Sessile Drop Evaporation on Surfaces of Various Wettability

This work experimentally investigates the evaporation rates of water drops on surfaces of various wettability. By measuring the temporal evolutions of the drop radius and contact angle, we find the qualitative difference between the evaporation behavior on hydrophilic surfaces where the contact radius remains constant initially and that on the superhydrophobic surfaces where the contact angle remains constant. Also, the evaporation rate is observed to depend on the surface material although the currently available models assume that the rate is solely determined by the drop geometry. Although the theory to explain this dependence on the surface remains to be pursued by the future work, we give the empirical relations that can be used to predict the drop volume evolution for each surface.