Effect of polymers on the flow behavior of blood in-vitro

• Applicant: Professor Dr. Christian Wagner, since 2/2024
• Subject Area: Fluid Mechanics ; Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 349558021

Red blood cells (RBCs) are the main constituent of human blood and deliver oxygen to the body tissues via the cardiovascular system. The cardiovascular system is a complex network of branching vessels of different sizes and geometries, such as sudden constrictions and expansions in stenosed arteries. The unique flow properties of blood in this network are crucial for its physiological functionality and stem from various microscale phenomena, including its inherent shear-thinning rheological flow behavior, the formation of a cell-depleted layer near the vessel walls, as well as the lateral migration of RBCs with impaired deformability, platelets, and white blood cells towards the vessel walls. In this project, we aim to advance our understanding of blood flow in the microcirculation by shedding light on margination and flow instabilities of RBC suspensions in-vitro microfluidic flows. A special emphasis will be set on the interplay between the rheological fluid properties of the suspension medium, i.e., viscoelasticity and shear-thinning, and the time-dependent driving of the flow. Particularly, we will focus on complex flow geometries such as contraction-expansion channels. Although the flow through a constriction expansion is considered a bench-mark geometry in classical fluid dynamics, little is known about the flow instabilities of complex fluids in such channels under time-dependent flow conditions. We will employ microfluidic experiments in combination with particle image velocimetry and particle tracking algorithms, as well as confocal microscopy, to investigate the in-vitro flow of RBC suspensions. To assess the rheological properties, we will first perform a detailed characterization of the shear and elongational fluid rheology. Subsequently, we will investigate the effect of viscoelasticity on margination of rigid RBCs using our recently developed tracking technique, which allows us to track individual cells along the channel flow direction under steady and unsteady flow conditions, thus revealing previously inaccessible long-range margination trajectories. Moreover, we will examine the flow of RBC suspensions through constricted microchannels, focusing on the vortex dynamics, the cell-free layer, and arising flow instabilities in such complex viscoelastic fluids. Besides these fundamental investigations, our results will provide a further understanding of the pivotal role of microfluidic constrictions in biomedical microfluidic applications for cell and plasma separation and the mimicry of constricted blood vessels.

• DFG Programme: Research Units
• Subproject of: FOR 2688: Instabilities, Bifurcations and Migration in Pulsatile Flows
• Ehemaliger Antragsteller: Dr.-Ing. Steffen Michael Recktenwald, until 1/2024