Although understanding the wetting behavior of solid surfaces is crucial for numerous engineering applications, the mechanisms driving the motion of Wenzel drops on rough surfaces remain incompletely clarified. In this study, the contact angle and contact angle hysteresis of Wenzel drops on superhydrophobic surfaces are investigated from a thermodynamic perspective. The free energy of the system is theoretically analyzed, thereby determining the equilibrium contact angle. Based on the sessile drop method, the relationship between the free energy barrier and the drop volume is calculated quantitatively, enabling the determination of advancing and receding contact angles under zero free energy barrier conditions. The theoretical calculations agree well with the experimental data. These findings enhance the understanding of the interfacial interactions between Wenzel drops and superhydrophobic surfaces.

The low adhesion of water drops on superhydrophobic surfaces is a prerequisite for their widespread potential industrial applications. The wetting transition between different wetting states significantly influences the dynamic behavior of water drops on solid surfaces. Although some theoretical studies have addressed wetting transitions, the underlying mechanisms by which local micro- and nanostructure parameters on superhydrophobic surfaces affect the wetting transition have not been fully elucidated. This study investigates three-dimensional micropillared and micro/nanopillared superhydrophobic surfaces, deriving thermodynamically the equation for the free energy barrier of wetting transition, which is influenced by the overall roughness of the entire superhydrophobic surface and its local micro/nanostructures. Theoretical calculations are performed to investigate the effects of various micro- and nanostructure parameters on the free energy barrier and wetting transition. Based on the principle of energy minimization and the calculated free energy barrier, the possible wetting states on superhydrophobic surfaces are analyzed and compared with experimental results. This study contributes to the theoretical understanding of wetting transitions and may guide the design of superhydrophobic surfaces for diverse applications.