A short review on AC electro-thermal micropumps based on smeared structural polarizations in the presence of a temperature gradient

Stubbe, Marco; Gimsa, Jan

doi:10.1016/j.colsurfa.2010.09.013

Cited by 32 publications

(63 citation statements)

References 39 publications

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“…These phenomena can be exploited, e.g. for the construction of micropumps [17,18], though usually they disturb the intended manipulation. These effects have been investigated particularly in a series of publications by the groups of Morgan and Castellanos [16,[19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Fluid streaming above interdigitated electrodes in dielectrophoresis experiments

2011

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For the investigation of alternating current electrokinetic effects, a system is presented that allows for the simultaneous observation of fluid flow above and around microelectrodes in all three directions in space. Beside the usual microscopical view from top, lateral observation through the same objective is made possible by two small mirrors that are placed next to the electrodes. Fluid flow and movement of fluorescent nanoparticles above interdigitated electrodes are monitored by fluorescence microscopy and digital imaging and are further analysed by image processing. Field frequencies are varied from 10 Hz to 1 GHz at up to 10V(rms) . Electrical conductivity of the fluid is monitored in situ in the actual measuring chamber.

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Section: Introductionmentioning

confidence: 99%

Fluid streaming above interdigitated electrodes in dielectrophoresis experiments

2011

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“…Generally, the pump velocity of ETμPs is generated by the effective volumetric force acting on the whole volume of the medium in the range of the AC field. The pump velocity ν depends on the geometry of the pump and fluid channels, as well as the viscosity η of the pump medium :

ν = \frac{ϕ ζ}{η} 〈\bar{F}〉

with ϕ and

(〈〉, \bar{F})

being a specific geometry coefficient and the time‐averaged mean volume force acting on all volume elements in the pump volume in N/m 3 . The latter is given by :

〈\bar{F}〉 = - \frac{1}{2} ɛ_{normalM} \frac{Δ T_{normalE}}{ζ} E^{2} (\frac{0.024}{1 + {((), ω / ω_{MW})}^{2}} - 0.002)

with ε M , Δ T E , ω, and ω MW being the permittivity of the medium, the temperature difference between the field electrodes, the angular field frequency, and the Maxwell–Wagner angular frequency :

ω_{MW} = 2 π f_{MW} = σ_{normalM} ɛ_{M}^{- 1}

The combination of Eqs.…”

Section: Methodsmentioning

confidence: 99%

“…Large field‐electrode gaps of 390 μm and more were used. The pump velocity was controlled by the temperature gradient resulting from the balance of Joule's medium heating by the AC pump field and the heating element which introduced an asymmetric temperature distribution with respect to the field electrodes .…”

Section: Introductionmentioning

confidence: 99%

Experimental verification of an equivalent circuit for the characterization of electrothermal micropumps: High pumping velocities induced by the external inductance at driving voltages below 5 V

2013

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Electrothermal micropumps (ETμPs) use local heating to create conductivity and permittivity gradients in the pump medium. In the presence of such gradients, an external AC electric field influences smeared spatial charges in the bulk of the medium. When there is also a symmetry break, the field-charge interaction results in an effective volumetric force resulting in medium pumping. The advantages of the ETμP principle are the absence of moving parts, the opportunity to passivate all the pump structures, homogeneous pump-channel cross-sections, as well as force plateaus in broad frequency ranges. The ETμPs consisted of a DC-heating element and AC field electrodes arranged in a 1000 μm × 250 μm × 60 μm (length × width × height) channel. They were processed as platinum structures on glass carriers. An equivalent-circuit diagram allowed us to model the frequency-dependent pumping velocities of passivated and nonpassivated ETμPs, which were measured at medium conductivities up to 1.0 S/m in the 300 kHz to 52 MHz frequency range. The temperature distributions within the pumps were controlled by thermochromic beads. Under resonance conditions, an additional inductance induced a tenfold pump-velocity increase to more than 50 μm/s at driving voltages of 5 V(rms). A further miniaturization of the pumps is viewed as quite feasible.

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“…By contrast, the academical term 'smeared structural polarizations' was recently proposed by Gimsa et al to reveal the physical essence of ACET [31,49,50]. Particle DEP has a surface-coupled nature, in that electrical properties are piecewise constant on either side of the phase boundary.…”

Section: Introductionmentioning

confidence: 99%

A microscopic physical description of electrothermal‐induced flow for control of ion current transport in microfluidics interfacing nanofluidics

et al. 2019

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The phenomenon of electrothermal (ET) convection has recently captured great attention for transporting fluidic samples in microchannels embedding simple electrode structures. In the classical model of ET‐induced flow, a conductivity gradient of buffer medium is supposed to arise from temperature‐dependent electrophoretic mobility of ionic species under uniform salt concentrations, so it may not work well in the presence of evident concentration perturbation within the background electrolyte. To solve this problem, we develop herein a microscopic physical description of ET streaming by fully coupling a set of Poisson‐Nernst‐Planck‐Navier‐Stokes equations and temperature‐dependent fluid physicochemical properties. A comparative study on a standard electrokinetic micropump exploiting asymmetric electrode arrays indicates that, our microscopic model always predicts a lower ET pump flow rate than the classical macroscopic model even with trivial temperature elevation in the liquid. Considering a continuity of total current density in liquids of inhomogeneous polarizability, a moderate degree of fluctuation in ion concentrations on top of the electrode array is enough to exert a significant influence on the induction of free ionic charges, rendering the enhanced numerical treatment much closer to realistic experimental measurement. Then, by placing a pair of thin‐film resistive heaters on the bottom of an anodic channel interfacing a cation‐exchange medium, we further provide a vivid demonstration of the enhanced model's feasibility in accurately resolving the combined Coulomb force due to the coexistence of an extended space charge layer and smeared interfacial polarizations in an externally‐imposed temperature gradient, while this is impossible with conventional linear approximation. This leads to a reliable method to achieve a flexible regulation on spatial‐temporal evolution of ion‐depletion layer by electroconvective mixing. These results provide useful insights into ET‐based flexible control of micro/nanoscale solid entities in modern micro‐total‐analytical systems.

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A short review on AC electro-thermal micropumps based on smeared structural polarizations in the presence of a temperature gradient

Cited by 32 publications

References 39 publications

Fluid streaming above interdigitated electrodes in dielectrophoresis experiments

Fluid streaming above interdigitated electrodes in dielectrophoresis experiments

Experimental verification of an equivalent circuit for the characterization of electrothermal micropumps: High pumping velocities induced by the external inductance at driving voltages below 5 V

A microscopic physical description of electrothermal‐induced flow for control of ion current transport in microfluidics interfacing nanofluidics

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