WO2021202820A1

WO2021202820A1 - Electrospun nanofibrous polymer membrane for use in personal protective equipment

Info

Publication number: WO2021202820A1
Application number: PCT/US2021/025285
Authority: WO
Inventors: Sherif SOLIMAN; Feng Guo
Original assignee: Matregenix, Inc.
Priority date: 2020-03-31
Filing date: 2021-03-31
Publication date: 2021-10-07
Also published as: EP4127150A4; CN116034156A; CA3174368A1; EP4127150A1; JP2023520541A; KR20230076803A

Abstract

An electrospun polymer nanofibrous membrane that provides high filtering efficiency and excellent porosity is disclosed herein. The membrane may be treated with one or more antimicrobial or antiviral agents. The treatment may preferably be a coating of one or more antiviral agents on the surface of the membrane. Alternatively, one or more antiviral agents may be impregnated into the nanofibrous membrane. The membrane may additionally or alternatively be impregnated with one or more metal-organic frameworks (MOFs). The membrane has a high filtering efficiency and sufficient porosity to provide breathability characteristics. The membrane is suitable for use in making facemasks and respirators that are highly resistant to infectious pathogens and/or other small particulates.

Description

ELECTROSPUN NANOFIBROUS POLYMER MEMBRANE FOR USE IN PERSONAL PROTECTIVE EQUIPMENT

_{CROSS REFERENCE TO RELATED APPLICATIONS}

[0001] 'this application claims the benefit of, and priority to, U.S. Provisional Patent

Application Serial Nos. 63/002,435, filed on March 31, 2020, and 63/116,799, filed on

November 20, 2020, the disclosures of which are hereby incorporated in their entireties herein by reference.

Field of the Invention

[0002] The present disclosure relates to materials for use in personal protective equipment.

Description of the Related Art [0003] Community acquired respiratory virus (CARV) infections include infections caused by a variety of viruses, including coronaviruses, rhinoviruses, influenza viruses, and metapneumovirus . See, e.g., Versluys, A.B., et al. “Morbidity and Mortality Associated With Respiratory Virus Infections in Allogeneic Hematopoietic Cell Transplant: Too Little Defense or Harmful Immunity?” Front, Microbiol 2018, 9, 2795-2795, doi;10.3389/ftnicb.2018.02795. Many CARV infections result in significant morbidity and mortality. For example, the Spanish flu pandemic of 1918 killed between 20 million and 50 million people worldwide. Roos, D. “Why the Second Wave of the 1918 Spanish Flu Was So Deadly,” History.com, 2020 (available at: https://www.histoiy.com/news/spanish-flu- second- wave-resurgence) . In addition, influenza pandemics are known to emerge cyclically. The current coronavirus disease 2019 (COVED- 19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become the foremost global health problem of the current century and is the worst pandemic since the Spanish flu pandemic .

[0004] Infectious respiratory pathogens are typically transmitted by droplet, aerosol, or airborne transmission of particles expelled from the respiratory tract of an infected person by coughing or sneezing, or in some cases by simple exhalation. To prevent this form of transmission, facemasks and respirators have been developed that either mechanically intercept the infectious particles or that disarm the infectious particles using a variety of mechanisms. Therefore, many research and development efforts have been made to enhance the filtering efficiency Of facemasks and respirators.

[0005] The COVID-19 pandemic has highlighted the need for functional protective textiles for a variety of applications. Functional protective textiles are particularly important for use in protective clothing for medical professionals, field workers, and soldiers. See, e.g., Zhu, Q., el al. “AQC Functionalized CNCs/PVA-co-PE Composite Nanofibrous Membrane with Flower-Like Microstructures for Photo-Induced Multi-Functional Protective Clothing,” Cellulose , 2018, 25, 4819-30, doi: 10.1007/sl0570-018-188l-5; Liu, Y„ et al. “UV- Crosslinked Solution Blown PVDF Nanofiber Mats for Protective Applications,” Fibers Polym. 2020, 21, 489-97, doi: 10.1007/sl222l-020-9666-5.

[0006] To limit dermal exposure to airborne solid particles, health and safely regulatory agencies have published good practice guidelines, and wearing persona! protective equipment (PPE) has been recommended to minimize exposure to a variety of hazards. Chemical and biological protective clothing (CBPC) are widely used and are considered the most economical among PPE options. For airborne nanomaterials, type 5 CBPC is considered die last line of defense against such dangers, as it provides full body protection against airborne solid particulates according to the ISO 13982-1 and ISO 13982-2 standards. See International Organization for Standardization (ISO) 13982-1 :2004; International Organization for Standardization (ISO) 13982-2:2004.

[0007] Nonwoven and woven materials commonly used as the base for type 5 CBPC have several disadvantages, such as poor permeability and filterability. See, e.g., Liu, Y„ et al. , supra; Wingert, L., et al. “Filtering Performances of 20 Protective Fabrics Against Solid Aerosols,” J. Occup. Environ . Hyg. 2019, 16, 592-606.

