Bulletin of the American Physical Society
66th Annual Meeting of the APS Division of Fluid Dynamics
Volume 58, Number 18
Sunday–Tuesday, November 24–26, 2013; Pittsburgh, Pennsylvania
Session D19: Biofluids: Cellular I - Computational Studies on Cellular Kinematics |
Hide Abstracts |
Chair: Timothy Wei, University of Nebraska, Lincoln Room: 310/311 |
Sunday, November 24, 2013 2:15PM - 2:28PM |
D19.00001: Fluid Flow in Cell Printing Maziyar Jalaal, Eric Cheng, Ali Ahmadi, Karen Cheung, Boris Stoeber Inkjet drop-on-demand (DOD) dispensing of cells has numerous applications including cell-based assays and tissue engineering. In our experiments, using a transparent inkjet nozzle, high speed camera, and a shadowgraphy technique, we have observed three different characteristic cell behaviors during droplet ejection: 1) traveling toward the nozzle tip, 2) ejection from the nozzle, and 3) reflection away from the nozzle tip, where the reflection is an unwanted effect which contributes to the unpredictability of current cell printing systems. To understand the reflection mechanisms, we use numerical simulation to resolve the fluid motion inside the nozzle in presence of a cell during drop formation. For this purpose an adaptive finite volume method is employed. To track the interfaces (cell-liquid, gas-liquid) a volume of fluid (VOF) method is used, where the cell is modeled as an immiscible fluid droplet with different physical properties from the suspending fluid. It is shown that after a short period of time, a recirculation zone close to the nozzle tip is generated due to droplet pinch-off. This causes a reverse flow (velocity away from the nozzle) in the center of the nozzle. This dynamic flow field inside the nozzle causes a cell to show one of the three behaviors described above depending on its initial position. Moreover, it is shown that, depending on the size, deformability, and location of the cell, the drop formation process may be influenced. [Preview Abstract] |
Sunday, November 24, 2013 2:28PM - 2:41PM |
D19.00002: Numerical computations of ionic electrodiffusion and osmotic water flow in cells Lingxing Yao, Yoichiro Mori We develop a computational method to characterize ionic electrodiffusion and osmotic water flow in cellular systems. In the biological model system we used, cell membranes, which are permeable to both water and ionic flows, divide the domain into intracellular and extracellular regions. The cell membranes move with the flow it is embedded in, while its elastic force and osmotic forces due to ions will in turn affect fluid properties. The whole system is then consists of fluid-structure interactions, coupled with ionic electrodiffusion on domain with moving (internal) interfaces. The numerical computation of advection-diffusion in a 2d rectangle domain with moving boundaries is carried out by using a embedded Cartesian grid method over the entire rectangle domain, which represents the intra- and extracellular regions, while the fluid-structure interactions is handled by the Immersed Boundary Method. We will describe our numerical scheme of solving this PDE system and illustrate the results with some simple applications as the proof of principles. [Preview Abstract] |
Sunday, November 24, 2013 2:41PM - 2:54PM |
D19.00003: Numerical Modeling of Flow through Phloem Considering Active Loading Jin Liu, Tsun-kay Jackie Sze, Prashanta Dutta Transport through phloem is of significant interest in engineering applications including self-powered microfluidic pumps. We present a phloem model, combining protein level mechanics with cellular level fluid transport. Fluid flow and sucrose transport through a petiole sieve tube are simulated using the Nernst-Planck, Navier-Stokes, and continuity equations. Governing equations are solved using the finite volume method with dynamically calculated boundary conditions. Sieve tube cell structure consisting of sieve plates is included in a two dimensional model by computational cell blocking. Sucrose transport is incorporated as a boundary condition through a six-state model, bringing in active loading mechanisms with consideration of physical plant properties. The effects of reaction rates and leaf sucrose concentration are investigated to understand the transport mechanism in petiole sieve tubes. Numerical results show that increasing forward reactions of the proton sucrose transporter significantly promotes the pumping ability. A lower leaf sieve sucrose concentration results in a lower wall inflow velocity, but yields a higher inflow of water due to the active loading mechanism. The overall effect is higher outflow velocity for lower leaf sieve sucrose concentration because the increase in inflow velocity outweighs wall velocity. This new phloem model provides new insights on mechanisms potentially useful for fluidic pumping in self-powered microfluidic pumps. [Preview Abstract] |
