Antonio González

Universidad de Sevilla, Sevilla, Andalusia, Spain

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Publications (7)9.19 Total impact

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    ABSTRACT: Microelectrodes subjected to AC potentials are usually employed to induce electrolyte flow, commonly known as AC electroosmotic (ACEO) flows. In this work, we apply novel theoretical results for analysing the influence of Faradaic reactions on these flows. Specifically, we choose to analyse the electrokinetic flow induced by a pair of coplanar symmetric microelectrodes, as the simplest microelectrode structure used in experiments. The liquid is assumed to be a 1:1 electrolyte with ions of different diffusivities. For simplicity, in the model only the cations are responsible for the Faradaic reactions while the anions do not react at the electrodes. We show how to use the novel model to numerically obtain the electrokinetic flow induced by the pair of electrodes. A remarkable new prediction of the model is that, for certain values of the parameters, fluid flow can occur in opposite direction to that obtained in the absence of Faradaic reactions.
    Colloids and Surfaces A Physicochemical and Engineering Aspects 01/2011; 376:47-52. · 2.11 Impact Factor
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    ABSTRACT: Net fluid flow of electrolytic solutions induced by a traveling-wave potential applied to an array of co-planar interdigitated microelectrodes has been reported. At low applied voltages the flow is driven in the direction of the traveling-wave potential, as expected by linear and weakly nonlinear theoretical studies. The flow is driven at the surfaces of the electrodes by electrical forces acting in the diffuse electrical double layer. The pumping mechanism has been analyzed theoretically under the assumption of perfectly polarizable electrodes. Here we extend these studies to include the effect of Faradaic currents on the electroosmotic slip velocity generated at the electrode/electrolyte interface. We integrate the electrokinetic equations under the thin-double-layer and low-potential approximations. Finally, we analyze the pumping of electrolyte induced by a traveling-wave signal applied to a microelectrode array using this linear model.
    Journal of Colloid and Interface Science 06/2007; 309(2):323-31. · 3.55 Impact Factor
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    ABSTRACT: Electrothermal motion in an aqueous solution appears when an electric field is coupled with thermally-induced gradients of conductivity and permittivity in the fluid. The temperature field can be produced by external sources, such as strong illumination, or caused by the applied electric field through Joule heating. Electrothermal flow in microsystems is usually important at frequencies around 1 MHz and voltages around. 10 V. In this work, we consider first the two-dimensional problem of an aqueous solution placed on top of two co-planar electrodes that are subjected to an ac potenfial difference when there is either a vertical or horizontal temperature gradient. Secondly, we study the three-dimensional problem of an aqueous solution lying on four co-planar electrodes which produce a rotating field. This electric field when combined with a vertical temperature gradient rotates the liquid. The resulting electric field an liquid motion in these problems are characterised using self-similar solutions. Finally, these analytical solutions are compared with numerical and experimental results.
    ASME 2003 International Mechanical Engineering Congress and Exposition; 01/2003
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    ABSTRACT: Planar microelectrodes, used for the electrokinetic manipulation of particles, generate high strength AC electric fields, resulting not only in forces on the particles but also on the suspending fluid. Observations of electrolytes on microelectrode structures at applied signal frequencies of the order of 1 MHz have shown the importance of the illumination in generating fluid flow. In this paper, these experiments are analysed in terms of the theory of electrothermally induced fluid flow. Numerical calculations are made of the electric field, temperature field and fluid flow, arising both from Joule heating and from light heating. The results verify that Joule heating is not important under the experimental conditions. The temperature gradient generated by the light that is required in order to match the experimental fluid velocities is determined.
    Journal of Electrostatics 08/2001; · 1.00 Impact Factor
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    ABSTRACT: The electrokinetic manipulation of particles suspended in a fluid medium is accomplished using microelectrodes that generate non-uniform fields of significant strength from low applied potentials. The high strength fields produce not only forces on the particles but also on the fluid medium used for suspension. This paper presents qualitative and semi-quantitative observations of the movement of the fluid at applied field frequencies of the order of 1MHz and higher. The importance of the illumination in generating the fluid flow is described, the flow depending on both the intensity of illumination and the applied electric field. The theory of electrothermally induced fluid flow is briefly described and compared with the experimental observations. Reasonable agreement is found between the experiments and the theory, with the light generating temperature gradients, and therefore gradients in fluid permittivity and conductivity, and the electric field responsible for the motive force.
    Journal of Physics D Applied Physics 12/1999; 33(2):L13. · 2.53 Impact Factor
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