. SUPER HYDROPHOBICITY Soumya Ranjan Sahoo (711CH1025) NIT, Rourkela Abstract:
Superhydrophobicity as a sensation has turned into an increasing focus of research and technological movement, where its key viewpoints span surface chemistry, chemical physics, and cellular biology. Hydrophobic particles have a tendency to be non-polar and, accordingly, incline toward other neutral molecule and non-polar solvents. Hydrophobic atoms in water frequently bunch together, shaping micelles. Water on hydrophobic surfaces will display a high contact point. Superhydrophobic surfaces are exceptionally hydrophobic, i.e., greatly hard to wet. The contact angle of a water droplet surpasses 150° and the contact angle hysteresis is under 10°. This is also referred to as the Lotus impact, after the superhydrophobic leaves of the lotus plant.Rough and microstructured surfaces characteristically build hydrophobicity of hydrophobic surfaces through two altogether
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Modeling of Contact Angle for a Liquid in Contact with a Rough Surface
When a solid is in contact with liquid, the molecular attraction will reduce the energy of the system below that for the two separated surfaces. This is expressed by the Dupré equation Figure-1
2.1 Wenzel Model:
The Wenzel model (Robert N. Wenzel 1936) describes the homogeneous wetting regime, as seen in Figure 2, and is defined by the following equation for the contact angle on a rough surface.
where is the apparent contact angle which corresponds to the stable equilibrium state (i.e. minimum free energy state for the system). The roughness ratio, r, is a measure of how surface roughness affects a homogeneous surface. The roughness ratio is defined as the ratio of true area of the solid surface to the apparent area. Figure -2 : Wenzel