Wetting-state transition of random surfaces

Understanding the influence of topography on the wettability is essential to improve the modeling of super hydrophobic surfaces. Topography plays an integral role in the transition from a heterogeneous wetting state to a superhydrophobic wetting state. Herein, we report a significant experimental result, which is consistent with the theoretical formula that establishes the correlation between the surface and root mean square slope of surface structures. Moreover, this result allows one to study the influence of topography on the wetting-state transition, from the Wenzel to Cassie regimes. With this aim, hydrophobic and hydrophilic samples with graduated roughness were prepared. The topography and wettability were characterized by atomic force microscopy and the sessile drop technique, respectively. The experimental data fit the theoretical curve of the Wenzel roughness parameter as a function of the root mean square slope of the surface structures. Based on the contact angle, the slope range of the surface structure (0,49-1,04) was defined for the wetting-state transition. In addition, for the hydrophilic case, a divergence of the measured contact angle was noted in the Wenzel model, indicating a theoretical inconsistency.

Automated summary

Understanding the influence of topography on wettability is crucial for enhancing the modeling of super hydrophobic surfaces. This study demonstrates the correlation between the surface and root mean square slope of surface structures, validating its theoretical formula. The findings shed light on the influence of topography on wetting state transition, from the Wenzel to Cassie regimes.