Electroosmotic flow in a microcavity with nonuniform surface charges

David Halpern, Hsien-Hung Wei

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

In this work, we theoretically explore the characteristics of electroosmostic flow (EOF) in a microcavity with nonuniform surface charges. It is well known that a uniformly charged EOF does not give rise to flow separation because of its irrotational nature, as opposed to the classical problem of viscous flow past a cavity. However, if the cavity walls bear nonuniform surface charges, then the similitude between electric and flow fields breaks down, leading to the generation of vorticity in the cavity. Because this vorticity must necessarily diffuse into the exterior region that possesses a zero vorticity set by a uniform EOF, a new flow structure emerges. Assuming Stokes flow, we employ a boundary element method to explore how a nonuniform charge distribution along the cavity surface affects the flow structure. The results show that the stream can be susceptible to flow separation and exhibits a variety of flow structures, depending on the distributions of zeta potentials and the aspect ratio of the cavity. The interactions between patterned EOF vortices and Moffatt eddies are further demonstrated for deep cavities. This work not only has implications for electrokinetic flow induced by surface imperfections but also provides optimal strategies for achieving effective mixing in microgrooves.

Original languageEnglish
Pages (from-to)9505-9512
Number of pages8
JournalLangmuir
Volume23
Issue number18
DOIs
Publication statusPublished - 2007 Aug 28

Fingerprint

Microcavities
Flow structure
Surface charge
Vorticity
Flow separation
cavities
vorticity
flow separation
Charge distribution
Viscous flow
Zeta potential
Boundary element method
Aspect ratio
Flow fields
Vortex flow
Electric fields
vortices
uniform flow
Stokes flow
Defects

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Cite this

Halpern, David ; Wei, Hsien-Hung. / Electroosmotic flow in a microcavity with nonuniform surface charges. In: Langmuir. 2007 ; Vol. 23, No. 18. pp. 9505-9512.
@article{0b351a23386943098290f3c7f1eb6c52,
title = "Electroosmotic flow in a microcavity with nonuniform surface charges",
abstract = "In this work, we theoretically explore the characteristics of electroosmostic flow (EOF) in a microcavity with nonuniform surface charges. It is well known that a uniformly charged EOF does not give rise to flow separation because of its irrotational nature, as opposed to the classical problem of viscous flow past a cavity. However, if the cavity walls bear nonuniform surface charges, then the similitude between electric and flow fields breaks down, leading to the generation of vorticity in the cavity. Because this vorticity must necessarily diffuse into the exterior region that possesses a zero vorticity set by a uniform EOF, a new flow structure emerges. Assuming Stokes flow, we employ a boundary element method to explore how a nonuniform charge distribution along the cavity surface affects the flow structure. The results show that the stream can be susceptible to flow separation and exhibits a variety of flow structures, depending on the distributions of zeta potentials and the aspect ratio of the cavity. The interactions between patterned EOF vortices and Moffatt eddies are further demonstrated for deep cavities. This work not only has implications for electrokinetic flow induced by surface imperfections but also provides optimal strategies for achieving effective mixing in microgrooves.",
author = "David Halpern and Hsien-Hung Wei",
year = "2007",
month = "8",
day = "28",
doi = "10.1021/la701343s",
language = "English",
volume = "23",
pages = "9505--9512",
journal = "Langmuir",
issn = "0743-7463",
publisher = "American Chemical Society",
number = "18",

}

Electroosmotic flow in a microcavity with nonuniform surface charges. / Halpern, David; Wei, Hsien-Hung.

In: Langmuir, Vol. 23, No. 18, 28.08.2007, p. 9505-9512.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Electroosmotic flow in a microcavity with nonuniform surface charges

AU - Halpern, David

AU - Wei, Hsien-Hung

PY - 2007/8/28

Y1 - 2007/8/28

N2 - In this work, we theoretically explore the characteristics of electroosmostic flow (EOF) in a microcavity with nonuniform surface charges. It is well known that a uniformly charged EOF does not give rise to flow separation because of its irrotational nature, as opposed to the classical problem of viscous flow past a cavity. However, if the cavity walls bear nonuniform surface charges, then the similitude between electric and flow fields breaks down, leading to the generation of vorticity in the cavity. Because this vorticity must necessarily diffuse into the exterior region that possesses a zero vorticity set by a uniform EOF, a new flow structure emerges. Assuming Stokes flow, we employ a boundary element method to explore how a nonuniform charge distribution along the cavity surface affects the flow structure. The results show that the stream can be susceptible to flow separation and exhibits a variety of flow structures, depending on the distributions of zeta potentials and the aspect ratio of the cavity. The interactions between patterned EOF vortices and Moffatt eddies are further demonstrated for deep cavities. This work not only has implications for electrokinetic flow induced by surface imperfections but also provides optimal strategies for achieving effective mixing in microgrooves.

AB - In this work, we theoretically explore the characteristics of electroosmostic flow (EOF) in a microcavity with nonuniform surface charges. It is well known that a uniformly charged EOF does not give rise to flow separation because of its irrotational nature, as opposed to the classical problem of viscous flow past a cavity. However, if the cavity walls bear nonuniform surface charges, then the similitude between electric and flow fields breaks down, leading to the generation of vorticity in the cavity. Because this vorticity must necessarily diffuse into the exterior region that possesses a zero vorticity set by a uniform EOF, a new flow structure emerges. Assuming Stokes flow, we employ a boundary element method to explore how a nonuniform charge distribution along the cavity surface affects the flow structure. The results show that the stream can be susceptible to flow separation and exhibits a variety of flow structures, depending on the distributions of zeta potentials and the aspect ratio of the cavity. The interactions between patterned EOF vortices and Moffatt eddies are further demonstrated for deep cavities. This work not only has implications for electrokinetic flow induced by surface imperfections but also provides optimal strategies for achieving effective mixing in microgrooves.

UR - http://www.scopus.com/inward/record.url?scp=34548534642&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34548534642&partnerID=8YFLogxK

U2 - 10.1021/la701343s

DO - 10.1021/la701343s

M3 - Article

VL - 23

SP - 9505

EP - 9512

JO - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 18

ER -