Soft dry electrode

Abstract

A flexible electrode (1) for measuring a bioelectric signal of an individual is made of an elastomeric material and has conductive properties and comprises a central connector portion (2) having attachment means for attaching the electrode (1) to a measuring device and a plurality of flexible contact members (3); the electrode (1) having a connector side (11) on the attachment device side and a contact side (12) opposite the connector side (11) and facing the individual when the electrode (1) is applied to the individual; the connector portion (2) further defines a central axis (A) of the electrode (1), the central axis (A) being arranged centrally through the contact side (12) and the connector side (11) of the electrode (1); wherein a plurality of contact members (3) are arranged around the central axis (A) and connected with the connector portion (2), the plurality of contact members (3) also protruding at a contact side (12) of the connector portion (2) to contact an individual region of interest for measurement; wherein each contact member (3) of the plurality of contact members (3) comprises a flexible leg portion (31) and a foot portion (32) at a free end (33) of the flexible leg portion (31); wherein the flexible leg portion (31) has a longitudinal cavity (4) formed by an inner wall (34) bent about a longitudinal axis (L) of the contact member (3), wherein the longitudinal cavity remains open on the connector side (11) and is closed by the foot portion (32) on the contact side (12); and wherein the foot portion (32) and the flexible leg portion (31) form a continuous radially inner contact surface (5).

Description

Technical Field

[0001] The present invention relates to a soft dry electrode for detecting bioelectric signals in applications such as electroencephalography (EEG), electrocardiography (ECG) or electromyography (EMG). Background Art

[0002] Commercially available "dry" EEG headsets are usually equipped with metal dry electrodes, which can cause pain to the subject after wearing the headset for a while. One possible solution is to combine such electrodes with a spring-like system to avoid high skin pressure.

[0003] Another approach is to use soft polymer-based dry electrodes. By mixing elastic polymers with additives, the conductivity can be increased while maintaining the elasticity required for high user comfort. The polymer-based dry electrodes can have a comb-shaped design (fingers or legs) to improve skin contact on hairy skin (e.g. on the scalp). Such fingers or legs can have at least a partial coating on the surface of the electrode that contacts the skin in order to reduce skin impedance and provide improved signal quality.

[0004] Therefore, soft dry electrodes are increasingly used for long-term biopotential measurements, such as EEG and ECG. In addition to being soft, the additional fact that such electrodes can be applied without the use of conductive gels provides considerable benefits to the measurement process, such as reducing the risk of skin irritation and avoiding degradation of signal quality due to drying of the gel.

[0005] Examples of such soft dry electrodes are described by Chen et al. in “Polymer-based dry electrodes for high user comfort ECG / EEG measurements” (Chen, Yun-Hsuan; Op de Beeck, Maaike; Carrette, Evelien; Vanderheyden, Luc; Grundlehner, Bernard; Mihajlovic, Vojkan; Boon, Paul; Van Hoof, Chris; Apprimus Verlag; Aachen; 8th International Conference and Exhibition on Miniaturized System Integration Issues - MEMS, NEMS, ICs and Electronic Components; 2014; pp. 329–336), and by Chen et al. in “Soft, Comfortable Polymer Dry Electrodes for High Quality ECG and EEG Recordings” (Chen, Yun-Hsuan; Op de Beeck, Maaike; Carrette, Evelien; Vanderheyden, Luc; Grundlehner, Bernard; Mihajlovic, Vojkan; Boon, Paul; Van Hoof, Chris; Apprimus Verlag; Aachen; 8th International Conference and Exhibition on Miniaturized System Integration Issues - MEMS, NEMS, ICs and Electronic Components; 2014; pp. 329–336). Recording)" (Journal of Sensors 2014, 14, 23758-23780; doi (Digital Object Identifier): 10.3390 / s141223758) or described in WO2016080804.

[0006] These soft dry electrodes include a substrate and a plurality of pins for contacting the area of ​​interest to be measured. The pins may have a tapered portion and a protruding portion. The electrode tip is made of a flexible or soft matrix material provided with a conductive material. The electrode may have a knob on the upper side of its substrate opposite to the pins for electrical connection to the electrode.

[0007] When force is applied to the soft electrode (eg, via a strap, cuff, headset, or head cover), the legs may move in an uncontrolled manner, failing to provide the intended wiping function of brushing hair aside to achieve direct contact between the electrode and the skin surface.

