electrode

Abstract

The present invention provides a flexible, dry electrode (1) for measuring a subject's bioelectrical signals. The electrode (1) comprises a central connector portion (2) with attachment means and contact members (3). The electrode (1) has a connector side (11) and a contact side (12), and the connector portion (2) further defines a central axis (A). A plurality of contact members (3) are arranged around the central axis (A) and connected to the connector portion (2). Each contact member (3) comprises a flexible leg portion (31) and a leg end portion (32). The flexible leg portion (31) has a longitudinal cavity (4) formed by a curved inner wall (34). The longitudinal cavity remains open at the connector side (11) and is closed at the contact side (12) by the leg end portion (32). The leg end 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 soft, dry electrodes for detecting bioelectrical signals in applications such as electroencephalography (EEG), electrocardiography (ECG), and electromyography (EMG). [Background technology]

[0002] Commercially available "dry" EEG headsets are often equipped with dry metallic electrodes that can be painful for subjects who wear the headset for a period of time. A possible solution is to combine such electrodes with a spring-like system to avoid high pressure on the skin.

[0003] Another approach is to use soft, polymer-based dry electrodes. Additives can be incorporated into elastic polymers to improve conductivity while maintaining the necessary elasticity for user comfort. Polymer-based dry electrodes can be designed with interdigitated fingers or legs to improve skin contact on hairy skin (e.g., the scalp). These fingers or legs can have at least a partial coating on the outer surface of the electrode that contacts the skin, lowering skin impedance and improving signal quality.

[0004] For this reason, soft and dry electrodes are increasingly being used for long-term biopotential measurements such as EEG and EGG. Not only are such electrodes soft, but the additional fact that they can be applied without the use of conductive gel offers significant advantages to the measurement procedure, such as reducing the risk of skin irritation and avoiding loss of signal quality due to drying of the gel. [Prior art documents] [Patent documents]

[0005] Examples of such soft and dry electrodes include "High user comfort in polymer-based dry electrodes for ECG / EEG measurements" by Chen et al. (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 "Integration Challenges of MEMS, NEMS, ICs and Electronic Components"; 2014; pp. 329-336), and "Soft, Comfortable Polymer Dry Electrodes for High Quality ECG and EEG Recording" by Chen et al. (Sensors, 2014, 14, 23758-23780; doi:10.3390 / s141223758) or WO 2016080804.

[0006] These flexible, dry electrodes consist of a base plate and multiple pins for contacting the target area to be measured. The pins may have tapered and protruding portions. The electrode tips are made of a flexible, flexible matrix material with a conductive material. The electrodes may have a knob on the top of the base plate opposite the pins for electrically connecting the electrode.

[0007] When force is applied to a soft electrode (e.g., a strap, band, headset, or head cap), the legs may move uncontrollably, preventing the brush from performing its intended function of brushing through hair to bring the electrode into direct contact with the skin surface.

[0008] One possible solution to this problem is to pre-orient the legs (as described in EP 2827770), so that when the electrodes are applied to a target area (such as the scalp), the legs are positioned at a non-perpendicular angle to the target area. However, a drawback of this approach is that the manufacturing process employs a 3D printing process that is not suitable for scalability to mass production.

[0009] JP 2019-097733 A relates to an electrode for measuring brain activity. The electrode has a rigid support and multiple arms attached to the sides of the rigid support. The arms have balls at their tips that contact the human scalp. The arms are flexible and bend when force is applied to the electrode. The electrode has a complex shape with multiple undercuts, making it difficult to manufacture at low cost.

[0010] WO 2022 / 047595 describes a soft, dry electrode that includes a flexible support and multiple pins parallel to the support's central axis. When a force is applied to the top surface of the support, the flexible support begins to bend, causing the tips of the pins or legs to move outward (i.e., away from the center of the electrode) and "push aside" hairs that prevent direct contact between the electrode and the subject's bare skin surface. Summary of the Invention [Problem to be solved by the invention]

[0011] It is an object of the present invention to provide a soft, dry electrode for measuring a subject's bioelectrical signals that avoids the problems of the prior art and is suitable for mass production.A further object of the present invention is to improve the shape of the soft, dry electrode to make it easier to push aside body hair in order to optimize contact between the tips of the pins and the subject's scalp / body. [Means for solving the problem]

