WO2017213593A2

WO2017213593A2 - Gleanable and sunlight-tolerant multifunctional nanofibrous filter for water and air filtration and fabrication process of nanofibrous filter thereof

Info

Publication number: WO2017213593A2
Application number: PCT/TH2017/000045
Authority: WO
Inventors: Varol INTASANTA; Nakarin SUBJALEARNDEE
Original assignee: National Science And Technology Development Agency
Priority date: 2016-06-10
Filing date: 2017-06-02
Publication date: 2017-12-14
Also published as: KR20190015563A; WO2017213593A8; CN109789352A; WO2017213593A3

Abstract

This invention related to multifunctional nanofibrous filters for water and air microfiltration able to be reused several times and their fabrication process. The described nanofibrous filters have antibacterial, water repellent, anti-UV functions with high flexibility and tensile strength. The filters are able to be cleaned and dried under sunlight several times. The filter according to this invention can be fabricated by solution-based processing from specific chemical components via needle-based electrospinning, nanospider electrospinning or forced/centrifuge spinning. The nanofibrous filters have small pores, high surface area and porosity and show high efficiency toward microparticle filtration.

Description

GLEANABLE AND SUNLIGHT-TOLERANT MULTIFUNCTIONAL NANOFIBROUS FILTER FOR WATER AND AIR FILTRATION AND FABRICATION PROCESS OF

NANOFIBROUS FILTER THEREOF

FIELD OF THE INVENTION Chemistry related to multifunctional, antibacterial, water repellent, UV protection, high strength, flexible and high tensile strength nanofibers and nanofibrous filter for water and air filtration which are cleanable and resistant to sunlight.

DISCLOSURE OF THE INVENTION

This invention is the development of multifunctional, antibacterial, water repellent, UV resistant, high strength and flexbile nanofibers and nanofibrous filter for water and air filtration able to be cleaned by water and is resistant to sunlight. The described nanofibers and nanofibrous filter are different from other nanofibers and nanofibrous filters in terms of antibacterial, water repellent, UV resistant, high strength and flexible properties. The described high-surface area and higly-porous nanofibers can be fabricated by solution-based processing from both of needle-based electrospinning, nanospider electrospinning and forced/centrifuge spinning.

BACKGROUND OF THE INVENTION

Environmental pollution from microparticles and microbial results in increasing medical, public health and social investment to fight against it, so development of the purification technology is a crucial issue in the present situation.

From the patent database and literature review, no record is found to be similar to this invention as shown below;

COLLOID AND INTERFACE SCIENCE Volume: 428 Page 41-48: Super amphiphobic nanofibrous filters for effective filtration of fine particles. The literature concerned fabrication process of water repellent nanofibers and nanofibrous filter. The chemical reactants were water- repellent chemical functionalized polyurethane and polyacrylonitrile. This fabrication process was electrospinning from solution. The output was water and oil repellent nanofibrous filter.

MEMBRANE SCIENCE Volume 448 Page 151-159: Water-soluble polyvinylpyrrolidone nanofilters manufactured by electrospray-neutralization technique. The literature concerned the fabrication process of water-soluble nanofibers and nanofibrous filter for small paticle filtration. The chemical reactant was polyvinylpyroridone in solvent such as DMF, water and ethanol. The fabrication process was electrospinning from solution. The output was water-soluble nanofibers and nanofibrous filter for microfiltration. COLLOID AND INTERFACE SCIENCE Volume 398 Page 240-246: Tortuously structured polyvinyl chloride/polyurethane fibrous filters for high-efficiency fine particulate filtration. The literature concerned the fabrication of anti-scraching nanofibers and nanofibrous memrbane. The chemical reactants were polyurethane and polyvinylchloride in solvent such as DMF and THF. The fabrication process was electrospinning from solution. The output was anti-scratching nanofibrous memrbane for microfiltration.

SEPARATION AND PURIFICATION TECHNOLOGY Volume 126 Page 44-51: Multilevel structured polyacrylonitrile/silica nanofibrous filters for high-performance air filtration. The literature concerned the fabrication of nanofibers and nanofibrous filter for small particle filtration. The chemical reactants were polyacelonitrile and silica nanoparticles coated with water repellent chemical in solvent such as DMF and THF. The fabrication process was layer-by-layer electrospinning. The output was nanofibrous filter for microfiltration.

COLLOID AND INTERFACE SCIENCE Volume 457 Page 203-211 : Efficient and reusable polyamide-56 nanofiber/nets filter with bimodal structures for air filtration. The literature concerned the fabrication of nanofibrous filter covered with nanonets for small particle filtration. The reactants were polyamide and silica nanoparticles coated with water repellent chemical in solvent such as formic and acetic acid. The fabrication process was electrospinning from solution. The output was nanonet-covered nanofibrous filter for microfiltration.

Patent number US20100285081A1 in a topic of "Antimicrobial fiber having diameter useful for making article e.g. nanocomposite, sensor and filtration filter, comprises electroprocessed blend of polymer, antimicrobial chemical and cross-linker". This patent concerned antibacterial fiber fabrication or fiber fabrication and coating with the antibacterial chemical compounds by electrospinning process that composed of at least one polymer and one crosslinking chemical.

Patent number EP2476798B1 in a topic of "Textile material endowed with antifouling properties obtained by coating textile support with layer of antifouling composition containing crosslinkable polymer, drying the composition and subjecting to crosslinking, used in e.g. ropes". This patent concerned the textiles property enhancement by coating with anti-drug chemicals which composed of at least one crosslinker polyer and one hydrolase enzyme.

Patent number US9125811B2 in a topic of "Nanofiber lamination sheet comprises layer of nanofibers comprising water-insoluble polymeric compound and layer of water-soluble polymeric compound containing cosmetic component or active drug substance". This patent concerned thin nanofibers which composed of hydrophobic and hydrophilic polymer layers for cosmetic actives storage. The output was thin films for rash and melasma reduction.

Patent number JP2014185081A in a topic of "Ultraviolet-absorption composition used for external preparation, cosmetics, coating composition and composite material, comprises urocanic acid and chitin nanofiber". This patent concerned UV absorbed nanofibers which composed of urocanic acid and chitin nanofibers. The output was chitin nanofibers able to absorb UV light and inherited high physical strength.

From the journal and patent database searching, no record represented the same material processing or chemical compositions as those in this invention which concerned the development of multifunctional, water-resistant, sunlight resistant, washable, high tensile strength and flexible nanofibers and nanofibrous filter by electrospinning prccess from the unique combination of chemical compounds which were different from those in other invention.

