Active soft & dry electrode

Abstract

A soft and dry electrode (1) for measuring a bioelectric signal of an individual, the electrode (1) comprising an electrode body (2), a connector side (11) with attachment means (31) for attaching the electrode (1) to a support member, and a contact side (12) opposite the connector side (11) for contacting a region of interest of the individual when applying the electrode (1) to the individual; wherein the electrode body (2) comprises a contact portion (4) of electrically conductive elastomeric material forming the contact side (12) of the electrode (1) and a connector portion (3) of electrically non-conductive material forming the connector side (11) of the electrode (1); wherein the electrode (1) further comprises a signal processing circuitry (5) enclosed between the connector portion (3) and the contact portion (4) of the electrode body (2), wherein the signal processing circuitry (5) is electrically connected to the contact portion (4); and wherein the signal processing circuitry (5) is provided with an electric connector (51) penetrating the connector portion (3) on the connector side (11).

Description

[0001] Active soft & dry electrode

[0002] Technical Field

[0003] The invention relates to an active soft and dry electrode (SDE) for detection of bioelectric signals in applications such as electroencephalography (EEG), electrocardiography (ECG) or electromyography (EMG).

[0004] Technical Background

[0005] So-called soft and dry electrodes (SDE) typically comprise an electrode body made from conductive elastomer offering high wear comfort thanks to the softness of the material. At the same time, dry signal acquisition is possible without use of conductive gels, shortening preparation time and further increasing wear comfort. Thus, SDEs are increasingly used for long term electric biopotential measurements.

[0006] The electrode body may have a connector side with attachment means for attaching the electrode to a support member of a measuring device (e.g. a headset or other interface). Electrodes with suitable attachment means are easily replaceable. With an opposite contact side, the electrode may be placed on a region of interest of an individual for picking up the biopotential signals. To transmit the signal from the individual to the measuring device, the electrode body may be made of conductive material or coated with conductive material. Such soft and dry electrodes are known from WO2022047595.

[0007] To noninvasively capture the electric potential fluctuations of an individual, two different electrode technology options are available, namely passive electrodes or active electrodes. Passive electrodes, e.g. as described in WO2022047595, are traditional electrodes that simply transmit the voltage fluctuation from the conductive electrode through a conductive wire to a signal processing unit. Active electrodes are electrodes that contain an electric circuit or components in its structure or very close to it. Unlike the traditional passive electrodes, active electrodes have built-in signal processing capabilities to improve signal to noise ratio.

[0008] WO2020255142 describes a sensing system comprising several (active) electrodes. The sensing system comprises a circuit board, e.g. a printed circuit board, and a plurality of flexible sensing legs (pins). A tip of each leg is in electrical communication with the circuit board via a conductive section. The sensing system has a rather complex structure and accordingly its manufacturing is complex. LIS2019150838 describes an active EEG sensor. The EEG sensor comprises an electrode body with several electrically conductive legs. A snap connector is attached to a connector side of the sensor for attaching the sensor to a support device. The snap connector is provided with an active electrode circuitry / PCB. The disadvantage is that the PCB is separate from the actual electrode and that good signal-to-noise ratio relies on a tight connection between the snap connector and the actual electrode.

[0009] US2020060571 describes an active electrode (sensor) for a headset comprising a sensor body and an electronic board. The sensor body is made of conductive polymeric material and includes a disc-shaped base and a set of protruding pimples. The electric board is attached to an upper side of the sensor body via a cylindrical flange that extends about the sensor body and includes a radially inner annular bead. The inner annular bead forms a recess for receiving the electronic board, which is intended to be maintained in this recess by the bead. The sensor body further comprises a radially outer annular flange, which can be used to mount the sensor in a suitable recess of a support device. Because the sensor body is simply slipped over the PCB and then fixed in the support device slightly bending the sensor may lead to interruption or changes in the electrical connection of the protruding pimples with the electronic board.

[0010] W02003079897 describes a disc-shaped active electrode. The electrode is encapsulated with an insulating layer, which is electrically resistive. The electrode possesses an internal conductive cap acting as a shield, which is “grounded” i.e. connected to the circuit reference potential, which is connected to a reference electrode. A cable carries power to, and signals from the on-board electronic circuit. The circuit is fixed on a 2-layer printed circuit board with a bottom conducting layer conveniently serving as the low resistance ohmic contact to the electrode substrate layer. The substrate layer may be of conductive rubber. The electrode has a rather complex structure, and the wire connection makes it very difficult for efficient manufacturing.