[0008] One possible solution to this problem is pre-orientation of the legs (as described in EP2827770) so that when the electrodes are applied to a target area (e.g. the scalp), the legs are arranged at a non-perpendicular angle to the target area. However, a disadvantage of this approach is that the manufacturing process employed, involving a 3D printing step, is not suitable for scalability to large-scale production.

[0009] JP2019097733 relates to an electrode for measuring brain activity. The electrode has a rigid support body and a plurality of arms attached to the sides of the rigid support body. Balls are formed at the ends of the arms to contact a person's scalp. The arms are flexible and bend when force is applied to the electrode. The electrode has a complex shape with multiple undercuts, which makes it difficult to manufacture in a low-cost manner.

[0010] WO2022047595 describes a soft dry electrode having a flexible support body and a plurality of pins parallel to the central axis of the support body. When a force is applied to the top surface of the support body, the flexible support body begins to bend so that the ends of the pins or legs move in an outward direction (ie away from the center of the electrode) so as to "wipe away" any hair that obstructs direct contact between the electrode and the exposed skin surface of the individual to be measured. Summary of the invention

[0011] One object of the present invention is to provide a soft dry electrode for measuring bioelectric signals of an individual, which overcomes the problems of the prior art and is suitable for mass production. Another object of the present invention is to improve the form of the soft dry electrode to increase the ability to rub through the hair so as to optimize the contact between the end of the pin and the scalp / body of the individual.

[0012] At least one object of the present invention is achieved by a soft dry electrode according to claim 1. A soft dry electrode for measuring bioelectric signals of an individual is made of an elastomeric material and has conductive properties. The electrode comprises a central connector portion and a plurality of flexible contact members, the central connector portion having an attachment device for attaching the electrode to a measuring device. The electrode has a connector side located on one side of the attachment device and a contact side opposite to the connector side and facing the individual when the electrode is applied to the individual. The connector portion also defines a central axis of the electrode, which is arranged to pass through the contact side and the connector side of the electrode along the center. A plurality of contact members are arranged around the central axis and connected to the connector portion. A plurality of contact members also protrude on the contact side to contact the area of ​​interest of the individual for measurement. Each of the plurality of contact members comprises (or may consist of) a flexible leg portion and a foot portion located at the free end of the flexible leg portion. The flexible leg portion has a longitudinal cavity formed by an inner wall bent around the longitudinal axis of the contact member, wherein the longitudinal cavity remains open on the connector side and is closed by the foot portion on the contact side. The foot portion and the flexible leg portion form a continuous radially inner contact surface.

[0013] Therefore, the inner wall of the flexible leg portion of the electrode can be smoothly transformed into the structure of the foot portion. The manufacture of the electrode does not require the use of complex tools due to the presence of, for example, undercuts. At the same time, due to the weakening of the curved wall, the "hollow" structure of the leg portion, i.e., the presence of a longitudinal cavity, the high flexibility of the leg portion is maintained. This enables the contact member to bend when the electrode is placed on an individual with its contact side and a force is applied to the connector side. Due to the weakening of the leg portion on the radially outer side, it is possible to bend in a manner that allows the foot portion to move in a radially outward direction along the skin of the individual and can rub the hair. Therefore, the continuous radially inner contact surface does not have an edge, a step, or a sudden change in curvature, so that when a force is applied to the connector side of the electrode, even if the actual contact area moves along the contact surface, the contact member can also move smoothly along the skin of the individual. In addition, by setting the inclination angle between the radially inner contact surface of the contact member and the central axis of the electrode, the outward movement of the foot portion when pressure is applied to the connection side can be further promoted. Therefore, the contact member can be opened toward the end portion so that the contact member moves radially outward when contacting the area of ​​interest of the individual.

[0014] The foot portion may be more rigid (or less flexible) than the flexible leg portion, but since the electrode is made of an elastomeric material, the foot portion still remains flexible. This can be achieved by a solid design of the foot portion without a cavity or "hollow" structure. Bending of the contact member occurs along the leg portion.

