Microfluidic Chip for Quantitatively Assessing Hemorheological Parameters

The biomechanical properties of blood are regarded as promising biomarkers for monitoring early-stage abnormalities and disease progression. To detect any changes in blood, it is necessary to measure as many rheological properties as possible. Herein, a novel method is proposed for measuring multiple rheological properties of blood using a microfluidic chip. The syringe pump turns off for 5 min to induce RBC (red blood cell) sedimentation in the driving syringe. RBC aggregation is determined by analyzing the time-lapse blood image intensity at stasis: <i>I</i>(<i>t</i>) = <i>I</i>₁ exp (-<i>k</i>₁<i>t</i>) + <i>I</i>₂ exp (-<i>k</i>₂<i>t</i>). RBC-rich blood and RBC-depleted blood are sequentially infused into the microfluidic chip. Based on blood pressure estimated with time-lapse blood velocity, blood viscosity is acquired with the Hagen-Poiseuille law. RBC sedimentation is quantified as RBC sedimentation distance (<i>X_esr</i>) and erythrocyte sedimentation rate (ESR). The proposed method provides a consistent viscosity compared with previous methods. Two of the four variables (<i>I</i>₁, <i>I</i>₂) exhibited a strong correlation with the conventional RBC aggregation index (AI). The indices <i>X_esr</i> and ESR showed consistent trends with respect to the blood medium and hematocrit. In conclusion, the proposed method is then regarded as effective for monitoring multiple rheological properties.