Biometric-signal sensing electrode

Abstract

A biometric-signal sensing electrode according to the present invention comprises: a base material having a two-dimensional surface; and an electroconductive material formed on the two-dimensional surface of the base material and containing particles of a layered material including one or more layers, the electroconductive material including, on the opposite side from the base material side, a contact surface that contacts a subject. The layer includes a layer body represented by Ti3C2, and a modification or a terminal T (T being at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body. The electroconductive material is formed on a region other than an end portion of the two-dimensional surface of the base material.

Description

Biosignal Sensing Electrodes

[0001] The present disclosure relates to a biosignal sensing electrode.

[0002] One method for detecting biometric information, such as electrical signals from the muscles or heart of a subject (patient), without causing pain to the human body is to measure by contacting a sheet-like electrode with the subject. Recently, dry electrodes have been proposed as such electrodes, which do not require gel or adhesive and are highly unlikely to cause an allergic reaction on the patient's skin. For example, Patent Literature 1 (JP-A-2005-102626) discloses a measurement device that includes multiple button-type electrodes embedded in or attached to a wearable device worn around the torso of a pregnant subject, enabling noninvasive acquisition of electrocardiogram signals and the extraction of separate electrocardiogram signals for the fetus and the mother.

[0003] U.S. Patent No. 9,579,055

[0004] The dry electrode of Patent Document 1 has protrusions to improve contact between the electrode and the skin, but these protrusions cause strong discomfort to the patient. Furthermore, dry electrodes are required to exhibit high conductivity and have sufficiently high sensitivity in a dry state. The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a biosignal sensing electrode that exhibits high conductivity and can detect bioinformation with high sensitivity without causing discomfort to the subject.

[0005] Furthermore, wet electrodes typically contain moisture in the gel, but when measuring an electrocardiogram continuously for a certain period of time, for example, for 10 days, the gel dries out, reducing measurement accuracy, and the wet electrode must be replaced, for example, at least once every three days. Therefore, another object of the present disclosure is to provide a highly reliable biosignal sensing electrode that can withstand continuous measurement.

[0006] According to one aspect of the present disclosure, there is provided a biosignal sensing electrode comprising: a substrate having a two-dimensional surface; and a conductive material including particles of a layered material including one or more layers formed on the two-dimensional surface of the substrate, the conductive material having a contact surface on the side opposite to the substrate side that contacts a subject, the layer being made of Ti.３ C ２ and a modified or terminated T (where T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, wherein the conductive material is formed on a region other than the end portion of the two-dimensional surface of the substrate.

[0007] According to the present disclosure, there is provided a biosignal sensing electrode that includes a conductive material containing particles of a predetermined layered material (also referred to herein as "MXene") on at least a region other than the edge of the two-dimensional surface of a substrate, the region being in contact with a subject. This provides a biosignal sensing electrode that exhibits high conductivity, is capable of sensitively detecting bioinformation, and is highly reliable, without causing discomfort to the subject.

[0008] FIG. 1 is a schematic cross-sectional view showing a conductive material in a preferred embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view showing MXene, a layered material that can be used for the conductive material in an embodiment of the present disclosure. FIG. 3 is a schematic perspective view showing a biosignal sensing electrode in an embodiment of the present disclosure. FIG. 4 is a schematic cross-sectional view showing a conventional biosignal sensing electrode. FIG. 5 is a schematic cross-sectional view showing a biosignal sensing electrode in another embodiment of the present disclosure. FIG. 6 is a schematic cross-sectional view showing another conventional biosignal sensing electrode. FIG. 7 is a schematic cross-sectional view showing a biosignal sensing electrode in an embodiment of the present disclosure. FIG. 8 is a schematic cross-sectional view showing a biosignal sensing electrode in another embodiment of the present disclosure. FIG. 9 is a schematic cross-sectional view showing an example of use of the biosignal sensing electrode in an embodiment of the present disclosure.

[0009] Hereinafter, a biosignal sensing electrode and a conductive material used in the electrode according to an embodiment of the present disclosure will be described in detail, but the present disclosure is not limited to such an embodiment.

[0010] (Conductive Material) The conductive material used in the biosignal sensing electrode of this embodiment contains particles of a predetermined layered material.

