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Wilhelm Barthlott - One of the best experts on this subject based on the ideXlab platform.
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Superhydrophobic Vertically Aligned Carbon Nanotubes for Biomimetic Air Retention under Water (Salvinia Effect)
Advanced Materials Interfaces, 2017Co-Authors: Deepu J Babu, Matthias Mail, Wilhelm Barthlott, Jorg J SchneiderAbstract:The Salvinia effect refers to the stable retention of an air layer when submerged in water and is a result of complex hierarchical structuring, ultimate example of which is the surface of the floating fern Salvinia molesta. The air retention capability is technologically interesting as the retained air layer reduces drag force, prevents biofouling, and serves sensory functions. Air retention on artificial materials is currently limited to very few materials and is often a result of micrometer sized surface structures obtained by complex lithography techniques. In the present work, the air retention capabilities of superhydrophobic vertically aligned carbon nanotubes (VACNTs) are explored for the first time and the retained air layer is characterized by atomic force microscopy and confocal microscopy techniques. While the as-prepared VACNTs retained only small pockets of air when submerged in water, superhydrophobic and regrown VACNT structures are found to be capable of retaining a continuous thick layer over extended period of time. The stable air retention capabilities of these nanostructured VACNT surfaces hold promising pathways for the development of biomimetic sensor systems.
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SYMPOSIUM Layers of Air in the Water beneath the Floating Fern Salvinia are Exposed to Fluctuations in Pressure
2016Co-Authors: Matthias Mayser, Wilhelm BarthlottAbstract:Synopsis Superhydrophobic, hierarchically structured, technical surfaces (Lotus-effect) are of high scientific and eco-nomic interest because of their remarkable properties. Recently, the immense potential of air-retaining superhydrophobic surfaces, for example, for low-friction transport of fluids and drag-reducing coatings of ships has begun to be explored. A major problem of superhydrophobic surfaces mimicking the Lotus-effect is the limited persistence of the air retained, especially under rough conditions of flow. However, there are a variety of floating or diving plant and animal species that possess air-retaining surfaces optimized for durable water-repellency (Salvinia-effect). Especially floating ferns of the genus Salvinia have evolved superhydrophobic surfaces capable of maintaining layers of air for months. Apart from maintaining stability under water, the layer of air has to withstand the stresses of water pressure (up to 2.5 bars). Both of these aspects have an application to create permanent air layers on ships ’ hulls. We investigated the effect of pressure on air layers in a pressure cell and exposed the air layer to pressures of up to 6 bars. We investigated the suppression of the air layer at increasing pressures as well as its restoration during decreases in pressure. Three of the four examined Salvinia species are capable of maintaining air layers at pressures relevant to the conditions applying to ships ’ hulls. High volumes of air per surface area are advantageous for retaining at least a partial Cassie–Baxter-state under pressure, which also helps in restoring the air layer after depressurization. Closed-loop structures such as the baskets at the top of the ‘‘egg-beate
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elasticity of the hair cover in air retaining Salvinia surfaces
Applied Physics A, 2015Co-Authors: Elena V Gorb, Stanislav N. Gorb, Petra Ditsche, Matthias Mayser, Thomas Schimmel, Wilhelm BarthlottAbstract:Immersed in water superhydrophobic surfaces (e.g., lotus) maintain thin temporary air films. In certain aquatic plants and animals, these films are thicker and more persistent. Floating ferns of the genus Salvinia show elaborated hierarchical superhydrophobic surface structures: a hairy cover of complex trichomes. In the case of S. molesta, they are eggbeater shaped and topped by hydrophilic tips, which pin the air-water interface and prevent rupture of contact. It has been proposed that these trichomes can oscillate with the air-water interface, when turbulences occur and thereby stabilize the air film. The deformability of such arrays of trichomes requires a certain elasticity of the structures. In this study, we determined the stiffness of the trichome coverage of S. molesta and three other Salvinia species. Our results confirm the elasticity of the trichome coverage in all investigated Salvinia species. We did not reveal a clear relationship between the time of air retention and stiffness of the trichome coverage, which means that the air retention function is additionally dependent on different parameters, e.g., the trichome shape and surface free energy. These data are not only interesting for Salvinia biology, but also important for the development of biomimetic air-retaining surfaces.