[0015] In the context of the present invention, "upper" refers to the connector side of the electrode and "lower" refers to the contact side of the electrode. "Radial" refers to a direction relative to the central axis of the electrode. The longitudinal axis of the contact member generally runs through the center of the foot portion and longitudinally along or through the leg portion, or in other words, along the longitudinal axis of the longitudinal cavity. The inclination angle of the contact surface can be determined along the radially innermost line of the curved inner wall. The contact surface can be a surface of the inner wall that faces radially inward and can contact the individual when the contact member is bent due to a force applied to the connector side.

[0016] Further embodiments of the invention are set forth in the dependent claims.

[0017] In some embodiments, the electrodes may be made of an elastomeric material provided with a conductive additive and / or at least partially coated with a conductive coating.

[0018] In some embodiments, the radially inner contact surface may be inclined, and the inclination angle between the radially inner contact surface and the central axis of the electrode is approximately 10 degrees to 45 degrees, and open on the contact side.

[0019] In some embodiments, good results have been achieved with an angle of inclination between the radially inner contact surface and the central axis of the electrode of about 15 to 25 degrees, preferably about 17.5 to 20 degrees.

[0020] In some embodiments, the inclination angle of the contact surface can increase continuously from the lower end of the leg portion to the lower end of the foot portion, preferably to about 35 to 45 degrees, more preferably to about 20 to 35 degrees. When force is applied and the leg portion begins to bend, the inclination angle of the contact member continuously increases toward the end of the contact member to facilitate the foot portion to slide along the skin of the individual. Therefore, according to the degree of bending of the contact member, the actual contact area of ​​the contact member can move from the end of the foot portion toward the inner side of the foot portion and the lower inner side of the leg portion.

[0021] In some embodiments, the contact surface has an increased inclination angle only at the foot portion and is substantially parallel to the central axis at at least the upper portion of the contact member, ie has an inclination angle of about zero or close to zero.

[0022] In some embodiments, the thickness of the curved inner wall can decrease in the radially outward direction. Therefore, when a force is applied to the connector side, the radially outer portion of the inner wall can be more easily twisted and deformed, thereby improving the bending behavior of the leg portion.

[0023] In some embodiments, the foot portion may extend in a radially outward direction on an inner wall of the leg portion.

[0024] In some embodiments, the leg portion may further include a curved outer wall, the curved outer wall and the curved inner wall together forming a longitudinal cavity of the leg portion, the longitudinal cavity having an opening toward the connector side of the electrode. In this way, the longitudinal cavity of the leg portion is formed by the circumferential wall. The thickness of the curved outer wall may be less than the thickness of the curved inner wall.

[0025] In some embodiments, the outer surface of the inner wall and / or the outer surface of the outer wall is transformed into the outer surface of the foot portion to form a continuous outer surface of the contact member. In other words, the entire contact member, i.e. the leg portion and the foot portion, forms a smooth outer surface. In the context of the present invention, the outer surface is the surface of the convex side of the inner wall or outer wall of the corresponding part that faces away from the longitudinal axis and thus forms the leg portion.

[0026] In some embodiments, each leg portion may be connected to an adjacent leg portion at the upper end of the leg portion, thereby increasing the stability of the electrode on its connector side.

[0027] In some embodiments, the contact member tapers toward the foot portion such that the size of the cross-section continuously decreases.

[0028] In some embodiments, the upper surface of the contact member may form a dome-shaped upper surface together with the connector portion.

[0029] In some embodiments, a circumferential step may be formed between the connector portion and the plurality of contact members. Such a step enhances the bending behavior of the electrode and reduces the required force.

[0030] In some embodiments, the plurality of contact members form a dome-shaped upper wall. The plurality of contact members may also form a flat upper wall perpendicular to the central axis.

[0031] In some embodiments, the attachment means may be a knob formed by the connector portion of the electrode or a rigidly connected insert embedded in the connector portion of the electrode.

[0032] In some embodiments, the longitudinal cavity has a semi-oval, semi-elliptical, oval, or elliptical cross-section.

[0033] In some embodiments, the longitudinal cavity may be open or closed in the radially outward direction.

[0034] In some embodiments, the electrode may include six to twelve contact members, preferably eight contact members, spaced about a central axis.

[0035] In some embodiments, a plurality of contact members may be regularly arranged around a central axis of the electrode.

