Figure 1.

Biological role models of air-retaining Salvinia effect surfaces. a) The floating fern Salvinia molesta has one of the most complex surface structures in plants. Reproduced with permission from [5], copyright 2010 Wiley-VCH Verlag GmbH & Co. KGaA. b) With its egg-beater-like trichomes with terminal hydrophilic anchor cells, Salvinia is able to maintain air layers for many weeks under water. c) The backswimmer Notonecta keeps a persistent air layer on its forewings even when it moves underwater at high velocity. The silvery shine is due to the total internal reflection of light at the air–water interface. d) The backswimmers double structure of longer hairs (grey and yellow) and a dense “carpet” of smaller hairs (microvilli, green) is responsible for the long-term air-retention capability.