FIGURE CAPTIONS: Figrue 1 Pictures of nanofiber's physical characters of example 1 (a), example 2 (b), example 3 (c) and example 4 (d). Water repellent function evaluation after nanofiber fabrication (1), after fabrication and immersion in water (2), after fabrication and curing at 140 °C (3) and after fabrication, curing at 140 °C and immersion in water (4);

al) Nanofibrous filter of example 1 after fabrication.

a2) Nanofibrous filter of example 1 after fabrication and immersion in water.

a3) Nanofibrous filter of example 1 after fabrication and curing at 140 °C.

a4) Nanofibrous filter of example 1 after curing and immersion in water,

bl) Nanofibrous filter of example 2 after fabrication.

b2) Nanofibrous filter of example 2 after fabrication and immersion in water.

b3) Nanofibrous filter of example 2 after fabrication and curing at 140 °C.

b4) Nanofibrous filter of example 2 after curing and immersion in water,

cl) Nanofibrous filter of example 3 after fabrication.

c2) Nanofibrous filter of example 3 after fabrication and immersion in water.

c3) Nanofibrous filter of example 3 after fabrication and curing at 140 °C.

c4) Nanofibrous filter of example 3 after curing and immersion in water,

dl) Nanofibrous filter of example 4 after fabrication.

d2) Nanofibrous filter of example 4 after fabrication and immersion in water.

d3) Nanofibrous filter of example 4 after fabrication and curing at 140 °C.

d4) Nanofibrous filter of example 4 after curing and immersion in water. Figure 2 Table of air permeability of examples 1 , 2, 3 and 4. Figure 3 Table of antibacterial testing result according to the AATCC TM 100:2004 and AATCC TM147:2011 standard testing of examples 1, 2, 3 and 4.

Figure 4 Table of M. tuberculosis cell pictures from PI staining and SYT09 staining on a commercial cellulose and nanofibrous filter of examples 1, 2, 3 and 4. Figure 5 Pictures of nanofibers' physical characteristics within the nanofibrous filter from examples 1, 2, 3 and 4 from UV protection efficiency testing;

al) Nanofibrous filter from example 1 after fabrication/ before UV exposure.

a2) Nanofibrous filter from example 1 after UV exposure,

bl) Nanofibrous filter from example 2 after fabrication/ before UV exposure.

b2) Nanofibrous filter from example 2 after UV exposure.

cl) Nanofibrous filter from example 3 after fabrication/before UV exposure.

c2) Nanofibrous filter from example 3 after UV exposure,

dl) Nanofibrous filter from example 4 after fabrication/before UV exposure.

d2) Nanofibrous filter from example 4 after UV exposure. Figure 6 Table of ultraviolet protection factor (UPF factor), UVA and UVB of nanofibrous filter in wet and dry conditions from examples 1, 2, 3 and 4.

Figure 7 Stress-strain curves of nanofibrous filters from examples 1, 2, 3 and 4 in tensile strength testing whereas;

al) Nanofibrous filter before UV exposure of example 1.

a2) Nanofibrous filter after UV exposure of example 1.

bl) Nanofibrous filter before UV exposure of example 2.

b2) Nanofibrous filter after UV exposure of example 2.

cl) Nanofibrous filter before UV exposure of example 3.

c2) Nanofibrous filter after UV exposure of example 3.

dl) Nanofibrous filter before UV exposure of example 4.

d2) Nanofibrous filter after UV exposure of example 4.

Figure 8 Table of tensile strength and elongation percentage of filters from examples 1, 2, 3 and 4.

Figure 9 Scheme and pictures of three types of crosslinking characterisics in filters whereas;

a) The network crosslinking type.

b) The bimodal-diameter crosslinking type.

c) The crossover-of-nanofiber crosslinking type. Figure 10 SEM images of crosslinking characteristics in the nanofibrous filter from examples 2, 3 and 4 whereas;

al) Top view of network crosslinking from example 2.

a2) Rear view of network crosslinking from example 2.

a3) Cross section view of network crosslinking from example 2.

bl) Top view of bimodal-diameter crosslinking type from example 3.

b2) Rear view of bimodal-diameter crosslinking type from example 3.

b3) Cross section view of bimodal-diameter crosslinking type from example 3.

cl) Top view of crossover-of-nanofiber crosslinking type from example 4.

c2) Rear view of crossover-of-nanofiber crosslinking type from example 4.

c3) Cross section view of crossover-of-nanofiber crosslinking type from example 4.

Figure 11 Scheme of crosslinking meachnism between PVA and glutaraldehyde molecules within the nanofibrous filter.

Figure 12 Infrared spectroscopy (FT-IR) of nanofibrous filter (a) before and (b) after exposure to weathering effect for examples 1, 2, 3 and 4.

Figure 13 Table of quantative analysis for comparison of ratio between O-H bonding and C-H bonding within nanofibers by infrared spectroscopy (FT-IR).

DETAILED DESCRIPTION OF THE INVENTION

Multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and resistant to sunlight with the fabrication process of the described nanofibrous filter thereof

Multifunctional nanofibrous filters according to this invention are nanofibrous filters from specific combination of crosslinker, water repellent, anti-bacterial and anti-UV chemicals for enhanced chemical and physical properties. The described filters consist of different types of crosslinking characters within and among nanofibers to form network crosslinking, bimodal-diameter crosslinking and crossover-of-nanofiber crosslinking types of structures.

For network crosslinking type, the nanofiber's diameter is in a range of 265 ± 44 nm with more porosity than the other types of crosslinking. The amount of porosity is in a range of 74 ± 20 % of total volume and is more than that in the other crosslinking as estimated from 25 μπι² size sampling. Moreover, pores' diameter is in a range of 55 ± 15 nm. From the side view, the pores of the crosslinked nanofibers appeared in circular shape.

For crossover-of-nanofiber crosslinking types, the nanofibers' diameter is in the range of 171 ± 53 nm. This crosslinking type has lower amount of porosity than the network crosslinking type but higher than the bimodal-diameter crosslinking type. In addition, this crosslinking type contains porosity of 48 ± 20% as estimated from the sampling area of 25 μιη² in size with pores' diameter in the range of 170 ± 19 nm.

For the bimodal-diameter crosslinking type, the average nanofibers' diameter is in the range of 273 ± 125 nm, with the lowest porosity with respect to the other two tyeps. This crosslinking type has porosity in the range of 34 ± 20% as estimated from sampling area of 25 μτ^η2 in size with pores' diameter in the range of 83 ± 21 nm.

These different crosslinking types are resulted from different chemical composition and fabrication process.

The multifunctional nanofibrous filter according to this invention on the 1 unit of area composes of functional polymer for 0.1-50%, antibacterial chemical for 0.01-20%, anti-UV chemical for 0.01-20% and may have water repellent chemical for 0.01-50% or crosslinking chemical for 0.01- 50%.

