Computational Fluid Dynamics (CFD) Simulation of Microfluidic Focusing in a Low-Cost Flow Cytometer

Inertial microfluidics refers to the manipulation of the location and velocity of particles suspended in microscale fluid flow without the introduction of outside forces. It has promising applications in flow cytometry and other biomedical technologies because of the potential for lowering cost and complexity relative to current particle focusing methods. Utilizing inertial microfluidics requires accurately modeling the effects of inertial forces acting on particles. This paper explores a method of predicting the trajectory of microscale particles using the Discrete Phase Model of the ANSYS Fluent CFD software. A model was developed for the effects of inertial lift on solid particles in Poiseuille flow. This method was observed to have good agreement with empirical results when modeling the behavior of neutrally buoyant spherical particles experiencing non-negligible laminar flow in straight circular channels. The particles were observed to focus to an equilibrium annulus of about 0.6 the diameter of the channel. The speed with which they focused was observed to vary proportionally with particle diameter and Reynolds number, corresponding with empirical results