Cassie–Baxter and Wenzel States on a Nanostructured Surface: Phase Diagram, Metastabilities, and Transition Mechanism by Atomistic Free Energy Calculations

Abstract

In this work, we study the wetting of a surface decorated with one nanogroove by a bulk Lennard-Jones liquid at various temperatures and densities. We used atomistic simulations aimed at computing the free energy of the stable and metastable states of the system, as well as the intermediate states separating them. We found that the usual description in terms of Cassie-Baxter and Wenzel states is insufficient, as the system presents two states of the Cassie-Baxter type. These states are characterized by different curvatures of the meniscus. The measured free energy barrier separating the Cassie-Baxter from the Wenzel state (and vice versa) largely exceeds the thermal energy, attesting the existence of Cassie-Baxter/Wenzel metastabilities. Finally, we found that the Cassie-Baxter/Wenzel transition follows an asymmetric path, with the formation of a liquid finger on one side of the groove and a vapor bubble on the opposite side.

Mobility tensor of a sphere moving on a superhydrophobic wall: application to particle separation

“…A number of studies show that this is hardly strictly true also in simple systems [35,36,37,38]. However, the present results show that a detailed description of the surface pattern is not required unless the particle is very close to the wall.…”

Unraveling the Salvinia Paradox: Design Principles for Submerged Superhydrophobicity

“…[ 25 ] , which has been shown to be effective in dealing with superhydrophobicity (see refs. [ 26 ] and [ 27 ] and the Supporting Information). The advantage of using an atomistic description of the solid and of the liquid is that it relies on minimal assumptions.…”

Wetting state on hydrophilic and hydrophobic micro-textured surfaces: Thermodynamic analysis and X-ray visualization

“…Although wetting state has been extensively explored in previous reports, 13,14,16,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] the majority of these previous reports have focused on hydrophobic textured surfaces. Besides the wetting state was inferred from visible-wavelength images, making it difficult to identify the physical behavior at the vicinity of the micro-pillars on the test surfaces.…”