Trapping of micrometre and sub-micrometre particles by high-frequency electric fields and hydrodynamic forces

Müller, Torsten; Gerardino, A.; Schnelle, Thomas; Shirley, Stephen G.; Bordoni, F.; Gasperis, Giovanni De; Leoni, R.; Fuhr, G.

doi:10.1088/0022-3727/29/2/010

Cited by 157 publications

(137 citation statements)

References 17 publications

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“…Similar to those previously studied in eDEP [34][35][36][37][38][39][40][41][42][43][44][45][46][47], electrothermal flows in iDEP devices also arise from the action of the electric field (both DC and AC) on fluid inhomogeneities (predominantly electrical properties including conductivity and permittivity) formed in the constriction region due to Joule heating-induced temperature gradients. Figure 4 shows the numerically predicted temperature and electric field contours in the constriction region at 100 V DC/500 V AC.…”

Section: Resultssupporting

confidence: 63%

“…It has been long known in capillary electrophoresis that Joule heating can elevate the buffer temperature and disturb the electroosmotic flow causing significant sample dispersion [30][31][32][33]. The effects of Joule heating on fluid temperature and motion in eDEP have been investigated previously [34][35][36][37][38]. It was reported that a pair of counter-rotating fluid circulations could form near the microelectrodes [39].…”

Section: Introductionmentioning

confidence: 99%

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Joule heating effects on electroosmotic flow in insulator‐based dielectrophoresis

et al. 2011

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Joule heating effects on electroosmotic flow in insulator-based dielectrophoresisInsulator-based dielectrophoresis (iDEP) is an emerging technology that has been successfully used to manipulate a variety of particles in microfluidic devices. However, due to the locally amplified electric field around the in-channel insulator, Joule heating often becomes an unavoidable issue that may disturb the electroosmotic flow and affect the particle motion. This work presents the first experimental study of Joule heating effects on electroosmotic flow in a typical iDEP device, e.g. a constriction microchannel, under DC-biased AC voltages. A numerical model is also developed to simulate the observed flow pattern by solving the coupled electric, energy, and fluid equations in a simplified two-dimensional geometry. It is observed that depending on the magnitude of the DC voltage, a pair of counter-rotating fluid circulations can occur at either the downstream end alone or each end of the channel constriction. Moreover, the pair at the downstream end appears larger in size than that at the upstream end due to DC electroosmotic flow. These fluid circulations, which are reasonably simulated by the numerical model, form as a result of the action of the electric field on Joule heatinginduced fluid inhomogeneities in the constriction region.

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Section: Resultssupporting

confidence: 63%

Section: Introductionmentioning

confidence: 99%

Joule heating effects on electroosmotic flow in insulator‐based dielectrophoresis

et al. 2011

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“…The mean free path of the movement is inversely dependent on mass, implying that decreases in the particle diameter require significant increases in the applied electrostatic energy (or field strength). The stable trapping of viruses and beads has been demonstrated previously [6][7][8][9]. Here we show that nanometre sized latex spheres can be both stably trapped in nanofabricated electrode arrays and, more importantly, that a heterogeneous mixture can be separated into two populations using dielectrophoresis.…”

