A. James Clark School of Engineering

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Author: search.filters.author.Wang, Yiyang

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    Capsule Migration and Deformation in a Converging Micro-Capillary
    (MDPI, 2021-03-03) Wang, Yiyang; Dimitrakopoulos, Panagiotis
    The lateral migration of elastic capsules towards a microchannel centerline plays a major role in industrial and physiological processes. Via our computational investigation, we show that a constriction connecting two straight microchannels facilitates the lateral capsule migration considerably, which is relatively slow in straight channels. Our work reveals that the significant cross-streamline migration inside the constriction is dominated by the strong hydrodynamic forces due to the capsule size. However, in the downstream straight channel, the increased interfacial deformation at higher capillary numbers or a lower viscosity ratio and lower membrane hardness results in increased lateral cross-streamline migration. Thus, our work highlights the different migration mechanisms occurring over curved and straight streamlines.
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    Lateral Capsule Migration in Microfluidic Channels
    (2017) Wang, Yiyang; Dimitrakopoulos, Panagiotis; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A capsule motion inside a microfluidic channel has attracted a lot of attention in recent decades owing to its important applications in industrial, pharmaceutical and physiological systems such as in cell sorting, targeted drug delivery and blood flow. In this dissertation, we computationally investigate an elastic capsule's lateral migration inside a constricted microfluidic device under Stokes flow conditions. We use the Membrane Spectral Boundary Element (MSBE) method to determine the capsule dynamics due to its high computational accuracy and versatility in dealing with complex solid geometries. In the bounded Poiseuille flow of the microfluidic constriction, a capsule, placed initially off-centered will migrate away from the wall and move toward the channel centerline. The capsule's lateral migration behavior is caused by the combination of the wall effects due to the existence of the channel boundary, the shear gradient generated by the non-linear velocity distribution of the flow, and the lift force created by the capsule deformation. We use a constricted device instead of a straight channel to do the simulations, because the capsule's lateral migration in a straight channel is too slow to be observed easily, while the existence of the converging connection of the constricted device increases the capsule's lateral velocity and thus facilitates its migration. The main goal of our research is to investigate the effects of the capsule's physical properties on its lateral migration behavior. We released various deformable capsules at different initial positions, membrane hardness, viscosity ratios, and capsule volumes inside the constricted channel and computed their deformation behavior and migration trajectories. Our results show that changing a capsule's viscosity ratio or the membrane hardness does not strongly affect the capsule's lateral migration due to the capsule's weak inner circulation. On the other hand, changing the capsule's initial position and capsule volume strongly affect its migration trajectories. Thus soft particles with different sizes can be separated and identified.