A method of preparing disposable water repellent mask and a product thereof

Abstract

ABSTRACT “A METHOD OF PREPARING A WATER REPELLENT AND ANTI-VIRAL COATING AND A PRODUCT THEREOF” The present invention provides a method of preparing a water repellent and anti-viral coating and a product thereof. More particularly, the present invention provides a method of preparing a water repellent and anti-viral coating on wide range of fibrous substrates which includes regular hydrophilic masks and tissue papers which provides stability to the masks and prevents penetration of water droplets that carries infectious agents. Figure 1 on sheet no. 1 of the drawings may accompany the abstract when published.

Description

FIELD OF THE INVENTIONThe present invention provides a method of preparing a water repellent and antiviralcoating and a product thereof. More particularly, the present inventionprovides a method of preparing a water repellent and anti-viral coating on widerange of fibrous substrates which includes regular hydrophilic masks and tissuepapers which provides stability to the masks and prevents penetration of waterdroplets that carry infectious agents.BACKGROUND OF THE INVENTIONMany countries are stockpiling face masks for use as non-pharmaceuticalinterventions to reduce viral transmission during an influenza pandemic. Muchtime and effort are devoted to develop an optimal strategy for the use of pandemicvaccines and antivirals, in addition to non-pharmaceutical measures during apandemic period. Given the lack of a specific vaccine against the pandemic virusesduring pandemic period mitigation measures have so far focused on identifying,treating, and isolating people who have the disease, and educating the public aboutthe steps that individuals can take to reduce transmission. Therefore, nonpharmacologicalpublic health interventions including use of face masks aretherefore likely to play a vital role in mitigating disease spread, particularly indeveloping countries.A surgical face mask is a loose-fitting, disposable device that creates a physicalbarrier between the mouth and nose of the wearer and potential contaminants inthe immediate environment. It helps to block large-particle droplets, splashes,sprays, or splatter that may contain infectious agents such as viruses and bacteriaand prevents from reaching to mouth and nose of the user. It also helps to reduceexposure of saliva and respiratory secretions to others. Surgical masks are not to beshared and may be labelled as surgical, isolation, dental, or medical proceduremasks. They may come with or without a face shield. These are often referred toas face masks, although not all face masks are regulated as surgical masks. Surgicalmasks are made in different thicknesses and with different ability to protect personsfrom contact with infectious and other harmful agents. These properties may alsoaffect how easily the person breathes through the face mask and how well thesurgical mask protects.While a surgical mask may be effective in blocking splashes and large-particledroplets, a face mask, by design, does not filter or block very small particles in theair that may be transmitted by coughs, sneezes, or certain medical procedures.Surgical masks also do not provide complete protection from germs and othercontaminants because of the loose fit between the surface of the face mask and yourface.Another kind of more sophisticated mask is called a respirator particularly, N95respirator. These are very specially engineered facemasks that are designed to filterout about 95 percent of the particles that might be moving toward our breathingzone when breathing in air. These masks remove very, very small particles andprevent from inhaling things that are the size of a virus or other infectious agents.The problem with a respirator is that if there's any gap between the respirator fittingto the face and the face itself then the air is coming in around the mask, and so itsfiltration isn't obviously 95 percent.However, there are many factors which may compromise the overall effectivenessof these measures. Poor training, lack of guidance and consistency in the use ofmasks, improper use and for N95 respirators, the need for fit-testing, may limit theirusefulness. Also, the presumption is that exhaled moisture clogs the voids in thefibrous filtration media thereby increasing the breathing resistance of therespirators. Because increased breathing resistance at low-to-moderate work ratesaugments the work of respiration via the additional physiological burden ofcompensatory mechanisms e.g. increases in respiratory rate, tidal volume, andheart rate, the exhaled moisture effects the breathing resistance of the respiratorsand determines the appropriate wear times. As a result, most of the respirators areused for limited period as they do not have improved moisture resistant filters. Suchmasks are highly expensive for use in developing country.Due to its inherent hydrophilic nature, the aqueous phase that contains infectiousagents can readily wet on such interfaces and infectious tiny agents is likely topenetrate through the surgical mask on prolonged use. Thus, the conventionalsurgical face masks are not able to provide much needed protection from theaqueous phase and as it readily wet by aqueous phase. On the other side, tissuepapers, which is inexpensive fibrous substrate for potential use in preparing facemask, is readily disintegrated by aqueous exposures. Since the regular tissue papermasks are prone to get degrade in aqueous phase and do not provide water repellentproperties therefore, people using hydrophilic regular masks and regular tissuepaper mask are prone to water droplets carrying the infectious agents that mightpenetrate