Difference between revisions of "Wetting"

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==Cassie and Wenzel States==
 
==Cassie and Wenzel States==
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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.

Diagram showing states for a liquid on a surface with (A) little wetting, (B) moderate wetting, and (C) high wetting. (Taken fromWikipedia Article )

See also:

Wetting from Lectures for AP225.

Wikipedia Article

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:

Controlled switching of the wetting behavior of biomimetic surfaces with hydrogel-supported nanostructures

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

Pitcher plant inspired non-stick surface