Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session M16: Biofluids: Blood Cells |
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Chair: Prosenjit Bagchi, Rutgers University Room: 28B |
Tuesday, November 20, 2012 8:00AM - 8:13AM |
M16.00001: Orbital drift of capsules and red blood cells Dan Cordasco, Prosenjit Bagchi Experiments using deformable red blood cells (RBC) in shear flow showed that the cells orient their symmetry axis towards the plane of shear (C = $\infty$ orbit) in a high viscosity medium, and along the vorticity direction (C = 0 orbit) in a low viscosity medium. In contrast, rigid ellipsoids in Stokes flow exhibit degenerate trajectories. The degeneracy can be broken by inertial effects, or, deformability. To explore the orientational drift, we conduct a 3D numerical simulation of prolate and oblate capsules and RBC over a range of capillary number, asphericity, and viscosity ratio. Four types of motion are observed: a stable precessing about C = 0, a stable kayaking about C = $\infty$, an unstable precessing towards C = 0, and a transition from a kayaking to a drifting precession. A prolate capsule with viscosity ratio of one mostly exhibits a kayaking at low asphericity, but mostly a drifting precession at high asphericity. In contrast, an oblate capsule drifts towards C = $\infty$. In agreement with published experiments, we find that the RBC orients its symmetry axis to C = 0 at high viscosity ratio, and C = $\infty$ at low viscosity ratio. We also find that the RBC orientation is dependent on the capillary number, implying the role of deformation. [Preview Abstract] |
Tuesday, November 20, 2012 8:13AM - 8:26AM |
M16.00002: Mechanical Response of Red Blood Cells Entering a Constriction: Influence of Oxidative Stress N.F. Zeng, W.D. Ristenpart A key determinant of RBC deformability is the level of oxidative stress, i.e., the imbalance of reactive oxygen species (ROS) associated with many disease states. Previous work has shown that oxidative stress rigidifies RBC membranes, but little is known about the mechanical response of RBCs to oxidative stress under physiological shear conditions. Here we show that oxidative stress significantly alters the dynamic mechanical behavior of RBCs undergoing a sudden increase in shear stress. Using high speed video, we tracked the motion of RBCs entering a narrow constriction in a microfluidic channel. Varied concentrations of hydrogen peroxide, a generator of ROS, were added to the RBCs to induce oxidative stress. We demonstrate that an H2O2 concentration as low as 30$\mu$M significantly decreases the percentage of RBCs undergoing stretching and twisting motions, while simultaneously increasing the percentage of RBCs undergoing tumbling motions. A key observation is that the H2O2 treatment reduced the average RBC volume by up to 30$\%$, suggesting that an increase in intracellular viscosity increased the propensity for RBCs to tumble. [Preview Abstract] |
Tuesday, November 20, 2012 8:26AM - 8:39AM |
M16.00003: Skeleton deformation of red blood cells during tank treading motions Qiang Zhu, Zhangli Peng By coupling a fluid-structure interaction algorithm with a three-level multiscale structural model, we simulate the tank treading responses of erythrocytes (red blood cells, or RBC) in shear flows. The fluid motion is depicted within the Stokes-flow framework, and is mathematically formulated with the boundary integral equations. The structural model takes into account the flexible connectivity between the lipid bilayer and the protein skeleton as well as the viscoelastic responses. The concentration of this study is on the transient process involving the development of the local area deformation of the protein skeleton. Under the assumption that the protein skeleton is stress-free in the natural biconcave configuration, our simulations indicate the following properties: (1) During tank treading motions it takes long time for significant area deformations to establish. For cells with diminished connectivity between the lipid bilayer and the protein skeleton (e.g. cells with mutations or defects), the relaxation time will be greatly reduced; (2) Deformations of the skeleton depend on the initial orientation of the cell with respect to the incoming flow; (3) The maximum area expansion occurs around the regions corresponding to the dimples in the original biconcave state; (4) Oscillations in cell geometry (breathing) and orientation (e.g. swinging) are observed. [Preview Abstract] |
Tuesday, November 20, 2012 8:39AM - 8:52AM |
