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EP-3934525-B1 - MANUFACTURING OF SKIN-COMPATIBLE ELECTRODES

EP3934525B1EP 3934525 B1EP3934525 B1EP 3934525B1EP-3934525-B1

Inventors

  • ZALAR, PETER
  • Smits, Edsger Constant Pieter
  • VAN DER MEULEN, INGE
  • GILLISSEN, STIJN
  • NEGELE, Carla
  • Goethel, Frank
  • ROSCHEK, TOBIAS
  • BESLER, Alissa

Dates

Publication Date
20260506
Application Date
20200306

Claims (20)

  1. A method of manufacturing a skin-compatible electrode (100), the method comprising: - printing a conductive ink (300p) onto a flexible substrate (200) to form an electrically conductive layer (300) in a circuit pattern (P1) comprising ∘ an electrode pad area (301) for transceiving electrical signals (E) via the skin (S), and ∘ a circuit lane (302) electrically connected to the electrode pad area (301) for guiding the electrical signals (E) along the flexible substrate (200); - printing, coating or dispensing an adhesive composition (401p) onto the printed electrode pad area (301) to form an adhesive interface layer (401) in an adhesive pattern (P2), wherein the adhesive interface layer (401) is conductive for, in use, maintaining an electrical connection for the electrical signals (E) between the electrode pad area (301) and the skin (S), wherein the adhesive interface layer (401) is a dry film formed from the adhesive composition (401p) comprising an ionically conductive pressure sensitive adhesive composition comprising a resin (R), an ionic liquid (I), and optionally electrically conductive particles (P), wherein the resin comprises a (meth)acrylate resin comprising a (meth)acrylate monomer having a hydroxy-group in a range of 10-65% by weight of the total (meth)acrylate resin, and wherein the ionic liquid is a salt which is liquid at temperatures of 100° C or below.
  2. The method according to claim 1, wherein the ionically conductive pressure sensitive adhesive composition comprises electrically conductive particles (P) and wherein the electrically conductive particles (P) are graphite and/or carbon based.
  3. The method according to claim 1 or 2, wherein the electrically conductive particles (P) are comprised in a range of 0.1 to 35% by weight relative to the total weight of the ionically conductive pressure sensitive adhesive composition.
  4. The method according to any of the preceding claims, wherein the ionically conductive pressure sensitive adhesive composition further comprises a polyether polyol in a range between 0.1 to 35% by weight of the ionically conductive pressure sensitive adhesive composition.
  5. The method according to any of the preceding claims, wherein the adhesive composition (401p) further comprises a solvent, and wherein the dry film of the adhesive interface layer is formed by evaporation of the solvent following the printing, coating, or dispensing.
  6. The method according to any of the preceding claims, wherein a combined thickness (T) of the flexible substrate (200), the electrically conductive layer (300) at the electrode pad area (301), and the adhesive interface layer (401), and their respective material compositions, are adapted to provide a combined stiffness at the electrode pad area (301) in plane of the flexible substrate (200) of less than two hundred thousand Newton per meter, more preferably below ten thousand Newton per meter.
  7. The method according to any of the preceding claims, wherein an electrically insulating composition (311p) is printed in a skin insulating pattern (P3) to form a skin insulating layer (311) covering at least part of the circuit lane (302) adjacent the electrode pad area (301) for, in use, electrically insulating the circuit lane (302) from the skin (S).
  8. The method according to claim 7, wherein the conductive ink (300p) is printed in a skin shielding pattern (P7) to form a skin shielding layer (321), for, in use, shielding the electrically conductive layer (300) from electromagnetic interference, wherein a skin insulating layer (311) is arranged between the skin shielding layer (321) and the circuit lane (302) for electrically insulating the skin shielding layer (321) from the electrically conductive layer (300).
  9. The method according to any of the preceding claims, wherein a dielectric adhesive composition (402p) is printed in an electrically insulating adhesive pattern (P4) to form an electrically insulating adhesive layer (402) on the flexible substrate (200) and/or the circuit lane (302) at areas adjacent the adhesive pattern (P2) for, in use, improving the adhesion of the electrode (100) on the skin (S).