supporting

confidence: 70%

Dielectrophoretic separation of nano-particles

Green

Morgan

1997

J. Phys. D: Appl. Phys.

156

141

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Abstract. We show for the first time that it is possible to separate a population of nanoparticles into two subpopulations solely on the basis of their dielectric properties. Using nanofabricated electrode arrays it has been shown that a solution of 93 nm diameter latex beads with a distribution of surface charge can be separated by the application of non-uniform AC electric fields (dielectrophoresis). The mixture separated into two populations, one experiencing positive dielectrophoresis and the other negative dielectrophoresis.The movement of polarizable particles in non-uniform fields, termed dielectrophoresis by Pohl [1], has been exploited as a rapid non-invasive tool for the diagnosis and separation of mammalian cells and micro-organisms [2]. It has found practical applications in medicine for separating cancer cells from blood [3], enriching CD34+ cells in bone marrow samples [4] and for detecting the viability of pathogenic organisms in water [5].Separation of particles is based on the fact that when placed in a non-uniform AC electric field, polarized particles experience a variable translational force, depending on the applied field frequency. For particles whose polarizability is greater than the medium the net movement is to regions of highest field strength, whereas particles whose polarizability is less than the medium move to the region of lowest field gradient. Because the particle's polarization is frequency dependent, the net force is also frequency dependent. Therefore, by judicious choice of suspending medium conductivity and applied frequency, even particles with very similar dielectric properties can be efficiently separated.The sum total of the forces on a given particle is: F total = F deterministic + F random . The deterministic force is the sum of the sedimentation, hydrodynamic and dielectrophoretic forces. The random force is due to Brownian motion and for particles with a diameter of the order of 100 nm this force is considerable. The mean free path of the movement is inversely dependent on mass, implying that decreases in the particle diameter require significant increases in the applied electrostatic energy (or field strength). The stable trapping of viruses and beads has been demonstrated previously [6][7][8][9]. Here we show that nanometre sized latex spheres can be both stably trapped in nanofabricated electrode arrays and, more importantly, that a heterogeneous mixture can be separated into two populations using dielectrophoresis. Experiments were conducted on charged latex spheres of 93 nm diameter, using planar electrodes manufactured by electron-beam lithography. The applied electric field strength was 2.5 × 10 5 V m −1 and the suspending medium conductivity was 0.018 S m −1 . Large electric field strengths cause localized heating of electrode structures which in turn gives rise to discontinuities in conductivity, permittivity and viscosity of the medium. The result is the inception

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“…Dielectrophoretic forces have been used to separate and manipulate cells, 2,11 bacteria, 12,13 viruses, 14 and submicron latex spheres. 5,15,16 Recently the dielectrophoretic manipulation of DNA molecules has led to applications such as the concentration of DNA molecules, [17][18][19] DNA-protein interaction studies, 20,21 and molecular surgery of DNA. 22 However, a detailed understanding of the behavior of surface-immobilized DNA molecules when exposed to high frequency ac electric fields, and in particular the orientation and elongation of DNA as a result of dielectrophoretic force and torque, has not yet been established.…”

Section: Introductionmentioning

confidence: 99%

Influence of alternating current electrokinetic forces and torque on the elongation of immobilized DNA

Germishuizen

Tosch

Middelberg

et al. 2004

Journal of Applied Physics

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Articles you may be interested inThe authors investigate the elongation and orientation of different-sized deoxyribose nucleic acid (DNA) molecules, tethered onto gold electrodes via a terminal thiol, under the influence of high frequency ac electric fields. The DNA molecules are elongated from a random coil into an extended conformation and orientated along the electric field lines as a result of the forces acting on the molecules during the application of the ac electric fields. Elongation was observed in the frequency range 100 kHz-1 MHz, with field strengths of 0.06-1.0 MV/ m. Maximum elongation for all DNA fragments tested, irrespective of size, was found for frequencies between 200 and 300 kHz. The torque acting on the induced dipole in the DNA molecules, complemented by a directional bias force, opposite in direction to the dielectrophoretic force, provides the main contribution to the elongation process. The length of elongation is limited to either half the distance between opposing electrodes or to the contour length of the DNA, whichever is shorter. Further, the authors show that the normalized length of the elongated DNA molecules is independent of the contour length of the DNA.

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Trapping of micrometre and sub-micrometre particles by high-frequency electric fields and hydrodynamic forces

Cited by 157 publications

References 17 publications

Joule heating effects on electroosmotic flow in insulator‐based dielectrophoresis

Joule heating effects on electroosmotic flow in insulator‐based dielectrophoresis

Dielectrophoretic separation of nano-particles

Influence of alternating current electrokinetic forces and torque on the elongation of immobilized DNA

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