ArticlePDF Available


The water-repellent surface of lotus (Nelumbo nucifera) leaf and flower is due to nanosized wax papillae on the upper side of each epidermal cell. As a result, raindrops make a high contact angle with the papillae and roll off carrying dust and dirt particles, leaving the surface clean. This self-cleaning property of highly hydrophobic surfaces, termed as the lotus effect, has opened the possibilities of fabricating superhydrophobic surfaces for a variety of products.
RESONANCE December 2008
The water-repellent surface of lotus (Nelumbo nucifera) leaf
and flower is due to nanosized wax papillae on the upper side
of each epidermal cell. As a result, raindrops make a high
contact angle with the papillae and roll off carrying dust and
dirt particles, leaving the surface clean. This self-cleaning
property of highly hydrophobic surfaces, termed as the lotus
effect, has opened the possibilities of fabricating
superhydrophobic surfaces for a variety of products.
Lotus, botanically named Nelumbo nucifera, is regarded as a
sacred plant in Hindu mythology. Lotus is also India’s national
flower (Figure 1) and is regarded as a symbol of purity. Its leaf
and flower are water-repellant. A falling raindrop turns into a
water bead and rolls off, taking along with it the dust and the dirt
particle. Hence, despite growing in muddy waters, the lotus leaf
surface stays relatively clean (Figure 2).
Although the water repellency of lotus had long been recognized,
its scientific basis was understood only in 1997 [1] when two
botanists, Wilhelm Barthlott (Figure 3) and Christoph Neinhuis,
at the University of Bonn in Germany examined leaf surfaces of
lotus and several other plants using a scanning electron micro-
scope which resolves structures as small as 1–20 nm (one nm =
billionth or 10
of a meter). They established that the self-
cleaning property is due to the presence of convex papillae on the
surface of leaves, coated with wax crystals of nanoscopic dimen-
sion: ~10 to ~100 nm (Figure 4). The papilla greatly reduces the
contact area of water droplets with it. The water droplet, as for
example due to rain or fog or dew, is dislodged, often coalescing
into a bigger drop at the center of leaf surface that falls off with
swaying of the leaf.
Wax is comprised of a mixture of long-chain hydrocarbons:
B Karthick is a research
scholar in the Centre for
Ecological Sciences, Indian
Institute of Science,
Bangalore. His research
interests are in taxonomy
and ecology of diatoms and
ecology of wetlands.
Ramesh Maheshwari is a
former professor in
biochemistry at the Indian
Institute of Science.
Lotus, self-cleaning, hydropho-
bicity, nanotechnology.
Lotus-Inspired Nanotechnology Applications
B Karthick and Ramesh Maheshwari
Figure 1. Lotus,the national
flower of India featured on
a postage stamp issued on
September 1, 1977.
1142 RESONANCE December 2008
primary and secondary alcohols, aldehydes and triterpenes. Since
the phenomenon of water repellency and self-cleaning is best
studied in the lotus, it has come to be known as the ‘Lotus effect’.
Barthlott andhis associates examined over 13,000 plants. Barthlott
is quoted as advising, Do trust your own eyes and not the
textbooks, and if your observation is repeatedly confirmed, pub-
lish it. But take a deep breath – expect rejections of your manu-
script” [2].
A great diversity of structures has been observed on surfaces of
the above-ground parts of the plants. Although the presently used
system of plant classification relies on the sexual (floral) charac-
teristics devised by the great Swedish botanist, Carl von Linnaeus
(1707–1778), it is thought that once a uniform terminology of
describing these structures is evolved, it is thought that micro-
morphologies of plant surfaces can be used as an aid in plant
taxonomy. Here we note that the world is celebrating the
tricentenary of the birth of Linnaeus who proposed the
binomial system of nomenclature and classification of
life forms.
Incidence of Water-Repellent Plant Surfaces
Interestingly, a majority of plants in the wetlands have
water-repellent leaves. If this were not so, wetting
would interfere with gas exchange through the stomata
located on the upper (exposed) side of the floating
Figure 2. Floating lotus leaves and a blooming flower in a pond
(Left); Water drops forming beads on the leaf surface (Right). Photo
courtesy: K V Gururaja and M Boominathan.
