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 B30: Biological Fluid Dynamics : Microfluidics |
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Chair: C. Nadir Kaplan, Virginia Tech Room: 612 |
Saturday, November 23, 2019 4:40PM - 4:53PM |
B30.00001: Thermal Effects on Fluid Mixing in the Eye Jinglin Huang, Morteza Gharib Age-related macular degeneration (AMD) is the leading cause of central vision loss in the developed world. In the case of wet AMD, it can be managed through serial intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents. However, sometimes the treatment is ineffective and causes side effects. One possible cause of the ineffective treatment is the inefficient fluid mixing in the eye. Continued from my talk last year, we are now focusing on the understanding of thermal effects on fluid mixing in the vitreous chamber and various parameters that could affect it. The study outcomes will be useful for inspiring eye doctors to develop better strategies for improving treatment efficiency and optimizing patient experience. [Preview Abstract] |
Saturday, November 23, 2019 4:53PM - 5:06PM |
B30.00002: Computational analysis of interstitial fluid flow through the lacunar-canalicular system with morphological variations. Shailesh Khadangale, Samira Hajebrahimi, Maureen Lynch, Debanjan Mukherjee Osteocytes play a central role in maintenance of skeletal structure and associated mechanobiological processes. Interstitial fluid flow in the lacunar-canalicular system (LCS) is pivotal for osteocyte mechanotransduction but is challenging to model. For this we developed a CFD framework, based on Stokes-Brinkman model with variable permeability, for interstitial fluid flow in the LCS, and quantify shear at the osteocyte wall. We used our framework to quantify variations in shear due to changes in LCS morphology observed in metastatic bone cancer. A range of parametrically varied LCS morphologies were modeled based on lacunae dimensions and position data from micro-CT scan of healthy and cancerous mouse tibia. Shear on osteocytes was quantified for the various LCS morphologies considered to obtain bounds on osteocyte shear based on knowledge of lacuna shape and dimensions alone. Also, shear variations on osteocytes resulting from LCS morphology variations from neighboring sites were quantified. Our study revealed significant shear stress variations across all LCS morphological variations. Our over-arching theme is to advance this model into a computational toolkit to generate and test hypotheses on the role of shear mechano-transduction in metastatic bone cancer. [Preview Abstract] |
Saturday, November 23, 2019 5:06PM - 5:19PM |
B30.00003: Experimental modeling of fluid homeostasis in the mammalian hearing organ Ruy Ibanez, Mohammad Shokrian, Jong-Hoon Nam, Douglas H. Kelley The mammalian hearing organ (cochlea) contains a long microfluidic channel (channel width $\approx 50$ $\mu m$ and aspect ratio $\approx 700$. Ex-vivo observations have shown that auditory stimulations induce deformations, in the form of a travelling wave, on the walls of the microfluidic channel and produce a flow. By determining the relevant physical parameters in the channel and applying scaling laws, we designed an apparatus that can replicate the physical conditions of the inner ear channel. We seek to characterize the induced flow using particle tracking velocimetry measurements, as well as characterizing the Lagrangian dynamics using a particle advection code. We validate the experimental measurements by comparing to previous analytic results. We study the effect of channel’s end boundary conditions (open or closed) and the shape of the wall deformation on the flow dynamics. We also find good agreement with finite-element simulations. [Preview Abstract] |
(Author Not Attending)
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B30.00004: Prediction of Low-density Lipoprotein Concentration on the Lumen Surface of Pathological Blood Vessels Using Wall Shear Stress. Satyajit Choudhury, Kameswararao Anupindi, B.S.V Patnaik Accumulation of low-density lipoprotein (LDL) on the lumen surface of blood vessels is central to the initiation and progression of many cardiovascular diseases. It has been found that, in high Schmidt number flows, it is the near-wall flow dynamics that dictate the transport and accumulation of the LDL on the lumen surface. Since wall shear stress (WSS) offers a reasonable approximation of near-wall flow dynamics, our study utilizes WSS to predict the variation of concentration of LDL on the lumen surface of symmetric 2D as well as asymmetric 3D pathological arteries. Blood is considered as Newtonian, incompressible and modeled using the Navier-Stokes equation whereas, the transport of LDL is governed by the passive scalar advection-diffusion equation. Even though the flow is pulsatile, it is found that time-averaged WSS gives a very good prediction of the variation of LDL concentration on the lumen surface. It is seen that low WSS need not necessarily lead to high LDL concentration. The influence of the stagnation points (region of zero WSS) on LDL concentration is also explored in the present work. [Preview Abstract] |
