Dry electrode system for detection of biopotentials and dry electrode for making electrical and mechanical connection to a living body

• US 4,865,039 A
• Filed: 05/20/1988
• Issued: 09/12/1989
• Est. Priority Date: 08/21/1985
• Status: Expired due to Fees

• Current Assignee: Technology 21 Incorporated
• Original Assignee: Spring Creek Institute
• Inventors: Dunseath, W. J. Ross Jr.
• Primary Examiner(s): Cohen, Lee S.
• Application Number:
  US07/196,661
• Time in Patent Office: 480 Days
• Field of Search: 128/639-641, 128/643, 128/644, 128/696, 128/798, 128/802, 128/803, 128/902
• US Class Current: 600/410
• CPC Class Codes: A61B 2562/182 Electrical shielding, e.g. using a Faraday cage
• CPC Class Codes: A61B 5/25 Bioelectric electrodes therefor
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: Y10S 128/902 Biological signal amplifier

Abstract

A dry electrode system for the detection of biopotentials existing on the surface of the skin of a living body, including a dry electrode pad with a resilient conductive pad adhering to at least one adhesive pad or otherwise having opposed adhesive surfaces, one of which is adapted to engage the skin of the living body. The dry electrode pad makes electrical connection to an amplifying circuit which transmits a biopotential derived from the conductive pad to a monitor. The amplifying circuit includes a conductive input contact for making electrical contact to the conductive pad, a lead amplifier having an input coupled to the input contact, and a voltage driven shield coupled to the output of the lead amplifier and surrounding portions of the input contact not in engagement with the dry electrode pad. In a preferred embodiment, conductive adhesive layers are applied to opposed sides of a conductive foam pad to construct the dry electrode pad.

Claims

1. A dry electrode system for the detection of biopotentials existing on the surface of the skin of a living body, comprising:

a conductive dry electrode having opposed sides, one of which is adapted to contact said skin, comprising a conductive substrate having opposed sides, and adhesive means comprising first and second conductive adhesive layers applied to opposed sides of said conductive substrate, said first adhesive layer adapted to adhere said dry electrode to said skin; and

an amplifying circuit connected to the other side of said dry electrode by means of said second adhesive layer for amplifying a biopotential transmitted via said dry electrode to said amplifying circuit.

2. A dry electrode system according to claim 1, wherein said dry electrode has an electrical impedance to dry skin of not greater than 1.5 million ohms at 10 Hz and an AC noise baseline not greater than 150 μ

V peak (0.15 to 100 Hz) under conditions of dry to saturation within a 0.9% saline solution.

3. A dry electrode system according to claim 1 or 2, wherein said amplifying circuit comprises:

an insulating housing having a conductive input contact mounted thereon and engaging the dry electrode,

a lead amplifier having a high impedance input coupled to said input contact and an output, and

a lead wire cable having plural conductors connected to said lead amplifier and supplying power and circuit common potential to said lead amplifier and taking out said output from said lead amplifier.

4. The dry electrode system as defined in claim 3, wherein said conductive input contact comprises a material that maintains an AC noise voltage baseline of not more than 150 μ

V (0.15 to 100 Hz) under conditions ranging from dry to saturation with a 0.9% saline solution.

5. A dry electrode system according to claim 3, comprising:

means for providing a circuit common potential connection to the living body, including,

a second dry electrode also comprising a conductive substrate having opposed sides one of which is adapted to engage the skin of the living body, and adhesive means having first and second adhesive surfaces, said first adhesive surface adapted to adhere said second dry electrode to the skin of said living body,

a second electrical contact mounted on a second housing and adhering to said second surface of said adhesive means, said second contact electrically contacting said second dry electrode, and

passive lead wire means for electrically conductively coupling said second electrical contact to said conductor carrying said circuit common potential.

6. A dry electrode system according to claim 1 or 2, wherein said adhesive means comprises:

a pair of tissue substrates each having opposed sides covered with a conductive adhesive layer, said pair of substrates sandwiching said conductive substrate therebetween.

