Is the lotus leaf superhydrophobic?

Cheng, Yang‐Tse; Rodak, Daniel E.

doi:10.1063/1.1895487

Cited by 567 publications

(446 citation statements)

References 18 publications

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“…The possibilities of the Lotus leaf with its hydrophobicity is investigated in several studies [25,34,35,45], and superhydrophobicity (including ultrahydrophobicity [42]) is furthermore the topic of yet several more studies [11,27,34,36,37,39,40,42,43,44,46], where links to nanostructure of the matter and hence nanotechnology are given in various works [1,12,33,35,40,45]. The large collection of water-repellent and self-cleaning plant surfaces with corresponding contact angles by Neinhuis and Barthlott (1997) [41] should be noted.…”

Section: Pursue Superhydrophobic Surface Characteristicsmentioning

confidence: 99%

“…Illustration of how self-cleaning glass works, in three steps, from left to right: 1) activation of the coating by UV radiation and natural dirtying, 2) decomposition of the organic dirt, and 3) rain water washes away the loosened and degraded dirt. Source: Pilkington Active [6] Several investigations have been carried out on hydrophilic and hydrophobic surfaces with their respective superhydrophilic and superhydrophobic counterparts or enhancements, and on self-cleaning properties and various possible application areas in general [1,2,5,10,11,12,22,24,25,27,33,34,35,36,37,38,39,40,41,42,43,44,45,46]. It is not within the scope of this work to go into details of all these, as the focus of this work is on self-cleaning characterization methods, state-of-the-art self-cleaning glazing products of today and future research pathways for self-cleaning glazing products of tomorrow.…”

Section: Theory Behind the Self-cleaning Effect Of Glazing Productsmentioning

confidence: 99%

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Self-cleaning glazing products: A state-of-the-art review and future research pathways

Midtdal

Jelle

2013

Solar Energy Materials and Solar Cells

174

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Self-cleaning technology is used in a variety of products today, with glazing products being the foremost area of application. However, there are several self-cleaning technologies in use and their self-cleaning efficiency may be unclear. This study aims to give a comprehensive state-of-the-art review of the self-cleaning glazing products available on the market today and investigate methods for measuring the self-cleaning effect. Various future research pathways and opportunities for the self-cleaning products of tomorrow are also explored within this study, with emphasis on solar energy application areas such as daylight, solar radiation transmission, electrochromism, building integrated photovoltaics (BIPV), solar cell glazing and solar cells in general. Self-cleaning products from several manufacturers that utilize two different self-cleaning technologies of either photocatalytic hydrophilic or hydrophobic capability are presented. The photocatalytic hydrophilic products in question are self-cleaning glazing products ready-to-use when purchased, whilst the presented hydrophobic products are coatings that must be applied to existing glazing products in order to yield a water-repellent and self-cleaning surface. It is stated that the self-cleaning action of the photocatalytic hydrophilic products is evident through 25 to 30 years, even during dry spills, and that they are able to maintain a cleaner surface than ordinary untreated float glass. However, the selfcleaning action of hydrophobic-coated products is limited by a relatively short life expectancy of about 3-4 years, and their self-cleaning performance is found to be feeble compared to ordinary untreated float glass. Nonetheless, the potential for future use of both self-cleaning technologies are apparent, with focus on alternative application areas such as solar cells, BIPV and information display devices, which indeed could benefit from utilizing the selfcleaning technology. Visions for future self-cleaning products are also discussed, which combine self-cleaning abilities with photovoltaism and electrochromism, whereupon the applicability of the self-cleaning technology may be greatly increased.

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Section: Pursue Superhydrophobic Surface Characteristicsmentioning

confidence: 99%

Section: Theory Behind the Self-cleaning Effect Of Glazing Productsmentioning

confidence: 99%

Self-cleaning glazing products: A state-of-the-art review and future research pathways

Midtdal

Jelle

2013

Solar Energy Materials and Solar Cells

174

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“…Different from traditional superhydrophobic surfaces, which are characterized by the bouncing or rolling off of deposited millimeter-size large drops, [32,33] CMDSP surfaces support the self-removal capability of smallscale condensate microdrops. It has been reported that classical superhydrophobic lotus leaves (Figure 1a), [34][35][36][37] as well as artificial surfaces consisting of hierarchical micro-and nanostructures, [38] one-tier microstructures, [39][40][41][42][43] or nanostructures [44,45] with larger characteristic interspaces, present a low-adhesivity property to the deposited water macrodrops, but become highly adhesive to condensed microdrops (Figure 1b). This is because moisture easily penetrates the microscale valleys or cavities.…”

