Multibody interactions of actuated magnetic particles used as fluid drivers in microchannels
R. J. S. Derks
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A. J. H. Frijns
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M. W. J. Prins
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A. Dietzel
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M. W. J. Prins Philips Research Europe
, High Tech Campus 12, 5656 AE Eindhoven,
The Netherlands
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M. W. J. Prins Applied Physics, Eindhoven University of Technology
, P.O. Box 513, 5600 MB Eindhoven,
The Netherlands
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R. J. S. Derks (&) A. J. H. Frijns A. Dietzel Mechanical Engineering, Eindhoven University of Technology
, P.O. Box 513, 5600 MB Eindhoven,
The Netherlands
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A. Dietzel Holst Centre
, High Tech Campus 31, 5605 KN Eindhoven,
The Netherlands
The forced motion of superparamagnetic particles and their multibody interactions are studied in view of the application as integrated fluid drivers in microchannel systems. Previous studies on particle manipulation in open fluid volumes serve as our starting point for the analysis of particle dynamics and interplay effects in confined fluid volumes. An experimental setup is designed that offers a constant force field on all individual particles dispersed in a microchannel. Distinguishable multi-particle configurations are observed and analyzed on the basis of magnetic and hydrodynamic particle interaction mechanisms. The fluid driving performance and the efficiency of the particles are evaluated on system level by means of numerical simulation models.
1 Introduction
The current trend in lab-on-a-chip devices involves the
miniaturization and integration of a wide range of functions
(Haeberle and Zengerle 2007). For biosensors, a main
challenge lies in achieving a high functional performance
with respect to sensitivity, specificity, and speed (Bruls
et al. 2009). Devices for biochemical analysis therefore
often contain elements with a large surface area to enhance
binding capacity and allow parallel screening. For instance,
porous DNA hybridization microarrays have become an
effective form of screening technology and allow the
analysis of hundreds to thousands of genes simultaneously
(Chen et al. 2007; Grasso et al. 2006). A concern in these
high-surface area systems is the limited accessibility of the
reactive surfaces for the fluid and analyte, which slows
down the effective reaction rate (Vanderhoeven et al. 2005;
Yuen et al. 2003). As an example, we consider a porous
structure with microchannels of length L of several
hundreds of micrometers. Assuming molecular diffusion only,
the time s required to travel the distance L can be estimated
using Einsteins law of diffusion (Vanderhoeven et al.
2005): s L2=2 D. A DNA molecule or protein with a
typical diffusion coefficient D of 10-11 m2/s needs hours to
travel from the channel inlet to the outlet. Furthermore,
only a fraction of the molecules is able to enter the pore
that holds the specific capture molecules on its surface.
Active transportation of fluid and analyte within and
through micropores is therefore essential to enable
accelerated reaction rates. Several actuation methods have
already been discussed in literature, but each having one or
more crucial shortcomings. External mechanical pumps
typically require large sample volumes (Vanderhoeven
et al. 2005; Yuen et al. 2003; Laser and Santiago 2004).
Open systems such as droplet-based actuation are sensitive
to evaporation (Gutmann et al. 2005). Systems based on
capillary or electro kinetic flows have a strong dependence
on the chemical properties of the sample (Vanderhoeven
et al. 2005; Laser and Santiago 2004). In fact, a fluid
actuation system for high-surface-area elements should be
fully integrated and suited for small samples of complex
biological fluids (Chen et al. 2007).
Superparamagnetic particles can be used for different
functions in lab-on-a-chip applications (Gijs 2004; Pamme
2006; Bruls et al. 2009). Their electromagnetic motion
control is very flexible and can even be combined with the
self-assembly and alignment of particle chains (Derks et al.
2007; Petousis et al. 2007). As biological materials are
essentially non-magnetic, functions such as sample
filtering, analyte transport, mixing, labeling, or detection can be
applied in complex samples without undesired side effects
and high reproducibility. In this paper, we propose a novel
way for integrated fluid transport in porous high surface
area systems based on the hydrodynamic momentum
transfer by magnetic particles. By means of applied
magnetic fields, the particles are actuated in the microchannels
in a non-contact approach. The fluid is driven by the forced
motion of the particles to create a net flow through the
pores, as illustrated in Fig. 1. Such integrated driving
mechanism can be applied in a porous system for large as
well as small sample volumes, without generating dead
fluid volumes. Several papers have addressed the use of
magnetic particles for fluidic pumping on the microscale
(Hatch et al. 2001; Hartshorne et al. 2004). These discuss
irreversibly aggregated plugs of enormous numbers of
Fig. 1 A sketch of the fluid driving concept in microchannels by
confined actuated superp (...truncated)