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The Salvinia effect describes the permanent stabilization of an air layer upon a 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〔J.-E. Melskotte, M. Brede, A. Wolter, W. Barthlott, A. Leder: ''Schleppversuche an künstlichen, Luft haltenden Oberflächen zur Reibungsreduktion am Schiff'' In: C. J. Kähler, R. Hain, C. Cierpka, B. Ruck, A. Leder, D. Dopheide (ed.): ''Lasermethoden in der Strömungsmesstechnik''. München 2013, Beitrag 53.〕). 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 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 from 2006 to 2015.〔〔 The best biological models are the floating ferns (Salvinia) with highly sophisticated hierarchically structured hairy surfaces,〔 and the back swimmers (''Notonecta'') with a complex double structure of hairs (Setae) and microvilli (microtrichia). Three of the ten known Salvinia species show a paradoxical chemical heterogenity:〔 hydrophilic hair tips, in addition to the super-hydrophobic plant surface, further stabilizing the air layer.〔 == ''Salvinia'', ''Notonecta'' and other organisms with air retaining surfaces == Immersed in water extremely water repellent (superhydrophobic), structured surfaces trap air between the structures and kept in place for a limited period of time. A silvery shine, due to the reflection of light at the interface of air and water, is visible on the submerged surfaces. The extremely unwettable leaves of lotus (''Nelumbo nucifera'') or lady's mantle (''Alchemilla'') are good examples. Long lasting air layers are known from under water living arthropods which breath via this air cap (palstron) atmen e. g. the water spider (''Argyroneta'') and the saucer bug (''Aphelocheirus''). Air layers are presumably also conductive to the reduction of friction in fast moving animals under water,as is the case for the back swimmer ''Notonecta''. Air layers presumably also conduce to reduce friction of fast moving animals under water (fishing spider ''Ancylomedes'') or at the water surface (back swimmer ''Notonecta''). The best known examples for long term air retention under water are the floating ferns of genus ''Salvinia''. About ten species of very diverse sizes are found in lentic water in all warmer regions of the earth, one widely spread species (''S. natans'') found in temperate climates can be even found in Central Europe. The ability to retain air is presumably a survival technique for these plants. The upper side of the floating leaves is highly water repellent and possesses highly complex and specie-specific very distinctive hairs. Some species present multicellular free-standing hairs of 0.3–3 mm length (e. g. ''S. cucullata'') while on others, two hairs are connected at the tips (e. g. ''S. oblongifolia''). ''S. minima'' and ''S. natans'' have four free standing hairs connected at a single base. The Giant Salvinia(''S. molesta''),as well as ''S. auriculata'', and other closely related species, display the most complex hairs: four hairs grow on a shared shaft; they are connected at their tips. These structures resemble microscopic eggbeaters and are therefore referred to as “eggbeater hairs”. The entireleaf surface, including the hairs, is covered with nanoscalewax crystals which are the reason for the water repellent properties of the surfaces. These leaf surfaces are therefore a classical example ofa “hierarchical structuring“.〔 The egg-beater hairs of ''Salvinia molesta'' and closely related species (e. g. ''Salvinia auriculata'') show an additional remarkable property. The four cells at the tip of each hair, as opposed to the rest of the hair, are free of wax and therefore hydrophilic; in effect, hydrophilic islands surrounded by a super-hydrophobic surface. This chemical heterogeneity,〔 the Salvinia paradox, enables a pinning of the air water interface to the plant and increases the pressure and longtime stability of the air layer.〔 The air retaining surface of the floating fern not only leads to a reduction in friction. The ecological extremely adaptable Giant Salvinia (''S. molesta'') is one of the most important invasive plants in all tropical and subtropical regions of the earth and is the cause of economic as well as ecologic problems.〔http://www.environment.gov.au/biodiversity/invasive/weeds/publications/guidelines/wons/pubs/s-molesta.pdf〕 Its growth rate might be the highest of all vascular plants. In the tropics and under optimal conditions, ''S. molesta'' can double its biomass within four days. The Salvinia effect, described here, most likely plays an essential role in its ecological success; the multilayered floating plant mats presumably maintain their function within the air-layer. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Salvinia effect」の詳細全文を読む スポンサード リンク
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