Current commercially available facemasks and respirators either do not have adequate filtering efficiency to intercept the infectious particles or have insufficient air permeability to allow frequent and convenient use. Lee, S., et al. “Reusable Polybenzimidazole Nanofiber Membrane Filter for Highly Breathable PM₂.₅ Dust Proof Mask ” ACS Appl Mater. Interfaces, , 2019, 11, 2750-57, doi:10.1021/acsami.8bl9741. Moreover, the recent COVID-19 pandemic has increased interest in antiviral membrane development for facemasks and respirators which will exterminate pathogens contacting the facemask or respirator. This will prevent infectious particles to be transferred to another surface by inadvertent contact of the mask with other surfaces or by the wearer touching the exterior surface of the mask by hand.

[0009] Numerous antiviral agents are known that may be suitable for use in coatings or that may otherwise be integrated into personal protective equipment. See, eg., Tran, Ό.Ν., ei al. “Silver Nanoparticles as Potential Antiviral Agents against African Swine Fever Virus,” Mater. Res . Express , 2020, 6(12), doi: 10.1Q88/2O53-1591/ab6ad8; Moreno, M.A., el al “Active Properties of Edible Marine Polysaccharide-Based Coatings Containing Larrea nitida Polyphenols Enriched Extract,” Food Hydrocoil. 2020, 102, 105595, doi: 10.1016/j .foodhyd.2019.105595; Husen, A. “Natural Product-Based Fabrication of Zinc- Oxide Nanoparticles and Their Applications,” In Nanomaterials and Plant Potential , 2019, 193-219, Springer; Cheng, C., et al. “Functional Graphene Nanomalerials Based Architectures: Biointeractions, Fabrications, and Emerging Biological Applications,” Chent. Rev . 2017, 117, 1826-1914; Zhang, D.-h., et al “In Silica Screening of Chinese Herbal Medicines with the Potential to Directly Inhibit 2019 Novel Coronavirus,” J. Integr Med. 2020, 18_, 152-8, doi: 10.1016/j.joim.2020.02.005; US. Patent Nos. 9,963,611 and 8,678,002. [0010] Various techniques for producing nanofiber membranes are known, including electrospinning, phase inversion, interfacial polymerization, stretching, and trackretching. Electrospinning is a very useful technique that provides efficiency and uniformity of pore size. See, e.g., Ray, S.S., et al. “A Comprehensive Review: Electrospinning Technique for Fabrication and Surface Modification of Membranes for Water Treatment Application,” RSC Adv. 2016, 6(88), 85495-85514, doi: 10.1O39/C6RA14952A. Electrospinning is a process that uses an electric field to generate continuous fibers on a micrometer or nanometer scale. Electrospinning «tables direct control of the microstructure of a scaffold, including characteristics such as the fiber diameter, orientation, pore size, and porosity.

[0011] Electrospun nanofibers have a wide range of applications. These include antibacterial food packaging, biomedical applications, and environmental applications. See, e.g., Lin, L., et at. “Cold Plasma Treated ^'thyme Essential Oil/Silk Fibroin Nanofibers against Salmonella Typhimurium in Poultry Meat,” Food Packag. Shelf Life, 2019, 21, 100337; Zhu, Y., et at. “A Novel Polyethylene Oxi de/Dendrobium officinale Nanofiber: Preparation, Characterization and Application in Pork Packaging,” Food Packag. Shelf Life , 2019, 21, 100329; Surendhiran, D., et at. “Encapsulation of Phlorotannin in Alginate/PEO Blended Nanofibers to Preserve Chicken Meat from Salmonella Contaminations,” Food Packag. Shelf Life, 2019, 21, 100346; Khan, M.Q., et al. “The Development of Nanofiber Tubes Based on Nanocomposites of Polyvinylpyrrolidone Incorporated Gold Nanoparticles as Scaffolds for Neuroscience Application in Axons,” Text Res. J. 2019, 89, 2713-20, doi: 10.1177/0040517518801185; Ullah, S., et al “Antibacterial Properties of In Situ and Surface Functionalized Impregnation of Silver Sulfadiazine in Polyacrylonitrile Nanofiber Mats,” Ini. J. Nanomedicine , 2019, 14, 2693-2703, doi: 10.2147/DN.S 197665; Khan, M.Q., et al “Fabrication of Antibacterial Electrospan Cellulose Acetate/S ilver-Sul fadiazine Nanofibers Composites for Wound Dressings Applications,” Polym. Test. 2019, 74, 39-44. Doi; 10.1016/j.polymertesting.2018.12.015; Ray, S.S., et al. , supra.

