Difference between revisions of "Wetting"
(→Introduction) |
(→Cassie and Wenzel States) |
||
| Line 13: | Line 13: | ||
==Cassie and Wenzel States== | ==Cassie and Wenzel States== | ||
| + | |||
| + | Surfaces can be made to be [[superhydrophobic]] or [[superhydrophilic]] by modification to have high aspect-ratio structures (micro-posts) on their surfaces, and chemical modification of these surfaces with [[hydrophobic]] or [[hydrophilic]] functional groups. Depending on the energetics of the surface, a drop of liquid on such a surface can be in either of two states--sitting on top of the micro-posts or sitting with the micro-posts embedded within it. The former is the [[Cassie state]] and the latter is the [[Wenzel state]]. | ||
== Keyword in references: == | == Keyword in references: == | ||
Revision as of 15:40, 7 December 2011
Chosen by Grant England
Introduction
Wetting refers to how well or poorly a liquid contacts a surface. Usually the term applies to water, where if a surface is hydrophobic it will not wet well while if it is hydrophilic it will wet well. The relative hydrophobicity or hydrophilicity of a substrate can be determined by measuring the contact angle of water with the surface. A liquid wets a surface better if it has a low contact angle with that surface. In general, if the contact angle is lower than 90 degrees, the liquid is considered to be wetting for that surface; while, if the contact angle is greater than 90 degrees, the liquid is non-wetting for the surface.
See also:
Wetting from Lectures for AP225.
Cassie and Wenzel States
Surfaces can be made to be superhydrophobic or superhydrophilic by modification to have high aspect-ratio structures (micro-posts) on their surfaces, and chemical modification of these surfaces with hydrophobic or hydrophilic functional groups. Depending on the energetics of the surface, a drop of liquid on such a surface can be in either of two states--sitting on top of the micro-posts or sitting with the micro-posts embedded within it. The former is the Cassie state and the latter is the Wenzel state.
Keyword in references:
Critical Casimir effect in three-dimensional Ising systems: Measurements on binary wetting films
Dewetting-Induced Membrane Formation by Adhesion of Amphiphile-Laden Interface
Encoding complex wettability patterns in chemically functionalized 3D photonic crystals
