FIELD OF THE INVENTION

[0001] The present invention relates to an air filtration system, particularly an air filtration system having anti-viral and anti-bacterial air filter effective to viruses and bacteria such as coronaviruses and manufacturing method thereof. The present invention can be used with any devices, tools, equipment, articles and apparatus, which require(s) air filtration.

BACKGROUND OF THE INVENTION

[0002] It is known that coronavirus 2019 (COVID-19) has been widely spread. More and more coronavirus cases are confirmed in different countries. More and more people wear antiviral face mask to protect themselves from being infected. The demand for face masks with an effective anti- bacterial and anti-viral air filter is high in different countries. Known antiviral face masks can protect human beings from bacteria and virus but no experimental evidence indicates that the air filters of the known antiviral face masks are able to protect human beings from COVID-19 or the like.

[0003] In order to solve the above-mentioned problems, an object of the present invention is to provide an anti-bacterial and anti-viral air filtration system that is proved experimentally to be effective for protecting human cells from the attack of COVID-19 or the like and that can be successfully applied to a face mask.

SUMMARY OF THE INVENTION

[0004] Below various embodiments of the present invention are described to provide a modified antiviral face mask.

[0005] An air filtration system comprises one or more first layers, one or more second layers, and one or more third layers, wherein the one or more second layers are positioned between the one or more first layers and the one or more third layers, and each of the one or more first layers and the one or more third layers include a hydrophobic air-permeable composite and the one or more second layers include a polycationic anti- viral and anti-bacterial air-permeable composite. [0006] Preferably, the polycationic anti- viral and anti-bacterial air permeable composite includes an air-permeable substrate, an anti-viral agent and an anti-bacterial agent and a binding agent. The anti-viral agent includes one kind of polymers with polycationic characters. The one kind of polymers with polycationic characters includes polyethylenimine (PEI), poly-L- lysine (PLL), diethylaminoethyl-dextran (DEAE-dextran) or poly(amidoamine) (PAMAM) dendrimers.

[0007] Preferably, the air-permeable substrate includes a non-woven fabric or a non-woven cellulose fabric.

[0008] Preferably, the binding agent includes a thermoplastic elastomer.

[0009] Preferably, the anti-bacterial agent includes a silver nanowire.

[0010] Preferably, the hydrophobic air-permeable composite includes an air-permeable substrate, a hydrophobic binding agent and a photocatalytic reactivity component.

[0011] Preferably, the hydrophobic binding agent includes a synthetic polymer with hydrophobic characteristics.

[0012] Preferably, the photocatalytic reactivity component includes a titanium dioxide nanoparticle.

[0013] An antiviral face mask comprises an air filtration system, a pair of straps; and a wire, wherein one of the pair of straps is provided at each side of the air filtration system and the wire is provided inside the top of air filtration system.

BRIEF DESCRIPTIION OF THE DRAWINGS

[0014] Fig. 1 illustrates a cross-sectional view of an air filtration system in accordance with various embodiments of the present invention.

[0015] Fig. 2 illustrates an example of Silver Nanowire in accordance with various embodiments of the present invention.

[0016] Fig. 3 illustrates an example of an antiviral face mask having an air filtration system of Fig. 1 in accordance with various embodiments of the present invention.

[0017] Fig. 4 illustrates graphically differential pressure of air permeability (KPasm-1) of different fabric material in accordance with various embodiments of the present invention. S-N-S refers to PET-1 Fabrics coated by hydrophobic air-permeable layers (HALs); V-N-V refers to PET-2 Fabrics coated by HALs; RN refers to RN nonwoven cellulose coated by HALs; RS refers to RS nonwoven cellulose coated by HALs; RV refers to RV nonwoven cellulose coated by HALs; Meltblown-1 refers to fresh meltblown coated by HALs; and Meltblown-II refers to used meltblown coated by HALs.

[0018] Figs. 5A - 5B illustrate graphically viral filtration efficiency in accordance with various embodiments of the present invention. In Fig. 5A, the dotted line shows the FTIR spectra of Hydrolysed polycationic anti-viral and anti-bacteria air-permeable composite, whereas the solid line shows the spectra of pure fabric nonwoven KWL. Fig. 5B shows the FTIR spectrum of a polycationic anti-viral and anti-bacteria air-permeable composite.

[0019] Fig. 6 illustrates atomic force microscopy (AFM) images of a polycationic anti-viral and anti-bacteria air-permeable composite in accordance with various embodiments of the present invention. Part (a) of the figure shows the composite and cellulose, while part (b) shows layers of the composite (left: 20 x 20 pm, right: 5 x 5 pm). The topography images are presented such that brightness increases with height.

[0020] Figs. 7A - 7B illustrate graphically evolutions of (a) the normalized frequency changes fii/n and (b) the dissipation factor changes Dn for the third, fifth and seventh overtones, during adsorptions of polyethylenimine (PEI) at increasing concentrations onto regenerated fabric layer in accordance with various embodiments of the present invention.

[0021] Fig. 8 illustrates graphically variations of the hydrated adsorbed mass of PEI onto cellulose as a function of the PEI concentration as derived from the QCM-D data following the Sauerbrey equation in accordance with various embodiments of the present invention. The value of the determination coefficient is 0.999.

[0022] Fig. 9 illustrates graphically variations of (a) the normalized frequency changes fn!n and (b) the dissipation factor changes Dn for the third, fifth and seventh overtones, during the deposition of PEI onto fabric, and during the subsequent rinsing steps with NaCl solutions at various concentrations in accordance with various embodiments of the present invention.

[0023] Fig. 10 illustrates an AFM image of bacteriophages T4 (5 x 5 pm) deposited on top of silicon substrates from a suspension used further for immobilization tests on top of fabric-coated QCM-D sensors, in accordance with various embodiments of the present invention.

[0024] Fig. 11 illustrates graphically variations of the normalized frequency changes fii/n and the dissipation factor changes Dn for the third, fifth and seventh overtones, during the deposition of T4D bacteriophages onto (a) native fabric and onto (b) PEI-treated fabric in accordance with various embodiments of the present invention.

[0025] Fig. 12 illustrates graphically Variations of the deposit thickness upon T4D bacteriophages adsorption onto native and PEI-treated fabric, as derived from the QCM-D data shown in Fig. 11 respectively following the Voigt viscoelastic model with a typical organic film density of 1 g cm ³ , in accordance with various embodiments of the present invention.

[0026] Fig. 13 illustrates graphically Variations of bacterial fall counts from spraying 2250 Staphylococcus Aureus on testing fabrics in accordance with various embodiments of the present invention.

[0027] Fig. 14 illustrates an image of bacteria fall count after spraying 2250 Staphylococcus Aureus deposited on top of cellulose subtracted with 2% PEI in accordance with various embodiments of the present invention.

[0028] Fig. 15A is a flowchart of a process for preparing one or more multifunctional air- permeable layers (MALs) using one loading agent in accordance with various embodiments of the present invention.

[0029] Fig. 15B is a flowchart of the process of Fig. 15A using another loading agent in accordance with various embodiments of the present invention. [0030] Fig. 16A is a flowchart of an alternative process for preparing one or more multifunctional air-permeable layers (MALs) using one loading agent in accordance with various embodiments of the present invention.

[0031] Fig. 16B is a flowchart of the process of Fig. 16A using another loading agent in accordance with various embodiments of the present invention.

[0032] Fig. 17A is a flowchart of an alternative process for preparing one or more multifunctional air-permeable layers (MALs) using one loading agent in accordance with various embodiments of the present invention.

[0033] Fig. 17B is a flowchart of the process of Fig. 17A using another loading agent in accordance with various embodiments of the present invention.

