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According to Wikipedia, contact angle depends on the hydrophobicity of the surface and on thermodynamic equilibrium. But how does it in theory depend on the drop size? In other words, how would a theoretical curve of contact-angle ($\theta$) vs. drop-volume ($V$) look like, for a given surface?

  1. According to Drelich et. al. and to Good & Koo, in some liquids there's dependence, while in other the dependence is very weak.
  2. According to attension TN6, droplet volume "has significant influence on contact angle only with substrates that have large contact angle hysteresis (e.g. due to chemical heterogeneity and surface roughness)".
  3. According to C. Elif Cansoy, on superhydrophobic surfaces there's very small dependance between contact angle and drop volume.
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  • $\begingroup$ If I have a drop of a certain size and contact angle and I allow it to evaporate, invert likely it will keep the same contact area and change its contact angle. Is that what you meant by hysteresis? $\endgroup$
    – Floris
    Commented May 14, 2015 at 0:53
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    $\begingroup$ @Floris, I think what they meant in the paper is this. $\endgroup$
    – Sparkler
    Commented May 14, 2015 at 2:58

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Vafaei & Podowski derived such theory, which seems to agree well with experimental data. Another interesting relation between contact angle and drop height appears in a paper by Srinivasan et. al. (pp. 16-17):

Assessing the Accuracy of Contact Angle Measurements for Sessile Drops on Liquid-Repellent Surfaces, Siddarth Srinivasan

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    $\begingroup$ Link-only answers (and questions) are not encouraged on this site. It should not be necessary for the reader to study your links in order to understand your answer. You should summarise the relevant information from the link in your answer. $\endgroup$
    – sammy gerbil
    Commented Mar 30, 2018 at 20:32

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