CANNA INDICA PLANT FIELD OF THE INVENTION

The present invention relates to a polymer with superior properties such as high aspect ratio, hierarchical super-hydrophobic and antireflective surfaces that is fabricated by bio-mimicking Canna Indica plant and method thereof to bio-mimic the properties.

BACKGROUND AND PRIOR ART

Materials, objects and processes found in nature functions from macro-scale to the nano-scale. Bio-inspiration or bio-mimetic is a tool to mimic these natural objects to develop functional materials which provide desired properties. There are a large number of examples found in nature svich as plants, bacteria, land animals, aquatic animals and insects which provide an inspiration to mimic some structural and functional properties owned by them. For example, some plant leaves and flower petals like lotus leaf, rice leaf, taro leaf and rose petal are well known for their super-hydrophobic and self-cleaning properties due to the multi-scale structural patterns present on their surfaces. This self-cleaning phenomenon also known as "Lotus effect" is due to high contact angle and low contact angle hysteresis. Similarly, moth eye that consists of an array of hexagonally arranged submicron features provides an inspiration to fabricate anti- reflective surfaces. The below table lists various non-patent literatures where bio-mimicking experiments have been conducted to achieve super-hydrophobic and high aspect ratio properties.

On water repellency - the property of water-repellency in discussed with its MathildeCallies and David dynamics, physical causes for the same and how they

Queere influence the hydrophobicity of a material

What do we need for a super- combination of multi-phases and a high roughness factor hydrophobic surface - A give best result in the creation of super-hydrophobic review on the recent progress surfaces. Diverse fabrication methods and a large variety in the preparation of of materials have been used ranging from inorganic nano superhydrophobic surfaces - particles to bulk polymeric materials to create super- Xue-Mei Li, David Reinhoudt hydrophobic surfaces.

and Mercedes Crego-Calama

Bio-inspired design of multi- Bio-mimicking of some naturally available biological scale structures for function materials which exhibit inherent multifunctional integration - Kesong Liu and integration.

Lei Jiang

Wetting, adhesion and friction The effect of micro-patterning and nano patterning on the of super-hydrophobic and hydrophobicity is investigated for two different polymers hydrophilic leaves and with micro-patterns and nano-patterns. The effect of fabricated micro/ nano- droplet size on contact angle was studied by droplet patterned surfaces - Bharat evaporation and transition criterion was developed to Bhushan and Yong Chae Jung predict when air pockets cease to exist. Microscopic study on the effect of droplet size of 20 micrometer radius on the contact angle of patterned surfaces is presented.

Super-hydrophobic surface A method to form hydrophobic surfaces using poly directly created by hydroxybutyrate-co-hydroxyvalerate. The shape of the electrospinning based on water droplet on these surfaces had contact angles hydrophilic material - Meifang ranging from 110.7 to 158.1°, with a maximum standard Zhu, WeiweiZuo, Hao Yu, deviation of 2.5°. It is found that both the micro and Wen Yang, Yanmo Chen nanostructure were important to create super- hydrophobic surfaces. Photoresist derived electrospun Here, SU-8, a negative photoresist, which is widely used carbon nanofibres with in conventional lithography, was chosen as a new tunablemorphology and surface polymer precursor to synthesize carbon nanofibres and properties - Chandra S. Sharma beads by electrospinning and subsequent pyrolysis. The et. Al formation of beaded fibres and beads was found to impart significant hydrophobicity to the electrospun carbon web, with the highest water contact angle of about 143° as compared to weakly hydrophilic smooth carbon film.

Fabrication of super- Here, the super-hydrophobic surfaces are prepared via a hydrophobic surfaces on solution-immersion method. After etching and engineering materials by a fluorination, the prepared super-hydrophobic surfaces on solution-immersion process steel and copper alloy have water contact angle of 161° ±

1° and 158° ± 1° respectively.

Ultra hydrophobic and ultra It is emphasized here that the contact angle hysteresis is lyophobic surfaces: some more important in characterizing lyophobicity than the comments and examples - Wei maximum achievable contact angle and suggest that the

Chen et. Al terms ultra hydrophobic and ultra lyophobic be reserved for materials upon which drops move spontaneously or easily on horizontal or near-horizontal surfaces.

Wetting and wetting transitions Rough and patterned surfaces were produced using on copper-based super- etching and, separately, using electrodeposition wherein hydrophobic surfaces - N.J. the roughness can be varied in a controlled manner and, Shirtcliffe et. Al when hydrophobized, these surfaces show contact angles that increase with increasing roughness to above 160°. The contact angle hysteresis on these surfaces initially increased and then decreased as the contact angle increased.