mentioning

confidence: 99%

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

2017

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interest has focused on utilizing the lowadhesivity nature of superhydrophobic surfaces for the rapid removal of condensate microdrops, as this has significance in fundamental research and technological innovation. Example applications are the enhancement of condensation heat transfer for high-efficiency thermal management and energy utilization, [20][21][22][23][24][25] energy-effective antifreezing for airconditioner heat exchangers and aircraft wings, [26][27][28] and electrostatic energy harvesting. [29] In general, condensate drops on typical flat hydrophobic surfaces are only shed off under gravity when their sizes are comparable to the capillary length (≈2.7 mm for water), [30] which creates undesirable effects such as large thermal resistance [20][21][22][23][24][25] and the freezing of subcooled drops. [26][27][28] Clearly, a great challenge is the timely removal of condensate drops at the microscale where the gravitational effect does not work. The latest research has indicated that these small-scale condensate microdrops may self-remove via mutual coalescence as long as the coalescence-released excess surface energy is larger than the interface adhesion-induced energy dissipation. [31] Much effort has been devoted to exploring the utilization of knowledge of bionic low-adhesivity superhydrophobicity to develop innovative condensate microdrop self-propelling (CMDSP) surfaces. Different from traditional superhydrophobic surfaces, which are characterized by the bouncing or rolling off of deposited millimeter-size large drops, [32,33] CMDSP surfaces support the self-removal capability of smallscale condensate microdrops. It has been reported that classical superhydrophobic lotus leaves (Figure 1a), [34][35][36][37] as well as artificial surfaces consisting of hierarchical micro-and nanostructures, [38] one-tier microstructures, [39][40][41][42][43] or nanostructures [44,45] with larger characteristic interspaces, present a low-adhesivity property to the deposited water macrodrops, but become highly adhesive to condensed microdrops (Figure 1b). This is because moisture easily penetrates the microscale valleys or cavities. Clearly, superhydrophobic surfaces with irrationally designed surface structures can enhance the solid-liquid interfacial adhesion instead of promoting the rapid removal of condensed drops. Accordingly, it is still a challenge to design and fabricate very effective low-adhesivity superhydrophobic surfaces with the self-removal ability of condensate microdrops. Recently, there has been a large breakthrough in understanding the mechanism and construction rules of bionic CMDSP surfaces, leading to the exploration of fabrication methods for the surface functionalization of widely used metal materials and the Bionic condensate microdrop self-propelling (CMDSP) surfaces are attracting increased attention as novel, low-adhesivity superhydrophobic surfaces due to their value in fundamental research and technological innovation, e.g., for enhancing heat transfer, energy-effective antifreezing, and...

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“…But, Table 1 shows that this is not the case for the CO 2 laser-induced patterned samples as θ had increased by up to 10° even though a maximum increase in Sa was determined to be around 0.5 µm when compared to the asreceived sample (AR). As hypothesized previously [29,30], this phenomenon can be explained by the existence of a mixed-state wetting regime [31][32][33][34]. That is, the liquid, when in contact with the sample surface, gave rise to a mixture of Wenzel and Cassie-Baxter regimes.…”

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confidence: 88%

Osteoblast cell response to a CO2 laser modified polymeric material

Waugh

Lawrence

Brown

2012

Optics and Lasers in Engineering

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-AbstractLasers are an efficient technology which can be applied for the surface treatment of polymeric biomaterials to enhance insufficient surface properties. That is, the surface chemistry and topography of biomaterials can be modulated to increase the biofunctionality of that material. By employing CO 2 laser patterning and whole area processing of nylon 6,6 this paper details how the surface properties were significantly modified. Samples which had undergone whole area processing followed current theory in that the advancing contact angle, θ, with water decreased and the polar component, γ p , increased upon an increase in surface roughness. For the patterned samples it was observed that θ increased and γ P decreased. This did not follow current theory and can be explained by a mixed-state wetting regime. By seeding osteoblast cells onto the samples for 24 hours and 4 days the laser surface treatment gave rise to modulated cell response. For the laser whole area processing, θ and γ P correlated with the observed cell count and cover density. Owed to the wetting regime, the patterned samples did not give rise to any correlative trend. As a result, CO 2 laser whole area processing is more likely to allow one to predict biofunctionality prior to cell seeding. What is more, for all samples, cell differentiation was evidenced. On account of this and the modulation in cell response, it has been shown that laser surface treatment lends itself to changing the biofunctional properties of nylon 6,6.Keywords: Laser surface treatment, osteoblast cells, wettability, nylon 6,6, bioactivity. -IntroductionOn account of the population living longer and biotechnology having the potential to improve quality of life there is an ever increasing interest in this field [1][2][3][4][5][6]. More times than not there usually has to be a compromise between bulk and surface properties when determining the best polymeric materials to use [7,8]. In most cases the bulk properties are seen more in favour over those surface properties required [8]. As a result of this, surface properties are not sufficient in terms of the level of bioactivity required giving rise to clinical failure of the implant [9]. Leading on from this, there is a necessity of developing a technique to change the surface properties to enhance and predict the cell response.Through prior research other methods such as plasmas [10][11][12][13], photochemical techniques [14][15][16] and coating technologies [3,[17][18][19] offer the ability to vary the physiochemical properties of the polymer surface without changing the bulk properties. These various techniques have the ability to improve cell growth and adhesion on polymeric biomaterials; however controlled, precise modification is lacking from the methods named. Laser surface treatment offers the ability to vary the physiochemical surface properties simultaneously with considerably more control and accuracy in comparison to the other possible techniques [20,21]. Furthermore, lasers offer a convenient means of modifying ...

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Is the lotus leaf superhydrophobic?

Cited by 567 publications

References 18 publications

Self-cleaning glazing products: A state-of-the-art review and future research pathways

Self-cleaning glazing products: A state-of-the-art review and future research pathways

Recent Progress in Bionic Condensate Microdrop Self‐Propelling Surfaces

Osteoblast cell response to a CO2 laser modified polymeric material

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