(37b) A Simple-to-Apply Predictive Wetting Model for Textured (Rough/Patterned) Surfaces and the Role of Re-Entrant Cavities
In general, when liquid is placed on any textured surface, the liquid can either (1) partially- or (2) fully-fill the cavities. Both states (partially- or fully-filled) can occur inside and/or outside (by condensation) of the droplet (bulk liquid). Importantly, the macroscopic contact angles manifested for each state can be significantly different, and either of these states can be a transient (unstable) state, a kinetically-trapped (short or long-lived) metastable state, or the thermodynamic equilibrium state. Utilizing an energy minimization approach, we derive a â??general wetting modelâ?? that (1) predicts apriori the state (partially- or fully-filled) of the cavities both under (in contact with) and outside of the liquid droplet, and the corresponding macroscopic contact angles on any type of textured surface; (2) allows for determination of the conditions under which metastable states exist; and (3) allows for engineering of specific nano/micro- textures that yield any desired macroscopic contact angle, Î¸t, for a given intrinsic contact angle Î¸0 (contact angle on smooth and flat surface).
During this talk, our â??general wetting modelâ?? will be discussed. In addition, we will demonstrate how this model can be used to design specific nano- and micro- textures to yield any desired macroscopic contact angle. Controlling the macroscopic contact angle, whether above or below the intrinsic contact angle, is desirable for many applications including both non-wetting, self-cleaning and anti-fouling surfaces, and completely-wetting/spreading applications, such as cosmetics and lubricant fluids.