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Stationary electro-osmotic flow driven by ac fields around insulators

Stationary electro-osmotic flow driven by ac fields around insulators
Stationary electro-osmotic flow driven by ac fields around insulators
Electric fields are commonly used for manipulating particles and liquids in microfluidic systems. In this work, we report stationary electro-osmotic flow vortices around dielectric micropillars induced by ac electric fields in electrolytes. The flow characteristics are theoretically predicted based on the well-known phenomena of surface conductance and concentration polarization around a charged object. The stationary flows arise from two distinct contributions working together: an oscillating nonuniform zeta potential induced around the pillar and a rectified electric field induced by the ion concentration gradients. We refer to this fluid flow as concentration-polarization electro-osmosis (CPEO). We present experimental data in support of the theoretical predictions. The magnitude and frequency dependence of the electro-osmotic velocity are in agreement with the theoretical estimates and are significantly different from predictions based on the standard theory for induced-charge electro-osmosis, which has previously been postulated as the origin of the stationary flow around dielectric objects. In addition to furthering our understanding of the influence of ac fields on fluid flows, we anticipate that this work will also expand the use of ac fields for flow control in microfluidic systems.
2331-7019
Calero, Víctor
4c270680-a83d-4c15-9cc6-df3fd34b79df
Fernández-Mateo, Raúl
3ed21318-e9d8-4d7c-a2e2-a5f77a738e92
Morgan, Hywel
de00d59f-a5a2-48c4-a99a-1d5dd7854174
García-Sánchez, Pablo
6639bc8e-9568-43ba-b029-67d7f7e4363c
Ramos, Antonio
ae174961-dbc5-44ec-bdca-7b90e247637b
Calero, Víctor
4c270680-a83d-4c15-9cc6-df3fd34b79df
Fernández-Mateo, Raúl
3ed21318-e9d8-4d7c-a2e2-a5f77a738e92
Morgan, Hywel
de00d59f-a5a2-48c4-a99a-1d5dd7854174
García-Sánchez, Pablo
6639bc8e-9568-43ba-b029-67d7f7e4363c
Ramos, Antonio
ae174961-dbc5-44ec-bdca-7b90e247637b

Calero, Víctor, Fernández-Mateo, Raúl, Morgan, Hywel, García-Sánchez, Pablo and Ramos, Antonio (2021) Stationary electro-osmotic flow driven by ac fields around insulators. Physical Review Applied, 15 (1), [014047]. (doi:10.1103/PhysRevApplied.15.014047).

Record type: Article

Abstract

Electric fields are commonly used for manipulating particles and liquids in microfluidic systems. In this work, we report stationary electro-osmotic flow vortices around dielectric micropillars induced by ac electric fields in electrolytes. The flow characteristics are theoretically predicted based on the well-known phenomena of surface conductance and concentration polarization around a charged object. The stationary flows arise from two distinct contributions working together: an oscillating nonuniform zeta potential induced around the pillar and a rectified electric field induced by the ion concentration gradients. We refer to this fluid flow as concentration-polarization electro-osmosis (CPEO). We present experimental data in support of the theoretical predictions. The magnitude and frequency dependence of the electro-osmotic velocity are in agreement with the theoretical estimates and are significantly different from predictions based on the standard theory for induced-charge electro-osmosis, which has previously been postulated as the origin of the stationary flow around dielectric objects. In addition to furthering our understanding of the influence of ac fields on fluid flows, we anticipate that this work will also expand the use of ac fields for flow control in microfluidic systems.

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Stationary Electro-osmotic Flow Driven by ac Fields around Insulators - Accepted Manuscript
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Accepted/In Press date: 14 December 2020
Published date: 26 January 2021

Identifiers

Local EPrints ID: 447481
URI: http://eprints.soton.ac.uk/id/eprint/447481
ISSN: 2331-7019
PURE UUID: 8bcf8080-fc8f-4f83-a62c-04dd0edd1a52
ORCID for Hywel Morgan: ORCID iD orcid.org/0000-0003-4850-5676

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Date deposited: 12 Mar 2021 17:32
Last modified: 13 Mar 2021 02:38

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