Nanofiber filter facemasks and cabin filters

1. A filtration medium, comprising:

a fine filter layer comprising a plurality of nanofibers; and

a coarse filter layer comprising a plurality of microfibers, the coarse filter layer attached to said fine filter layer,

wherein said coarse filter layer is positioned proximal to a direction of fluid flow, and said fine filter layer is positioned distal to said direction of fluid flow.

2. The filtration medium of claim 1 , wherein said nanofibers comprise electrospun polymer fibers.

3. The filtration medium of claim 1 , wherein said nanofibers comprise melt-blown polymer fibers.

4. The filtration medium of claim 1 , wherein said nanofibers have an average diameter of about 5 to about 500 nanometers.

5. The filtration medium of claim 1 , wherein said nanofibers have a surface area-to-volume ratio of about 1.3×10 7 /meter to about 4×10 8 /meter.

6. The filtration medium of claim 1 , wherein said nanofibers comprise an electrical charge.

7. The filtration medium of claim 1 , wherein said fine filter layer further comprises a plurality of substrate nanoparticles.

8. The filtration medium of claim 7 , wherein the content of said substrate nanoparticles in said fine filter layer is from about 0.1 wt % to about 10 wt %.

9. The filtration medium of claim 7 , wherein said substrate nanoparticles comprise anti-microbial substrates.

10. The filtration medium of claim 9 , wherein said anti-microbial substrates are porous.

11. The filtration medium of claim 9 , wherein said anti-microbial substrates comprise magnesium oxide, silver nanoparticles, silver nitrate, titanium oxide nanoparticles, Poly(N-benzyl-4-vinylpyridinium chloride), or combinations thereof.

12. The filtration medium of claim 7 , wherein said substrate nanoparticles comprise adsorption particles.

13. The filtration medium of claim 12 , wherein said adsorption particles comprise activated carbon, silica gel, activated alumina, zeolites, porous clay minerals, molecular sieves, zinc oxide, calcium oxide, cupric oxide, magnesium oxide, manganese dioxide, manganese oxide, aluminum oxide, zeolite, or combinations thereof.

14. The filtration medium of claim 12 , wherein said adsorption particles comprise carbon nanoparticles.

15. The filtration medium of claim 7 , wherein said substrate nanoparticles comprise desorption substances.

16. The filtration medium of claim 15 , wherein said desorption substances comprise steroids, albuterol powder, respirable antisense oligonucleotides tiotropium bromide, beclomethasone dipropionate, albuterol sulfate and ipratropium bromide, formoterol fumarate inhalation powder, albuterol sulfate inhalation aerosol, triamcinolone acetonide spray, or combinations thereof.

17. The filtration medium of claim 1 , wherein said fine filter layer has a thickness of about 10 to about 1000 microns.

18. The filtration medium of claim 1 , wherein said fine filter layer has a packing density of nanofibers of about 0.1 to about 2 grams per square meter of filter area.

19. The filtration medium of claim 1 , wherein said microfibers comprise polyethylene, glass, cellulose acetate, activated carbon, or combinations thereof.

20. The filtration medium of claim 1 , wherein said microfibers have an average diameter of about 1 to about 30 microns.

21. The filtration medium of claim 1 , wherein said coarse filter layer has a thickness of about 0.1 to about 20 millimeters.

22. The filtration medium of claim 1 , wherein said fine filter layer and said coarse filter layer form a bi-layer unit that is a well-bonded laminate structure.

23. The filtration medium of claim 1 , wherein said fine filter layer and said coarse filter layer form a bi-layer unit, the filtration medium further comprising a plurality of said bi-layer units.

24. The filtration medium of claim 1 , further comprising a cover layer on said fine filter layer.

25. The filtration medium of claim 24 , further comprising a protective layer on said cover layer.

26. The filtration medium of claim 1 , further comprising a cover layer on said coarse filter layer.

27. The filtration medium of claim 26 , further comprising a hydrophobic layer on said cover layer.

28. The filtration medium of claim 27 , further comprising a protective layer on said hydrophobic layer.

29. A filtration article, comprising a body and the filtration medium of claim 1 attached to said body.

30. The filtration article of claim 29 , wherein the filtration article is selected from a filter facemask, a ward filter, a ventilation filter, a vehicle filter, a vacuum filter, and a respirator filter.

31. A method of making a filtration medium, comprising:

providing a fine filter layer comprising a plurality of nanofibers;

providing a coarse filter layer comprising a plurality of microfibers; and

attaching said fine filter layer to said coarse filter layer,

wherein said coarse filter layer is positioned proximal to a direction of fluid flow and said fine filter layer is positioned distal to said direction of fluid flow.

32. The method of claim 31 , further comprising providing a plurality of substrate nanoparticles into said fine filter layer.

33. The method of claim 31 , further comprising providing alternating layers of fine filter layers and coarse filter layers.

34. The method of claim 31 , further comprising providing a cover layer on said fine filter layer.

35. The method of claim 34 , further comprising providing a protective layer on said cover layer.

36. The method of claim 31 , further comprising providing a cover layer on said coarse filter layer.

37. The method of claim 36 , further comprising providing a hydrophobic layer on said cover layer.

38. The method of claim 37 , further comprising providing a protective layer on said hydrophobic layer.