Surface texture and surface chemistry both are important to design the highly hydrophobic surfaces. Tuning surface chemistry with chemical coating can improve the hydrophobic nature of the surface to a limit. Further increase in hydrophobicity requires an alteration in surface roughness. The present work proposes the randomly distributed nanoscale roughness for designing highly hydrophobic surface engineered particle (SEP) from the hydrophilic particle. An alkali medium is used to engineer the surface of the original particle (OP) for the different time intervals. The surface is thoroughly characterized by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy, and contact angle (CA) measurement. Results reveal that the hydrophobic CA up to 147° can be tuned by nanoscale surface roughness even after Si-OH incorporation on the surface. Moreover, the silanization of the OP and SEP surface further identifies that a gradual increase in CA beyond 113° is due to the favorable nano-scale surface roughness and its distribution on the surface of SEP. The study is first of its kind to achieve highly hydrophobic micron-size particle surface (CA ~ 147°) without coating of any low surface energy material.
Keywords: Hydrophobicity; Nano-roughness; Rose petal effect; Roughness distribution; Solid-liquid adhesion; Surface wetting; Water contact angle.
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