[0012] Electrospun nanofiber textiles have been considered promising candidates for CBPC. See, e.g., Lee, S„ et al. “Transport Properties of Layered Fabric Systems Based on Electrospun Nanofibers,” Fibers Polym. 2007, 8, 501-06; Bagherzadeh, R., et al. “Transport Properties of Multi-Layer Fabric Based on Electrospun Nanofiber Mate as a Breathable Barrier Textile Material,” Text. Res . J. 2012, 82, 70-76.

[0013] Electrospun polymeric nanofibers may exhibit very high external surface area, excellent water vapor transport properties, and good mechanical strength. See, e.g., Huang,

Z., et at. “A Review on Polymer Nanofibers by Electrospinning and Their Applications in Nanocomposites Compos. Sci. Technol. 2003, 63, 2223-53.

[0014] Fabrication of textiles from electrospun polymeric nanofibers generates ultrathin, lightweight, and high tensile strength textiles. See, e.g, Lee, S., et at ., supra; Dhineshbabu, N. R., et at. “Electrospun MgO/Nylon 6 Hybrid Nanofibers for Protective Clothing,” Nano- Micro Lett 2014, 6, 46-54; Han, Y., et at. “Reactivity and Reusability of Immobilized Zinc Oxide Nanoparticles in Fibers on Methyl Parathion Decontamination,” Text Res. J. 2013, 86, 339-49. toois] Chen, et at. disclose functionalized nanofiber mats generated by integrating nucleophilic oxime moieties through electrospinning of polyacryiamidoxime (PAAO) and

PAN. These functionalized nanofiber mas exhibited a substantial ability to hydrolyze chemical nerve agents. Chen, L., et at. “Multifunctional Electrospun Fabrics via Layer-by- Layer Electrostatic Assembly for Chemical and Biological Protection,” Chem. Mater. 2010, 22, 1429-36.

[0016] Choi, et al disclose fabricated polyurethane nanofibers functionalized by N- chloro hydantoin (NCH-PU). These nanofibers successfully decontaminated a simulant for V-type nerve gas (demeton-S-methyl). Choi, J., et al “N-Chloro Hydantoin Functionalized Polyurethane Fibers Toward Protective Cloth Against Chemical Warfare Agents,” Polymer , 2018, 138, 146-55.

[0017] Various metal nanopartides integrated nanofibers have been disclosed that have been proposed for use in protective clothing and face masks for shielding against harmful chemicals and biological agents. See, e.g, Ramaseshan, R., et ah “Zinc Titanate Nanofibers for the Detoxification of Chemical Warfare Simulants, ./. Am. Ceram. Soc. 2007, 90, 1836-

42.

[0018] Lee, et ah disclose functional PAN nanofiber webs to protect users from a simulant of a chemical warfare agent (CWA). Lee, J., et at “Preparation of Non- Woven Nanofiber Webs for Detoxification of Nerve Gases,” Polymer , 2019, 179, 121664.

[0019] Zhao, et ah disclose metal-organic frameworks (MOFs) integrated into polyamide-6 nanofibers. The MOF-nanofiber composites exhibited extraordinary reactivity for detoxifying CWAs. Zhao, J_M et ah “Ultra-Fast Degradation of Chemical Warfare Agents Using MOF-Nanofiber Kebabs,” Angew. Chem . ini. Ed. 2016, 55, 13224-28.

[0020] Antiviral agents have been incorporated into electrospun fibers for prevention of

HIV infection. Grooms, T. N., et ah “Griffithsin-Modified Electrospun Fibers as a Delivery

Scaffold To Prevent HIV Infection,” Antimicrob. Agents Chemother. 2016, 60, 6518.

[0021] There remains a need for new materials to develop high-performance membranes with antiviral and other anti-pathogenic properties that have high filtering efficiency and breathabi!ity for use in facemasks and respirators.

SUMMARY

[0022] An electrospun polymer nanofibrous membrane that provides high filtering efficiency and excellent porosity is disclosed herein. [0023] The membrane may be treated with one or more antimicrobial or antiviral agents. In some embodiments, the membrane may be treated with an antiviral agent selected from the group consisting of graphene, nanoparticies, nanocomposites, multivalent metallic ions, and medicinal or other extracts from natural products. The treatment may preferably be a coating of one or more antiviral agents on the surface of the membrane. Alternatively, one or more antiviral agents may be impregnated into the nanofibrous membrane.

[0024] The membrane may additionally or alternatively be impregnated with one or more metal-organic frameworks (MOFs). The one or more MOFs may, for example, be one or more zirconium MOFs. The MOFs may provide filtration of chemical warfare agents (CWAs) and other toxic chemical agents and, in some embodiments, may also provide additional or alternate filtration of small particulates and pathogens.

[0025] The disclosed membrane may preferably have a high filtering efficiency. ^'Che porosity of the disclosed membrane may preferably be sufficient to provide breathabiliiy characteristics suitable for use as a facemask or respirator. The disclosed membrane is suitable for use in making facemasks and respirators that are highly resistant to infectious pathogens and/or other small particulates.

