Difference between revisions of "Pearl drops"

From Soft-Matter
Jump to: navigation, search
(Reference)
(Soft matter example)
Line 21: Line 21:
 
                 cosθ = (f<sub>sv</sub>-f<sub>sl</sub>)/f<sub>lv</sub>
 
                 cosθ = (f<sub>sv</sub>-f<sub>sl</sub>)/f<sub>lv</sub>
  
where f<sub>sv</sub>, f<sub>sl</sub>, f<sub>lv</sub> are surface tensions for solid/vapor, solid/liquid and liquid/vapor, respectively.
+
where f<sub>sv</sub>, f<sub>sl</sub>, f<sub>lv</sub> are surface tensions for solid/vapor, solid/liquid and liquid/vapor, respectively.
 +
 
 +
The contact angle can be changed by introducing textured surface. In nature, the contact angles of water drops on some leaves such as lotus or lily-water are around 160° by having rough surfaces [1]. Synthetically, it was found that a hydrophobic surface with surface texture had a contact angle around 170° for water. In this paper, the authors analyzed parameters affecting the contact angle and discussed data obtained from model surfaces.
  
 
==Reference==
 
==Reference==
  
 
1. C. Neinhuis and W. Barthlott, Planta 202, 1-8 (1997).
 
1. C. Neinhuis and W. Barthlott, Planta 202, 1-8 (1997).

Revision as of 00:56, 9 March 2009

By Sung Hoon Kang


Title: Pearl drops

Reference: J. Bico, C. Marzolin and D. Quere, Europhys. Lett. 47, 220-226 (1999).

Soft matter keywords

hydrophobic, surface roughness, contact angle, Young's equation, surface tension, Wenzel's equation

Abstract from the original paper

If deposited on a hydrophobic rough substrate, a small drop of water can look like a pearl, with a contact angle close to 180. We examine the conditions for observing such a phenomenon and show practical achievements where the contact angle can be predicted and thus quantitatively tuned by the design of the surface microstructure.

Soft matter example

For a flat uniform solid, the contact angle of a drop is given by Young's equation:

               cosθ = (fsv-fsl)/flv

where fsv, fsl, flv are surface tensions for solid/vapor, solid/liquid and liquid/vapor, respectively.

The contact angle can be changed by introducing textured surface. In nature, the contact angles of water drops on some leaves such as lotus or lily-water are around 160° by having rough surfaces [1]. Synthetically, it was found that a hydrophobic surface with surface texture had a contact angle around 170° for water. In this paper, the authors analyzed parameters affecting the contact angle and discussed data obtained from model surfaces.

Reference

1. C. Neinhuis and W. Barthlott, Planta 202, 1-8 (1997).