Microfluidic-based effective monitoring of bloods by measuring RBC aggregation and blood viscosity under stepwise varying shear rates

To effectively discriminate changes in blood samples, RBCs aggregation and blood viscosity should be evaluated independently and simultaneously. In this study, by setting two syringe pumps for delivering two fluids (blood sample and reference fluid) at stepwise varying flow rates, RBCs aggregation (AI) and viscosity (µBlood) are sequentially measured by quantifying image intensity of blood flows (<I>) and interface between blood sample and reference fluid (αBlood) in microfluidic channels. The (<I>) for measuring AI was obtained at lower shear rate (γ̇ < 91.7 s-1). Additionally, αBlood for measuring µBlood was obtained at higher shear rates (γ̇ < 91.7 s-1). As a demonstration, the proposed method is employed to measure AI and µBlood for various blood samples composed of different concentrations of dextran solution or different degrees in RBCs deformability. After then, the method is employed to measure AI and µBlood of blood samples with respect to storage time of 25 days. As a result, RBCs aggregation and blood viscosity varied continuously up to 15 days of storage time. In conclusion, this method can be used effectively to detect changes in blood samples by measuring µmood and AI of blood samples simultaneously.