The multifunctional nanofibrous filters according to this invention have tensile strength enhancement and water repellent function by crosslinker and water repellent chemical in nanoscale. In addition, antibacterial and anti-UV functions are added by antibacterial and anti-UV chemical incorporation, so the filter can be cleaned and recycled several times by water and exposed to sunlight or UV light for drying or cleaning purposes. The nanofibrous filters can be fabricated from specific chemical composition through solution based processing such needle-based electrospinning, nanospider electrospinning, or forced/centrifuge spinning. The presence of nanosized fibers result in small pores, high surface area and high porosity.

The nanofibrous filter fabrication process according to this invention composed of; a) Solution mixture preparation

al) Polymer solution in water: The polymer solution was prepared by adding functional polymer into water under stirring at 70-90 °C (The proper temperature was 85 °C) for

120-180 minutes. Then the prepared polymer solution was kept for the next process (Step a2-a4). The polymer can be that with hydroxyl group, amine group, nitrile group or carboxyl group along the main hydrocarbon chain. The polymer is selected from the group consisting of polyacrylonitrile, polyvinyl pyroridone, polyvinyl alcohol, polyhydroxypropyl-metachrylate, polyhydroxyethyl-metachrylate, polyglycerol- metachelate and combinations thereof.

a2) Polymer solution in water containing antibacterial and anti-UV complex: The solution mixture can be prepared by mixing the antibacterial complex with the the polymer solution from al) under stirring. Then anti-UV complex was added into the previous solution. a3) Polymer solution in water containing antibacterial/anti-UV complexes and nanoparticles: The solution mixture can be prepared by mixing the antibacterial nanoparticles with solution from a2) under stirring. Then the anti-UV nanoparticles was added into the previous solution mixture. Finally, the polymer solution contained antibacterial/anti-UV complexes and nanoparticles.

The solution from a3) further comprising water repellent complex: The solution can be prepared by adding the water repellent compound in the solution mixture (From step a3).

The antibacterial chemicals is selected from the group consisting of silver nitrate, silver nanoparticles and combinations thereof. In addition, the anti-UV chemicals is selected from the group consisting of zinc acetate, zinc oxide nanoparticles and combinations thereof while the water repellent chemical is fluorocarbon.

b) The solution from a) was sonicated by a sonicator for 30 minutes prior to nanofiber fabrication in the next step.

The solution from b) further comprising crosslinkers by adding the crosslinking chemicals in the solution from b) under stirring for at least 10 minutes prior to nanofiber fabrication in the next step. The crosslinking chemical is selected from the group consisting of polyurethane, glutaraldehyde and glutaraldehyde solution and combinations thereof.

c) Nanofiber fabrication: The solution from b) is fabricated into nanofibrous filter via solution-based processing by needle-based electrospinning, nanospider electrospinning or forced/centrifuge spinning. The best fabrication technique was the nanospider electrospinning.

The optimised condition for needle-based electrospinning can be achieved by setting the tip-to-ground distance at 10-20 cm, voltage of 10-20 kV and solution flow rate at 0.12 ml/hour.

The optimised condition for nanospider electrospinning can be achieved by setting the distance between electrode-to-ground distance at 18-20 cm, voltage of 55 kV and electrode's rotating speed at 5 rpm.

A part of the nanofibrous filter was kept for water repellent testing and the rest will be kept for curing in the next process.

d) The nanofibrous filter from c) was heated at 100-140 °C for 60-120 minutes. The resulted multifunctional nanofibrous filter having antibacterial, anti-UV, water repellent, high tensile strength properties and flexibility suitable for water and air filtration. In addition, the filter can be cleaned by water and is resistant to sunlight, so it can be recycled several times which are unique from other inventions.

In the next section, exemplary inventions are described but not limited to the examples given.

EXAMPLES

In this example, polyvinyl alcohol and glutaraldehyde solution are selected as representatives of functional polymer and crosslinker, respectively.

Example 1: Tensile strength enhanced nanofibrous filter by a crosslinking chemical.

Nanofibrous filter fabrication process according to the example 1 composed of;

a) Solution mixture preparation: PVA solution was prepared by adding PVA into water in a ratio of 1 : 10 under magnetic stirring at 70-90 °C (The proper temperature was 85 °C) for 120-180 minutes. Then the prepared PVA solution was kept for the next process.

b) The crosslinker, glutaraldehyde solution, was mixed with the PVA solution in a ratio of 1 : 5 under magnetic stirring for at least 10 minutes. Then the solution mixture was kept for the fabrication process.

The solution mixture formular for nanofibrous filter fabrication in the example 1 composed of chemicals as stated below;

Polyvinyl alcohol 7.1% by solution mixture weight Glutaraldehyde solution 14.3% by solution mixture weight

Water 78.6% by solution mixture weight c) Fiber fabrication process: The solution from b) was fabricated into nanofibrous filter via nanospider machine by applying the electrode-to-ground distance at 18-20 cm, voltage of 55 kV and electrode's rotating speed at 5-8 rpm. After fabrication, the resulted nanofibers were overlapped which resulted in nanofibrous filter. A part of the nanofibrous filter was kept for water repellent testing and the rest for curing in the next process.

d) The nanofibrous filter from c) was cured at 100-140 °C for 60-120 minutes. Then the nanofibrous filter was characterized in terms of water repellency, air permeability, antibacteria, UV and tensile strength. In addition, the physical and chemical crosslinking characteristics of the filter were characterized by scanning electron microscope (SEM) as described below;

- Water repellency: The test was performed 2 times after fabrication (Step c) and after curing (Step d) by immersing the nanofibrous filter in water for 5 minutes then observing physical character by SEM.

- Air permeability: The test was performed with the cured nanofibrous filter by air permeability tester machine (M021 A). Antibacteria property: the test was performed according to the standard testing method

1. AATCC TM 100:2004 standard testing by mersuring bacteria reduction percentage of gram positive bacteria (Staphylococcus aureus) and gram negative beacteria {Klebsiella pneumonia).

2. AATCC TM 147:2011 standard testing by measuring the bacteria growth rate on agar plate and evaluating the size of clear zone around the testing sample. The same tyes of bacteria as the AATCC TM 100:2004 were employed in this standard testing method.

3. Anti-tuberculosis (Mycobacterium tuberculosis H37Ra, TB) property by measuring the living TB cell with confocal microscope on the filter. The green dots represented living TB cells while the red dots represented the dead cells. The experiment was performed in comparison with the commercial cellulose filter with 0.45 micron diameter (Satorius filter).

Anti-UV property: The test was performed by measuring the ultraviolet protection factor (UPF) according to the AATCC 183:2010 standard testing method and the UVA and UVB permeability percentage in a frequency range between 315-400 nm and 280-315 nmm, respectively, in both dry and wet filter conditions. In addition, the SEM characterization was performed in order to observe the physical characteristics of nanofibers before and after UV irradiation exposure.

