Influence of surface morphology and nano-structure on hydrophobicity: A molecular dynamics approach

In this study, water droplet behavior on hydrophobic and superhydrophobic surfaces with different morphologies and geometries has been investigated using molecular dynamics method. The contact angle and potential energy of water droplet on nanostructured surfaces has been evaluated as criteria of hydrophobicity. Results show that surface morphology, distance between columns, void fraction and the growth angle are the main parameters that significantly influence surface hydrophobicity. Wetting transition from Cassie-Baxter state to Wenzel state of simulated structures show that contact the angle decreases with increasing the distance between the columns. Superhydrophobic thin films with different shapes and dimensions, namely tetragonal helical sculptured, gecko feet and lotus leaves were designed and simulated. A contact angle of 155.7° for tetragonal helical sculptured structure is achieved. Interestingly, gecko feet and lotus leaves structures show oscillatory behavior of potential energy curves. It implies that these surfaces are more hydrophobic than other simulated films.