UNS: Molecular Modeling of Wetting and Dewetting Transitions on Nanotextured Surfaces

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1511437 - PatelSurface roughness or texture can amplify the desirable properties of hydrophobic or "water-hating" surfaces. Such superhydrophobic surfaces have numerous applications due to their ability to repel water, to be self-cleaning, and to resist the formation of biofilms. However, the widespread adoption of these revolutionary materials has been thwarted by the fact that superhydrophobicity is fragile, and can be destroyed if water penetrates the surface texture. Thus, fully realizing the promise of these materials requires strategies to stabilize the fragile superhydrophobic state. The work proposed here will employ specialized molecular simulation methods to improve understanding of the connection between surface topography and the stability of the superhydrophobic state, and transform the ability to design robust superhydrophobic surfaces.The proposed work seeks to establish an understanding of how the thermodynamics of wetting-dewetting transitions on nanotextured surfaces are affected by the morphology of the surface nanotexture, and to use this understanding to inform the design of robust superhydrophobic and superoleophobic surfaces. Although wetting-dewetting transitions on textured surfaces have been studied extensively using macroscopic interfacial thermodynamics, a fundamental understanding of how such transitions are affected by collective water density fluctuations is missing. Our work promises to break new ground by using molecular simulations to characterize the free energetics of such wetting-dewetting transitions on nanotextured surfaces, the corresponding mechanistic pathways, and their dependence on external conditions such as pressure. The results of the work could also shed light on other phenomena where wetting-dewetting transitions on nanotextured surfaces are important, e.g., heterogeneous nucleation of bubbles and contact line pinning. By uncovering the fundamental connection between surface nanotexture and the stability of the superhydrophobic Cassie state, the proposed work has the potential to inform the rational design of robust superhydrophobic and superoleophobic surfaces, and bring about a transformative effect on the use of these materials in real-world applications that range from self-cleaning paints and coatings to water-repellent automobile windshields, and ice-resistant coatings for airplane wings and solar cells. The proposed work will lead to the training of a doctoral student and will also facilitate the mentoring of under-represented minority and undergraduate students by the PI. The findings of this project will also serve as the basis for augmenting a new course being developed by the PI at the University of Pennsylvania.