Particle Shape Influences Settling and Sorting Behavior in Microfluidic Domains

Abstract

We present a new numerical model to simulate settling trajectories of discretized individual or a mixture of particles of different geometrical shapes in a quiescent fluid and their flow trajectories in a flowing fluid. Simulations unveiled diverse particle settling trajectories as a function of their geometrical shape and density. The effects of the surface concavity of a boomerang particle and aspect ratio of a rectangular particle on the periodicity and amplitude of oscillations in their settling trajectories were numerically captured. Use of surrogate circular particles for settling or flowing of a mixture of non-circular particles were shown to miscalculate particle velocities by a factor of 0.9–2.2 and inaccurately determine the particles’ trajectories. In a microfluidic chamber with particles of different shapes and sizes, simulations showed that steady vortices do not necessarily always control particle entrapments, nor do larger particles get selectively and consistently entrapped in steady vortices. Strikingly, a change in the shape of large particles from circular to elliptical resulted in stronger entrapments of smaller circular particles, but enhanced outflows of larger particles, which could be an alternative microfluidics-based method for sorting and separation of particles of different sizes and shapes.

Combined effects of fluid type and particle shape on particles flow in microfluidic platforms

“…Thus, elevated inertial effects on the trajectories of a mobile particle in a dilatant fluid caused by relatively sharper gradients of fluid velocities than in Newtonian or pseudoplatic fluids are comparable to the elevated inertial effects on the settling trajectories of a denser particle in an initially quiescent fluid or flow trajectories of a particle in higher Reflow. Overall transitions in flow trajectories of a single DSP in pseudoplastic fluid flow to flow trajectories in dilatant fluid flow are consistent with settling trajectories of a circular particle [47], or an elliptical particle [48], or a particle of other geometric shapes as the particle density is increased [14].…”

“…DSP-LBM simulations in [14] were practically insensitive to the grid resolution. The same lattice spacing and particles' dimensions in [14] were adopted in DSP-LBM simulations in this paper, in which R p =10 lattice units, N Bnd =100 for DCsPs, and the aspect ratio of the elliptical and rectangular particles is 2. N Bnd =100 led to a lattice spacing of ∼ 0.6 − 0.7 < 1 along the circumference of circular and elliptical particles, which eliminated the risk for missing any IPBN or EPBNs in calculating Eq.…”

“…− U p / t is the force induced by covered, r c b , and uncovered, r u b lattice nodes due to due to particle motion [43,44,45]. Steric interaction forces, F ri , between the particles and between the particles and stationary solid zones, including channel walls and inline obstacles, are expressed in terms of two-body Lennard-Jones potentials [14,42] such that F ri = −ψ |ri| |r it | −13 n, where | r i | is the distance between a particle surface node and the neighboring particle surface node (r i = r pp ) or between a particle surface node and the stationary solid node on channel walls or inline obstacles (r i = r pw ); p is the particle index; | r it | is the repulsive threshold distance; n is the unit vector along r i ; and ψ is the repulsive strength between the particles and between the particles and stationary solid nodes.…”

“…The initial tilt angle of non-circular particles is 0 • . ψ=1 and r it =2.5 lattice spacing in simulating particle-particle and particle-wall interactions [14].…”

Effects of Advective-Diffusive Transport of Multiple Chemoattractants on Motility of Engineered Chemosensory Particles in Fluidic Environments

“…The particle flow submodule of the CLB model [19,20], built on the LBM formulation by [34][35][36], was modified to simulate hydrodynamic interactions between an ECP (represented as a circular-cylindrical particle in the LBM) and the bulk fluid [21]. ECP-fluid hydrodynamic forces, F r b at boundary nodes located halfway between the intra-particle lattice node, r v , and extra-particle lattice node, r v + e i , are computed based on momentum exchanges between the ECP and surrounding fluid ( Figure 4) [34,37]…”