[0036] In some embodiments, the connector portion and the plurality of contact members of the electrode may be integrally formed as a single unitary body of elastomeric material, with or without a rigid insert in the connector portion.

[0037] In some embodiments, the electrodes may have a diameter of 8 mm to 25 mm (around the central axis A) and a length of 6 mm to 25 mm (along the central axis).

[0038] In some embodiments, the contact member may have a length of 4 mm to 20 mm and an average cross-section of 1.5 mm to 3.5 mm in the radial and / or tangential directions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Below, the present invention is described in more detail with reference to the embodiments shown in the accompanying drawings. These drawings show:

[0040] FIG1 shows a first embodiment of a soft electrode, FIG1(a) is a perspective view of a connector side, FIG1(b) is a perspective view of a contact side, FIG1(c) is a top view of a connector side, FIG1(d) is a side view, FIG1(e) is a cross section taken along C1-C1 as shown in FIG1(c), and FIG1(f) is a cross section taken along C2-C2 as shown in FIG1(c);

[0041] FIG2 shows a second embodiment of a soft electrode, FIG2(a) is a perspective view of a connector side, FIG2(b) is a perspective view of a contact side, FIG2(c) is a top view of a connector side, FIG2(d) is a side view, FIG2(e) is a cross section taken along C1-C1 as shown in FIG2(c), and FIG2(f) is a cross section taken along C2-C2 as shown in FIG2(c);

[0042] Figure 3 shows a third embodiment of the soft electrode, Figure 3(a) is a perspective view of the connector side, Figure 3(b) is a perspective view of the contact side, Figure 3(c) is a top view of the connector side, Figure 3(d) is a side view, Figure 3(e) is a cross-section taken along C1-C1 as shown in Figure 3(c), and Figure 3(f) is a cross-section taken along C2-C2 as shown in Figure 3(c). DETAILED DESCRIPTION

[0043] Figures 1, 2 and 3 show three embodiments of a soft electrode 1 for measuring bioelectric signals of an individual. The electrode 1 is made of an elastomeric material to obtain a soft and flexible electrode and has conductive properties so as to be able to measure even tiny electrical signals on the skin of an individual. The electrode 1 comprises a central connector part 2 and a plurality of flexible contact members 3. The central connector 2 is provided with an attachment means (not shown) for attaching the electrode to a measuring device, such as a headset, for example in the form of an integral knob or in the form of an embedded insert with, for example, a knob. Such attachment means are known in the art.

[0044] In the embodiment shown, the electrode has eight contact members arranged at regular intervals around a central axis.

[0045] The electrode 1 further defines a connector side 11 on the side of the attachment device and a contact side 12 opposite the connector side 11, and when the electrode 1 is correctly applied, the contact side 12 faces the individual, that is, the connector side 11 faces away from the individual. Thus, the electrode is placed with the contact side facing the individual. The device or headset applies a force to the connector side 11 of the electrode 1, thereby pressing the contact side 12 of the electrode 1 against the individual.

[0046] The central connector part 2 defines a central axis A of the electrode 1, which passes through the connector side 11 and the contact side 12. A plurality of contact members 3 are regularly arranged around the central axis A and connected to the connector part 2. The connector members 3 protrude from the connector part 2 at the contact side 12 and, when the electrode 1 is correctly applied, the contact members 3 contact the contact area of ​​interest of the individual. The connector side 11 with the attachment means faces away from the contact area of ​​the individual.

[0047] Each of the plurality of contact members 3 comprises a flexible leg portion 31 and a more rigid foot portion 32 at a free end 33 of the flexible leg portion 31. The foot portion 32 is rigid compared to the flexible leg portion 31, but since the electrode 1 is made of an elastomeric material, the foot portion 32 remains elastic. The flexible leg portion comprises a longitudinal cavity 4 so that the flexible leg portion 31 can bend more easily when pressure is applied to the connector side 11 of the electrode 1. The longitudinal axis L is defined by the protruding contact member 3 and the longitudinal cavity 4 of the leg portion 31. The longitudinal cavity 4 is formed by at least a curved inner wall 34 that is curved around the longitudinal axis L of the contact member 3.

