Bulletin of the American Physical Society
72nd Annual Meeting of the APS Division of Fluid Dynamics
Volume 64, Number 13
Saturday–Tuesday, November 23–26, 2019; Seattle, Washington
Session A32: Biological Fluid Dynamics: Single Cells and Bacteria I |
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Chair: Maziyar Jalaal, DAMTP, University of Cambridge Room: 614 |
Saturday, November 23, 2019 3:00PM - 3:13PM |
A32.00001: Boundary integral simulations of a red blood cell squeezing through a submicron slit under prescribed inlet and outlet pressures Zhangli Peng, Huijie Lu, Alexis Moreau, Emmanuele Helfer, Anne Charrier, Annie Viallat We developed a boundary integral formulation to simulate a red blood cell (RBC) squeezing through a submicron slit under prescribed inlet and outlet pressures. The main application of this computational study is to investigate splenic filtrations of RBCs and the corresponding in vitro mimicking microfluidic devices, during which RBCs regularly pass through inter-endothelial slits with a width less than 1.0 micrometer. The diseased and old RBCs are damaged or destroyed in this mechanical filtration process. We first derived the boundary integral equations of a RBC immersed in a confined domain with prescribed inlet and outlet pressures. A multiscale model is applied to calculate forces from the RBC membrane, and it is coupled to boundary integral equations to simulate the fluid-structure interaction. After multi-step verifications and validations against analytical and experimental results, we systematically investigated the effects of pressure drop, volume-to-surface-area ratio, internal viscosity, and membrane stiffness on RBC deformation and internal stress. We found that spectrins of RBCs could be stretched by more than 2.5 times under high hydrodynamic pressure and that the bilayer tension could be more than 500 pN/um, which might be large enough to open mechanosensitive channels but too small to rupture the bilayer. On the other hand, we found that the bilayer-cytoskeletal dissociation stress is too low to induce bilayer vesiculation. [Preview Abstract] |
Saturday, November 23, 2019 3:13PM - 3:26PM |
A32.00002: Fluid-Structure Interaction of Bioluminescence Maziyar Jalaal, Nico Schramma, Raymond Goldstein Bioluminescence (emission of light from living organisms) is a common form of communication in the ocean. Here we study the bioluminescence on a single-cell level, aiming to understand the response to mechanical stimulation. In our experiments, the cell (an alga) was immobilised via micro-pipette aspiration. We impose pressure on the cell, via a submerged impinging jet. We show that the flow-induced stress on the cell membrane results in a local elastic deformation. As a result, a series of chemical signaling events occur that eventually yields to light production in sub-cellular compartments. Besides experiments, we propose a counterpart model. [Preview Abstract] |
Saturday, November 23, 2019 3:26PM - 3:39PM |
A32.00003: Flow-Induced Deformation of Cells During Small Opening Traversal Igor V. Pivkin We performed experimental and computational study of cells in microfluidic devices measuring cell traversal through the series of openings of various sizes. MCF-10A, MCF-7 and MDA-MB-231 cells were used in experiments and corresponding computational models were developed using particle-based approach. Deformability of cells under the flow conditions will be discussed. This work was done in collaboration with the group of Chwee Teck Lim from National University of Singapore. [Preview Abstract] |
Saturday, November 23, 2019 3:39PM - 3:52PM |
A32.00004: Deformation and viability of an encapsulated cell through a microfluidic contraction Mohammad Nooranidoost, Ranganathan Kumar Deformation and viability of an encapsulated cell moving through a sudden contraction in a capillary tube is studied using a front-tracking method. A cell-laden droplet is initiated in a capillary tube which is allowed to migrate with the flow. When it moves through a sudden contraction, high shear stresses are experienced around the droplet where the velocity is maximum. The interplay between these stresses and interfacial forces, as well as the geometrical constraint squeezes the droplet resulting in the deformation of the inner cell. A cell viability model is used to relate the cell deformation to cell viability. Deformation and viability of the cell are highly dependent on encapsulating droplet properties and the geometry of the contraction. For a fixed geometry of the contraction, viscosity and size of the encapsulating droplet can be adjusted to minimize cell deformation. Increasing droplet size for low viscosity of the droplet shell helps reduce the deformation and maintain the viability of the cells. The deformation is enhanced for capillary tubes with narrow and long contractions, which leads to a lower cell viability. This study can be useful in biomedical applications to improve viability of cells migrating in channels with sudden obstacles. [Preview Abstract] |
