Bioinspired Self-cleaning Materials - Biotechnologies and Biomimetics for Civil Engineering - page 206

Chapter 9
Bioinspired Self-cleaning Materials

Maria Vittoria Diamanti and MariaPia Pedeferri

Abstract Among nature-inspired phenomena, the interactions of nanostructured
surfaces with water are probably the most studied ones, as well as the most
mimicked by science: geckos and spiders that can stick on smooth surfaces, beetles
that collect fog in the desert, gerridae that walk on water—which is the reason why
they are also called water striders, or pond skaters; all of these creatures owe their
characterizing properties to the influence of surface nanostructuring on their
affinity to water. Still, the most popular example of ''nature-created'' nanotech-
nology is the self-cleaning one, given by the onset of either superhydrophilicity,
superhydrophobicity, or superoleophobicity. This is allowed by particular condi-
tions of surface (photo)chemistry and structuring: the former is typical of TiO 2 -
containing surfaces, while the latter is based on the formation of air layers between
water and the surface nanometric protrusions, preventing the liquid from wetting
it. This chapter is dedicated to the mechanisms underlying bioinspired self-
cleaning and to the fields of application of these effects.

9.1 Water and Surfaces

9.1.1 An Introduction to Self-cleaning

Self-cleaning is clearly a fascinating concept, which reflects the capability of a
material to maintain its aspect unaltered in time, avoiding the deposition of dirt.
Such property first attracted producers and consumers working in the construction