Tensile strength: The test was performed by measuring the tensile strength of nanofibers before and after UV irradiation according the ASTM G 154:2006 standard (Drying at temperature 60 °C for 480 minutes before condensation at 50 °C for 240 minutes) by Instron Model 5566 machine. Then the nanofibrous filters were cut into 1 inch x 2 inch before testing with the tension speed of 100 mm/minute.

Chemical and physical characterization of crosslinking structure: The test was performed by observing the crosslinking character as well as quantitative and qualitative ratio between O-H and C-H bonding by SEM and FT-IR.

Result: After nanofiber fabrication from the composition of PVA and glutaraldehyde solution, the nanofibers structure was able to maintain the original shape after curing at 140 °C. After water repellent property testing by immersion the filter in water, the physical characteristics of nanofibers was transformed partially as evident by reduction of porosity and collapsed void within the filter (Figure 1, al-a4). After air permeability testing, the result of 0.22 cm³/sec/cm² showed that air can flow through the filter according to the example 1 (Figure 2). For antibacterial testing according to the AATCC standard, the filter from the example 1 showed low antibacterial property as bacteria could grow on the testing plate (Figure 3). For anti-TB testing, the living TB cells (Green dots) were observed in high numer on the filter similar to those on the cellulose control filter (Figure 4). After UV irradiation, the majority of nanofibers were merged and transformed into a thin solid film (Figure 5, al and a2). The UPF of the filter was measured in dry and wet conditions. The UPF of the filter in wet condition was measured at rating of 3 and in dry condition 7. The UVA permeability of the filter in dry condtion was 23.1% and increased to 43.7% in the wet condition. The UVB permeability of the filter in the dry condition was 12.4% and increased to 27.2% in wet condition (Figure 6). For tensile strength testing before and after UV irradiation, the result showed that the UV irridated filter had significantly lower tensile strength and elongation percentage than non-UV irradiated filter. Before UV irradiation, the elongation percentage of the filter was 54.45% and tensile strength of 5.27 N. After UV irradiation, the elongation percentage and tensile strength were reduced to 21.62% and 0.44 N, respectively. From subsequent calculations, the elongation percentage was reduced for 60.20% while the tensile strength reduced for 91.65%, showing the decrease in flexibility and strength

(Figure 7 and 8). There was no crosslinking characterization by SEM because the filter significanty decomposed after UV irradiation. However, the infrared spectroscopy characterization showed the increase of the absorbance ratio between O-H and C-H bonding from 1.18 to 1.55 which implied the decrease of crosslinking efficiency (Figure 12 and 13). Example 2: Tensile strength enhanced nanofibrous filter by a crosslinker, antibacterial and anti-UV chemicals.

Nanofibrous filter fabrication process according to the example 2 composed of;

a) Solution mixture preparation

al) PVA solution in water: The PVA solution was prepared by adding PVA into water in a ratio of 1 : 10 under magnetic stirring at 70-90 °C (The proper temperature was 85 °C) for

120-180 minutes. Then the prepared PVA solution was kept for the next process.

a2) PVA solution in water containing antibacterial and anti-UV complex: Silver nitrate was added into the PVA solution from al) in a ratio of 0.1 : 10 of PVA solution under magnetic stirring. Then zinc acetate was added into the solution mixture in a ratio of 0.1 : 10 of PVA solution.

a3) PVA solution in water containing antibacterial and anti-UV complex and nanoparticles:

Silver nanoparticles were added into the solution from a2) in a ratio of 0.05: 10 of PVA solution under magnetic stirring. Then zinc oxide nanoparticles were added into the solution mixture in a ratio of 0.05: 10 of PVA solution.

b) The solution from a) was sonicated by a sonicator for 30 minutes. c) The crosslinker, glutaraldehyde solution, was mixed with the PVA solution from b) in a ratio of 1 : 5 under magnetic stirring for at least 10 minutes. Then the solution mixture were kept for the fabrication process.

The solution mixture for nanofibrous filter fabrication in the example 2 composed of chemical as stated below;

Polyvinyl alcohol 7% by solution mixture weight

Glutaraldehyde solution 14% by solution mixture weight

Silver nitrate 0.7% by solution mixture weight

Silver nanoparticles 0.3% by solution mixture weight Zinc acetate 0.7% by solution mixture weight

Zinc oxide nanoparticles 0.3% by solution mixture weight

Water 77% by solution mixture weight d) Fiber fabrication process: The solution from c) was fabricated into nanofibrous filter via nanospider machine by applying the electrode-to-ground distance at 18-20 cm, voltage of 55 kV and electrode's rotating speed at 5-8 rpm. After fabrication, the resulted nanofibers were overlapped which resulted in nanofibrous filter. A part of the nanofibrous filter was kept for water repellent testing and the rest for curing in the next process.

e) The nanofibrous filter from d) was cured at 100-140 °C for 60-120 minutes. Then the nanofibrous filter was characterized as per water repellency, air permeability, antibacteria, antiUV functions and tensile strength. In addition, the physical and chemical crosslinking characteristics of the filter was characterized by scanning electron microscope (SEM) as described below;

Water repellency: The test was performed 2 times after fabrication (Step d) and after curing (Step e) by immersing the nanofibrous filter in water for 5 minutes then observing the physical characteristics by SEM.

- Air permeability: The test was performed with the cured nanofibrous filter by air permeability tester machine (M021A).

- Antibacteria property: the test was performed according to the standard testing method

1. AATCC TM 100:2004 standard testing by mearsuring bacteria reduction percentage of gram positive bacteria (Staphylococcus aureus) and gram negative beacteria (Klebsiella pneumonia).

2. AATCC TM 147:2011 standard testing by measuring the bacteria growth rate on agar plate and evaluating the size of clear zone around the test sample. The same types of bacteria as the AATCC TM 100:2004 were employed in this standard testing method.

3. Anti-tuberculosis (Mycobacterium tuberculosis H37Ra, TB) property by measuring the living TB cell with confocal microscope on the filter. The green dots represented living TB cells while the red dots represented the dead cells. The experiment was performed in comparison with the commercial cellulose filter with 0.45 micron diameter (Satorius filter). Anti-UV property: The test was performed by measuring the ultraviolet protection factor (UPF) according to the AATCC 183:2010 standard testing method and the UVA and UVB permeability percentage in a frequency range between 315-400 nm and 280-315 nm, respectively, in both dry and wet filter conditions. In addition, the SEM characterization was performed in order to obsrve the physical characteristics of nanofibers before and after UV irradiation exposure.

Tensile strength: The test was performed by measuring the tensile strength of nanofibers before and after UV irradiation according the ASTM G 154:2006 standard (Drying at temperature 60 °C for 480 minutes before condensation at 50 °C for 240 minutes) by Instron Model 5566 machine. Then the nanofibrous filter was cut into 1 inch x 2 inch before testing with the tension speed of 100 mm/minute.