Figure 3. ProfessorWilhelm
Barthlott, Director of Bo-
tanical Garden of the Uni-
versity of Bonn, discovered
the lotus effect and con-
ceived the fabrication of
surfaces with nanoscopic
bumps to make them self-
cleaning and patented Lo-
tus Effect in 1980.
Photo courtesy: Kerstin Koch.
Figure 4. Scanning elec-
tron microscope image of
leaf surface of Nelumbo
Photo courtesy: Prof. Wilhelm
RESONANCE December 2008
leaves. Another advantage of a water-repellant surface could be
in reducing the risk of infection. Since spores of several patho-
genic fungi require free water and air for germination, the evolu-
tion of a water-repellent surface by superimposing wax mol-
ecules on cuticle (the outermost covering) probably evolved to
reduce the risk of infection by pathogenic bacteria and fungi.
Water-repellency is not restricted to plants alone. It is manifested
also by insects with large wings (such as butterflies and dragon-
flies) which cannot clean their flying structures by legs. In this
case lotus effect works not only for the removal of particles, but
also for maintenance of flight capability of insects, which other-
wise is lost due to an unequal load on the wings.
Water-Repellant Nanostructures on Leaf Replica
Lotus effect can be reproduced on artificially made
superhydrophobic films. In one of the procedures, a rough surface
was etched into polydimethylsiloxane (PDMS). Using the lotus
leaf, a negative PDMS template was made and the negative
template then used to make a positive PDMS reproduced as a
replica sheet of the original lotus leaf. The positive PDMS
template had the same surface structures and extreme water
repellency (superhydrophobic) as the lotus leaf. A plant epider-
mal cell extrudes wax molecules which self-assemble and crys-
tallize as nanosized pillars. Thus, the hydrophobic cuticle has a
double structure: the cuticle (a polyester called cutin), and crys-
talline wax on the cuticle. On a water-repellant leaf cuticle, the
dirt particles, like a ‘fakir lying on a carpet of nails’ make only a
minuscule contact with the top of the bumps present on the plant
surface. A rolling water drop on contaminated surfaces easily
picks up the dirt particle.
Physical Basis
Four classes of surface wettability are recognized (Figure 5):
namely, superhydrophobic, hydrophobic, hydrophilic and
superhydrophilic. Lotus leaf and petal surface exhibits
superhydrophobicity, i.e., the contact angle (Figure 6) is high –
a prerequisite for
self-cleaning, is
characterized by very
high contact angles
of nanostructured
The discovery of
Lotus effect is a ‘by
product’ of research
on diversity of
morphology and
wetting of plant
1144 RESONANCE December 2008
Figure 5. The four classes
of surface wettability types
of leaf surface based on
their interaction with aque-
ous droplets.
Redrawn from Koch et al, 2008.
Figure 6. Physics of self-
cleaning property of lotus.
The large contact angle re-
sults from nanoscopic
bumps that trapairbetween
the water and the surface
minimizing the contactwith
the surface. A drop of water
rolls downwards on leaf
surface, picking up dirt
(Based on Forbes 2008).
exceeding 150 degrees. The drop, instead of sliding and spread-
ing the dirt particles which have fallen on the cuticle, rolls off
taking with it dirt (Figure 6). Lotus effect is inspiring material
scientists into sculpturing superhydrophobic surfaces that will
mimic this effect, minimizing labour and expense involved in
frequent painting of facade, particularly in the high-rise build-
Left: On smooth surface the dirt particles are redistributed
Right: On rough surface water droplet rolls off taking dirt
RESONANCE December 2008
Fabrication of Hydrophobic Surfaces
Optimizing water repellency requires consideration of the geom-
etry of pillars (size, height) and spacing. Rough, nanoscopic
finish can be exploited for several applications. Among the
numerous applications of lotus effect are, non-wettable rain wear
and sails for boats, paints for kitchen roofs and walls that make
them soot-free, windows in high-rise buildings and glass for
greenhouses avoiding their expensive and cumbersome cleaning,
water repellant fibers for garments etc. Other applications can be
in sanitary products in bathrooms and toilets and motor vehicle
windshields for reducing sticking of dirt matter and easier clean-
We are thankful to Kerstin Koch, K V Gururaja and M
Boominathan for allowing us to use their photographs.
