Center for Biofluid and Biomimic Research, Pohang University of Science and Technology, Pohang, South Korea.
Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang, South Korea.
Biomicrofluidics. 2013 Oct 1;7(5):54111. doi: 10.1063/1.4823586. eCollection 2013.
Blood viscosity has been considered as one of important biophysical parameters for effectively monitoring variations in physiological and pathological conditions of circulatory disorders. Standard previous methods make it difficult to evaluate variations of blood viscosity under cardiopulmonary bypass procedures or hemodialysis. In this study, we proposed a unique microfluidic device for simultaneously measuring viscosity and flow rate of whole blood circulating in a complex fluidic network including a rat, a reservoir, a pinch valve, and a peristaltic pump. To demonstrate the proposed method, a twin-shaped microfluidic device, which is composed of two half-circular chambers, two side channels with multiple indicating channels, and one bridge channel, was carefully designed. Based on the microfluidic device, three sequential flow controls were applied to identify viscosity and flow rate of blood, with label-free and sensorless detection. The half-circular chamber was employed to achieve mechanical membrane compliance for flow stabilization in the microfluidic device. To quantify the effect of flow stabilization on flow fluctuations, a formula of pulsation index (PI) was analytically derived using a discrete fluidic circuit model. Using the PI formula, the time constant contributed by the half-circular chamber is estimated to be 8 s. Furthermore, flow fluctuations resulting from the peristaltic pumps are completely removed, especially under periodic flow conditions within short periods (T < 10 s). For performance demonstrations, the proposed method was applied to evaluate blood viscosity with respect to varying flow rate conditions [(a) known blood flow rate via a syringe pump, (b) unknown blood flow rate via a peristaltic pump]. As a result, the flow rate and viscosity of blood can be simultaneously measured with satisfactory accuracy. In addition, the proposed method was successfully applied to identify the viscosity of rat blood, which circulates in a complex fluidic network. These observations confirm that the proposed method can be used for simultaneous measurement of viscosity and flow rate of whole blood circulating in the complex fluid network, with sensorless and label-free detection. Furthermore, the proposed method will be used in evaluating variations in the viscosity of human blood during cardiopulmonary bypass procedures or hemodialysis.
血液粘度一直被认为是有效监测循环系统疾病生理和病理状态变化的重要生物物理参数之一。传统的标准方法很难评估心肺旁路手术或血液透析过程中血液粘度的变化。在这项研究中，我们提出了一种独特的微流控设备，用于同时测量包括大鼠、储液器、夹管阀和蠕动泵在内的复杂流体网络中循环的全血的粘度和流量。为了验证所提出的方法，精心设计了一种由两个半圆形腔室、两个带有多个指示通道的侧通道和一个桥接通道组成的双形状微流控装置。基于微流控装置，应用了三个连续的流量控制来实现对血液粘度和流量的无标记和无传感器检测。半圆形腔室用于实现微流控装置中的流动稳定的机械膜顺应性。为了量化流动稳定对流动波动的影响，使用离散流体电路模型推导出脉动指数（PI）的公式。使用 PI 公式，估计半圆形腔室贡献的时间常数约为 8 s。此外，周期性流动条件下（T < 10 s），蠕动泵引起的流动波动完全消除，尤其是在短时间内。为了进行性能演示，将所提出的方法应用于评估不同流量条件下的血液粘度[（a）通过注射器泵的已知血流率，（b）通过蠕动泵的未知血流率]。结果，能够以令人满意的准确度同时测量血液的流量和粘度。此外，成功地将所提出的方法应用于识别在复杂流体网络中循环的大鼠血液的粘度。这些观察结果证实，所提出的方法可用于同时测量复杂流体网络中循环的全血的粘度和流量，并且具有无标记和无传感器检测。此外，所提出的方法将用于评估心肺旁路手术或血液透析过程中人类血液粘度的变化。