Sunday, November 24, 2013 2:54PM - 3:07PM |
D19.00004: The Effect of Shape Memory on Red Blood Cell Motions Xiting Niu, Lingling Shi, Tsorng-Whay Pan, Roland Glowinski An elastic spring model is applied to study the effect of the shape memory on the motion of red blood cell in flows. In shear flow, shape memory also plays an important role to obtain all three motions: tumbling, swinging, and tank-treading. In Poiseuille flow, cell has an equilibrium shape as a slipper or parachute depending on capillary number. To ensure the tank-treading motion while in slippery shape, a modified model is proposed by introducing a shape memory coefficient which describes the degree of shape memory in cells. The effect of the coefficient on the cell motion of red blood cell will be presented. [Preview Abstract] |
Sunday, November 24, 2013 3:07PM - 3:20PM |
D19.00005: Numerical simulation of red blood cell suspensions behind a moving interface in a capillary Shihai Zhao, Tsorng-Whay Pan Computational modeling and simulation are presented on the motion of red blood cells behind a moving interface in a capillary. The methodology is based on an immersed boundary method and the skeleton structure of the red blood cell (RBC) membrane is modeled as a spring network. The computational domain is moving with either a designated RBC or an interface in an infinitely long two-dimensional channel with an undisturbed flow field in front of the domain. The tanking-treading and the inclination angle of a cell in a simple shear flow are briefly discussed for the validation purpose. We then present the results of the motion of red blood cells behind a moving interface in a capillary, which show that the RBCs with higher velocity than the interface speed form a concentrated slug behind the interface. It is a key mechanism responsible for penetration failure in a capillary behind the meniscus. [Preview Abstract] |
Sunday, November 24, 2013 3:20PM - 3:33PM |
D19.00006: Probing bilayer--cytoskeletal interactions in erythrocytes using a two-component dissipative particle dynamics model Zhangli Peng, Xuejin Li, Igor Pivkin, Ming Dao, George Karniadakis We develop a two-component dissipative particle dynamics (DPD) model of the red blood cell (RBC) membrane by modeling the lipid bilayer and the cytoskeleton separately. By applying this model to simulate four different experiments on RBCs, including micropipette aspiration, membrane fluctuations, tank-treading motions in shear flow and bilayer tethering in a flow channel, we validated our model and studied the mechanical properties of the bilayer--cytoskeletal interaction in a systematic and controlled manner, such as its elastic stiffness, viscous friction and strength. In the same time, we also resolved several controversies in RBC mechanics, e.g., the dependence of tank-treading frequency on shear rates and the possibility of bilayer--cytoskeletal slip. Furthermore, to investigate RBC dynamics in the microcirculation, we simulated the passages of RBCs through narrow channels of the flow cytometer in vitro and their passages through the splenic inter-endothelial slits in vivo. The effects of RBC geometry and membrane stiffness on the critical pressure gradient of passage were studied, and the simulation results agree well with experimental measurements. [Preview Abstract] |
Sunday, November 24, 2013 3:33PM - 3:46PM |
D19.00007: Quantifying the transition of blood flow to the non-continuum regime Huan Lei, Dmitry Fedosov, Bruce Caswell, George Karniadakis Blood flow is usually treated as a Newtonian fluid down to diameters of about $200$ $\mu m$. We employ the dissipative particle dynamics to simulate the flow of red blood cell suspensions driven through small tubes (diameters $10-150$ $\mu m$) in the range marking the transition from venules to the large capillaries. Simulation results show that for diameters less than about $100$ $\mu m$ the suspension's stress cannot be described as a continuum, even a heterogeneous one. In tube flow the cross-stream stress gradient induces an inhomogeneous distribution of RBCs featuring a centerline cell density peak, and a cell-free layer next to the wall. The local viscosity across the section as a function of the strain rate is found to be essentially independent of tube size for the larger diameters and is determined by the local hematocrit ($H$) and shear rate. As the tube diameter decreases below about $100$ $\mu m$, the viscosity in the central region departs from the large-tube similarity function of the shear rate, since $H$ increases significantly towards the centerline. The dependence of shear stress on tube size, in addition to the expected local shear rate and local hematocrit, implies that blood flow in small tubes cannot be described as a heterogeneous continuum. [Preview Abstract] |