- Chemical and physical characterization of crosslinking structure: The test was performed by observing the crosslinking character as well as quantitative and qualitative ratio between O-H and C-H bonding by SEM and FT-IR.

Result: After nanofiber fabrication from the solution mixture between PVA solution, silver nitrate, silver nanoparticles, zinc acetate, zinc oxide nanoparticles and glutaraldehyde solution according to the example 2, the nanofibers showed the network crosslinking type. After curing at 100-140 °C, the nanofibers were able to maintain their original shape. On the 1 unit of area, the filter composed of PVA for 43.47%, antibacterial chemical for 6.53%, anti-UV chemical for 6.53% and glutaraldehyde for 43.47%. After water repellent property testing by immersing the filter in water, the physical characteristics of nanofibers was transformed partially as evident by the reduction of porosity and collapsed void within the filter (Figure 1, bl-b4). After air permeability testing, the result of 1.06 cm³/sec/cm² showed that air can flow through the filter (Figure 2). For antibacterial testing according to the AATCC standard, the filter from the example 2 showed high antibacterial property as the bacteria could not grow on the testing plate and the clear zone of gram positive bacteria was observed higher than gram negative bacteria (Figure 3). For anti-TB testing, the filter had the anti-TB property in comparison with the example 1 and control cellulose filter by observing both of living (Green dots) and dead (Red dots) TB cells on the filter (Figure 4). After UV irradiation, the nanofibers were merged and transformed partially but still showed the original form of nanofiber characteristics (Figure 5, bl and b2). The UPF of the filter was measured in dry and wet conditions. The UPF of the filter in wet condition was measured at rating of 32 and in dry condition 50+. The UVA permeability of the filter in dry condition was 0.2% and increased to 2% in wet condition. The UVB permeability of the filter in dry condition was 0.2% and increased to 2.5% in wet condition (Figure 6). For tensile strength testing before and after UV irradiation, the result showed that the UV irradiated filter had significantly higher tensile strength and elongation percentage than non-UV irradiated membrane. Before UV irradiation, the elongation percentage of the filter was 31.11% and tensile strength of 2.98 N. After UV irradiation, the elongation percentage and tensile strength were increased to 35.00% and 10.67%, respectively. From subsequent calculations, the elongation percentage was increased for 11.11% while the tensile strength was increased for 72.07% showing the increase in flexibility and strength (Figure 7 and 8). For crosslinking characterization by SEM, this example showed the networking crosslinking type which had the nanofiber's diameter in a range of 265 ± 44 nm and observed the higher amount of porosity than example 3 and 4 (Figure 9a and 10, al-a3). The amount of porosity is in a range of 74 ± 20 % of total volume and is more than that in the other crosslinking as estimated from 25 μπι² size sampling. After infrared spectroscopy characterization, the absorbance ratio between O-H and C-H bonding increased slightly after UV irradiation which implied the maintaining of crosslinking characteristics (Figure 12 and 13).

Example 3: Antbacterial, anti-UV and water repellent nanofibrous filter.

Nanofibrous filter fabrication process according to the example 3 composed of;

a) Solution mixture preparation

al) PVA solution in water: PVA solution was prepared by adding PVA into water in a ratio of 1 : 10 under magnetic stirring at 70-90 °C (The proper temperature was 85 °C) for 120- 180 minutes. Then the prepared PVA solution was kept for the next process. a2) PVA solution in water containing antibacterial and anti-UV complex: Silver nitrate was added into the PVA solution from al) in a ratio of 0.1 : 10 of PVA solution under magnetic stirring. Then zinc acetate was added into the solution mixture in a ratio of 0.1 : 10 of PVA solution.

a3) PVA solution in water containing antibacterial/ anti-UV complex and nanoparticles:

Silver nanoparticles were added into the solution from a2) in a ratio of 0.05: 10 of PVA solution under magnetic stirring. Then zinc oxide nanoparticles were added into the solution mixture in a ratio of 0.05: 10 of PVA solution. a4) PVA solution in water containing antibacterial/ anti-UV complex and nanoparticles and water repellent complex: Fluorocarbon complex was added into the solution mixture from a3) in a ratio of 1 : 5 of PVA solution.

The solution mixture from a) was sonicated by a sonicator for 30 minutes.

The solution mixture for nanofibrous filter fabrication in the example 3 composed of chemical as stated below;

Polyvinyl alcohol 7% by solution mixture weight

Silver nitrate 0.7% by solution mixture weight

Silver nanoparticles 0.3% by solution mixture weight

Zinc acetate 0.7% by solution mixture weight

Zinc oxide nanoparticles 0.3% by solution mixture weight

Fluorocarbon complex 14% by solution mixture weight

Water 77% by solution mixture weight

Fiber fabrication process: The solution from b) was fabricated into nanofibrous filter via nanospider machine by applying the electrode-to-ground distance at 18-20 cm, voltage of 55 kV and electrode's rotating speed at 5-8 rpm. After fabrication, the resulted nanofibers were overlapped which resulted in nanoibrous filter. A part of the nanofibrous filter was kept for water repellent testing and the rest for curing in the next process.

The nanofibrous filter from c) was cured at 100-140 °C for 60-120 minutes. Then the nanofibrous filter was characterized in as per water repellency, air permeability, antibacteria, UV functions and tensile strength. In addition, the physical and chemical crosslinking characteristics of the filter were characterized by scanning electron microscope (SEM) as described below;

- Water repellency: The test was performed 2 times after fabrication (Step c) and after curing (Step d) by immersing of the nanofibrous filter in water for 5 minutes then observing the physical character by SEM.

- Air permeability: The test was performed with the cured nanofibrous filter by air permeability tester machine (M021 A).

2. AATCC TM 147:201 1 standard testing by measuring the bacteria growth rate on agar plate and evaluating the size of clear zone around the testing sample. The same tyes of bacteria as the AATCC TM 100:2004 were employed in this standard testing method.

3. Anti-tuberculosis {Mycobacterium tuberculosis H37Ra, TB) property by measuring the living TB cell with confocal microscope on the filter. The green dots represented living TB cells while the red dots represented the dead cells. The experiment was performed in comparison with the commercial cellulose filter with 0.45 micron diameter (Satorius filter). Anti-UV property: The test was performed by measuring the ultraviolet protection factor (UPF) according to the AATCC 183:2010 standard testing method and the UVA and UVB permeability percentage in a frequency range between 315-400 nm and 280-315 nm, respectively, in both dry and wet filter conditions. In addition, the SEM characterization was performed in order to observe the physical characteristics of nanofibers before and after UV irradiation exposure.

