The Salvinia effect describes the permanent stabilization of an air layer upon a hierarchically structured surface submerged in water. Based on biological models (e.g. the floating ferns Salvinia, backswimmer Notonecta), biomimetic Salvinia-surfaces are used as drag reducing coatings (up to 30% reduction were previously measured on the first prototypes.[1][2] When applied to a ship hull, the coating would allow the boat to float on an air-layer, reducing energy consumption and emissions. Such surfaces require an extremely water repellent super-hydrophobic surface and an elastic hairy structure in the millimeter range to entrap air while submerged. The Salvinia effect was discovered by the biologist and botanist Wilhelm Barthlott (University of Bonn) and his colleagues and has been investigated on several plants and animals since 2002. Publications and patents were published between 2006 and 2016.[3] The best biological models are the floating ferns (Salvinia) with highly sophisticated hierarchically structured hairy surfaces,[4] and the back swimmers (e.g.Notonecta) with a complex double structure of hairs (setae) and microvilli (microtrichia). Three of the ten known Salvinia species show a paradoxical chemical heterogeneity: hydrophilic hair tips, in addition to the super-hydrophobic plant surface, further stabilizing the air layer.[5]
- ^ Barthlott, W., Mail, M., & C. Neinhuis, (2016) Superhydrophobic hierarchically structured surfaces in biology: evolution, structural principles and biomimetic applications. Phil. Trans. R. Soc. A 374.2073 DOI:10.1098/rsta.2016.0191
- ^ Barthlott, W., Mail, M., Bhushan, B., & K. Koch. (2017). Plant Surfaces: Structures and Functions for Biomimetic Innovations. Nano-Micro Letters, 9(23), doi:10.1007/s40820-016-0125-1.
- ^ Barthlott, W., Wiersch, S., Čolić, Z., & K. Koch, (2009) Classification of trichome types within species of the water fern Salvinia, and ontogeny of the egg-beater trichomes. Botany. 87(9). pp 830–836, DOI:10.1139/B09-048.
- ^ Barthlott, W., Schimmel, T., Wiersch, S., Koch, K., Brede, M., Barczewski, M., Walheim, S., Weis, A., Kaltenmaier, A., Leder, A., & H. Bohn, (2010). The Salvinia Paradox: Superhydrophobic surfaces with hydrophilic pins for air retention under water. Advanced Materials. 22(21). pp 2325–2328, DOI:10.1002/adma.200904411.
- ^ Ditsche-Kuru, P., Schneider, E.S., Melskotte, J.-E., Brede, M., Leder, A., & W. Barthlott, (2011) Superhydrophobic surfaces of the water bug Notonecta glauca: a model for friction reduction and air retention. Beilstein Journal of Nanotechnology. 2(1). pp 137–144, DOI:10.3762/bjnano.2.17.