Red blood cells (RBCs) are the major component of blood, and the flow of blood is dictated by that of RBCs. We employ vesicles, which consist of closed bilayer membranes enclosing a fluid, as a model system to study the behavior of RBCs under a confined Poiseuille flow. We extensively explore two main parameters: (i) the degree of confinement of vesicles within the channel and (ii) the flow strength. Rich and complex dynamics for vesicles are revealed, ranging from steady-state shapes (in the form of parachute and slipper shapes) to chaotic dynamics of shape. Chaos occurs through a cascade of multiple periodic oscillations of the vesicle shape. We summarize our results in a phase diagram in the parameter plane (degree of confinement and flow strength). This finding highlights the level of complexity of a flowing vesicle in the small Reynolds number where the flow is laminar in the absence of vesicles and can be rendered turbulent due to elasticity of vesicles.
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http://dx.doi.org/10.1103/PhysRevE.90.033011 | DOI Listing |
J Chem Phys
December 2024
State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China.
Comprehending the flow dynamics of ionic solutions within nanoconfined spaces is imperative for diverse applications encompassing desalination, nanofiltration, energy storage, and electrochemical devices. When the confinement space is further reduced to 1 nm (Ångstrom scale), monolayer ionic solutions will emerge. In this regime, ions not only have the ability to influence water properties such as viscosity but also primarily modify the interactions and corresponding slip length (or friction coefficient) between the solution and wall.
View Article and Find Full Text PDFACS Appl Mater Interfaces
October 2024
Department of Chemistry, University of Manchester, Oxford Road, M13 9PL Manchester, U.K.
The flow of water confined in nanosize capillaries is subject of intense research due to its relevance in the fabrication of nanofluidic devices and in the development of theories for fluid transport in porous media. Here, using molecular dynamics simulations carried out on 2D capillaries made up of graphite, hexagonal boron nitride (hBN) and a mix of the two, and of sizes from subnanometer to few nanometers, we investigate the relationship between the wettability of the wall capillary, the water diffusion, and its flow rate. We find that the water diffusion is decoupled from its flow properties as the former is not affected either by the height or chemistry of the capillary (except for the subnanometer slits), while the latter is dependent on both.
View Article and Find Full Text PDFSoft Matter
August 2024
Université Grenoble Alpes, CNRS, LIPhy, F-38000 Grenoble, France.
In this answer, we provide our arguments in support of the possibility to observe the single file-organization of red blood cells in microvessels and the resulting unexpectedly weak increase of blood viscosity with increasing hematocrit, the physiological relevance of which was questioned in the comment. The key element is that the equivalent diameter in 3D for the maximal hematocrit corresponding to a single file of red blood cells is about 10 µm and not 20 µm, as in 2D. In addition, the viscosity contrast (ratio between the cell internal and external viscosities) value must be chosen in our 2D simulation in a such a way that the effective viscosity (a linear combination of the internal, external and membrane viscosities) be close to that of a real RBC.
View Article and Find Full Text PDFSoft Matter
August 2024
Université Grenoble Alpes, CNRS, Grenoble INP, LRP, F-38000 Grenoble, France.
In a recent paper, [Gou , , 2023, , 9101-9114] studied numerically the viscosity of a confined suspension of vesicles flowing in a channel as a function of vesicle concentration. In order to discuss the genericity of the observed behaviour, namely a nearly constant effective viscosity at low concentrations, we complement their study by a comparison with the few existing ones in the literature. In particular, we highlight that they fail to reproduce well established results for blood viscosity in microcirculation, thereby suggesting that the conclusions regarding the optimization of cell transport and oxygenation may not apply.
View Article and Find Full Text PDFSci Rep
June 2024
CNRS, LIPhy, Université Grenoble Alpes, 38000, Grenoble, France.
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