Assessment of Blood Biophysical Properties Using Pressure Sensing with Micropump and Microfluidic Comparator

Abstract

To identify the biophysical properties of blood samples consistently, macroscopic pumps have been used to maintain constant flow rates in a microfluidic comparator. In this study, the bulk-sized and expensive pump is replaced with a cheap and portable micropump. A specific reference fluid (i.e., glycerin solution [40%]) with a small volume of red blood cell (RBC) (i.e., 1% volume fraction) as fluid tracers is supplied into the microfluidic comparator. An averaged velocity (<Ur>) obtained with micro-particle image velocimetry is converted into the flow rate of reference fluid (Qr) (i.e., Qr = CQ × Ac × <Ur>, Ac: cross-sectional area, CQ = 1.156). Two control variables of the micropump (i.e., frequency: 400 Hz and volt: 150 au) are selected to guarantee a consistent flow rate (i.e., COV < 1%). Simultaneously, the blood sample is supplied into the microfluidic channel under specific flow patterns (i.e., constant, sinusoidal, and periodic on-off fashion). By monitoring the interface in the comparator as well as Qr, three biophysical properties (i.e., viscosity, junction pressure, and pressure-induced work) are obtained using analytical expressions derived with a discrete fluidic circuit model. According to the quantitative comparison results between the present method (i.e., micropump) and the previous method (i.e., syringe pump), the micropump provides consistent results when compared with the syringe pump. Thereafter, representative biophysical properties, including the RBC aggregation, are consistently obtained for specific blood samples prepared with dextran solutions ranging from 0 to 40 mg/mL. In conclusion, the present method could be considered as an effective method for quantifying the physical properties of blood samples, where the reference fluid is supplied with a cheap and portable micropump.

Red Blood Cell Sedimentation Index Using Shear Stress of Blood Flow in Microfluidic Channel

“…In previous studies [ 7 , 20 , 23 , 37 ], the RBC aggregation or sedimentation was quantified by analyzing the image intensity of the blood flow over time. Following such previous methods, as shown in Figure 3 C, the image intensity of the blood flow ( I b ) was obtained under a continuous blood flow ( Q b = 0.5 mL/h).…”

“…The time variation of I b is not distinct with respect to C dex . Based on the definition of the RBC aggregation index [ 37 ], the ESR index (ESI I ) was calculated using the temporal variations in I b . Figure 5 (Bii) shows the variations in ESR I with respect to C dex .…”

“…The shear stress of the test fluid increased with time. Referring to an RBC aggregation index reported in a previous study [ 7 , 37 ], the RBC sedimentation index was newly suggested as ESR τ = A /( A + B ). Based on the temporal variations in τ , A and B were calculated as A = and B = .…”

Contributions of Red Blood Cell Sedimentation in a Driving Syringe to Blood Flow in Capillary Channels

“…The junction pressure at a distance (L* = 3500 µm) from the outlet (or the ground) was denoted as P r (L*) for the reference fluid stream and P t (L*) for the test fluid stream. According to a previous study [27], the analytical expression for each junction pressure is given as:…”

Biosensing of Haemorheological Properties Using Microblood Flow Manipulation and Quantification

“…In this study, three haemorheological properties (i.e., viscosity, time constant, and RBC aggregation index) were obtained periodically by analysing blood flow, which was set to a square-wave profile. Based on the coflowing channel adapted for the measurement of blood viscosity [ 32 ], blood was injected periodically into a microfluidic device by turning the syringe pump on and off. To quantify blood viscosity, we supplied a reference fluid at a constant flow rate.…”