Mimicking natural super- The most recent progress in preparing manmade super- hydrophobic surfaces and hydrophobic surfaces through a variety of grasping the wetting process: A methodologies, particularly within the past several years, review on recent progress in and the fundamental theories of wetting phenomenon preparing super-hydrophobic related to super-hydrophobic surfaces are reviewed in surfaces - Y.Y.Yan, N. Gao this work.

and W. Barthlott

Wetting of regularly structured A systematic study of the wetting of structured gold gold surfaces - Mandouh E. surfaces formed by electrodeposition through monolayer Abdelsalam wt. al templates of close-packed uniform sub micrometer spheres. It is found that as the thickness of the porous film increases up to the radius of the pores, the apparent contact angle for water on the surface increases from 70° on the flat surface to more that 130°, and then with increasing thickness above the radius of the pores the apparent contact angle decreases back toward 70°. Even the role of the pore shape and size in stabilizing the nonwetting droplet on the surface is discussed.

Progress in super-hydrophobic Different methods of preparation of super-hydrophobic surface development - Paul surfaces and the development of the same over the years

Roach have been discussed. Further, the main focus is also laid on how size and shape of surface features are used to control surface characteristics.

Constructing a super- This method proposes a method of construction of a hydrophobic surface on super-hydrophobic surface on polydimethylsiloxane polydimethylsiloxane via spin substrate was constructed via the proposed vapour-liquid coating and vapour - Liquid sol-gel process in conjunction with spin coating of Sol - Gel Process - Yu-Ting dodecyltrichlorosilane. Thus forming a wrinkle like Peng et. Al structure with static contact angle of water droplet on surface about 162° with 2° sliding angle and less than 5° contact angle hysteresis. Design and fabrication of The design and fabrication of micro-textures for inducing micro-textures for inducing a a super-hydrophobic behaviour on hydrogen terminated super-hydrophobic behaviour Si surfaces with an intrinsic water contact angle of ~ 74° on hydrophilic materials - has been reported. The micro-textures consist of Liangliang Cao et. Al overhang structures with well-defined geometries fabricated by micro-fabrication technologies, which provide positions to support the liquid and prevent the liquid from entering into the indents between the micro- textures.

Lotus-like biomimetic Biomimetic hierarchical surfaces were fabricated by hierarchical structures replication of a micropatterned master surface and self- developed by the self-assembly assembly of two kinds of tubular wax crystals, which of tubular plant waxes naturally occur on the superhydrophobic leaves of

Tropaeolummajus (L.) and Leymusarenarius (L.). The optimal structural parameters for super-hydrophobicity and low static contact angle hysteresis, superior to natural plant leaves including lotus, have been identified and provide a useful guide for development of biomimetic superhydrophobic surfaces.

Purity of the sacred lotus, or It is shown that for the first time that the interdependence escape from contamination in between surface roughness, reduced particle adhesion biological surfaces - W. and water repellency is the keystone in the self-cleaning Barthlott mechanism of many biological surfaces based on the experimental data carried out on microscopically smooth and rough water-repellent plants.

Characterization and This is a survey of micro morphological characteristics distribution of water-repellent, of anti-adhesive plant surfaces. Further, an overview is self-cleaning plant surfaces - given on the occurrence of water-repellency among C. neinhuis and W.Barthlott different life forms and within different habitats. The importance of roughness and water-repellency as the basis of an anti-adhesive, self-cleaning surface, in comparison to other functions of microstructures, is discussed.

Biomimetics: lessons from This provides a broad overview of the various objects nature - an overview - Bharat and processes of interest found in nature and applications

Bhushan under development or available in the marketplace.

Bio-inspired, smart, multiscale A strategy for the design of bio-inspired, smart, interfacial materials - Fan Xia multiscale interfacial materials is presented and put in to and Lei Jiang context with recent progress in the field of BSMI materials spanning natural to artificial to reversibly stimuli-sensitive interfaces.

Biologically inspired surfaces: The effect of roughness on wetting mechanisms and Broadening the scope of relevant roughness parameters and ways to broaden the roughness - Michael concept and scope of surface roughness are discussed in Nosonovsky et. Al this paper.

Biomimetic Superhydrophobic It is shown that the contact angle hysteresis depends surfaces: multiscale approach - upon both kinetic effects at the triple line and adhesion Michael Nosonovsky et. Al hysteresis and that the magnitude of the two

contributions is comparable. The transition between the composite and wetted states is a linear effect with the microdroplet radius proportional to the pitch over pillar diameter. It also shown that wetting of a superhydrophobic surface is a multiscale phenomenon that involved three scale lengths.

