Meniscus Shape During Immersion and Emersion Processes

CHANGE OF MENISCUS SHAPE DURING IMMERSION AND EMERSION PROCESSES 

The shape of the meniscus of water at the plate may either be depressed away or advanced toward the dry surface. In general, a hydrophobic surface would result in a depressed meniscus (0D,a,i 90 degrees, cos 0D,a,i 0) whereas a hydrophilic surface would result in an advanced meniscus (0D,a,i 90 degrees, cos 0D,a,i 0)- The meniscus can be clearly seen visually for extremely hydrophilic and hydrophobic surfaces. Surfaces with moderate hydrophilicity/hydrophobicity exhibit flat meniscus, which seems to be perpendicular to the surface (0D,a,i = 90 degrees, cos 0D,a,i =0). 

There is no significant transition stage on initial immersion of a hydrophilic surface because the dynamic meniscus is immediately developed on contact [(a) in 

It should be noted that on the receding cycle the wet plate surface has previously interacted with water molecules for a different period of time depending on the immersion depth of the plate. Therefore, the bottom deeper immersed portions of the plate interact with the water molecules for a longer period than the shallow immersed portions closer to the top of the plate. This causes small but continuous changes in the meniscus shape even after the three-phase contact line starts to move in the advancing and receding processes. 

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