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I am conducting an experiment that requires comparison to models for a water droplet's change in size due to evaporation. I've found plenty of papers, but they all seem to require measurement of the drop's radius and/or height.

For the purposes of the experiment, I need a rate of change of the drops volume - $ \frac{dV}{dt} $ - related to temperature, humidity, local pressure, and surface tension. The contact angle starts at $ \approx 90 $ and a volume less than 60$\mu L$.

Does anyone know of such a paper? If so, please post the citation and/or a link. I suspect that the lack of papers would be due to the great age of the discovery,

Thanks

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If the contact angle is known to be near right, then the drop is roughly hemispherical, and you can find the geometry from the volume in a straight forward way, no? So, what exactly is the difficulty? –  dmckee Jun 27 '11 at 20:44
    
Unfortunately, not. As the drop shrinks two things may happen (or both, but usually one's dominant): the contact angle changes because the line (and therefore the radius) is "pinned" or the radius changes. The papers I've been able to find usually have one or the other or both in their change of volume (or change of mass) equations. I need just a general change of volume equation if such a thing exists. Either that, or I may simply have to take a radius measurement, but that is going to be a pain to put together. Thanks. –  pballjew Jun 27 '11 at 22:52

1 Answer 1

Well, I found a paper that works for my particular situation (a drop evaporating of PTFE) that does the trick. I doubt that very many people need this particular question answered, but here it is:

"Drop Evaporation on Solid Surfaces: Constant Contact Angle Mode" H. Ebril, G. McHale, and M Newton Langmuir 2002, 18, 2636-2641

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