- Chemical and physical characterization of crosslinking structure: The test was performed by observing the crosslinking character as well as quantitative and qualitative ratio between O-H and C-H bonding by SEM and FT-IR. Result: After nanofiber fabrication from the composition of PVA solution, silver nitrate, silver nanoparticles, zinc acetate, zinc oxide nanoparticles and fluorocarbon complex according to the example 3, the nanofibers showed the crossover-of-nanofiber crosslinking type. After curing at 100-140 °C, the nanofibers were able to maintain the original shape. On a 1 unit of area, the filter composed of PVA for 43.47%, antibacterial chemical for 6.53%, anti-UV chemical for 6.53% and fluorocarbon complex for 43.47%. After water repellent property testing by immersing the filter in water, there was no transformation in physical characteristics of nanofibers showing high water resistant property (Figure 1, cl-c4). After air permeability testing, the result of 0.43 cm³/sec/cm² showed that air can flow through the filter (Figure 2). For antibacterial testing according to the AATCC standard, the filter from the example 3 showed high antibacterial property as the bacteria could not grow on the testing plate. In addition, the zone of bacteria inhibition expanded to 2.2 mm and 1.2 mm for gram positive and negative bacteria, repectively (Figure 3). For anti-TB testing, the dead TB cells (Red dots) were observed at high number on the filter (Figure 4). After UV irradiation, the nanofibers were merged partially but still showed the original form of nanofiber characteristics (Figure 5, bl and b2). The UPF of the filter was measured in dry and wet conditions. The UPF of the filters in wet and dry conditions were reported at rating of 50+ (Figure 6). The UVA permeability of the filter in dry and wet condtions were 0.1%. Similarly, the UVB permeability of the filter in both conditions were 0.1%. For tensile strength testing before and after UV irradiation, the result showed that the UV irradiated filter had significantly higher tensile strength and elongation percentage than the non-UV irradiated filter. Before UV irradiation, the elongation percentage of the filter was 28.33% and tensile strength of 2.19 N. After UV irradiation, the elongation percentage and tensile strength were increased to 65% and 3.85 N, respectively. From subsequent calculations, the elongation percentage was increased for 56.42% while the tensile strength increased for 43.12%, showing the increase in flexibility and strength (Figure 7 and 8). For crosslinking characterization by SEM, this example showed the crossover-of-nanofiber crosslinking type which inherited the nanofibers' diameter in the range of 171 ± 53 nm and observed the lower amount of porosity than the network crosslinking type but higher than the bimodal-diameter crosslinking type (Figure 9b and 10, bl-b3). This crosslinkning type contained porosity of 48 ± 20% as estimated from the sampling area of 25 μπι² in size with pores' diameter in the range of 170 ± 19 nm. After infrared spectroscopy characterization, the absorbance ratio between O-H and C-H bonding increased slightly after UV irradiation showing the maintaining of crosslinking characteristics (Figure 12 and 13).

Example 4: Fabrication process of tensile strength enhancement by crosslinkers, antbacterial, anti- UV and water repellent nanofibrous filter.

Nanofibrous filter fabrication process according to the example 4 composed of;

a) Solution mixture preparation

al) PVA solution in water: PVA solution was prepared by adding PVA into water in a ratio of 1 : 10 under magnetic stirring at 70-90 °C (The proper temperature was 85 °C) for 120- 180 minutes. Then the prepared PVA solution was kept for the next process. a2) PVA solution in water containing antibacterial and anti-UV complex: Silver nitrate was added into the PVA solution from al) in a ratio of 0.1 : 10 of PVA solution under magnetic stirring. Then zinc acetate was added into the previous solution in a ratio of 0.1 : 10 of

PVA solution.

Silver nanoparticles were added into the solution mixture from a2) in a ratio of 0.05: 10 of PVA solution under magnetic stirring. Then zinc oxide nanoparticles was added into the previous solution in a ratio of 0.05: 10 of PVA solution. a4) PVA solution in water containing antibacterial/ anti-UV complex and nanoparticles and water repellent complex: Fluorocarbon complex was added into the solution from a3) in a ratio of 1 : 5 of PVA solution,

b) The solution mixture from a was sonicated by a sonicator for 30 minutes

c) The crosslinker, glutaraldehyde solution, was mixed with the PVA solution from a) in a ratio of 1 : 5 under magnetic stirring for at least 10 minutes. Then the solution mixture were kept for the fabrication process.

The solution mixture for nanofibrous filter fabrication in the example 1 composed of chemical as stated below;

Polyvinyl alcohol 7% by solution mixture weight

Glutaraldehyde solution 14% by solution mixture weight

Silver nitrate 0.7% by solution mixture weight

Silver nanoparticles 0.3% by solution mixture weight

Zinc acetate 0.7% by solution mixture weight

Zinc oxide nanoparticles 0.3% by solution mixture weight

Fluorocarbon complex 14% by solution mixture weight

Water 63% by solution mixture weight

Fiber fabrication process: The solution from c) was fabricated into nanofibrous filter via nanospider machine by applying the electrode-to-ground distance at 18-20 cm, voltage of 55 kV and electrode's rotating speed at 5-8 rpm. After fabrication, the resulted nanofibers were overlapped which resulted in nanoibrous filter. A part of the nanofibrous filter was kept for water repellent testing and the rest for curing in the next process.

The nanofibrous filter from d) was cured at 100-140 °C for 60-120 minutes. Then the nanofibrous filter was characterized in terms of water repellency, air permeability, antibacteria, UV and tensile strength. In addition, the physical and chemical crosslinking characteristics of the filter were characterized by scanning electron microscope (SEM) as described below;

Water repellency: The test was performed 2 times after fabrication (Step d) and after curing (Step e) by immersing the nanofibrous filter in water for 5 minutes then observing the physical character by SEM.

Air permeability: The test was performed with the cured nanofibrous filter by air permeability tester machine (M021 A).

Antibacteria property: the test was performed according to the standard testing method 1. AATCC TM 100:2004 standard testing by measuring bacteria reduction percentage of gram positive bacteria (Staphylococcus aureus) and gram negative beacteria (Klebsiella pneumonia).

2. AATCC TM 147:2011 standard testing by measuring the bacteria growth rate to on the agar plate and evaluating the size of clear zone around the testing sample. The same tyes of bacteria as the AATCC TM 100:2004 were employed in this standard testing method.

- Anti-UV property: The test was performed by measuring the ultraviolet protection factor (UPF) according to the AATCC 183:2010 standard testing method and the UVA and UVB permeability percentage in a frequency range between 315-400 nm and 280-315 nm respectively in both dry and wet filter conditions. In addition, the SEM characterization was performed in order to obsrve the physical characteristics of nanofibers before and after UV irradiation exposure.

- Tensile strength: The test was performed by measuring the tensile strength of nanofibers before and after UV irradiation according the ASTM G 154:2006 standard (Drying at temperature 60 °C for 480 minutes before condensation at 50 °C for 240 minutes) by Instron Model 5566 machine. Then the nanofibrous filters were cut into 1 inch x 2 inch before testing with the tension speed of 100 mm/minute.