through mask.US 20060130841 discloses a face mask for reducing fogging of eyewear. The facemask may include a body portion that is configured to be placed over a mouth andat least part of a nose of a user. The body portion may have an outer facing surfaceand an inner facing surface opposite from the outer facing surface. The bodyportion may have at least one horizontal fold and a plurality of vertical folds whichcreate a large breathing chamber when unfolded. However, the cited art is silent onthe water repellent properties of the face mask which the present inventionprovides.Therefore, there is a need to provide disposable and economic water repellent maskwhich provides stability and restricts penetration of water droplets that carryinfectious agents and is biodegradable in nature and provides better moistureresistance and much needed protection to the user from the infectious agents.OBJECT OF THE INVENTIONThe main object of the present invention is to provide a method of preparing awater repellent and anti-viral coating and a product thereof.Another object of the present invention is to provide a disposable water repellentmask comprising of a superhydrophobic coating and a fibrous substrate.Yet another object of the present invention is to provide a method of preparing adisposable water repellent mask by providing superhydrophobic coating on fibroussubstrates.Yet another object of the present invention is to provide a superhydrophobiccoating comprising of a mixture of small molecule-based reactants is prepared inorganic solvent and spray deposited on fibrous substrates.Yet another object of the present invention is to provide a disposable water repellentmask which provides stability and restricts splashing of body fluids during thesurgical intervention and is biodegradable in nature.Yet another object of the present invention is to provide a superhydrophobiccoating comprising of molecules having a long hydrophobic tail and metal oxidesis prepared for possible use in the contact killing of the virus.Still another object of the present invention is to provide a disposable mask to avoiddroplet infection with respiratory pathogens such as influenza virus, coronavirusand respiratory syncytia virus.SUMMARY OF THE INVENTIONIn an embodiment, the present invention provides a method of preparing adisposable water repellent mask and a product thereof. More particularly, thepresent invention provides a method of preparing a disposable water repellent maskby preparing superhydrophobic coatings on a wide range of fibrous substrateswhich includes regular hydrophilic masks and tissue papers.In yet another embodiment, the present invention provides a disposable waterrepellent mask comprising of a superhydrophobic coating and a fibrous substrate;wherein, the superhydrophobic coating is a mixture of small molecule-basedreactants prepared in organic solvent and spray deposited on fibrous substrates. Thesmall molecule-based reactants include but is not limited to octadecyl acrylate andits fluorinated derivatives and 3-(2-Aminoethylamino) propyl trimethoxysilane).The fibrous substrates include but are not limited to polyurethane fabrics, cottonfabrics, regular hydrophilic mask and tissue papers. The organic solvents includebut is not limited to ethanol, acetone, toluene. Superhydrophobicity is achieved onevaporation of reaction solvent. Temperature (below 70°C) is applied for rapidevaporation of reaction solvent.BRIEF DESCRIPTION OF THE DRAWINGThe object of the invention may be understood in more details and more particulardescription of the invention briefly summarized above by reference to certainembodiments thereof which are illustrated in the appended drawings, whichdrawings form a part of this specification. It is to be noted, however, that theappended drawings illustrate preferred embodiments of the invention and aretherefore not to be considered limiting of its scope, for the invention may admit toother equally effective equivalent embodiments.Figure 1 shows digital images of beaded water droplets on various fibroussubstrates.Figure 2(a) shows FTIR-ATR spectra for the individual solution of selected smallmolecules-octadecylacrylate (ODAc, black) and [3-(2 Aminoethylamino)propyl]trimethoxysilane (AEAPTMS, yellow) in ethanol in accordance with thepresent invention.Figure 2(b) shows plots accounting the changes in static contact angle on thesynthesized superhydrophobic coatings in accordance with the present invention.Figures 2(c)-(f) shows FESEM images of bare fibrous substrate and smallmolecules derived coatings on the fibrous substrates, where the deposition solutionswere prepared by changing the concentrations of the reaction mixture inaccordance with the present invention.Figure 3(a) and Figure 3(b) shows digital images of the reaction mixture of ODAcand AEAPTMS after mixing the selected reactants in ethanol for 10 minutes and200 days in accordance with the present invention.Figure 3(c) and Figure 3(d) shows digital image and contact angle image (inset) ofbeaded water droplets on the coated fabric in accordance with the presentinvention.Figure 3(e) and Figure 3(f) shows continuous water jet flow on the coated fabric;and digital image of the coated fabric under water where the shiny interfaceappeared due to entrapped air layer in the coated surface respectively in accordancewith the present invention.Figure 3(g) shows digital image of Indian Institute of Technology GuwahatiInstitute logo printed fabric with and without coating, where optically transparentand superhydrophobic coating was applied on half of the area (left side of the dottedline) in the image.Figures 3(h)-(j) shows demonstration of the rolling of beaded water droplet (10 μL)on the tilted (6˚) superhydrophobic