Bulletin of the American Physical Society
70th Annual Meeting of the APS Division of Fluid Dynamics
Volume 62, Number 14
Sunday–Tuesday, November 19–21, 2017; Denver, Colorado
Session A4: Flows involving Vesicles and MicellesBio Fluids: External
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Chair: David Salac, University at Buffalo Room: 404 |
Sunday, November 19, 2017 8:00AM - 8:13AM |
A4.00001: The motion of a train of vesicles in channel flow Joseph Barakat, Eric Shaqfeh The inertialess motion of a train of lipid-bilayer vesicles flowing through a channel is simulated using a 3D boundary integral equation method. Steady-state results are reported for vesicles positioned concentrically inside cylindrical channels of circular, square, and rectangular cross sections. The vesicle translational velocity U and excess channel pressure drop $\Delta $p$^{\mathrm{+}}$ depend strongly on the ratio of the vesicle radius to the hydraulic radius $\lambda $ and the vesicle reduced volume $\upsilon $. ``Deflated vesicles'' of lower reduced volume $\upsilon $ are more streamlined and translate with greater velocity U relative to the mean flow velocity V. Increasing the vesicle size ($\lambda )$ increases the wall friction force and extra pressure drop $\Delta $p$^{\mathrm{+}}$, which in turn reduces the vesicle velocity U. Hydrodynamic interactions between vesicles in a periodic train are largely screened by the channel walls, in accordance with previous results for spheres and drops. The hydraulic resistance is compared across different cross sections, and a simple correction factor is proposed to unify the results. Nonlinear effects are observed when $\beta $ -- the ratio of membrane bending elasticity to viscous traction -- is changed. The simulation results show excellent agreement with available experimental measurements as well as a previously reported ``small-gap theory'' valid for large values of $\lambda $. [Preview Abstract] |
Sunday, November 19, 2017 8:13AM - 8:26AM |
A4.00002: Rupture and Spreading Dynamics of Lipid Membranes on a Solid Surface Antonio Perazzo, Sangwoo Shin, Carlos Colosqui, Yuan-Nan Young, Howard A. Stone The spreading of lipid membranes on solid surfaces is a dynamic phenomenon relevant to drug delivery, endocytosis, biofouling, and the synthesis of supported lipid bilayers. Current technological developments are limited by an incomplete understanding of the spreading and adhesion dynamics of a lipid bilayer under different physicochemical conditions. Here, we present recent experimental and theoretical results for the spreading of giant unilamellar vesicles (GUVs), where the vesicle shell consists of a lipid bilayer. In particular, we study the effect of different background ion concentrations, osmolarity mismatches between the interior and the exterior of the vesicles, and different surface chemistries of the glass substrate. In all of the studied cases, we observe a delay time before a GUV in contact with the solid surface eventually ruptures. The rupture kinetics and subsequent spreading dynamics is controlled by the ionic screening within the thin film of liquid between the vesicle and the surface. Different rupture mechanisms, mobilities of the spreading vesicle, and degrees of substrate coverage are observed by varying the electrolyte concentration, solid surface charge, and osmolarity mismatch. [Preview Abstract] |
Sunday, November 19, 2017 8:26AM - 8:39AM |
A4.00003: Shape fluctuations of a giant lipid vesicle Hammad Faizi, Nicolas Galle, Petia Vlahovska Ultra-soft fluid interfaces, like biological membranes, possess a unique combination of area-incompressibility and very low bending rigidity. Several methods have been developed for the measurement of membrane bending rigidity and tension. Flicker spectroscopy relies on measurement of thermal shape undulations of the membrame. Mechanical deformation techniques such as micropipette aspiration and electrodeformation rely on the overall deformation of giant vesicles. Slight discrepancies have been observed in the bending rigidity measured with a different method. In this project, we measure the bending rigidity of the same vesicle with three different techniques; fluctuation analysis, electrodeformation and a new hybrid technique developed by us ‘Fluctuation analysis of a vesicle under electric field.’ We assess if these methods yield different values and discuss our findings in the context of local vs global properties, equilibrium vs out-of-equilibrium conditions. [Preview Abstract] |
Sunday, November 19, 2017 8:39AM - 8:52AM |
A4.00004: Three-Dimensional Hydrodynamics of Multicomponent Vesicles Prerna Gera, David Salac The cholesterol present in lipid membranes combine with the saturated lipids to form energetically stable domains that are surrounded by unsaturated lipids on the surface of a vesicle. In experimental studies, these domains have exhibit interesting and exotic patterns. A three dimensional continuum model is used in this work to replicate, understand, and explore the dynamics of a multicomponent vesicle. The multicomponent membrane is modeled using a two phase surface Cahn-Hilliard equation along with a combined level set/closest point method. The domains on the membrane is coupled with the fluid surrounding the vesicle via an energy variation approach. Using this coupled model the sample results will be presented and comparison with experimental work will be done. [Preview Abstract] |
