|M.Sc Student||Kestenberg Tomer|
|Subject||The Effect of Gravity on the Hysteresis of Contact Angles|
|Department||Department of Chemical Engineering||Supervisor||Professor Emeritus Abraham Marmur|
|Full Thesis text|
Wetting of surfaces is a fundamental research area which is relevant in many industrial and scientific domains such as coatings, paints, food, self-cleaning surfaces and more. Wetting of solid surfaces by liquid drops is usually described and quantified by an important parameter called the "contact angle". This parameter often used to characterize the interactions between the liquid and the solid surface. Another phenomenon which helps researchers to define and characterize surfaces called the "contact angle hysteresis". This phenomenon is what keeps a drop in place when it rests on a vertical surface. Over the last decade this phenomenon has become more and more important, due to the increase of studies on super-hydrophobic surfaces.
Despite its importance, the contact angle hysteresis phenomenon has yet to be studied in the present of gravity. It is obvious that wetting occurs in a gravitational environment and so the objective of this research was to investigate the effect of gravity on the hysteresis of contact angles.
In this thesis, theoretical models which describe wetting on a smooth rigid solid with continuous or discontinuous heterogeneity were formulated. Using these models the effect of gravity on the contact angles, energy barriers and the contact angle hysteresis were studied. The results clearly show that, gravity does not have any effect on the ideal contact angle (on a perfectly uniform surface) and on the contact angle hysteresis range.