[0034] Fig. 18A is an illustration of the multiarm polytelechelic compound of the present invention, with the multifunctional cationic end groups attached to the viral surface via a combined effect of electrostatic interaction, hydrogen-bond interaction, ion complexation, Van der Waals effects and chain entanglement.

[0035] Fig. 18B is an illustration of the multiarm polytelechelic components being directly dispersed on a target object with hydrophilic surfaces.

[0036] Fig. 18C is an illustration of the multiarm polytelechelic components dispersed on a hydrophobic surface, with the assistance of a coupling agent with amphiphilic groups.

[0037] Fig. 19 is another illustration of the multiarm polytelechelic compounds.

[0038] Fig. 20A is a different illustration of the multi-arm polytelechelic components with numerous reactive end groups being distributed over a surface evenly with the aid of a coupling agent.

[0039] Fig. 20B shows the multifunctional cationic end groups of the polytelechelic components leading to electrostatic interaction, hydrogen-bond interaction, ion complexation, Van der Waals effects and/or chain entanglement with the target object, which is a virus. [0040] Fig. 21 illustrates the high-density, homogeneous and evenly distribution of the polytelechelic compounds enabling constructive interference within dipole-dipole forces between multifunctional cationic end groups and protein structure inside viruses and bacteria.

[0041] Fig. 22 is an illustration of the electrostatic interaction via generation of electrostatic filed between positively charged surface and negative charged surface of virus.

[0042] Fig. 23 shows the experimental procedures for testing the affinity of materials coated with the polytelechelic compounds to viruses.

[0043] Fig. 24A is a graph of the remaining copies of the HCoV-229E viruses in the buffer after the test material was applied, incubated and centrifuged.

[0044] Fig. 24B is a graph of the remaining copies of the Coxsackievirus B6 in the buffer after the test material was applied, incubated and centrifuged.

DETAILED DESCRIPTION OF THE INVENTION

[0045] The following description is presented to enable a person of ordinary skill in the art to make and use the various embodiments. Descriptions of specific devices, techniques, and applications are provided only as examples. Various modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the present invention. Thus, the disclosed invention is not intended to be limited to the examples described herein and shown but is to be accorded the scope consistent with the claims.

[0046] Fig. 1 illustrates a cross-sectional view of an air filtration system / air filter in accordance with various embodiments of the present invention. Air filtration system 100 may comprise one, two, three or more layers. The present invention may be used with any devices, tools, equipment, articles and apparatus, which require(s) air filtration.

[0047] Air filtration system 100 may include one or more first layers 102, one or more second layer 104 and one or more third layers 106. In this embodiment, second layer 104 is positioned between first layer 102 and third layer 106. second layer 104 is also considered as an intermediate layer. First layer 102 and third layer 106 refer to hydrophobic air-permeable layers respectively. First layer 102 and third layer 106 are dedicated for repelling water and allowing air to pass through. The hydrophobic air-permeable layer includes a hydrophobic air-permeable composite. Second layer 104 refers to a multifunctional air-permeable layer which includes a polycationic anti-viral and anti-bacteria air-permeable composite.

[0048] In one example, the multifunctional air-permeable layer includes a polycationic anti viral and anti-bacteria air-permeable composite which is formed based on, including but not limited, an air-permeable substrate (for example a woven / woven cellulose, a knitted or a non- woven / non- woven cellulose fabric with hydrophilic properties), an anti-viral agent (for example one kind of polymers with polycationic characters such as polyethylenimine (PEI), poly-L-lysine (PLL), diethylaminoethyl-dextran (DEAE-dextran), and poly(amidoamine) (PAMAM) dendrimers), an anti-bacterial agent (such as a silver nanowire) and/or a binding agent (such as a thermoplastic elastomer) via a surface coating technique with the assistance of aqueous liquids. The binding agent is adapted to decrease the pore size of the air-permeable substrate and the anti viral agent (such as PEI) with the air-permeable substrate tightly. In the present invention, the air- permeable substrate is the non- woven / non-woven cellulose fabric and the anti-viral agent is polyethylenimine (PEI). The multifunctional air-permeable layer (second layer 104) is dedicated for trapping and/or filtering airborne bacteria and virus (particularly COVID-19).

[0049] The hydrophobic air-permeable layer includes a hydrophobic air-permeable composite which is formed based on, including but not limited, an air-permeable substrate (such as a woven / woven cellulose, a knitted or a non-woven / non-woven cellulose fabric with hydrophobic properties), a binding agent with hydrophobic properties /a hydrophobic binding agent (such as a synthetic polymer with hydrophobic characteristics, for instance, a silicon- containing polymer, a fluorinated polymer and a polyolefin) and/or a component with photocatalytic reactivity / a photocatalytic reactivity component (such as a titanium dioxide nanoparticle) via a surface coating technique with the assistance of liquids. In the present invention, the air-permeable substrate is the non-woven / non-woven cellulose fabric. The hydrophobic air-permeable layer (first layer 102 and third layer 106) are allowing to air to pass through.

[0050] It is known that the surface coating technique can introduce coating materials (such as the binding agent, anti-viral agent and anti-bacterial agent ) contouring to the fiber surface of the non-woven fabric (the air-permeable substrate), which can decrease the pore size of the non- woven fabric but maintain its unique texture (structure) and inherent properties (i.e. flexibility and permeability), and can also introduce new functions/properties of coating materials with significant decrease of usage amount.

[0051] A kind of polymers with polycationic characters such as polyethylenimine (PEI) may act as an active agent for particulate, viral and bacterial filtration or may act as an anti-viral agent.

Polyethylenimine

(PEI)

[0052] A growth of a kind of polymers with polycationic characters such as polyethylenimine (PEI), increases successively of an aminalized solution. The adsorption of T4D bacteriophages, which stands for Virus Filtration Efficiency (VFE) are 15-fold more efficient onto the fabric by coating with a kind of polymers with polycationic characters such as polyethylenimine (PEI). The adsorption of Staphylococcus Aureus, which stands for Bacterial Filtration Efficiency (BFE) are 25 -fold more efficient onto the fabric by coating with a kind of polymers with polycationic characters such as polyethylenimine (PEI). Coating with a kind of polymers with polycationic characters such as polyethylenimine (PEI) highly improves the airborne virus and bacteria affinity.

[0053] The fabric can be an air-permeable substrate (, that may comprise a fibrous substrate, which can either be a woven or non-woven material. Examples of woven materials include those natural and synthetic fibers such as cotton, cellulose, wool, polyolefins, polyester, polyamide (e.g.nylon), rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls and any other synthetic polymers that can be processed into fibers. Examples of non-woven materials include polypropylene, polyethylene, polyester, nylon, PET and PLA.

[0054] In one embodiment, the non-woven is used in this invention. Such a material may be in the form of a non-woven sheet or pad. Preferably, a non-woven polyester is used as an air- permeable substrate because it is found that the aminalized coating with a kind of polymers with polycationic characters such as polyethylenimine (PEI) of the types described herein adhere better to polyester material. There appears to be less tendency for the aminalized coating with a kind of polymers with polycationic characters such as polyethylenimine (PEI) to visibly flake or rub off a polyester substrate. Polyester fibers and fabrics made therefrom are well known. The term "polyester" as used herein is a generic name for a manufactured fiber being a polymer with units linked by ester groups. A common polyester used for woven and non-woven fiber manufacture is polyethylene terephthalate.