[0011] A particle of a given layered material in this embodiment is defined as follows: A particle of a layered material comprising one or more layers, the layers being Ti ３ C ２ and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body (more specifically, on at least one of two opposing surfaces of the layer body). ３ C ２ T ｘ ", where x is an arbitrary number, and conventionally, s or z is sometimes used instead of x). Hereinafter, this layered material will be referred to as "Ti ３ C ２ T ｘ " or MXene (particle).

[0012] Such MXene can be synthesized by selectively etching (removing and optionally separating) A atoms (such as Al, Si, Sn, and In) from the MAX phase (and optionally some Ti atoms). ３ AC ２ and Ti ３ C ２ The MAX phase has a crystal structure in which a layer composed of A atoms is located between two layers represented by the formula (which may have a crystal lattice in which each C is located in the octahedral array of Ti). ３ AC ２ As shown above, when the number of Ti atoms = the number of carbon atoms + 1, one layer of carbon atoms is placed between each of the three Ti atom layers (together, these are called "Ti ３ C ２ The MAX phase has a repeating unit in which a layer of A atoms (also referred to as a "layer") is arranged as the next layer after the third layer of Ti atoms ("A atom layer"). The A atoms (and possibly some of the Ti atoms) are selectively etched (removed and possibly layer separated) from the MAX phase, thereby removing the A atom layer (and possibly some of the Ti atoms) and exposing the Ti atoms. ３C ２ The surface of the layer is modified with hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms, hydrogen atoms, etc. present in the etching solution (usually, an aqueous solution of fluorine-containing acid is used, but this is not limited to this) to terminate the surface.

[0013] The etching is performed using a fluorine-based resin container with an acid such as HF, HCl, HBr, HI, sulfuric acid, phosphoric acid, or nitric acid. For example, a method using a mixture of lithium fluoride and hydrochloric acid, or a method using hydrofluoric acid, may be used. The etching process involves stirring at a temperature above room temperature and below 40°C for approximately 5 to 48 hours. The subsequent cleaning step involves transferring the liquid after the etching process to, for example, a centrifuge tube, adding pure water, stirring, separating the supernatant and precipitate using a centrifuge, and discarding the supernatant, repeating this process 5 to 20 times. Thereafter, a delamination process is performed for a predetermined time using, for example, a mechanical shaker, a vortex mixer, a homogenizer, an ultrasonic bath, or the like. The supernatant and precipitate are then separated using a centrifuge, and the collected supernatant is used to remove the monolayered Ti. ３ AC ２ (MXene) can be used as a dispersion.

[0014] In the present disclosure, MXene may contain a relatively small amount of residual A atoms, for example, 10% by mass or less of the original A atoms. The amount of residual A atoms may be preferably 8% by mass or less, and more preferably 6% by mass or less. However, even if the amount of residual A atoms exceeds 10% by mass, this may not be a problem depending on the application and use conditions of the paste (and the conductive film obtained therefrom).

[0015] As shown schematically in Figure 2, the MXene (particle) 10 synthesized in this manner can be a layered material containing one or more MXene layers 7a, 7b (examples of the MXene (particle) 10 include, but are not limited to, a single layer of MXene 10a in Figure 2(a) and a two layer MXene 10b in Figure 2(b)). More specifically, the MXene layers 7a, 7b can be Ti, ３ C ２ The layer body (Ti３ C ２ The MXene layers 7a and 7b have Ti modifications or terminations 3a, 5a, 3b, and 5b present on the surfaces of the layer bodies 1a and 1b (more specifically, on at least one of the two surfaces facing each other in each layer). ３ C ２ T ｘ ", where x is an arbitrary number. MXene 10 may be a single layer in which the MXene layers are individually separated (single-layer structure shown in FIG. 2(a), known as single-layer MXene 10a), a laminate in which multiple MXene layers are stacked and spaced apart (multilayer structure shown in FIG. 2(b), known as multilayer MXene 10b), or a mixture thereof. MXene 10 may be in the form of aggregate particles (which may also be referred to as powder or flakes) composed of single-layer MXene 10a and / or multilayer MXene 10b. In this embodiment, MXene 10 is preferably a particle (which may also be referred to as nanosheet) composed mostly of single-layer MXene 10a. In the case of multilayer MXene, two adjacent MXene layers (e.g., 7a and 7b) do not necessarily have to be completely separated and may be partially in contact.