M16.00004: Deformation of a single red blood cell in bounded Poiseuille flows Lingling Shi, Tsorng-Whay Pan, Roland Glowinski An immersed boundary method (IBM) combined with the elastic spring model is applied to investigate the deformation of a single red blood cell (RBC) in two-dimensional bounded Poiseuille flows. The equilibrium shape of the cell under flow depends on the swelling ratio (($s^*$)), the initial angle of the long axis of the cell at the centerline ($\varphi$), the maximum velocity of the flow ($u_\textrm{max}$), the membrane bending stiffness of the RBC ($k_b$), and the height of the microchannel($H$). Two motions of oscillation and vacillating breathing of the RBC are observed in narrow channel considered here. The strength of the vacillating-breathing motion depends on degree of confinement and $u_\textrm{max}$. For the different $k_b$, the RBC obtains the same equilibrium shape for the same capillary number. Parachute shape and bullet-like shape, depending on the angle $\varphi$, coexist for the elliptic shape cell with lower $u_\textrm{max}$ in a narrower channel. [Preview Abstract] |
Tuesday, November 20, 2012 8:52AM - 9:05AM |
M16.00005: On the oscillating motion of a red blood cell in bounded Poiseuille flows Yao Yu, Lingling Shi, Roland Glowinski, Tsorng-Whay Pan Two motions of oscillation and vacillating breathing (swing) a RBC have been observed in bounded Poiseuille flows [Phys. Rev. E 85, 16307 (2012)]. To understand such motions, we have studied the motion of a neutrally buoyant rigid particle of the same shape in bounded Poiseuille flows and obtained that the equilibrium height of the mass center, the confined ratio of the long axis of the particle and the channel height, and the initial position of the particle are important factors for having such oscillating motion. But the crucial one is to have the particle interacting with Poiseuille flow with its mass center oscillating about the channel center. When the mass center is always away from the channel center, the particle just keep rotating. Since the mass center of the cell migrates to the channel center in bounded Poiseuille flow in the regime of low Reynolds number, the oscillating motion then is similar to the aforementioned motion as long as the cell keeps the shape of long body. [Preview Abstract] |
Tuesday, November 20, 2012 9:05AM - 9:18AM |
M16.00006: Simulation of the Effect of Red Blood Cell Collisions on Platelet Adsorption Sean Fitzgibbon, Hong Zhao, Eric Shaqfeh The adsorption of platelets to the endothelial wall is an important first step in the clotting process, which is critical to stopping blood loss after trauma. Initial platelet arrest is controlled by very short range interaction between two proteins, von Willibrand Factor and GPIb, so the rate of platelet adsorption is expected to be strongly dependent on the rate at which the platelets sample the wall. With Peclet numbers in the range (10$^{3}$ - 10$^{5})$, simple diffusive arguments are not sufficient to explain the high rates of platelet adsorption. Using Stokes flow simulations, we show that the platelets' wall sampling rate is significantly increased by interactions with red blood cells. Our simulation models platelets as rigid bodies suspended in a Stokesian linear shear flow. We solve for the flow using standard boundary integral techniques with the appropriate single wall bounded Green's function. Receptor-ligand interactions are represented as Hookean springs with characteristic lifetimes, sizes, and stiffness coefficients. Drag forces are calculated with the reciprocal theorem, and RBC collisions are modelled as AR processes extracted from the large scale suspension simulations of Zhao et al. [Preview Abstract] |
Tuesday, November 20, 2012 9:18AM - 9:31AM |
M16.00007: Microfluidic approach of Sickled Cell Anemia Manouk Abkarian, Etienne Loiseau, Gladys Massiera Sickle Cell Anemia is a disorder of the microcirculation caused by a genetic point mutation that produces an altered hemoglobin protein called HbS. HbS self-assembles reversibly into long rope like fibers inside the red blood cells. The resulting distorded sickled red blood cells are believed to block the smallest capillaries of the tissues producing anemia. Despite the large amount of work that provided a thorough understanding of HbS polymerization in bulk as well as in intact red blood cells at rest, no consequent cellular scale approaches of the study of polymerization and its link to the capillary obstruction have been proposed in microflow, although the problem of obstruction is in essence a circulatory problem. Here, we use microfluidic channels, designed to mimic physiological conditions (flow velocity, oxygen concentration, hematocrit...) of the microcirculation to carry out a biomimetic study at the cellular scale of sickled cell vaso-occlusion. We show that flow geometry, oxygen concentration, white blood cells and free hemoglobin S are essential in the formation of original cell aggregates which could play a role in the vaso-occlusion events. [Preview Abstract] |