7. A dry electrode system according to claim 6, wherein:

said first adhesive layer comprises a hypoallergenic adhesive material, and

said second adhesive layer comprises an adhesive material which leaves no adhesive residue on said amplifying circuit after removal therefrom.

8. A dry electrode system according to claim 1 or 2, wherein:

said first adhesive layer comprises a hypoallergenic adhesive material, and

said second adhesive layer comprises an adhesive material which leaves no adhesive residue on said amplifying circuit after removal therefrom.

9. A dry electrode system for the detection of biopotentials existing on the surface of the skin of a living body, comprising:

a conductive dry electrode comprising a conductive substrate and having opposed sides, one of which is adapted to contact the skin of said living body, and adhesive means, having first and second adhesive surfaces, at least said first adhesive surface being conductive and adapted to adhere said conductive substrate to said skin; and

an amplifying circuit connected to the other side of said dry electrode for amplifying a biopotential transmitted via said dry electrode pad to said amplifying circuit;

wherein said adhesive means comprises;

a conductive adhesive layer applied to at least a portion of said conductive substrate; and

an insulative adhesive layer applied to a selected portion of at least one of the conductive substrate and the conductive adhesive layer.

10. A dry electrode system according to claim 9, wherein said amplifying circuit comprises:

an insulating housing having a conductive input contact mounted thereon engaging the dry electrode,

a lead amplifier having a high impedance input coupled to said input contact and an output, and

a lead wire cable having plural conductors connected to said lead amplifier and supplying power and circuit common potential to said lead amplifier and taking out said output from said lead amplifier.

11. The dry electrode system as defined in claim 10, wherein said conductive input contact comprises a material that maintains an AC noise voltage baseline of not more than 150 μ

V peak (0.15 to 100 Hz) under conditions ranging from dry to saturation with a 0.9% saline solution.

12. A dry electrode system according to claim 11, comprising:

means for providing a circuit common potential connection to the living body, including,

a second dry electrode also comprising a conductive substrate having opposed sides one of which is adapted to engage the skin of the living body, and adhesive means having first and second adhesive surfaces, said first adhesive surface adapted to adhere said second dry electrode to the skin of said living body,

a second electrical contact mounted on a second housing and adhering to said second surface of said adhesive means, said second contact electrically contacting said second dry electrode to the skin of said living body,

a second electrical contact mounted on a second housing and adhering to said second surface of said adhesive means, said second contact electrically contacting said second dry electrode, and

passive lead wire means for electrically conductively coupling said second electrical contact to said conductor carrying said circuit common potential.

13. A dry electrode for enabling electrical and mechanical connection between the skin of a living body and an electrically conductive contact, comprising:

a conductive substrate having first and second opposed sides, one of which is adapted to contact the skin of said living body; and

adhesive means having opposed first and second adhesive surfaces respectively provided on the opposed sides of said conductive substrate, said first adhesive surface being conductive and adapted to adhere to the skin such that one opposed side of said conductive substrate is in electrical connection with the skin, said second adhesive surface adapted to adhesively engage said contact with the other opposed side of said conductive substrate in electrical connection with said contact.

14. A dry electrode according to claim 13, wherein said dry electrode has an electrical impedance to dry skin of not greater than 1.5 million ohms at 10 Hz and an AC noise baseline not greater than 150 μ

V peak (0.15 to 100 Hz) under conditions of dry to saturation within a 0.9% saline solution.

15. A dry electrode according to claims 13 or 14, wherein said adhesive means comprises:

first and second conductive adhesive layers applied to respective opposed sides of said conductive substrate.

16. A dry electrode according to claims 13 or 14, wherein said adhesive means comprises:

a pair of tissue substrates each having opposed sides covered with a conductive adhesive layer, said pair of substrates sandwiching said conductive substrate therebetween.

17. A dry electrode according to claims 13 or 14, wherein said adhesive means comprises:

a conductive adhesive layer applied to said one side of said conductive substrate and an insulative adhesive layer applied to selected portions of the other side of said conductive substrate, said conductive adhesive layer adapted to adhesively engage the skin, and said insulative adhesive layer adapted to adhesively engage the contact with said conductive substrate in electrical connection with said contact.

