Thermodynamic analysis on superhydrophobicity based on the design of a pillar model

Abstract

Superhydrophobicity and the fabrication of superhydrophobic surfaces (SHSs) have inspiring applications in microfluidics, self-cleaning and drag-reducing coatings. However, the thermodynamic mechanisms responsible for superhydrophobicity are not completely clear yet. Therefore, we propose a three-dimensional (3-D) model based on the scanning electron microscopy (SEM) of cicada wings and artificial SHSs with the purpose of determining and explaining contact angle hysteresis (CAH) in quantity. Subsequently, the relationships between contact angle (CA), CAH, changes in free energy (CFE), free energy barrier (FEB), adhesion work (W_a), spreading coefficient (S_L/S) and microstructures of the surfaces are established. The negative and positive correlations between the property parameters are quantitatively discussed. This can potentially play a theoretical guiding role in the fabrication of SHSs and improve on the understanding of the physical nature of SHSs.