Abstract:The aquatic fern salvinia can retain an air layer on its hairy leaf surface when submerged under water, which is an inspiration for biomimetic applications like drag reduction. In this research, an electrostatic flocking technique is used to produce a hairy surface to mimic the air-trapping performance of the salvinia leaf.Viscose and nylon flocks with different sizes were selected. A volumetric method was established to analyze the air-retaining performance of the flocking samples, Salvinia molesta and lotus … Show more
“…For further study, air volume change over time was tested under the same status with an extra air collection device (a funnel placed over the sample with its end inserted into a sealed 10-mL burette filled with 8 mL of distilled water). 35 Air bubbles escaping from the sample were collected and the volume was obtained from the scale reading of the burette.…”
Section: Methodsmentioning
confidence: 99%
“…Our research group has successfully evaluated the underwater air-retaining performance of electrostatic flocking samples by designing an installation to monitor the air volume change. 35 Herein, this approach was applied to the terry fabrics and a simple thermal insulation test was carried out as well. Figure 2.Schematic drawing of terry fabric under fluctuant water: (left) loop form when air–water interface is pulled away from surface by wave, (right) change of loop form when water is pushed to penetrate the surface.…”
The plant leaf of Salvinia molesta can retain an air layer underwater due to the hydrophobic and elastic eggbeater-shaped hairs on its surface, which have potential applications in thermal insulation devices. In this research, terry fabrics are explored to mimic the air-retaining ability of the salvinia leaf for potential application in overwater life-saving appliances. The surface structure of the fabric is analyzed and the superhydrophobicity is obtained by hydrophobic treatment combined with microscale roughness brought by the fabric texture. The air volume change and the thermal insulation tests demonstrated that terry fabrics, F1 and F3, can retain an air layer on their surfaces and hold air in between the fibers and inside the loops for a long time underwater, which would provide thermal insulation and buoyancy force—the two key features of life-saving appliances.
“…For further study, air volume change over time was tested under the same status with an extra air collection device (a funnel placed over the sample with its end inserted into a sealed 10-mL burette filled with 8 mL of distilled water). 35 Air bubbles escaping from the sample were collected and the volume was obtained from the scale reading of the burette.…”
Section: Methodsmentioning
confidence: 99%
“…Our research group has successfully evaluated the underwater air-retaining performance of electrostatic flocking samples by designing an installation to monitor the air volume change. 35 Herein, this approach was applied to the terry fabrics and a simple thermal insulation test was carried out as well. Figure 2.Schematic drawing of terry fabric under fluctuant water: (left) loop form when air–water interface is pulled away from surface by wave, (right) change of loop form when water is pushed to penetrate the surface.…”
The plant leaf of Salvinia molesta can retain an air layer underwater due to the hydrophobic and elastic eggbeater-shaped hairs on its surface, which have potential applications in thermal insulation devices. In this research, terry fabrics are explored to mimic the air-retaining ability of the salvinia leaf for potential application in overwater life-saving appliances. The surface structure of the fabric is analyzed and the superhydrophobicity is obtained by hydrophobic treatment combined with microscale roughness brought by the fabric texture. The air volume change and the thermal insulation tests demonstrated that terry fabrics, F1 and F3, can retain an air layer on their surfaces and hold air in between the fibers and inside the loops for a long time underwater, which would provide thermal insulation and buoyancy force—the two key features of life-saving appliances.
“…In 2011, lithography was first applied to fabricate simplified eggbeater structures. [ 31 ] Since then, several techniques including direct laser lithography, [ 32 ] low‐temperature chemical vapor deposition (LTCVD), [ 36 ] atmosphere pressure plasma chemical vapor deposition (APPCVD), [ 37 ] water‐assisted chemical vapor deposition (WACVD), [ 38 ] electrodeposition, [ 39 ] electrospinning, [ 40 ] electrostatic flocking, [ 41 ] 3D printing, [ 26,30 ] plasma etching, [ 42 ] and chemical etching [ 43 ] have been developed to imitate the fine structures of Salvinia leaves ( Figure ). These techniques have been used to replicate simple artificial eggbeater structures ( Table 1 ).…”
Section: Fabrication Techniquesmentioning
confidence: 99%
“…Electrospinning: Reproduced with permission. [ 41 ] Copyright 2018, Royal Society of Chemistry. Electrostatic flocking: Reproduced with permission.…”
Nature‐inspired superhydrophobic surfaces have attracted significant attention because of their remarkable properties. In particular, recent findings about the aquatic plant Salvinia provide novel approaches for the application of superhydrophobic surfaces. The unique heterogeneous eggbeater structures endow Salvinia leaves with superhydrophobicity and strong adhesion, which ensures that the leaves show durable air‐retainability in underwater environments. However, the complex eggbeater structures present a difficult manufacturing challenge. Therefore, this review first introduces the air‐retention mechanism, which may benefit the design of Salvinia‐inspired structures. Moreover, advanced techniques including photolithography, direct laser lithography, chemical vapor deposition, electrodeposition, electrostatic flocking, 3D printing, chemical etching, and plasma etching recently have been developed for fabricating Salvinia‐inspired structures. This review focuses on the advantages, disadvantages, and application prospects of such techniques. In addition, the excellent air‐retainability of Salvinia structures has inspired many engineering applications, including drag reduction; water harvesting, evaporation, and repellence; oil/water separation; and thermal insulation. This review discusses the performance and challenges of artificial structures to such applications. Finally, methods of evaluating air‐retainability are discussed. It is expected that this review will not only satisfy scientific curiosity but also contribute to the design and application of Salvinia‐inspired functional surfaces.
“…With respect to these parameters most artificial surfaces developed so far failed. [20,35,38,39] Surprisingly, the floating fern Salvinia molesta is able to maintain a permanent air layer under water during its lifetime. Therefore, the surface of Salvinia leaves is considered as a biological model for technological air-retaining surfaces.…”
The ability of floating ferns Salvinia to keep a permanent layer of air under water is of great interest, e.g., for drag‐reducing ship coatings. The air‐retaining hairs are superhydrophobic, but have hydrophilic tips at their ends, pinning the air–water interface. Here, experimental and theoretical approaches are used to examine the contribution of this pinning effect for air‐layer stability under pressure changes. By applying the capillary adhesion technique, the adhesion forces of individual hairs to the water surface is determined to be about 20 µN per hair. Using confocal microscopy and fluorescence labeling, it is found that the leaves maintain a stable air layer up to an underpressure of 65 mbar. Combining both results, overall pinning forces are obtained, which account for only about 1% of the total air‐retaining force. It is suggested that the restoring force of the entrapped air layer is responsible for the remaining 99%. This model of the entrapped air acting is verified as a pneumatic spring (“air‐spring”) by an experiment shortcircuiting the air layer, which results in immediate air loss. Thus, the plant enhances its air‐layer stability against pressure fluctuations by a factor of 100 by utilizing the entrapped air volume as an elastic spring.
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