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![SEM images of: (a) the natural lotus leaf and (b) the superhydrophobic PDMS surface (respective insets shows the higher magnification images) and spherical water droplets on the (c) lotus leaf and (d) superhydrophobic PDMS surface. Images reprinted from [73], with permission from American Chemical Society, Copyright 2005.](publication/261516233/figure/fig7/AS:399602734911495@1472284124785/SEM-images-of-a-the-natural-lotus-leaf-and-b-the-superhydrophobic-PDMS-surface.png)
SEM images of: (a) the natural lotus leaf and (b) the superhydrophobic PDMS surface (respective insets shows the higher magnification images) and spherical water droplets on the (c) lotus leaf and (d) superhydrophobic PDMS surface. Images reprinted from [73], with permission from American Chemical Society, Copyright 2005.
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The lotus plant is recognized as a 'King plant' among all the natural water repellent plants due to its excellent non-wettability. The superhydrophobic surfaces exhibiting the famous 'Lotus Effect', along with extremely high water contact angle (>150°) and low sliding angle (<10°), have been broadly investigated and extensively applied on variety o...
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... antistick trimethylchlorosilane (TMCS) monolayer was evaporated on this negative template and again a second PDMS replication was performed on it. In this fashion, the hierarchical surface morphology of the lotus leaf was directly transferred with high precision to the PDMS surface which exhibited similar wetting behavior as the original lotus leaf (Figure 7). However the molding of fresh lotus leaves may create artifacts due to water evaporation from the structure and consequently shrinkage of papillae structures. ...
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Citations
... mimicked rice-leaf hierarchical surface structure and achieved superhydrophobic and anisotropic properties. Nonetheless, considerable attention has been focused on a limited number of nature's functional surfaces, such as lotus leaves 56,57 , butterfly wings 58 , shark skin 59 , and rose petals 60,61 , leaving many potential bio-templates unexplored. ...
Developing suitable light management layers can improve the lifetime and efficiency of solar cells and other optoelectronics. Here, a bioinspired approach to produce all-biobased films with high anisotropic light scattering and superhydrophobicity is presented as a route toward sustainable light management layers for photovoltaics. The multifunctional films are achieved by replicating leek leaves onto cellulose acetate, producing hierarchical surface structures. The free-standing films show a transmittance of ≈94% and a haze of ≈54% at the wavelength of 550 nm. Moreover, anisotropic advancing contact angles of up to 160° and 156° in cross directions are achieved through tailoring a carnauba wax coating. Using the replica as the light management layer on perovskite solar cells improved the power conversion efficiency by 6 ± 0.3%. Meanwhile, the surface water repellency facilitates self-cleaning, ensuring maximum incident light over time by tackling dirt accumulation. Furthermore, the method can be potentially employed to fabricate substrates from virtually any leaf or patterned surface as the initial replication template.
... The lotus leaf is commonly considered as an example of the relationship between hydrophobicity and surface morphology [1], sometimes without indicating that the surface of the lotus leaf (Nelumbo nucifera) is a composite of papillary epidermal cells and tubular epicuticular waxes [2,3]. Plant waxes can be seen with the naked eye on the leaves and fruits of certain plants. ...
A special technique has been developed for producing a composite aerogel which consists of graphene oxide and soy wax (GO/wax). The reduction of graphene oxide was carried out by the stepwise heating of this aerogel to 250 °C. The aerogel obtained in the process of the stepwise thermal treatment of rGO/wax was studied by IR and Raman spectroscopy, scanning electron microscopy, and thermogravimetry. The heat treatment led to an increase in the wax fraction accompanied by an increase in the contact angle of the rGO/wax aerogel surface from 136.2 °C to 142.4 °C. The SEM analysis has shown that the spatial structure of the aerogel was formed by sheets of graphene oxide, while the wax formed rather large (200–1000 nm) clumps in the folds of graphene oxide sheets and small (several nm) deposits on the flat surface of the sheets. The sorption properties of the rGO/wax aerogel were studied with respect to eight solvent, oil, and petroleum products, and it was found that dichlorobenzene (85.8 g/g) and hexane (41.9 g/g) had the maximum and minimum sorption capacities, respectively. In the case of oil and petroleum products, the indicators were in the range of 52–63 g/g. The rGO/wax aerogel was found to be highly resistant to sorption–desorption cycles. The cyclic tests also revealed a swelling effect that occurred differently for different parts of the aerogel.
... Identification of the water contact (wetting) angle is used to determine whether the surface of solid materials is hydrophilic, hydrophobic or highly hydrophobic. The surface is considered hydrophilic when the water contact angle is less than 90° (Figure 1), hydrophobic when the water contact angle is greater than 90° and highly hydrophobic when the water contact angle is greater than 150° [30]. Surfaces with water contact ranging from 10° to 90° are termed semi-hydrophilic [31,32]. ...