  10. The method according to any of the preceding claims, wherein the conductive ink (300p) is printed in an exterior shielding pattern (P5) to form an exterior shielding layer (322) on the flexible substrate (200) before printing the electrically conductive layer (300), for, in use, shielding the electrically conductive layer (300) from exterior electromagnetic interference.
  11. The method according to any of the preceding claims, wherein the skin shielding layer (321) is electrically connected to the exterior shielding layer (322).
  12. The method according to any of the preceding claims, wherein the flexible substrate (200) is cut according to a substrate cut pattern (P8), wherein the circuit pattern (P1) forms a subset area of the substrate cut pattern (P8).
  13. The method according to any of the preceding claims, comprising manufacturing a plurality of the electrodes (100) on a common flexible substrate (200).
  14. The method according to claim 13, wherein the electrodes (100) are arranged according to a predefined electrode pattern for transceiving a plurality of electrical signals (E) at respective areas of the skin (S).
  15. The method according to claim 13 or 14, wherein the electrode pattern comprises at least three electrodes (100) for measuring ECG signals via the skin (S).
  16. The method according to any of claims 13 - 15, wherein areas between the electrode pad areas (301) are covered by the electrically insulating adhesive layer (402).
  17. The method according to any of claims 13 - 16, wherein the respective circuit lanes (302) of the electrodes converge at a common external connection area (303).
  18. The method according to any of claims 13 - 17, wherein the electrode pattern forms a two-dimensional array of spaced apart electrode pad areas (301) with respective circuit lanes (302)
  19. A skin-compatible electrode (100), manufactured according to any of the preceding claims, the electrode (100) comprising: - a flexible substrate (200); - an exterior shielding layer (322) formed by a conductive ink (300p) printed in an exterior shielding pattern (P5) onto the flexible substrate (200); - an exterior insulating layer (312) formed by a dielectric composition (311p) printed in an intermediary insulating pattern (P6) onto the exterior shielding layer (322); - an electrically conductive layer (300) formed by the conductive ink (300p) printed in a circuit pattern (P1) onto the exterior insulating layer (312), the circuit pattern (P1) comprising ∘ an electrode pad area (301) for transceiving electrical signals (E) via the skin (S), and ∘ a circuit lane (302) electrically connected to the electrode pad area (301) for guiding the electrical signals (E) along the flexible substrate (200); - a skin insulating layer (311) formed by a dielectric composition (311p) printed in a skin insulating pattern (P3) onto at least part of the circuit lane (302); - a skin shielding layer (321) formed by the conductive ink (300p) printed in a skin shielding pattern (P7), wherein the skin insulating layer (311) is arranged between the skin shielding layer (321) and the circuit lane (302); - an adhesive interface layer (401) formed by a dry film of an adhesive composition (401p) coated or dispensed in an adhesive pattern (P2) on the electrode pad area (301), wherein the adhesive composition (401p) comprises an ionically conductive pressure sensitive adhesive composition comprising a resin (R), an ionic liquid (I), and optionally electrically conductive particles (P), wherein the resin comprises a (meth)acrylate resin comprising a (meth)acrylate monomer having a hydroxy-group in a range of 10-65% by weight of the total (meth)acrylate resin, and wherein the ionic liquid is a salt which is liquid at temperatures of 100° C or below; - an electrically insulating adhesive layer (402) formed by a dielectric adhesive composition (402p) printed in an electrically insulating adhesive pattern (P4) on the flexible substrate (200) and/or the circuit lane (302) at areas adjacent the adhesive pattern (P2).
  20. The skin-compatible electrode (100) according to claim 19, wherein a combined thickness (T) of the flexible substrate (200), the electrically conductive layer (300) at the electrode pad area (301), and the adhesive interface layer (401), and their respective material compositions, have a combined stiffness at the electrode pad area (301) in plane of the flexible substrate (200) less than two hundred thousand Newton per meter, more preferably below ten thousand Newton per meter.

