Particle filter system incorporating nanofibers

• US 8,652,229 B2
• Filed: 10/08/2009
• Issued: 02/18/2014
• Est. Priority Date: 11/13/2006
• Status: Active Grant

• Current Assignee: Research Triangle Institute
• Original Assignee: Research Triangle Institute
• Inventors: Ensor, David S., Walls, Howard J., Andrady, Anthony L., Walker, Teri A.
• Primary Examiner(s): CLEMENTE, ROBERT ARTHUR
• Application Number:
  US12/575,892
• Publication Number:
  US 20100031617A1
• Time in Patent Office: 1,594 Days
• Field of Search: 554/86, 554/87, 555/01, 555/02, 555/14, 555/27, 555/28, 555/29, 96/54
• US Class Current: 55/527
• CPC Class Codes: B01D 2239/025 comprising nanofibres
• CPC Class Codes: B01D 39/1623 of synthetic origin
• CPC Class Codes: D01D 5/0076 characterised by the collecting device, e.g. drum, wheel, endless belt, plate or grid D01D5/0046 takes precedence
• 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: Y10S 55/05 Methods of making filter
• CPC Class Codes: Y10T 442/622 Microfiber is a composite fiber

Abstract

A filtration device including a filtration medium having a plurality of nanofibers of diameters less than 1 micron formed into a fiber mat in the presence of an abruptly varying electric field. The filtration device includes a support attached to the filtration medium and having openings for fluid flow therethrough. A device for making a filter material. The device includes an electrospinning element configured to electrospin a plurality of fibers from a tip of the electrospinning element, a collector opposed to the electrospinning element configured to collect electrospun fibers on a surface of the collector, and an electric field modulation device configured to abruptly vary an electric field at the collector at least once during electrospinning of the fibers. A method for making a filter material. The method provides a support having openings for fluid flow therethrough, electrospins nanofibers across an entirety of the openings, and abruptly varies an electric field at the collector at least once during electrospinning of the fibers.

Claims

1. A filtration device comprising:

a filtration medium including a plurality of nanofibers having diameters less than 1 micron formed into a fiber mat; and

an electrically conductive rigid support attached to the filtration medium and having macroscopic openings for fluid flow therethrough,

wherein

the nanofibers are deposited in a not completely dry state onto the rigid support, and

the filtration medium has a figure of merit FoM=−

Log(Pt)/Δ

P, where Pt is the fractional penetration of an aerosol particle diameter of 0.3 microns and Δ

P is a filtration medium pressure drop across the filtration medium corresponding to a face velocity of 5.3 cm/s, and said figure of merit is equal to or greater than 14 kPa<sup>−

1</sup> and less than 98 kPa<sup>−

1</sup>.

2. The device of claim 1, wherein the rigid support has at least one of a conical shape, a curved shape, a circular shape, a planar shape, a spherical shape, and a cylindrical shape, and combinations thereof.

3. The device of claim 1, wherein the nanofibers are integrally attached one to another at points along respective ones of the nanofibers.

4. The device of claim 1, wherein the nanofibers have an average fiber diameter of less than 500 nm.

5. The device of claim 1, wherein the nanofibers have an average fiber diameter of less than 200 nm.

6. The device of claim 1, wherein the nanofibers have an average fiber diameter of less than 100 nm.

7. The device of claim 1, wherein the filtration medium comprises plural layers of oriented fibers.

8. The device of claim 1, wherein the nanofibers are deposited and bonded on the macroscopic openings of the support to form a mesh-fiber filter structure.

9. The device of claim 1, further comprising a supplemental filtration medium.

10. The device of claim 9, wherein the supplemental filtration layer provides filtration for particles larger than a micron in diameter.

11. The device of claim 1, further comprising:

plural supports, with respective ones of the supports including respective nanofiber layers to provide multi-stage filtration.

12. A filtration device comprising:

a filtration medium including a plurality of nanofibers having diameters less than 1 micron formed into a fiber mat; and

a support attached to the filtration medium and having macroscopic openings for fluid flow therethrough,

wherein,

the filtration medium has a figure of merit FoM=−

Log(Pt)/Δ

P, where Pt is the fractional penetration of an aerosol particle diameter of 0.3 microns and Δ

P is a filtration medium pressure drop across the filtration medium corresponding to a face velocity of 5.3 cm/s, and said figure of merit is equal to or greater than 14 kPa<sup>−

1</sup> and less than 98 kPa<sup>−

1</sup>.

13. A filtration device comprising:

a filtration medium including a polymer-based material having microscopic openings; and

a support attached to the filtration medium and having macroscopic openings for fluid flow therethrough,

wherein

the filtration medium has a figure of merit FoM=−

Log(Pt)/Δ

P, where Pt is the fractional penetration of an aerosol particle diameter of 0.3 microns and Δ

P is a filtration medium pressure drop across the filtration medium corresponding to a face velocity of 5.3 cm/s, and said figure of merit is equal to or greater than 14 kPa<sup>−

1</sup> and less than 98 kPa<sup>−

1</sup>.

14. The device of claim 13, wherein the figure of merit is equal to or greater than 20 kPa⁻

1.

15. The device of claim 13, wherein the figure of merit is equal to or greater than 50 kPa⁻

1.

16. The device of claim 13, wherein the polymer-based material comprises nanofibers in one layer integrally attached to other nanofibers in an adjacent layer of the filtration medium.

17. The device of claim 13, wherein the polymer-based material comprises a plurality of nanofibers having diameters less than 1 micron.

18. The device of claim 13, wherein the polymer-based material comprises network spaces to allow particles to move in between.