Ensuring the tightness of buildings using self-adhesive tapes is one of the cost-effective, efficient, and reliable solutions. There is a lack of research, standards, and methodologies for construction adhesive tape, especially for assessing the functional properties of the tape after ageing. The aim of this work is to evaluate the tightness of different building surfaces and adhesive tape systems by conducting artificial ageing. It was found that adhesive tapes with an acrylic adhesive base ensured a fully sealed system. In all cases, tapes applied to surfaces such as plywood, gypsum plasterboard, cement-bonded particle board, plastered cement-bonded particle board, and plastic board provided sufficient sealing. The air permeability of the tapes on the OSB was two to seven times higher than that of the defined sealed system with other surfaces. In most cases, air permeability increased on OSB, gypsum plasterboard, and plastered cement-bonded particle board after ageing. The least problematic surface is the plastic board. In all tested cases, adequate sealing was observed after ageing, with only three of all tested tapes not providing sufficient bonding strength.
... Research in biomimicry has shown that the microstructure of surfaces is the most important reason for the special functionality of biological surfaces in nature [1]. For example, the dense microcolumn structure and the nanoscale villi on the microcolumn make the lotus leaf surface with superhydrophobic property and self-cleaning capability [2]. Shark skin is composed of oriented diamond-shaped dermal denticles which are each covered with five conical ridges. ...
... These ions reduce the ionization energy (∆E) required for the solution to undergo ionization. According to Eqs. (2) and (3), a lower ionization energy implies a lower breakdown threshold and results in the (3), a lower ionization energy implies a lower breakdown threshold and results in the formation of a plasma with a higher electron density during the breakdown process. This dense plasma generates stronger shock waves, contributing to the enhanced performance of material removal. ...
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... All plasma treatment conditions on bacterial cellulose resulted in an increased contact angle, indicating a reduction in hydrophilic characteristics. Depending on the plasma processing conditions, some contact angle results approached 100°, indicating hydrophobic characteristics (Latthe et al. 2014). ...
Bacterial cellulose presents itself as an alternative to traditional textiles due to its versatility, aesthetics, mechanical similarity to leather and, most importantly, sustainability in production processes. However, its use depends on surface modifications that promote suitable performance in fashion products, due to its high hydrophilicity. A less polluting alternative is the plasma treatment, which does not involve effluents or solid or liquid waste. In this context, this study aims to use the cathodic cage plasma process, an environmentally friendly technique, to reduce the hydrophilic nature of bacterial cellulose for its application in the fashion industry. Samples were produced from kombucha and treated through a modified low-pressure cold plasma system, named cathodic cage plasma. The influence of the gas mixture (Ar/acetylene and Ar/acetylene/H2), treatment time and duty cycle was evaluated. The samples were characterized through wetting behavior (contact angle), FTIR, TG and dTG, XPS and FEG-SEM. The cultivated bacterial cellulose exhibited apparent flexibility, roughness, and some transparency. The plasma treatment was proven effective, forming a thin hydrocarbon film on the surface of the BC, sufficient to decrease the hydrophilicity and purify it without degradation. The bacterial cellulose could be made hydrophobic by using parameters such as a longer treatment time, a combination of gases without the addition of hydrogen, and a lower duty cycle (from the most to the least influential factor, respectively). Plasma treatment mitigated the common issues of hydrophilic bacterial cellulose without the need to introduce processes that generate effluents or waste while maintaining the material’s biodegradability.
... Hydrophobic behavior can be seen in nature with the example of a lotus leaf. Since the study by Neinhuis and Barthlott, the lotus leaf has been studied by many scientists due to a CA greater than 160° and a sliding angle (SA), the angle at which water slides off the surface with respect to the horizontal, of less than 5° [6][7] . Even more, on the lotus leaf surface, the adhesion between the surface and dust particles is much smaller than the adhesion between water droplets and dust particles [7] . ...
... Since the study by Neinhuis and Barthlott, the lotus leaf has been studied by many scientists due to a CA greater than 160° and a sliding angle (SA), the angle at which water slides off the surface with respect to the horizontal, of less than 5° [6][7] . Even more, on the lotus leaf surface, the adhesion between the surface and dust particles is much smaller than the adhesion between water droplets and dust particles [7] . Conversely, in hydrophilic coatings water exhibits a lower CA (<90°), adheres more to the surface, and dissolves and washes away the contaminants. ...
... The surface of these leaves exhibits micro-scale roughness, leading to water CAs up to 170 • . This is attributed to the presence of air trapped between the droplets and the wax crystals on the plant's surface, effectively minimizing the contact area [13]. ...
... The increase in the contact angle can be attributed to an enhanced surface roughness and the presence of hierarchical spiky protrusions. Lotus leaves exhibit excellent superhydrophobic surface properties owing to their microstructures and hierarchical structural arrangements [13]. In the case of the PP superhydrophobic surface, the hierarchical protrusions were created via microstretching at the interphase of the polymer and solvent-leaving regions. ...