Result: After nanofiber fabrication from the solution mixture between PVA solutions, silver nitrate, silver nanoparticles, zinc acetate, zinc oxide nanoparticles, fluorocarbon complex and glutaraldehyde solution according to the example 4, the nanofiber structure showed the bimodal- diameter crosslinking type and is able to maintain the original shape after curing at 100-140 °C but showed merging character partially. On the 1 unit of area, the filter composed of PVA for 30.30%, antibacterial chemical for 4.55%, anti-UV chemical for 4.55%, fluorocarbon complex for 30.30% and glutaraldehyde for 30.30%. After immersing the filter in water, there was no transformation in physical characteristics of nanofibers showing high water resistant property (Figure 1, dl-d4). After air permeability testing, the result of 0.22 cm³/sec/cm² showed that air can flow through the filter (Figure 2). For antibacterial testing according to the AATCC standard, the filter from the example 4 inhirited high antibacterial property as the bacteria could not grow on the testing plate. In addition, the zone of bacteria inhibition grew upto 3.0 mm and 2.8 mm for gram positive and negative bacteria, repectively (Figure 3). For anti-TB testing, the dead TB cells (Red dots) were observed at high number on the filter (Figure 4). After UV irradiation, the nanofibers were merged partially but still showed the form of original nanofiber characteristics (Figure 5, dl and d2). The UPF of the filter was measured in dry and wet conditions. The UPF of the filter in wet and dry conditions were measured to have rating of 50+ (Figure 6). The UVA permeability of the filter in dry and wet condtions were less than 0.1%. Similarly, the UVB permeability of the filter in both conditions were less than 0.1%. For tensile strength testing before and after UV irradiation, the result showed that the UV irradiated filter had significantly higher tensile strength and elongation percentage than non-UV irradiated filter. Before UV irradiation, the elongation percentage of the filter was 35.56% and tensile strength of 4.08 N. After UV irradiation, the elongation percentage and tensile strength were increased to 73.61% and 6.68 N respectively. From subsequent calculations, the elongation percentage was increased for 51.69% while the tensile strength increased for 38.92% showing the increase in flexibility and strength (Figure 7 and 8). For crosslinking characterization by SEM, this example showed the bimodal-diameter crosslinking type which inherited the nanofibers' diameter in the range of 273 ± 125 nm and observed the lowest amount of porosity in comparison between example 2 and 3

(Figure 9c and 10, cl-c3). This crosslinking type contained porosity of 34 ± 20% as estimated from the sampling area of 25 μπι² in size with pores' diameter in the range of 83 ± 21 nm. After infrared spectroscopy characterization, the absorbance ratio between O-H and C-H bonding increased slightly after UV irradiation showing the maintaining of crosslinking characteristics (Figure 12 and 13).

Conclusion and examples analysis

From the studies of the examples, the best approach for fabricating the high strength and water repellent filter was the addition of crosslinking chemical into the solution mixture prior to fabrication. Examples which inherited the water repellent property were example 2, 3 and 4 which contained glutaraldehyde, fluorocarbon or mixture between glutaraldehyde and fluorocarbon (Figure 1). In addition, air permeability of all examples was more than zero which confirmed the ability of the sample to allow airflow (Figure 2).

For antibacterial property, all types of filters showed excellent antibacterial property against gram positive and negative bacteria under AATCC TM 100:2004 and 147:201 1 standard testings (Figure 3). For anti-TB property against tuberculosis H37Ra, example 3 and 4 inherited excellent anti-TB function with high number of dead TB cells on the filter. The example 2 also had moderate anti-TB property in comparison with the filter from example 1 which had no anti-TB property similar to the control filter (Cellulose filter) (Figure 4).

The anti-UV property of filters was measured by UPF including UVA/UVB transmission percentage in both of dry and wet filter conditions. The result showed that examples 2-4 had anti-UV property as thier physical characteristics remained intact upon exposure (Figure 5 and 6).

The tensile strength testings of filters were divided into two parts—before and after UV irradiation. Examples 2, 3 and 4 showed better tensile strength and elongation after UV irradiation (Figure 7 and 8).

The study of crosslinking characteristics between nanofibers can be performed by SEM characterization. Under SEM, three types of crosslinkings were observed including network crosslinking, bimodal-diameter crosslinking and crossover-of-nanofiber crosslinking (Figure 9). Example 4 which showed bimodal-diameter crosslinking type gave the best results after tensile strength and weathering effect resistant property characterization. On the other hand, example 3 and 2 which had crossover-of-nanofiber and network crosslinking types, respectively, showed inferior physical characteristics (Figure 10). The schematic crosslinking aspects were shown in figure 11.

Apart from physical crosslinking studied by SEM, the qualitative and quantitative analyses of chemical crosslinking were performed by infrared spectroscopy (Figure 12). The result showed that examples 2-4 had high resistance to weathering effect which include simulated thermal, moisture and UV factors. This was confirmed by low IR absorbance ratio between O-H and C-H bonding as an evidence of the remaining high crosslinking degree, a physical origin of mechanical and physical stability (Figure 13).

Claims

1. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight whereas nanofibers in the nanofilter have network crosslinking type, bimodal-diameter crosslinking type and crossover-of-nanofiber crosslinking or mixture of these characteristics. One unit of nanofibrous filter area contains 0.1-50% of functional polymer, 0.01-

20% of antibacterial chemical and 0.01-20% of anti-UV chemical.

2. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to claim 1, whereas the one unit of nanofibrous filter area further comprising 0.01-50% water repellent chemical.

3. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to claims 1 or 2, whereas the one unit of nanofibrous filter area further comprising 0.01-50% crosslinking chemical.

4. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 3, whereas the network crosslinking type has nanofiber's diameter between 265 ± 44 nm.

5. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 4, whereas the amount of porosity of network crosslinking type is higher than the bimodal-diameter crosslinking type and the crossover-of-nanofiber crosslinking type.

6. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 5, whereas the amount of porosity among nanofibers in the network crosslinking type has 74 ± 20% as estimated from 25 μπι² of the filter

7. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 6, whereas the network crosslinking type has pores' diameter in a range of 55 ± 15 nm.

8. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 7, whereas the pores among nanofibers in the network crosslinking type in a rear view is in circular shape.

9. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 8, whereas the functional polymer is the polymer containing active groups along the hydrocarbon chain.

10. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to claim 9, whereas the active group on the hydrocarbon chain of polymer is selected from the group consisting of hydroxyl group, amine group, nitrile group and carboxyl group.

1 1. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 10, whereas the functional polymer is selected from the group consisting of polyacrylonitrile, polyvinyl pyroridone, polyvinyl alcohol, polyhydroxypropyl-metachrylate, polyhydroxyethyl-metachrylate, polyglycerol- metachelate and combinations thereof.

12. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 11, whereas the antibacterial chemical is selected from the group consisting of silver nitrate, silver nanoparticles

13. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 12, whereas the anti-UV chemical is selected from the group consisting of zinc acetate, zinc oxide nanoparticles and combinations thereof.

14. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 2 to 13, whereas the water repellent chemical is fluorocarbon.

15. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 3 to 14, whereas the crosslinking chemical is selected from the group consisting of polyurethane, glutaraldehyde and combinations thereof.

16. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 15, whereas the crossover-of- nanofiber crosslinking type has the nanofiber's diameter in a range of 171 ± 53 nm.

17. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 16, whereas the amount of porosity among nanofibers in the crossover-of-nanofiber crosslinking type is in a range of 48 ± 20% as estimated from 25 μηι² of nanofibrous filter.

18. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 17, whereas the pores' diameter in the crossover-of-nanofiber crosslinking type is in a range of 170 ± 19 nm.

19. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 18, whereas the bimodal-diameter crosslinking type has the nanofiber's diameter is in a range of 273 ± 125 nm.

20. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 19, whereas the amount of porosity among nanofibers in bimodal-diameter crosslinking type is in a range of 34 ± 20% as estimated from 25 μπν² of the filter.

21. Multifunctional nanofibrous filter for water and air microfiltration which is able to be cleaned and is resistant to sunlight according to any one of claims 1 to 20, whereas the pores among nanofibers in bimodal-diameter crosslinking type has the pores' diameter in a range of 83 ± 21 nm.

22. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 1 to 21, whereas the preparation process comprising the step of

a) Solution mixture preparation

al) Polymer solution in water: The polymer solution is prepared by adding functional polymer into water under stirring at 70-90 °C for 120-180 minutes. Then the prepared polymer solution was kept for the next process.

a2) Polymer solution in water containing antibacterial and anti-UV complex: The solution mixture can be prepared by mixing the antibacterial complex with the the polymer solution from al) under stirring. Then anti-UV complex was added into the previous solution.

a3) Polymer solution in water containing antibacterial/anti-UV complexes and nanoparticles:

The solution mixture can be prepared by mixing the antibacterial nanoparticles with solution from a2) under stirring. Then the anti-UV nanoparticles was added into the previous solution mixture. Finally, the polymer solution contained antibacterial/anti-UV complexes and nanoparticles.

b) The solution mixture from a) was sonicated by the sonicator for 30 minutes prior to nanofiber fabrication in the next step.

c) Nanofiber fabrication: The solution from b) is fabricated into nanofibrous filter via solution- based processing by needle-based electrospinning, nanospider electrospinning or forced/centrifuge spinning.

d) The nanofibrous filter from c) was heated at 100-140 °C for 60-120 minutes. Then the nanofibrous filter will result in multifunctional nanofibers having antibacterial, anti-UV, water repellant and high tensile strength properties for water and air filtration and able to clean by water and resistant to sunlight.

23. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to claim 22, whereas the solution from a3) further comprising water repellent complex: The solution can be prepared by adding the water repellent compound in the solution mixture (from step a3).

24. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to claim 22, whereas the solution from b) further comprising crosslinkers by adding the crosslinking chemicals in the solution from b) under stirring for at least 10 minutes prior to nanofiber fabrication in the next step.

25. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 24, whereas the functional polymer has the active group selected from the group consisting of hydroxyl group, amine group, nitrile group and carboxyl group on the main hydrocarbon chain.

26. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 25, whereas the functional polymer is selected from the group consisting of polyacrylonitrile, polyvinyl pyroridone, polyvinyl alcohol, polyhydroxypropyl-metachrylate, polyhydroxyethyl- metachrylate, polyglycerol-metachelate and combinations thereof.

27. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to cleaned and is resistant to sunlight according to any one of claims 22 to 26, whereas the antibacterial is in the form of complex and nanoparticles of silver

28. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 27, whereas the antibacterial is selected from the group consisting of silver nitrate, silver nanoparticles and combinations thereof.

29. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 28, whereas the anti-UV is in the form of complex and nanoparticle of zinc.

30. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 29, whereas the anti-UV is selected from the group consisting of zinc acetate and zinc oxide nanoparticles and combinations thereof.

31. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 30, whereas the water repellent chemicals is fluorocarbon.

32. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 31, whereas the crosslinking chemical is selected from the group consisting of polyurethane, glutaraldehyde and combinations thereof.

33. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 32, whereas the suitable nanofibrous filter fabrication technique is nanospider technique.

34. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 33, whereas the nanospider machine condition can be performed by setting the electrode-to-ground distance at 18-20 cm, voltage of 55 kV and the electrode's rotating speed at 5-8 rpm.

35. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to claim 34, whereas the optimized condition for nanospider machine is setting the electrode-to-ground distance at 18 cm, the voltage of 55 kV and the electrode's rotating speed at 5 rpm.

36. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 32, whereas the optimized condition for electrospinning process is setting the tip-to-ground distance at 10-20 cm, the voltage of 10-20 kV, and the flow speed at 0.12 mm/hour.

37. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 36, whereas the solution mixture for nanofibrous filter fabrication comprising;

Polyvinyl alcohol 7% by weight of the solution mixture

Glutaraldehyde 14% by weight of the solution mixture Silver nitrate 0.7% by weight of the solution mixture

Silver nanoparticles 0.3% by weight of the solution mixture

Zinc acetate 0.7% by weight of the solution mixture

Zinc oxide nanoparticles 0.3% by weight of the solution mixture

Water 77% by weight of the solution mixture

38. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 36, whereas the solution mixture for nanofibrous filter fabrication comprising;

Polyvinyl alcohol 7% by weight of the solution mixture

Silver nitrate 0.7% by weight of the solution mixture Silver nanoparticles 0.3% by weight of the solution mixture Zinc acetate 0.7% by weight of the solution mixture

Zinc oxide nanoparticles 0.3% by weight of the solution mixture

Fluorocarbon 14% by weight of the solution mixture

Water 77% by weight of the solution mixture

39. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 36, whereas the solution mixture for nanofibrous filter fabrication comprising;

Polyvinyl alcohol 7% by weight of the solution mixture Glutaraldehyde 14% by weight of the solution mixture Silver nitrate 0.7% by weight of the solution mixture Silver nanoparticles 0.3% by weight of the solution mixture Zinc acetate 0.7% by weight of the solution mixture

Zinc oxide nanoparticles 0.3% by weight of the solution mixture

Fluorocarbon 14% by weight of the solution mixture

Water 63% by weight of the solution mixture

40. The fabrication process of multifunctional nanofibrous filter for water and air microfiltration able to be cleaned and is resistant to sunlight according to any one of claims 22 to 39, whereas the proper temperature for preparation of polymer solution (Step al) was 85 °C.