From plant to product – basic principles, applications and future prospects

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The springtail cuticle as a blueprint for omniphobic surfaces

Omniphobic surfaces found in nature have great potential for enabling novel and emerging products and technologies to facilitate the daily life of human societies. One example is the water and even oil-repellent cuticle of springtails (Collembola). The wingless arthropods evolved a highly textured, hierarchically arranged surface pattern that affords mechanical robustness and wetting resistance even at elevated hydrostatic pressures. Springtail cuticle-derived surfaces therefore promise to overcome limitations of lotus-inspired surfaces (low durability, insufficient repellence of low surface tension liquids). In this review, we report on the liquid-repellent natural surfaces of arthropods living in aqueous or temporarily flooded habitats including water-walking insects or water spiders. In particular, we focus on springtails presenting an overview on the cuticular morphology and chemistry and their biological relevance. Based on the obtained liquid repellence of a variety of liquids with remarkable efficiency, the review provides general design criteria for robust omniphobic surfaces. In particular, the resistance against complete wetting and the mechanical stability strongly both depend on the topographical features of the nano- and micropatterned surface. The current understanding of the underlying principles and approaches to their technological implementation are summarized and discussed

Verhuellia is a segregate lineage in Piperaceae: more evidence from flower, fruit and pollen morphology, anatomy and development

Background and Aims The perianthless Piperales, i.e. Saururaceae and Piperaceae, have simple reduced flowers strikingly different from the other families of the order (e.g. Aristolochiaceae). Recent molecular phylogenies proved Verhuellia to be the first branch in Piperaceae, making it a promising object to study the detailed structure and development of the flowers. Based on recently collected material, the first detailed study since 1872 was conducted with respect to morphology, anatomy and development of the inflorescence, pollen ultrastructure and fruit anatomy. Methods Original Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Light Microscopy (LM) observations on Verhuellia lunaria were compared with Piperaceae, Saururaceae and fossils. Key results The inflorescence is an indeterminate spike with sessile flowers, each in the axil of a bract, developing in acropetal, helical succession. Flowers consist of two (occasionally three) stamens with basifixed tetrasporangiate anthers and latrorse dehiscence by a longitudinal slit. The gynoecium lacks a style but has three to four stigma branches and a single, basal orthotropous, and unitegmic ovule. The fruit is a drupe with large multicellular epidermal protuberances. The pollen is very small, inaperturate, and areolate with hemispherical microechinate exine elements. Conclusions Despite the superficial similarities with different genera of Piperaceae and Saururaceae, the segregate position of Verhuellia revealed by molecular phylogenetics is supported by morphological, developmental and anatomical data presented here. Unitegmic ovules and inaperturate pollen, which are synapomorphies for the genus Peperomia, are also present in Verhuellia

Bouncing or sticky droplets: impalement transitions on superhydrophobic micropatterned surfaces

When a liquid drops impinges a hydrophobic rough surface it can either bounce off the surface (fakir droplets) or be impaled and strongly stuck on it (Wenzel droplets). The analysis of drop impact and quasi static ''loading'' experiments on model microfabricated surfaces allows to clearly identify the forces hindering the impalement transitions. A simple semi-quantitative model is proposed to account for the observed relation between the surface topography and the robustness of fakir non-wetting states. Motivated by potential applications in microfluidics and in the fabrication of self cleaning surfaces, we finally propose some guidelines to design robust superhydrophobic surfaces.Comment: 7 pages, 5 figure

Contact angle measurements on superhydrophobic Carbon Nanotube Forests : effect of fluid pressure

In this paper the effect of pressure on the contact angle of a water drop on superhydrophobic Carbon Nanotube (CNT) forests is studied. Superhydrophobic CNT forests are obtained from a new and simple functionalization strategy, based on the gold-thiol affinity. Using a specifically devised experimental setup, we then show that these surfaces are able to withstand high excess pressures (larger than 10 kPa) without transiting toward a roughness-invaded state, therefore preserving their low adhesion properties. Together with the relatively low technical cost of the process, this robustness versus pressure makes such surfaces very appealing for practical integration into microfluidic systems.Comment: accepted for publication in Europhysics Letter

A lichen protected by a super-hydrophobic and breathable structure

A species of lichen, Lecanora conizaeoides, is shown to be super-hydrophobic. It uses a combination of hydrophobic compounds and multi-layered roughness to shed water effectively. This is combined with gas channels to produce a biological analogue of a waterproof, breathable garment. The particular lichen grows mostly during wet seasons and is unusually resistant to acid rain [Hauck, M., 2003. The Bryotogist 106(2), 257-269; Honegger, R., 1998. Lichenologist 30(3),193-212]. The waterproof, breathable surface allows this lichen to photosynthesise when other species are covered with a layer of water. In addition, rainwater runs off the surface of the organism, reducing its intake of water from above and probably contributing to its resistance to acid rain

Superhydrophobic surfaces: a model approach to predict contact angle and surface energy of soil particles

Wettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. The problem of determining contact angles and surface energy of powders, such as soil particles, remains unsolved. So far, several theories and approaches have been proposed, but formulation of surface and interfacial free energy, as regards its components, is still a very debatable issue. In the present study, the general problem of the interpretation of contact angles and surface free energy on chemically heterogeneous and rough soil particle surfaces is evaluated by a reformulation of the Cassie-Baxter equation, assuming that the particles are attached on to a plane and rigid surface. Compared with common approaches, our model considers a roughness factor that depends on the Young’s Law contact angle determined by the surface chemistry. Results of the model are discussed and compared with independent contact angle measurements using the Sessile Drop and the Wilhelmy Plate methods. Based on contact angle data, the critical surface tension of the grains were determined by the method proposed by Zisman. Experiments were made with glass beads and three soil materials ranging from sand to clay. Soil particles were coated with different loadings of dichlorodimethylsilane (DCDMS) to vary the wettability. Varying the solid surface tension using DCDMS treatments provided pure water-wetting behaviours ranging from wettable to extremely hydrophobic, with contact angles > 150°. Results showed that the critical surface energy measured on grains with the highest DCDMS loadings was similar to the surface energy measured independently on ideal DCDMS-coated smooth glass plates, except for the clay soil. Contact angles measured on plane surfaces were related to contact angles measured on rough grain surfaces using the new model based on the combined Cassie-Baxter Wenzel equation, which takes into account the particle packing density on the sample surface

The phylogenetic systematics of Spilomelinae and Pyraustinae (Lepidoptera: Pyraloidea: Crambidae) inferred from DNA and morphology

Spilomelinae and Pyraustinae form a species-rich monophylum of Crambidae (snout moths). Morphological distinction of the two groups has been difficult in the past, and the morphologically heterogenous Spilomelinae has not been broadly accepted as a natural group due to the lack of convincing apomorphies. In order to investigate potential apomorphic characters for Spilomelinae and Pyraustinae and to examine alternative phylogenetic hypotheses, we conduct a phylogenetic analysis using 6 molecular markers and 114 morphological characters of the adults representing 77 genera of Spilomelinae and 18 genera of Pyraustinae. The results of the analysis of the combined data strongly suggest that Spilomelinae and Pyraustinae are each monophyletic and sister to each other. Wurthiinae is confirmed as ingroup of Spilomelinae, and Sufetula Walker, 1859 as a non-spilomeline. Within Spilomelinae, several well supported clades are obtained, for which we propose a first phylogeny-based tribal classification, using nine available and four new names: Hydririni Minet, 1982 stat.rev., Lineodini Amsel, 1956 stat.rev., Udeini trib.n., Wurthiini Roepke, 1916 stat.rev., Agroterini Acloque, 1897 stat.rev., Spilomelini Guenée, 1854 stat.rev. (= Siginae Hampson, 1918), Herpetogrammatini trib.n., Hymeniini Swinhoe, 1900 stat.rev., Asciodini trib.n., Trichaeini trib.n., Steniini Guenée, 1854 stat.rev., Nomophilini Kuznetzov & Stekolnikov, 1979 stat.rev. and Margaroniini Swinhoe & Cotes, 1889 stat.rev. (= Dichocrociinae Swinhoe, 1900; = Hapaliadae Swinhoe, 1890; = Margarodidae Guenée, 1854). The available name Syleptinae Swinhoe, 1900 could not be assigned to any of the recovered clades. Three tribes are recognized in Pyraustinae: Euclastini Popescu-Gorj & Constantinescu, 1977 stat.rev., Portentomorphini Amsel, 1956 stat.rev. and Pyraustini Meyrick, 1890 stat.rev. (= Botydes Blanchard, 1840; = Ennychites Duponchel, 1845). The taxonomic status of Tetridia Warren, 1890, found to be sister to all other investigated Pyraustinae, needs further investigation. The four Spilomelinae tribes that are sister to all other, ‘euspilomeline’ tribes share several plesiomorphies with Pyraustinae. We provide morphological synapomorphies and descriptions for Spilomelinae, Pyraustinae and the subgroups recognised therein. These characters allow the assignment of additional 125 genera to Spilomelinae tribes, and additional 56 genera to Pyraustinae tribes. New and revised combinations are proposed: Nonazochis Amsel, 1956 syn.n. of Conchylodes Guenée, 1854, with Conchylodes graphialis (Schaus, 1912) comb.n.; Conchylodes octonalis (Zeller, 1873) comb.n. (from Lygropia); Hyperectis Meyrick, 1904 syn.n. of Hydriris Meyrick, 1885, with Hydriris dioctias (Meyick, 1904) comb.n., and Hydriris apicalis (Hampson, 1912) comb.n.; Conogethes pandamalis (Walker, 1859) comb.n. (from Dichocrocis); Arthromastix pactolalis (Guenée, 1854) comb.n. (from Syllepte); Prophantis coenostolalis (Hampson, 1899) comb.n. (from Thliptoceras); Prophantis xanthomeralis (Hampson, 1918) comb.n. (from Thliptoceras); Prophantis longicornalis (Mabille, 1900) comb.n. (from Syngamia); Charitoprepes apicipicta (Inoue, 1963) comb.n. (from Heterocnephes); Prenesta rubrocinctalis (Guenée, 1854) comb.n. (from Glyphodes); Alytana calligrammalis (Mabille, 1879) comb.n. (from Analyta). Epherema Snellen, 1892 stat.rev. with its type species E. abyssalis Snellen, 1892 comb.rev. is removed from synonymy with Syllepte Hübner, 1823. Ametrea Munroe, 1964 and Charitoprepes Warren, 1896 are transferred from Pyraustinae to Spilomelinae; Prooedema Hampson, 1891 from Spilomelinae to Pyraustinae; Aporocosmus Butler, 1886 from Spilomelinae to Odontiinae; Orthoraphis Hampson, 1896 from Spilomelinae to Lathrotelinae; Hydropionea Hampson, 1917, Plantegumia Amsel, 1956 and Munroe’s (1995) “undescribed genus ex Boeotarcha Meyrick” are transferred from Spilomelinae to Glaphyriinae.publishedVersio