## 3 Results and Discussion
### Quantitative Comparison of the Present Method and Previous Method
(**B**) Variations of \(\lambda_{\text{{off}}}\) and \(C_{eq}\) with respect to \(C_{GA}\). (**C**) Variations of \(G_{B}\) with respect to \(C_{GA}\). (**D**) Linear relationship between \(C_{eq}\) and \(G_{B}\). (_PI_) was calculated as \(PI=\frac{1}{I_{s}}\int_{I_{0}}^{I_{0}+I_{s}}I_{pc}dt\), with the image intensity of blood sample (\(I_{PC}\)) collected in the pressure channel with the large area. The variations of _PI_ were obtained with respect to \(C_{GA}=0\), 4, 6, and 8 \(\upmu\)L/mL. Here, the flow rate of the blood sample was fixed at 2 mL/h with a single syringe pump. The method had the ability to measure variations of blood pressure. Figure 7(A-a) shows variations of two blood-pressure-related indices obtained with the present method (\(\beta\)) and previous method (_PI_), respectively; \(\beta\) and _PI_ tended to increase with respect to \(C_{GA}\). Figure 7(A-b) shows the correlation between \(\beta\) and _PI_. 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 \(\upmu\)L/mL. Here, two syringe pumps were used to supply the blood sample and reference fluid into a microfluidic channel. The flow rates of the blood sample (\(Q_{B}\)) and 1x PBS (\(Q_{P}\)) were set to \(Q_{B}=1+0.5\) sin (2\(\upmu\)t/360) mL/h and \(Q_{P}=1\) mL/h, respectively. Figure 7(B-a) shows two compliance values obtained with the present method (\(C_{eq}\)) and previous method (\(C_{B}\)) with respect to \(C_{GA}\). Differences in microfluidic system contributed to differences in compliance. However, both methods exhibited similar trends with respect to \(C_{GA}\). As the GA solution contributed to decreasing the deformability of RBCs, it was reasonable that both compliance values tended to decrease with respect to \(C_{GA}\). As shown in Figure 7(B-b), the correlation between \(C_{eq}\) and \(C_{B}\) was represented by drawing the \(X\)-\(Y\) plot. From the linear regression analysis (i.e., \(R^{2}=0.8409\)), the present method (\(C_{eq}\)) showed consistent trends when compared with the previous method (\(C_{B}\)). From the quantitative comparison, this led to the conclusion that the present method (\(\beta\), \(C_{eq}\)) can be used to obtain variations of blood pressure and compliance effectively when compared with the previous method (_PI_, \(C_{B}\)). From the experimental results, it was found that the two properties suggested with the present method (i.e., \(P_{x}\) and \(C_{eq}\)) had strong correlations when compared with the two properties suggested in the previous method (i.e., \(\mu_{B}\) and \(G_{B}\)). Thus, while supplying the blood sample with a single syringe  
Figure 7: Quantitative comparison between the present method (\(\beta\)) and previous method (_PI_). (**A**) Comparison of blood-pressure-related indices (\(\beta\), _PI_). (**a**) Variations of \(\beta\) and _PI_ with respect to \(C_{GA}\). (**b**) Correlation between \(\beta\) and _PI_. (**B**) Comparison of the compliance obtained with the present method (\(C_{eq}\)) and previous method (\(C_{B}\)). (**a**) Variations of \(C_{eq}\) and \(C_{B}\) with respect to \(C_{GA}\). (**b**) Correlation between \(C_{eq}\) and \(C_{B}\). pump, the present method could be effectively employed to monitor mechanical variations of blood samples in a periodic on-off fashion. According to Figures 5 and 6, the blood pressure proposed in this study was proportional to blood viscosity. In addition, compliance and elasticity exhibited a linear relationship. From the results, it was inferred that the two mechanical properties (i.e., blood pressure and compliance) could be used interchangeably as conventional properties, such as blood viscosity and elasticity.