Blood Cell Behavior in Hyperbolic Microchannels: Investigating the Cell Free Layer and Deformation

Microfluidic systems have been successfully used in diverse biomedical applications, owing to their multitude advantages. These systems excel in working with minimal sample volumes and with short assays times. Moreover, microfluidic systems allow parallel operations, facilitating tasks like separation and deformation measurement of individual cell/particles. In microfluidic devices, cells can be effectively separated using two main methods for cells separation: passive methods, which are based on microstructures and laminar flow, and active methods that are driven by external force fields. The preference for passive methodologies is evident in numerous studies, given their autonomy from the need for external forces. The primary aim of this study is to demonstrate the potential of employing microfluidic systems featuring hyperbolic microchannels for the separation of RBCs from plasma and to evaluate alterations in RBC deformability under physiological and pathological conditions, with a view to clinical applications. The protocol involves the initial separation of a specific quantity of RBCs from plasma, followed by deformability measurements on individual RBCs downstream. This research leverages soft lithography techniques to propose the design and fabrication of four distinct microfluidic devices, providing a foundation for comprehensive investigations into RBC deformability and its clinical implications. The results show that the hyperbolic contractions with a higher Hencky strain, significantly enhance the CFL downstream of the contraction region. Regarding the cell deformability, the measurements indicate that RBCs are highly deformable under strong extensional flows, with the extent of deformability closely linked to flow rates and deformability indices (DI). Another important feature is the implementation of numerical simulation, which offer insights into mesh settings, quality, and their alignment with experimental results, enhancing our understanding of the underlying phenomena. The endeavor to evaluate RBC deformability offers a strategic approach for the development of a straightforward, cost-effective, and user-friendly diagnostic tool for the detection and diagnosis of diseases related to red blood cells. The findings presented in this thesis underscore the efficacy of the hyperbolic microchannel as a viable method for integration into microfluidic systems, facilitating the continuous separation of cells from plasma.