[0011] Summary of the Invention

[0012] It is an objective of the invention to design an active electrode aiming to solve the limitation of passive electrodes and improve the quality, reliability and sensitivity of the recorded signals while balancing usability and user comfort. It is a further objective to avoid the disadvantages of the known active electrodes, in particular to improve the communication between the electrode and the tissue by reducing the noises, and the motion artifacts. At the same time, the electrode design should be compact and cost-efficient for manufacturing despite the integration of electronic components.

[0013] At least one of the objectives of the present invention is achieved by a soft and dry electrode according to claim 1 and a method of manufacturing such an electrode according to claim 15. The soft and dry electrode for measuring a bioelectric signal of an individual comprises an electrode body, a connector side with attachment means for attaching the electrode to a support member and a contact side opposite the connector side for contacting a region of interest of the individual when applying the electrode to the individual. The electrode body comprises a contact portion of electrically conductive elastomeric material forming the contact side of the electrode and a connector portion of electrically non-conductive material forming the connector side of the electrode. The electrode further comprises a signal processing circuitry enclosed between the connector portion and the contact portion of the electrode body, wherein the signal processing circuitry is electrically connected to the contact portion. The signal processing circuitry is provided with an electric connector penetrating the connector portion on the connector side.

[0014] Thus, the signal processing circuitry may be firmly enclosed between two parts of the electrode body, which are made of different materials but are firmly bound together. Such a design of the electrode can be manufactured in a cost- efficient manner in that first the contact portion is moulded of a conductive rubber material. In a second step the signal processing circuitry is placed on the pre-moulded contact portion, which then in third step is over-moulded with the connector portion of non-conductive (rubber) material. Thereby a reliable electrical contact between the signal processing circuitry and the underlying contact portion is established. The electric connector of the signal processing circuitry sticks out of the electrode body on the connector side and can easily be electrically contacted by a further measurement device, while the electrode is attached to a support member via separate attachment means.

[0015] In use, the electrically conductive contact portion of the electrode contacts the individual in a region of interest and transmits a signal from the tissue of the individual to the embedded or enclosed signal processing circuitry. The signal processing circuitry pre-processes the detected signal, which is further transmitted via the electric connector to a main processing unit of an external measuring device. The connector portion electrically insulates the signal processing circuitry and its electric connector. At the same time, it provides attachment means for attaching the soft and dry electrode to a support structure.

[0016] In the context of the present invention, conductive or non-conductive means electrically conductive or electrically non-conductive, respectively. A support member may be a headset or any structure for placing the electrode on an individual. The support member may comprise or may be connected to a measuring apparatus or device. The signal processing circuitry may be a signal processing unit comprising a printed circuit board (PCB) or a flexible printed circuit board with or without surface mounted components. The signal processing circuitry may or may not have thin protective coatings or shielding layers.

[0017] The attachment means is used to connect the electrode to a support device in a stable but removable manner leaving a certain degree of flexibility. The electric connector is used to electrically connect the electrode to a main measuring device. In some embodiments the electric connector may function as attachment means as well.

[0018] The non-conductive material of the connector portion may be an elastomeric material. Thus, the electrode body comprising the connector portion and the contact portion is made of elastomeric material providing an even look and feel and which may provide additional flexibility when combined with a flexible circuit board.

[0019] The elastomeric material of the electrode may be a thermoset elastomer or a thermoplastic elastomer.

[0020] The elastomeric material can be, for example, a synthetic or natural rubber, such as butyl rubber, isoprene rubber, butadiene rubber, halogenated butyl rubber (e.g., bromobutyl rubber), ethylene propylene terpolymer, silicone rubber, fluoro- or perfluoroelastomers, chlorosulfonate, polybutadiene, butyl, neoprene, nitrile, polyisoprene, buna-N, copolymer rubbers such as ethylene-propylene (EPR), ethylene-propylene-diene monomer (EPDM), acrylonitrile-butadiene (NBR or HNBR) and styrene-butadiene (SBR), blends such as ethylene or propylene-EPDM, EPR, or NBR, combinations thereof. The term "synthetic rubbers" also should be understood to encompass materials which alternatively may be classified broadly as thermoplastic or thermosetting elastomers such as polyurethanes, silicones, fluorosilicones, styrene-isoprene-styrene (SIS), and styrene-butadiene-styrene (SBS), as well as other polymers which exhibit rubber-like properties such as plasticized nylons, polyolefins, polyesters, ethylene vinyl acetates, fluoropolymers, and polyvinyl chloride.

[0021] The conductive properties of the elastomeric material may be achieved by adding conductive material. The conductive material may be carbon black, silver coated glass spheres, silver particles, Ag-coated aluminium beads, Ag-coated glass fibres, graphene, carbon nanotubes, graphite, stainless steel fibres, or any other suitable material.

