M.M. Amrei

Predicting longevity of submerged superhydrophobic surfaces with parallel grooves

A mathematical framework is developed to predict the longevity of a submerged superhydrophobic surface made up of parallel grooves. Time-dependent integro-differential equations predicting the instantaneous behavior of the air–water interface are derived by applying the balance of forces across the air–water interface, while accounting for the dissolution of the air in water over time. The calculations start by producing a differential equation for the initial steady-state shape and equilibrium position of the air–water interface at t = 0. Analytical and/or numerical solutions are then developed to solve the time-dependent equations and to compute the volume of the trapped air in the grooves over time until a Wenzel state is reached as the interface touches the grooves bottom. For demonstration, a superhydrophobic surface made of parallel grooves is considered, and the influence of the grooves dimensions on the longevity of the surface under different hydrostatic pressures is studied. It was found that ...

Wetting states of superhydrophobic surfaces made of polygonal pores or posts

In this work, a mathematical framework is developed to describe some of the important intermediate wetting states of a superhydrophobic surface between the two extreme states of Cassie and Wenzel. The superhydrophobic surfaces considered here are comprised of sharp-edged polygonal pores or posts. Two different critical pressures are defined in this work, and used to distinguish pinned, partially pinned, and de-pinned air–water interfaces from one another. This information, in particular, is used to develop predictive expressions for the critical pressure and wetted area of the surfaces. Good agreement is observed between the predictions of our expressions and those obtained from numerical calculations or experiment. The work presented here compares the pressure-dependent performances of the superhydrophobic surfaces having different pore or post designs with one another.