[0016] Although not limiting this embodiment, the thickness of each MXene layer (corresponding to the above-mentioned MXene layers 7a and 7b) is, for example, 0.8 nm to 5 nm, in particular 0.8 nm to 3 nm (this may vary mainly depending on the number of Ti atomic layers contained in each layer), and the maximum dimension in a plane parallel to the layer (two-dimensional sheet surface) is, for example, 0.1 μm to 200 μm, in particular 1 μm to 40 μm. When MXene is a laminate (multilayer MXene), the interlayer distance (or gap dimension, shown as Δd in Figure 2(b)) for each laminate is, for example, 0.8 nm to 10 nm, particularly 0.8 nm to 5 nm, and more particularly about 1 nm; the total number of layers may be 2 or more, but is, for example, 50 to 100,000, particularly 1,000 to 20,000; the thickness in the stacking direction is, for example, 0.1 μm to 200 μm, particularly 1 μm to 40 μm; and the maximum dimension in a plane perpendicular to the stacking direction (two-dimensional sheet surface) is, for example, 0.1 μm to 100 μm, particularly 1 μm to 20 μm. These dimensions are determined as number-average dimensions (e.g., number-average of at least 40 particles) based on a scanning electron microscope (SEM), transmission electron microscope (TEM) photograph, or atomic force microscope (AFM) photograph, or as distances in real space calculated from the position in reciprocal lattice space of the (002) plane measured by X-ray diffraction (XRD).

[0017] 1 shows a conductive material used in a preferred embodiment of the biosignal sensing electrode. In FIG. 1, the conductive material 20 used in the biosignal sensing electrode includes particles 10 of a predetermined layered material and a polymer 11. The polymer 11 is preferably a hydrophilic polymer having a polar group, and the polar group is preferably a group that forms a hydrogen bond with the modification or terminal T of the layer.

[0018] As in this embodiment, a highly reliable biosignal sensing electrode is provided by providing a composite material containing MXene and, preferably, a polymer, on a two-dimensional surface, such as a flat surface, of a substrate, excluding the edges. The layered material contained in the composite material has the physical characteristic of spontaneously stacking parallel to the substrate. In areas with unevenness or protrusions, such as the edges of the substrate, the alignment of the layered material tends to become disordered, causing gaps between the layers to widen. These widened gaps allow perspiration on the skin and moisture in the environment to penetrate, reducing the reliability of the biosignal sensing electrode. Therefore, a conductive material, preferably the composite material, is provided in the area of ​​the two-dimensional surface, such as a flat surface, excluding the edges. This maintains a dense membrane structure, thereby preventing the penetration of perspiration on the skin and moisture in the environment, resulting in a highly reliable biosignal sensing electrode.

[0019] In this embodiment, the polymer that can be mixed with the particles of the layered material is preferably a hydrophilic polymer having a polar group, and the polar group is preferably a group that forms a hydrogen bond with the modification or terminal T of the layer.

[0020] The polymer is preferably one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, sodium alginate, water-soluble acrylic acid polymer, polyacrylamide, polyaniline sulfonic acid, and nylon. ３ -, -CONH-, -COO-, -OH, -NH- are abundant, so Ti ３ C ２ T ｘ The resulting conductive material has high affinity with the metal, for example, it is easy to form hydrogen bonds, and therefore the resulting conductive material has reduced disorder and can have high conductivity. As a result, a highly sensitive dry electrode can be provided.

[0021] Among these, one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, and sodium alginate are more preferred. These polymers have functional groups capable of forming hydrogen bonds, particularly Ti. ３ C ２T ｘ Since it has many functional groups that contribute to hydrogen bonding with Ti, ３ C ２ T ｘ It is believed that this facilitates the formation of hydrogen bonds with water, providing highly sensitive electrodes. In particular, water-soluble polyurethane contains a large amount of urethane bonds, which have both hydrogen bond donor and hydrogen bond acceptor properties. The polyvinyl alcohol contains a large amount of OH groups, which exhibit hydrogen bond donor properties. In addition, sodium alginate has a high molecular planarity, and MXene, especially Ti, ３ C ２ T ｘ The number of functional groups that can hydrogen bond with the hydroxyl group is substantially larger.

