Title: MICROFLUIDIC METHODS FOR MEASUREMENT OF RED BLOOD CELL FLOW IN CONFINED SPACES
Joie N. Marhefka and Kalman B. Migler
Affiliation: Polymers Division, NIST Gaithersburg, MD 20899.
Measurement techniques are being explored for characterizing flow of red blood cells (RBCs) in confined spaces. Bulk rheology is not sufficient to characterize blood flow in microcirculation. As the blood vessel dimensions approach that of the RBCs, blood no longer follows the continuum model due to contributions from individual cell properties as well as uneven distribution of RBCs across the vessel. Therefore, microfluidic systems are being developed and applied as in vitro models of microvascular blood flow. These systems provide valuable information on blood rheology at the microvascular level and can be applied as tools for investigating the effects of various therapies or alterations in RBC properties on the microcirculation.
This study uses microscopic imaging methods to determine RBC velocity profiles and distributions in microfluidic devices having dimensions characteristic of the microcirculation. It has been shown that droplets (PIB in PDMS) sheared between parallel plates organize into discrete layers when droplet dimensions were comparable to gap width (Pathak et al, 2002). In addition, Thurston (1989) developed a theory that when flowing blood exceeds a critical strain (unit strain) RBCs align, releasing trapped plasma and forming multiple layers of plasma on which layers of RBCs slide. This theory was developed for bulk blood flow, but concept of cell alignment extends to flow in small gaps/channels. Experimental evidence to support this theory is lacking. Further understanding of the flow structure of RBCs in microfluidic devices will provide insight into blood flow in the microcirculation as well as scientific knowledge that could be useful in studying alterations in blood rheology as well as in the development of microfluidic devices.
 J.A. Pathak, M.C. Davis, S.D. Hudson, and K.B. Migler, Journal of Colloid and Interface Science, 255, 391-402, (2002)
 G.B. Thurston, Biorheology, 26, 199-214, (1989)
Mentors Name: Kalman Migler
Division, Laboratory: Polymers, MSEL
Room, Building Mail stop: A227, 224, MS 8542
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