A swimming beauty - Superhydrophobic surfaces

Water repellent surfaces are under thorough study and various examples can be found throughout the plant and animal kingdom.

Particularily the characteristics of waxy surfaces are well known. By preventing water from touching the whole surface, elastic hair-like structures are responsible for the famous self-cleaning properties of Lotus leafs (Nelumbo nucifera).

Moreover, gracile Namib desert beetles (Stenocara gracilipes) survive in a most arid environment by extracting and collecting small water droplets from foggy coastal breezes, and the agile water bug (Notonecta glauca) glides quickly through water, because the protective 'airsuit' reduces drag to a minimum.

Culex pipiens

New evidence for the stunning diversity of superhydrophobic surfaces comes from a rather common species: Females of the europaen mosquito (Culex pipiens) place their eggs directly onto the water surface. Thereby, large aggregations of sometimes more than 100 eggs, which are called 'egg rafts' or 'swimming rafts', are becoming adhesive. To avoid immersion, each egg is covered with a microscopically small but precisely spun network (see above). The network traps a very thin boundary layer of air and thereby enables the egg to float and to remain permanently attached to neighboring eggs.

Rare insights into this beautiful and complex surface morphology can now be found in the Micronaut online gallery (see section: 'Editor's Picks' and 'Insect Kingdom')

A true story of success

Since the commercialization of the scanning-electron-microscope, superhydrophobic surfaces have been under extensive investigation and the research field of bioinspired technologies regularily leads to new and innove applications, e.g. to permanently clean kitchens and bathrooms, streamlined swimwear, or antibacterial deodorizing.

However, millions of years before scientists have begun to put together the keys for new technologies, mosquitoes have evolved a stunning egg with a water repellent surface. The adaptation represents an elegant way to circumnavigating temporary fluctuations of the water level, thereby preventing the water-bound larvae from hatching on dry land. The success of the adaptation is proved year after year - by millions of hungry bites!