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layers of air in the water beneath the floating fern Salvinia are exposed to fluctuations in pressure
Integrative and Comparative Biology, 2014Co-Authors: Matthias Mayser, Wilhelm BarthlottAbstract:Superhydrophobic, hierarchically structured, technical surfaces (Lotus-effect) are of high scientific and economic interest because of their remarkable properties. Recently, the immense potential of air-retaining superhydrophobic surfaces, for example, for low-friction transport of fluids and drag-reducing coatings of ships has begun to be explored. A major problem of superhydrophobic surfaces mimicking the Lotus-effect is the limited persistence of the air retained, especially under rough conditions of flow. However, there are a variety of floating or diving plant and animal species that possess air-retaining surfaces optimized for durable water-repellency (Salvinia-effect). Especially floating ferns of the genus Salvinia have evolved superhydrophobic surfaces capable of maintaining layers of air for months. Apart from maintaining stability under water, the layer of air has to withstand the stresses of water pressure (up to 2.5 bars). Both of these aspects have an application to create permanent air layers on ships' hulls. We investigated the effect of pressure on air layers in a pressure cell and exposed the air layer to pressures of up to 6 bars. We investigated the suppression of the air layer at increasing pressures as well as its restoration during decreases in pressure. Three of the four examined Salvinia species are capable of maintaining air layers at pressures relevant to the conditions applying to ships' hulls. High volumes of air per surface area are advantageous for retaining at least a partial Cassie-Baxter-state under pressure, which also helps in restoring the air layer after depressurization. Closed-loop structures such as the baskets at the top of the "egg-beater hairs" (see main text) also help return the air layer to its original level at the tip of the hairs by trapping air bubbles.
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measuring air layer volumes retained by submerged floating ferns Salvinia and biomimetic superhydrophobic surfaces
Beilstein Journal of Nanotechnology, 2014Co-Authors: Matthias Mayser, Holger F Bohn, Meike Reker, Wilhelm BarthlottAbstract:Some plants and animals feature superhydrophobic surfaces capable of retaining a layer of air when submerged under water. Longterm air retaining surfaces (Salvinia-effect) are of high interest for biomimetic applications like drag reduction in ship coatings of up to 30%. Here we present a novel method for measuring air volumes and air loss under water. We recorded the buoyancy force of the air layer on leaf surfaces of four different Salvinia species and on one biomimetic surface using a highly sensitive custom made strain gauge force transducer setup. The volume of air held by a surface was quantified by comparing the buoyancy force of the specimen with and then without an air layer. Air volumes retained by the Salvinia-surfaces ranged between 0.15 and 1 L/m2 depending on differences in surface architecture. We verified the precision of the method by comparing the measured air volumes with theoretical volume calculations and could find a good agreement between both values. In this context we present techniques to calculate air volumes on surfaces with complex microstructures. The introduced method also allows to measure decrease or increase of air layers with high accuracy in real-time to understand dynamic processes.
Steven L Chown - One of the best experts on this subject based on the ideXlab platform.
