Fully reversible transition from Wenzel to Cassie-Baxter states on corrugated superhydrophobic surfaces

TL;DR

This paper demonstrates a simple, reversible, and barrierless method to switch between Wenzel and Cassie-Baxter wetting states on textured surfaces using electrowetting, enabling precise control of fluid dynamics.

Contribution

It introduces a new design paradigm with parallel grooves of specific aspect ratio for reversible wetting transitions without energy barriers.

Findings

Reversible switching between wetting states observed experimentally.

Theoretical model and lattice-Boltzmann simulations support the transition mechanism.

Barrierless transition pathway confirmed for the first time.

Abstract

Liquid drops on textured surfaces show different dynamical behaviors depending on their wetting states. They are extremely mobile when they are supported by composite solid-liquid-air interfaces (Cassie-Baxter state) and immobile when they fully wet the textured surfaces (Wenzel state). By reversibly switching between these two states, it will be possible to achieve large control over the fluid dynamics. Unfortunately, these wetting transitions are usually prevented by surface energy barriers. We demonstrate here a new and simple design paradigm, consisting of parallel grooves of appropriate aspect ratio, that allows for a controlled, barrierless, and reversible switching of the wetting states upon the application of electrowetting. We report a direct observation of the barrierless dynamical pathway for the reversible transitions between the Wenzel (collapsed) and the Cassie-Baxter (suspended) states and present a theory that accounts for these transitions, including detailed lattice-Boltzmann simulations.