Directional flow induced by synchronized longitudinal and zeta-potential controlling AC-electrical fields

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Wouden, E.J. van der and Hermes, D.C. and Gardeniers, J.G.E. and Berg, A. van den (2006) Directional flow induced by synchronized longitudinal and zeta-potential controlling AC-electrical fields. Lab on a Chip, 6 (10). pp. 1300-1305. ISSN 1473-0197

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Abstract:Electroosmotic flow (EOF) in a microchannel can be controlled by electronic control of the surface charge using an electrode embedded in the wall of the channel. By setting a voltage to the electrode, the zeta-potential at the wall can be changed locally. Thus, the electrode acts as a "gate" for liquid flow, in analogy with a gate in a field-effect transistor. In this paper we will show three aspects of a Field Effect Flow Control (FEFC) structure. We demonstrate the induction of directional flow by the synchronized switching of the gate potential with the channel axial potential. The advantage of this procedure is that potential gas formation by electrolysis at the electrodes that provide the axial electric field is suppressed at sufficiently large switching frequencies, while the direction and magnitude of the EOF can be maintained. Furthermore we will give an analysis of the time constants involved in the charging of the insulator, and thus the switching of the zeta potential, in order to predict the maximum operating frequency. For this purpose an equivalent electrical circuit is presented and analyzed. It is shown that in order to accurately describe the charging dynamics and pH dependency the traditionally used three capacitor model should be expanded with an element describing the buffer capacitance of the silica wall surface.
Item Type:Article
Copyright:© 2006 Royal Society of Chemistry
Faculty:
Electrical Engineering, Mathematics and Computer Science (EEMCS)
Science and Technology (TNW)
Research Group:
Link to this item:http://purl.utwente.nl/publications/63751
Official URL:http://dx.doi.org/10.1039/b607403k
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