Enhancing cell-free layer thickness by bypass channels in a wall

Area of Science:

• Biomedical Engineering
• Fluid Dynamics
• Cellular Mechanics

Background:

• Red blood cells (RBCs) naturally form a cell-free layer (CFL) near walls during blood flow.
• Controlling CFL thickness is crucial for preventing unwanted cell adhesion in biomedical device design.
• Existing designs lack sufficient control over CFL formation, posing challenges for device efficacy.

Purpose of the Study:

• To investigate a novel wall configuration featuring stenoses and bypass channels to enhance CFL thickness.
• To determine the impact of bypass channel geometry and hematocrit (Hct) on CFL modulation.
• To elucidate the underlying flow dynamics responsible for CFL enhancement using numerical simulations.

Main Methods:

• Computational fluid dynamics (CFD) simulations were employed to model blood flow through the novel wall geometry.
• Varying hematocrit levels (5%, 10%, 20%) were simulated to assess CFL response.
• Analysis of streamline distribution and RBC size relative to stenosis geometry was performed.

Main Results:

• The proposed wall configuration with bypass channels significantly increased CFL thickness downstream of stenoses.
• A single bypass channel increased CFL thickness by 1.7μm at 5% Hct; three bypass channels increased it by 3μm.
• CFL enhancement was observed up to 10% Hct, with diminishing effects at 20% Hct.
• Numerical simulations identified the streamline-to-stenosis corner distance relative to RBC size as a key regulatory parameter.

Conclusions:

• Novel wall configurations with bypass channels effectively enhance CFL thickness, offering a new strategy for biomedical device design.
• The findings provide a mechanistic understanding of CFL modulation, linking flow field characteristics to RBC behavior.
• This approach holds significant potential for preventing cell adhesion and improving the performance of blood-contacting medical devices.