DISCONTINUOUS CONDUCTIVE FILLER POLYMER-MATRIX COMPOSITES FOR ELECTROMAGNETIC SHIELDING

• US 20080195187A1
• Filed: 02/14/2007
• Published: 08/14/2008
• Est. Priority Date: 02/14/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Li, Bernard, Cai, Chad, Chen, Xingfu
• Granted Patent: US 9,044,593 B2
• Time in Patent Office: Days
• US Class Current: 607/116
• CPC Class Codes: A61N 1/05 for implantation or insertion into the body, e.g. heart electrode A61N1/06 takes precedence
• CPC Class Codes: A61N 1/0563 specially adapted for defibrillation or cardioversion
• CPC Class Codes: A61N 1/086 Magnetic resonance imaging [MRI] compatible leads

Abstract

A medical electrical lead having a conductor assembly covered by an insulating layer, and a shield covering positioned adjacent or proximate to at least a portion of the insulating layer in order to shield the conductor assembly from one or more electromagnetic fields. The shield covering is formed of a polymer-matrix composite. The polymer-matrix composite includes a polymeric resin having discontinuous conductive fillers provided therein. The discontinuous conductive fillers include one or more of nano-sized metal structures and nano-sized non-metallic conductive structures. The nano-sized non-metallic conductive structures can have a coating formed of one or more metals. The nano-sized non-metallic conductive structures can be formed of carbon. In turn, the nano-sized non-metallic conductive structures can include one or more of carbon nanofibers, carbon filaments, carbon nanotubes, and carbon nanoflakes.

Claims

1. A medical electrical lead, comprising:

a conductor assembly having one or more conductors covered by an insulating layer; and

a shield covering adjacent or proximate to at least a portion of the insulating layer to shield the conductors from one or more electromagnetic fields, the shield covering comprising a polymer-matrix composite, the polymer-matrix composite including a polymeric resin having discontinuous conductive fillers provided therein, the discontinuous conductive fillers comprising one or more of nano-sized metal structures and nano-sized non-metallic conductive structures.

2. The medical electrical lead of claim 1, wherein the discontinuous conductive fillers are non-uniformly disbursed throughout the polymeric resin with higher concentration at the outer surface of the shield covering.

3. The medical electrical lead of claim 1, wherein the discontinuous conductive fillers comprise at least the nano-sized non-metallic conductive structures, wherein the nano-sized non-metallic conductive structures are formed of carbon.

4. The medical electrical lead of claim 3, wherein the nano-sized non-metallic conductive structures comprise one or more of carbon nanofibers, carbon filaments, carbon nanotubes, and carbon nanoflakes.

5. The medical electrical lead of claim 4, wherein the nano-sized non-metallic conductive structures comprise carbon nanofibers.

6. The medical electrical lead of claim 5, wherein the carbon nanofibers have an outer diameter ranging in size from about 70 nanometers to about 500 nanometers.

7. The medical electrical lead of claim 1, wherein the discontinuous conductive fillers comprise at least the nano-sized non-metallic conductive structures, wherein the nano-sized non-metallic conductive structures each has an outer metal coating.

8. The medical electrical lead of claim 7, wherein nano-sized non-metallic conductive structures are uniformly disbursed throughout the polymeric resin, the outer metal coating preventing a natural tendency of the structures from clumping together.

9. The medical electrical lead of claim 7, wherein the outer metal coating enhances electromagnetic radiation shielding effectiveness of the nano-sized non-metallic conductive structures, the outer metal coating having a thickness no greater than about 1 μ

m.

10. The medical electrical lead of claim 1, further comprising a coating formed of one or more metals, the coating positioned external to the shield covering, the coating and the shield covering providing an enhanced shielding effect for the one or more conductors.

11. The medical electrical lead of claim 1, further comprising one or more additional layers positioned internal to the shield covering, one of the additional layers comprising a braided metal sheath or mesh, the one additional layer and the shield covering providing an enhanced shielding effect for the one or more conductors.

12. The medical electrical lead of claim 1, further comprising a further layer formed of a conductive non-metallic material being in a wrapped or woven form, the further layer positioned either internal or external to the shield covering, the further layer and the shield covering providing an enhanced shielding effect for the one or more conductors.

13. The medical electrical lead of claim 12, wherein the conductive non-metallic material has a higher skin depth than metals.

14. The medical electrical lead of claim 12, wherein the conductive non-metallic material has an outer diameter that is no greater than about 20 μ

m.

15. The medical electrical lead of claim 12, wherein the conductive non-metallic material comprises carbon.

16. The medical electrical lead of claim 15, wherein the carbon is formed of one or more of carbon fiber, carbon nanofiber, and carbon nanotube having one or more of single and multiple walls.