BRIEF DESCRIPTION OF THE DRAWINGS [0026] FIG. I shows representative scanning electron microscopy (SEM) images of embodiments of the disclosed nanofibrous polymer membranes.

[0027] FIG. 2 shows fiber diameter measurements and distribution for representative samples of an embodiment of the disclosed nanofibrous polymer membrane.

[0028] FIG. 3 shows pore size distribution for representative samples of an embodiment of the disclosed nanofibrous polymer membrane as determined by mercury porosimeter analysis.

[0029] FIG. 4 shows average porosity and the distribution of mean porosity for representa tive samples of an embodiment of the disclosed nanofibrous polymer membrane. [0030] FIG. 5 shows mechanical tensile strength test results for representative samples of an embodiment of the disclosed nanofibrous polymer membrane.

[0031] FIG. 6 shows filtration efficiency test results for representative samples of an embodiment of the disclosed nanofibrous polymer membrane. [0032] FIG. 7 shows latex filtration test results for representative samples of an embodiment of the disclosed nanofibrous polymer membrane.

[0033] FIG. 8 shows viral filtration efficiency test results for representative samples of an embodiment of the disclosed nanofibrous polymer membrane.

[0034] FIG. 9 shows bacteria filtration efficiency test results for representative samples of an embodiment of the disclosed nanofibrous polymer membrane.

[0035] FIG. 10 shows flammability test results for a representative sample of an embodiment of the disclosed nanofibrous polymer membrane.

[0036] FIG. 11 shows antiviral properties test results for representative samples of an embodiment of the disclosed nanofibrous polymer membrane.

[0037] FIG. 12 shows antibacterial properties test results for representative samples of an embodiment of the disclosed nanofibrous polymer membrane.

[0038] FIG. 13 shows how filtration efficiency is affected by the flow rate of aerosols through the membrane.

[0039] FIG. 14 shows how the pressure drop across the membrane is affected by the flow rate of aerosols through the membrane.

DETAILED DESCRIPTION

[0040] An electrospun polymer nanofibrous membrane that provides high filtering efficiency and excellent porosity is disclosed herein.

[0041] The membrane may be treated with one or more antimicrobial or antiviral agents. In some embodiments, the membrane may be treated with an antiviral agent selected from the group consisting of graphene, nanoparticles, nanocomposites, multivalent metallic ions, and medicinal or other extracts from natural products. The treatment may preferably be a coating of one or more antiviral agents on the surface of the membrane. Alternatively, one or more antiviral agents may be impregnated into the nanofibrous membrane.

[0042] The membrane may additionally or alternatively be impregnated with one or more metal-organic frameworks (MOFs). The one or more MOFs may, for example, be one or more zirconium MOFs. The MOFs may provide filtration of chemical warfare agents (CWAs) and other toxic chemical agents and, in some embodiments, may also provide additional or alternate filtration of small particulates and pathogens. [0043] The disclosed membrane may preferably have a high filtering efficiency. The porosity of (he disclosed membrane may preferably be sufficient to provide breathability characteristics suitable for use as a facemask or respirator. The disclosed membrane is suitable for use in making facemasks and respirators that are highly resistant to infectious pathogens and/or other small particulates.

[0044] The disclosed membrane may preferably have a filtering efficiency of at least

95%, more preferably at least 98%, even more preferably at least 99%, and most preferably at least 99.5%.

[0045] The disclosed membrane may preferably be capable of intercepting and exterminating infectious pathogens on its surfaces.

[0046] In some preferred embodiments, the disclosed membrane is non-flammable.

[0047] The disclosed membrane may be suitable for the production of non-flammable high-performance textiles.

[0048] In some preferred embodiments, the disclosed membrane is ullrathin and lightweight

[0049] In some preferred embodiments, the disclosed membrane does not degrade upon exposure to water or selected organic solvents such as ethanol or acetone. Thus, products made using the membrane may be washed and reused.

[0050] In some embodiments, the nanofibrous polymer membrane may be made from polyvinylidene fluoride (PVDF). In some alternate embodiments, the nanofibrous polymer membrane may be made from one or more Tecophilic™ thermoplastic polyurethanes (TPlis). In some other alternate embodiments, the nanofibrous polymer membrane may be made from a blend of polyvinylidene fluoride and one or more Tecophilic™ thermoplastic polyurethanes.

[0051] e nanofibrous polymer membrane may be made using electrospinning techniques. A polymer is dissolved in a solvent prior to electrospinning. In some embodiments, the solvent may preferably be selected from the group consisting of dimethyifonnamide (DMF), dimethylacetamide (DMA), hexafl uoroisopropanol (HFIP), acetone, water, or a combination thereof.

[0052] In some embodiments, a surfactant may be added to the polymer solution. Adding a surfactant to the polymer solution may promote a smaller fiber diameter and thus yield a membrane which has a smaller pore size and thus higher filtration efficiency. In some preferred embodiments, the surfactant may be one or more surfactants selected from the group consisting of cetrimomum bromide (CTAB), lauramidopropyl betaine (LAPS), and alpha olefin sulfonate (AOS).