[0048] The outer surface of the inner wall 4, i.e., the surface facing the central axis A, forms a continuous surface with the outer surface of the leg portion 32. In other words, the outer surface of the leg portion 31 smoothly transforms into the outer surface of the leg portion 32. A continuous radially inner contact surface 5 is formed along the innermost outer surface of the contact member. When pressure is applied to the connector side 11, different areas of the contact surface 5 may contact the individual, depending on the degree of curvature of the contact member 3.

[0049] The radially inner contact surface 5 is inclined relative to the central axis A of the electrode 1. The inclination angle α between the radially inner contact surface 5 and the central axis A is approximately 15 to 25 degrees. In the embodiment shown in Figures 1-3, the inclination angle α is approximately 18 degrees. The inclination angle α is open toward the contact side 12, so that when pressure is applied to the connector side 11 and the electrode is pressed onto the individual with the contact side 12, the foot portion 32 slides in a radially outward direction. Therefore, the more rigid foot portion 32 can slide along the skin / scalp of the individual and rub the hair (if there is hair). At the same time, the actual contact area on the contact member 3 increases and / or moves upward along the contact member 3, that is, moves toward the connector side 11.

[0050] In order to achieve stability in the region of the connector part 2 , the upper end of the inner wall 34 of the leg part 31 may be connected to the upper end of the inner wall 34 of the leg part 31 of an adjacent leg part 31 .

[0051] The longitudinal cavity 4 remains open on the connector side 11 but is closed on the contact side 12 by the foot portion 32. The contact member 3 tapers towards the foot portion 32 so that the size of the cross section decreases continuously. The design of the electrode has no undercuts and therefore allows manufacturing with the aid of a fairly simple mold using only two mold halves.

[0052] 1-3, the angle of inclination is constant from the upper end of the leg portion 31 to approximately the middle of the leg portion 31. The angle of inclination then increases continuously to approximately 45 degrees toward the lower end of the foot portion 32. When a force is applied to the connector side 11 and the leg portion 31 begins to bend outwardly, the foot portion 32 is effectively directed in a radially outward direction.

[0053] The thickness of the curved inner wall 34 may decrease toward the outer side of the electrode. Therefore, the curved inner wall 34 is less flexible on the inner side than on the outer side, thereby further facilitating the leg portion 32 to be guided to move outward.

[0054] In the embodiment shown in FIG. 1 , the longitudinal cavity 4 of the contact member 3 is open radially outward. The leg portion 31 is formed only by the inner wall 34. The foot portion 32 extends radially outward on the inner wall 34 of the leg portion 31. The inner wall has a U-shaped cross section and is open radially outward. The cavity 4 has a semi-oval or semi-elliptical cross section. The foot portion 32 has an oval or elliptical cross section.

[0055] In the embodiment shown in FIGS. 1 and 2 , the plurality of contact members 3 may form a dome-shaped upper wall.

[0056] Compared to the embodiment shown in FIG. 1 , in the embodiment shown in FIG. 2 and FIG. 3 , the longitudinal cavity 4 of the contact member 3 is closed radially outwardly by a curved outer wall 35 that is curved around the longitudinal axis L. The curved inner wall 34 and the curved outer wall 35 together form the longitudinal cavity 4 of the leg portion 31 , which has an opening toward the connector side 11 . The contact side 12 of the longitudinal cavity 4 is closed by the foot portion 32 . The outer surfaces of the inner wall 34 and the outer wall 35 smoothly transform into the outer surface of the foot portion 32 . The outer surfaces of the leg portion 31 and the foot portion 32 form a continuous surface. The longitudinal cavity 4 , the leg portion 31 and the foot portion 32 have an oval or elliptical cross section.

[0057] The thickness of the outer wall 35 may be smaller than the thickness of the inner wall 34 to obtain a higher flexibility radially outside the leg portion 31 than radially inside the leg portion 31. This improves the guidance of the foot portion 32 in the radially outward direction when pressure is applied.

[0058] Compared to the embodiment shown in FIG. 2 , the electrode of the embodiment shown in FIG. 3 has a circumferential step 6 between the connector part 2 and the plurality of contact members 3. In the embodiment shown, the contact members form a flat upper wall (perpendicular to the central axis A). When pressure is applied to the connector part 2, the upper wall 37 may bend slightly upward at the circumferential step 6. Embodiments with a dome-shaped upper wall may also have a step between the connector part 2 and the plurality of contact members 3.

