Continuous Separation of White Blood Cells From Whole Blood Using Viscoelastic Effects

White blood cells (WBCs) are the only cellular constituent containing genetic materials, and, hence, are candidate biomarkers for a host of diseases. However, conventional methods for WBC separation tend to have low sample purity and separation efficiency, which will have adverse implications on downstream polymerase chain reaction (PCR) analyses. In this study, we introduce a two-stage microfluidic device which harnesses the elastic property of a non-Newtonian fluid for size-based separation of WBCs from whole blood. The device displayed high resolution and efficiency in separating polystyrene particles and blood cells of different sizes up to a flow rate of 150 μL/min in polyvinylpyrrolidone solutions. We performed a separate parametric study to evaluate the effects of the fluid elasticity and flow rate on the separation performance. The hematocrit of the blood sample was varied from 0.01% to 20% to investigate the effect of increased intercellular interactions on the separation efficiency. An optimized set of parameters was selected to demonstrate the applicability of the device to the separation of WBCs from diluted whole blood, with excellent efficiency and purity (>90%). This microfluidic device will be especially useful for blood fractionation applications requiring high sample purity and speedy processing. Additionally, the apparent flow-rate insensitivity of the separation allows for its potential use in point-of-care applications.