Suggested Reading
[1] W Barthlott, C Neinhuis, Purity of the sacred lotus, or escape from
contamination in biological surfaces, Planta, Vol.202, pp.1–8, 1997.
[2] P Forbes, Self-cleaning materials, Sci. Amer., August 2008.
[3] Y T Cheng, D E Rodak, C A Wong and C A Hayden, Effects of micro-
and nano-structures on the self-cleaning behaviour of lotus leaves,
Nanotechnology, Vol.17, pp.1359–1362, 2006.
[4] K Koch, B Bhushan and W Barthlott, Diversity of structure, morphol-
ogy and wetting of plant surfaces, Soft Matter, Vol.4, pp.1943–1963,
Lotus effect is
caused by
combination of
waxiness of leaf
surface and the
nanoscopic bumps
that cover it.
Address for Correspondence
B Karthick
Centre for Ecological Sciences
Indian Institute of Science
Bangalore 560 012, India.
Email: *
Ramesh Maheshwari
Email: ramesh.maheshwari01
... Lotus-leaf-inspired biomimetic coatings can be used for a myriad of civil structures including but not limited to buildings, bridges, pavements, and sewers [26,78]. They can be applied on the exterior walls or facades, roofs, and floors of buildings to minimize the dampness due to water absorption [26,65,78]. ...
... Lotus-leaf-inspired biomimetic coatings can be used for a myriad of civil structures including but not limited to buildings, bridges, pavements, and sewers [26,78]. They can be applied on the exterior walls or facades, roofs, and floors of buildings to minimize the dampness due to water absorption [26,65,78]. Lotus-leaf biomimetic coatings will provide dust-free, self-cleaned, dry surfaces in the cases of walls or facades. ...
... Water-repellent lotus-leaf biomimetic coatings can be used to enhance the performance of drainage structures. They can be applied on the inner surface of storm and sanitary sewers to increase the flowrate of stormwater and wastewater, respectively by decreasing the surface friction [26,78]. In addition, this type of coatings can be considered for use in culverts to enhance the flowrate of overland water for faster drainage; they can also be applied on tunnel lining to keep the tunnel structures dry and to inhibit the growth of mold and mildew in tunnels [26]. ...
Full-text available
A universal infrastructural issue is wetting of surfaces; millions of dollars are invested annually for rehabilitation and maintenance of infrastructures including roadways and buildings to fix the damages caused by moisture and frost. The biomimicry of the lotus leaf can provide superhydrophobic surfaces that can repel water droplets, thus reducing the penetration of moisture, which is linked with many deterioration mechanisms in infrastructures, such as steel corrosion, sulfate attack, alkali-aggregate reactions, and freezing and thawing. In cold-region countries, the extent of frost damage due to freezing of moisture in many components of infrastructures will be decreased significantly if water penetration can be minimized. Consequently, it will greatly reduce the maintenance and rehabilitation costs of infrastructures. The present study was conducted to explore any attempted biomimicry of the lotus leaf to produce biomimetic coatings. It focuses anti-wetting characteristics (e.g., superhydrophobicity, sliding angle, contact angle), self-cleaning, durability, and some special properties (e.g., light absorbance and transmission, anti-icing capacity, anti-fouling ability) of lotus-leaf-inspired biomimetic coating products. This study also highlights the potential applications of such coating products, particularly in infrastructures. The most abundant research across coating materials showed superhydrophobicity as being well-tested while self-cleaning and durability remain among the properties that require further research with existing promise. In addition, the special properties of many coating materials should be validated before practical applications.
