Manipulating particles in microfluidics by floating electrodes (original) (raw)
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On-demand particle enrichment in a microfluidic channel by a locally controlled floating electrode
Sensors and Actuators B: Chemical, 2011
A flexible strategy for the on-demand control of the particle enrichment and positioning in a microfluidic channel is proposed and demonstrated by the use of a locally controlled floating metal electrode attached to the channel bottom wall. The channel is subjected to an axially acting global DC electric field, but the degree of charge polarization of the floating electrode is governed largely by a local control of the voltage applied to two micron-sized control electrodes (CEs) on either side of the floating electrode (FE). This strategy allows an independent tuning of the electrokinetic phenomena engendered by the floating electrode regardless of the global electric field across the channel, thus making the method for particle manipulation far more versatile and flexible. In contrast to a dielectric microchannel wall possessing a nearly uniform surface charge (or zeta potential), the patterned metal strip (floating electrode) is polarized under electric field resulting in a non-uniform distribution of the induced surface charge with a zero net surface charge, and accordingly induced-charge electro-osmotic (ICEO) flow. The ICEO flow can be regulated by the control electric field through tuning the magnitude and polarity of the voltage applied to the CEs, which in turn affects both the hydrodynamic field as well as the particle motion. By controlling the control electric field, on-demand control of the particle enrichment and its position inside a microfluidic channel has been experimentally demonstrated. Buffalo in 1987. His research interests cover aspects of mechanics and instabilities of soft visco-elastic interfaces; thin films and nano-confined systems; self-organized mesopatterning of polymers, ceramics, hydrogels and carbon; interfacial and colloidal interactions; wetting and adhesion; smart and functional materials: adhesives, catalytic, optical, super-hydrophobic and nano-composites; biosurfaces: surface chemistry of cornea and tear film; cell adhesion; and interfaces in membranes and microfluidics.
Electrohydrodynamic modeling for manipulation of micro/nano particles in microfluidic systems
2012
Studies developed over the past ten years, since the inception of microfluidics, showed that the electric force can be the ideal candidate for spatial precision control of the particles suspensions movement in an operating fluid (electrohydrodynamics). A very high electric field can be obtained and the electric force can be highly localized because the electrodes are placed cross a small distance (from sub-millimeter to a few microns). Dielectrophoretic (DEP) force is exerted when a neutral particle is polarized in a non-uniform electric field, and depends on the dielectric properties of the particle and those of the suspending medium. The integration of DEP and microfluidic systems permits numerous applications in different areas as micro/nano particles manipulation and filtration, nanoassembly, biosensors, cell therapeutics, drug discovery, medical diagnostics. This paper presents the basics of the dielectrophoresis theory, different examples of electrodes configuration for particle manipulation together with a set of numerical results obtained in the frame of a two-dimensional mathematical model. The numerical solutions are computed using the finite element method.
ELECTROPHORESIS, 2021
Electrokinetically driven insulator-based microfluidic devices represent an attractive option to manipulate particle suspensions. These devices can filtrate, concentrate, separate, or characterize micro and nanoparticles of interest. Two decades ago, inspired by electrodebased dielectrophoresis, the concept of insulator-based dielectrophoresis (iDEP) was born. In these microfluidic devices, insulating structures (i.e., posts, membranes, obstacles, or constrictions) built within the channel are used to deform the spatial distribution of an externally generated electric field. As a result, particles suspended in solution experience dielectrophoresis (DEP). Since then, it has been assumed that DEP is responsible for particle trapping in these devices, regardless of the type of voltage being applied to generate the electric field-direct current (DC) or alternating current. Recent findings challenge this assumption by demonstrating particle trapping and even particle flow reversal in devices that prevent DEP from occurring (i.e., unobstructed long straight channels stimulated with a DC voltage and featuring a uniform electric field). The theory introduced to explain those unexpected observations was then applied to conventional "DC-iDEP" devices, demonstrating better prediction accuracy than that achieved with the conventional DEP-centered theory. This contribution summarizes contributions made during the last two decades, comparing both theories to explain particle trapping and highlighting challenges to address in the near future.
Microelectronic Engineering, 2008
One of the challenges in biological applications of nanotechnology is the manipulation of micro and nanoparticles in microfluidic systems. In one approach, the short-range forces exerted on particles by electric fields, e.g. via dielectrophoresis, can be utilized for this purpose. By a combination of dielectrophoresis and electroosmosis it is possible to act on particles in larger volumes. In this work a new method for examining particle distributions in microfluidic devices is presented together with results of experiments in which the method was used to investigate the combination of dielectrophoresis and electroosmosis.
Electrohydrodynamic Flow for Microfluidic Mixing and Microparticle Manipulation
Abstract—We discuss the mechanisms by which bulk electro-hydrodynamic air thrust or ionic wind generated above and directed towards the surface of a microfluidic chamber by a sharp electrode tip can give rise to surface or bulk liquid recirculation in the chamber and demonstrate various ways in which the phenomenon can be exploited for microfluidic mixing and particle trapping.
Electrophoresis, 2009
Transient electrophoretic motion of a charged particle through a converging-diverging microchannel is studied by solving the coupled system of the Navier-Stokes equations for fluid flow and the Laplace equation for electrical field with an arbitrary Lagrangian-Eulerian finite-element method. A spatially non-uniform electric field is induced in the converging-diverging section, which gives rise to a direct current dielectrophoretic (DEP) force in addition to the electrostatic force acting on the charged particle. As a sequence, the symmetry of the particle velocity and trajectory with respect to the throat is broken. We demonstrate that the predicted particle trajectory shifts due to DEP show quantitative agreements with the existing experimental data. Although convergingdiverging microchannels can be used for super fast electrophoresis due to the enhancement of the local electric field, it is shown that large particles may be blocked due to the induced DEP force, which thus must be taken into account in the study of electrophoresis in microfluidic devices where non-uniform electric fields are present.