Abstract
When quantifying mechanical properties of blood samples flowing in closed fluidic circuits, blood samples are collected at specific intervals. Centrifugal separation is considered as a required procedure for preparing blood samples. However, the use of centrifuge is associated with several issues, including the potential for red blood cell (RBC) lysis, clotting activation, and RBC adhesions in the tube. In this study, an ultrasonic transducer is employed to separate RBCs or diluent from blood sample. The ultrasonic radiation force is much smaller than the centrifugal force acting in centrifuge, it can avoid critical issues occurring under centrifuge. Then, the RBC aggregation and blood viscosity of the blood sample are obtained using the microfluidic technique. According to the numerical results, ultrasonic transducers exhibited a maximum quality factor at an excitation frequency of 2.1 MHz. Periodic pattern of acoustic pressure fields were visualized experimentally as a column mode. The half wavelength obtained was as 0.5 λ = 0.378 ± 0.07 mm. The experimental results agreed with the analytical estimation sufficiently. An acoustic power of 2 W was selected carefully for separating RBCs or diluent from various blood samples (i.e., Hct = 20% ~ 50%; diluent: plasma, 1x phosphate-buffered saline (PBS), and dextran solution). The present method was employed to separate fixed blood samples which tended to stack inside the tube while using the centrifuge. Fixed RBCs were collected easily with an ultrasonic transducer. After various fixed blood samples with different base solutions (i.e., glutaraldehyde solution, 1x PBS, and dextran solution) were prepared using the present method, RBC aggregation and the viscosity of the blood sample are successfully obtained. In the near future, the present method will be integrated into ex vivo or in vitro fluidic circuit for measuring multiple mechanical properties of blood samples for a certain longer period.
Highlights
To monitor the mechanical properties of blood samples flowing under an extracorporeal rat bypass loop [1,2], blood samples are collected at specific intervals
When an AC potential was applied to the piezo resonator, the dynamic behavior of the ultrasonic transducer system was estimated as the electrical admittance with respect to frequency (f ) [20]
The results indicated that the acoustic power contributed to accelerating red blood cell (RBC)-to-liquid separation accelerating RBC-to-liquid separation significantly
Summary
To monitor the mechanical properties of blood samples flowing under an extracorporeal rat bypass loop [1,2], blood samples are collected at specific intervals. The repetitive collection of blood sample results in decreasing the volume of blood flowing in the circuit substantially. To maintain a fixed blood volume, 1x phosphate-buffered saline (PBS) is infused. The hemodilution procedure leads to significantly change mechanical properties of blood samples (i.e., blood viscosity, hematocrit, and pressure) [3]. Experimental tests have been limited to durations less than 2 h. The use of different blood storage techniques have led to large variations in the mechanical properties of Sensors 2020, 20, 2284; doi:10.3390/s20082284 www.mdpi.com/journal/sensors
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