Cross-sectional focusing of red blood cells in a constricted microfluidic channel

Abstract

Constrictions in blood vessels and microfluidic devices can dramatically change the spatial distribution of passing cells or particles and are commonly used in biomedical cell sorting applications. However, the three-dimensional nature of cell focusing in the channel cross-section remains poorly investigated. Here, we explore the cross-sectional distribution of living and rigid red blood cells passing a constricted microfluidic channel by tracking individual cells in multiple layers across the channel depth and across the channel width. While cells are homogeneously distributed in the channel crosssection pre-contraction, we observe a strong geometry-induced focusing towards the four channel faces post-contraction. The magnitude of this cross-sectional focusing effect increases with increasing Reynolds number for both living and rigid red blood cells. We discuss how this non-uniform cell distribution downstream of the contraction results in an apparent double-peaked velocity profile in particle image velocimetry analysis and show that trapping of red blood cells in the recirculation zones of the abrupt construction depends on cell deformability.

Dual shape recovery of red blood cells flowing out of a microfluidic constriction

“…The implementation of a geometrical constriction has been demonstrated to focus cells towards the centerline of the device when the width of the channel is subsequently increased. 26,27 . Finally, in order to obtain a single file of cells, Tsai et al have used a 4.5µm wide and 30 µm long geometrical restriction with a width to center RBCs and align them so they would enter the evaluation zone on the same streamline 28 .…”

Effect of Temperature and Flow Rate on the Cell-Free Area in the Microfluidic Channel

“…Faiver et al (2006) also found that using a contraction-expansion channel had a high impact on the CFA formation [21]. Abay et al (2020) use a constricted channel to focus 4% of RBCs suspended in PBS [34]. They observed no inertial focusing before the contraction, but the focusing effect was observed due to the narrow section, increasing the velocity.…”

Optimizing pressure-driven pulsatile flows in microfluidic devices

“…We use two commercial pressure controllers, the Elveflow OB1-MK3 and the Fluigent Flow-EZ, to drive fluid through a microfluidic device. Both pressure devices have been used in various microfluidic studies 11,12,[20][21][22][23] and are referred to as OB1 pump and as Flow-EZ pump throughout this study. The pressure controller outlet is connected to a 1.5 mL tube containing the fluid sample.…”