Biomimetism and This review is about supra-molecular chemistry that is of bioinspiration as tools for the interest for complex macromolecular assemblies such as design of innovative materials molecular crystals, micelles and membranes; hybrid and systems - Clement Sanchez materials that combine organic and inorganic

et. Al components on a nanoscale with innovative controlled textures etc.

How Plants Keep Dry: A It is showed that the water repellence if certain plat Physicist's point of view - leaves can be explained by considering surface roughness Alexander Otten et. Al on different length scales and sometimes additional elastic structures covering the surface. The minimum hierarchical degree of roughness needed to achieve superhydrophobic behaviour has not yet been revealed, but plants such as for example Indian Cress seem to get along with three different length scales of roughness.

Micro-, nano- and hierarchical The effect of micro and nano patterned polymers on structures for super- hydrophobicity was studied by analysing the roughness hydrophobicity, self-cleaning factor and static contact angle. It was found that and low adhesion - Bharat increasing roughness on a hydrophilic micro- or Bhushan, Yong Chae Jung and nanostructured surface decreases the contact angle, Kerstin Koch whereas increasing roughness on a hydrophobic micro- or nanostructured surface increases the contact angle. Micro-, nano- and hierarchical structures led to a high static contact angle, e.g. for lotus wax of the order of 160, 167 and 173°, respectively. Contact angle hysteresis for the hierarchical structure was the lowest.

Diversity of structure, This paper presents the diversity of plant surface morphology and wetting of structures from a single cell to multi-cellular surface plant surfaces - Kerstin Koch sculptures. It presents a guide for the description of et. Al cellular and sub-cellular plant surface structures, which include hairs, wax crystals and surface folding. In the plant surface, micro- and nano- structures play a special role, and a large diversity of surface structures exists at different size levels. Biomimickedsuperhydrophobic The surface textures of the selected plant leaves are first polymeric and carbon surfaces biomimicked by replica molding using different - Chandra S.Sharma et. Al polymers, polydimethylsiloxane, polystyrene and resorcinol-formaldehyde gel. RF gel introduced by Pekala is a especially attractive polymeric precursor for glassy carbon. It is shown that replication of the microscale featured of natural leaves on polymer surfaces generates hydrophobicity in these polymeric surfaces.

Fabrication of artificial Lotus Hierarchical structures of the lotus were fabricated by a leaves and significance of fast and precise molding of the lotus leaf micro structure, hierarchical structure for super- and self-assembly of the natural lotus wax deposited by hydrophobicity and low thermal evaporation to create the wax tubules adhesion - Kerstin Koch et. Al nanostructures. Tubule formation was initiated by exposure of the specimens to a sol vent vapour phase at a selected temperature. It is shown that the hierarchical structures further improve the super-hydrophobicity property and show low contact angle hysteresis, superior to that of the natural lotus leaves.

Artificial hairy surfaces with a A nearly perfect hydrophobic interface by dint of nearly perfect hydrophobic mimicking hairs of arthropods was achieved in this response - Shu-Hau Hsu experiment by a membrane casting technique on polypropylene substrates. There is no chemical treatment needed in this step. The ultralow adhesion to water droplets is believed to be attributed to the mechanical response of the artificial hairs.

Fabrication of hairy polymeric A facile and efficient method for fabricating gecko- films inspired by Geckos: inspired, hairy hard poly structures, composed of wetting and High adhesion nanopillars with controllable lengths is reported. The Properties - WooKyung Cho structures are generated by utilizing an anodic oxide et. Al membrane as a replication template and vinyl-terminated glass as substrate. The resulting hairy h-PDMS -coated glass surface shows both the static water contact angle as high as 150.5° ± 0.4° and high adhesion to water.

32. Petal Effect: A Large scale fabrication of the superhydrophobic and superhydrophobic state with adhesive petal layer can be achieved by using the petal as high adhesive force - linFeng a mold in the duplicating process, which is possible for et. Al industrial production with high throughputs.

33. Soft Lithography - Younan Xia This paper discloses an alternative to non-photo et. Al lithographic micro fabrication methods that circumvents the diffraction limits of photolithography, provide access to 3D structures and tolerate a wide rage of materials and surface chemistries, and also be inexpensive and accessible.

34. Wettability of porous surfaces - The analysis of apparent contact angles for rough A B D Casste and S. baxter surfaces is extended to porous surfaces, particularly those encountered in natural and artificial clothing. Water repellent clothing structures are discussed by means of this analysis, and it is shown that the water-repellency of the duck is due to the structure of its feathers rather than to any exceptional proofing agent.