in accordance with the present invention.Figure 4(a) shows schematic representing the 1,4-conjugate addition reactionbetween amine group of [3-(2-Aminoethylamino)propyl]trimethoxysilane andacrylate group of different alkyl acrylates (ODAc, dodecylacrylate (DDAc) andhexyl acrylate (HAc)). Figure 4(b) showing FTIR-ATR spectra of two distinctdeposition solutions, labelled as DS 2 (mixture of HAc and AEAPTMS; 1:1) andDS 3 (DDAc and AEAPTMS; 1:1) were recorded at 0 minute (blue) and 10minutes (red) in accordance with the present invention.Figures 4(c)-(i) represents advancing and receding water contact angle images ofbeaded water droplet on the coated interfaces where the deposition solutions wereprepared separately by associating HAc (C, F), DDAc (D,G) and ODAc (E,H) withAEAPTMS; and adhesion force profiles for the coatings that were derivedindividually by reacting AEAPTMS with HAc (red), DDAc (green) and ODAc(blue), respectively in accordance with the present invention.Figure 5(a) shows plot showing the change in static contact angle (black) andcontact angle hysteresis (red) of beaded water droplet on the nonadhesivesuperhydrophobic coating during the repetitive (3750 cycles);Figures 5 (b)-(g) shows digital images of the experimental setup for knife test (B),adhesive tape peeling test (D), sand paper abrasion test (F) respectively. (C, E, G)Digital images and contact angle images (inset) of the beaded water droplets afterperforming knife test (C), adhesive tape peeling test (E) and sand paper abrasiontest (G).Figures 5 (h)-(i) shows plots accounting the impact of practically relevant variousand challenging exposures of ambient (25°C) air, DI-water, artificial seawater, riverwater and UV irradiation (at λmax = 254 and 365 nm) for 300 days on the synthesizedsuperhydrophobic coating; and plot showing the change in static contact angle andcontact angle hysteresis of beaded water droplet on the superhydrophobic fabricafter conducting repetitive washing and ironing test (400 cycles) where insets arethe digital images of the superhydrophobic coating before and after ironing test inaccordance with the present invention.Figures 6(a)-(i) shows digital and static contact angle image ofAEAPTMS@ODAC coated different natural and synthetic fabric including jute(A), silk (B), cotton (C), wool (D), lycra (E), nonwoven fabric (F), polyurethane,(G) polyester (H). I-K) Digital and static contact angle image ofAEAPTMS@ODAC coated large scale substrate including T-shirt (I), melaminein accordance with the present invention.Figures 7(a)-(k) shows schematic representing the 1,4-conjugate addition reactionbetween amine group of [3-(2 Aminoethylamino)propyl]trimethoxysilane(AEAPTMS) and Octadecyl acrylate (ODAc). B) FTIR-ATR spectra of theOctadecylacrylate (black), [3-(2-Aminoethylamino)propyl]trimethoxysilane (blue)and coating solution after (red). In the FTIR-ATR spectra, the IR peak at 1735 cm-1, 1603 cm-1 and 1410 cm-1 are characteristic IR signatures for C=O stretching,primary N-H bending and C-H deformation of the β-carbon of the vinyl grouprespectively. C-F) Digital (C, E) and water contact angle images (D, F) of beadedwater droplets on the bare tissue paper (C, D) and superhydrophobic tissue paper(E, F). G) TEM image of Cu2O nanoparticles. H) HRTEM image confirms thesynthesis of Cu2O nanoparticles. I) XRD spectra of Cu2O nanoparticles. J-K)Digital (J) and water contact angle (K) image of Cu2O nanoparticles coatedsuperhydrophobic tissue paper in accordance with the present invention.Figures 8(a)-(g) shows digital images depicting the various physical manipulations,including creasing (A), twisting (B) and finger-wiping (E) on the coated(SHS@Cu2O) tissue paper. C-D) Digital image (C) and contact angle images (D)of the beaded water droplet on the coated (SHS@Cu2O) tissue paper after incurringseveral time creasing and twisting test. F) Digital image and contact angle images(inset) of the beaded water droplet on the coated (SHS@Cu2O) tissue paper afterincurring several time finger-wiping test. G) Plots accounting the impact ofpractically relevant various and challenging exposures of ambient (25°C) air, 80°C,DI-water and UV irradiation (at λmax = 254 and 365 nm) for 15 days on thesynthesized superhydrophobic coating in accordance with the present invention.Figures 9(a)-(f) shows digital and contact angle image (inset) of beaded waterdroplets on the bare (A, B, C) and coated (D, E, F) natural and synthetic fibroussubstrates including cotton (A,D), jute (B,E), nonwoven fabric (C,F) in accordancewith the present invention.Figures 10(a)-(b) shows cytotoxicity of Cu2O nanoparticle coated paper in BHK-21 cells using MTT assay. Plots depicting percentage cell viability after 2 hrstreatment with different coatings that loaded with increasing concentration of Cu2Onanoparticles in absence (A) and presence of (B) superhydrophobicity. In absenceof superhydrophobicity, the Cu2O nanoparticle based coating was found to behighly toxic and toxicity increased with increasing concentration of Cu2O. SameCu2O nanoparticle coatings in presence of superhydrophobicity showed high cellviabilityin accordance with the present invention.Figures 11(a)-(b) shows Plaque Reduction Assay for the antiviral study ofsuperhydrophobic paper coated with different concentration of Cu2O. Picturedepicting reduction in number of plaques with increasing concentration of Cu2Ocoating on the superhydrophobic paper; graph showing percentage virus reductionwith respect to virus control respectively in accordance with the present invention.DETAILED DESCRIPTION OF THE INVENTIONThe present invention now will be described hereinafter with reference to thedetailed description, in which some, but not all embodiments of the