[0053] In some embodiments, a salt or salt solution may be added to the polymer solution. Adding a salt or salt solution to the polymer solution may promote formation of thinner and more uniform fibers and may also reduce bead formation. By increasing charge density and conductivity, the presence of salts in the polymer solution promotes elongation of the spinning jet, which leads to the generation of thinner fibers. In some preferred embodiments, the salt or salt solution may be one or more salts or salt solutions selected from the group consisting of alkali metal halides and phosphate-buffered saline (PBS). In some more preferred embodiments, the salt or salt solution may be one or more salts selected from the group consisting of sodium chloride (NaCl), lithium chloride (LiCI), and potassium chloride (KC3).

[0054] The nanofibrous polymer membrane may be a single layer membrane or may alternatively be an integrated multi-layer membrane. In some embodiments, the membrane may be composed of multiple integrated layers with distinguishable microstructure characteristics. A membrane that is composed of multiple integrated layers may provide enhanced filtration efficiency and high breathability. The enhanced filtration efficiency of an integrated multi-layer membrane may result from superior barrier protection against small pathogen particles.

[0055] In some embodiments, the integrated multi-layer membrane is composed of two layers with different pore sizes. In some alternate embodiments, the integrated multi-layer membrane is composed of three layers with two layers of equal pore size separated by a layer with a different pore size. The pore size may preferably be between 1 and 20 pm for the Iayer(s) with smaller pore size and between 20 and 200 pm for the iayer(s) with larger pore size.

[0056] In embodiments with three layers having two layers of equal pore size separated by a layer with a different pore size, the layers of equal size may preferably have a larger pore size and foe layer in between these two layers may preferably have a smaller pore size. This configuration decreases the likelihood of delamination and also decreases the pressure drop that is generated as a gas passes through the multi-layer membrane, which corresponds to increased breathabiiity, without appreciably reducing the filtration efficiency of the membrane.

[0057] In some other alternate embodiments, the integrated multi-layer membrane is composed of three layers with three different pore sizes,

[0058] The pore size of the layers in integrated multi-layer membranes may be adjusted by adjusting the viscosity of the polymer solution and the electrospinning process conditions. Electrospinning process conditions may be adjusted to further stabilize the spinning jet used in the electrospinning setup. Solutions with lower viscosity will typically generate smaller pore size layers, and solutions with higher viscosity will typically generate larger pore size layers.

[0059] In some embodiments, the mechanical integrity and binding forces between layers of the membrane may be enhanced by electrospraying short fibers prior to electrospinning the subsequent layer. In some other embodiments, the mechanical integrity and binding forces between layers of the membrane may be enhanced by eiectrospinning wet fibers by decreasing the screen distance to generate a “tacky surface” prior to electrospinning the subsequent layer.

[0060] In some embodiment, the disclosed nanofibrous polymer membrane may be laminated onto a textile material. Alternatively, the nanofibers may be directly electrospun on nonwoven fabrics such as polyethylene terephthalate (PET), polypropylene (PP), and PET copolymers. The use of PET copolymers results in enhanced adhesion between the nanofibers and textile, which thereby reduces peeling.

[0061] The disclosed nanofibrous polymer membrane may be treated with an anti- pathogenic agent such as an antiviral agent selected from the group consisting of graphene, nanoparticles, nanocomposites, multivalent metallic ions, and medicinal or other extracts from natural products. The nanoparticles may preferably be metal nanoparticles such as silver nanoparticles or zinc nanoparticles. The nanocomposites may preferably be silver- doped titanium dioxide nanomaterials, lire multivalent metallic ions may preferably be metal ions such as Cu^{2 +} or Zn₂ ⁺ cations. The extracts from natural products may preferably be licorice extracts. [0062] The anti-pathogenic agent(s) may be physically coated on the surface of the membrane. The coating may be applied using chemical or electrochemical methods such as atomic layer deposition, vapor deposition methods such as physical vapor deposition (PVD) or chemical vapor deposition (CVD), spray coating methods such as plasma spraying or spray painting, or physical coating methods such dip-coating or spin-coating.

[0063] The anti-pathogenic agent(s) may alternatively be incorporated into the membrane by blending the anti-pathogenic agents) into the polymer solution prior to electrospinning, thereby generating a membrane impregnated with the anti-pathogenic agenl(s).

[0064] In some embodiments, the disclosed nanofibrous polymer membrane may be impregnated with one or more metal-organic frameworks (MOFs), such as zirconium MOFs. The MOFs may be incorporated into the membrane by blending the MOFs into the polymer solution prior to electrospinning, thereby generating a membrane impregnated with the MOFs.