... Nature offers numerous sources of inspiration which can be employed effectively for sustainable future advancement. For instance, fast-swimming sharks have special micro-grooves in their skin to aid reduction in friction [25]; the surface of a lotus leaf exhibits a water-repellent effect [26]; gecko feet have a smart-adhesion function that allows them to climb even the smoothest surfaces [27]. It is well acknowledged that friction is reduced with surface smoothness, but an investigation in 1982 revealed that shark skin has a micro-groove structure that can significantly minimize friction in some turbulent situations [28]. ...
Full-text available
Energy losses due to various tribological phenomena pose a significant challenge to sustainable development. These energy losses also contribute toward increased emissions of greenhouse gases. Various attempts have been made to reduce energy consumption through the use of various surface engineering solutions. The bioinspired surfaces can provide a sustainable solution to address these tribological challenges by minimizing friction and wear. The current study majorly focuses on the recent advancements in the tribological behavior of bioinspired surfaces and bio-inspired materials. The miniaturization of technological devices has increased the need to understand micro-and nano-scale tribological behavior, which could significantly reduce energy wastage and material degradation. Integrating advanced research methods is crucial in developing new aspects of structures and characteristics of biological materials. Depending upon the interaction of the species with the surrounding, the present study is divided into segments depicting the tribological behavior of the biological surfaces inspired by animals and plants. The mimicking of bio-inspired surfaces resulted in significant noise, friction, and drag reduction, promoting the development of anti-wear and anti-adhesion surfaces. Along with the reduction in friction through the bioinspired surface, a few studies providing evidence for the enhancement in the frictional properties were also depicted.
... The hydrophobic surface is a layer that has self-cleaning properties, this property is the same as that of lotus plants and banana leaves. . Such properties occur because the lotus/banana leaf has a waxy layer that resembles oil on its surface, and the wax layer has a contact angle greater than 90° and a rough and jagged morphological surface [1] while a surface that has a contact angle of >150° is called superhydrophobic [2] [3]. The hydrophobicity of a surface can be determined by measuring contact angle formed between the water and sample surface [4] There have been many researches on the synthesis of hydrophobic coatings, but in use, these coatings are still easily damaged due to contact with other objects and easy to corrode. ...
Full-text available
The manufacture of hydrophobic coatings that have self-cleaning properties has become a research trend now, but when applied, the coating is still easily damaged due to contact with other objects and is not durable due to corrosion. This problem will certainly hinder the application of hydrophobic surfaces in industry. For this reason, the researchers mixed substrates that had anti-corrosion properties such as silica and hard and strong properties such as manganese to be able to solve the previous problem, and the method used is spin coating. The precursors were made by adding 0.5 grams of polystyrene, 0.2 grams of silica nanoparticles and 0.2 grams of manganese nanoparticles. The coating was done by using the spin coating method and the calcination temperature was 60°C using an oven for 1 hour. The research results indicate that during immersion in an acid solution (pH 6), a salt solution (pH 7) and an alkaline solution (pH 11) as well as before immersion, there is a decrease in crystal size. For the best contact angle results obtained after immersion in acid is 97.28° with salt and base is 91.65° and 95.21° and before immersion is 104.70°.
Surface-mediated transmission of pathogens is a major concern with regard to the spread of infectious diseases. Current pathogen prevention methods on surfaces rely on the use of biocides, which aggravate the emergence of antimicrobial resistance and pose harmful health effects. In response, a bifunctional and substrate-independent spray coating is presented herein. The bifunctional coating relies on wrinkled polydimethylsiloxane microparticles, decorated with biocidal gold nanoparticles to induce a "repel and kill" effect against pathogens. Pathogen repellency is provided by the structural hierarchy of the microparticles and their surface chemistry, whereas the kill mechanism is achieved using functionalized gold nanoparticles embedded on the microparticles. Bacterial tests with methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa reveal a 99.9% reduction in bacterial load on spray-coated surfaces, while antiviral tests with Phi6─a bacterial virus often used as a surrogate to SARS-CoV-2─demonstrate a 98% reduction in virus load on coated surfaces. The newly developed spray coating is versatile, easily applicable to various surfaces, and effective against various pathogens, making it suitable for reducing surface contamination in frequently touched, heavy traffic, and high-risk surfaces.