invention areindicated. Indeed, the invention may be embodied in many different forms andshould not be construed as limited to the embodiments set forth herein; rather,these embodiments are provided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout. The presentinvention is described fully herein with non-limiting embodiments and exemplaryexperimentation.The present invention provides a method of preparing a water repellent and antiviralcoating and a product thereof. More particularly, the present inventionprovides a method of preparing a water repellent and anti-viral coating on widerange of fibrous substrates which includes regular hydrophilic masks and tissuepapers which provides stability to the masks and prevents penetration of waterdroplets that carries infectious agents.In the preferred embodiment, a method of preparing a water repellent and anti-viralcoating on a fibrous substrate comprising steps of: (a) reacting 3-(2-Aminoethylamino) propyl trimethoxysilane (AEAPTMS) and octadecylacrylate(ODAc) in a desired ratio prepared in organic solvent to form a reaction mixture;(b) adding Cu2O nanoparticles to a desired molar concentration of said reactionmixture obtained in step (a) to obtain a spray deposition solution and furtherdepositing the spray deposition solution on the fibrous substrate to obtain a waterrepellent and anti-viral coating; wherein, said water repellent and anti-viral coatingis a Cu2O nanoparticle embedded superhydrophobic (SHS@Cu2O) coating; saidcoating has enhanced water wettability in range of 134° to 159°; said AEAPTMSand octadecylacrylate (ODAc) are reacted in desired ratio of 1:1; the spraydeposition solution obtained in step (b) of the reaction mixture yield said coating,where water droplets beaded with water contact angle (WCA) more than 150° andcontact angle hysteresis of less than 10°; said superhydrophobic (ODAC@AEAPTMS) coating is 99.2% optically transparent; said SHS@Cu2O coating isnon-toxic and has cell viability of above 95%; and said coating has antiviralproperty with 88% virus reduction.In another embodiment, the present invention a water repellent and anti-viralcoating on a fibrous substrate comprising of: a 3-(2-Aminoethylamino) propyltrimethoxysilane (AEAPTMS) and octadecylacrylate (ODAc) in a desired ratioprepared in organic solvent with Cu2O nanoparticles spray deposited on a fibroussubstrate; wherein, said coating has enhanced water wettability in range of 134° to159°; said coating has antiviral property with 88% virus reduction; said coating is99.2% optically transparent; said coating is non-toxic and has cell viability of above95%.In yet another embodiment, the present invention provides a disposable waterrepellent mask comprising of a superhydrophobic coating and a fibrous substrate;wherein, the superhydrophobic coating is a mixture of small molecule-basedreactants prepared in organic solvent and spray deposited on fibrous substrates. Thesmall molecule-based reactants include but is not limited to octadecyl acrylate andits fluorinated derivatives and 3-(2-Aminoethylamino) propyl trimethoxysilane).The fibrous substrates include but is not limited to polyurethane fabrics, cottonfabrics, regular hydrophilic mask and tissue papers. The organic solvents includebut are not limited to ethanol, acetone, toluene. The water repellent tissue mask inthe present invention provides stability and restricts penetration of water dropletsthat carries infectious agents and overcomes the drawback of disintegration onwater exposure in tissue papers.Since, Corona virus or any other infectious microbe mostly spreads throughmigration of water droplets from infected persons to non-infected people. Theextremely water repellent coating in the present invention ensures no penetrationof corona-virus contaminated aqueous droplets through the coated mask. Further,the water repellent tissue mask provides easy disposal of the used mask as thefibrous substrate that is tissue paper is biodegradable. Therefore, the presentinvention allows to prevent unwanted wetting of medially relevant substrate i.e.,crepe bandage.The present invention provides a rapid and single step process forsuperhydrophobic coating on fibrous substrate. Figure 1 shows the water repellenttissue mask and depiction of water repellent coating on different fibrous substrates.It shows digital images of beaded water droplets in air on the uncoated fibroussubstrate, water repellent tissue paper-based mask, polyurethane fabric and cottoncrepe bandage. It is observed that the water repellent coating prevents thedisintegration of tissue paper-based mask even after the exposures to aqueousphase.EXAMPLE 1"Small Molecules Derived Bio-inspired Coating"In the past, a facile and catalyst free 1,4-conjugate addition reaction betweenbranched poly(ethyleneimine) and dipentaerythritolpenta-acrylate has beenextended to develop various functional polymeric coatings mostly followingmultistep deposition processes. The present invention has further extended 1,4-conjugate addition reaction to develop chemically reactive and polymericnanocomplex (CRPNC) that is loaded with residual acrylate groups. The ageing ofthe solution of CRPNC for 3.5 hr led to formation of self-standing gel throughcovalent crosslinking between residual functional groups. Further selection ofexternal solvent and addition of salt accelerated the gelation of CRPNC dispersion.In the recent past, such CRPNC with short shelf-life was strategically extended toprepare chemically reactive polymeric coating, where choice of solvent andadditives played a crucial role on achieving stable coating. An additional andappropriate post covalent modifications of such chemically reactive coating withselected alkyl amines for overnight, yielded