Description

TECHNICAL FIELD AND BACKGROUND The present invention relates to a method for the production of ExG electrodes and patches for application to human subjects. Bio potential electrodes are used to measure bio signals such as electrocardiography (ECG), electroencephalography (EEG) and electromyography (EMG). For example, currently used ECG electrodes are connected to the skin via gel, which acts as an electrolyte and couples the electrical potential in the body to the electrode. However, presently used electrodes typically dry out over time and cannot be used for prolonged measurements. Most of the presently used electrodes are not recommended for use longer than 24h, In addition, they do not have long storage times in air. Most of the presently used electrodes expire within one month after opening the hermetic packaging preventing them from drying out during storage. Currently used gel electrodes comprise high salt concentrations, which are needed for providing low impedances and good signal quality, however at the same time they cause skin irritation with many patients. Furthermore, presently used electrodes which are based on a hydrogel contain relatively high quantities of water. The high water content is the reason why these electrodes tend to dry out over time. Presently used electrodes which are based on ionic conductivity can therefore not be used for long-term measurements (e.g. three days) since the signal quality decreases along with decreasing water content. Current gel electrodes are attached to the skin with a ring of a pressure sensitive skin adhesive surrounding the inner gel. There are also tab electrodes currently on the market, which are attached to the skin via a gel-type adhesive. These electrodes do not need an additional skin adhesive, since the gel itself is adhering to the skin. However, these electrodes also comprise a salt and water, and dry out over time and are therefore not suitable for prolonged measurements. The cohesion of the adhesive is often poor in these electrodes, which for example leads to cohesive failure upon removal of the electrode. Furthermore, production of such electrodes is laborious due to the difficult handling of the adhesive, e.g. placement of the gel film atop the conductive bottom layers. Alternatively, a pressure sensitive adhesive comprising conductive fillers, such as carbon black can be used in the electrodes to measure bio signals. The drawback in this kind of electrodes is that a high carbon black concentration is needed, which leads to reduced adhesion properties. Furthermore, the signal quality in this kind of electrodes is poor. In another electrode solution, the electrode comprises adhesives comprising the combination of carbon black and a salt. An electrophoretic alignment of conductive fillers is required in order to obtain sufficient impedances in this solution. However, this electrophoretic activation step makes the electrode production expensive and complicated. Therefore, there is a need for electrodes and a method for the production of such electrodes to measure bio signals, which mitigate one or more of the above problems. In Isik et al., Journal of Materials Chemistry C 3, 2015, 8942, Cholinium-based ion gels as solid electrolytes for long-term cutaneous electrophysiology (DOI: 10.1039/C5TC01888A) describes a skin electrode structure in which the conductive Cholinium-based ion gel is a pressure sensitive adhesive. US 6 121 508 A (BISCHOF KATHARINA J [DE] ET AL) 19 September 2000 describes a skin compatible, lipophilic, polar pressure-sensitive adhesive. US 2018/055399 A1 (MORITA TAKASHI [JP] ET AL) 1 March 2018 describes a biological electrode tool with an adhesive layer. US 7 945 302 B2 (UNIV ULSTER [GB]) 17 May 2011 discloses a system and method for mapping tissue, especially for mapping a skin wound. In Isik et al., ACS Macro Letters, vol. 2, no. 11, (DOI: 10.1021/mz400451g) discloses a biocomptible resin comprising a (meth)acrylate monomer having a hydroxy-group in a range of 10-65% by weight of the total (meth)acrylate resin. SUMMARY Aspects of the present disclosure relate to a method of manufacturing a skin-compatible electrode. Preferably, the method comprises printing a conductive ink onto a flexible substrate to form an electrically conductive layer in a circuit pattern comprising an electrode pad area and a circuit lane. The method further comprises coating, printing or dispensing an adhesive composition onto the printed electrode pad area to form an adhesive interface layer in an adhesive pattern. The adhesive interface layer may be a dry film formed from the adhesive composition comprising an ionically conductive pressure sensitive adhesive composition comprising a resin, an ionic liquid, and optionally electrically conductive particles. Furthermore, a combined thickness and sizes of the flexible or stretchable substrate, the electrically conductive layer at the electrode pad area, and the adhesive interface layer, and their r