Focusing and Sorting of Particles in Spiral Microfluidic Channels

A El Hasni,K Göbbels,A.L Thiebes,P Bräunig,W Mokwa,U Schnakenberg

doi:10.1016/j.proeng.2011.12.295

Abstract

We present a microfluidic device for focusing and separation applications of large particles exploiting inertial migration in curved microchannels. Due to the curvilinear geometry of the microchannel particles experience a combination of inertial lift and Dean drag forces causing a lateral equilibration at a position near the inner wall. Depending on the ratio of lift and Dean drag forces particles with different sizes occupy distinct equilibrium positions resulting in individual particle streams. For testing the principle, a 5 loop spiral microchannel was used. Channel width and spacing between successive loops were fixed to 500μm and the height to 220μm. To evaluate the device for sorting large insect cells, particle focusing and separation was carried out using fluorescently labeled 40μm and 60μm polystyrene beads.

Highlights

Focusing and sorting of micro particles or biological cells in microfluidic systems for analysis applications is a process of great importance [1]
Due to inertial lift forces arising from the parabolic nature of the laminar velocity profile in a Poiseuille flow, suspended particles migrate across the streamlines to an equilibrium position away from the channel centre
Since the ratio of the lift force FL to the Dean drag force FD depends on particle size, particles with different diameter equilibrate at distinct positions resulting in a continuous separation of multi-sized particle mixture

Summary

Introduction

Focusing and sorting of micro particles or biological cells in microfluidic systems for analysis applications is a process of great importance [1]. Various techniques employing external forces, such as dielectrophoresis, acoustic waves, and optical interference have been used on the microscale [2]. These techniques show integral limitation including modification of particles or cellular properties and reduced sample volumes due to the low operating flow rates [2]. High throughput passive particle separation based on inertial migration in curved microchannels has been described [3]. This method avoids the disadvantages of conventional techniques needing externally applied forces since only fluidic forces and particle size influence the particle separation. We applied a spiral microchannel for focusing and separation of a mixture of large-sized particles with a diameter of 40 μm and 60 μm

Working principle

Microchannel design and fabrication

Particle focusing

Results

Conclusions