18. A dry electrode according to claims 13 or 14, wherein:

said first adhesive surface comprises a hypoallergenic adhesive material, and

said second adhesive surface comprises an adhesive material which leaves no residue on said contact after removal therefrom.

19. A dry electrode according to claims 13 or 14, wherein said adhesive means comprises:

a conductive adhesive layer applied to at least a portion of said conductive substrate; and

an insulative adhesive layer applied to a selected portion of at least one of the conductive substrate and the conductive adhesive layer.

20. A dry electrode pad for enabling electrical and mechanical connection between the skin of a living body and an electrically conductive contact, comprising:

a resilient conductive pad having first and second opposed sides, one of which is adapted to contact the skin of said living body; and

adhesive means having opposed first and second adhesive surfaces respectively provided on the opposed sides of said conductive pad, said first adhesive surface being conductive and adapted to adhere to the skin such that one opposed side of said conductive pad is in electrical connection with the skin, said second adhesive surface adapted to adhesively engage said contact with the other opposed side of said conductive pad in electrical connection with said contact.

21. A dry electrode pad according to claim 20, wherein said conductive pad comprises a resilient material having not less than 5% rebound value, and wherein said dry electrode pad has an electrical impedance to dry skin of not greater than 1.5 million ohms at 10 Hz and an AC noise base line not greater than 150 μ

V peak (0.15 to 100 Hz) under conditions of dry to saturation within a 0.9% saline solution.

22. A dry electrode pad according to claim 21, wherein said conductive pad comprises:

an open-cell foam.

23. The dry electrode pad as defined in claim 22, wherein said conductive foam pad comprises:

carbon loaded polyurethane foam.

24. A dry electrode pad according to claim 21, wherein said conductive pad comprises:

a closed-cell foam.

25. A dry electrode pad according to claim 24, wherein said conductive foam pad comprises:

a cross-linked vinyl-nitrile polymer.

26. A dry electrode pad according to claim 20, 21, 22 or 23, wherein said adhesive means comprises:

first and second conductive adhesive layers applied to respective opposed sides of said resilient conductive pad.

27. A dry electrode pad according to claim 20, 21, 22 or 23, wherein said adhesive means comprises:

a pair of tissue substrates each having opposed sides covered with a conductive adhesive layer, said pair of substrates sandwiching said resilient conductive pad therebetween.

28. A dry electrode pad according to claim 20, 21, 22 or 23, wherein said adhesive means comprises:

a conductive adhesive layer applied to said one side of said resilient conductive pad and an insulative adhesive applied to selected portions of the other side of said resilient conductive pad, said conductive adhesive adapted to adhesively engage the skin, and said insulative adhesive adapted to adhesively engage the contact with said resilient conductive pad in electrical connection with said contact.

29. A dry electrode pad according to claim 20, 21, 22 or 23, wherein:

said first adhesive surface comprises a hypoallergenic adhesive material, and

said second adhesive surface comprises an adhesive material which leaves no adhesive residue on said contact after removal therefrom.

30. A dry electrode pad according to claim 20, 21, 22 or 23, wherein said conductive pad comprises:

a flexible conductive film provided on at least one side of said conductive pad, said conductive film having an electrical impedance to dry skin of not greater than 1.5 million ohms at 10 Hz and maintaining an AC noise voltage (0.15 to 100 Hz) of not more than 150 μ

V peak under conditions ranging from dry to saturation with a 0.9% saline solution.

31. A dry electrode pad according to claim 30, wherein said conductive film is provided on both opposed sides of said conductive pad.

32. A dry electrode pad according to claim 31, wherein said conductive film comprising:

a cured mixture of one and one half parts by volume graphite powder, five parts by volume distilled water and ten parts by volume of liquid latex.

33. A dry electrode pad according to claim 20, 21, 22 or 23, wherein said adhesive means comprises:

a conductive adhesive layer applied to at least a portion of said resilient conductive pad; and

an insulative adhesive layer applied to a selected portion of at least one of the resilient conductive pad and the conductive adhesive layer.