Active control of particle position by boundary slip in inertial microfluidics

TL;DR

This paper introduces a boundary slip-based method to actively control the vertical position of particles in inertial microfluidic channels, enhancing particle focusing and separation precision.

Contribution

The study demonstrates how unilateral slip boundary conditions can be used to manipulate particle equilibrium positions in inertial microfluidics, a novel approach for real-time vertical control.

Findings

Boundary slip effectively shifts particle equilibrium positions.

Elliptical and rectangular particles exhibit non-uniform rotations.

The scheme improves particle focusing and separation accuracy.

Abstract

Inertial microfluidic is able to focus and separate particles in microchannels based on the characteristic geometry and intrinsic hydrodynamic effect. Yet, the vertical position of suspended particles in the microchannel cannot be manipulated in real time. In this study, we utilize the boundary slip effect to regulate the parabolic velocity distribution of fluid in the microchannel and present a scheme to active control the vertical position of particles in inertial microfluidics. The flow field of a microchannel with a unilateral slip boundary is equivalent to that of the microchannel widened by the relevant slip length, and the particle equilibrium positions in the two microchannels are consistent consequently. Then, we simulate the lateral migrations of three kinds of typical particles, namely circle, ellipse, and rectangle in the microchannel. Unlike the smooth trajectories of circular particles, the motions of the elliptical and rectangular particles are accompanied by regular fluctuations and non-uniform rotations due to their non-circular geometries. The results demonstrate that the unilateral slip boundary can effectively control the vertical equilibrium position of particles. Thus, the present scheme enables to active manipulate the particles positions in vertical direction and can promote more accurate focusing, separating, and transport in inertial microfluidics.