Abstract
Viscoelastic fluid flow-induced cross-streamline migration has recently received considerable attention because this process provides simple focusing and alignment over a wide range of flow rates. The lateral migration of particles depends on the channel geometry and physicochemical properties of particles. In this study, digital in-line holographic microscopy (DIHM) is employed to investigate the lateral migration of human erythrocytes induced by viscoelastic fluid flow in a rectangular microchannel. DIHM provides 3D spatial distributions of particles and information on particle orientation in the microchannel. The elastic forces generated in the pressure-driven flows of a viscoelastic fluid push suspended particles away from the walls and enforce erythrocytes to have a fixed orientation. Blood cell deformability influences the lateral focusing and fixed orientation in the microchannel. Different from rigid spheres and hardened erythrocytes, deformable normal erythrocytes disperse from the channel center plane, as the flow rate increases. Furthermore, normal erythrocytes have a higher angle of inclination than hardened erythrocytes in the region near the side-walls of the channel. These results may guide the label-free diagnosis of hematological diseases caused by abnormal erythrocyte deformability.
Highlights
A detailed understanding of the transport processes of particles or cells in flowing fluids is important for various industrial and biomedical applications
The biochemical and mechanical properties of erythrocytes are highly sensitive to the stages of various hematological diseases[25]
An elastic aqueous solution of poly(vinyl pyrrolidone) (PVP) with a constant viscosity was used as the suspending medium, and hardened erythrocytes were prepared by formalin treatment
Summary
Yang et al.[48] investigated the lateral migrations of deformable and rigid particles in viscoelastic fluid flow of square microchannel. Rigid spherical particles and both hardened and normal erythrocytes commonly migrate along the depthwise direction (z-axis) and focus in the channel center plane even at low Re conditions. The deformation of normal erythrocytes adversely affects the focusing in the mid-plane of the rectangular channel under a high flow rate condition of Q ≥ 10 μL/min (Fig. 2d). The flow-induced migrations of rigid spherical particles and normal and hardened erythrocytes in the rectangular microchannel flows of a viscoelastic fluid (PVP solution) were experimentally investigated using DIHM. This technique enables the acquisition of accurate information on 3D positions and orientations of such particles in the microchannel. These results can be used to design microfluidic devices for deformability-based cell separation and develop diagnostic tools for hematological diseases
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