17. The medical electrical lead of claim 12, wherein the conductive non-metallic material is covered with a thin metal coating.

18. An apparatus for alleviating the adverse effects of various health ailments of a patient comprising:

a medical device; and

an electrical lead connected to the medical device at a proximal end of the lead and having at least a distal end implanted within a patient'"'"'s body, the distal end of the electrical lead having one or more electrodes or electrical contacts for sensing and/or therapy delivery, the electrical lead comprising a conductor assembly having one or more conductors covered by an insulating layer and a shield covering adjacent or proximate to at least a portion of the insulating layer to shield the conductors from one or more electromagnetic fields, the shield covering comprising a polymer-matrix composite, the polymer-matrix composite including a polymeric resin having discontinuous conductive fillers provided therein, the discontinuous conductive fillers comprising one or more of nano-sized metal structures and nano-sized non-metallic conductive structures.

19. The apparatus of claim 18, wherein the discontinuous conductive fillers comprise at least the nano-sized non-metallic conductive structures, wherein the nano-sized non-metallic conductive structures are formed of carbon.

20. The apparatus of claim 19, wherein the nano-sized non-metallic conductive structures comprise one or more of carbon nanofibers, carbon filaments, carbon nanotubes, and carbon nanoflakes.

21. The apparatus of claim 18, wherein the discontinuous conductive fillers comprise at least the nano-sized non-metallic conductive structures, wherein the nano-sized non-metallic conductive structures each has an outer metal coating.

22. The apparatus of claim 21, wherein nano-sized non-metallic conductive structures are uniformly disbursed throughout the polymeric resin, the outer metal coating preventing a natural tendency of the structures to clump together.

23. The apparatus of claim 21, wherein the outer metal coating enhances electromagnetic radiation shielding effectiveness of the nano-sized non-metallic conductive structures, the outer metal coating having a thickness no greater than about 1 μ

m.

24. The apparatus of claim 18, further comprising a coating formed of one or more metals, the coating positioned external to the shield covering, the coating and the shield covering providing an enhanced shielding effect for the one or more conductors.

25. The apparatus of claim 18, further comprising one or more additional layers, one of the additional layers comprising a braided metal sheath or mesh, the additional layers positioned internal to the shield covering, the one additional layer and the shield covering providing an enhanced shielding effect for the one or more conductors.

26. The apparatus of claim 18, further comprising a further layer formed of a conductive non-metallic material being in a wrapped or woven form, the further layer positioned either internal or external to the shield covering, the further layer and the shield covering providing an enhanced shielding effect for the one or more conductors.

27. The apparatus of claim 26, wherein the conductive non-metallic material has a higher skin depth than metals.

28. The apparatus of claim 26, wherein the conductive non-metallic material has an outer diameter that is no greater than about 20 μ

m.

29. The apparatus of claim 26, wherein the conductive non-metallic material comprises carbon.

30. The apparatus of claim 29, wherein the carbon is formed of one or more of carbon fiber, carbon nanofiber, and carbon nanotube having one or more of single and multiple walls.

31. The apparatus of claim 26, wherein the conductive non-metallic material is covered with a thin metal coating.

32. The apparatus of claim 18, wherein the medical device is an implantable medical device, the device and the electrical lead being implanted within the patient.

33. The apparatus of claim 18, wherein the electrical lead further includes a lead extension electrically connecting the lead to the medical device, the shield covering positioned adjacent or proximate to at least a portion of the lead extension.

34. A method of providing a medical electrical lead with uniform shielding effectiveness of electromagnetic radiation using a shield covering having nano-sized discontinuous conductive fillers therein, comprising

selecting one or more nano-sized discontinuous conductive fillers;

selecting a matrix material;

preparing a polymer-matrix composite from the nano-sized discontinuous conductive fillers and the matrix material; and

preparing the medical electrical lead with the polymer-matrix composite.

35. The method of claim 34, wherein the nano-sized discontinuous conductive fillers comprising one or more of nano-sized metal structures and nano-sized non-metallic conductive structures.

36. The method of claim 35, wherein the nano-sized discontinuous conductive fillers comprise at least the nano-sized non-metallic conductive structures, wherein the nano-sized non-metallic conductive structures are formed of carbon.

37. The method of claim 36, wherein the nano-sized non-metallic conductive structures comprise one or more of carbon nanofibers, carbon filaments, carbon nanotubes, and carbon nanoflakes.

38. The method of claim 35, wherein the nano-sized discontinuous conductive fillers comprise at least the nano-sized non-metallic conductive structures, further comprising the step of coating each of the nano-sized non-metallic conductive structures with a metal.