Figure 2. Features of inertio-elastic focusing based on individual particles.

(a) Representative fluid velocity field along the channel determined from a correlative µ-PIV technique. (b) Cross-sectional particle histogram of 8-µm particles in a lower quadrant of the square cross-section channel at Q = 0.09 ml min⁻¹ and at Q = 6.0 ml min⁻¹. (c) Velocity profiles measured in the two fluids (red and blue curves respectively) and the corresponding velocities of the migrating 8-µm beads (black dots for beads in water and violet dots for beads in the HA solution) measured at the channel mid-plane (y = 0 µm). Note that at Q = 0.09 ml min⁻¹ in water, the particles occupy off-center equilibrium positions with fourfold symmetry. The particles that appear to be located at z = 0 in Fig. 2c are projections of particles located around y ≈ ± 25 µm. For comparison, the expected velocity profiles at the mid-plane of the channel (that is, y = 0 µm) for the flow of a Newtonian fluid and a shear thinning Carreau model (determined from COMSOL simulations) are shown by the green and gold curves, respectively. The s.d. in the velocity measurements are shown by the error bars in u_x, and the width of the interrogation windows are shown by the error bars along the z-axis.