Wetting Regimes and Wetting to non-Wetting Transitions via Ambient Exposure*

The interactions between liquid droplets and solids are paramount to applications including coatings, materials processing, spray cooling, and medical diagnostics. Although interactions can be controlled by altering the material and structure, the wettability of pristine smooth materials such as metals and rare earth oxides transitions from wetting to non-wetting as they are exposed to the ambient environment. In addition, micro- and/or nano-structures can empower wettability transitions from complete wetting (superhydrophilic) to non-wetting (superhydrophobic state). Other intermediate states are also observed on micro- and nano-structured surfaces function of the pristine material, which will be introduced and described. Transitions are explained in terms of volatile organic compounds VOCs (ever present in the ambient as a consequence of manmade practices) adsorption, which are hydrophobic in nature. The wetting to non-wetting transition dynamics are dependent on both material and surface structure, which are elucidated and introduced too. Finally, superhydrophobicity of copper oxide surfaces exposed to VOCs empowering dropwise condensation phase-change are shown. Findings should be carefully considered during materials processing, surface characterization, coating deposition, and spray cooling applications.