Saturday, November 23, 2019 3:52PM - 4:05PM |
A32.00005: Effect of constitutive laws on erythrocyte membrane response Marianna Pepona, John Gounley, Amanda Randles Despite the extensive literature on the modelling of red blood cells, only a few works have compared the response of a deforming red blood cell to different constitutive laws. In the current work, three different constitutive equations are considered: the strain-hardening Skalak’s law, the strain-softening neo-Hookean model, and Yeoh’s law, whose nature and degree of strain-hardening/softening depend on the deformation regime and type. The performance of these laws is assessed on accurately capturing deformations in the longitudinal and transverse directions, and under shear via optical tweezers, micropipette aspiration and “wheel” numerical experiments, respectively. Particular emphasis is given to the nonlinear deformation regime, i.e. moderate and large deformations, where it is known that the discrepancies between various constitutive laws are most prominent. Finally, we compare the aforementioned laws in the configuration of a single red blood cell flowing inside a capillary. This work aims at providing criteria for selecting the constitutive law best describing the erythrocyte membrane mechanics for the deformation type and regime of interest. [Preview Abstract] |
Saturday, November 23, 2019 4:05PM - 4:18PM |
A32.00006: Shake, rattle, and roll: microstreaming flows from acoustically oscillating cells Scott Tsai, Alinaghi Salari, Sila Appak-Baskoy, Michael Kolios Steady-state microstreaming flows can arise from the interaction of sound waves with elastic objects, such as bubbles. Such microstreaming finds utility in cell and particle manipulation, and in microfluidic pumping and analyte mixing. Here, we describe a new observation that in vitro single cells that are excited by a controlled acoustic wave are also able to generate microstreaming flows. Specifically, adherent cells under the influence of a surface acoustic wave oscillate inside a microfluidic channel to generate microstreaming flows. We study the cellular properties that affect the degree of microstreaming by, for example, imposing an osmotic shock to the cell, manipulating the cell structure enzymatically using trypsin, and chemically, using paraformaldehyde and Cytochalasin D. Our findings suggest that the microstreaming induced by MDA-MB-231 cells is primarily controlled by the overall cell stiffness. We thus conclude that measuring the resulting flow pattern and velocity magnitude may be utilized as a label-free proxy for quantifying the mechanical properties, such as stiffness, of the cell. [Preview Abstract] |
Saturday, November 23, 2019 4:18PM - 4:31PM |
A32.00007: A Microfluidic Platform for the Study of Cell Deformability Amir Saadat, Diego A. Huyke, Ingrid H. Ovreeide, Diego I. Oyarzun, Paulina V. Escobar, Juan G. Santiago, Eric S. G. Shaqfeh Reduced deformability of red blood cells (RBCs) can affect the hemodynamics in the microcirculation and reduce the oxygen transport efficiency. To this end, we developed a high-fidelity computational model of RBCs in confined microchannels to inform design decisions and fabricate a microfluidic device to measure RBC deformability. We applied our computational simulation platform to determine the appropriate deformability figure(s) of merit to quantify RBC stiffness based on an experimentally measured, steady cell shape. In particular, we determined a shape parameter based on the moment of area that is sensitive to the changes in the membrane stiffness and size. We conducted experiments and developed automatic image processing codes to track the velocity and morphology of individual RBCs within microchannels. For this purpose, we fabricated PDMS microchannels with square cross-sections (7x7 $\mu $m$^{\mathrm{2}})$ and applied a small (order 10 kPa) gauge pressure at the inlet to induce cell movement (order 10~mm s$^{\mathrm{-1}})$. Our experimental setup can record 200 cells per second, and achieve image exposure times on the order of 10~$\mu $s. This microfluidic device and supporting computational tools are intended to diagnose blood cell disorders in chronic fatigue syndrome (CFS) patients relative to the healthy controls. [Preview Abstract] |
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