Sunday, November 24, 2013 3:46PM - 3:59PM |
D19.00008: 2-Point Particle Tracking Microrheology of Directional Gels Manuel Gomez-Gonzalez, Juan C. del Alamo The stiffness of the cell cytoplasm, and other minute-quantity materials, can be measured by using Particle Tracking Microrheology, where a micron size spherical particle is used as a probe. It relies on the assumption of isotropy of the probed material. In order to apply it to highly oriented materials we have calculated the drag force of a microparticle embedded in a directional viscoelastic gel. The gel is modeled as a directional viscoelastic network frictionally coupled to a viscous isotropic fluid. The directional network is modeled with the Leslie-Ericksen equations and the isotropic fluid with the Stokes equation. The motion of particles embedded in such a directional gel is dependent on up to three viscoelastic coefficients, but only two can be calculated from tracking a single probing particle. We have calculated the first order perturbation that the motion of one probe induces on a distant particle, as a function of the three viscosity coefficients. By correlating the motion of two distant particles we can measure such a perturbation and obtain three independent equations that univocally determine the three viscoelasticity coefficients that define a directional viscoelastic gel. [Preview Abstract] |
Sunday, November 24, 2013 3:59PM - 4:12PM |
D19.00009: Ordered and chaotic flow of red blood cells flowing in a narrow tube Natalie N. Beams, Jonathan B. Freund Red blood cells are well known to line up in an orderly arrangement when forced to flow through a narrow capillary-scale round tube (diameter $\leq 8\mu$m). However, in slightly larger tubes, small perturbations from the center of the tube can cause this order to break down, resulting in apparently chaotic flow. Investigating this breakdown using a high-fidelity boundary integral solver for flowing blood cells, we show the existence of a bifurcation point for the appearance of this non-orderly behavior. The bifurcation point is found to be dependent on the diameter of the tube and the density of the cells, with more cells required to instigate chaotic behavior in smaller tubes (e.g., 27.5\% cells by volume for a $11.28 \mu$m diameter tube, but only 5.63\% for similar behavior in a tube twice that width). Increasing the cell interior viscosity is also observed to increase the amplification of perturbations. Additionally, as a counterpoint, we show that cells flowing chaotically in $D = 12 \mu $m tubes, apparently indefinitely, will slowly organize into a regular single file if $D$ is decreased to $D \approx 10 \mu$m. [Preview Abstract] |
Sunday, November 24, 2013 4:12PM - 4:25PM |
D19.00010: Three-dimensional simulations of the cell growth and cytokinesis using an immersed boundary method Yibao Li, Jung-il Choi For an animal cell, cytokinesis is the process by which a cell divides its cytoplasm to produce two daughter cells. We present a three-dimensional immersed boundary method for the simulation of cell growth and cytokinesis. The proposed model is robust and realistic in deciding the position of the cleavage furrow and in defining the contractile force leading to cell division. For accurate calculations, a simple surface re-meshing algorithm is applied to uniformalize distorted meshes. In addition, to keep the mass conservation of the numerical solution at each time step, we use the volume-preserving scheme (Li et al., 2013). We investigate the effects of each model parameter on the cell growth and cytokinesis, and compare numerical results with the experimental data to demonstrate the efficiency and accuracy of the proposed method. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2022 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
1 Research Road, Ridge, NY 11961-2701
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700