Blood Viscoelasticity Measurement Using Interface Variations in Coflowing Streams under Pulsatile Blood Flows

Abstract

Blood flows in microcirculation are determined by the mechanical properties of blood samples, which have been used to screen the status or progress of diseases. To achieve this, it is necessary to measure the viscoelasticity of blood samples under a pulsatile blood condition. In this study, viscoelasticity measurement is demonstrated by quantifying interface variations in coflowing streams. To demonstrate the present method, a T-shaped microfluidic device is designed to have two inlets (a, b), one outlet (a), two guiding channels (blood sample channel, reference fluid channel), and one coflowing channel. Two syringe pumps are employed to infuse a blood sample at a sinusoidal flow rate. The reference fluid is supplied at a constant flow rate. Using a discrete fluidic circuit model, a first-order linear differential equation for the interface is derived by including two approximate factors (F1 = 1.094, F2 = 1.1087). The viscosity and compliance are derived analytically as viscoelasticity. The experimental results showed that compliance is influenced substantially by the period. The hematocrit and diluent contributed to the varying viscosity and compliance. The viscoelasticity varied substantially for red blood cells fixed with higher concentrations of glutaraldehyde solution. The experimental results showed that the present method has the ability to monitor the viscoelasticity of blood samples under a sinusoidal flow-rate pattern.

Experimental Investigation of Air Compliance Effect on Measurement of Mechanical Properties of Blood Sample Flowing in Microfluidic Channels

“…To keep the mathematical model simple, the interface in the co-flowing channel was modeled as a virtual wall. Different boundary conditions between the real physical model and the mathematical model were compensated by adding a correction factor (C f ) into the governing equation [39]. Thus, both fluids in the co-flowing channel were modeled independently with discrete circuit elements.…”

“…Because of the nonlinear terms in the left member of Equation ( 1), the differential equation was difficult to solve substantially. Based on an approximate procedure [39], two approximate coefficients (F 1 , F 2 ) were obtained as F 1 = 1.112, F 2 = 1.129, respectively. Consequently, 1/(1-α) was converted into β and Equation ( 1) was transformed into a linear differential equation as follows:…”

Microfluidic Quantification of Blood Pressure and Compliance Properties Using Velocity Fields under Periodic On–Off Blood Flows

“…According to linear regression (i.e., R 2 = 0.9461), both methods had a strong correlation. Second, according to previous study [15], the compliance of the fixed RBCs was obtained by analyzing the interfacial location in the coflowing channel under sinusoidal blood flows. The equivalent compliance (C B ) was obtained with respect to C GA = 0, 4, 8, and 12 µL/mL.…”

“…Conventional micro-electromechanical system techniques were used to fabricate a four inch silicon mold. Based on a soft lithography process with PDMS (Sylgard 184, Dow Corning, Midland, MI, USA) [15], a PDMS block was fabricated from the silicon mold. Using an oxygen plasma system, the PDMS block was bonded to the glass slide.…”

“…More recently, the author has suggested the viscoelasticity measurement technique in dynamic varying flow conditions. First, by controlling the blood flow rate in the oscillatory pattern, the viscosity and elasticity can be obtained periodically by analyzing the interface in coflowing streams (i.e., blood stream, 1× phosphate-buffered saline (PBS) stream) [15]. Second, viscosity and elasticity can be obtained sequentially by monitoring reversal flow switching in a Wheatstone bridge circuit under a steady flow and transient flow.…”