35. Super-hydrophobic states - Two distinct hypotheses are classically proposed to AurelieLafuma and David explain the effect super-hydrophobicity i.e. the roughness

Quere factor and Cassie model. However, it is shown here that both situations are very different from their adhesive properties, because Wenzel drops are found to be highly pinned. In addition, irreversible transitions can be induced between Cassie and Wenzel states, with a loss of the anti-adhesive properties generally associated with super-hydrophobicity.

Most of the plant leaves, petals and animal surfaces exhibit super-hydrophobic behavior due to low aspect ratio hierarchical structure present on their surfaces. However, there are only a few reports of mimicking the plant surfaces with high aspect ratio patterns except hairy surface leaves. Structures with low aspect ratio find limited use as lower surface area may not be suitable for various applications like energy storage devices including solar cells, filtration products etc. Further, self-cleaning functionality and anti-reflectivity to these bio-mimicked hierarchical structures are integrated here.

As mentioned in the above paragraph, fabrication of antireflective surfaces has been inspired by moth eye due to its low aspect ratio submicron features which are not able to resolve the light. Fabrication of array of submicron structures over a large area is always expensive, time consuming and techniques available are specific to materials. Multi-functionality (super- hydrophobicity as well as anti-reflectivity) with high aspect ratio multi-scale (hierarchical) structures might find a range of applications including solar cells with enhanced efficiency and self cleaning ability and thus extended durability however this is not yet been achieved. Various patents and patent applications like US20130087530, US2010/0028604, US8093725, and US6210595 have disclosed methods of bio-mimicking and method of producing polymers with either high aspect ratio or super-hydrophobicity separately. The results achieved by these mentioned inventions are also not as superior as compared to the present invention. The present invention puts a light on the above untouched area to produce a fabricated polymer material with multi-functionality and high aspect ratio multi-scale structures which possess self- cleaning ability and extended durability. Here, the properties of Indian Carina seedpod which is also known as Carina Indica, belonging to Cannaceae family, a native of the Caribbean and tropical America are exploited to bio-mimic the same. Here, the plant seedpod, petal and leaf are used as master templates for fabricating large area super-hydrophobic and antireflective polymer surfaces.

The fabrication is done by bio-mimicking the properties of Carina Indica plant especially the properties of seedpod, flower petal and leaf. As of now, no bio-mimicking experiments have been conducted on the seed pod of a plant. Seedpod possesses high aspect ratio structures which correspond to higher external surface area. The larger surface area is useful for various applications including energy storage devices such as lithium ion battery anode materials where it allows more lithium ions to intercalate and thus enhancing the specific capacity. Other applications in which high surface area may be useful include adsorption for filtration applications etc.

Another important aspect of this invention is one can fabricate high aspect ratio super- hydrophobic surfaces in carbon using carbon polymer precursors like RF gel as depicted here. Carbon based super-hydrophobic surfaces with larger surface area has enormous applications in micro fluidic devices, water and air filtration and anode materials for Lithium ion batteries.

SUMMARY OF THE INVENTION

The present invention discloses a polymer possessing superior properties like high aspect ratio, hierarchical super-hydrophobicity and anti-reflective properties. This polymer is fabricated by bio-mimicking Canna Indica plant's seed pod or petal or leaf through exploiting its multi- functionality properties.

The process of bio-mimicking or fabrication of polymer comprises the steps of obtaining negative replica from the subject part of the plant (seedpod or leaf or petal) using Polydimethylsiloxane (PDMS) solution; and obtaining positive replica from the negative replica using Resorcinol formaldehyde (RF) sol. The obtained positive replicas of the seedpod/ leaf/petals of Canna Indica are investigated and inferred to show superior properties like high aspect ratio, super hydrophobicity and anti-reflective properties. There are four major aspects of this invention namely (1) Super-hydrophobicity; (2) Anti- reflectivity; (3) High aspect ratio and thus high surface area structures; and (4) Fabrication in polymers including carbon, more particularly all these aspects are brought together in a polymer. Industrial applications of super-hydrophobic surfaces include in textiles, paints, anti bio fouling surfaces to avoid corrosion. A polymer with super-hydrophobicity and anti-reflectivity features cover wider range of applications like optics (car windshields, architectural glasses) and solar cells. Polymer solar cells with anti-reflective as well as super-hydrophobic surface will not only enhance the efficiency but also durability. Further if these properties are achieved in carbon materials which are electrically conductive, one can explore applications in electrode materials in batteries, high performance fuel cells, super-capacitors and bio-sensors. BRIEF DESCRIPITON OF THE DRAWINGS

