Electrospinning of fine hollow fibers

• US 7,575,707 B2
• Filed: 03/29/2005
• Issued: 08/18/2009
• Est. Priority Date: 03/29/2005
• Status: Expired due to Fees

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Li, Dan, Xia, Younan
• Primary Examiner(s): Tentoni; Leo B
• Application Number:
  US11/097,975
• Publication Number:
  US 20060226580A1
• Time in Patent Office: 1,603 Days
• Field of Search: 264/172.15, 264/209.1, 264/211.16, 264/465, 264/623, 264/634, 264/639
• US Class Current: 264/465
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C04B 2235/3272 Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
• CPC Class Codes: C04B 2235/3289 Noble metal oxides
• CPC Class Codes: C04B 2235/3293 Tin oxides, stannates or oxide forming salts thereof, e.g. indium tin oxide [ITO]
• CPC Class Codes: C04B 2235/408 Noble metals
• CPC Class Codes: C04B 2235/441 Alkoxides, e.g. methoxide, tert-butoxide
• CPC Class Codes: C04B 2235/483 Si-containing organic compounds, e.g. silicone resins, (poly)silanes, (poly)siloxanes or (poly)silazanes
• CPC Class Codes: C04B 2235/5284 Hollow fibers, e.g. nanotubes
• CPC Class Codes: C04B 35/62259 Fibres based on titanium oxide
• CPC Class Codes: C04B 35/624 Sol-gel processing
• CPC Class Codes: C04B 35/6264 Mixing media, e.g. organic solvents
• CPC Class Codes: C04B 35/62675 characterised by the treatment temperature
• CPC Class Codes: C04B 35/62849 Silica or silicates
• CPC Class Codes: C04B 35/62876 with metals
• CPC Class Codes: C04B 35/62892 with a coating layer consisting of particles
• CPC Class Codes: C04B 35/63404 obtained by reactions only involving carbon-to-carbon unsaturated bonds
• CPC Class Codes: C04B 35/63408 Polyalkenes
• CPC Class Codes: C04B 35/63432 Polystyrenes
• CPC Class Codes: C04B 35/63444 Nitrogen-containing polymers, e.g. polyacrylamides, polyacrylonitriles, polyvinylpyrrolidone [PVP], polyethylenimine [PEI]
• CPC Class Codes: D01D 5/0069 characterised by the spinning section, e.g. capillary tube, protrusion or pin
• CPC Class Codes: D01D 5/24 : with a hollow structure; Spinnerette packs therefor D01D5/38 takes precedence; producing tubes of plastic material B29D; addition of agents forming hollow filaments D01F1/08
• CPC Class Codes: D01D 5/34 : Core-skin structure; Spinnerette packs therefor
• CPC Class Codes: D01F 1/10 : Other agents for modifying properties

Abstract

A method for electrospinning nanofibers having a core-sheath, tubular, or composite structure is disclosed. The process uses a spinneret having first and second capillaries that channel first and second fluids in the spinneret, the second capillary surrounding the first. A high voltage is applied between the spinneret and a spaced conductive collector. In one embodiment, the first fluid is a mineral oil and the second fluid is a polymeric solution that may include a polymer, a catalyst, a solvent, and a sol-gel precursor. The as-spun nanofiber includes an oil core and a composite sheath. The oil may be removed to produce a composite tubular fiber or the polymer and oil may be removed by calcination to produce a ceramic tubular fiber. In other embodiments, miscible fluids are used to produce porous nanofibers, selected additives functionalize the surfaces of the nanofibers and/or conjugated polymers are used.

Claims

1. A method for electrospinning a nanofiber comprising:

providing a spinneret having a needle defining a bore, the needle fluidly connected to a first liquid comprising a spinnable polymeric solution, and a capillary having a proximal end connected to a second liquid and a distal end disposed in the needle bore such that an annular aperture is defined between the needle and the capillary;

providing a conducting collector disposed a distance from the needle;

applying a voltage between the needle and the conducting collector; and

feeding the polymeric solution through the needle and feeding the second liquid through the capillary;

wherein the applied voltage is sufficiently high to induce a jet made of the polymeric solution and the second liquid to travel from the spinneret to the collector to form a composite nanofiber.

2. The method of claim 1, wherein the needle is a conductive metal.

3. The method of claim 2, wherein the capillary is a polymer-coated silica capillary.

4. The method of claim 3, wherein the needle and capillary are substantially axisymmetrically disposed.

5. The method of claim 1, wherein the polymeric solution includes a polymer and a sol-gel precursor.

6. The method of claim 5, wherein the sol-gel precursor is a metal alkoxide.

7. The method of claim 5, wherein the polymer is poly(vinyl pyrrolidone).

8. The method of claim 5, wherein the polymeric solution further comprises an acid stabilizer and a solvent.

9. The method of claim 8, wherein the acid stabilizer is acetic acid and the solvent is ethanol.

10. The method of claim 5, wherein the polymeric solution and the second fluid are immiscible.

11. The method of claim 1, wherein the second fluid comprises an oil.

12. The method of claim 11, wherein the second fluid further comprises an additive selected from a molecular species soluble in the oil or nanoparticles that form a stable dispersion in the oil.

13. The method of claim 12, wherein the additive is selected from an oil-based ferrofluid and tin isopropoxide.

14. The method of claim 12, wherein the additive is a long-chain silane.

15. The method of claim 12, wherein the additive is a hydrophobic substance.

16. The method of claim 1, wherein the second fluid comprises a conjugated polymer solution.

17. The method of claim 1, wherein the conjugated polymer solution comprises MEH-PPV and chloroform.

18. The method of claim 1, wherein the conjugated polymer solution comprises a blend of conjugated polymers and a solvent.

19. The method of claim 18, wherein the blend of conjugated polymers comprises MEH-PPV and PHT, and chloroform.

20. The method of Claim 11, further comprising the step of soaking the composite nanofiber in a solvent to remove the second liquid such that a hollow nanofiber remains.

21. The method of claim 20, wherein the solvent is an alkane.

22. The method of claim 11, further comprising the step of calcining the composite nanofiber such that a hollow ceramic fiber remains.

23. The method of claim 22, wherein the calcination temperature is about 500°

C.