an optically translucentsuperhydrophobic coatings. Unlike previous reports, in this invention, the same1,4-conjugate addition reaction has been applied on rationally selected smallmolecules (used as reactants)-instead of the branched polymer-that derived fromhighly toxic aziridine. In the present invention, 1,4 conjugate addition reaction isrationally extended with commercially available and economically viable twosmall molecules-AEAPTMS and octadecylacrylate (ODAc) to achieve a reactionmixture with prolonged shelf-life (200 days) in wide range of organic solvents. Theselected reactants were mixed in the molar ratio of 1:1 in ethanol at ambientconditions, and as expected, amine groups of AEAPTMS spontaneously reactedwith the acrylate moiety of ODAc as characterized through standard Fouriertransform infrared attenuated total reflectance spectra (FTIR-ATR) analysis.During the 1,4-conjugate addition reaction between amine and acrylate groups, thevinyl moiety of ODAc is compromised, whereas the carbonyl moiety remainedunaffected at the end of the reaction. At time zero, the FTIR-ATR peaks at 1410cm-1 and 1730 cm-1 confirmed the existence of both C-H deformation of - carbonof vinyl group and carbonyl stretching in the reaction mixture respectively.However, as the reaction proceeds, the IR peak intensity at 1410 cm-1 depletedselectively and significantly with respect to the carbonyl stretching at 1730 cm-1 asshown in Figure 2(a). Moreover, the characteristic IR signature of the N-H bendingfor primary amine at 1601 cm-1 gradually decreased with increasing reaction time.After 10 minutes duration of the reaction mixture, the significant reduction of thecharacteristic IR signatures at 1410 cm-1 and 1601 cm-1 for both C-H stretching of -carbon of vinyl group and N-H bending of primary amine, respectively, validatedthe successful 1,4-conjugate addition reaction between two selected smallmolecules. Next, the reaction mixtures having different molar concentrations (10mM to 30 mM) were spray deposited on a polyurethane-based inherentlyhydrophilic fibrous substrate. On increasing the concentration of reaction mixtures,the spray deposited coating displayed enhanced water wettability (from 134° to159°) as shown in Figure 2(b). At the concentration of 30 mM of each of theselected reactants (AEAPTMS and ODAc), the deposition solution-I (denoted asDS-1) displayed superhydrophobicity with water contact angle of ~159°. Thegradual change in reaction concentration of spray deposited solution resulted inobvious alteration of topography on the selected featureless fibrous substrate asshown in Figures 2(c)-(f). A prominent granular domain with random sizesappeared uniformly on the fibrous substrate for the reaction mixture of smallmolecules having concentration of 30 mM as shown in Figure 2(f). The presenceof such topography is important for conferring superhydrophobicity. The reactionmixture of same reactants having same composition (1:1)-but with lowerconcentrations (below 30 mM) failed to provide extreme water repellency due tothe lack of appropriate topography as evident from the Figure 2(c) and Figure 2(d).The globular domains are less prominent once the concentration of the reactants inthe reaction mixtures is reduced to below 30 mM as shown in Figure 2(d) andFigure 2(e). Thus, the concentration of reactants in the reaction mixture played acrucial role in adopting essential topography that conferred superhydrophobicity.In the present invention, AEAPTMS is selected as binder, where the selfpolymerizationability during the solvent evaporation process as evident fromFTIR-ATR spectral study allowed to achieve durable coating. The appearance ofcharacteristic IR signature at 1028 cm-1 for Si-O-Si bridge confirmed thepolymerization process. However, the deposition of only AEAPTMS on theselected hydrophilic fibrous substrate failed to provide extreme water repellence,rather the water droplet beaded with water contact angle (WCA) of ~40°.Nevertheless, the appropriate association of 1,4-conjugate addition reaction withthe self-polymerization process allowed the single-step co-optimization of essentialtopography and appropriate chemistry for conferring desired superhydrophobicity.The characteristic IR signature at 1028 cm-1 for Si-O-Si bridge revalidated thesuccessful polymerization of the reaction mixture (blue) during the solventevaporationprocess. After ageing of reaction mixture for 10 minutes as shown inFigure 3(a), the spray deposition of the reaction mixture yielded an extremelywater-repellent coating, where water droplets beaded with WCA of ~159° asshown in Figure 3(c). Further, a water jet immediately bounced off from thesuperhydrophobic interface shown in Figure 3(e), irrespective of the incident angle.This result indicated the existence of non-adhesive and robustsuperhydrophobicity. The entrapment of external third phase-air, minimized theinteraction between the aqueous phase and the bio-inspired coating. Theunderwater shiny interface revealed the existence of external trapped air into thesmall molecules derived coating as shown in Figure 3(f), and as expected, suchshiny interface was not observed for the uncoated substrate. Further, thesynthesized superhydrophobic coating remained 99.2% optically transparent.Indian institute of technology, Guwahati logo printed T-shirt was successfully andselectively a s shown in left side of the dotted line in Figure 2(g) coated for a visualdemonstration of the optical transparency and water repellence of the synthesizedcoating.Thereafter, the same reaction mixture that was stored in ambient conditions for 200days was spray deposited as shown in Figure 3(b) and the coating displayedsuperhydrophobicity with WCA above 150° and roll off