Electrospinning in a controlled gaseous environment

• US 20050224999A1
• Filed: 04/08/2004
• Published: 10/13/2005
• Est. Priority Date: 04/08/2004
• Status: Active Grant

• Current Assignee: Research Triangle Institute
• Original Assignee: Research Triangle Institute
• Inventors: Ensor, David S., Andrady, Anthony L.
• Granted Patent: US 7,297,305 B2
• Time in Patent Office: Days
• US Class Current: 264/10
• CPC Class Codes: D01D 5/0061 characterised by the electro-spinning apparatus
• CPC Class Codes: D01F 11/00 Chemical after-treatment of artificial filaments or the like during manufacture
• CPC Class Codes: H05B 6/62 Apparatus for specific applications
• CPC Class Codes: Y10T 428/249924 Noninterengaged fiber-containing paper-free web or sheet which is not of specified porosity
• CPC Class Codes: Y10T 428/2913 Rod, strand, filament or fiber

Abstract

Apparatus and method for producing fibrous materials in which the apparatus includes an extrusion element configured to electrospin a substance from which the fibers are to be composed by an electric field extraction of the substance from a tip of the extrusion element, a collector disposed from the extrusion element and configured to collect the fibers, a chamber enclosing the collector and the extrusion element, and a control mechanism configured to control a gaseous environment in which the fibers are to be electrospun. The method includes providing a substance from which the fibers are to be composed to a tip of an extrusion element, applying an electric field to the extrusion element in a direction of the tip, controlling a gaseous environment about where the fibers are to be electrospun, and electrospinning the substance from the tip of the extrusion element by an electric field extraction of the substance from the tip into the controlled gaseous environment.

Claims

1. An apparatus for producing fibers, comprising:

an extrusion element having a tip, and configured to electrospin a substance from which the fibers are to be composed by an electric field extraction of the substance from the tip of the extrusion element;

a collector disposed from the extrusion element and configured to collect the fibers;

a chamber enclosing the collector and the extrusion element; and

a control mechanism configured to control a gaseous environment in which the fibers are to be electrospun.

2. The apparatus of claim 1, wherein the control mechanism is configured to control a drying rate of electrospun fibers.

3. The apparatus of claim 2, further comprising:

a vapor pool containing at least one of an inorganic and organic liquid; and

said control mechanism comprises a temperature controller configured to control a temperature of the liquid in the vapor pool.

4. The apparatus of claim 3, wherein the liquid comprises at least one of dimethyl formamide, methylene chloride, acetone, and water.

5. The apparatus of claim 4, wherein the temperature controller is configured to control a temperature of the liquid to provide a predetermined vapor pressure of the liquid to the gaseous environment.

6. The apparatus of claim 5, wherein the temperature controller is configured to control the temperature from an ambient temperature to 10°

C. below a boiling point of the liquid.

7. The apparatus of claim 1, wherein the controller is configured to control an injection of species altering an electrical resistance of the gaseous environment in which the fibers are electrospun.

8. The apparatus of claim 7, wherein the control mechanism is configured to control the injection at least one of an electronegative gas, a vapor, ions, and energetic particles.

9. The apparatus of claim 8, wherein the chamber is connected to a supply of the electronegative gas.

10. The apparatus of claim 9, wherein the control mechanism comprises a flow controller configured to control a flow rate of the electronegative gas into the chamber.

11. The apparatus of claim 9, wherein the chamber is connected to a supply of at least CO₂, CO, SF₆, CF₄, N₂O, CCl₄, CCl₃F, and C₂Cl₂F₂.

12. The apparatus of claim 8, wherein the chamber comprises:

a shroud about said extrusion element, connected to a supply of the electronegative gas.

13. The apparatus of claim 12, wherein the control mechanism comprises a flow controller configured to control a flow rate of the electronegative gas into the shroud.

14. The apparatus of claim 12, wherein the shroud is connected to a supply of at least CO₂, CO, SF₆, CF₄, N₂O, CCl₄, CCl₃F, and C₂Cl₂F₂.

15. The apparatus of claim 8, further comprising:

a radioisotope source of the energetic particles,

the control mechanism comprises a shutter configured to control an exposure of the chamber to the radioisotope source, said shutter comprising an energetic particle absorbing material.

16. The apparatus of claim 8, further comprising:

an ion generator configured to generate the ions; and

the control mechanism comprising extraction elements configured to control a rate of extraction of the ions from the ion generator into the gaseous environment.

17. The apparatus of claim 16, wherein the ion generator is configured to inject ions into a Rayleigh instability region in which the fibers are electrospun.

18. The apparatus of claim 1, wherein the chamber is connected to a supply of gas.

19. The apparatus of claim 18, further comprising:

a flow controller configured to control a flow rate of the gas into the chamber.

20. The apparatus of claim 1, wherein the chamber comprises:

a shroud about the extrusion element, connected to a supply of gas.