[0012] At least one of the objects of the present invention is achieved by a soft, dry electrode according to claim 1. The soft, dry electrode for measuring a subject's bioelectrical signals is made of an elastomeric material and is electrically conductive. The electrode comprises a central connector portion including an attachment means for attaching the electrode to a measurement device and a plurality of flexible contact members. The electrode has a connector side adjacent to the attachment means and a contact side opposite the connector side, facing the subject when the electrode is attached to the subject. The connector portion further defines a central axis of the electrode that passes through the center between the contact side and the connector side of the electrode. A plurality of the contact members are arranged around the central axis and connected to the connector portion. The plurality of contact members further protrude toward the contact side to contact a contact target area of ​​the subject for measurement. Each of the contact members comprises (or may consist of) a flexible leg and a leg end provided at the free end of the flexible leg. The flexible legs have longitudinal cavities formed by inner walls that are curved around the longitudinal axis of the contact members, the longitudinal cavities remaining open on the connector side and closed on the contact side by leg ends, the leg ends and the flexible legs forming a continuous radially inner contact surface. [Effects of the Invention]

[0013] This allows the electrode to have a structure in which the inner walls of the flexible legs transition smoothly to the end of the legs. Manufacturing the electrode does not require complex tooling to accommodate undercuts. At the same time, the "hollow" structure, i.e., longitudinal cavity, of the curved walls that weaken the legs maintains high flexibility of the legs. This allows the contact members to bend when the contact surface of the electrode is placed on a subject and force is applied to the connector side. The weakened radially outer legs allow the leg ends to move radially outward along the subject's skin and part hair as they bend. This continuous radially inner contact surface does not have edges, steps, or abrupt changes in curvature, allowing the contact members to move smoothly along the subject's skin as the actual contact area moves across the contact surface, even when force is applied to the connector side of the electrode. Additionally, the outward movement of the leg ends when pressure is applied to the connector side may be further enhanced by an inclination angle between at least a portion of the radially inner contact surface of the contact member and the central axis of the electrode, which causes the contact members to open towards their tip portions and thus move radially outward upon contacting the measurement area of ​​the subject.

[0014] The leg ends may be stiffer (or less flexible) than the flexible legs, but still remain resilient due to the elastomeric material of the electrode. This is achieved by having the leg ends be a solid design with no cavities or "hollow" structures. The bending of the contact members occurs along the legs.

[0015] In the present invention, "upper" refers to the connector side, and "lower" refers to the contact side of the electrode. "Radial" is used relative to the central axis of the electrode. The long axis of the contact member passes through approximately the center of the leg end and extends longitudinally along the leg, in other words, the long axis along the longitudinal cavity. The inclination angle of the contact surface can be determined along the radially innermost line of the inner wall in a bent state. The contact surface is the surface of the inner wall facing radially inward, which can contact the subject when the contact element is bent by a force applied to the connector side.

[0016] Further embodiments of the invention are described in the dependent claims. In some embodiments, the electrodes may be made of an elastomeric material provided with a conductive additive and / or may be at least partially coated with a conductive coating.

[0017] In some embodiments, the radially inner contact surface is inclined, the angle of inclination between the radially inner contact surface and the central axis of the electrode being about 10 to 45 degrees, and opening toward the contact side.

[0018] In some embodiments, good results are obtained when the angle of inclination between the radially inner contact surface and the central axis of the electrode is about 15-25°, preferably about 17.5-20°.

[0019] In some embodiments, the angle of inclination of the contact surface from the lower end of the leg to the lower end of the leg tip increases continuously, preferably by about 35-45°, more preferably by about 20-35°. The continuously increasing angle of inclination toward the tip of the contact element allows the leg tip to slide easily along the subject's skin when force is applied and the leg begins to bend. This allows the actual contact area of ​​the contact element to move from the tip of the leg tip toward the inside of the leg tip and the lower-inner side of the leg, depending on the degree of bending of the contact element.

[0020] In some embodiments, the inclination angle of the contact surface of only the leg end is large, and at least the upper part of the contact member is approximately parallel to the central axis, i.e., the inclination angle is approximately 0° or close to 0°.

[0021] In some embodiments, the thickness of the inner wall in the bent state may decrease radially outward, which allows the radially outer portion of the inner wall to deform more easily when a force is applied to the connector side, improving the bending behavior of the legs.

[0022] In some embodiments, the leg ends may extend radially outward beyond the inner wall of the leg.

