A better prediction of the contact angle for nanodroplets on chemically patterned surfaces by considering varied contact line width

Abstract

The contact angle of nanodroplets on chemically patterned surfaces can be predicted more accurately by introducing the contact line (CL) width. Rather than treating the CL width as a constant, it is proposed and validated for the first time that the CL width varies with different surface wettability, which enables more accurate prediction of contact angles. Assuming that the droplet maintains the shape of a spherical cap, a theory based on the local Cassie-Baxter equation which includes the effect of the CL width, is established to predict the contact angle. The CL width is determined through comprehensive molecular dynamics (MD) simulations. Several parameters are defined to describe the wettability of chemically patterned surfaces, the influence of which on the CL width is quantified. Based on this quantified relationship, an empirical formula is established, which can be used to determine the CL width of droplets. Further, prediction of the contact angle on chemically patterned surfaces can be achieved.