Apparatus and methods for electrospinning polymeric fibers and membranes

• US 20020175449A1
• Filed: 05/16/2001
• Published: 11/28/2002
• Est. Priority Date: 05/16/2001
• Status: Active Grant

• Current Assignee: Rutgers University
• Original Assignee: Rutgers University
• Inventors: Chu, Benjamin, Fang, Dufei, Hsiao, Benjamin S.
• Granted Patent: US 6,713,011 B2
• Time in Patent Office: Days
• US Class Current: 264/465
• CPC Class Codes: D01D 5/0092 characterised by the electrical field, e.g. combined with a magnetic fields, using biased or alternating fields
• CPC Class Codes: D04H 1/728 by electro-spinning electro-spinning methods and apparatus D01D5/0007

Abstract

An apparatus and methods for electrospinning polymer fibers and membranes are described. The methods include in one aspect electrospinning a polymer fiber from a conducting fluid containing the polymer in the presence of a first electric field established between a conducting fluid introduction device and a ground source and modifying the first electric field with a second electric field to form a jet stream of the conducting fluid. In another aspect the methods include forming an electrospinning jet stream of the conducting fluid and electrically controlling the flow characteristics of the jet stream. In yet another aspect the methods include forming a plurality of electrospinning jet streams of the conducting fluid and independently controlling the flow characteristics of at least one of the jet streams. The apparatus for electrospinning includes a conducting fluid introduction device containing a plurality of electrospinning spinnerets for delivering the conducting fluid, a ground member positioned adjacent to the spinnerets, a support member disposed between the spinnerets and the ground member and movable to receive fibers formed from the conducting fluid, and a means for controlling the flow characteristics of conducting fluid from at least one spinneret independently from the flow characteristics of conducting fluid from another spinneret. An improved conducting fluid introduction device which includes a plurality of spinnerets, each for independently delivering a controlled quantity of conducting fluid at a controlled pressure or flow rate, the spinnerets being charged at an electric potential and being disposed relative to each other to normally interfere with the electric field produced by adjacent spinnerets, each of the spinnerets having a tip at which conducting fluid exits configured to have an electrostatic field strength at each tip stronger than the liquid surface tension at each of the tips is also described.

Claims

1. A method for electrospinning a polymer fiber from a conducting fluid containing said polymer in the presence of a first electric field established between a conducting fluid introduction device and a ground source comprising:

modifying said first electric field with a second electric field to form a jet stream of said conducting fluid.

2. A method according to claim 1, wherein said conducting fluid introduction device is a spinneret.

3. A method according to claim 1, wherein said second electric field is established by imposing at least one field modifying electrode.

4. A method according to claim 3, wherein said field modifying electrode is a plate electrode positioned between said conducting fluid introduction device and said ground source.

5. A method according to claim 3, further comprising controlling the electrical potential on the conducting fluid introduction device by adjusting the electric charge on said field modifying electrode.

6. A method according to claim 3, further comprising imposing a plurality of electrical field modifying electrodes to provide a controlled distribution of electrostatic potential along the direction of flow of said jet stream.

7. A method according to claim 1, further comprising feeding said conducting fluid to said conducting fluid introduction device at a controlled rate.

8. A method according to claim 7, wherein said rate is controlled by maintaining said conducting fluid at a constant pressure or constant flow rate.

9. A method for electrospinning a polymer fiber from a conducting fluid containing a polymer in the presence of an electric field established between a spinneret and a ground source comprising:

a) forming an electrospinning jet stream of said conducting fluid; and

b) electrically controlling the flow characteristics of said jet stream.

10. A method according to claim 9, wherein said flow characteristics of said jet stream are electrically controlled by at least one electrode.

11. A method according to claim 9, wherein said flow characteristics of said jet stream are electrically controlled by at least one pair of electrostatic quadrupole lenses.

12. A method according to claim 11, wherein said flow characteristics of said jet stream are electrically controlled by a plurality of pairs of electrostatic quadropole lenses.

13. A method according to claim 12, wherein said flow characteristics of said jet stream are electrically controlled by using an alternating gradient technique.

14. A method according to claim 9, further comprising electrically controlling said flow characteristics of said jet stream to provide a controlled pattern over a desired target area.

15. A method according to claim 14, wherein said controlled pattern is provided by applying a waveform to the potential on at least one pair of electrostatic quadropole lenses.

17. A method according to claim 16, wherein said flow characteristics of at least one of said jet streams are controlled by at least one scanning electrode.

18. A method according to claim 17, wherein said flow characteristics of at least one or more of said jet streams are controlled by at least one pair of scanning electrodes.

19. A method according to claim 16, wherein said solution introduction device consists of a plurality of electrospinning spinnerets.

20. A method according to claim 19, wherein each spinneret produces an individual jet stream of said conducting fluid.

21. A method according to claim 20, wherein the flow characteristics of each individual jet stream is independently controlled.

22. A method according to claim 21, wherein each spinneret has at least one scanning electrode for electrically independently controlling the flow characteristics of each individual jet stream.

23. A method according to claim 22, wherein each spinneret has two pairs of scanning electrodes for electrically controlling the flow characterists of each individual jet stream.

24. A method according to claim 19, wherein at least two spinnerets deliver different conducting fluids.

25. A method according to claim 24, wherein said different conducting fluids refers to different concentrations of polymer, different polymers, different polymer blends, different additives and/or different solvents.