Tuesday, November 20, 2012 9:31AM - 9:44AM |
M16.00008: Mechanism of vaso-occlusion in sickle cell anemia Huan Lei, George Karniadakis Vaso-occlusion crisis is one of the key hallmark of sickle cell anemia. While early studies suggested that the crisis is caused by blockage of a single elongated cell, recent experimental investigations indicate that vaso-occlusion is a complex process triggered by adhesive interactions among different cell groups in multiple stages. Based on dissipative particle dynamics, a multi-scale model for the sickle red blood cells (SS-RBCs), accounting for diversity in both shapes and cell rigidities, is developed to investigate the mechanism of vaso-occlusion crisis. Using this model, the adhesive dynamics of single SS-RBC was investigated in arterioles. Simulation results indicate that the different cell groups (deformable SS2 RBCs, rigid SS4 RBCs, leukocytes, {\it etc.}) exhibit heterogeneous adhesive behavior due to the different cell morphologies and membrane rigidities. We further simulate the tube flow of SS-RBC suspensions with different cell fractions. The more adhesive SS2 cells interact with the vascular endothelium and further trap rigid SS4 cells, resulting in vaso-occlusion in vessels less than $15 \mu m$. Under inflammation, adherent leukocytes may also trap SS4 cells, resulting in vaso-occlusion in even larger vessels. [Preview Abstract] |
Tuesday, November 20, 2012 9:44AM - 9:57AM |
M16.00009: How does confinement affect the dynamics of viscous vesicles and red blood cells? Badr Kaoui, Timm Kruger, Jens Harting Despite its significance in microfluidics, the effect of confinement on the transition from the tanktreading (steady motion) to the tumbling (unsteady motion) dynamical state of deformable microparticles has not been studied in detail. In this work, we investigate the dynamics of a single viscous vesicle under confining shear as a general model system for red blood cells, capsules, or viscous droplets. The transition from the tank-treading to the tumbling motion can be triggered by the ratio between internal and external fluid viscosities. Here, we show that the transition can be induced solely by reducing the confinement, keeping the viscosity contrast constant. The observed dynamics results from the variation of the relative importance of viscous-, pressure-, and lubrication-induced torques exerted upon the vesicle. Our findings are of interest for designing future experiments or microfluidic devices: the possibility to trigger the tumbling-to-tank-treading transition either by geometry or viscosity contrast alone opens attractive possibilities for microrheological measurements as well as the detection and diagnosis of diseased red blood cells in confined flow. [Preview Abstract] |
Tuesday, November 20, 2012 9:57AM - 10:10AM |
M16.00010: Desiccation of a pool of blood: from fluid mechanics to forensic investigations Celine Nicloux, David Brutin The evaporation of biological fluids (with droplet configuration) has been studied since a few years due to several applications in medical fields such as medical tests, drug screening, biostabilization{\ldots} The evaporation of a drop of whole blood leads to the formation of final typical pattern of cracks [1]. Flow motion, adhesion, gelation and fracturation all occur during the evaporation of this complex matter. During the drying, a sol-gel transition develops. The evaporation of a pool of blood is studied in order to link the pattern formation and the evaporation dynamics. We intend to transfer the knowledge acquired for drops on pool to improve the forensic investigations. In this study, we focus on both pool of blood and pure water to determine the transition region from drop to pool and then to characterize the evaporation rate in the pool configuration. The spreading of blood which can be seen as a complex fluid is strongly influenced the substrate nature. The initial contact angle of blood on different substrate nature [2] will influence the maximum thickness of the layer and then will influence the evaporation mass flux.\\[4pt] [1] B. Sobac \& D. Brutin, Phys. Rev. E 84, 011603, 2011.\\[0pt] [2] Brutin D., Sobac B., Nicloux C., Journal of Heat Transfer, Vol. 134, 061101, 2012. [Preview Abstract] |
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