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the effects of acclimation and rates of temperature change on critical thermal limits in tenebrio molitor tenebrionidae and cyrtobagous Salviniae curculionidae
Journal of Insect Physiology, 2012Co-Authors: Jessica L Allen, Susana Clusellatrullas, Steven L ChownAbstract:Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing ther- mal environments on such survival. However, investigations of these limits may be affected by the circum- stances under which trials are undertaken. Only a few studies have examined these effects, and typically not for beetles. This group has also not been considered in the context of the time courses of acclimation and its reversal, both of which are important for estimating the responses of species to transient temper- ature changes. Here we therefore examine the effects of rate of temperature change on critical thermal maxima (CTmax) and minima (CTmin), as well as the time course of the acclimation response and its reversal in two beetle species, Tenebrio molitor and Cyrtobagous Salviniae. Increasing rates of temperature change had opposite effects on T. molitor and C. Salviniae .I nT. molitor, faster rates of change reduced both CTmax (c. 2 C) and CTmin (c. 3 C), while in C. Salviniae faster rates of change increased both CTmax (c. 6 C) and CTmin (c. 4 C). CTmax in T. molitor showed little response to acclimation, while the response to acclimation of CTmin was most pronounced following exposure to 35 C (from 25 C) and was complete within 24 h. The time course of acclimation of CTmax in C. Salviniae was 2 days when exposed to 36 C (from c. 26 C), while that of CTmin was less than 3 days when exposed to 18 C. In T. molitor, the time course of reacclimation to 25 C after treatments at 15 C and 35 C at 75% RH was longer than the time course of acclimation, and varied from 3-6 days for CTmax and 6 days for CTmin .I nC. Salviniae, little change in CTmax and CTmin (<0.5 C) took place in all treatments suggesting that reacclimation may only occur after the 7 day period used in this study. These results indicate that both T. molitor and C. Salviniae may be restricted in their ability to respond to transient temperature changes at short-time scales, and instead may have to rely on behavioral adjustments to avoid deleterious effects at high temperatures.
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the effects of acclimation and rates of temperature change on critical thermal limits in tenebrio molitor tenebrionidae and cyrtobagous Salviniae curculionidae
Journal of Insect Physiology, 2012Co-Authors: Jessica L Allen, Susana Clusellatrullas, Steven L ChownAbstract:Abstract Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing thermal environments on such survival. However, investigations of these limits may be affected by the circumstances under which trials are undertaken. Only a few studies have examined these effects, and typically not for beetles. This group has also not been considered in the context of the time courses of acclimation and its reversal, both of which are important for estimating the responses of species to transient temperature changes. Here we therefore examine the effects of rate of temperature change on critical thermal maxima (CTmax) and minima (CTmin), as well as the time course of the acclimation response and its reversal in two beetle species, Tenebrio molitor and Cyrtobagous Salviniae. Increasing rates of temperature change had opposite effects on T. molitor and C. Salviniae. In T. molitor, faster rates of change reduced both CTmax (c. 2 °C) and CTmin (c. 3 °C), while in C. Salviniae faster rates of change increased both CTmax (c. 6 °C) and CTmin (c. 4 °C). CTmax in T. molitor showed little response to acclimation, while the response to acclimation of CTmin was most pronounced following exposure to 35 °C (from 25 °C) and was complete within 24 h. The time course of acclimation of CTmax in C. Salviniae was 2 days when exposed to 36 °C (from c. 26 °C), while that of CTmin was less than 3 days when exposed to 18 °C. In T. molitor, the time course of reacclimation to 25 °C after treatments at 15 °C and 35 °C at 75% RH was longer than the time course of acclimation, and varied from 3–6 days for CTmax and 6 days for CTmin. In C. Salviniae, little change in CTmax and CTmin (
Jessica L Allen - One of the best experts on this subject based on the ideXlab platform.