27. An electrospinning apparatus according to claim 26, wherein said means for independently controlling the flow characteristics comprises at least one electrode disposed adjacent each spinneret, each electrode being charged at a potential different from and separate from said first potential.

28. An electrospinning apparatus according to claim 27, wherein each spinneret has two pairs of scanning electrodes for electrically separately directing the flow characteristics of conducting fluid from said spinneret.

29. An electrospinning apparatus according to claim 27, further comprising a probe associated with at least one spinneret, said probe being disposed between said electrode and said ground member, said probe being electrically charged at a potential different from said spinneret and said electrode.

30. An electrospinning apparatus according to claim 26, wherein said means for independently controlling said flow characteristics comprises a means for individually electrically turning on and off a respective spinneret.

31. An electrospinning apparatus according to claim 30, wherein said means for individually electrically turning on and off a respective spinneret comprises at least one scanning electrode associated with each spinneret.

32. An electrospinning apparatus according to claim 26, wherein said means for independently controlling said flow characteristics comprises a means for applying an alternating gradient to said conducting fluid delivered from said spinnerets.

33. An electrospinning apparatus according to claim 32, wherein said means for applying said alternating gradient comprises a plurality of pairs of electrostatic quadropole lenses.

34. An electrospinning apparatus according to claim 26, wherein said apparatus further comprises a pump for supplying conducting fluid to said solution introduction device at a predetermined pressure.

35. An electrospinning apparatus according to claim 34, wherein said pump is adapted to control the supply rate of conductive fluid at a constant flow rate.

36. An electrospinning apparatus according to claim 34, wherein said pump is adapted to control the supply of conductive fluid at a constant pressure.

37. An electrospinning apparatus according to claim 26, wherein said apparatus comprises a pump system for supplying different conducting fluids to at least two individual spinnerets.

38. An electrospinning apparatus according to claim 26, wherein said solution introduction device comprises a slit-die defining said plurality of spinneret.

39. An electrospinning apparatus according to claim 38, wherein adjacent spinnerets are interconnected by slits.

40. An electrospinning apparatus according to claim 39, wherein said spinnerets are defining by openings in said slit-die and said slits interconnecting said spinnerets are of configurations smaller than said openings.

41. An electrospinning apparatus according to claim 38, further comprising a plurality of scanning electrodes disposed adjacent to each of said spinnerets.

42. An electrospinning apparatus according to claim 26, wherein said solution introduction device comprises a matrix defining said plurality of spinnerets, said spinnerets being disposed in said matrix in electrical isolation from each other.

43. An electrospinning apparatus according to claim 42, wherein at least two individual spinnerets are electrically charged to a different potential.

44. An electrospinning apparatus according to claim 42, further comprising a plurality of individual electrodes wherein at least one individual electrode is disposed adjacent to each individual spinneret.

45. An electrospinning apparatus according to claim 44, wherein at least two of said individual electrodes are electrically charged to a different potential.

47. An improved solution introduction device according to claim 46, wherein each spinneret tip is configured by having a selected geometric profile, a selected spatial relationship relative to other spinneret tips or a combination of both.

48. An improved solution introduction device according to claim 47, further comprising an electrode associated with each spinneret configured to produce an electrical potential to at least partially screen electric field interference from adjacent spinnerets.

49. An improved solution introduction device according to claim 46, further comprising a means for at least partially shielding each spinneret tip from electric field interference from adjacent spinnerets.

50. A improved solution introduction device according to claim 49, wherein said means for at least partially shielding is a physical barrier disposed between adjacent spinnerets.

51. An improved solution introduction device according to claim 50, wherein said physical barrier has a conical shape.

16. A method for forming a controlled-dimension and controlled-morphology membrane by electrospinning a plurality of polymer fibers from a conducting fluid containing said polymer in the presence of an electric field established between a solution introduction device and a ground source, said method comprising:

a) forming a plurality of electrospinning jet streams of said conducting fluid; and

b) independently controlling the flow characteristics of at least one of said jet streams.

26. An electrospinning apparatus for forming a membrane, comprising:

a conducting fluid introduction device for providing a quantity of conducting fluid containing a polymer, said conducting fluid introduction device comprising a plurality of electrospinning spinnerets for delivering said conducting fluid, said spinnerets being electrically charged at a first potential;

a ground member positioned adjacent said spinnerets and electrically charged at a second potential different from said first potential, thereby establishing an electric field between said spinnerets and said ground member;

a support member disposed between said spinnerets and said ground member and movable to receive conducting fluid from said spinnerets; and

means for controlling the flow characteristics of conducting fluid from at least one spinneret independently from the flow of conducting fluid from another spinneret.

46. In an electrospinning apparatus for forming a membrane by electrospinning a plurality of polymer fibers from a conducting fluid which contains a polymer in the presence of an electric field between a conducting fluid introduction device and a ground source, an improved solution introduction device comprising:

a plurality of spinnerets, each for independently delivering a controlled quantity of conducting fluid at a constant pressure or constant flow rate, said spinnerets being charged at an electric potential and being disposed relative to each other to normally interfere with the electric field produced by adjacent spinnerets, each of said spinnerets having a tip at which conducting fluid exits configured to have an electrostatic field strength at each tip stronger than the liquid surface tension at each of said tips.