Numerical study of the effect of rectangular cross-sections in straight channels on particle migration in inertial particle microfluidics
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Inertial particle microfluidics (IPMF) is a technique that is used to manipulate cells and particles on the microscale, for industrial1 or disease diagnosis2 applications, by focusing cells and particles to lateral positions across the channel cross-section called equilibrium positions. IPMF is a passive technique which, aside from a pump to generate a flow inside the device, solely relies on the intrinsic hydrodynamic forces3. Two key forces in IPMF are the wall lift force and the shear gradient lift force, influenced by several parameters, such as the Reynolds number, particle confinement (particle size relative to the channel size), and shape of the velocity profile. The velocity profile is determined by the shape of the channel cross-section. Changing any of the parameters mentioned can lead to variations in the number and location of equilibrium positions of the particles. In a straight channel, changing the cross-sectional shape from square to rectangular can reduce the number of equilibrium positions. However, the detailed mechanism of this transition is not well understood. In our study, we employ a 3D immersed-boundary-lattice-Boltzmann method to numerically analyse the dynamics of a single particle, including its migration paths and equilibrium positions, over a range of Reynolds number and channel aspect ratio. We demonstrate how the migration path, and the number and location of equilibrium positions depend on particle size, geometry and Reynolds number.