Full-text available
Oxidative stress can be explained as the deterioration of the balance between the peroxidation in the lipid layer of the cells as a result of the production of free radicals and the antioxidant defense system of the body (Cochranc, 1991), that is, oxidative stress occurs when the balance between oxidant and antioxidant systems cannot be achieved(Patlevič et al., 2016). Impaired cellular metabolism, molecular breakdown and tissue damage, which are disrupted as a result of oxidative stress to which the organism is exposed when oxidants are increased or antioxidants are insufficient (Bullock et al., 1954). One of the two main sources of oxidant substances are reactive oxygen products, the most important of which are hydroxyl radical (•OH), superoxide anion (O2•−), hydroperoxyl radical (HO2•), single oxygen (1O2) and hydrogen peroxide (H2O2) (Patlevič et al., 2016) (Figure 1).Free radicals and reactive oxygen species (ROT) cause oxidative damage to lipid, carbohydrate, protein and nucleic acids (Yoshikawa and Naito, 2002).
Die Übertragung von Prinzipien aus der Natur half dem Menschen in der Vergangenheit bei bahnbrechenden technischen und medizinischen Neuerungen, die nun unseren Alltag erleichtern. Eine genaue Studie der Vorgänge der Biomineralisation, wie sie in unser aller Knochen ablaufen, kann verschiedene Anwendungen enorm bereichern. Das Verständnis der zu Grunde liegenden Prozesse, wie die Interaktion von Zellen mit dem umliegenden mineralisierten Gewebe, die Steuerung der Kristallkeim- und Strukturbildung durch Proteintemplate oder der osmotischen Balance während der Mineralabscheidung aus übersättigter Lösung spielen dabei auch in ihrer Interaktion untereinander eine wichtige Rolle. Der Brückenschlag zwischen dem natürlichen Vorbild und der späteren Applikation findet dabei insbesondere bei biomedizinischen Anwendungen statt: Im biomedizinischen Anwendungsbereich gelten derzeit nach wie vor Implantation oder Transplantation als Goldstandardlösungen für den Ersatz von mineralisierten Geweben. Dabei stellen sich vermehrt Probleme wie die Knappheit an Spenderorganen, eine nachteilige Interaktion von Implantaten mit dem umliegenden Ersatzgewebe oder die Übertragung von Krankheiten aus tierischen Produkten dar. Um diese Hindernisse zu überwinden, können artifizielle Gewebe, die einer Biomineralisation des Materials unterliegen, geeignete Lösungen im Sinne des Tissue Engineering darstellen. In diesem Fabrikationsansatz werden personalisierte Ersatzgerüste erstellt und in den Patienten eingebracht. In technischen Anwendungen ist in Zeiten der Energiewende die möglichst effiziente Nutzung und klimafreundliche Erzeugung von Energie ein wichtiges Argument. Um die erneuerbare Energieerzeugung zu unterstützen und effizienter zu gestalten, kommen häufig keramische Katalysatoren zum Einsatz. So kann im Zuge der Wasserstoffwirtschaft die katalytische Spaltung von Wasser als Grundlage für die Gewinnung des Energieträgers Wasserstoff dienen. In ausgefeilten Mineralisationsprozessen können gerichtet Materialien entstehen, die diese Reaktion katalysieren und großtechnisch umsetzbar machen. Um diese unterschiedlichen Ziele miteinander zu verbinden und basierend auf einer gemeinsamen Grundlage individuell zu lösen, wurden in der vorliegenden Dissertation nach dem Vorbild der natürlich ablaufenden Biomineralisation Lösungsansätze erstellt. Als gemeinsame Ausgangsmaterialien wurden dafür rekombinante Spinnenseidenproteine gewählt. Basierend auf funktionellen Peptidmotiven der repetitiven Kerndomäne des Abseilfadens der Gartenkreuzspinne Araneus diadematus lag bereits das rekombinante Spinnenseidenprotein eADF4(C16) vor, das biotechnologisch großtechnisch hergestellt werden kann. Es ermöglicht neben einer molekularbiologischen Modifikation des Ausgangsmaterials ein Maßschneidern von Morphologien für unterschiedliche Anwendungen. Anhand