[0022] Further embodiments of the invention are set forth in the dependent claims. In some embodiments the attachment means are an integral part formed by the connector portion. The attachment means can for example be a snap-fit connector for easy fastening and removing the electrode from the support member having a corresponding attachment means. The snap-fit connector may have the form of a snap fastener or snap button. Typically, the attachment means is arranged centrally on the connector side for better balancing of the electrode and even distribution of application forces when applying the electrode to an individual. The attachment means is non-conductive and not used for electrically contacting the signal processing circuitry or the contact portion.

[0023] In some embodiments the signal processing circuitry may be provided with electric contact means, preferably a pin connector or a spot connector, on a surface facing the contact portion for establishing electric contact between the signal processing circuitry and the contact portion. Thereby, the embedded signal processing circuitry may receive a signal from the individual, which is transmitted through the contact portion. The remaining surface of the signal processing circuitry, which faces the contact portion, is electrically insulated. A pin connector may be pushed into the contact portion. A spot connector is an electrically conductive area or spot on the signal processing circuitry / unit 5, which contacts the surface of the contact portion.

[0024] In some embodiments the electric connector may be arranged on the connector side spaced apart from the attachment means. The electric connector may be a multi-pin connector, preferably a 3-pin connector, which can be easily connected via standard wiring.

[0025] In some embodiments the connector portion and the contact portion may be bonded to each other directly via covalent bonds or indirectly via an adhesive. The materials for the electrode body may be thermosetting (vulcanizable) materials to provide chemical bonding between the connector portion and the contact portion.

[0026] In some embodiments the contact side of the contact portion may have a planar surface or may be provided with several flexible contact pins for contacting a region of interest of the individual when the electrode is in use. The planar surface or the tips of the contact pins may be provided with an additional conductive coating, e.g. an Ag / AgCI coating to increase conductivity at the interface.

[0027] In some embodiments the signal processing circuitry may be a printed circuit board (PCB) or a flexible printed circuit board. The signal processing circuitry may comprise a processing component such as an amplifier and / or a digitizer.

[0028] In some embodiments the contact portion and / or the signal processing circuitry may be provided with positioning means for positioning the signal processing circuitry in a defined position relative to the contact portion. The positioning means may be a protrusion on the contact portion engaging into an opening of the signal processing circuitry or the circuit board of the signal processing circuitry.

[0029] In some embodiments the contact portion and / or the connector portion may have a circular shape.

[0030] In some embodiments the contact portion may comprise a circumferential skirt projecting towards the connector side and / or the connector portion comprises a circumferential skirt projecting towards the contact side. The circumferential skirt of one portion may abut on a circumferential surface of the other part and be bonded thereto. Alternatively, if both portions have circumferential skirts, the circumferential skirt of the connector portion may overlap the circumferential skirt of the contact portion. In other words, the two skirts may overlap with each other leading to a larger surface area for firm bonding of the two portions.

[0031] In some embodiments a side surface of the electrode body is formed by the non-conductive connector portion.

[0032] In some embodiments the soft and dry electrode may be manufactured by injection moulding, compression moulding, injection transfer moulding or compression transfer moulding.

[0033] The invention also relates to a process for manufacturing the above described soft and dry electrode. The process comprises the steps of: (a.) moulding the contact portion of conductive elastomer; (b.) placing the signal processing circuitry onto the pre-moulded contact portion; and (c.) over-moulding the signal processing circuitry with the connector portion of non-conductive material and thereby bonding the connector portion to the contact portion.

[0034] In some embodiments of the process the connector portion and the contact portion may be made of vulcanizable (thermosetting) material, and wherein the contact portion may be only partially vulcanized or cross-linked in step a) and in step c) the contact portion and the connector portion are fully vulcanized or cross-linked to form covalent bonds between each other.

[0035] A preferred process for manufacturing the soft and dry electrode may thus comprise the following steps. In a first step the connector portion is injection moulded. After moulding the injection moulding tool is opened and the connector portion remains in the tool half forming the contact side of the contact portion. In a second step, the signal processing circuit I unit is placed onto the contact portion. The signal processing circuit I unit may be positioned using positioning means formed by the contact portion, e.g. in the form of a protrusion fitting into an opening of the signal processing circuit I unit. In a third step, the mould is closed using a different mould half forming a cavity for over-moulding the signal processing circuit I unit and parts of the contact portion with the connector portion.

[0036] Fully vulcanized or cross-linked is understood as the desired degree of vulcanization or cross-linking in the final product and not necessarily the full degree, which may be chemically possible.