The above-mentioned product and the method of manufacture of the same with other advantages of this present disclosure, and the manner of attaining them, will become more apparent and the present disclosure will be better understood by reference to the following description of embodiments of the present disclosure taken in conjunction with the accompanying drawings, wherein:

Figure 1 A shows a picture of the seedpod of Canna Indica plant; Figure IB shows a picture of the flower petals of Canna Indica plant; Figure 1C shows a picture of the leaves of Canna Indica plant;

Figure 2 illustrates schematic of fabrication of negative PDMS replica and positive resorcinol- formaldehyde (RF) gel replica of high aspect ratio Canna Indica seedpod;

Figure 3 illustrates SEM images captured wherein: a - d showing surface morphology of original Canna Indica seedpod; e - h showing surface morphology of negative PDMs replica; and I - 1 showing surface morphology of positive RF gel replica at various magnifications;

Figure 4 illustrates SEM images captured wherein: al- dl showing surface morphology of original Canna Indica petal; a2 - d2 showing surface morphology of negative PDMS replica; and a3 - d3 showing surface morphology of RF gel positive replica at different magnifications; Figure 5 illustrates SEM images captured wherein: al- dl showing surface morphology of original Canna Indica leaf; a2 - d2 showing surface morphology of negative PDMS replica; a3 - d3 showing surface morphology of RF gel positive replica at different magnifications; Figure 6 illustrates photos captured by a high definition digital camera and goniometer camera wherein: figure a and b showing the water droplet on original Canna Indica seedpod; figure c and d showing the water droplet on negative PDMS replica of the seedpod; and figure e and f showing the water droplet on RF gel replica of the seedpod; Figure 7 illustrates photos captured by a high definition digital camera and gonimeter camera wherein: figure al and a2 showing the water droplet on original Canna Indica petal; figure bl and b2 showing the water droplet on negative PDMS replica of the petal; and figure cl and c2 showing the water droplet on RF gel replica of the petal; Figure 8 illustrates photos captured by a high definition digital camera and gonimeter camera wherein: figure a showing the water droplet on original Canna Indica leaf; figure b showing the water droplet on negative PDMS replica of the leaf; and figure c showing the water droplet on RF gel replica of the leaf; Figure 9 illustrates a graph showing the reflection measurement of original Canna Indica petal, plain PDMS, plain RF, structured PDMS surface (negative PDMS petal replica) and Structured RF surface (positive RF gel petal replica) respectively at 30 ⁰ and wavelength ranging from 400nm-800nm; Figure 10 illustrates a graph showing the reflection measurement of original Canna Indica leaf, plain PDMS surface, structured PDMS surface (negative PDMS leaf replica) and structured RF gel surface (positive RF gel leaf replica) at 30 ⁰ and wave length ranging from 400nm-900nm;

Figure 11 illustrates a graph showing the variable angle of reflectance measurement of original Canna Indica petal and their bio-mimicked surfaces wherein petal bio-mimicked surfaces having low reflection compared to the standard surfaces irrespective of the angle of incidence of light; and

Figure 12 illustrates a graph showing the variable angle of reflectance measurement of original Canna Indica leaf and their bio-mimicked surfaces wherein leaf bio-mimicked surfaces having low reflection compared to the standard surfaces irrespective of the angle of incidence of light.

DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the exemplary embodiment(s) of the invention. Before describing the detailed embodiments that are in accordance with the present disclosure, it should be observed that the embodiments reside primarily in combinations of process/ method steps and components of product. In this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, product, method, article, device or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, product, method, article, device, or apparatus. An element proceeded by "comprises ...a" does not, without more constraints, preclude the existence of additional identical elements in the process, product, method, article, device or apparatus that comprises the element.

Any embodiment described herein is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this detailed description are illustrative, and provided to enable persons skilled in the art to make or use the disclosure and not to limit the scope of the disclosure, which is defined by the claims.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present method of fabrication of the polymer by bio-mimicking Canna Indica's seedpod, leaf and petal. It will be apparent, however, to one skilled in the art that the present invention can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form only in order to avoid obscuring the present invention.

The present invention discloses bio-mimicking of Indian Canna seedpod which is also known as Canna Indica, belonging to Cannaceae family, a native of the Caribbean and tropical America. It is also been widely cultivated as a garden plant. More particularly, the plant seedpod, petal and leaf as shown in figure 1A, IB and 1 C are used as master templates for fabricating large area super-hydrophobic and antireflective polymer surfaces. The below paragraphs illustrates the method of fabrication of the polymer by bio-mimicking seedpod, leaf and petal of Canna Indica to produce a polymer with superior quality which is super-hydrophobic in nature with anti- reflective properties and possessing high aspect ratio.