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the effects of acclimation and rates of temperature change on critical thermal limits in tenebrio molitor tenebrionidae and cyrtobagous Salviniae curculionidae
Journal of Insect Physiology, 2012Co-Authors: Jessica L Allen, Susana Clusellatrullas, Steven L ChownAbstract:Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing ther- mal environments on such survival. However, investigations of these limits may be affected by the circum- stances under which trials are undertaken. Only a few studies have examined these effects, and typically not for beetles. This group has also not been considered in the context of the time courses of acclimation and its reversal, both of which are important for estimating the responses of species to transient temper- ature changes. Here we therefore examine the effects of rate of temperature change on critical thermal maxima (CTmax) and minima (CTmin), as well as the time course of the acclimation response and its reversal in two beetle species, Tenebrio molitor and Cyrtobagous Salviniae. Increasing rates of temperature change had opposite effects on T. molitor and C. Salviniae .I nT. molitor, faster rates of change reduced both CTmax (c. 2 C) and CTmin (c. 3 C), while in C. Salviniae faster rates of change increased both CTmax (c. 6 C) and CTmin (c. 4 C). CTmax in T. molitor showed little response to acclimation, while the response to acclimation of CTmin was most pronounced following exposure to 35 C (from 25 C) and was complete within 24 h. The time course of acclimation of CTmax in C. Salviniae was 2 days when exposed to 36 C (from c. 26 C), while that of CTmin was less than 3 days when exposed to 18 C. In T. molitor, the time course of reacclimation to 25 C after treatments at 15 C and 35 C at 75% RH was longer than the time course of acclimation, and varied from 3-6 days for CTmax and 6 days for CTmin .I nC. Salviniae, little change in CTmax and CTmin (<0.5 C) took place in all treatments suggesting that reacclimation may only occur after the 7 day period used in this study. These results indicate that both T. molitor and C. Salviniae may be restricted in their ability to respond to transient temperature changes at short-time scales, and instead may have to rely on behavioral adjustments to avoid deleterious effects at high temperatures.
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the effects of acclimation and rates of temperature change on critical thermal limits in tenebrio molitor tenebrionidae and cyrtobagous Salviniae curculionidae
Journal of Insect Physiology, 2012Co-Authors: Jessica L Allen, Susana Clusellatrullas, Steven L ChownAbstract:Abstract Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing thermal environments on such survival. However, investigations of these limits may be affected by the circumstances under which trials are undertaken. Only a few studies have examined these effects, and typically not for beetles. This group has also not been considered in the context of the time courses of acclimation and its reversal, both of which are important for estimating the responses of species to transient temperature changes. Here we therefore examine the effects of rate of temperature change on critical thermal maxima (CTmax) and minima (CTmin), as well as the time course of the acclimation response and its reversal in two beetle species, Tenebrio molitor and Cyrtobagous Salviniae. Increasing rates of temperature change had opposite effects on T. molitor and C. Salviniae. In T. molitor, faster rates of change reduced both CTmax (c. 2 °C) and CTmin (c. 3 °C), while in C. Salviniae faster rates of change increased both CTmax (c. 6 °C) and CTmin (c. 4 °C). CTmax in T. molitor showed little response to acclimation, while the response to acclimation of CTmin was most pronounced following exposure to 35 °C (from 25 °C) and was complete within 24 h. The time course of acclimation of CTmax in C. Salviniae was 2 days when exposed to 36 °C (from c. 26 °C), while that of CTmin was less than 3 days when exposed to 18 °C. In T. molitor, the time course of reacclimation to 25 °C after treatments at 15 °C and 35 °C at 75% RH was longer than the time course of acclimation, and varied from 3–6 days for CTmax and 6 days for CTmin. In C. Salviniae, little change in CTmax and CTmin (
C.j. Cilliers - One of the best experts on this subject based on the ideXlab platform.
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Biological control of water fern, Salvinia molesta (Salviniaceae), in South Africa
Agriculture Ecosystems & Environment, 1991Co-Authors: C.j. CilliersAbstract:Abstract Until recently, water fern, Salvinia molesta D.S. Mitchell, in South Africa was only surpassed by water hyacinth as an aquatic weed and was particularly troublesome in regions with a subtropical climate. Following impressive successes elsewhere around the world, the weed has been successfully controlled biologically in South Africa using the weevil Cyrtobagous Salviniae Calder and Sands. In this review, the recent introduction and establishment of C. Salviniae in South Africa is described, and the future management of S. molesta is discussed.
Susana Clusellatrullas - One of the best experts on this subject based on the ideXlab platform.