[0065] In some embodiments, MOF-impregnation into the membrane may be in addition to coating with or impregnation of anti-pathogenic agent(s). In other embodiments, MOF- impregnation into the membrane may be an alternative to coating with or impregnation of anti-pathogenic agentfs). Membranes impregnated with MOFs may provide filtration of chemical warfare agents (CWAs) and other toxic chemical agents. In some embodiments, membranes impregnated with MOFs may also exhibit antiviral, antibacterial, or other anti- pathogenic properties.

[0066] Thus, it is not intended that the MOFs described herein are necessarily distinct from the anti-pathogenic agents, such as antiviral or antibacterial agents, described herein. Rather, the anti-pathogenic agent may be a MOF or may alternatively be one of the other anti-pathogenic agents described herein. It is also not intended that the MOFs described herein wilt necessarily exhibit antiviral, antibacterial, or other anti-pathogenic properties. MOFs that are impregnated in the disclosed membranes may provide filtration of chemical warfare agents (CWAs) and other toxic chemical agents but, in some embodiments, may not exhibit antiviral, antibacterial, or other anti-pathogenic properties or provide filtration of small particulates.

[0067] To increase the hreathability of textile materials coated with the disclosed nanofibrous polymer membranes, multiple nanofiber layers of differing thicknesses may be electrospun on the same or opposite sides of textile materials. A textile material that is in the form of a textile material roll may be coated with one or more nanofiber layers by electrospinning, in some embodiments, one or more first nanofiber layers are electrospun on a first side of a textile material at a first winding speed, the textile material roll is flipped, and one or more second nanofiber layers are electrospun on a second side of the textile material at a second winding speed, where the first winding speed is different from the second winding speed. In other embodiments, one or more first nanofiber layers are electrospun on a first side of a textile material at a first winding speed, and one or more second nanofiber layers are then electrospun on the first side of tire textile material at a second winding speed, where the first winding speed is different from the second winding speed. In yet other embodiments, one or more first nanofiber layers are electrospun on a first side of a textile material at a first winding speed, one or more second nanofiber layers are then electrospun on the first side of the textile material at a second winding speed, the textile material roll is then fl ipped, and one or more third nanofiber layers are electrospun on a second side of the textile material at a third winding speed, where the first winding speed is different from the second winding speed. In yet other embodiments, additional electrospinning steps may be added to include additional nanofiber layers of different thicknesses on one or both sides of the textile material.

[0068] A facemask or respirator made from the disclosed nano fibrous polymer membrane is also disclosed herein. The facemask or respirator may preferably have a high filtration capacity and suitable breathability characteristics for comfortable use by a wearer. The disclosed facemask or respirator may preferably have a filtering efficiency of at least 95%, more preferably at least 98%, even more preferably at least 99%, and most preferably at least 99.9%.

[0069] A method of making a facemask or respirator from the disclosed nanotibrous polymer membrane is also disclosed herein. The method may preferably allow the anti- pathogenic, physical, chemical, and mechanical properties to be fine-tuned according to the requirements of the specific application. Sample Preparation

[0070] The following sample preparation materials and methods are exemplary. Other suitable materials and methods may be used within the scope of the invention.

[0071] «Materials. Multiple Tecophitic™ thermoplastic polyurethanes (PEU) were purchased from Lubrizol. Knyar 2801 polyvinylidene fluoride (PVDF) was purchased from Arkema. Hexafluoroisopropanol (HFIP) was purchased from Oakwood Products Inc. Dimethylacetamide (DM Ac), acetone, cetrimonium bromide (('TAB), and lithium chloride (LiCl) were purchased from Fisher Scientific. Silver nanopartcies (15 nm) were purchased from Skyspring Nanomaterials. ZnO and CuO (Zn-Cu) were purchased from Sigma Aldrich. Ag-doped T1O2 (Ag-TiOa) nanoparticlcs were provided by JM Material Technology Inc. Licorice extracts were provided by XSL USA Inc.

]0072] Solution Preparation. PEU polymers were added to HFIP to create 7 and 15 w/v solutions. 16.5% wt PVDF was dissolved in 3:1 DMAc/acetone containing 0.85% CTAB and 0.04% Li CL All of the solutions were mixed on a stirring plate until the polymer pellets/powder completely dissolved.

[0073] Antiviral Treatment Two antiviral treatment methods were used: (I) the membranes were submerged in an aqueous dispersion containing antiviral particles, or (2) the antiviral agents were added to the polymer solutions to directly fabricate antiviral nanofibrous membranes. The antiviral agents used were 2% citric acid and silver, Ag-TtO₂ and Zn-Cu nanoparticles, and licorice extracts.

[0074] Membrane Fabrication. The membrane fabrication process was a roll-to-roll system, where a textile material was wound from one side to the other side and the nanofiber layer was laminated on the textile during the winding process. The thickness of the nanofiber layers was controlled by controlling the winding speed.