angle 6° as shown inFigures 3(d) to 3(j). Further, the reaction mixtures of AEAPTMS andoctadecylacrylate, which were prepared using various other volatile organicsolvents, including acetone, toluene, propanol, butanol, pentanol, hexanol andheptanol, remained capable of providing extremely water-repellent coating. Thespray deposition of the respective reaction mixture provided non-adhesivesuperhydrophobicity with static WCA above 150° and contact angle hysteresis ofbelow 10°, irrespective of the choice of organic solvents as shown in Table 1. Evenafter 200 days, the same reaction mixtures that were prepared in various organicsolvents remained capable of providing bio-inspired superhydrophobic coating asnoted in Table 1. The HPLC grade organic solvents were used to suppress thecrosslinking of the siloxane during the storage of reaction mixture for 200 days.Thus, various volatile organic solvents can be used as reaction medium forpreparing deposition solution that made of selected small molecules to achieve bioinspiredsuperhydrophobicity.Next, the adhesive interaction between the bio-inspired coating and beaded waterdroplet was modulated through rational selection of alkyl acrylates during thepreparation of reaction mixture as shown in Figure 4(a). The deposition solutionsobtained by individually mixing hexyl acrylate (HAc; 30 mM) anddodecylaacrylate (DDAc, 30 mM) with AEAPTMS (30 mM), denoted as DS-2 andDS-3. The mutual reaction between these two selected small molecules wereverified with standard ATR-FTIR analysis as shown in Figure 4(b). As expected,within 10 minutes, the catalyst-free 1,4 conjugate addition reaction between amineand acrylates in DS-2 (HAc and AEAPTMS) and DS-3 (DDAc and AEAPTMS)at ambient condition led to depletion of IR signatures for both amine (at 1410 cm-1) and vinyl (at 1601 cm-1) moieties, respectively, as shown in Figure 4(b). Theseparate spray deposition of the DS-2 and DS-3 provided an adhesivesuperhydrophobicity with different advancing (~159° and ~161°) and receding(~146° and ~150°) water contact angles as shown in Figures 4(c), 4(d), 4(f) and4(g). The adhesive forces between the beaded droplet and the superhydrophobiccoatings that were derived from DS-2 and DS-3 were found to be 204 N (red) and104 N (green), respectively. The superhydrophobic coating derived from DS-1(having ODAc) displayed a receding water contact angle of 158° as shown inFigure 4(h) and an adhesive force of 24 N as shown in Figure 4(i), blue). Thus,the adhesive force gradually decreased on association of higher analogues of HAcas shown in Figures 4(c)-(h). The appropriate selection of small molecule isimportant for tailoring both Cassie-Baxter and Cassie-Wenzel transitional states.Such tunable adhesive superhydrophobicity was also extended to demonstrate thecontrolled mixing and no-loss transfer of aqueous droplet mixing.Table 1Accounting the water wettability of beaded droplets on superhydrophobiccoatings that were prepared using different volatile organic solvents asreaction medium, where the respective reaction mixtures were spray depositedafter storing them for 10 minutes and 200 daysSolvent t = 10 minutes t = 200 daysθstatic (°) θhys (°) θstatic (°) θhys (°)Toluene 161.2 ± 0.6 3.9 ± 0.6 152.4 ± 1.5 5.9 ± 1.2Ethanol 159.8 ± 0.5 4.5 ± 0.5 151.9 ± 1.2 6.8 ± 1.3Propanol 158.8 ± 0.8 4.6 ± 0.7 152.5 ± 1.6 7.0 ± 1.1Butanol 159.5 ± 0.9 3.9 ± 1.1 151.5 ± 0.7 6.8 ± 0.9Pentanol 158.5 ± 1.1 4.0 ± 1.0 151.4 ± 0.9 6.5 ± 0.8Hexanol 160.2 ± 1.3 4.7 ± 0.7 150.8 ± 1.1 7.1 ± 1.7Heptanol 158.2 ± 0.8 4.6 ± 0.6 152.7 ± 1.4 6.6 ± 0.7EXAMPLE 2"Investigating the durability of synthesized Bio-inspired Coatings"To investigate the robustness of the synthesized non-adhesive superhydrophobiccoating, various standard and practically relevant abrasive tests were performed onthe freshly prepared bio-inspired coating. Firstly, the superhydrophobic coatingon the stretchable fibrous substrate was exposed to large physical deformation, andthe embedded superhydrophobicity remained capable of sustaining a tensiledeformation of 150% with static WCA of 156° and contact angle hysteresis ofbelow 10° as shown in Figure 5(a). The small molecules derived coating wasextended to repetitive tensile deformation (150%) for 3750 times. The embeddednon-adhesive superhydrophobicity remained intact till 2000 times. Further anydeformation of the coated substrate compromised the embeddedsuperhydrophobicity as shown in Figure 5(a). Next, the small molecules derivedsuperhydrophobic coating on the fibrous substrate was exposed to successive knifetest as shown in Figure 5(b), where the physical damages were clearly visible onthe synthesized bio-inspired interface. Nevertheless, the water droplets beaded onthe physically damaged interface with static WCA of ~156° shown in Figure 5(c).The as-synthesized superhydrophobic coating was then exposed to adhesive tapepeeling test, where a freshly exposed adhesive surface was placed on the bioinspiredcoating with an applied load of 66 kPa for 60 s before peeling of the appliedtape from the superhydrophobic interface as shown in Figure 5(d). Such adhesivetape peeling test was repeated for 350 times. The synthesized coating failed toperform only after repeating the adhesive tape peeling test above 250 cycles asshown in Figure 5(e). Thereafter, an abrasive sand paper was rubbed on thesynthesized superhydrophobic interface with an applied load of 66 kPa as shownin Figure 5(f), and the water wettability was investigated with increasing the sandpaperabrasion distance. The physically damaged as evident from Figure 5(g)coated substrate, which was continuously exposed to sandpaper abrasion,displayed extreme water repellency with a static WCA of ~153.2°. The synthesizedsuperhydrophobic