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the effects of acclimation and rates of temperature change on critical thermal limits in tenebrio molitor tenebrionidae and cyrtobagous Salviniae curculionidae
Journal of Insect Physiology, 2012Co-Authors: Jessica L Allen, Susana Clusellatrullas, Steven L ChownAbstract:Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing ther- mal environments on such survival. However, investigations of these limits may be affected by the circum- stances under which trials are undertaken. Only a few studies have examined these effects, and typically not for beetles. This group has also not been considered in the context of the time courses of acclimation and its reversal, both of which are important for estimating the responses of species to transient temper- ature changes. Here we therefore examine the effects of rate of temperature change on critical thermal maxima (CTmax) and minima (CTmin), as well as the time course of the acclimation response and its reversal in two beetle species, Tenebrio molitor and Cyrtobagous Salviniae. Increasing rates of temperature change had opposite effects on T. molitor and C. Salviniae .I nT. molitor, faster rates of change reduced both CTmax (c. 2 C) and CTmin (c. 3 C), while in C. Salviniae faster rates of change increased both CTmax (c. 6 C) and CTmin (c. 4 C). CTmax in T. molitor showed little response to acclimation, while the response to acclimation of CTmin was most pronounced following exposure to 35 C (from 25 C) and was complete within 24 h. The time course of acclimation of CTmax in C. Salviniae was 2 days when exposed to 36 C (from c. 26 C), while that of CTmin was less than 3 days when exposed to 18 C. In T. molitor, the time course of reacclimation to 25 C after treatments at 15 C and 35 C at 75% RH was longer than the time course of acclimation, and varied from 3-6 days for CTmax and 6 days for CTmin .I nC. Salviniae, little change in CTmax and CTmin (<0.5 C) took place in all treatments suggesting that reacclimation may only occur after the 7 day period used in this study. These results indicate that both T. molitor and C. Salviniae may be restricted in their ability to respond to transient temperature changes at short-time scales, and instead may have to rely on behavioral adjustments to avoid deleterious effects at high temperatures.
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the effects of acclimation and rates of temperature change on critical thermal limits in tenebrio molitor tenebrionidae and cyrtobagous Salviniae curculionidae
Journal of Insect Physiology, 2012Co-Authors: Jessica L Allen, Susana Clusellatrullas, Steven L ChownAbstract:Abstract Critical thermal limits provide an indication of the range of temperatures across which organisms may survive, and the extent of the lability of these limits offers insights into the likely impacts of changing thermal environments on such survival. However, investigations of these limits may be affected by the circumstances under which trials are undertaken. Only a few studies have examined these effects, and typically not for beetles. This group has also not been considered in the context of the time courses of acclimation and its reversal, both of which are important for estimating the responses of species to transient temperature changes. Here we therefore examine the effects of rate of temperature change on critical thermal maxima (CTmax) and minima (CTmin), as well as the time course of the acclimation response and its reversal in two beetle species, Tenebrio molitor and Cyrtobagous Salviniae. Increasing rates of temperature change had opposite effects on T. molitor and C. Salviniae. In T. molitor, faster rates of change reduced both CTmax (c. 2 °C) and CTmin (c. 3 °C), while in C. Salviniae faster rates of change increased both CTmax (c. 6 °C) and CTmin (c. 4 °C). CTmax in T. molitor showed little response to acclimation, while the response to acclimation of CTmin was most pronounced following exposure to 35 °C (from 25 °C) and was complete within 24 h. The time course of acclimation of CTmax in C. Salviniae was 2 days when exposed to 36 °C (from c. 26 °C), while that of CTmin was less than 3 days when exposed to 18 °C. In T. molitor, the time course of reacclimation to 25 °C after treatments at 15 °C and 35 °C at 75% RH was longer than the time course of acclimation, and varied from 3–6 days for CTmax and 6 days for CTmin. In C. Salviniae, little change in CTmax and CTmin (
