Reversible Dewetting of Thin Lubricating Films Underneath Aqueous Drops Using External Electric Field

TL;DR

This study demonstrates reversible dewetting and rewetting of thin lubricating films under aqueous drops on slippery surfaces controlled by an external electric field, enabling on-demand stability manipulation of the films.

Contribution

It introduces a method to reversibly control thin film stability using electric fields, revealing spinodal dewetting behavior and pattern randomness over multiple cycles.

Findings

Dewetting occurs via spinodal process under electric field.

Rewetting restores a uniform film after dewetting.

Dewetting patterns are random and uncorrelated across cycles.

Abstract

The stability of thin liquid films on a surface depends on the excess free energy of the system involving various short-range and long-range interactions. In an unstable condition, thin liquid films may dewet into multiple small-sized droplets via spinodal, homogeneous, or heterogeneous nucleation process. However, if the total excess free energy of the system can be manipulated using an external stimulus, one can control the stability of thin liquid films on demand. Here, we study the reversible dewetting process of thin lubricating films underneath aqueous drops on slippery surfaces using an external electric field. Upon applying voltage, stable thin lubricating films dewet in a manner identical to the spinodal dewetting of nanometer-thick liquid films. Upon removing the applied voltage, the dewetted droplets spread, coalesce with neighboring ones, and form a uniform film again, however the time taken during rewetting is very different compared to dewetting. The characteristic features of both the dewetting and rewetting processes are present over multiple cycles. Due to the random nature of the spinodal dewetting process, the final dewetting pattern does not show any correlation over multiple dewetting cycles.