Fabrication of negative PDMS Replica: The part of the Canna Indica plant which needs to bio-mimicked is cut into small piece of 1cm x lcm length by breadth, and dried at 40 ^° C for 1 hour to remove moisture content. The dried part is fixed to a clean glass slide or plane surface with double sided tape as shown in Figure 2(a). Then Polydimethylsiloxane (PDMS) solution (10: 1 weight ratio of sylgard 184, polymer elastomer and cross-linking agent) is poured on to the dried pieces (of plant) which shall be kept for de-aeration in vacuum desiccators to avoid bubble formation. Later the sample is kept in vacuum oven at 80 ^° C for 12 hrs for curing after which, the PDMS sample is swelled in glass petridish containing chloroform for 1 hour. During this treatment, the PDMS sample gets detached from the subject part and forms a negative replica of the mold, which is then dried for 1 hour at room temperature. Resorcinol formaldehyde (RF) sol is used to make positive replica from negative replica which is an organic precursor to carbon upon pyrolysis. This RF sol was prepared in aqueous form which contains resorcinol, formaldehyde, water and potassium carbonate. 1.27 g resorcinol and 1.3 ml formaldehyde are mixed and stirred together continuously until it turns into a clear solution. In another beaker, 0.136 gm potassium carbonate is taken and 5.6 ml of water is added followed by stirring together to get a clear solution. Finally, these two solutions are mixed and stirred continuously for 15 min until RF sol is changed to golden yellow colour.

Before pouring the RF sol into the negative replica, the negative PDMS replica is swelled in chloroform for 1 hour as mentioned above or the PDMS replica is UV treated for 15 minutes. This helps RF sol to wet the pores, since PDMS is hydrophobic in nature. It is ensured that the sol should be little viscous before pouring into the negative PDMS replica to avoid brittleness of the positive RF gel. The RF sol is poured to the swelled PDMS replica as shown in Figure 2(f) and de-aerated for 30 minutes in vacuum desiccators to remove any gas bubbles. Then the sample is kept at room temperature for 12 hours to undergo gelation. After sol is converted into gel, the same is peeled off from the negative replica by swelling the PDMS sample in chloroform shown in Figure 2(g) for 1 hour and allowed to dry at 40°C to 50°C in hot oven for 12 hours to avoid any breakage. The dried RF replica is removed from oven to get the positive replica.

The negative and positive replica of the seed pod, leaf and flower petals of the Carina Indica are prepared in the method as mentioned above and are investigated for the claimed properties such as high aspect ratio, super-hydrophobicity and anti-reflectiveness as follows.

Investigation of surface morphology: Illustration 1:

Now the surface morphology of the original seed pod, negative PDMS replica and the positive RF replica are observed and studied under Scanning Electron Microscope (SEM) which is summarised as shown in Figure 3. Figure 3a-3d shows the surface features of the original seedpod at various magnifications such as 500 μιη, 200 μηι, 50 μπι and 10 μη respectively. Figure 3a shows the high aspect ratio tapered structures whereas Figure 3b magnifies the complex subsurface folded like structures on an individual tapered bump. The average height of these tapered pillars was 2.5 mm while on top of each tapered pillar, folded surface patterns with average width 184 μιη are observed. At further higher magnification as in Figure 3c and 3d, it is clearly observed that the submicron spikes found on individual tapered bump structure with average feature size 287 nm. The complex nature of surface patterns on the seedpod can be well understood with features size varying almost four orders of magnitude. Figure 3e-3h shows the images of negative PDMS replicas at the same magnifications mentioned above, consisting of pores with surface patterned thoroughly inside their walls. The average width of these pores was 488 μη as shown in Figure 3e while another layer of patterns on inner surface walls of these pores consists features of average size 64 μιη (refer Figure 3f). Figure 3g and 3h shows the inner view of the pores at higher magnification with protrusions feature size appearing in submicron range (contrast was not good to image inner view at higher magnification). Figure 3i-31 shows the surface morphology of the positive RF xerogel replica. As observed in Figure 3i and 3j, the high aspect ratio (average height 2.1 mm) tapered structures with patterns on its surface with average length of 1 18 μιη are replicated. Further magnified view as shown in Figure 3k shows the inner patterns with feature size 47 μηι. Figure 31 shows high magnification image of these patterns and it is observed that on each feature, there are signatures of submicron protrusions.

