher than 10% of the film thickness. Sidewall effect is considered to be the main reason for the difference, and the Reynolds equation is believed not suitable for calculating the effect of the squared transverse roughness in the hydrodynamic lubrication.

Hemolysis usually happens instantly when red blood cells (RBCs) rupture under a high shear stress. However, it is also found to happen gradually in the extracorporeal membrane oxygenation (ECMO) under low but periodic squeezes. In particular, the gradual hemolysis is accompanied by a progressive change in morphology of RBCs. In this work, the gradual hemolysis is studied in a microfluidic device with arrays of narrow gaps the same as the constructions in ECMO. RBCs are seen to deform periodically when they flow through the narrow gaps, which causes the release of adenosine-triphosphate (ATP) from RBCs. The reduced ATP level in the cells leads to the fatigue of RBCs with the progressive changes in morphology and the gradual loss of deformability. An empirical model for the fatigue of RBCs is established under the periodic squeezes with controlled deformation, and it reveals a different way of the hemolysis that is dominated by the squeeze frequency. This finding brings a new insight into the mechanism of hemolysis, and it helps to improve the design of circulatory support devices.