Saturday, November 23, 2019 5:32PM - 5:45PM |
B30.00005: Rotation and propulsion in 3d active chiral droplets Livio Nicola Carenza, Giuseppe Gonnella, Davide Marenduzzo, Giuseppe Negro Chirality is an ubiquitous feature of biological matter. This may arise due to thermodynamic or non-equilibrium effects. Moreover biological fluids evolve far from thermodynamic equilibrium, since they are internally driven by the injection of energy at the level of the individual constituents. Despite much effort has been taken to understand the dynamics of active gels in bidimensional environments, much less is known about chiral systems and in general about active matter in 3d. Here we consider a three-dimensional droplet of inherently chiral and apolar material that can be modelled - in the passive limit - as a Cholesteric Liquid Crystal. Intrinsically chiral droplets display a range of astonishing behaviors. First, we find that active force dipoles strengthen the equilibrium chiral pattern, enabling a novel and fascinating motility mode, where the fan-like rotational motion of surface defects is converted into propulsion. Second, an active torque dipole sets up a periodical mirror rotation of two pairs of disclination lines exhibiting a "coiling and relaxing" dynamics. [Preview Abstract] |
Saturday, November 23, 2019 5:45PM - 5:58PM |
B30.00006: Examining role of composition on the formation of extracellular polymeric substance (EPS) aggregates over a rising oil micro-droplet under shear Jian Sheng, Mun Mun Nahar, Andrew White, Maryam Jalali After Deepwater Horizon spill, it is believed that up to 15{\%} of released oil settled to the sea floor as marine oil snow (MOS), which has been corroborated by field and laboratory observations. Several factors contributed to the production of MOS including particulate concentration and microbial mucous (e.g. EPS). EPS is a complex mixture of polysaccharides, proteins, nucleic acids and lipids, and their composition can vary significantly based on the microbial community and the environment. To examine quantitatively the role of EPS composition, specifically protein to hydrocarbon ratio (PHR), on aggregation, we use a microfluidics, ``ecology-on-a-chip'', to simulate an rising oil drop through a suspension containing EPS and particulates. Time lapse microscopy lasting several days captures the growth and morphology of EPS aggregates. We demonstrate that EPS in the absence of particles is unable to form aggregates, while the addition of particles induces rapid aggregation. The higher PHR results in more stickiness of the EPS molecule and consequently leads to larger and more rapid formation of MOS. Ongoing work is considering the influence of flow shear and various EPS conformation on aggregate formation in flows. Funded by GoMRI {\&} ARO [Preview Abstract] |
Saturday, November 23, 2019 5:58PM - 6:11PM |
B30.00007: Non-equilibrium signal integration in hydrogels C. Nadir Kaplan, Peter A. Korevaar, Alison Grinthal, Reanne M. Rust, Joanna Aizenberg Soft multiphase materials that perform controlled actuation and complex sensing are ubiquitous in living systems, and their synthetic analogs would transform developments in areas such as bioengineering or soft robotics. We introduce a fluid mechanical framework that predicts the minimal set of components needed to integrate bioinspired signal processing capabilities into a simple hydrogel that is activated upon transport and reaction of chemical stimuli. For a common polyacrylic acid hydrogel, with copper cations and acid as representative chemical stimuli, the theory explains the experimentally observed unique cascades of mechanical and optical responses. These results suggest simple hydrogels, already built into numerous systems, have a much larger sensing space than currently employed. [Preview Abstract] |
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