Introducing phase analysis light scattering for dielectric characterization: measurement of traveling-wave pumping

Gimsa, Jan; Eppmann, Peter; Prüger, Bernhard

doi:10.1016/s0006-3495(97)78355-3

Cited by 37 publications

(37 citation statements)

References 19 publications

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“…Note that the effect decreases with increasing conductivity. Electrothermal travelling wave pumping experiments [4,22] show that voltages greater than 10 V are required to achieve noticeable fluid velocities, in agreement with the calculated voltages shown in the figures. The velocity measurements given in [22] show that strong thermal convection is obtained for conductivities greater than 1.6 × 10 −2 S m −1 .…”

Section: Fluid Flowsupporting

confidence: 79%

“…Electrothermal travelling wave pumping experiments [4,22] show that voltages greater than 10 V are required to achieve noticeable fluid velocities, in agreement with the calculated voltages shown in the figures. The velocity measurements given in [22] show that strong thermal convection is obtained for conductivities greater than 1.6 × 10 −2 S m −1 . In the same work, it was shown that the velocity increases with conductivity (in the measured range of 4 × 10 −3 to 1.6 × 10 −2 S m −1 ), which is a clear indication of Joule heating.…”

Section: Fluid Flowsupporting

confidence: 79%

See 1 more Smart Citation

Electrohydrodynamics and dielectrophoresis in microsystems: scaling laws

Castellanos

Ramos

González-Weller

et al. 2003

J. Phys. D: Appl. Phys.

621

682

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The movement and behaviour of particles suspended in aqueous solutions subjected to non-uniform ac electric fields is examined. The ac electric fields induce movement of polarizable particles, a phenomenon known as dielectrophoresis. The high strength electric fields that are often used in separation systems can give rise to fluid motion, which in turn results in a viscous drag on the particle. The electric field generates heat, leading to volume forces in the liquid. Gradients in conductivity and permittivity give rise to electrothermal forces and gradients in mass density to buoyancy. In addition, non-uniform ac electric fields produce forces on the induced charges in the diffuse double layer on the electrodes. This causes a steady fluid motion termed ac electro-osmosis. The effects of Brownian motion are also discussed in this context. The orders of magnitude of the various forces experienced by a particle in a model microelectrode system are estimated. The results are discussed in relation to experiments and the relative influence of each type of force is described.

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Section: Fluid Flowsupporting

confidence: 79%

Section: Fluid Flowsupporting

confidence: 79%

Electrohydrodynamics and dielectrophoresis in microsystems: scaling laws

Castellanos

Ramos

González-Weller

et al. 2003

J. Phys. D: Appl. Phys.

621

682

View full text Add to dashboard Cite

show abstract

“…Gimsa et al [9] measures peak fluid velocity of approximately 10 µm s −1 and 25 µm s −1 for a conductivity of 8 mS m −1 and 16 mS m −1 , respectively, both with a driving voltage of 25 V pk-pk. The gap between successive electrodes was 70 µm.…”

Section: Changing the Temperaturementioning

confidence: 99%

“…Calculating the electric field induced force on the particle and its ensuing motion is relatively simple [3]. However, for DEP electrode arrays in general, the electric field not only produces an induced particle motion but is also responsible for an induced fluid flow in the suspending medium [7][8][9][10]. There are several physical mechanisms whereby the electric field can interact with the fluid, ranging from bulk effects such as convection and electrothermal effects to surface effects such as ac electro-osmosis [10].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of travelling wave induced electrothermal fluid flow

Perch-Nielsen¹,

Green²,

Wolff³

2004

J. Phys. D: Appl. Phys.

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Many microdevices for manipulating particles and cells use electric fields to produce a motive force on the particles. The movement of particles in non-uniform electric fields is called dielectrophoresis, and the usual method of applying this effect is to pass the particle suspension over a microelectrode structure. If the suspension has a noticeable conductivity, one important side effect is that the electric field drives a substantial conduction current through the fluid, causing localized Joule-heating. The resulting thermal gradient produces local conductivity and permittivity changes in the fluid. Dielectrophoretic forces acting upon these pockets of fluid will then produce motion of both the fluid and the particles. This paper presents a numerical solution of the electrical force and the resulting electrothermal driven fluid flow on a travelling wave structure. This common electrode geometry consists of interdigitated electrodes laid down in a long array, with the phase of the applied potential shifted by 90o n each subsequent electrode. The resulting travelling electric field was simulated and the thermal field and electrical body force on the fluid calculated, for devices constructed from two typical materials: silicon and glass. The electrothermal fluid flow in the electrolyte over the electrode array was then numerically simulated.The model predicts that the thermal field depends on the conductivity and applied voltage, but more importantly on the geometry of the system and the material used in the construction of the device. The velocity of the fluid flow depends critically on the same parameters, with slight differences in the thermal field for glass and silicon leading to diametrically opposite flow direction with respect to the travelling field for the two materials. In addition, the imposition of slight external temperature gradients is shown to have a large effect on the fluid flow in the device, under certain conditions leading to a reversal of the fluid flow direction.

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“…Electrothermal fluid flow is due to the action of an electric field on thermally induced gradients of conductivity and permittivity in the fluid (Melcher & Firebaugh 1967;Melcher 1981). The gradients of temperature can be produced by external sources, such as strong illumination (Green et al 2000), or caused by the applied electric field through Joule heating (Müller et al 1993;Gimsa, Eppmann & Prüger 1997;Wang, Sigurdson & Meinhart 2005). Observations and estimates show that electrothermal effects are important in microsystems for frequencies of the order of 1 MHz and voltages of the order of 10 V (Green et al 2001;Castellanos et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Electrothermal flows generated by alternating and rotating electric fields in microsystems

et al. 2006

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Electrothermal motion in an aqueous solution arises from the action of an electric field on inhomogeneities in the liquid induced by temperature gradients. The temperature field can be produced by the applied electric field through Joule heating, or caused by external sources, such as strong illumination. Electrothermal flows in microsystems are usually observed at applied signal frequencies around 1 MHz and voltages around 10 V. In this work, we present self-similar solutions for the motion of an aqueous solution in a constant temperature gradient placed on top of: (a) two coplanar electrodes subjected to an a.c. potential difference, and (b) four coplanar electrodes subjected to a four-phase a.c. signal, generating a rotating field. The first case produces two-dimensional rolls whereas the second case produces a liquid whirl. Finally, we present experimental results of electrothermal liquid flows generated by alternating and rotating electric fields under strong illumination, and these experiments are compared to the analytical solutions. The induced rotating flow could be used in the mixing of analytes and of liquids in microsystems.

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Introducing phase analysis light scattering for dielectric characterization: measurement of traveling-wave pumping

Cited by 37 publications

References 19 publications

Electrohydrodynamics and dielectrophoresis in microsystems: scaling laws

Electrohydrodynamics and dielectrophoresis in microsystems: scaling laws

Numerical simulation of travelling wave induced electrothermal fluid flow

Electrothermal flows generated by alternating and rotating electric fields in microsystems

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