Advanced Self-Cleaning Surfaces

In the last fifteen years, an exponentially increasing number of scientific studies have focused on surface micro- and nano-engineering to develop surfaces capable of repelling liquids (and even solids, in the case of ice) by controlling wetting properties. Such interest primarily derives from nature observations, as some plant leaves have developed peculiar wetting properties for self-cleaning purposes, e.g., to remain clean by preventing the adhesion of particles or bacteria on their surfaces [1]. The classic example is Nelumbo nucifera, more commonly known as lotus, but other plants such as Colocasia esculenta, Mutisia decurrens [2] and Salvinia molesta [3] possess similar properties. All these plants are characterized by superhydrophobicity, which combines high water repellence with high mobility: these properties are given by a combination of chemistry (leaves are coated with intrinsically hydrophobic wax) and surface hierarchical topography at the micro- and nano-scale.