Book Description

Continuous multidisciplinary advancements in medicine, science and engineering have led to the rise of biomedical microfluidic devices for clinical diagnoses, laboratory research for modeling and screening of drugs or disease states, and implantable organs such as artificial kidneys. Blood is often the biological fluid of choice for these purposes. However, unique hemodynamic properties observed only in microscale channels complicate experimental repeatability and reliability. For vessels with 10-300μm diameters, red blood cell properties such as deformability have a significant impact on hemorheology, and the blood can no longer be considered as a homogeneous fluid. The flowing blood segregates into a red blood cell rich core bounded by a cell-free layer composed almost entirely of plasma. Viscous forces dominate flow behavior, and shear rates at the wall are much higher than in arteries and veins. The overall viscosity becomes dependent on vessel diameter. These unique characteristics are interesting from a biophysics perspective, but the value of biomedical microfluidic technologies makes research in this regime even more critical. Accordingly, this work focuses on experimental comparison of the microfluidic flow properties of red blood cells with varying physical characteristics. Blood viscosity in microscale tubes was investigated experimentally for 6 blood types (goat, sheep, pig, llama, chicken and turkey) at a range of hematocrits (0-50%). The selected blood types represented a small sample of the wide-ranging red blood cell characteristics found in mammals, birds, reptiles, amphibians and fish. These red blood cells vary in size over an order of magnitude, represent shapes ranging from biconcave to ellipsoidal, and include both nucleated cell types found in birds, amphibians and reptiles and denucleated mammalian cells. Pressure drop experiments at physiologically relevant flow rates were carried out for rigid tubing diameters ranging from 73μm - 161μm. The resulting viscosities were normalized relative to the measurements made of the homologous plasma for each species. The viscosity of blood in this regime is much different than in larger vessels (>500μm) or in small capillaries (