[0037] In some embodiments the contact portion and the connector portion are injection moulded.

[0038] Brief Explanation of the Figures

[0039] The invention is described in greater detail below with reference to embodiments that are illustrated in the figures. The figures show:

[0040] Fig. 1 a perspective view onto a connector side of a soft and dry electrode;

[0041] Fig. 2 a perspective view onto a contact side of the soft and dry electrode of Fig. 1 ;

[0042] Fig. 3 a side view of the soft and dry electrode of Fig. 1 ;

[0043] Fig. 4 a cross-section of the soft and dry electrode of Fig. 1 ;

[0044] Fig. 5 an exploded view of the soft and dry electrode of Fig. 1 ;

[0045] Fig. 6 a cross-section of a variant of the soft and dry electrode;

[0046] Fig. 7 a cross-section of a further variant of the soft and dry electrode.

[0047] Embodiments of the Invention

[0048] Figs. 1 to 5 show a first embodiment of an active, soft and dry electrode 1 (electrode or SDE) in different views. The soft and dry electrode 1 comprises an elastomeric electrode body 2, which in the shown embodiments consists of two elastomeric portions 3, 4, namely a connector portion 3 and a contact portion 4, firmly bound together. The connector portion 3 forms a connector side 11 of the electrode 1 and is made of electrically non-conductive elastomer material. The contact portion 4 forms a contact side 12 of the electrode 1 and is made of electrically conductive elastomer material. Such conductive elastomer material is known in the art. In use, the contact portion 4 contacts an individual for picking up and transmitting bioelectric signals to a signal processing circuitry.

[0049] Fig. 1 and Fig. 2 are perspective views of the electrode 1 onto the connector side 11 and the contact side 12, respectively. Fig. 3 show a side view of the electrode. In the shown embodiment the two portions 3, 4 have a circular shape. Other shapes, e.g. oval or rectangular are also possible.

[0050] The connector portion 3 is provided with attachment means 31 in the form of a snap-fit button. Such attachment means 31 are known in the art for attaching the electrode 1 to a corresponding attachment means of a support device. In the present embodiment the snap- fit button is arranged centrally on the connector side 11 of the connector portion 3 to evenly propagate pressure when the electrode is placed on an individual.

[0051] In the shown embodiment, the contact portion 4 is provided with several flexible contact pins 41 having a conical base and cylindrical ends. The contact pins 41 may bend when applying the electrode on an individual and may slide through hair (if present) to form proper contact with the individual.

[0052] Also visible on the connector side 11 of the shown electrode 1 is an electric connector 51. In the shown embodiment, the electric connector 51 is a 3-pin connector. The electric connector 51 is connected to a signal processing circuitry 5 (shown in Fig. 4) and protrudes through the connector portion 3 of the electrode body 2. The pins of the electric connector 51 can be contacted by a measuring device. In the shown embodiment, the electric connector 51 is arranged next to the snap-fit button.

[0053] The active electrode further comprises a signal processing circuitry or unit 5, which is firmly embedded or enclosed between the connector portion 3 and the contact portion 4 of the elastomeric electrode body 2. Fig. 4 shows a cross-section of the soft and dry electrode 1 and Fig. 5 shows an exploded view of the soft and dry electrode 1 . In Fig. 4 and Fig. 5 the signal processing circuitry or unit 5 is visible. The signal processing circuitry I unit 5 is a printed circuit board (PCB) or a flexible printed circuit board with or without surface mounted components.

[0054] The signal processing circuitry I unit 5 electrically contacts the contact portion 4 via electric contact means 53 (not shown). The electric contact means 53 are located on the surface 54 on contact side of the signal processing circuitry I unit 5 and may be a pin connector or a spot connector. A pin connector may be pushed into the contact portion 4. A spot connector is an electrically conductive area or spot on the signal processing circuitry I unit 5, which contacts the surface of the contact portion 4.

[0055] The connector portion 3 and the contact portion 4 of the electrode body 2 are firmly bound with each other. The bonding may be achieved via an adhesive layer or via covalent bonding during the manufacturing. In the embodiment of Fig. 4 the contact portion 4 is provided with a circumferential skirt 41 protruding in a direction towards the connector portion 3. The connector portion 3 is also provided with a circumferential skirt 31 protruding in a direction towards the contact portion 4. The circumferential skirt 31 of the connector portion 3 has a larger diameter than the circumferential skirt 41 of the contact portion 4 and forms an outer side surface of the electrode 1. With such a structure the bonding area between the two portions is increased compared to two other embodiments as described below (Figs. 6 and 7).

