Quantitative Measurement and Evaluation of Red Blood Cell Aggregation in Normal Blood Based on a Modified Hanai Equation

2020

Micromachines

Air compliance has been used effectively to stabilize fluidic instability resulting from a syringe pump. It has also been employed to measure blood viscosity under constant shearing flows. However, due to a longer time delay, it is difficult to quantify the aggregation of red blood cells (RBCs) or blood viscoelasticity. To quantify the mechanical properties of blood samples (blood viscosity, RBC aggregation, and viscoelasticity) effectively, it is necessary to quantify contributions of air compliance to dynamic blood flows in microfluidic channels. In this study, the effect of air compliance on measurement of blood mechanical properties was experimentally quantified with respect to the air cavity in two driving syringes. Under periodic on–off blood flows, three mechanical properties of blood samples were sequentially obtained by quantifying microscopic image intensity (<I>) and interface (α) in a co-flowing channel. Based on a differential equation derived with a fluid circuit model, the time constant was obtained by analyzing the temporal variations of β = 1/(1–α). According to experimental results, the time constant significantly decreased by securing the air cavity in a reference fluid syringe (~0.1 mL). However, the time constant increased substantially by securing the air cavity in a blood sample syringe (~0.1 mL). Given that the air cavity in the blood sample syringe significantly contributed to delaying transient behaviors of blood flows, it hindered the quantification of RBC aggregation and blood viscoelasticity. In addition, it was impossible to obtain the viscosity and time constant when the blood flow rate was not available. Thus, to measure the three aforementioned mechanical properties of blood samples effectively, the air cavity in the blood sample syringe must be minimized (Vair, R = 0). Concerning the air cavity in the reference fluid syringe, it must be sufficiently secured about Vair, R = 0.1 mL for regulating fluidic instability because it does not affect dynamic blood flows.

Section: Introductionmentioning

confidence: 99%

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

2020

Micromachines

“…These alterations contribute to a reduction of mass transport and interrupt the blood flow in capillary vessels. To effectively detect changes in blood samples from a physical point of view, several rheological properties (i.e., viscosity [ 3 , 4 , 5 , 6 ], viscoelasticity [ 7 ], red blood cell (RBC) deformability [ 8 , 9 , 10 , 11 , 12 , 13 ], RBC aggregation [ 14 , 15 , 16 , 17 ], RBC sedimentation rate [ 18 , 19 ], and Hct [ 20 ]) have been measured for screening or diagnosing various diseases, including coronary heart disease, hypertension, diabetes [ 21 ], sickle cell anemia [ 22 , 23 ], and malaria. Plasma protein (i.e., fibrinogen) contributes to increasing RBC aggregation.…”

Section: Introductionmentioning

confidence: 99%

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

2022

Micromachines

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.

“…Several techniques have been applied to quantify RBC aggregation or the ESR, including those based on electrical impedance [ 5 , 12 , 13 , 14 , 15 ], optical light intensity [ 7 , 16 , 17 ], microscopic image intensity [ 18 , 19 ], interface detection in the tube [ 11 , 20 , 21 ], a holographic laser tweezer [ 6 ], and the shear stress in microfluidic device [ 22 ]. Additionally, an external mechanism (e.g., a pinch valve [ 16 ], vibration motor [ 7 ], driving syringe [ 20 ], or vacuum pump [ 22 ]) can be adopted to periodically run or stop the blood flow in a microfluidic channel.…”

Section: Introductionmentioning

confidence: 99%

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

2022

Biosensors

Red blood cell sedimentation has been used as a promising indicator of hematological diseases and disorders. However, to address several issues (i.e., syringe installation direction, blood on-off flow control, image-based quantification, and hemodilution) raised by the previous methods, it is necessary to devise a new method for the effective quantification of red blood cell sedimentation under a constant blood flow. In this study, the shear stress of a blood flow is estimated by analyzing an interface in a co-flowing channel to quantify the red blood cell sedimentation in blood syringes filled with blood (hematocrit = 50%). A red blood cell sedimentation index is newly suggested by analyzing the temporal variations in the shear stress. According to the experimental investigation, the sedimentation index tends to decrease at a higher flow rate. A higher level of hematocrit has a negative influence on the sedimentation index. As a performance demonstration of the present method, the red blood cell sedimentation processes of various test bloods were quantitatively compared in terms of the shear stress, image intensity, and sedimentation velocity. It was found that the proposed index provided a more than 10-fold increase in sensitivity over the previous method (i.e., image intensity). Additionally, it provided more consistent results than another conventional sedimentation method (sedimentation velocity). In conclusion, the present index can be effectively adopted to monitor the red blood cell sedimentation in a 10-min blood delivery.