[0055] It is known that a face mask has an intermediate layer as an air filter which is adapted to trap and neutralize virus and bacteria. The intermediate layer is made meltblown materials which trap virus and bacteria by electrostatic attraction force. Electrostatic attraction force will be discharged successively after encounter saliva vapour from user’ s mouth, with the result that the meltblown materials will lose most of the electrostatic attraction force and Bacterial Filtration Efficiency (BFE) and Viral Filtration Efficiency (VFE) will decrease significant after several hours of use of the face mask

[0056] In this invention, second layer 104 is the multifunctional air-permeable layer, which includes the polycationic anti-viral and anti-bacteria air-permeable composite. One of the benefits is that trapping and neutralizing bacteria and virus remain substantially stable upon large variations of ionic strength. The capture of bacteriophages is 15 fold more efficient when the cellulose surface is treated with a kind of polymers with polycationic characters such as polyethylenimine (PEI). The affinity between bacteria and virus and a kind of polymers with polycationic characters such as polyethylenimine (PEI) is due to strong electrostatic attractive interactions between polycationic a kind of polymers with polycationic characters such as polyethylenimine (PEI) and negatively charged viruses. And the attractive interactions will grow stronger along with increasing humidity, as electricity conductivity within fabric structure will increase. The non-woven fabric coated by PEI supports as a filter for confined spaces air purifiers (airplanes, boats, offices, hospitals), antiviral masks, surface cleaning wipes, or protective clothing.

[0057] One of the benefits is the production cost being reduced. PEI presents in two kinds of physical structure. A linear structure of PEI is solid form in room temperature. It is easy to coat on fabric structure, but the cost is up to USD 1000 per gram. Branched structure of PEI is liquid form in room temperature, and it is not soluble to fabric materials, but the cost is USD 17.96 per kilogram.

[0058] By modifying industrial processes and applying proper chemical loading vehicle, PEI is successfully laminated in branched structure in fabric surface, and production cost of a polycationic anti-viral and anti-bacteria air-permeable composite can be reduced 99.998204%, which make the polycationic anti-viral and anti-bacteria air-permeable composite commercially feasible in production.

[0059] In another embodiment of the present invention, the polycationic anti-viral and anti bacteria composite of the second layer 104 is further modified with a multiarm polytelechelic compound, such as oligomers, polymers and/or particles, containing high-density multifunctional cationic end groups that have strong affinity with viral surfaces via a combined effect of electrostatic forces, hydrogen bonding, Van der Waals forces and chain entanglement.

[0060] The multiarm polytelechelic components can be directly dispersed on a target object with hydrophilic surface tightly, homogeneously and evenly via electrostatic interaction, hydrogen- bond interaction and/or ion complexation with some of the multifunctional cationic end groups.

[0061] When the polytelechelic components are coated onto a material, it can also be dispersed on its surface tightly, homogeneously and evenly with or without the assistance of a coupling agent that has amphiphilic groups. In the presence of such coupling agent, the polytelechelic components can link tightly with the reactive end groups of “polytechnic” components via electrostatic interaction, hydrogen-bond interaction and/or ion complexation. In the absence of the coupling agent, they can attach on the target surface directly via chemical bond, ion bond, hydrogen bond and/or Van der Waals forces.

[0062] The structure of the polytelechelic compounds of the present invention can comprise hyperbranched, star or brush-like oligomers and polymers, or oligomers and polymers-modified nanoparticles. On the other hand, alkylation of the polycationic groups also allows them to distribute over the material surface evenly. Such even and durable distribution of polycationic groups leaves insufficient space for small size viruses and bacteria to attach and survive over the modified surface. The multifunctional cationic end groups can also lead to effect of electrostatic forces, hydrogen-bond interaction, ion complexation, Van der Waals forces and/or chain entanglement with the viruses and bacteria. Such high-density, homogeneous and evenly distribution can further enable constructive interference within dipole-dipole forces between multifunctional cationic end groups and protein structure inside viruses and bacteria, capturing and destroying the viruses and bacteria efficiently and effectively.

[0063] In one embodiment, the number of arms in the polytelechelic compounds exceeds 14. In one embodiment, the density of the multifunctional cationic end groups is greater than 1.37xl0 ²² g ¹ ·

[0064] In one embodiment, the method for preparing a material with the multiarm polytelechelic compound dispersed comprises the following steps: (a) dissolving (i) at least one kind of cationic polymers; and (ii) ammonium polyphosphates (APP) in water to prepare an aqueous solution ; (b) spraying the solution onto the material, or dipping the material into the solution; and (c) removing the water from the material. After removal of water, the solids left on the fabric or fiber surface shall be between 0.5 and 100 g/m ² .

[0065] In another embodiment, the aqueous solution of step (a) further comprises (iii) a quaternary ammonium salt; and (iv) a nonionic hydrophilic polymer. [0066] In one embodiment, the dissolving step takes place under a temperature between 250°C and 350°C. In one embodiment, the dissolving step takes place under a pressure between 5Pa andlOPa. In one embodiment, the resulting aqueous solution has a total mass fraction of N greater than 25 wt.%. In another embodiment, the resulting aqueous solution has a total mass fraction of N between 10 wt.% and 35 wt.%.

[0067] In one embodiment, the cationic polymer is selected from a group consisting of branched/linear polyethylenimine (PEI), Chitosan and Polylysine. In one embodiment, the quaternary ammonium salt is selected from a group consisting of Poly(diallyldimethylammonium chloride) (PDADMAC) and Quaternized Hydroxyethylcellulose ethoxylate. In one embodiment, the nonionic hydrophilic polymer is selected from a group consisting of Polyacrylamide (PAM), Poly(N-isopropylacrylamide) and Polyethylene glycol.

[0068] In one embodiment, the aqueous solution comprises 10% to 80% by weight of said at least one kind of cationic polymers, and 20% to 90% by weight of said ammonium polyphosphates. In another embodiment, the aqueous solution comprises 6.5 portions of PEI, 3.0 portions of PDADMAC, 1.0 portions of PAM, 0.5 portions of APP and 490 portions of water by weight.

[0069]

MATERIAL USED

[0070] the multifunctional air-permeable layer includes a polycationic anti-viral and anti bacteria air-permeable composite which is formed based on, including but not limited an air- permeable substrate (for example a woven, knitted or non-woven fabric with hydrophilic properties), an anti- viral agent (for example one kind of polymers with polycationic characters such as polyethylenimine (PEI), poly-L-lysine (PLL), diethylaminoethyl-dextran (DEAE- dextran), and poly(amidoamine) (PAMAM) dendrimers), an anti-bacterial agent (such as a silver nanowire) and/or a binding agent (such as a thermoplastic elastomer) via a surface coating technique with the assistance of aqueous liquids. The binding agent is adapted to decrease the pore size of the air- permeable substrate and the anti-viral agent (such as PEI) with the air- permeable substrate tightly. polystyrene polybutadiene

Rigid end block Rubber mid block Rigid end block

Thermoplast Elastomers

[0071] As used herein the term "a kind of polymers with polycationic characters such as polyethylenimine (PEI)" includes a polymer having polyethylenimine groups along its backbone, e.g. as side groups. Suitable groups are polyethylenimine groups. The fabric coated by, a kind of polymers with polycationic characters such as polyethylenimine (PEI), may be branched or linear. Generally, for the present application branched, e.g. branched polymers are preferred. This is inter alia because relative to branched structure can provide more available amino groups, and also branched polymers are easier to dissolve and consequently to use in the preparative process disclosed herein.

[0072] Polyethylenimine (PEI) is a polymer with repeating unit composed of the amine group and two carbon aliphatic CH2CH2 spacer. Linear polyethyleneimines contain all secondary amines, in contrast to branched PEIs which contain primary, secondary and tertiary amino groups. PEI is produced on industrial scale and finds many applications usually derived from its polycationic character.