diesen flexiblen Materials als Grundlage wurden verschiedene Fragestellungen zum Themenkomplex Biomineralisation beleuchtet, im Speziellen darunter Ersatzmaterialien für den Sehnen-Knochen-Übergang, der Enthese. Der erste Teil dieser Arbeit fokussierte sich auf das Verständnis mechanistischer Vorgänge während der bioinspirierten Mineralisation von Mangancarbonat unter kontrollierten Bedingungen in Gegenwart von verschiedenen Additiven. Darüber hinaus wurde der Ladungseinfluss von zwei Spinnenseidenvarianten untersucht, die mit unterschiedlichen Peptid-Funktionalisierungen ausgestattet waren und als klassisches Proteintemplat fungierten. Weiterhin wurde die ebenfalls geladene, synthetische Polyacrylsäure in die Reaktion als Struktur-dirigierendes Polymer eingebracht. Dabei wurde herausgefunden, dass neben einem Ladungseinfluss der Komponenten auch die kolloidale Stabilität der eingebrachten Spinnenseidenpartikel das Mineralisationsergebnis beeinflusst. Eine Abweichung der gebildeten Spezies äußerte sich in unterschiedlich starker Interaktion der Spinnenseidenpartikel mit den unter diesen Bedingungen typischerweise gebildeten Mangancarbonat-Würfeln. Außerdem konnte eine Polymer-induzierte Flüssigphase ähnlich bereits beschriebener Strukturen in Gegenwart von Polyacrylsäure generiert werden. Somit konnten aus diesen Erkenntnissen Aussagen über das Mineralisationsgeschehen mit Spinnenseidenproteinen getroffen werden und eine Einschätzung der gebildeten Materialien für eine Anwendung als Katalysatormaterial abgeleitet werden. Im zweiten Teil wurden Antworten zu Fragestellungen zu mineralisiertem Gewebeersatz erarbeitet. Da Spinnenseide ein biokompatibles Biomaterial darstellt, das nicht-toxisch und bioabbaubar ist und keine Immunreaktion auslöst, eignet es sich für derartige biomedizinische Anwendungen. Im Falle des teilmineralisierten Gewebes des Sehnen-Knochen-Übergangs sind neben einer graduellen Mineralisation hin zur Knochenseite weitere Designkriterien wichtig, die die Mechanik des Gewebes zur Kraftübertragung und Zellbesiedlung betreffen. Es wurde eine biomimetische Biomineralisation von rekombinanten Spinnenseidenvarianten untersucht, die Mineralisierungs- und Kollagenbindemotive aus der Mineralisation im Knochen zu Grunde liegenden SIBLING Proteinen trugen. Eine Materialstudie zeigte das Mineralisationsverhalten der Varianten und ihre Zellverträglichkeit. Durch eine Prozessierung in ein Gradientenmaterial wurde das unterschiedliche Zellverhalten von Osteoblasten mit einer Präferenz zu Gunsten des Kollagenbindemotivs sichtbar. Dies bestätigte eine Eignung für Materialanwendungen im graduellen Sehnenersatz an der Knochenseite. Ein weiterer Ansatz realisierte Spinnenseiden-Kompositmaterialien mit anorganischen Füllstoffen. Vorteil dieser Herangehensweise war das gerichtete Einbringen von Keramiken in ein Matrixmaterial, das dann zusätzlich mit Zellen angereichert wurde. Die Entwicklung eines neuartigen Verfahrens im 3D Druck erlaubte das einfache Verarbeiten dieser Biotinten in Gradientenmaterialien. Somit wurde erfolgreich nach Vorbild der Enthese ein rekombinantes Spinnenseidenhydrogel mit einem Gradienten, beladen an Zellen und Fluorapatit-Partikeln, gedruckt und eine Zellviabilität nach dem Prozess bestätigt. In einem dritten Teil wurde ein neuer Fabrikationsansatz für Spinnenseidengele entwickelt. Faltung und Selbstassemblierung von rekombinanten Spinnenseidenproteinen basierten in mischbaren, wässrig-organischen Zwischenphasen auf der Ausbildung von Wasserstoffbrücken und hydrophoben Effekten. Neben zu Grunde liegenden mechanistischen Betrachtungen wurde eine höhere Materialsteifigkeit der Spinnenseidengele in wässrig-organischen Mischphasen mit Dimethylsulfoxid erzielt. Sie eignen sich durch ihren organischen Lösungsmittelanteil als injizierbare oder druckbare Depots zur Formulierung von wasserunlöslichen Wirkstoffen.
