Microfluidics and Nanofluidics

, Volume 4, Issue 5, pp 375–389

A rapid magnetic particle driven micromixer

  • Yiou Wang
  • Jiang Zhe
  • Benjamin T. F. Chung
  • Prashanta Dutta
Research Paper

DOI: 10.1007/s10404-007-0188-x

Cite this article as:
Wang, Y., Zhe, J., Chung, B.T.F. et al. Microfluid Nanofluid (2008) 4: 375. doi:10.1007/s10404-007-0188-x

Abstract

Performances of a magnetic particle driven micromixer are predicted numerically. This micromixer takes advantages of mixing enhancements induced by alternating actuation of magnetic particles suspended in the fluid. Effects of magnetic actuation force, switching frequency and channel’s lateral dimension have been investigated. Numerical results show that the magnetic particle actuation at an appropriate frequency causes effective mixing and the optimum switching frequency depends on the channel’s lateral dimension and the applied magnetic force. The maximum efficiency is obtained at a relatively high operating frequency for large magnetic actuation forces and narrow microchannels. If the magnetic particles are actuated with a much higher or lower frequency than the optimum switching frequency, they tend to add limited agitation to the fluid flow and do not enhance the mixing significantly. The optimum switching frequency obtained from the present numerical prediction is in good agreement with the theoretical analysis. The proposed mixing scheme not only provides an excellent mixing, even in simple microchannel, but also can be easily applied to lab-on-a-chip applications with a pair of external electromagnets.

Keywords

Magnetic particles Micromixing Microfluidic Magnetic actuation 

List of symbols

A

cross-section area of the microchannel (m2)

Ap

cross-section area of the particle (m2)

B

magnetic flux density (Tesla)

C

dimensionless concentration

CD

drag coefficient

D

diffusion coefficient (m2/s)

F

force (N)

f

switching frequency (Hz)

fcr

critical switching frequency (Hz)

H

channel height (m)

He

magnetic field strength (A/m)

HM

electromagnet thickness (m)

I

current (A)

L

streamwise dimension or length (m)

m

particle mass (kg)

M

magnetization of the particle (A/m)

P

pressure (N/m2)

Pe

peclet number (ReSc)

r

particle radius (m)

Re

Reynolds number (UWρf/η)

Sc

Schmidt number (η/ρfD)

St

Strouhal number (Wf/U)

S

distance between two parallel electromagnets (m)

t

time (s)

T

period, 1/f (s)

U

relative velocity between the fluid and particle along y direction (m/s)

V

volume (m3)

\(\vec{V}\)

fluid’s velocity vector

\(\vec{v}\)

particles’ velocity vector

W

lateral dimension or width (m)

x

streamwise coordinate of the microchannel

y

lateral coordinate of the microchannel

z

coordinate in the direction normal to the xy plane

Greek

η

dynamic viscosity of the fluid (kg/m s)

ρ

density (kg/m3)

χ

magnetic susceptibility of the particle

ηe

mixing efficiency (%)

μ

permeability (N/A2)

Subscript

d

drag

f

fluid

m

magnetic

M

electromagnet

o

prior mixing stage or medium

p

particle

r

relative

s

magnetization saturation

complete mixing state

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Yiou Wang
    • 1
  • Jiang Zhe
    • 1
  • Benjamin T. F. Chung
    • 1
  • Prashanta Dutta
    • 2
  1. 1.Department of Mechanical EngineeringThe University of AkronAkronUSA
  2. 2.School of Mechanical and Materials EngineeringWashington State UniversityPullmanUSA