Linear Polyethylenimine (PEI)

[0073] Branched Polyethylenimine can be synthesized by the ring opening polymerization of aziridine. Depending on the reaction conditions different degree of branching can be achieved. Linear PEI is available by post-modification of other polymers like poly(2-oxazolines) or N- substituted polyaziridines. Linear Polyethylenimine was synthesised by the hydrolysis of poly(2- ethyl-2-oxazoline) and sold as jetPEI. The current generation in-vivo-jetPEI uses bespoke poly(2- ethyl-2-oxazoline) polymers as precursors.

Branched Polyethylenimine (PEI)

[0074] For example, the filter material may incorporate one or more surfactant. A surfactant can facilitate wetting of the filter material. Airborne pathogens such as virus are known to be carried in small droplets of water, and consequently enhanced wetting of the filter material can enhance the effective contact between the pathogen and the active materials on the filter material. Furthermore, surfactants are known to be effective in disrupting the membranes of virus and bacteria. Non-ionic surfactants are preferred because ionic surfactants can tend to cause the aminalized coating, especially of the polyethylenimine (PEI) to gel. A preferred non-ionic surfactant is selected. [0075] Although in general a high loading of a kind of polymers with polycationic characters such as polyethylenimine (PEI) on the substrate is desirable to achieve high effectiveness against pathogens, it is found that this should be balanced against the disadvantage that too high a loading can result in blockage of the passage of air through the filter material.

[0076] To achieve a suitable amount of immobilization of viruses in air passing through air filtration system 100, combined with permeability of a suitable rate of air, the total loading of a kind of polymers with polycationic characters such as polyethylenimine (PEI) if present and plus any surfactant if any on the substrate of the filter material is preferably in the range 20 - 50 g/m2, particularly 25 - 45 g/m2.

[0077] For substrates of the typical weights per square metre discussed herein this can correspond to total loading of a kind of polymers with polycationic characters such as polyethylenimine (PEI) if present and plus any surfactant if any on the substrate of the filter material, (based on the substrate itself of a starting 100% weight) of 5 - 60 wt %, typically 10 - 30 wt %.

[0078] For example, the filter material may incorporate one or more metal salt, for example selected from salts of silver, zinc, iron, copper, tin and mixtures thereof. Such salts may have antibacterial activity. These may be inorganic salts such as those of mineral acids such as chloride, nitrate or sulphate, or organic salts. An example of a metal salt of this type is zinc chloride.

[0079] For example, the filter material may incorporate one or more antimicrobial compound. Suitable examples of such compounds include quaternary ammonium compounds (e.g. benzalkonium chloride, cetrimide), phenolic compounds (e.g. triclosan, benzoic acid) biguanides (e.g. chlorhexidine, alexidine) and mixtures thereof.

[0080] An overall preferred filter material comprises a branched polyethylenimine (PEI), in its structure, together with a non-ionic surfactant, deposited on a non-woven polyester fibrous substrate, in the proportions described herein.

[0081] One particular type of such a filter material comprises a fibrous substrate (as discussed above) on which is deposited the aminalized coating, especially of the PEI. The filter material described herein may be made in various ways, in which the air-permeable substrate is combined with the aminalized coating, especially of the PEI.

[0082] In one way, PEI may be deposited on the air-permeable substrate as a complete or partial film on the substrate material, e.g. on fibers thereof. In another way, PEI may be incorporated into the material of the air-permeable substrate, e.g. into fibers thereof. This may be done during the fiber-forming process, e.g. spun bond and melt blown to form non-woven materials.

[0083] In another way, filter materials of the present invention may be made by known electrospinning processes, in which an electrified liquid jet of a polymer, in the form of a solution or melt is formed, and is deposited on a grounded collector fiber.

[0084] The hydrophobic air-permeable layer includes a hydrophobic air-permeable composite which is formed based on, including but not limited, an air-permeable substrate (such as a woven, knitted or non-woven fabric with hydrophobic properties), a binding agent with hydrophobic properties /a hydrophobic binding agent (such as a synthetic polymer with hydrophobic characteristics, for instance, a silicon-containing polymer, a fluorinated polymer and a polyolefin) and/or a component with photocatalytic reactivity / a photocatalytic reactivity component (such as a titanium dioxide nanoparticle) via a surface coating technique with the assistance of liquids.

[0085] The air-permeable substrate may comprise a fibrous substrate, which can either be a woven or non-woven material. Examples of woven materials include those natural and synthetic fibers such as cotton, cellulose, wool, polyolefins, polyester, polyamide (e.g. nylon), rayon, polyacrylonitrile, cellulose acetate, polystyrene, polyvinyls and any other synthetic polymers that can be processed into fibers. Examples of non-woven materials include polypropylene, polyethylene, polyester, nylon, PET and PLA. For this invention, non-woven is preferred. Such a material may be in the form of a non-woven sheet or pad. Non-woven polyester is a preferred air- permeable substrate because it is found that the aminalized coating, especially of the polyethylenimine (PEI) of the types described herein adhere better to polyester material. There appears to be less tendency for the aminalized coating, especially of the polyethylenimine (PEI) to visibly flake or rub off a polyester substrate. Polyester fibers and fabrics made therefrom are well known. The term "polyester" as used herein is a generic name for a manufactured fiber being a polymer with units linked by ester groups. A common polyester used for woven and non- woven fiber manufacture is polyethylene terephthalate.

[0086] The grade of fibrous substrate which may be used may be determined by practice to achieve a suitable through- flow of air, and the density may be as known from the face-mask art to provide a mask of a comfortable weight.

[0087] Typical non-woven polypropylene materials found suitable for use in this invention have weights 10 - 40 g/m2, although other suitable material wights can be determined empirically.

[0088] Typical non-woven polyester materials found suitable for use in this invention have weights 10 - 200 g/m2 , although materials toward the upper end of this range maybe rather heavy for use in a face mask. For example materials of weight 20 - 100 g/m2 are preferred, e.g. ca. 60 g/m2 . Such materials are commercially available. Other suitable materials can be determined empirically.

[0089] Alternatively the air-permeable substrate may be in other forms such as an open-cell foam, e.g. a polyurethane foam as is also used for air filters, for example as in nasal air plugs. It has been found that the aminalized coating, especially of the polyethylenimine (PEI) is effective at capturing and neutralising virus and bacteria in air passing through such a material. Without being limited to a specific theory of action it is believed that upon contact with the surface of the substrate the virus interact with the polymer, are entrapped and immobilized by polyethylenimine (PEI), inactivates the virus to thereby neutralise them. It is believed that the filter material of this invention may be effective in this manner against the virus that cause colds, influenza, SARS, RSV, bird flu, COVID-19 and mutated serotypes of these.

MANUFACTURING METHOD

[0090] Two kinds of air-permeable substrates with suitable thickness, porosity and surface wettability were selected for the fabrication of a multifunctional air-permeable layer (MAL) i.e. second layer 104 and hydrophobic air-permeable layers HALs i.e. first layer 102 and third layer 106 respectively.

[0091] Turning to now Fig. 15 A, an example process 1500A for preparing one or more multifunctional air-permeable layers (MALs). In some examples, process 1500A is implemented at a washing machine. As shown in Fig 15 A, at Step 1501, process 1500A includes soaking and stirring a non- woven fabric in a kind of solvent with a loading vehicle in a container for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature in order to optimize affinity between a kind of polymers with polycationic characters such as polyethylenimine (PEI) and the non-woven fabric. For example, the loading vehicle is a Carboxymethyl Group

R = H or CH ₂ Q0 ₂ H

Carboxymethyl Group

[0092] The Carboxymethyl Group is adapted to be bound to some of the hydroxyl groups of the glucopyranose monomers that make up a cellulose backbone such as Carboxymethyl Cellulose (CMC) or Cellulose Gum or Sodium Carboxymethyl Cellulose or Tylose or SE Tylose with concentration falling within a range Of 0.1% to 2%, preferably 0.5%.