Sunday, November 19, 2017 8:52AM - 9:05AM |
A4.00005: Coupling molecular dynamics with lattice Boltzmann method based on the immersed boundary method. Jifu Tan, Talid Sinno, Scott Diamond The study of viscous fluid flow coupled with rigid or deformable solids has many applications in biological and engineering problems, e.g., blood cell transport, drug delivery, and particulate flow. We developed a partitioned approach to solve this coupled Multiphysics problem. The fluid motion was solved by Palabos (Parallel Lattice Boltzmann Solver), while the solid displacement and deformation was simulated by LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator). The coupling was achieved through the immersed boundary method (IBM). The code modeled both rigid and deformable solids exposed to flow. The code was validated with the classic problem of rigid ellipsoid particle orbit in shear flow, blood cell stretching test and effective blood viscosity, and demonstrated essentially linear scaling over 16 cores. An example of the fluid-solid coupling was given for flexible filaments (drug carriers) transport in a flowing blood cell suspensions, highlighting the advantages and capabilities of the developed code. [Preview Abstract] |
Sunday, November 19, 2017 9:05AM - 9:18AM |
A4.00006: Waving of filaments induced by molecular motors Gabriele De Canio, Eric Lauga, Raymond E. Goldstein In many cellular phenomena, for example cytoplasmic streaming, molecular motors translocate along microtubules carrying cargoes which entrain fluid. The piconewton forces that motors produce can be sufficient to bend or buckle the filaments. When large numbers of such forced filaments interact through the surrounding fluid, as in particular stages of oocyte development in {\it Drosophila melanogaster}, complex dynamics are observed, but the mechanism underlying them has remained unclear. By using a combination of theory and numerical simulations, we study a simplified microtubules-molecular motor system in a viscous fluid and show that it can capture the wave-like filament motion dynamics observed in experiments. [Preview Abstract] |
Sunday, November 19, 2017 9:18AM - 9:31AM |
A4.00007: Mechanical characterization of capsule properties using abrupt-step channels Anne-Virginie Salsac, Anne Le Goff, Badr Kaoui, Dominique Barthès-Biesel Capsules consisting of a liquid droplet enclosed by a thin polymerized membrane are commonly encountered in nature (cells) or in industrial process (pharmaceutical, cosmetic or food products). The mechanical properties of the capsule wall are essential to guarantee the particle integrity and release of the internal contents when and where necessary. The difficulty is to assess the mechanical properties of the thin membrane. We will show how abrupt-step channels can be used to identify the membrane viscoelastic properties and point of rupture. This can be achieved by using a channel presenting a step change in cross-section and inverting the direction of the flow of the capsule suspension within the tube. To deduce information on the viscoelasticity, we will exploit the relaxation of the capsules as they flow through the expansion. To study membrane rupture, we will instead invert the channel, block the capsules at the neck of the constriction and determine the pressure difference needed for breakup. All the experiments will be conducted on initially spherical capsules with a thin cross-linked protein membrane for a proof of concept. [Preview Abstract] |
Sunday, November 19, 2017 9:31AM - 9:44AM |
A4.00008: DPD simulation on the dynamics of a healthy and infected red blood cell in flow through a constricted channel Sazid Zamal Hoque, D. Vijay Anand, B.S.V. Patnaik The state of the red blood cell (either healthy or infected RBC) will influence its deformation dynamics. Since the pathological condition related to RBC, primarily originates from a single cell infection, therefore, it is important to relate the deformation dynamics to the mechanical properties (such as, bending rigidity and membrane elasticity). In the present study, numerical simulation of a healthy and malaria infected RBC in a constricted channel is analyzed. The flow simulations are carried out using finite sized dissipative particle dynamics (FDPD) method in conjunction with a discrete model that represents the membrane of the RBC. The numerical equivalent of optical tweezers test is validated against the experimental studies. Two different types of constrictions, viz., a converging-diverging type tapered channel and a stenosed microchannel are considered for the simulation. The effect of degree of constriction and the flow rate effect on the RBC is investigated. It was observed that, as the flow rate decreases, the infected RBC completely blocks the micro vessel. The transit time for infected cell drastically increases compared to healthy RBC. Our simulations indicate that, there is a critical flow rate below which infected RBC cannot pass through the micro capillary. [Preview Abstract] |
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