Electroosmotic flow dipole: experimental observation and flow field patterning

TL;DR

This paper experimentally investigates electroosmotic dipole flows generated around localized surface charges in a Hele-Shaw cell, demonstrating flow patterning through controlled surface charge deposition without physical walls.

Contribution

It introduces a method to create and control electroosmotic dipole flows using localized surface charges, enabling complex flow patterning in microfluidic systems.

Findings

Localized surface charges induce dipole flow patterns.

Flow can be controlled by superposing multiple charge spots.

Flow patterning achieved without physical walls.

Abstract

We experimentally demonstrate the phenomenon of electroosmotic dipole flow that occurs around a localized surface charge region under the application of an external electric field in a Hele-Shaw cell. We use localized deposition of polyelectrolytes to create well-controlled surface charge variations, and show that for a disk-shaped spot, the internal pressure distribution that arises, results in uniform flow within the spot and dipole flow around it. We further demonstrate the superposition of surface charge spots to create complex flow patterns, without the use of physical walls.