Advised by Stephen Garoff
In a series of experiments, lead was deposited on a variety of metallic and semiconductor surfaces, and allowed to reach its equilibrium configuration. Lead partially wetted two of these systems, forming droplets with non-zero contact angles on the bare solid surface. Lead pseudo partially wetted the other four systems, forming droplets with non- zero contact angles on top of a thin film of lead. In this talk we discuss the origins of this behavior
Thin films of fluids are typically described in terms of their disjoining pressure isotherms. Various models have been used to characterize the form of the disjoining pressure that would lead to pseudo partial wetting. Here, we use an energy minimization technique to identify isotherms that would lead to pseudo partial (and partial) wetting, and match their behavior to experimental systems. This matching is facilitated by measurements of the relevant surface energies and the film thickness.
Autophobing is a phenomenon related to pseudo partial wetting. Typically autophobing is observed as a fluid spreading and then retracting to form a drop on top of its own monolayer. Although the explanation of surfactant solution autophobing may be quite different, we present the conditions on the disjoining pressure and the kinetics for pure autophobing fluids. We will compare this to the metallic systems to explain why we consider the metallic systems to be pseudo partial wetting systems.