Blood Velocity Profile Measurements in Microchannels Using Micro-particle Image Velocimetry

Experimental studies of blood microflows in rectangular biocompatible polymer microchannels measured using micro-particle image velocimetry are reported. The data processing methods, data collection methods, and choice of channel material are demonstrated to impact the velocity profile measurements obtained. Results show that the use of red blood cells as tracer particles creates a large depth of correlation which can approach the size of the vessel itself and decrease the accuracy of the method. It is shown that changing the amount of overlap in the post-processing parameters affects the results by nearly 10%. The velocity profile is studied as a function of the flow rate of the blood, the hematocrit, or percentage of red blood cells, the shape of the channel, and the channel material. The results highlighted here show that the best processing options include pre-processing, the use of fluorescent tracer particles instead of the red blood cells themselves as tracers give a more accurate prediction of the profile, and the use of silicone as the channel material more closely mimics the behavior of physiology. Acrylic biocompatible polymer channels are shown to give a more parabolic profile at lower levels of hematocrit, while silicone biocompatible polymer channels give a velocity profile that looks more like in vivo flow studies. INTRODUCTION Microcirculation is the range of blood vessels, generally around 100 μm or less, where the Reynolds and Womersley numbers are significantly less than unity, and the viscous stress and pressure gradient are the main determinations of flow. Blood is a non-homogeneous fluid, and this complex composition and environment makes characterization of the blood at the micro level difficult. As lab-on-a-chip and medicine move to the micro level, this characterization becomes important, especially velocity profile characterization. First, we will discuss the accuracy of measurement method before discussing the physical parameters influencing the velocity profile. Blood flow measurements in microflow, such as maximum velocity and the shape of the velocity profile, can be achieved through micro-particle image velocimetry (μPIV). Generally, for in vivo studies red blood cells (RBCs) are used as tracer particles for the μPIV method, while for in vitro studies, artificial fluorescent micro particles are added to the blood. Microcirculation is of current basic science and clinical interest. Microcirculation regulates the exchange between blood and tissues via vascular beds both in and around organs [1]. Recognizing the characteristics of blood flow in microcirculation is essential in order to understand the mechanical interactions between the blood and the vessel Proceedings of the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels ICNMM2012 July 8-12, 2012, Rio Grande, Puerto Rico