[0023] In some embodiments, the leg may further comprise a bent outer wall that, together with the bent inner wall, defines a longitudinal cavity of the leg, the longitudinal cavity being open toward the connector side of the electrode, whereby the longitudinal cavity of the leg is defined by a peripheral wall. The thickness of the bent outer wall may be less than the thickness of the bent inner wall.

[0024] In some embodiments, the outer surface of the inner wall and / or the outer surface of the outer wall merges into the outer surface of the leg end to form a continuous outer surface of the contact element. In other words, the entire contact element, i.e. the leg and the leg end, forms a smooth outer surface. In the context of the present invention, the outer surface is the surface of each part facing away from the longitudinal axis, thereby forming the convex side of the inner or outer wall of the leg.

[0025] In some embodiments, each leg may be connected to an adjacent leg at its upper end, which improves the stability of the electrode at the connector side.

[0026] In some embodiments, the contact members taper towards the leg ends, continuously decreasing in cross-sectional size.

[0027] In some embodiments, the upper surface of the contact member may form a dome-shaped upper surface with the connector portion.

[0028] In some embodiments, a circumferential step may be formed between the connector portion and the plurality of contact members, which improves the bending behavior of the electrode and reduces the required force.

[0029] 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.

[0030] In some embodiments, the attachment means may be a knob formed by the connector portion of the electrode, or a rigid connection insert recessed into the connector portion of the electrode.

[0031] In some embodiments, the longitudinal cavity has a semi-oval, semi-elliptical, oval, or elliptical cross section.

[0032] In some embodiments, the longitudinal cavity may be radially outwardly open or closed.

[0033] In some embodiments, the electrode may comprise between 6 and 12 of the contact members, preferably 8 contact members, spaced about the central axis.

[0034] In some embodiments, the plurality of contact members may be regularly arranged around the central axis of the electrode.

[0035] In some embodiments, the connector portion and the plurality of contact members of the electrodes may be integrally formed as a single piece of elastomeric material, with or without a rigid insert in the connector portion.

[0036] In some embodiments, the electrode may have a diameter (around the central axis A) of 8 to 25 mm and a length (along the central axis) of 6 to 25 mm.

[0037] In some embodiments, the contact members may have a length of between 4 and 20 mm and an average radial and / or tangential cross-sectional dimension of between 1.5 and 3.5 mm. [Brief explanation of the drawings]

[0038] The invention will now be explained in more detail with reference to embodiments shown in the drawings, in which: [Figure 1] 1A and 1B are diagrams showing a first embodiment of a soft electrode, in which (a) is a perspective view of the connector side, (b) is a perspective view of the contact side, (c) is a top view of the connector side, (d) is a side view, (e) is a cross-sectional view taken along C1-C1 shown in (c), and (f) is a cross-sectional view taken along C2-C2 shown in (c). [Figure 2] 10A and 10B are diagrams showing a second embodiment of a soft electrode, in which (a) is a perspective view of the connector side, (b) is a perspective view of the contact side, (c) is a top view of the connector side, (d) is a side view, (e) is a cross-sectional view along C1-C1 shown in (c), and (f) is a cross-sectional view along C2-C2 shown in (c). [Figure 3] 10A and 10B are diagrams showing a third embodiment of a soft electrode, in which (a) is a perspective view of the connector side, (b) is a perspective view of the contact side, (c) is a top view of the connector side, (d) is a side view, (e) is a cross-sectional view along C1-C1 shown in (c), and (f) is a cross-sectional view along C2-C2 shown in (c). DETAILED DESCRIPTION OF THE INVENTION

[0039] 1, 2, and 3 show three embodiments of a flexible electrode 1 for measuring a subject's bioelectrical signals. The electrode 1 is made of an elastomeric material to provide a soft, flexible electrode with electrical conductivity that allows for measurement of even small electrical signals on the subject's skin. The electrode 1 comprises a central connector portion 2 and a plurality of flexible contact members 3. The central connector portion 2 is provided with an attachment means (not shown), such as an integral knob or a recessed insert with a knob, by which the electrode can be attached to a measurement device (e.g., a headset). Such attachment means are known in the art.

[0040] In the illustrated embodiment, the electrode has eight contact members regularly spaced about a central axis.