Illustration 2:

The surface morphology of the original flower petal, its negative PDMS replica and the positive RF replica are observed and studied under Scanning Electron Microscope (SEM) which is summarised as shown in Figure 4. Figure al- dl shows the surface features of the original petal at various magnifications such as 500 μπι, 100 μιη, 20 μπι and 10 μηι respectively. It is observed that folded layered structures with size range (20 μη ) (Figure 5bl -cl) spread all over. Further higher magnification image (5dl) shows signature of uneven surfaces inside these folded structures with submicron size wrinkle like patterns. Figure 5a2- d2 shows the surface features of the negative replica in PDMS for the petal at various magnifications such as 500 μηι, 100 μηι, 20 μ ^η ι and 10 μηι respectively. A uniform array of holes over a large area of about 17μηι is observed as shown in Figure 5 a2-c2. Further higher magnification image (Figure 5d2) shows the inside view of these holes having submicron wrinkles type features. Figure 5a3- d3 shows the surface features of the positive replica in RF xerogel for the petal at various magnifications such as 500 μηι, 100 μιη, 20 μηι and 10 μηι respectively. A nicely arranged array of around 15 μιη size hemispherical surface features is also observed. Though it is not very clear however one can observe carefully submicron features present on each of these hemispherical droplet arrays (small tiny bumps like features) (Figure 5d3). Illustration 3:

The surface morphology of the original leaf of Canna Indica, its negative PDMS replica and the positive RF replica are observed and studied under Scanning Electron Microscope (SEM) which is summarised as shown in Figure 5. Figure al- dl shows the surface features of the original petal at various magnifications such as 500 μιη, 100 μιη, 50 μπι and 20 μηι respectively. At higher magnifications a combination of micro/nanostructures features of about 23μΓη/600ηηι is observed as shown in Figure 5(cl) and (dl). SEM analysis was also done for PDMS negative replica where small holes like structures are seen as shown in Figure 5 (a2), (b2) and (c2). At higher magnifications, holes of about 17 μιη is observed as shown in Figure 5(c2). Finally, SEM analysis is also done for RF gel positive replica as shown in Figure 5 (a3, b3, c3, d3). It is observed that some micro-structured features of about 26 μη are present as shown in Figure 5 (c3) with some signatures of submicron features (Fig. 5d3).

Investigation of Super-hydrophobicity:

Illustration 4:

Figure 6a, 6c and 6e show the image of water droplet on original seedpod, negative PDMs replica and positive RF gel replica respectively. The water contact angle of the original and other replicas as mentioned above is measured by contact angle goniometer and are found to be 151°, 136° and 154° respectively. Further contact angle hysterisis for all these caes are less than 5° which confirms the presence of super-hydrophobicity in the bio-mimicked polymer surfaces.

Illustration 5:

Figure 7al to cl show the image of water droplet on the petal of Canna Indica, negative PDMs replica and positive RF gel replica respectively. The water contact angle of the original petal is found to be 137° whereas the same for negative PDMS replica and positive RF replica are found to be 152° and 140° respectively. The contact angle hysteresis for all the above cases are less than 5° confirming the presence of super-hydrophobicity in the bio-mimicked polymer surfaces.

Illustration 6:

Figure 8a to c show the image of water droplet on the leaf of Canna Indica, negative PDMs replica and positive RF gel replica respectively. The water contact angle of the original leaf is found to be 122° whereas the same for negative PDMS replica and positive RF replica are found to be 124° and 135° respectively. These results show the strong hydrophobic behaviour of Canna Indica leaf and its bio-mimicked polymer surfaces. Investigation of Anti-reflective properties:

The bio-mimicked Canna Indica petal and leaf surfaces having hierarchical structures in PDMS and RF gel are investigated for their anti-reflective properties. To check how much of light is reflected from the original petal surface and replicated surfaces, reflection studies are done for original Canna Indica petal, bio-mimicked surfaces (negative PDMS petal replica and positive RF gel petal replica), plain PDMS and plain RF gel of 5cm x 5 cm area samples by using UV- VIS spectroscopy of wavelength ranging from 400nm - 800nm, which is a visible wavelength at an angle of incidence of 30°. Illustration 7:

Figure 9 shows a graph raised between the wavelength on X-axis and percentage of reflection on Y-axis illustrating the reflection measurement for original petal and its replicas. The curve in light blue color indicates the plain RF gel surface showing reflection of 0.68%, where as the curve in green color indicates the structured RF gel sample having bumps (positive RF petal replica) shows 0.02%, having significant decrease in reflection compared to plain RF gel surface. The curve in light purple color indicates plain PDMS surface showing reflection of 0.29%, where as the curve in dark blue color indicates structured PDMS surface having holes (negative PDMS petal replica) showing a reflection of 0.04%, having significant decrease in reflection compared to the plain PDMS surface. The curve in light red color indicates original Canna Indica petal showing reflection of 0.03% up to 510nm and there is a gradual increase in reflection from 0.03% to 0.27%) up to 630nm and remains constant till 800nm. This proves that the bio- mimicked polymer surfaces show less reflection than the standard surfaces.