[0056] Fig. 6 shows a cross-section of a variant of the soft and dry electrode. In this embodiment, only the connector portion 3 is provided with the circumferential skirt 31. Fig. 7 shows a cross-section of a further variant of the soft and dry electrode. In this embodiment, only the contact portion 4 is provided with the circumferential skirt 41.

[0057] Reference Signs

[0058] 1 soft and dry electrode (SDE)

[0059] 11 connector side

[0060] 12 contact side

[0061] 2 electrode body

[0062] 3 connector portion

[0063] 31 attachment means

[0064] 33 circumferential skirt

[0065] 4 contact portion

[0066] 41 flexible contact pins

[0067] 42 positioning means

[0068] 43 circumferential skirt

[0069] 5 signal processing circuitry I unit

[0070] 51 electric connector

[0071] 52 positioning means

[0072] 53 electric contact means

[0073] 54 surface on contact side

Claims

Claims1. Soft and dry electrode (1) for measuring a bioelectric signal of an individual, the electrode (1) comprising an electrode body (2), a connector side (11) with attachment means (31) for attaching the electrode (1) to a support member, and a contact side (12) opposite the connector side (11) for contacting a region of interest of the individual when applying the electrode (1) to the individual; characterized in that the electrode body (2) comprises a contact portion (4) of electrically conductive elastomeric material forming the contact side (12) of the electrode (1) and a connector portion (3) of electrically non-conductive material forming the connector side (11) of the electrode (1); in that the electrode (1) further comprises a signal processing circuitry (5) enclosed between the connector portion (3) and the contact portion (4) of the electrode body (2), wherein the signal processing circuitry (5) is electrically connected to the contact portion (4); and in that the signal processing circuitry (5) is provided with an electric connector (51) penetrating the connector portion (3) on the connector side (11).

2. Soft and dry electrode according to claim 1 , wherein the attachment means (31) are an integral part formed by the connector portion (3).

3. Soft and dry electrode according to one of the preceding claims, wherein the attachment means (31) are formed as a snap-fit connector, preferably in the form of a snap fastener or snap button.

4. Soft and dry electrode according to one of the preceding claims, wherein the signal processing circuitry (5) is provided with electric contact means (53), preferably a pin connector or a spot connector, on a surface (54) facing the contact portion (4) for establishing electric contact between the signal processing circuitry (5) and the contact portion (4).

5. Soft and dry electrode according to one of the preceding claims, wherein the electric connector (51) is arranged on the connector side (11) spaced apart from the attachment means (31).

6. Soft and dry electrode according to one of the preceding claims, wherein the connector portion (3) and the contact portion (4) are bonded to each other directly via covalent bonds or indirectly via an adhesive.

7. Soft and dry electrode according to one of the preceding claims, wherein the contact side (12) of the contact portion (4) has a planar surface or is provided with several flexible contact pins (41).

8. Soft and dry electrode according to one of the preceding claims, wherein the signal processing circuitry (5) is a printed circuit board or a flexible printed circuit board.

9. Soft and dry electrode according to one of the preceding claims, wherein the contact portion (4) and / or the signal processing circuitry (5) is provided with positioning means (42, 52) for positioning the signal processing circuitry (5) in a defined position relative to the contact portion (4).

10. Soft and dry electrode according to one of the preceding claims, wherein the contact portion (4) and / or the connector portion (3) have a circular shape.

11. Soft and dry electrode according to one of the preceding claims, wherein the contact portion (4) comprises a circumferential skirt (43) projecting towards the connector side (11) and / or the connector portion (3) comprises a circumferential skirt (33) projecting towards the contact side (12).

12. Soft and dry electrode according to one of the preceding claims, wherein the circumferential skirt of the connector portion overlaps the circumferential skirt of the contact portion.

13. Soft and dry electrode according to one of the preceding claims, wherein a side surface of the electrode body (2) is formed by the non-conductive connector portion (3).

14. Soft and dry electrode according to one of the preceding claims, wherein the connector portion (3) is made of electrically non-conductive material.

15. Process for manufacturing the soft and dry electrode according to one of the preceding claims, the process comprising the steps of: a. moulding the contact portion (4); b. placing the signal processing circuitry (5) onto the pre-moulded contact portion (4); c. over-moulding the signal processing circuitry (5) with the connector portion (3) and thereby bonding the connector portion (3) to the contact portion (4).

16. Process according to claim 15, wherein the connector portion (3) and the contact portion (4) are made of vulcanizable material, and wherein in step a) the contact portion (4) is only partially vulcanized or cross-linked and in step c) the contact portion (4) and the connector portion (3) are fully vulcanized or cross-linked to form covalent bonds between each other.

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