[0041] The electrode 1 further has a connector side 11 on the attachment means side and a contact side 12 located opposite the connector side 11, which contact side faces the subject when the electrode 1 is properly worn, i.e., when the connector side 11 faces away from the subject. The electrode is therefore positioned with the contact side facing the subject. The device or headset applies a force to the connector side 11 of the electrode 1, pressing the electrode 1 so that the contact side 12 is pressed against the subject.

[0042] The central connector portion 2 defines the 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 portion 2. The contact members 3 protrude from the contact side 12 of the connector portion 2 and come into contact with the subject's contact target area when the electrode 1 is correctly attached. The connector side 11, which is provided with the attachment means, faces away from the subject's contact area.

[0043] Each of the plurality of contact members 3 includes a flexible leg 31 and a stiffer leg end 32 at a free end 33 of the flexible leg 31. The leg end 32 is stiffer than the flexible leg 31 but remains elastic due to the elastomeric material of the electrode 1. The flexible leg has a longitudinal cavity 4, which allows the flexible leg 31 to bend more easily when pressure is applied to the connector side 11 of the electrode 1. A longitudinal axis L is defined by the protruding contact member 3 and the longitudinal cavity 4 of the leg 31. The longitudinal cavity 4 is formed by at least one curved inner wall 34 that is curved around the longitudinal axis L of the contact member 3.

[0044] The outer surface of the inner wall 34, i.e., the surface facing the central axis A, forms a continuous surface with the outer surface of the leg end 32. In other words, the outer surface of the leg 31 transitions smoothly into the outer surface of the leg end 32. The innermost outer surface along the contact member forms a continuous radially inner contact surface 5. Depending on how much the contact member 3 bends when pressure is applied to the connector side 11, different areas of said contact surface 5 may come into contact with the subject.

[0045] 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 15-25°. In the embodiment shown in FIGS. 1-3, the inclination angle α is approximately 18°. Because the inclination angle α is open toward the contact side 12, when pressure is applied to the connector side 11 and the electrode is pressed against the subject at the contact side 12, the leg ends 32 slide radially outward. This allows the stiffer leg ends 32 to slide along the subject's skin / scalp and through hair (if present). At the same time, the actual contact area on the contact member 3 increases and / or moves upward along the contact member 3, i.e., toward the connector side 11.

[0046] To obtain stability in the region of the connector part 2, the upper ends of the inner walls 34 of the legs 31 may be connected to the upper ends of the inner walls 34 of the adjacent legs 31.

[0047] The longitudinal cavity 4 is open at the connector side 11 but closed at the contact side 12 by the leg ends 32. The contact members 3 are tapered towards the leg ends 32, with a continuously decreasing cross-sectional size. The electrode design does not have undercuts, allowing for manufacture with a relatively simple mold using only two mold halves.

[0048] 1-3, the angle of inclination at the upper ends of the legs 31 is constant up to approximately the middle of the legs 31. Thereafter, the angle increases continuously towards the lower ends of the leg ends 32, reaching approximately 45°. When a force is applied to the connector side 11 and the legs 31 begin to bend outward, the leg ends 32 are efficiently guided radially outward.

[0049] The thickness of the curved inner wall 34 may decrease towards the outside of the electrode, such that the curved inner wall 34 is less flexible on the inside than on the outside, further facilitating the outward guiding movement of the leg ends 32.

[0050] In the embodiment of Figure 1, the longitudinal cavity 4 of the contact member 3 is open radially outward. The leg 31 is formed only by the inner wall 34. The leg end 32 extends radially outward beyond the inner wall 34 of the leg 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 leg end 32 has an oval or elliptical cross section.

[0051] In the embodiment of Figures 1 and 2, a plurality of contact members 3 may form a dome-shaped upper wall.

[0052] In the embodiment of Figures 2 and 3, in comparison with the embodiment of Figure 1, the longitudinal cavity 4 of the contact element 3 is closed radially outward by a curved outer wall 35 that is curved about the longitudinal axis L. The curved inner wall 34 and the curved outer wall 35 together form the longitudinal cavity 4 of the leg 31 that opens towards the connector side 11. The contact side 12 of the longitudinal cavity 4 is closed by the leg end 32. The outer surfaces of the inner wall 34 and the outer wall 35 smoothly merge into the outer surfaces of the leg end 32. The outer surfaces of the leg 31 and the leg end 32 form a continuous surface. The longitudinal cavity 4, the leg 31 and the leg end 32 have an oval or elliptical cross section.