[0093] At Step 1502, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0094] At Step 1503, the non-woven fabric is re-soaked and stirred in a solvent with a kind of polymers with polycationic characters such as polyethylenimine (PEI), with concentration falling within a range of 0.1% to 10%, preferably 2%, for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature, in order to optimize affinity between virus and/or bacteria and the non-woven fabric (optimize trapping and blocking the virus and/or bacteria).

[0095] At Step 1504, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0096] Alternatively, as shown in Fig. 15B, at Step 1505, process 1500B includes soaking and stirring a non-woven fabric in a kind of solvent with another loading vehicle in a container for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature in order to optimize affinity between a kind of polymers with polycationic characters such as polyethylenimine (PEI) and the non-woven fabric. The loading vehicle is Alginic Acid:

Alginic Acid

[0097] The solvent includes a linear copolymer with homopolymeric blocks of (l-4)-linked b- D-mannuronate (M) and its C-5 epimer a-L-guluronate (G) residues respectively, covalently linked together in different sequences or blocks, which monomers may appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks) or alternating M and G-residues (MG-blocks) such as Alginic Acid or Algin or Alginates, with concentration falling within a range Of 0.1% to 2%, preferably 0.5%.

[0098] At Step 1506, the non- woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0099] At Step 1507, the non-woven fabric is re-soaked and stirred in a solvent with a kind of polymers with poly cationic characters such as polyethylenimine (PEI), with concentration falling within a range of 0.1% to 10%, preferably 2%, for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature, in order to optimize affinity between virus and/or bacteria and the non-woven fabric (optimize trapping and blocking the virus and/or bacteria).

[0100] At Step 1508, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0101] Merely by way of examples, an alternative process 1600A to prepare one or more multifunctional air-permeable layers (MALs) is illustrated in Fig. 16A. In some examples, process 1700A is implemented at a spraying machine. As shown in Fig 16A, at Step 1601, process 1600A includes spraying a non-woven fabric with a kind of solvent with Carboxymethyl Group (-CH2- COOH) for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature in order to optimize affinity between a kind of polymers with polycationic characters such as polyethylenimine (PEI) and the non-woven fabric. The Carboxymethyl Group is adapted to be bound to some of the hydroxyl groups of the glucopyranose monomers that make up a cellulose backbone such as Carboxymethyl Cellulose (CMC) or Cellulose Gum or Sodium Carboxymethyl Cellulose or Tylose or SE Tylose with concentration falling within a range Of 0.1% to 2%, preferably 0.5%.

[0102] At Step 1602, the non-woven is sprayed with a solvent with a kind of polymers with polycationic characters such as polyethylenimine (PEI), with concentration falling within a range of 0.1% to 10%, preferably 2%, for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature, in order to optimize affinity between virus and/or bacteria and the non-woven fabric (optimize trapping and blocking the virus and/or bacteria). [0103] At Step 1603, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0104] Alternatively, as shown in Fig. 16B, at Step 1604, process 1600B includes spraying a non-woven fabric with a kind of solvent with another loading vehicle for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature in order to optimize affinity between a kind of polymers with polycationic characters such as polyethylenimine (PEI) and the fabric. The solvent is same as Fig. 16B and the loading vehicle is Alginic Acid with concentration falling within a range Of 0.1% to 2%, preferably 0.5%.

[0105] At Step 1605, the non-woven is sprayed with a solvent with a kind of polymers with polycationic characters such as polyethylenimine (PEI), with concentration falling within a range of 0.1% to 10%, preferably 2%, for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature, in order to optimize affinity between virus and/or bacteria and the non-woven fabric (optimize trapping and blocking the virus and/or bacteria).

[0106] At Step 1606, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0107] Merely by way of examples, an alternative process 1700A to prepare one or more multifunctional air-permeable layers (MALs) is illustrated in Fig. 17A. In some examples, process 1800A is implemented at a printing machine. As shown in Fig 17A, at Step 1701, process 1700A includes printing a non-woven fabric with a kind of solvent with Carboxymethyl Group (-CH2- COOH) for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature in order to optimize affinity between a kind of polymers with polycationic characters such as polyethylenimine (PEI) and the non-woven fabric. The Carboxymethyl Group is adapted to be bound to some of the hydroxyl groups of the glucopyranose monomers that make up a cellulose backbone such as Carboxymethyl Cellulose (CMC) or Cellulose Gum or Sodium Carboxymethyl Cellulose or Tylose or SE Tylose with concentration falling within a range Of 0.1% to 2%, preferably 0.5%.

[0108] At Step 1702, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0109] At Step 1703, the non-woven fabric is re-soaked and stirred in a solvent with a kind of polymers with poly cationic characters such as polyethylenimine (PEI), with concentration falling within a range of 0.1% to 10% , preferably 2%, for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature, in order to optimize affinity between virus and/or bacteria and the non-woven fabric (optimize trapping and blocking the virus and/or bacteria).

[0110] At Step 1704, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0111] Alternatively, as shown in Fig. 17B, at Step 1705, process 1700B includes printing a non- woven fabric with a kind of solvent with another loading vehicle for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature in order to optimize affinity between a kind of polymers with polycationic characters such as polyethylenimine (PEI) and the non-woven fabric. The solvent is same as Fig. 16B and the loading vehicle is Alginic Acid with concentration falling within a range Of 0.1% to 2%, preferably 0.5%.

[0112] At Step 1706, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0113] At Step 1707, the non-woven fabric is re-soaked and stirred in a solvent with a kind of polymers with polycationic characters such as polyethylenimine (PEI), with concentration falling within a range of 0.1% to 10%, preferably 2%, for a time period falling within a range of 20 seconds to 180 seconds, preferably 60 seconds, at room temperature, in order to optimize affinity between virus and/or bacteria and the non-woven fabric (optimize trapping and blocking the virus and/or bacteria).

[0114] At Step 1708, the non-woven fabric is dried, at temperature falling within a range of a range of 40°C to 90°C, preferably 70°C, for a time period falling within a range of 2 minutes to 12 minutes, preferably 10 minutes.

[0115] For hydrophobic air-permeable layers (HALs), they can be produced by one of the known process. For example, the known process includes web formation and web consolidation. The web formation includes carding, air laying, wet laying, spun-bonding, melt-blowing and electro spinning.

[0116] Air filtration system 100 is formed by sandwiching a MAL (second layer) with two HALs (first layer and third layer) through one of known lamination methods such as ultrasonic welding, hot-press lamination and cold-press lamination.

[0117] The present invention provides an air filtration system. In one embodiment, said air filtration system comprises: one or more first layers; one or more second layers; and one or more third layers; wherein the one or more second layers are positioned between the one or more first layers and the one or more third layers, and each of the one or more first layers and the one or more third layers include a hydrophobic air-permeable composite and the one or more second layers include a polycationic anti- viral and anti-bacterial air-permeable composite.

[0118] In one embodiment, the one or more second layer comprises: (a) a matrix of hollow hydrophilic fibers; and (b) a coating obtained by drying of a solution, said solution comprises: (i) a polycationic polymer; (ii) a quaternary ammonium salt; (iii) a nonionic hydrophilic polymer; and (iv) ammonium polyphosphate; wherein said coating comprises > 1.37 x 10 ²² g ¹ cationic group, a dry mass of >2g/m ² and a total mass fraction of N >25 wt.%.