[0059] Reference numerals

[0060] 1 electrode

[0061] 11-Electrode / Connector Section Connector Side

[0062] 12 Contact side of electrode

[0063] 2 Connector part

[0064] 3 Contact components

[0065] 31 Flexible leg section

[0066] 32 Rigid foot section

[0067] 33 Free end / lower end

[0068] 34 Curved inner wall

[0069] 35 Curved outer wall

[0070] 36 Dome-shaped upper wall

[0071] 37 Flat upper wall

[0072] 4 Longitudinal cavity

[0073] 5 Inner contact surface

[0074] 6 Circumferential steps

[0075] A The center axis of the electrode

[0076] L Longitudinal axis of the contact member

[0077] α Tilt angle

Claims

1. A soft dry electrode (1) for measuring bioelectric signals of an individual, the electrode (1) being made of an elastomeric material and having conductive properties, and comprising: a central connector part (2) having attachment means for attaching the electrode (1) to a measuring device, and a plurality of flexible contact members (3); The electrode (1) has: a connector side (11) located on one side of the attachment device, and a contact side (12) opposite to the connector side (11) and facing the individual when the electrode (1) is applied to the individual; The connector portion (2) further defines a central axis (A) of the electrode (1), the central axis (A) being arranged to pass centrally through the contact side (12) and the connector side (11) of the electrode (1); wherein the plurality of contact members (3) are arranged around the central axis (A) and connected to the connector part (2), and the plurality of contact members (3) also protrude at a contact side (12) of the connector part (2) to contact an area of ​​interest of an individual for measurement; Features Each of the plurality of contact members (3) comprises a flexible leg portion (31) and a foot portion (32) located at a free end (33) of the flexible leg portion (31); The flexible leg portion (31) has a longitudinal cavity (4) formed by an inner wall (34) bent around the longitudinal axis (L) of the contact member (3), wherein the longitudinal cavity remains open on the connector side (11) and is closed by the foot portion (32) on the contact side (12); And the foot portion (32) and the flexible leg portion (31) form a continuous radial inner contact surface (5).

2. The soft electrode (1) according to claim 1, wherein the radially inner contact surface (5) is inclined, and the inclination angle (α) between the radially inner contact surface (5) and the central axis (A) of the electrode (1) is approximately 10 degrees to 45 degrees and is open on the contact side (12).

3. The soft electrode according to claim 1 or 2, wherein the inclination angle (α) of the contact surface (5) continuously increases from the lower end of the leg portion (31) to the lower end of the foot portion (32), preferably increases to about 35 degrees to 45 degrees.

4. The flexible electrode according to one of the preceding claims, wherein the thickness of the curved inner wall (34) decreases in radially outward direction.

5. The flexible electrode according to one of the preceding claims, wherein the foot portion (32) extends in radially outward direction on an inner wall (34) of the leg portion (31).

6. A soft electrode according to one of the preceding claims, wherein the leg portion (31) further comprises a curved outer wall (35), which together with the curved inner wall (34) forms a longitudinal cavity (4) of the leg portion (31), the longitudinal cavity (4) having an opening towards the connector side (11) of the electrode (1).

7. The flexible electrode according to claim 6, wherein the thickness of the curved outer wall (35) is smaller than the thickness of the curved inner wall (34).

8. The flexible electrode according to one of the preceding claims, wherein the outer surface of the inner wall (34) and / or the outer surface of the outer wall (35) transforms into the outer surface of the foot portion (32) to form a continuous outer surface of the contact member.

9. The flexible electrode according to one of the preceding claims, wherein each leg portion (31) is connected to an adjacent leg portion (31) at an upper end of the leg portion (31).

10. The flexible electrode according to one of the preceding claims, wherein the attachment means is a knob formed by a connector part (2) of the electrode (1) or a rigid connection insert embedded in the connector part (2).

11. The flexible electrode according to one of the preceding claims, wherein the longitudinal cavity (4) has a semi-oval, semi-elliptical, oval or elliptical cross section.

12. The flexible electrode according to one of the preceding claims, wherein the longitudinal cavity (4) is open or closed in radially outward direction.

13. The soft electrode according to one of the preceding claims, wherein the connector part (2) and the plurality of contact members (3) are integrally formed as a single entity of elastomeric material, with or without a rigid insert in the connector part (2).

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