receding textured contact angles had wide variations. Due to the high aspect ratios and

significant roughness of the textured areas, air is trapped in the grooves when the

advancing front of the liquid passes over. As can be seen by Figure 3.10, the advancing

force decreases as the liquid front reaches the texture, which in effect is increasing the

resistance of the water to the film penetration. As it encounters areas of low surface

energy air trapped in between the grooves, the water adheres to the ridges until the

surface tension is overcome and it can bridge to the next ridge.



 Textured Silicone Elastomer
 20% wt/wt. 5000 cSt oil


150
100
 50
 0
 -50
-100
-150
-200
-250
-300
-350


Position (mm)


Figure 3.10


Force distance curve from DCA on a textured silicone elastomer substrate


Optical Profilometry

 Optical profilometry is a useful tool for characterizing the shape and 3-D features

of textured substrates. It uses white light interferometry to determine the topography of a

substrate without contacting the surface. It also has the great advantage that no surface