[0119] In one embodiment, the air filtration system comprises one or more of the followings: (a) said polycationic polymer is selected from the group consisting of branched/linear polyethyleneimine, chitosan, poly-L-lysine and poly-D-lysine; (b) said quaternary ammonium salt is Poly(diallyldimethylammonium chloride) or Quaternized Hydroxyethylcellulose ethoxylate; or (c) said nonionic hydrophilic polymer is selected from the group consisting of Polyacrylamide, Poly(N-isopropylacrylamide) and Poly(ethylene glycol).

[0120] In one embodiment, the solution is a 2wt% solution comprising 31.8% of polyethyleneimine, 8.7% of Poly (diallyldimethylammonium chloride), 19.7% of Polyacrylamide, 13.1% of ammonium polyphosphate.

[0121] In one embodiment, the mass fraction of N is 26.56 wt%.

[0122] In one embodiment, polycationic polymer is a multiarm polytelechelic polymer comprising >14 arms.

[0123] In one embodiment, the matrix of hollow hydrophilic fibers comprises cotton or cellulose.

[0124] In one embodiment, the pressure drop across said one or more second layer at physiological respiratory flow rates is 0.5 to 10 Pa while having a VFE >99.9%.

[0125] In one embodiment, the polycationic anti- viral and anti-bacterial air permeable composite includes an air-permeable substrate, an anti-viral agent and an anti- bacterial agent and a binding agent.

[0126] In one embodiment, the anti-viral agent includes one kind of polymers with polycationic characters.

[0127] In one embodiment, the one kind of polymers with polycationic characters includes polyethylenimine (PEI), poly-L-lysine (PLL), diethylaminoethyl-dextran (DEAE-dextran) or poly(amidoamine) (PAMAM) dendrimers.

[0128] In one embodiment, the air-permeable substrate includes a non- woven fabric or a non- woven cellulose fabric.

[0129] In one embodiment, the binding agent includes a thermoplastic elastomer.

[0130] In one embodiment, the anti-bacterial agent includes a silver nanowire. [0131] In one embodiment, the hydrophobic air-permeable composite includes an air-permeable substrate, a hydrophobic binding agent and a photocatalytic reactivity component.

[0132] In one embodiment, the hydrophobic binding agent includes a synthetic polymer with hydrophobic characteristics.

[0133] In one embodiment, the photocatalytic reactivity component includes a titanium dioxide nanoparticle.

[0134] The present invention also provides an antiviral face mask. In one embodiment, said antiviral face mask comprises (a) the air filtration system of an embodiment of the invention; (b) a pair of straps; and (c) a wire; wherein one of the pair of straps is provided at each side of the air filtration system and the wire is provided inside the top of air filtration system.

[0135] The present invention further provides a coating obtained by drying of a solution. In one embodiment, said solution comprises: (a) a polycationic polymer; (b) a quaternary ammonium salt; (c) a nonionic hydrophilic polymer; and (d) ammonium polyphosphate; wherein said coating comprises > 1.37 x 10 ²² g ¹ cationic group, a dry mass >2g/m ² and a total mass fraction of N >25 wt.%.

[0136] In one embodiment, the coating comprises one or more of the followings: (a) said polycationic polymer is selected from the group consisting of branched/linear polyethyleneimine, chitosan, poly-L-lysine and poly-D-lysine; (b) said quaternary ammonium salt is Poly(diallyldimethylammonium chloride) or Quaternized Hydroxyethylcellulose ethoxylate; or (c) said nonionic hydrophilic polymer is selected from the group consisting of Polyacrylamide, Poly(N-isopropylacrylamide) and Poly(ethylene glycol).

[0137] In one embodiment, the solution is a 2wt% solution comprising 31.8% of polyethyleneimine, 8.7% of Poly (diallyldimethylammonium chloride), 19.7% of Polyacrylamide, 13.1% of ammonium polyphosphate.

[0138] In one embodiment, the mass fraction of N for the coating is 26.56wt%. [0139] In one embodiment, the polycationic polymer is a multiarm polytelechelic polymer comprising >14 arms.

[0140] The present invention also provides a coated object comprising: (a) a substrate; and (b) a coating of an embodiment of the present invention.

[0141] In one embodiment, the coating is coated on a hydrophobic surface of said substrate that has been treated with an amphiphilic coupling agent.

EXAMPLES

[0142] To obtain the above results, outcomes and findings, various tests are performed. For example, air permeability test, viral filtration efficiency test and bacterial filtration efficiency test are performed. All three tests are known. Figs 4 to 14 illustrates different results and findings of these three tests.

EXAMPLE 1 - Air Permeability Test

[0143] Referring to Fig. 4 indicates measurement on differential pressure of air permeability of different fabric materials with coating and without coating. Based on the test results, woven cellulose fabric / woven fabric coated by HALs and non-woven cellulose fabric / non-woven fabric coated by HALs have higher air permeability than conventional meltblown materials.

EXAMPLE 2 - Viral Filtration Efficiency Test

[0144] Referring to Figs 5 -12, Viral Filtration Efficiency (VFE) Tests are performed on the fabric materials with coating and without coating respectively. The results indicate that VFE of the coated fabric material performs 15 folds better than the uncoated fabric material. VFE reaches 99.999%.

Cellulose fabric Coated by HALs

[0145] According to “Polyethylenimine surface layer for enhanced virus immobilization on cellulose, Ghania Tiliket, Guy Ladam, Quang Trong Nguyen, Laurent Lebrun, 2016”, the regeneration of cellulose subtracted coated by HALs is shown by the comparison of the respective FTIR spectra of the hydrolyzed cellulouse surface and the pure cellulosic non-woven KWL. The spectra are almost superimposable, which prove the effective modification of cellulose fabric into cellulose (Fig. 5A). Moreover, the unmodified side of the substrate keeps the spectral signature of cellulose fabric with a strong band at 1700 cm-1 corresponding to the C=0 group of ester (Fig. 5B). The impact of the hydrolysis treatment on cellulose fabric coated by HALs is also inspected by water contact angle measurements. The water contact angle is significantly decreased from 71° (□ 6°) before hydrolysis to 48° (□ 4°) after hydrolysis, consistently with the conversion of cellulose fabric coated by HALs into more hydrophilic cellulose. From AFM data, no structural change occurred upon the conversion of cellulose fabric (Fig. 6). Both native and modified coatings have mainly flat uniform morphologies, but with scattered defects. These defects consist in holes likely to be due to the detachment of small pieces of material which are then re-deposited onto the coating. Detachment might occur during spin-coating, rinsing and/or drying operations at sites of weak adhesion of the coating onto gold, possibly due to entrapped nano-bubbles. The presence of holes allows the coating thickness (30 ± 2 nm) to be measured. The influence of holes on further PEI adsorption measurements by QCM-D is negligible because the fraction of uncovered gold surface was very small (ca. 5%), based on assumption.

