An electro-hydrodynamics modeling of droplet actuation on solid surface by surfactant-mediated electro-dewetting

TL;DR

This paper develops an electro-hydrodynamics model to control droplet behavior on surfaces using electric fields and surfactants, enabling manipulation of wetting states for microfluidic applications.

Contribution

It introduces a unified model combining electro-hydrodynamics and surfactant dynamics to predict and control droplet actuation on surfaces under electric fields.

Findings

Electric fields promote dewetting by attracting ionic surfactants.

Electric fields promote rewetting by repelling ionic surfactants.

The model accurately reproduces microfluidic operations like shifting and rewetting.

Abstract

We propose an electro-hydrodynamics model to describe the dynamic evolution of a slender drop containing a dilute ionic surfactant on a naturally wettable surface, with a varying external electric field. This unified model reproduces fundamental microfluidic operations controlled by electrical signals, including dewetting, rewetting, and droplet shifting. In this paper, lubrication theory analysis and numerical simulations illustrate how to electrically control the wettability of surface via the charged surfactant. Our numerical results show that electric field promotes dewetting by attracting ionic surfactants onto the transition thin-film region and promotes rewetting by attracting them away from the region.