Ethylene-vinyl alcohol samples containing 27 and 38 % ethylene were used to prepare blends containing 30 and 50 % thermoplastic starch (TPS) plasticized with glycerol. Their biodegradability and cytotoxicity were studied by different techniques (XRD, DSC, TGA, CA, ATR-FTIR, SEM). TPS presence significantly affected copolymer behavior, as confirmed by the appearance of OH IR 1000–1170 cm⁻¹ bands and overall reduction of EVOH crystallinity, melting point, thermal stability and hydrophobicity. Biodegradation was more efficient in the presence of TPS and resulted in the formation of a robust biofilm by a consortium of three bacteria. A lower ethylene content facilitated biodegradation, making the material easier to metabolize. The mineralization percentages obtained after a 40-day bioassay at 45 °C were up to 66 % (EVOH-27/TPS 50:50). In vitro cytotoxicity assay demonstrated no cytotoxicity before and after biodegradation. EVOH/TPS blends are presented as a potential environmentally friendly alternative to pure synthetic polymers.
Full-text available
Currently a lot of research has been done on hydrophobic layers, but in its application the layer is easily damaged and is not corrosion resistant. Therefore, this research intends to decide the effect of variations in sintering temperature on the hydrophobic characteristic of SiMn/PS nanocomposite layers using a sintering temperature of 60°C, 100°C, 140°C, 180°C and 200°C for 1 hour using a furnace.. This research uses HEM-3D (High Energy Milling Ellipse-3D Mention), XRD (X-Ray Difraction) and SEM (Scanning Electron Microscope) tools. The precursor was made by giving 0.5 grams of polystyrene, 0.2 grams of silica powder and 0.2 grams of manganese powder. Coating is done by spin coating method. The results of this research from the variation of the sintering temperature showed that the SiMn/PS nanocomposite layer was hydrophobic based on the contact angle test. The highest contact angle is at a temperature of 60°C.
Full-text available
Herein, we report cellulose-based threads from Indian sacred Lotus (Nelumbo nucifera) of the Nymphaceae family embellished with MoS 2 nanosheets for its enhanced hydrophobic and antimicrobial properties. MoS 2 nanosheets synthesized by a coprecipitation method using sodium molybdate dihydrate (Na 2 MoO 4 ·2H 2 O) and thioacetamide (CH 3 CSNH 2) were used as a sourse for MoS 2 particle growth with cellulose threads extracted from lotus peduncles. The size, crystallinity, and morphology of pure and MoS 2-coated fibers were studied using X-ray diffractometry (XRD) and scanning electron microscopy (SEM). the XRD pattern of pure lotus threads showed a semicrystalline nature, and the threads@MoS 2 composite showed more crystallinity than the pure threads. SEM depicts that pure lotus threads possess a smooth surface, and the MoS 2 nanosheets growth can be easily identified on the threads@MoS 2. Further, the presence of MoS 2 nanosheets on threads was confirmed with EDX elemental analysis. Antimicrobial studies with Escherichia coli and Candida albicans reveal that threads@MoS 2 have better resistance than its counterpart, i.e., pure threads. MoS 2 sheets play a predominant role in restricting the wicking capability of the pure threads due to their enhanced hydrophobic property. The water absorbency assay denotes the absorption rate of threads@MoS 2 to 80%, and threads@MoS 2 shows no penetration for the observed 60 min, thus confirming its wicking restriction. The contact angle for threads@MoS 2 is 128°, indicating its improved hydrophobicity.
