Bulletin of the American Physical Society
76th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 19–21, 2023; Washington, DC
Session G14: Biofluids: Single Cell and Bacteria II |
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Chair: Luca Pellegrino, Humanitas University Room: 144AB |
Sunday, November 19, 2023 3:00PM - 3:13PM |
G14.00001: Hemolysis quantification for single ventricles undergoing the stage I (Norwood) operation Saba Mansour, Grant J Rydquist, Mahdi Esmaily The Norwood procedure is a lifesaving surgical operation performed on newborns suffering from hypoplastic left heart syndrome (HLHS). This operation involves the insertion of a shunt to create a parallel circulation between systemic and pulmonary circuits. The blockage of the established circulation is fatal, accounting for a large portion of complications in these patients. As the first step to understanding such complications, we adopt a multiscale model in this study to predict hemolysis in a set of idealized models. For this purpose, we use our in-house CFD solver coupled with cell-resolved Lagrangian models of red blood cells (RBCs) to measure stresses and strains on the RBC membrane for quantifying the RBC damage and, in extreme cases, rupture caused by this surgery. In total, we simulated three anatomies including 2.5mm and 4.0mm diameter Blalock-Taussig (BT) shunts and a 2.5mm central shunt, with 2000 RBCs in each case. Using maximum strain as an indicator of hemolysis, the results suggest that the shunt configuration has a larger effect on the RBC damage than changing the shunt size, with a larger diameter shunt being more prone to hemolysis. Overall, the central shunt creates the highest areal and shear strains on RBCs' surface, indicating that it is a riskier option in comparison to the BT shunt in terms of hemolysis. |
Sunday, November 19, 2023 3:13PM - 3:26PM |
G14.00002: Microbial interaction with micrometer-scale wrinkled surfaces subjected to fluid shear Luca Pellegrino, Giovanni Savonara, Eleonora Secchi, Roberto Rusconi, Valeriano Vinci Surface properties influence bacterial adhesion, which is the first step towards colonization and biofilm formation. For implantable devices, biofilm-associated infections are the most common clinical complications, given their resistance against mechanical stress and antibiotics; therefore, it becomes of paramount importance to designing surfaces able to prevent or reduce bacterial colonization. |
Sunday, November 19, 2023 3:26PM - 3:39PM |
G14.00003: Penetration of thin polymeric membranes by microswimmers Rudi Schuech, Ricardo Cortez, Lisa J Fauci At the microscale, particles and microorganisms are often filtered by or swim through thin networks of polymers immersed in a viscous fluid. For instance, ascidians feed by filtering particles through a mucosal interface composed of a discrete mesh of filaments with pores comparable to the size of prey bacteria. Due to the length scales involved, we model this polymeric interface as a discrete elastic network rather than adopting a continuum description. Connectivities and stiffnesses of elastic links between network nodes endow the interface with membrane-like material properties. Network links could also be dynamically broken if, for instance, they experience a stress beyond a given threshold. Here we use a regularized Stokeslet boundary element method to compute the motion of a microswimmer as it attempts to penetrate this interface. We compare the dynamics of both externally-driven spherical particles and helically-propelled microswimmers that are either free-swimmers like natural bacteria or externally-actuated like many microrobots. We found that the ability of a particle or microswimmer to successfully penetrate the membrane depends on the mode of propulsion as well as the network properties. |
Sunday, November 19, 2023 3:39PM - 3:52PM |
G14.00004: Viscoelastic Focusing of Living Cells: Fluidic Mechanics Insights for Microfluidic Device Design Takayuki Suzuki, Soojung C Hur This study presents an experimental investigation of viscoelastic focusing on living cells, with a specific emphasis on viscoelasticity influence. Experiments were conducted in straight microchannels with a rectangular cross-section (WXH= 34.5 X 80 μm and 80 X 34.5 μm), exploring a wide range of Reynolds numbers (Re = 0.01 to 44), viscoelasticity (EI = 0.36 to 1.7), and shear thinning effects of carrier fluids to study their impact on cell-focusing behaviors. The extensive dataset obtained from our high-speed video-collecting apparatus (400 to 30,000 fps and 100,000+ frames per condition) allowed for a meticulous single-cell level analysis of the interplay between fluid inertia and viscoelastic characteristics. The investigation yields crucial design guidelines for microfluidic devices that effectively leverage viscoelastic focusing for label-free cell purification and flow cytometry. This work serves as a critical resource for researchers and practitioners aiming to optimize microfluidic devices for cell manipulation and various fluidic mechanics-based applications. |
Sunday, November 19, 2023 3:52PM - 4:05PM |
G14.00005: Intestinal folds accumulate bacteria through physical and biological factors Jinyou Yang, Toma Isaka, Kenji Kikuchi, Keiko Numayama-Tsuruta, Takuji Ishikawa The gut microbiota is widely acknowledged as a crucial element for maintaining the health of the host. Understanding the mechanisms governing bacterial behavior and distribution within the gut holds significant importance. Bacterial accumulation is particularly noteworthy due to its potential to lead to biofilm formation, but the underlying mechanism remains unclear. Hence, our study focused on investigating Escherichia coli (E. coli) behavior and distribution in zebrafish larval intestines, with a specific emphasis on the gut microenvironment's influence. We observed distinct E. coli movement was restrained within the intestinal folds, resulting in a higher accumulation within these structures. Our in vitro microfluidic experiments confirmed that the physical properties associated with the intestinal wall's geometric shape facilitated preferential E. coli accumulation in the folds. Additionally, a higher density of E. coli was observed on the dorsal side of the intestines. To understand the phenomena, we constructed a continuum model that accounts for the physical factor of decrease in cell flux from the wall to the bulk and the biological factor of directional movement of cells from the ventral to the dorsal side. Through theoretical analysis, we revealed that the overall distribution of E. coli in the intestines resulted from a combination of physical and biological factors. These findings provide valuable insights into how the intestinal microenvironment influences bacterial accumulation. |
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