Human red blood cell behavior under homogeneous extensional flow in a hyperbolic-shaped microchannel

Abstract

It is well known that certain pathological conditions result in a decrease of red blood cells (RBCs) deformability and subsequently can significantly alter the blood flow in microcirculation, which may block capillaries and cause ischemia in the tissues. Microfluidic systems able to obtain reliable quantitative measurements of RBC deformability hold the key to understand and diagnose RBC related diseases. In this work, a microfluidic system composed of a microchannel with a hyperbolic-shaped contraction followed by a sudden expansion is presented. We provide a detailed quantitative description of the degree of deformation of human RBCs under a controlled homogeneous extensional flow field. We measured the deformation index (DI) as well as the velocity of the RBCs travelling along the centerline of the channel for four different flow rates and analyze the impact of the particle Reynolds number. The results show that human RBC deformation tends to reach a plateau value in the region of constant extensional rate, the value of which depends on the extension rate. Additionally, we observe that the presence of a sudden expansion downstream of the hyperbolic contraction modifies the spatial distribution of cells and substantially increases the cell free layer (CFL) downstream of the expansion plane similarly to what is seen in other expansion flows. Beyond a certain value of flow rate, there is only a weak effect of inlet flow rates on the enhancement of the downstream CFL. These in vitro experiments show the potential of using microfluidic systems with hyperbolic-shaped microchannels both for the separation of the RBCs from plasma and to assess changes in RBC deformability in physiological and pathological situations for clinical purposes. However, the selection of the geometry and the identification of the most suitable region to evaluate the changes on the RBC deformability under extensional flows are crucial if microfluidics is to be used as an in vitro clinical methodology to detect circulatory diseases. V C 2013 AIP Publishing LLC. [http://dx

In vitro blood flow and cell-free layer in hyperbolic microchannels: Visualizations and measurements

“…Experiments with different flow rates (5 and 15 μL/min) were also performed. The results corroborate with past studies 6,11 were they found that flow rate has a weak effect on the downstream CFL. Additionally, Figure 4 shows that the highest CFLs thickness occur at microchannels with a εH of 3.6 and 4.2.…”

“…The present results corroborate the study performed by Yaginuma et al (2013) 11 , where by using a single hyperbolic contraction with a εH = 3, they have showed that for this particular hyperbolic contraction the downstream CFL enhanced by nearly ten times relatively to the CFL upstream of contraction region.…”

“…In contrast, with the work performed by Yaginuma and co-workers 11 , in this study we have used hyperbolic contractions with different Hencky strains (εH), which is defined as: εH = ln (width of the channel/width of the throat). Hence, the current work has performed, for the first time, in vitro blood experiments in hyperbolic-shaped microchannels with different Hencky strains, in order to assess the effect of the extensional flow on the CFL thickness.…”

“…It is of great importance to understand the behaviour of the CFL in microcirculation as it contributes to the rheological properties of blood flowing in microvessels. In this context, Yaginuma et al (2013) 11 demonstrated that microfluidic devices, composed of a hyperbolic contraction followed by an abrupt expansion, are able to perform separation of RBCs from plasma. Hence, the main objective of this work is to perform a more detailed investigation on the effect of the extensional flow field in the formation of the CFL in microfluidic devices.…”

Measuring Cell Viscoelastic Properties Using a Microfluidic Extensional Flow Device

“…To address these issues, microfluidic tools have recently been explored as a strategy to measure cellular structural and mechanical properties with a rapidity that may be better suited to drug discovery and clinical application (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Although these approaches have indeed massively improved measurement throughput and reduced operator skill/bias issues relative to traditional measurements, the extraction of cell mechanical properties (e.g., elastic modulus) remains challenging, primarily due to complex viscous forces that severely complicate analysis of deformations.…”