Characterization of Representative Samples

[0075] To investigate the feasibility of using the disclosed nanofibrous polymer membranes in facemasks and respirators, the moiphology, fiber diameter, filtering efficiency, porosity, wettability, mechanical strength, and antiviral activity of representative samples of an embodiment of the disclosed nanofibrous polymer membrane was characterized. [0076] Nanofibrous polymer membranes were characterized using scanning electron microscopy (SEM) imaging. FIG. 1 shows representative SEM images of an embodiment of the disclosed nanofibrous polymer membrane. The larger images show 2000X magnification, while each inset shows the respective 5000X magnification image. As shown in FIG. 1, the internal and external surfaces of each nanofiber membrane display consistent morphology between samples. In addition, the nanofibrous membranes show good orientation and are tree of breading, splitting, and other undesirable morphological features. [0077] FIG. 2 shows fiber diameter measurements and distribution for representative samples of an embodiment of the disclosed nanofibrous polymer membrane. The average fiber diameter of representative samples was 0.224 pm, with a median fiber diameter of 0.210 pm and a standard deviation of 0.196. The average orientation was 79°, and the area coverage was 16%.

[0078] FIG. 3 shows pore size distribution for representative samples of an embodiment of the disclosed nanofibrous polymer membrane as determined by mercury porosimeter analysis. The mean pore diameter was found to be 0.0025 pm.

[0079] FIG. 4 shows average porosity and the distribution of mean porosity for representative samples of an embodiment of the disclosed nanofibrous polymer membrane. The average porosity as determined by gravimetric measurements was shown to be distributed around a center point of 78.5%. As shown in FIG. 4, all samples showed consistent porosity in the range of 75% to 83%, High porosity of the membrane is a critical requirement to increase the breathabiiity of a facemask or filter made from the membrane. [0080] FIG. 5 shows mechanical tensile strength test results tor representative samples of an embodiment of the disc l osed nanofibrous polymer membrane.

[0081] A representative sample of an embodiment of the disclosed nanofibrous polymer membrane was also tested for filtration efficiency. The observed efficiency was 99.61% for 30 L/min, with a pressure loss of 1.265 mbar, and 99.85% for 95 L/min, with a pressure loss of 4.3 mbar. [0082] Table 1 shows a summary of test results for representative samples of an embodiment of the membrane.

[0083] Representative samples of an embodiment of the membrane did not degrade after washing with water or ethanol. By contrast, a sample of a melt-blown membrane showed a significant decrease in filtration efficiency after washing with ethanol.

[0084] A comparison between a representative sample of an embodiment of the disclosed nanofibrous polymer membrane and a typical melt-blown membrane is shown in Table 2.

[0085] The filtration efficiency and observed pressure drop for various membrane samples is shown in Table 3.

FiGs. 6-12 show test results for filtration efficiency, flammability, and antiviral and antimicrobial properties for representative samples of an embodiment of the disclosed nanofihrous polymer membrane.

[0087] FIG. 13 shows how filtration efficiency is affected by the flow rate of aerosols through the membrane.

[0088] FIG. 14 shows how the pressure drop across the membrane, which is a measure of breathability of the membrane, is affected by the flow rate of aerosols through the membrane. [0089] The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention disclosed herein. Although the various inventive aspects are disclosed in the context of one or more illustrated embodiments, implementations, and examples, it should be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. It should be also understood that the scope of this disclosure includes the various combinations or sub-combinations of the specific features and aspects of the embodiments disclosed herein, such that the various features, modes of implementation, and aspects of the disclosed subject matter may be combined with or substituted for one another. The generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0090] All references cited are hereby expressly incorporated herein by reference.

Claims

CLAIMS What is claimed is:

1. An eleclrospun polymer nanofibrous membrane having a high filtration efficiency comprising polyvinylidene fluoride, one or more Tecophilic™ thermoplastic polyurethanes, or a blend of polyvinylidene fluoride and one or more Tecophilic™ thermoplastic polyurethanes, wherein the membrane is treated with one or more anti- pathogenic agents.

2. The membrane of Claim 1, wherein the one or more anti-pathogenic agents comprise an antiviral agent.

3. The membrane of Claim 2, wherein the antiviral agent is selected from the group consisting of graphene, nanoparticles, nanocomposites, multivalent metallic ions, and extracts from natural products.

4. The membrane of Claim 2, wherein the antiviral agent is coated on the surface of the membrane.

5. The membrane of Claim 3, wherein the antiviral agent is selected from the group consisting of silver nanopaiticles and zinc nanoparticles.

6. The membrane of Claim 3, wherein the antiviral agent comprises a silver- doped titanium dioxide nanomaterial.

7. The membrane of Claim 3, wherein the antiviral agent comprises multivalent

Cu²+ or Zn²+ cations.

8. The membrane of Claim 3, wherein the antiviral agent comprises a licorice extract.

9. The membrane of Claim 1, wherein one or more metal-organic frameworks are impregnated into the membrane.

10. The membrane of Claim 5, wherein the one or more metal-organic frameworks comprise a zirconium metal-organic framework.

