Hello, good morning!

Nice picture. However it seems that it has nothing to do with a real water droplet on a non reactive surface. As you say, there was an obvious reaction of water with hydromagnesite, with the formation of some solid hydrated compound  which grew  with a clear tendency to produce a faceted shape.  It could be interesting to obtain a vertical section of the "drop"/substrate in order to study the interfacial shape and the variation in  its composition along the vertical axis.  Best wishes!

A. Passerone

Thanks Prof. Passerone for your comments and suggestions on my experimental observation. 

As Passerone mentioned the picture is not of  a flat subtract and probably you have a water film on top of a crystal. It will be interesting to see drop still attached to the needle.

In a different situation  a similar picture can be obtained after measuring advancing-receding crude oil- water contact angle and when the oil forms a "skin" on the interface. When the oil is withdrawn a portion I left attached to the surface indication the disappearance of the water molecular film.The oil-solid-water contact line gets pinned to the edge the new oil wet region.

This is used to  determine changes in wettability and adhesion. The oil-solid-water contact line gets pinned on the oil wet region 

Thanks Prof. Grattoni. May I know the conclusion of this result. Is it conforms the hydrophillic character of material ?

The conclusion from the oil adhesion test is that the region in contact with oil has become hydrophobic. By changing the pH and salinity of water the conditions where adhesion happens can be identified,

Hello U. Chinna Rajesh,

First of all I guess the right figure (within the file) is after the experiment and clearly shows a rapture of your sample and a hill-like structure. As far as I can judge your sample swells during the application of the drop resulting in a rupture of the material and instead of measuring a drop of water your measured the “hill” (the sharp borders and the tip of the “droplet” is not possible for liquids). I would suggest to expose the material to saturated water atmosphere to prevent breaking (normally CA-measurements should be performed in saturated vapour phase of the chosen liquid with well-defined temperature). Different points (roughness, advancing, receding) as mentioned Carlos Grattoni have also to be considered. If water will not work you have to perform your experiment with a non-reactive pure liquid.

Regards Michael Schmitt

Thanks Prof. Schmitt, 

We will try to analyze it as per your suggestions.