Prediction of sessile drop evaporation considering surface wettability

Previous studies suggest that most theoretical models for drop evaporation based on an ideally simplified domain in which evaporation occurs do not correlate well with experimental results. The present paper proposes a novel empirical model f(theta) as a simple function of the contact angle theta, which is to be used to predict temporal evolution of a sessile water drop volume when the drop evaporates on surfaces of various wettabilities widely adopted in microelectronic engineering. For hydrophilic and hydrophobic surfaces, the evolution of the drop volume during the evaporation process can be predicted more accurately by representing f(theta) as an empirical linear function rather than by using previous theoretical models. Furthermore, the proposed model can account for the increased evaporation rate on smooth surfaces, thus providing a wide applicability to various substrate surfaces. For cases involving a superhydrophobic surface, f(theta) can be represented by an empirical constant because the contact angle remains constant during evaporation, which is in excellent agreement with the experimental observation. (C) 2011 Elsevier B.V. All rights reserved.