coating remained capable of sustaining a sand paper abrasiondistance of 2250 cm without compromising the embedded extreme waterrepellence. Further, an increment of the abrasion distance led to compromise of thenon-adhesive superhydrophobicity. Again, the same reaction mixture of smallmolecules was deposited on a selected fibrous substrate following a dip-coatingprocess to compare the performance of the embedded superhydrophobicity withthe spray deposited coating. The dip-coated interface displayed non-adhesivesuperhydrophobicity with WCA of 159°. The performance of the dip coating atchallenging abrasive exposure observed to be very similar to the spray-coating ofsame reaction mixture. Thus, the process of depositing the reaction mixture hasminimal impact on the durability of the embedded superhydrophobicity. Further,the durability of the synthesized coating is compared with an earlier reported andpolymer derived superhydrophobic spray coating under the identical abrasiveconditions. The polymer derived spray coating that was prepared followingreported protocol can survive sandpaper abrasion distance of only 250 cm andadhesive tape peeling test for only 25 times under the applied load of 66 KPa. Thus,the small molecules derived coating provided a superior and exemplary durabilityin comparison to the earlier reported polymeric coating. The small moleculesderived superhydrophobic coating extremely repelled various and relevantchemically complex aqueous phases. The bio-inspired extreme water repellencesurvived prolonged (300 days) exposures to ambient air, DI-water, artificial seawater, river water and UV light, with static WCA above 150° and contact anglehysteresis below 10° as shown in Figure 5(h). This exemplary chemical durabilityof the coating is attributing to the strategic association of robust 1,4 conjugateaddition reaction. The synthesized superhydrophobic coating was also repetitively(400 times) washed with surfactant (SDS) added aqueous phase following astandard and reported procedure. Even after 250 times of washing, thesuperhydrophobicity remained intact with static WCA above 150° and contactangle hysteresis below 10° as shown in Figure 5(i). However, the embeddedsuperhydrophobicity compromised on further repetition of the washing cycle asshown in Figure 5(i). The synthesized superhydrophobic interface remainedrepellent to boiling water, tea and prolonged (30 days) exposure of hightemperature (80°C). The bio-inspired coating continued to perform even afterironing the interface at 180°C for 375 times as shown in Figure 5(i). During theprocess of ironing at 180°C, the creasing marks disappeared from the wrinkledsuperhydrophobic surface as shown in the inset image of Figure 5(i). The fluorinefreeand small molecules derived, optically transparent and highly tolerantsuperhydrophobic coating can be successfully applied on various natural andsynthetic hydrophilic substrates, including jute fabric, silk fabric, cotton fabric,woolen fabric, lycra fabric, non-woven fabric i.e. commercially available surgicalmask, polyurethane fabric and polyester fabric as shown in Figures 6(a)-(h). Dueto the inherent simplicity of the synthesis process, practically relevant differentlarge objects (e.g. cotton T-shirt, melamine sponge and cotton roll) can also beeasily decorated with extreme water repellence as shown in Figures 6(i)- (k).EXAMPLE 3"Synthesis of Water-repellent and Antiviral Coating"Next, the reaction mixture of AEAPTMS and octadecylacrylate (ODAc) wasdeposited on inherently hydrophilic tissue paper to achieve superhydrophobiccoating as shown in Figures 7(a)-(f).The standard Fourier Transform Infrared Attenuated Total Reflectance (FTIRATR)spectra confirmed the complete 1,4- conjugate addition reaction betweenacrylate group of octadecyl acrylate and primary amine group of AEAPTMS whereIR peak at 1410 cm-1 for C-H stretching of β carbon of vinyl group of octadecylacrylate and peak at 1601 cm-1 for N-H bending of primary amine of AEAPTMSwere depleted significantly as shown in Figure 7(b). The spray deposition ofcoating solution on inherently hydrophilic bare tissue paper provides the waterrepellent property with water contact angle above 150° as shown in Figures 7(c)-(f). Next, Cu2O nanoparticle was synthesized and characterized following somestandard procedure. The Transmission Electron Microscopy (TEM) and HighResolution Transmission Electron Microscopy (HRTEM) images confirmed thesuccessful preparation of Cu2O nanoparticles with a lattice spacing of 0.26 nmwhich corresponds to the (111) plane as shown in Figures 7(g) and 7(h). Inaddition, XRD spectra further confirmed the existence the planes of (110), (111),(200) (220) and (311) on 2θ position of 29.90, 36.94, 41.64, 61.76 and 74.47respectively as shown in Figure 7(i). Next, the Cu2O nanoparticle added depositionsolution was uniformly deposited to achieve superhydrophobic tissue paper. Thewater repellent property of the tissue paper was remained intact after association ofCu2O nanoparticle in the deposition solution as shown in Figures 7(j) and (k).Next, the durability of the Cu2O nanoparticle embedded superhydrophobic(denoted as SHS@Cu2O) tissue paper was investigated in details. Firstly, thesuperhydrophobic tissue paper was exposed to creasing, twisting and finger wipingfor multiple times, but water repellent property remained intact with a contact angleabove 150° as shown in Figures 8(a)-(f). Moreover, the anti-wetting propertysurvived prolonged (15 days) exposure to ambient air, DI-water, UV light and 80°Cwith static water contact angle above 150° as shown in Figure 8(g). Next, theSHS@Cu2O coating was successfully applied on the various substrate includingcotton fabric, jute fabric, polyurethane