Paper Number
PO116 

Session
Poster Session

Title
Cross-sectional focusing and vortex dynamics of red blood cells in a constricted microfluidic channel

Presentation Date and Time
October 23, 2019 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom C on 4th floor

Authors (Click on name to view author profile)

  1. Recktenwald, Steffen M. (Saarland University, Department of Experimental Physics)
  2. Abay, Asena (Saarland University, Department of Experimental Physics)
  3. John, Thomas (Saarland University, Department of Experimental Physics)
  4. Kaestner, Lars (Saarland University, Theoretical Medicine and Biosciences)
  5. Wagner, Christian (Saarland University, Department of Experimental Physics)

Author and Affiliation Lines (in printed abstract book)
Steffen M. Recktenwald1, Asena Abay1, Thomas John1, Lars Kaestner2, and Christian Wagner1
1Department of Experimental Physics, Saarland University, Saarbruecken 66123, Germany; 2Theoretical Medicine and Biosciences, Saarland University, Homburg 66424, Germany

Speaker / Presenter 
Recktenwald, Steffen M.

Text of Abstract
The cardiovascular system is a complex network of branching vessels that transport and distribute blood through our bodies. Blood vessels can exhibit complex geometries and cross-sections, such as sudden constrictions and expansions in stenosed arteries, that dramatically change the spatial distribution of passing cells or particles. To mimicking pathophysiological geometric blockages and obstructed vessels in the circulation, constricted microfluidic channels are commonly used to study the flow of red blood cell (RBC) suspensions. However, knowledge about the distribution of cells in the channel cross-section in non-confined flows is still missing, which can help to understand the unique flow properties of blood in microvessels and can improve high-throughput microfluidic cell sorting and plasma extraction.

Here, we experimentally probe the distribution and velocities of RBCs across the channel width as well as the channel depth in a sudden contraction-expansion geometry and demonstrate how the constriction dramatically affects the spatial cell distribution. Upstream of the contraction, RBCs are homogeneously dispersed in the channel cross-section. However, tracking individual RBCs in multiple planes across the channel depth reveals a strong focusing near the four channel faces post-contraction. Additionally, we observe cell-depleted zones in the channel center and close to the four corners of the channel cross-section. We discuss how this non-uniform spatial distribution of cells results in an apparent double-peaked velocity profile in particle image velocimetry measurements, providing a better understanding of the influence of geometry-induced focusing effects on velocimetry techniques. Covering a broad range of pressure drops demonstrates that this phenomenon arises above a critical Reynolds number. Further, we show that cell deformability influences the trapping of cells in the recirculation zones downstream of the contraction, highly relevant for biomedical cell-sorting applications.