... Thus, the exposed outer surface is converted into a superhydrophobic surface, as shown in Fig. 1f. These protrusions facilitate the adoption of the Cassie-Baxter phenomenon with the added backing of air pockets between the polymer and water droplet interphases, through which the surface repels water (similar to a lotus flower surface) and avoids any surface retention [13]. ...
The global pollution crisis arising from the accumulation of plastic in landfills and the environment necessitates addressing plastic waste issues. Notably, polypropylene (PP) waste accounts for 20% of total plastic waste and holds promise for hydrophobic applications in the realm of recycling. Herein, the transparent and non-transparent superhydrophobic films made from waste PP are reported. A hierarchical structure with protrusions is induced through spin-casting and thermally induced phase separation. The films had a water contact angle of 159° and could vary in thickness, strength, roughness, and hydrophobicity depending on end-user requirements. The Bode plot indicated enhanced corrosion resistance in the superhydrophobic films. Antibacterial trials with Escherichia coli and Staphylococcus aureus microbial solutions showed that the superhydrophobic film had a significantly lower rate of colony-forming units compared to both the transparent surface and the control blank sample. Moreover, a life cycle assessment revealed that the film production resulted in a 62% lower embodied energy and 34% lower carbon footprint compared to virgin PP pellets sourced from petroleum. These films exhibit distinctiveness with their dual functionality as coatings and freestanding films. Unlike conventional coatings that require chemical application onto the substrate, these films can be mechanically applied using adhesive tapes on a variety of surfaces. Overall, the effective recycling of waste PP into versatile superhydrophobic films not only reduces environmental impact but also paves the way for a more sustainable and eco-friendly future.
... An example of how nature takes advantage of hydrophobic behavior is seen in the lotus leaf. Since the study by Neinhuis and Barthlott, the lotus leaf has been studied by many scientists due to a contact angle greater than 160° and a sliding angle less than 5° [5][6]. The adhesion between the surface and dust particles is much smaller on the lotus leaf surface than the adhesion between water droplets and dust particles [6]. ...
... Since the study by Neinhuis and Barthlott, the lotus leaf has been studied by many scientists due to a contact angle greater than 160° and a sliding angle less than 5° [5][6]. The adhesion between the surface and dust particles is much smaller on the lotus leaf surface than the adhesion between water droplets and dust particles [6]. By this hydrophobic principle, the lotus leaf has a self-cleaning effect which, when implemented on metal surfaces, could further reduce corrosion and degradation of the metal. ...
Aluminum and especially titanium alloy are increasingly being used to replace traditional metals in many new applications due to their high strength-to-weight ratio and biocompatibility. Surgical implants need to have a hydrophilic nature when tissue growth is desired, while they need to be hydrophobic if tissue/microbial growth is not expected. Thus, there is a need to control the wettability of these metals. This study used a sodium chlorate electrolyte to control the wettability of 1-inch by 3-inch aluminum and titanium alloy samples using an electrochemical surface modification (ECSM) process. Duty cycle, frequency, and ECSM duration were modified while voltage was held constant at 10 V. Duty cycles of 25%, 50%, 75%, and 100% (or direct current) and frequencies of 1 kHz and 100 kHz were used. The time of processing was changed to allow the samples to have an equal active time with 2000, 1000, 667, and 500 seconds for 25%, 50%, 75%, and 100% duty cycles, respectively. A first principles-based theoretical model was developed in this study to predict the pulse power setting needed to achieve the desired wettability in the samples by measuring the sample mass before and after ECSM. The model was validated with experimental results. The surface’s wettability switched from superhydrophilic to hydrophilic after the sample was heated in a furnace. Both the metals showed a change in contact angle behavior after evaporation of the residual water. This study allows for the use of ECSM as a technique to modify the surface of implants with controlled wettability for improved osseointegration.
... The coating treatment on paper-based materials provides hydrophobic or superhydrophobic surfaces with excellent properties, such as being easy to clean, less dirty, and water-resistant (Li et al., 2021a). In addition to having a very low sliding angle (10 • ) and a very high water contact angle (>150 • ), superhydrophobic surfaces also display the well-known "Lotus Effect" (Latthe et al., 2014). Its standout features are the superhydrophobic surface's resistance to water and capacity for self-cleaning (Lee and Michielsen, 2006). ...
... These surfaces are not homogeneous as they contain lipids (hydrophobic) and polysaccharides (hydrophilic) rich areas and these variations in surface chemistry (inhomogeneities) are responsible for the effective interaction with water droplets [10,11]. As a result, rose petals can exhibit large WCA (>130 • ), but water droplets pin strongly onto the surface and cannot be removed even at high tilting angles (HA > 50 • ) [10,12]. To reach superhydrophobicity, the surface topography, i.e., the surface roughness, seems to be the most dominant characteristic. ...
