Figure 4.

Sensitivity of the microfluidic platform to hematocrit. Venous whole blood anticoagulated with a bivalent direct thrombin inhibitor (hirudin) was subjected to a series of centrifugation steps to isolate RBCs and platelet-poor plasma (PPP) fractions. The RBC pellet was resuspended with autologous PPP to specified levels of hematocrit and samples were perfused through BSA-coated microfluidic devices. (a) Representative ‘voltage vs. reaction time’ curves of real-time progression of resuspended RBCs at select hematocrits within the microfluidic device are shown, with ‘PPP alone’, which has a hematocrit of zero, used as a control. The dashed arrows indicate calculation of empirical time constant values (${\tau }_{H_x}$) for samples with increasing hematocrits. (b) Plot of empirical ${\tau }_{H_x}$ values for samples with select hematocrit content is shown as mean ± SD, n ≥ 3. Single experimental data points are compared with approximated ${\tau }_{H_x}$ values from Fig. 3 (dashed lines: Approximation 1—grey, Approximation 2—black). The normal hematocrit range for men (40–54%) and women (36–48%) is highlighted in grey.