Illustration 8:

Figure 10 shows a graph raised between the wavelength on X-axis and percentage of reflection on Y-axis illustrating the reflection measurement for original leaf and its replicas. The curve in light blue color indicates the plain RF gel surface showing a reflection of 0.68%, whereas the curve in green color indicates the structured RF gel surface (positive RF leaf replica) showing 0.02%, having significant decrease in reflection compared to the plain RF gel surface. The curve in light purple color indicates plain PDMS surface showing reflection of 0.29%, whereas the curve in dark blue color indicates structured PDMS surface (negative PDMS leaf replica) showing 0.1%, illustrating significant decrease in reflection compared to the plain PDMS surface. The curve which is in light red color indicates original Canna Indica leaf showing reflection of 0.03% up to 690nm and there is gradual increase in reflection from 0.03% to 0.27% up to 740nm after which it remains constant till 800nm. Like petal bio-mimicked surfaces, leaf bio-mimicked polymer surfaces also show less reflection than the standard surfaces. Determination of amount of light reflected: Illustration 9: To check how much of light is reflected from the original petal surface and replicated surfaces by varying angle of incidence of light and keeping wavelength constant, variable angle reflection studies are done for original Canna Indica petal, bio-mimicked surfaces of 5mm thickness (negative PDMS petal replica and positive RF gel petal replica), plain PDMS surface and plain RF gel surface of 5mm thickness by using UV-VIS spectroscopy of keeping wavelength constant 700nm and varying the light incident angle from 30° to 70 ^° . The graph drawn between the angle of incidence in X-axis and the percentage of reflection as resulted in Y-axis is shown in Figure 11. The curve in green indicates the plain RF surface showing reflection of 0.8% at an angle of incidence of light of 30°, having gradual increase in reflection up to 4.3% at 60° of incident angle of light and a sudden decrease in reflection reaches almost 0% at 70° incident angle of light. The curve in light blue colour indicates the structured RF surface (positive RF petal replica) showing reflection of almost 0% at all angle of incidence of light. The curve in light red colour indicates plain PDMS surface showing reflection of 0.3% at 30° angle of incidence of light and gradually decreasing almost to 0% at 50° angle of incidence of light. Then it gradually increases and shows 3.7% reflection at 70° angle of incidence of light. The purple curve indicates structured PDMS surface, which shows almost reflection of 0% at all angle of incidence of light. The curve in blue colour indicates original petal showing reflection of 0.2% at all angle of incidence of light. From the results, it is observed and inferred that the bio-mimicked petal surfaces shows significant less reflection compared to the standard surfaces irrespective of the angle of incidence of light. Illustration 10:

Figure 12 summarises the graph between the angle of incidence in X-axis and the percentage of reflection as resulted in Y-axis illustrating the amount of light reflected from the original leaf surface and replicated surfaces by varying angle of incidence of light and keeping wavelength constant. Variable angle reflection studies are done for original Canna Indica leaf, bio-mimicked surfaces of 5mm thickness (negative PDMS leaf replica and positive RF gel leaf replica), plain PDMS surface and plain RF gel surface of 5mm thickness by using UV-VIS spectroscopy of keeping wavelength constant 700nm and varying the light incident angle from 30° to 70°. The purple curve indicates the plain RF surface showing reflection of 0.8% at 30° incident angle of light, having gradual increase in reflection up to 4.3% at 60° incident angle of light and sudden decrease in reflection reaches almost 0% at 70° incident angle of light. The curve in light blue color indicates the structured RF surface (positive RF leaf replica) showing reflection of almost 0% from 30° to 50° angle of incidence of light and then a gradual increase of reflection of about 0.3% at 70° angle of incidence of light. The curve in light green color indicates plain PDMS surface showing reflection of 0.3% at 30° angle of incidence of light and gradually decreases almost 0% of reflection at 50° angle of incidence of light. It then gradually increases and shows 3.7% reflection at 70 ^° angle of incidence of light. Whereas the curve in light red color indicates structured PDMS sample (negative PDMS leaf replica) showing almost reflection of 0.2% from 30° to 40° angle of incidence of light and then a gradual increase of reflection thereby reaching 0.7% at 70° angle of incidence of light. The curve in blue color indicates original leaf showing reflection of 0.2% from 30° to 60° angle of incidence of light and reflection of 0.3% at 70° angle of incidence of light. It is observed that bio-mimicked leaf surface also shows less reflection than the standard surfaces like bio-mimicked petal surface.