Visualization study of motion and deformation of red blood cells in a microchannel with straight, divergent and convergent sections

Abstract

The size of red blood cells (RBC) is on the same order as the diameter of microvascular vessels. Therefore, blood should be regarded as a two-phase flow system of RBCs suspended in plasma rather than a continuous medium of microcirculation. It is of great physiological and pathological significance to investigate the effects of deformation and aggregation of RBCs on microcirculation. In this study, a visualization experiment was conducted to study the microcirculatory behavior of RBCs in suspension. Motion and deformation of RBCs in a microfluidic chip with straight, divergent, and convergent microchannel sections have been captured by microscope and high-speed camera. Meanwhile, deformation and movement of RBCs were investigated under different viscosity, hematocrit, and flow rate in this system. For low velocity and viscosity, RBCs behaved in their normal biconcave disc shape and their motion was found as a flipping motion: they not only deformed their shapes along the flow direction, but also rolled and rotated themselves. RBCs were also found to aggregate, forming rouleaux at very low flow rate and viscosity. However, for high velocity and viscosity, RBCs deformed obviously under the shear stress. They elongated along the flow direction and performed a tank-treading motion.

Keywords: Microchannel; Microfluidic chip; Red blood cell; Visualization.

Fig. 1

Schematic of the experimental setup

Fig. 2

Microfluidic chip

Fig. 3

Test section of the microchannel

Fig. 4

Microchannel blocking and cleaning. a Channel blocking; b after cleaning

Fig. 5

RBCs aggregation in the microchannel (hematocrit: 1%, flow rate: 0.0046 ml/h)

Fig. 6

RBCs’ deformation under different flow rate and viscosity: a hematocrit 1%, flow rate 0.0046 ml/h, without PVP; b hematocrit 1%, flow rate 1.0 ml/h, with PVP

Fig. 7

Deformation process of RBCs’ passing though the convergent section of the channel

Fig. 8

Schematic diagram of RBCs’ rotation and rolling

Fig. 9

The rotation of RBC

Fig. 10

The rolling motion of RBC

Fig. 11

RBCs rotation near the channel wall

Fig. 12

RBCs rotation near centerline of the channel

Fig. 13

Tubular pinch effect of RBC at flow rate 1 ml/h: a hematocrit 8%, b hematocrit 10%, c hematocrit 15%

Fig. 14

Tubular pinch effect of RBC at flow rate 0.15 ml/h: a hematocrit 8%, b hematocrit 10%, c hematocrit 15%

Fig. 15

Tubular pinch effect of RBC at flow rate 0.012 ml/h: a hematocrit 8%, b hematocrit 10%, c hematocrit 15%