The advances made in the field of cardiovascular prostheses have proved invaluable in saving human lives. However, implanting such a device may cause unwanted results like thrombosis, the formation of blood clots inside blood vessels. This formation of thrombi can affect the flow of blood, which if left untreated may result in strokes. As the blood moves through various arteries and veins, the platelets move toward the periphery and the red blood cells (RBC) are more concentrated near the center. This process is called margination and has been shown by Aarts et al.[1]. The platelets in essence are policing the endothelial layer, and with any change in the endothelial layer, say as a result of injury, the platelets get activated, which in turn starts a domino effect eventually resulting in the formation of a clot to stop the bleeding. These platelets can also get activated due to their presence in regions of high shear as is the case when the blood is flowing through narrow constrictions (for example, when a mechanical heart valve is about to close). This phenomenon is referred to as Shear Induced Platelet Activation (SIPA)[2]. The goal of this research is to study the effect of constricted geometries, high shear rates and erythrocyte-platelet interactions on platelet activation and aggregate formation, events that are critical in the initiation of thrombosis. In order to understand SIPA, one must first obtain a detailed flow in these constricted geometries. Numerous studies have been performed to obtain the flow fields of blood flowing through microchannels [3, 4]. However, the Reynolds numbers based on the characteristic length of the microchannel were in the O (1). It is worth noting that for such laminar flows confocal particle image velocimetry can be successfully applied. In this present study, the Reynolds numbers were in the O (100), rendering confocal mPIV impractical and making Micro Particle Image Velocimetry (mPIV) a clear choice.

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