fabric, non-woven fabric i.e. commerciallyavailable surgical mask, as shown in Figures 9(a)-(f). These SHS@Cu2O coatedfabrics were highly durable and various standard and practically relevant abrasivetests were applied on the SHS@Cu2O coated polyurethane fabric to investigate thedurability. First, an abrasive sand paper was rubbed on the SHS@Cu2O coatedpolyurethane fabric with an applied load of 60 kPa for 50 cycles, but the sand paperabraded substrate displayed extreme water repellency with a static water contactangle above 150°. Next, the SHS@Cu2O coated polyurethane fabric was exposedto an adhesive tape peeling test, where a freshly exposed adhesive surface wasplaced on the fabric with an applied load of 60 kPa for 1 minute. But, after peelingthe tape, the anti-wetting property of the substrate remained intact. Moreover, theanti-wetting property of the synthesized fabric remained unperturbed even afterrandom scratching with a sharp knife.EXAMPLE 4"Investigating Cell Viability and Antiviral Performance of SHS@Cu2OCoating"Next, cell viability of the Cu2O nanoparticle embedded superhydrophobic coatingwas demonstrated by studying the standard MTT assay. In MTT assay, it wasfound that the Cu2O nanoparticle coated bare tissue papers were cytotoxic. Even alower amount of Cu2O (0.5 mg / ml) loaded tissue paper showed only 15% of cellviability, as shown in Figure 10(a). Whereas, after the association of samenanoparticle with superhydrophobicity (labelled as SHS@Cu2O coating), thecoated tissue paper became non-toxic and cell viability remained above 95%, evenin the case of high loading (3.0 mg / ml) of Cu2O, which indicate that the bio15inspired superhydrophobicity helped in reduction of cytotoxicity of embeddedCu2O as shown in Figure 10(b). Thereafter, the antiviral performance of the coatingwas studied with Avian Paramyxovirus (Newcastle disease virus). In the plaquereduction assay for antiviral study, it was found that the SHS@Cu2O has antiviralproperty and a maximum 88% virus reduction was achieved with a high amountof Cu2O loaded SHS@Cu2O mask (3 mg / ml) as shown in Figures 11(a) and 11(b).This is the highest loading concentration of metal oxide, where the synthesizedcoating remained superhydrophobic and highly cell-viable.Therefore, the present invention provides water repellent tissue mask which isstable and restricts penetration of water droplets that carry infectious agents, inaddition the water repellent tissue masks offer easy disposal as they arebiodegradable in nature.Many modifications and other embodiments of the invention set forth herein willreadily occur to one skilled in the art to which the invention pertain having thebenefit of the teachings presented in the foregoing descriptions and the associateddrawings. Therefore, it is to be understood that the invention is not to be limited tothe specific embodiments disclosed and that modifications and other embodimentsare intended to be included within the scope of the appended claims. Althoughspecific terms are employed herein, they are used in a generic and descriptive senseonly and not for purposes of limitation.

Claims

1. A method of preparing a water repellent and anti-viral coating on a fibrous substrate comprising steps of: (a) reacting 3-(2-Aminoethylamino) propyl trimethoxysilane (AEAPTMS) and octadecylacrylate (ODAc) in a desired ratio prepared in organic solvent to form a reaction mixture for achieving superhydrophobicity; (b) adding Cu2O nanoparticles to a desired molar concentration of said reaction mixture obtained in step (a) to obtain a spray deposition solution and further depositing the spray deposition solution on the fibrous substrate to obtain a water repellent and anti-viral coating; wherein, said water repellent and anti-viral coating is a Cu2O nanoparticle embedded superhydrophobic (SHS@Cu2O) coating; said coating has enhanced water wettability in range of 134° to 159°; said AEAPTMS and octadecylacrylate (ODAc) are reacted in desired ratio of 1:1; said reaction mixture is stable and active for upto 200 days and provides superhydrophobicity; the spray deposition solution obtained in step (b) of the reaction mixture yield said coating, where water droplets beaded with water contact angle (WCA) more than 150 and contact angle hysteresis of less than10; said coating is 99.2% optically transparent; said coating is non-toxic and has cell viability of above 95%; and said coating has antiviral property with 88% virus reduction.

2. The method as claimed in claim 1, wherein said fibrous substrate includes but is not limited to polyurethane fabrics, cotton fabrics, regular hydrophilic mask and tissue papers.

3. The method as claimed in claim 1, wherein desired molar concentration of said reaction mixture is in range of 10 mM to 30 mM.

4. The method as claimed in claim 1, wherein said coating is highly durable.

5. A water repellent and anti-viral coating on a fibrous substrate comprising of: a 3-(2-Aminoethylamino) propyl trimethoxysilane (AEAPTMS) and octadecylacrylate (ODAc) in a desired ratio prepared in organic solvent with Cu2O nanoparticles spray deposited on a fibrous substrate; wherein, said coating has water wettability in the range of 134° to 159°; and said coating has antiviral property with 88% virus reduction.

6. The coating as claimed in claim 5, wherein said coating is non-toxic and has cell viability of above 95%.

7. The coating as claimed in claim 5, wherein said coating is 99.2% optically transparent.

8. The coating as claimed in claim 5, wherein said coating is highly durable.

9. The coating as claimed in claim 5, wherein said fibrous substrate includes but is not limited to polyurethane fabrics, cotton fabrics, regular hydrophilic mask and tissue papers.