11. The membrane of Claim 1, wherein the membrane is eleclrospun from a polymer solution that includes a surfactant

12. The membrane of Claim 11, wherein the surfactant is selected from the group consisting of cetrimonium bromide (CTAB), lauramidopropyl betaine (LAPB), and alpha olefin sulfonate (AOS).

13. The membrane of Claim 1, wherein the membrane is electrospun from a polymer solution that includes a salt

14. The membrane of Claim 13, wherein the salt is selected from the group consisting of alkali metal halides.

15. The membrane of claim 2, wherein the membrane comprises multiple integrated layers with distinguishable microstructure characteristics.

16. The membrane of Claim 15, wherein the membrane is composed of three layers including a first and third layer having equal pore size separated by a second layer having a different pore size.

17. The membrane of Claim 16, wherein the first and third layers have a larger pore size and the second layer has a smaller pore size.

18. The membrane of Claim 15, wherein the membrane ½ composed of three layers with three different pore sizes.

19. The membrane of Claim 17, wherein the mechanical integrity and binding forces between layers of the membrane is enhanced by electrospraying short fibers prior to electrospinning a subsequent layer of the membrane or by electrospinning wet fibers by decreasing the screen distance to generate a “tacky surface” prior to electrospinning a subsequent layer of the membrane.

20. The membrane of Claim 15, wherein the membrane is formed by winding a textile material roll comprising a textile material from a first side to a second side and then performing the following steps in order. a. electrospinning one or more first nanofiber layers on the first side of the textile material at a first winding speed; b. flipping the textile material roll; and c. electrospinning one or more second nanofiber layers on the second side of the textile material at a second winding speed; wherein the first winding speed is different from the second winding speed,

21. The membrane of Claim 15, wherein the membrane is formed by winding a textile material roll comprising a textile material from a first side to a second side and then performing the following steps in order. a. electrospinning one or more first nanofiber layers on the first side of the textile material at a first winding speed; and b. electrospinning one or more second nanofiber layers on the first side of the textile material at a second winding speed; wherein the first winding speed is different from die second winding speed.

22. The membrane of Claim 15, wherein the membrane is formed by winding a textile material roll comprising a textile material from a first side to a second side and then performing the following steps in order: a. electrospinning one or more first nanofiber layers on the first side of the textile material at a first winding speed; b. electrospinning one or more second nanofiber layers on the first side of the textile material at a second winding speed; c. flipping the textile material roll; and d. electrospinning one or more third nanofiber layers on the second side of the textile material at a third winding speed; wherein the first winding speed is different from the second winding speed.

23. An electrospun polymer nanofibrous membrane having a high filtration efficiency comprising polyvinylidene fluoride, one or more Teeophilic™ thermoplastic polyurethanes, or a blend of polyvinylidene fluoride and one or more Teeophilic™ thermoplastic polyurethanes, wherein one or more anti-pathogenic agents is impregnated into the membrane.

24. The membrane of Claim 23, wherein one or more metal-organic frameworks are impregnated into the membrane.

25. The membrane of Claim 24, wherein the one or more metal-organic frameworks comprise a zirconium metal-organic framework.

26. The membrane of Claim 23, wherein the membrane is electrospun from a polymer solution that includes a surfactant.

27. T he membrane of Claim 26, wherein the surfactant is selected from the group consisting of cetrimonium bromide (CTAB), lauramidopropyl betaine (L APB), and alpha olefin sulfonate (AOS).

28. The membrane of Claim 23, wherein the membrane is electrospun from a polymer solution that includes a salt

29. The membrane of Claim 28, wherein the salt is selected from the group consisting of alkali metal halides.

30. The membrane of Claim 23, wherein the membrane comprises multiple integrated layers with distinguishable microstructure characteristics.

31. The membrane of Claim 30, wherein the membrane is composed of three layers including a first and third layer having equal pore size separated by a second layer having a different pore size.

32. The membrane of Claim 31, wherein the first and third layers have a larger pore size and the second layer has a smaller pore size.

33. The membrane of Claim 30, wherein the membrane ½ composed of three layers with three different pore sizes.

34. The membrane of Claim 32, wherein the mechanical integrity and binding forces between layers of the membrane is enhanced by electrospraying short fibers prior to eleclruspinning a subsequent layer of the membrane or by electrospinning wet fibers by decreasing the screen distance to generate a “tacky surface” prior to electrospinning a subsequent layer of the membrane.

35. An electrospun polymer nanofibrous membrane having a high filtration efficiency comprising polyvinylidene fluoride, one or more Tecophilic™ thermoplastic polyurethanes, or a blend of polyvinylidene fluoride and one or more Tecophilic™ thermoplastic polyurethanes, wherein one or more metal-organic frameworks is impregnated into tiie membrane.

36. The membrane of Claim 22_» wherein the one or more metal-organic frameworks comprise a zirconium metal-organic framework.