Quantification of Blood Viscoelasticity under Microcapillary Blood Flow

Area of Science:

• Biomedical Engineering
• Microfluidics
• Rheology

Background:

• Quantifying blood elasticity is crucial for understanding pulsatile blood flow.
• Existing single-compliance models are significantly influenced by microfluidic system properties (e.g., soft channels, flexible tubing).
• This limitation hinders accurate assessment of intrinsic blood viscoelasticity.

Purpose of the Study:

• To develop a novel method for disentangling blood viscoelasticity from microfluidic system compliance.
• To introduce two distinct compliance coefficients: one for the microfluidic system (C1) and one for red blood cell (RBC) elasticity (C2).
• To enable more accurate measurements of blood viscoelasticity independent of the measurement device.

Main Methods:

• Utilized a coflowing microfluidic channel for blood viscoelasticity estimation.
• Derived a governing equation for the interface using fluidic circuit modeling and solved it analytically.
• Employed nonlinear curve fitting to determine the two compliance coefficients (C1 and C2).

Main Results:

• The ratio of RBC elasticity to microfluidic system compliance (C2/C1) was estimated between 10.9 and 20.4, varying with channel depth.
• Polydimethylsiloxane (PDMS) channel depth increased both compliance coefficients; outlet tubing decreased C1.
• Both compliance coefficients and blood viscosity showed significant variations with homogeneous versus heterogeneous hardened RBCs.

Conclusions:

• The proposed two-compliance coefficient method effectively distinguishes blood viscoelasticity from microfluidic system effects.
• This technique can accurately detect changes in blood properties and microfluidic systems.
• Future applications include the detection of red blood cell subpopulations in patient blood samples.