Hydrodynamic Trapping of Particles in an Expansion-Contraction Microfluidic Device

Ruijin Wang

doi:10.1155/2013/496243

Abstract

Manipulation and sorting of particles utilizing microfluidic phenomena have been a hot spot in recent years. Here, we present numerical investigations on particle trapping techniques by using intrinsic hydrodynamic effects in an expansion-contraction microfluidic device. One emphasis is on the underlying fluid dynamical mechanisms causing cross-streamlines migration of the particles in shear and vortical flows. The results show us that the expansion-contraction geometric structure is beneficial to particle trapping according to its size. Particle Reynolds number and aspect ratio of the channel will influence the trapping efficiency greatly because the force balance between inertial lift and vortex drag forces is the intrinsic reason. Especially, obvious inline particles contribution presented when the particle Reynolds number being unit. In addition, we selected three particle sizes (2, 7, and 15 μm) to examine the trapping efficiency.

Highlights

Microfluidics has greatly interested many researchers in recent years, and has been widely used in the areas of nanomaterials preparation, pharmaceutical analysis, protein engineering, and so on [1,2,3,4]
When particles are suspended in the carried fluid, the particle behavior is affected by the inertial and viscous forces occurring in the interaction with fluid
According to a number of theoretical analyses, the inertial migration phenomenon can be explained by a sheargradient-induced lift force that causes particles to migrate away from the axis of pipe and a wall-effect-induced lift force that repels particles away from a pipe wall [22, 23]

Summary

Introduction

Microfluidics has greatly interested many researchers in recent years, and has been widely used in the areas of nanomaterials preparation, pharmaceutical analysis, protein engineering, and so on [1,2,3,4]. Hydrodynamic manipulation of particles in an expansioncontraction microfluidic device is a passive method by harnessing microchannel geometrical effects and nonlinear hydrodynamic forces and needs not any application of external force leading to a complicated device structure. Karimi et al [11] concentrated their study on the dynamical mechanisms of cross stream migration particles in shear and vortical flows. According to their research work, in the contraction part, particles flow under the balance of shear-gradient lift force and wall effect lift force. When the particles move into the expansion part, wall effect lift force disappears and the shear-gradient lift force leads particles to the vortex formed in the orifice. The research object is to gain an insight into what condition being beneficial to the particle trapping efficiency for varying particle sizes and to supply the design foundations of such a microfluidic device

Problem Description

Results and Discussion

Conclusions