Nanofiber mats and production methods thereof

• US 7,592,277 B2
• Filed: 05/17/2005
• Issued: 09/22/2009
• Est. Priority Date: 05/17/2005
• Status: Active Grant

• Current Assignee: Research Triangle Institute
• Original Assignee: Research Triangle Institute
• Inventors: Prabhu, Purva, Ensor, David S., Walker, Teri A., Andrady, Anthony L.
• Primary Examiner(s): TORRES VELAZQUEZ, NORCA LIZ
• Application Number:
  US11/130,269
• Publication Number:
  US 20060264140A1
• Time in Patent Office: 1,589 Days
• Field of Search: 442/340, 442/327, 442/341, 442/350, 442/351, 442/401, 442/414, 442381-382, 442/393, 442/415, 442/417, 442/409, 442/411, 428/357, 428/364, 428/365, 428/401, 425/174.8 E, 264/10, 264/465
• US Class Current: 442/340
• CPC Class Codes: D01D 5/0061 characterised by the electro-spinning apparatus
• CPC Class Codes: D04H 1/4291 Olefin series
• CPC Class Codes: Y10T 428/29 Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber
• CPC Class Codes: Y10T 428/2915 including textile, cloth or fabric
• CPC Class Codes: Y10T 428/298 Physical dimension
• CPC Class Codes: Y10T 442/60 Nonwoven fabric [i.e., nonwoven strand or fiber material]
• CPC Class Codes: Y10T 442/614 Strand or fiber material specified as having microdimensions [i.e., microfiber]
• CPC Class Codes: Y10T 442/615 Strand or fiber material is blended with another chemically different microfiber in the same layer
• CPC Class Codes: Y10T 442/625 Autogenously bonded
• CPC Class Codes: Y10T 442/626 Microfiber is synthetic polymer
• CPC Class Codes: Y10T 442/659 Including an additional nonwoven fabric
• CPC Class Codes: Y10T 442/66 Additional nonwoven fabric is a spun-bonded fabric
• CPC Class Codes: Y10T 442/681 Spun-bonded nonwoven fabric
• CPC Class Codes: Y10T 442/69 Autogenously bonded nonwoven fabric
• CPC Class Codes: Y10T 442/692 Containing at least two chemically different strand or fiber materials
• CPC Class Codes: Y10T 442/696 Including strand or fiber material which is stated to have specific attributes [e.g., heat or fire resistance, chemical or solvent resistance, high absorption for aqueous compositions, water solubility, heat shrinkability, etc.]
• CPC Class Codes: Y10T 442/697 Containing at least two chemically different strand or fiber materials
• CPC Class Codes: Y10T 442/699 Including particulate material other than strand or fiber material

Abstract

An apparatus and method in which the apparatus includes a first electrospinning device configured to electrospin first fibers of a first substance, a second electrospinning device configured to electrospin second fibers of a second substance such that first and second fibers combine in a mat formation region, and a biasing device configured to bias the first electrospinning device with a first electric polarity and to bias the second electrospinning device with a second electric polarity of opposite polarity to the first electric polarity to promote attraction and coalescence between the first and second fibers. The method electrospins under the first electric polarity first fibers from the first substance, electrospins under the second electric polarity fibers from the second substance, and coalesces the first and second fibers to form the fiber mat.

Claims

1. A mat of fibers, comprising:

a plurality of intermixed first and second electrospun fibers comprising oppositely charged nanofibers; and

a first region including said plurality of intermixed fibers, the first and second electrospun fibers having an average of diameters (d) less than 500 nm; and

an average separation distance between the first and second fibers is equal to or proximate to d.

2. The mat of claim 1, wherein said first region has a cross section fiber density of at least (2.5×

10¹³)/d².

3. The mat of claim 1, wherein the first fibers comprise a material different than that of the second fibers.

4. The mat of claim 1, wherein the first fibers have a first elastic modulus and the second fibers have a second elastic modulus at least twice the first elastic modulus.

5. The mat of claim 4, wherein the first fibers comprise a material different than that of the second fibers.

6. The mat of claim 4, wherein the second elastic modulus is at least five times the first elastic modulus.

7. The mat of claim 6, wherein the first fibers comprise a material different than that of the second fibers.

8. The mat of claim 3, wherein the first fibers comprise hydrophobic fibers and the second fibers comprise hydrophilic fibers.

9. The mat of claim 8, wherein the hydrophobic fibers comprise at least one of poly(alkyl acrylate), polybutadiene, polyethylene, polylactones, polystyrene, polyacrylonitrile, polyethylene (terephthalate), polysulfone, polycarbonate, and poly(vinyl chloride).

