(658c) Wetting-Dewetting Transitions on Superhydrophobic Surfaces

Nano-textured surfaces can have water contact angles approaching 180^o, making them incredibly useful as self-cleaning, fouling-resistant and icephobic surfaces. However, such “superhydrophobic” surfaces are usually fragile, because the system is superhydrophobic only when water sits on a cushion of air in the so-called Cassie state. Such a Cassie state is metastable, whereas the non-functional Wenzel state, which results when water penetrates the grooves on the surface, is thermodynamically favorable. Using specialized molecular dynamics simulations, here we study model nanotextured surfaces to understand the thermodynamics and the kinetics of the Cassie to Wenzel transition. By uncovering how various surface geometrical parameters affect the free energy differences and the kinetic barriers between the two states, we hope to inform the design of surfaces with a thermodynamically stable, superhydrophobic Cassie state.