A low-temperature deposition of zinc oxide (ZnO) nanorod has been reported on commercially available cotton fabrics. Field emission scanning electron microscope was used to investigate the morphological evolution of the ZnO with deposition time. X-ray diffraction confirms the crystallinity of the sample. Fourier transformed infrared spectroscopic study analysed the different bonding present. The as-synthesized samples showed good hydrophobic properties which got significantly worse for the sample synthesized for the highest time duration. The surface energies of the samples have been calculated using conventional Young’s equation. The sample was further modified by simple stearic acid treatment. Also, it is seen that the samples, thus prepared partially to allow oil over water to pass, thus become a material of potential regarding oil–water separation. Detail theoretical calculation has been done in order to find the surface energy and its effect on the observed hydrophobicity.
This review paper presents the diversity of plant surface structures from a single cell to multi-cellular surface sculptures. There is still no comprehensive book which provides an overview of the diversity of plant surface structures. This article presents a guide for the description of cellular and sub-cellular plant surface structures, which include hairs, wax crystals and surface folding. Biological surfaces are multifunctional boundary layers to their environment. Functionally optimized surfaces are one of the key innovations in the more than 400 million years of evolution of land plants. In the plant surface, micro- and nanostructures play a special role, and a large diversity of surface structures exists at different size levels. Well known functional aspects of plant surface structures are the reduction of particle adhesion, the sliding structures of carnivorous plants for insect catching, and the self-cleaning properties of the superhydrophobic Lotus (Nelumbo nucifera) leaves. Their structures and functions might be useful models for the development of functional materials. The surface properties of plants are based on physico-chemical principles and can be transferred to technical "biomimetic" materials, as successfully done for the self-cleaning properties of the Lotus leaves. This article is designed as an introduction for biologists and non biologists and should stimulate the reader to initiate or intensify the study of biological surfaces.
When rain falls on lotus leaves water beads up with a high contact angle. The water drops promptly roll off the leaves, collecting dirt along the way. This self-cleaning ability or lotus effect has, in recent years, stimulated much research effort worldwide for a variety of applications ranging from self-cleaning window glasses, paints, and fabrics to low friction surfaces. What are the mechanisms giving rise to the lotus effect? Although chemical composition and surface structure are believed important, a systematic experimental investigation of their effects is still lacking. By altering the surface structure of the leaves while keeping their chemical composition approximately the same, we report in this study the influence of micro- and nano-scale structures on the wetting behaviour of lotus leaves. The findings of this work may help design self-cleaning surfaces and improve our understanding of wetting mechanisms.
The microrelief of plant surfaces, mainly caused by epicuticular wax crystalloids, serves different purposes and often causes effective water repellency. Furthermore, the adhesion of contaminating particles is reduced. Based on experimental data carried out on microscopically smooth (Fagus sylvatica L., Gnetum gnemon L., Heliconia densiflora Verlot, Magnolia grandiflora L.) and rough water-repellent plants (Brassica oleracea L., Colocasia esculenta (L.) Schott., Mutisia decurrens Cav., Nelumbo nucifera Gaertn.), it is shown here for the first time that the interdependence between surface roughness, reduced particle adhesion and water repellency is the keystone in the self-cleaning mechanism of many biological surfaces. The plants were artificially contaminated with various particles and subsequently subjected to artificial rinsing by sprinkler or fog generator. In the case of water-repellent leaves, the particles were removed completely by water droplets that rolled off the surfaces independent of their chemical nature or size. The leaves of N. nucifera afford an impressive demonstration of this effect, which is, therefore, called the “Lotus-Effect” and which may be of great biological and technological importance.
The lotus plant's magnificent ability to repel dirt has inspired a range of self-cleaning and antibacterial technologies that may also help control microfluidic “lab-on-a-chip” devices