PEI Adsorption onto Cellulose Substrate

[0146] The initial pH of the PEI 4.4% w/v solution is 11. When the pH decreases, the amine nitrogen atoms on PEI are protonated and the fixation ability on the support increases. The previous virus filtration experiments show a better virus retention at pH=6. At pH = 6, the amine protonation ratio was determined to be 75% ± 5. For this reason, the PEI adsorption measurements were performed at pH = 6. The adsorption of PEI onto the regenerated cellulose is studied by QCM-D. 3 experiments is performed and averaged. The changes with time of the normalized frequencies following successive injections of PEI solutions at increasing concentrations were reported in Fig. 7A. The decreases in Af _n /n observed after each injection (as considered after rinsing with the NaCl 0.2 M reference medium) is revealed the uptake of mass by the cellulose fabric due to the PEI adsorption. As previously shown by Swerin et al. and Ahola et ah, when highly charged cationic polyelectrolytes were layered on hydrated cellulose (at low salt concentration), the uptake of PEI (pKa = 7.7 and pKa = 9.7; cationic at pH = 6) might have been accompanied by the release of water from the cellulose substrate.

[0147] However, the QCM-D technique cannot distinguish between both effects. The normalized frequencies after rinsing are almost superimposed, suggesting that the PEI-treated film had a rigid structure. The very weak increases of the dissipation factors (as measured in the NaCl 0.2 M reference medium) (Fig. 7B) confirms the rigid character of the film (ADn = 8xl0 ⁷ for the largest PEI concentration (1% w/v)). Therefore, the Sauerbrey equation can be applied. The first adsorption step is carried out with a PEI 0.1% w/v solution led to the adsorption of about 100 ng cm ² PEI onto the cellulose film (Fig. 8). Each further PEI injection (at 0.4, 0.7 and 1% w/v) allows limited additional adsorption of PEI onto the cellulose substrate, in such a manner that a ten-fold increase of the PEI concentration improves the adsorbed mass only by a factor 1.4. This result shows that a high PEI concentration may not be required to mostly cover the regenerated cellulose surface.

Influence of the Ionic Strength on the Stmcture of the PEI Laver Deposited onto Cellulose Substrate

[0148] The impact of the ionic strength on the structure of adsorbed PEI is studied by QCM-D in order to test the stability of the adsorbed layer. A regenerated cellulose fabric is first coated with PEI (PEI 0.1% w/v in NaCl 0.2 M) and then, put in contact with solutions of increasing NaCl concentrations (0.05 M, 0.5 M, 1 M), with intermediary rinsing steps at NaCl 0.2 M. The corresponding changes in normalized frequencies Afn/n and in dissipation factors ADn are recorded throughout the protocol. As a control experiment, the same protocol is performed with a native regenerated cellulose film (without adsorbed PEI), to know the combined influence of (i) the solution viscosity changes and (ii) the potential structural changes of the cellulose substrate, on the QCM-D parameters. The QCM-D data measured in the presence of PEI is then corrected from these contributions (by subtraction), and is shown in Fig. 9 for analysis of the structural impact of the ionic strength on the adsorbed PEI layer itself. A mass uptake is detected after the PEI injection and rinsing step, as shown by the decrease in the resonance frequencies. The decrease of the NaCl concentration to 0.05 M induces a water uptake as indicated by the decrease of the resonance frequencies, while subsequent increases of the NaCl concentration to 0.5 M or 1 M induced similar releases of water. Such swelling and deswelling behaviours are expected, based on the well- established electrostatic screening effect, which strengthens or weakens the intra- and interchain electrostatic repulsions of polyelectrolytes at low or high ionic strength, respectively, leading to chain elongation or coiling. Decreases of the dissipation factors at high NaCl concentrations (0.5 M and 1 M) reveals a stiffening of the PEI layer, consistently with a deswelling effect. In contrast, no significant increase of the dissipation factors is measured in the presence of the 0.05 M NaCl solution. It might be due to a slight bias in the correction of the QCM-D parameters, if the contribution of the underlying cellulose is not exactly reproducible between the experiment in the presence of PEI, and the control experiment.

[0149] The swelling of the PEI layer upon rinsing at 0.05 M NaCl is confirmed by the slightly increased dissipation factor as measured after the replacement of the 0.05 M NaCl solution by the 0.2 M NaCl. The PEI layer swelling induced by the lower ionic strength treatment is irreversible, while the deswelling effects observed upon higher ionic strength treatments were reversible, with the /Sfnln and A On restored to their previous values after 0.2 M NaCl rinsing. By decreasing the electrostatic screening effect and, in turn, increasing both the repulsive interactions between PEI chains and the attractive interactions between PEI chains and the underlying cellulose, the low ionic strength treatment might have allowed the re-organization of the PEI chains at the surface of the cellulose film, leading to a more strongly bound PEI layer.

[0150] In spite of significant ionic strength variations imposed by the consecutive rinses, the PEI layer is not destructed by the increased electrostatic repulsion between the PEI chains at low ionic strength, or by the reduced electrostatic attraction between the PEI chains and the underlying cellulose at high ionic strength, showing the good stability of our system.

Adsorption of T4D Bacteriophages onto PEI-Treated Cellulose Substrate

[0151] AFM observations of silicon substrates after contact with a suspension of T4D bacteriophages are first carried out to verify that intact viruses are adsorbed on the support and not only residues, such as proteins, due to the filtering process. The AFM image included in Fig.10 shows the presence of many intact bacteriophages constituted of a head and a tail, with a size of 120 nm. Some bacteriophages appeared broken, and the presence of aggregates (proteins or unstructured viruses) is also detected.

[0152] QCM-D is then used to compare the adsorption behaviors of T4D bacteriophages onto native, and onto PEI-treated cellulose. The PEI concentration for the deposit is 1% w/v to be in agreement with the method used for the preparation of PEI functionalized filters for antiviral masks. The concentration is higher than the minimal 0.1% w/v concentration recommended in section PEI adsorption onto cellulose fabric because the filters are porous non-woven materials with much larger surface than plane supports. The corresponding changes in the QCM-D parameters are shown in Fig. 11. The frequency curves are not strictly superimposed after bacteriophage adsorption and rinsing step, showing the viscoelastic character of the bacteriophage layer. This is confirmed by the increases in dissipation factors, especially for PEI- treated cellulose ( ADn = 4xl0 ⁶ without PEI, A Dn = 27xl0 ⁶ with PEI). Consequently, the linear Sauerbrey equation cannot be applied to derive the adsorbed amounts from the frequency shifts. Therefore, the raw QCM-D data within the frame of the Voigt viscoelastic model by using the Q- Tools software (Q-Sense) is analyzed.

[0153] The evolution of thicknesses derived from the data modelling for bacteriophage layers adsorbed onto untreated and onto PEI-treated cellulose are given in Fig. 12. The thickness of the adsorbed PEI layer on the cellulose film (as considered after the rinsing step) is around 3.5 nm. Promisingly, the bacteriophage layer is 15 -fold thicker (93 nm) when it is deposited onto the PEI- treated, than onto the untreated cellulose substrate. This proves the strong affinity between the bacteriophage and the PEI-treated regenerated cellulose. This affinity can be mainly explained by the strong electrostatic interactions between the positively charged PEI and the negatively charged viruses. For instance, Anany et al. have prepared active membranes against E. coli and Listeria by immobilizing T4 bacteriophages by their head on positively charged modified cellulose membranes. Li et al. also show that it is possible to bind T4 bacteriophages onto cellulose via proteins in order to prepare antibacterial paper. The adsorption of a polyelectrolyte onto a charged surface leads to an overcompensation of the surface charge. Thus, when polycationic PEI chains adsorb onto cellulose, the surface becomes positively charged and promotes the electrostatic attraction of negatively charged sites on other material. For example, PEI-treated cellulosic microporous membranes capture glucose oxidase, amylase or heparin, leading to highly active enzyme membranes. PEI is also currently used to bind RNA or DNA to adenovirus particles through electrostatic interactions.

[0154] Moreover, the PEI chain flexibility promotes chain folding and, in turn, optimization of local interactions on the virus surface. Thus, the PEI chains with a large charge density and an extremely large contour length offer optimal conditions for virus capture.

