Computational methods for the suspensions of deformable and rigid particles and their applications to modelling of blood flows

University Of Houston, Houston TX

Investigators

Abstract

This project focuses on developing computational methods for simulating the suspensions of deformable and rigid particles and their applications to modeling the microcirculation of blood flow and cell separation in microchannel flow. It is computationally challenging to simulate directly the three-dimensional motion and dynamics of hydrodynamically interacting red blood cells in a fluid. We will use a spring network model with its associated energy potential to model the membrane of the red blood cell. We propose to combine the spring network model with the immersed boundary methods, finite element methods and operator splitting techniques to simulate the cell-fluid and cell-cell interactions in three dimensions. We also want to combine the above proposed methodology with the distributed Lagrange multiplier/fictitious domain methods, which are closed related to the immersed boundary methods, to simulate the suspensions of cells and solid particles. Through the computational methodologies proposed by the PIs, efficient three-dimensional simulations of the red blood cells in microvessels will be performed to study the rheology of red blood cells in microcirculation, the margination dynamics of solid particles in microvessels and the cell separation in microchannels. The microcirculation, which takes place in the smallest blood vessels (i.e., arterioles, capillaries, and venules), is responsible for regulating blood flow in individual organs and for exchange between blood and tissue. Since blood contains about 40-45% red blood cells by volume, as well as platelets and leukocytes, the interactions of these formed elements play a crucial role in determining blood characteristics. Because of their large volume fraction and their aggregation capacity, red blood cells are the most important determinant of blood flow characteristics. While theories of suspension rheology generally focus on homogeneous flows in infinite domains, the important phenomena of blood flows in microcirculation depend on the combined effects of vessel geometries, cell deformabilities, wall compliance, flow shear rates, and many micro-scale chemical, physiological, and biological factors. We concentrate on the rheological aspects of flow in microcirculation involving deformable cells, cell-cell interactions and vessel geometry, which is particularly challenging theoretically and computationally. The first main application is to study the margination dynamics of solid particles in microvessels. The intravascular delivery of rigid particles for biomedical imaging and therapy is being recognized as a powerful and promising tool in cardiovarscular and oncological applications. These particles can be loaded with drug molecules and contrast agents and transported by the blood flow through the circulatory system. They are generally decorated with ligand molecules which are able to interact specifically with antigens expressed over diseased cells (or target cells). The effect of particle shape, size and density on margination propensity is needed to be analyzed in order to find the optimal design. The second main application is to study cell separation in microchannel flow. The main focus is to gain inside in the separation of healthy and sick red blood cells due to their deformability and size on a microfluidic biochip platform. Separation of soft objects is of enormous relevance in medical and biological applications, since very often a loss in deformability comes along with diseases such as malaria, diabetes mellitus or cancer, just to name a few. Hence, a microfluidic system to sort or separate cells would be of tremendous importance for both diagnostic and dialysis applications.