21. The apparatus of claim 20, wherein the control mechanism comprises a flow controller configured to control a flow rate of the gas into the shroud.

22. The apparatus of claim 1, wherein the extrusion element comprises a plurality of extrusion elements.

23. The apparatus of claim 1, wherein the collector comprises at least one of a plate and a screen.

24. The apparatus of claim 1, wherein the collector comprises an electrical ground.

25. The apparatus of claim 1, wherein the collector is disposed 1-100 cm from said extrusion element.

26. The apparatus of claim 1, further comprising:

a power source electrically connected across said extrusion element and said collector.

27. The apparatus of claim 26, wherein the power source is configured to generate an electric field with a strength of 2,000-400,000 V/m between said extrusion element and said collector.

28. The apparatus of claim 1, wherein the extrusion element has an inner dimension in a range of 50-250 μ

m.

29. The apparatus of claim 1, wherein the extrusion element has an interior cross sectional area of 1,900-50,000 μ

m².

30. An apparatus for producing fibers, comprising:

an extrusion element having a tip, and configured to electrospin a substance from which the fibers are to be composed by an electric field extraction of the substance from the tip of the extrusion element;

a collector disposed from the extrusion element and configured to collect the fibers; and

means for injecting a species to alter an electrical resistance of a gaseous environment in which the fibers are electrospun.

31. The apparatus of claim 30, wherein the means for injecting comprises:

means for injecting at least one of an electronegative gas, a vapor, ions, and energetic particles.

32. The apparatus of claim 31, wherein said means for injecting an electronegative gas comprises:

a chamber about said extrusion element and configured to introduce the electronegative gas into the chamber.

33. The apparatus of claim 31, wherein said means for injecting comprises:

an ion generator configured to generate the ions.

34. The apparatus of claim 33, wherein the ion generator is configured to inject ions into a Rayleigh instability region in which the fibers are electrospun.

35. An apparatus for producing fibers, comprising:

an extrusion element having a tip, and configured to electrospin a substance from which the fibers are to be composed by an electric field extraction of the substance from a tip of the extrusion element;

a collector disposed from the extrusion element and configured to collect the fibers; and

means for controlling a drying rate of electrospun fibers in a gaseous environment in which the fibers are electrospun.

36. The apparatus of claim 35, wherein the means for controlling comprises:

a temperature controller configured to control a temperature of at least one of an inorganic and organic liquid in a vapor pool exposed to the gaseous environment.

37. The apparatus of claim 36, wherein the liquid comprises at least one of dimethyl formamide, methylene chloride, acetone, and water.

38. The apparatus of claim 36, wherein the temperature controller is configured to control the temperature from an ambient temperature to 10°

C. below a boiling point of the liquid in the vapor pool.

39. A method for producing fibers, comprising:

providing a substance from which the fibers are to be composed to a tip of an extrusion element;

applying an electric field to the extrusion element in a direction of the tip;

controlling a gaseous environment about where the fibers are to be electrospun; and

electrospinning the substance from the tip of the extrusion element by an electric field extraction of the substance from the tip into the controlled gaseous environment.

40. The method of claim 39, wherein the controlling comprises:

injecting at least one of an electronegative gas, ions, and energetic particles into the gaseous environment.

41. The method of claim 40, wherein the controlling comprises:

injecting at least one of CO₂, CO, SF₆, CF₄, N₂O, CCl₄, CCl₃F, and C₂Cl₂F₂ into the gaseous environment.

42. The method of claim 40, wherein the injecting comprises:

generating the ions; and

injecting the generated ions into the gaseous environment.

43. The method of claim 42, wherein the injecting the generated ions comprises:

injecting the ions into a Rayleigh instability region downstream from the extrusion element.

44. The method of claim 39, wherein said electrospinning comprises:

electrospinning said substance in the electric field having a strength of 2,000-400,000 V/m.

45. The method of claim 39, wherein said electrospinning comprises:

electrospinning nanofibers.

46. The method of claim 39, wherein the controlling comprises:

introducing a vapor of a solvent into the gaseous environment.

47. The method of claim 46, wherein the introducing a vapor comprises:

introducing the vapor at a predetermined vapor pressure.

48. The method of claim 47, where the exposing comprises:

exposing the chamber to at least one of dimethyl formamide, methylene chloride, acetone, and water.

49. The method of claim 39, wherein the electrospinning comprises:

electrospinning polymeric fibers.

50. The method of claim 49, further comprising:

annealing said polymeric fibers to form carbon fibers.

51. The method of claim 39, wherein the electrospinning comprises:

electrospinning polymeric nanofibers.

52. The method of claim 51, further comprising:

annealing said polymeric nanofibers to form carbon nanofibers.

53. The method of claim 39, wherein the providing a substance comprises:

providing as said substance a solvent in which a polymer is dissolved.

54. The method of claim 53, wherein the providing as said substance comprises:

providing at least one of dimethyl formamide, methylene chloride, acetone, and water.