EXAMPLE 3 - Bacterial Filtration Efficiency Test

[0155] Referring to Figs 13 - 14, Bacterial Filtration Efficiency (BFE) Tests on the fabric materials with coating and without coating respectively. The results indicate that BFE of the coated fabric material performs 25 folds better than the uncoated fabric material. BFE reaches 99.9703%

[0156] For example, Biological Aerosol of Staphylococcus Aureu is used to measure the bacterial filtration efficiency (BFE) of medical face mask materials, employing a ratio of the upstream bacterial challenge to downstream residual concentration to determine filtration efficiency of medical face mask materials.

[0157] 2250 Staphylococcus Aureus were sprayed over testing subject via biological aerosol, and bacterial fall count is measured. By comparing bacterial fall count, BFE of different testing subject can be induced.

[0158] Fig. 13 shows that BFE of cellulose fabric with 2% PEI are 25 folds better than meltblown material and further proves that the efficiency of PEI on BFE.

[0159] Fig. 14 shows the actual bacterial fall counts of cellulose fabric with 2% PEI.

EXAMPLE 4 - Embodiment for an air filtration used with an antiviral face mask

[0160] Fig. 3 illustrates an example of an antiviral face mask having an air filtration system of Fig. 1 in accordance with various embodiments of the present invention. In one embodiment, face mask 300 includes air filtration system / air filter 302 /100, a pair of straps 304 and wire 306. In this example, strap 304 is made of elastomer such as rubber and is provided at each side of air filtration system / air filter 302 to support face mask 300 at a pair of a user’s ears. Wire 306 is provided inside the top of air filtration system / air filter 302. Wire 306 is deformable to enhance sealability of face mask 300 along the ridge from the user’s nose to chin. Antiviral face mask 300further includes at least three pleats 308 in the horizontal direction of air filtration system / air filter 302 to enhance sealability along the contour of the user’s face up to the lower portion of the chin. Air filtration system / air filter 302 is shaped to be hemispherical and the middle of filter 302 is concaved.

[0161] Antiviral face mask 300 having a shape and a structure exhibit high sealability between the user’s face and antiviral face mask 300 and facilitates breathing of the user.

[0162] There is no limitation on what air filtration system / air filter 302 is used with. In one example, air filtration system / air filter 302 may be used in an air purifier or air conditioner. In another example, air filtration system / air filter 302 may be used in protective helmet or the like.

EXAMPLE 5 - Results for materials coated with polytelechelic compounds Effect on viruses

[0163] In order to test the affinity and virucidial effect of materials coated with the polytelechelic compounds to viruses, they were tested with other materials commonly used in the laboratory or for the manufacturing of masks. Five different materials were tested: Tissue paper used in the laboratory, a filter of FFP2 standard, a sponge of FFP2 standard, spunlace material with the polytelechelic compounds applied, and paper with the polytelechelic compounds applied.

[0164] A 2.5x2.5 cm piece of each material was placed into a separate 2ml Eppendorf tube, and 200m1 of HCoV-229E virus containing buffer at about 50000 PFU was added to each tube. The tubes were incubated for 5 minutes, then they were centrifuged to remove the buffer solution from the test material. The test material was removed from the tube and the virus concentration left in the buffer was measured using RT-qPCR. The same experiment was repeated with an incubation time of 60 minutes, and both sets of experiments were also repeated with Coxsackievirus B6 instead of the HCov-229E. The experimental method is also shown in Fig. 23.

[0165] As seen in Fig. 24A and 24B, the virus concentration for both HCoV-229E and Coxsackievirus B6 remained very high with the tissue, FFP2 filter and FFP2 sponge, In each case, regardless of whether the tubes were incubated with the test material for 5 or 60 minutes, the reduction in the tested virus concentration was more than half of the original concentration. This shows that the tissue, FFP2 filter and FFP2 sponge materials have minor affinity to the tested viruses. Conversely, the virus concentrations left in the buffer were very low for both the spunlace and paper treated with the polytelechelic materials. Only less than or equal to 10 copies of the viruses remained in the buffer solution after the incubation and centrifugation. It can thus be concluded that both tested virus strains have a strong affinity to the polytelechelic compounds of the materials.

Viral Filtration Efficiency Test

[0166] A further test was performed to determine the filtration efficiency of a textile material coated with the polytelechelic compounds, by comparing the viral control counts upstream of the test article to the counts downstream. A suspension of bacteriophage FC174 was aerosolized using a nebulizer and delivered to the test article, which is a non-woven white textile coated with the polytelechelic compounds, at a constant flow rate and fixed air pressure. The challenge delivery was maintained at 1.1 - 3.3 x 10 ⁶ plaque forming units (PFU) with a mean particle size (MPS) of 3.0 ± 0.3pm. The aerosol droplets were drawn through a six-stage, viable particle, Andersen sampler for collection. The results are shown in Table 1 below.

Table 1: Results for antibacterial ability against Staphylococcus aureus [0167] Using a test area of about 40cm ² , a VFE flow rate of 28.3 L/min and conditioning parameters of 85_± 5% relative humidity and 21 ± 5 °C for a minimum of 4 hours, the percentage VFE tested for each of the 5 repeated experiments were over 99.9%, as no plaques were detected on any of the Andersen sampler plates for all test articles. All of the bacteriophages were captured under the fast air flow, indicating that the material with polytelechelic compounds have a high affinity to viruses.

Effect on bacteria

[0168] Two white textile specimens coated with the polytelechelic compounds were tested for their antibacterial ability. One milliliter of an inoculum of Staphylococcus aureus with a concentration of 1 x 10 ⁶ CFU/ml to 3 x 10 ⁶ CFU/ml was applied onto an agar plate, where each specimen was set on the agar surface and weighted down with a 200g stainless steel cylinder for 60 ± 5 s to transfer the microbial content. The bacteria was then shaken out using peptone water, before incubation for one specimen and after incubation for the other specimen. The resulting number of bacteria for each sample is shown in Table 2 below. Based on the results obtained, the specimens demonstrated effective antibacterial property to kill the Staphylococcus aureus bacteria during the transfer phase of the experiment.

Table 2: Results for antibacterial ability against Staphylococcus aureus

[0169] A further experiment using the same testing conditions and methods were conducted on 3 different types of materials coated with the polytelechelic compounds: 100% cotton, 65% polyester + 35% cotton, and 92% polyester + 8% spandex twill. Each material was tested without washing and after 60 washes. The results are shown in Table 3 below:

Table 3: Results for antibacterial ability against Staphylococcus aureus for various materials

[0170] According to Wiegand et al. ¹ , an antimicrobial activity value less than 0.5 represents no antibacterial activity. Values between 0.5 and 1 are rated as a slight, values greater than 1 and less than or equal to 3 as a significant, and a log reduction greater than 3 as a strong antibacterial activity. The experimental results show that almost all samples show strong antibacterial activity, even after 60 washes.

[0171] Various exemplary embodiments are described herein. Reference is made to these examples in a non-limiting sense. They are provided to illustrate more broadly applicable aspects of the disclosed technology. Various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the various embodiments. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, process, process act(s) or step(s) to the objective(s), spirit or scope of the various embodiments. Further, as will be appreciated by those with skill in the art, each of the individual variations described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the various embodiments.

References: 1. Wiegand C., Heinze T., Hipler U.C. (2009) Comparative in vitro study on cytotoxicity, antimicrobial activity and binding capacity for pathophysiological factors in chronic wounds of alginate and silver-containing alginate. Wound Repair Regen., 17, 511-521.