10. The mat of claim 8, wherein the hydrophilic fibers comprise at least one of poly(acrylic acid), poly(ethylene glycol), poly(vinyl alcohol), poly (vinyl acetate), cellulose, poly(acrylamide), proteins, poly (vinyl pyrrolidone), and poly(styrene sulfonate).

11. The mat of claim 1, wherein the first fibers have a first average diameter along a length thereof and the second fibers have a second average diameter along a length thereof different from the first average diameter.

12. The mat of claim 11, wherein the first average diameter is less than 10 μ

m and the second average diameter is less than 500 nm.

13. The mat of claim 11, wherein the first average diameter is less than 1 μ

m and the second average diameter is less than 100 nm.

14. The mat of claim 1, wherein the first region comprises:

a region in which the first fibers vary in number relative to a number of the second fibers along a predetermined direction of the mat.

15. The mat of claim 14, wherein a relative number of the first fibers to the second fibers varies along the predetermined direction.

16. The mat of claim 15, wherein the first fibers comprise a material different than that of the second fibers.

17. The mat of claim 16, wherein a relative number of the first fibers to the second fibers varies linearly along the predetermined direction.

18. The mat of claim 15, wherein the first fibers have an average diameter along a length thereof different than that of the second fibers.

19. The mat of claim 18, wherein a relative number of the first fibers to the second fibers varies linearly along the predetermined direction.

20. The mat of claim 1, further comprising:

a second region disposed on a first side of the first region and having more first fibers than second fibers; and

a third region disposed on a second side of the first region opposite the first side and having more second fibers than first fibers.

21. The mat of claim 20, wherein

the first fibers of said second region comprise hydrophobic fibers;

and

the second fibers of said third region comprise hydrophilic fibers.

22. The mat of claim 20, wherein

the first fibers of said second region have an average diameter less than 10 μ

m along lengths thereof; and

the second fibers of said third region have an average diameter less than 500 nm along lengths thereof.

23. The mat of claim 20, wherein

the first fibers of said second region have an average diameter less than 1 μ

m along corresponding lengths thereof; and

the second fibers of said third region have an average diameter less than 100 nm along corresponding lengths thereof.

24. The mat of claim 1, wherein the first and second fibers comprise a same material.

25. The mat of claim 1, wherein the first and second fibers have the same average diameter.

26. The mat of claim 1, further comprising:

particles included with the mat.

27. The mat of claim 26, wherein the particles include at least one of a metallic material, an organic material, an oxide material, a semiconductor material, an electroluminescent material, a phosphorescent material, a medical compound, and a biological material.

28. A composite filter comprising:

a plurality of intermixed first and second electrospun fibers comprising oppositely charged nanofibers that form a composite of intermixed fibers;

the composite of intermixed fibers having an average of diameters (d) of less than 500 nm, and

an average separation distance between the first and second fibers equal to or proximate to d.

29. A skin substitute comprising:

a membrane comprising plural electrospun hydrophilic fibers and plural electrospun hydrophobic fibers comprising oppositely charged nanofibers that form a composite of intermixed fibers;

the composite of intermixed fibers having an average of diameters (d) of less than 500 nm, and

an average separation distance between the intermixed fibers equal to or proximate to d.

30. A filtration medium comprising:

a plurality of intermixed first and second electrospun nanofibers comprising oppositely charged nanofibers that form a composite of intermixed nanofibers;

the composite of intermixed nanofibers having an average of diameters (d) of less than 1 μ

m, and

an average separation distance between the first and second nanofibers equal to or proximate to d.

31. The mat of claim 30, wherein the first nanofibers comprise a material different than that of the second nanofibers.

32. The mat of claim 30, wherein the first nanofibers have a first elastic modulus and the second nanofibers have a second elastic modulus at least twice the first elastic modulus.

33. A composite fiber mat comprising:

plural intermeshed electrospun fibers of a given polarity; and

electrosprayed particles having a polarity opposite to the electrospun fibers and attached to at least one of the plural intermeshed fibers by a fiber material of the at least one of the plural intermeshed fibers;

wherein the electrosprayed particles are autogenously attached to the plural intermeshed fibers.

34. The mat of claim 33, wherein the particles are partially embedded in a surface of the plural intermeshed fibers.

35. The mat of claim 33, wherein the particles comprise at least one of a metallic material, an organic material, an oxide material, a semiconductor material, an electroluminescent material, a phosphorescent material, a medical compound, and a biological material.

36. The mat of claim 33, wherein the plural intermeshed fibers comprise a cross section fiber density of at least (2.5×

10¹³)/d² fibers/cm², where a value of d is given in nm, is less than 500 nm, and comprises an average of diameters of the first and second fibers in a cross section of the composite fiber mat.