[0053] The thickness of the outer wall 35 may be less than the thickness of the inner wall 34, which makes the radially outwardly flexible legs 31 more flexible than the radially inwardly flexible legs 31, improving the radially outward guidance of the leg ends 32 when pressure is applied.

[0054] In comparison to the embodiment of FIG. 2, the electrode of the embodiment of FIG. 3 has a circumferential step 6 between the connector portion 2 and the plurality of contact members 3. In the illustrated embodiment, the contact members form a flat top wall (perpendicular to the central axis A). The circumferential step 6 may cause the top wall 37 to flex slightly upward when pressure is applied to the connector portion 2. In embodiments having a dome-shaped top wall, a step may also be provided between the connector portion 2 and the plurality of contact members 3. [Explanation of symbols]

[0055] 1 electrode 11 Electrode connector side / connector part 12 Electrode contact side 2 Connector part 3 Contact members 31 Flexible legs 32 Highly rigid leg end 33 Free end / lower end 34 Curved inner wall 35 Curved exterior wall 36 Dome-shaped upper wall 37 Flat top wall 4 Longitudinal Cavity 5 Inner contact surface 6 Circumferential step A Central axis of the electrode L Long axis of contacting member α Incline angle

Claims

1. A soft and dry electrode (1) for measuring a subject's bioelectrical signals, The electrode (1) is made of an elastomeric material and having electrical conductivity; a central connector portion (2) having attachment means for attaching the electrodes (1) to a measuring device and a plurality of flexible contact members (3); The electrode (1) is a connector side (11) on the side of the attachment means, and a contact side (12) located on the opposite side of the connector side (11) and facing the subject when the electrode (1) is attached to the subject; The connector portion (2) further defines a central axis (A) of the electrode (1) that is arranged to pass through the center between the contact side (12) and the connector side (11) of the electrode (1); The plurality of contact members (3) are arranged around the central axis (A) and connected to the connector portion (2); The plurality of contact members (3) further protrude from the contact side (12) of the connector portion (2) to contact a contact target area for measurement of the subject; Each of the contact members (3) comprises a flexible leg (31) and a leg end (32) provided at a free end (33) of the flexible leg (31); The flexible leg (31) has a longitudinal cavity (4) formed by an inner wall (34) in a curved state around the longitudinal axis (L) of the contact member (3), the longitudinal cavity remains open on the connector side (11) and is closed by the leg ends (32) on the contact side (12), The leg end (32) and the flexible leg (31) form a continuous radially inner contact surface (5).

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

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

4. 4. A flexible electrode according to claim 1, wherein the thickness of the inner wall (34) in the bent state decreases radially outward.

5. The soft electrode according to any one of claims 1 to 4, The leg ends (32) extend radially outward beyond the inner wall (34) of the leg portion (31).

6. The soft electrode according to any one of claims 1 to 5, The leg (31) further comprises a curved outer wall (35) which, together with the curved inner wall (34), defines the longitudinal cavity (4) of the leg (31) opening towards the connector side (11) of the electrode (1).

7. 7. A flexible electrode according to claim 6, wherein the thickness of the outer wall (35) in the bent state is less than the thickness of the inner wall (34) in the bent state.

8. The soft electrode according to any one of claims 1 to 7, An electrode wherein the outer surface of said inner wall (34) and / or the outer surface of said outer wall (35) merges into the outer surface of said leg ends (32) to form a continuous outer surface of the contact element.

9. The soft electrode according to any one of claims 1 to 8, An electrode in which each of the legs (31) is connected to an adjacent leg (31) at the upper end of the leg (31).

10. The soft electrode according to any one of claims 1 to 9, The attachment means is a knob formed by the connector part (2) of the electrode (1) or a rigid connecting insert embedded in the connector part (2) of the electrode (1).

11. The soft electrode according to any one of claims 1 to 10, Electrode, wherein said longitudinal cavity (4) has a semi-oval, semi-elliptical, oval or elliptical cross section.

12. The soft electrode according to any one of claims 1 to 11, Electrode, wherein said longitudinal cavity (4) is open or closed radially outward.

13. The soft electrode according to any one of claims 1 to 12, An electrode wherein the connector portion (2) and the plurality of contact members (3) are integrally formed as a single piece of elastomeric material, with or without a rigid insert in the connector portion (2).

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