Biofouling on ships' hulls is a significant problem worldwide causing an increase in fuel consumption due to drag as well as mediating the spread of non-indigenous species. The economic impact of biofouling has been estimated to be $56M per year ($1 B over 15 years) for a single class of naval vessel. Biocides have been used in the past to combat biofouling, but the use of biocides in antifouling (AF) paints is becoming increasingly restricted.
The settlement of barnacle cyprids and algal zoospores is highly correlated with surface energies and surface wettabilities as is the removal of algal (Ulva) sporelings (young plants) and adhered diatoms. For example, cypris larvae of B. Amphitrite prefer to settle on surfaces with high wettability and high surface energy while algal zoospores prefer to settle on hydrophobic surfaces with low surface energy. Algal sporelings are more readily removed from surfaces with high wettability and high surface energy while diatoms are more readily removed from surfaces with high wettability and high surface energy. The adhesion of proteins to the xerogel surfaces follows the “Baier curve” with higher adhesion at both low and high surface energies and minimal adhesion near a critical surface tension, γC, of 20 to 25 mN m−1. NATURE in her diversity has created a situation where no previous single surface can have appropriate wettability/surface energy to prevent and/or release micro- and macrofouling of all types.