Study of Local Inertial Focusing Conditions for Spherical Particles in Asymmetric Serpentines

Eric Pedrol,Francesc Díaz,Jaume Massons,Magdalena Aguiló

doi:10.3390/fluids5010001

Abstract

Inertial focusing conditions of fluorescent polystyrene spherical particles are studied at the pointwise level along their pathlines. This is accomplished by an algorithm that calculates a degree of spreading function of the particles’ trajectories taking streaklines images as raw data. Different confinement ratios of the particles and flow rates are studied and the results are presented in state diagrams showing the focusing degree of the particles in terms of their position within a curve of an asymmetric serpentine and the applied flow rate. In addition, together with numerical simulation results, we present empirical evidence that the preferred trajectories of inertially focused spheres are contained within Dean vortices’ centerlines. We speculate about the existence of a new force, never postulated before, to explain this fact.

Highlights

The merging of microfluidics with inertial focusing has provided researchers with interesting applications whose performance can hardly be matched by conventional techniques in other disciplines, in fields related with flow cytometry
In this paper we present a series of focusing measurements which involve the characterization of the degree of spreading (DoS) of the streak of fluorescent polystyrene beads moving in an asymmetric serpentine under inertial focusing conditions
Focusing.InInmost mostofofthe thecases, cases,two twolocal local minima found degree of spreadlesser minima areare found forfor thethe degree of spreading ing along the focused streak of particles at a given flow rate

Summary

Introduction

The merging of microfluidics with inertial focusing has provided researchers with interesting applications whose performance can hardly be matched by conventional techniques in other disciplines, in fields related with flow cytometry. Inertial focusing positions are inherently dependent on particle’s physical properties (its size, shape and deformability [10,11,12,13]) Both theoretical and experimental approaches have found a strong relationship between the particle’s diameter and the inertial lift [14,15,16,17,18,19,20]. A precise knowledge of the scaling laws of the involved inertial forces has been sought [1,14,35,36]

Methods

Results

Conclusion