[0022] The polymer is preferably a polymer having an amide bond or a urethane bond, which has both hydrogen bond donor and hydrogen bond acceptor properties, and from this viewpoint, the water-soluble polyurethane is particularly preferred. ３ C ２ T ｘ There are many parts that contribute to hydrogen bonding with Ti. ３ C ２ T ｘ When the modified or terminal T in the formula (I) has at least one hydrogen acceptor selected from the group consisting of a fluorine atom, a chlorine atom, and an oxygen atom, the H of the NH of the amide bond or the urethane bond can act as a hydrogen donor to form a hydrogen bond. ３ C ２ T ｘ When the modified or terminal T in has a hydroxyl group and / or a hydrogen atom as a hydrogen donor, the O of the CO of the amide bond or urethane bond can act as a hydrogen acceptor to form a hydrogen bond.

[0023] The ratio of the particles of the layered material to the conductive material, i.e., the ratio of Ti to the conductive material ３ C ２ T ｘThe ratio of the particles of the layered material is preferably 52% by mass or more and 83% by mass or less. By setting the ratio of the particles of the layered material to 52% by mass or more, biological signals can be detected with high sensitivity. The ratio of the particles of the layered material is more preferably 61% by mass or more. From the viewpoint of ensuring higher flexibility of the composite material, the ratio is preferably 83% by mass or less, more preferably 75% by mass or less. As described above, the ratio of the particles of the layered material refers to the ratio in the conductive material. The conductive material of the present disclosure may contain additives such as colorants and antioxidants. In this case, the ratio of the particles of the layered material refers to the ratio in the conductive material including the additives.

[0024] In another preferred embodiment, the conductive material has a higher concentration of layered material particles, and the proportion of layered material particles is greater than 83% by mass and less than 94% by mass. By using a conductive material with this increased concentration, even if the surface of the subject is difficult to detect biosignals due to, for example, hard keratin, measurement can be performed without pretreatment such as removing the keratin. From the perspective of detecting biosignals with higher sensitivity, the proportion of layered material particles is more preferably 85% by mass or more, and even more preferably 89% by mass or more. Even in this case, from the perspective of ensuring the flexibility of the composite material, the proportion of layered material particles is preferably 94% by mass or less, and more preferably 92% by mass or less.

[0025] One electrode may be provided with two or more conductive materials having different particle ratios of the layered material.

[0026] The conductive material in the biosignal sensing electrode of this embodiment is not limited to a specific form, as long as it is formed in a region other than the edge of the two-dimensional surface of the substrate and has at least a contact surface with the subject, as described above. The conductive material may be in a solid state or a flexible, soft state. When the conductive material is in a sheet form, its thickness can be measured, for example, by measuring with a micrometer or by observing the cross section using a scanning electron microscope (SEM), a microscope, or a laser microscope.

[0027] The conductive material of this embodiment preferably maintains a conductivity of 500 S / cm or more when it is, for example, a sheet-like conductive film with a thickness of 5 μm. The conductivity can be maintained at preferably 1000 S / cm or more, more preferably 1800 S / cm or more, even more preferably 2400 S / cm or more, and even more preferably 2900 S / cm or more. There is no particular upper limit to the conductivity of the conductive film, but it can be, for example, 10,000 S / cm or less. The conductivity can be determined as follows: The surface resistivity is measured using a four-probe method, and the value obtained by multiplying the thickness [cm] and the surface resistivity [Ω / □] is the volume resistivity [Ω.cm], and the conductivity [S / cm] can be calculated as the reciprocal of this value.

[0028] (Biological signal sensing electrode) In the biological signal sensing electrode of this embodiment, the conductive material is formed in an area other than the end portion on the two-dimensional surface of the substrate as described above, and is provided at least on the surface that comes into contact with the subject, and the specific form is not limited. As described above, the conductive material may be in a solid state or a flexible soft state.

[0029] FIG. 3 shows a schematic perspective view of a snap-type electrode as one embodiment of a biosignal sensing electrode. FIG. 3 shows a lead wire 32A connected to a snap portion 31A of an electrode 30A, which has a convex curved contact surface with the subject. Cross-sectional views of a conventional electrode are shown in FIGS. 4( a), 4( b), and 4( c) as cross-sectional views of the electrode 30A in FIG. 3 . FIG. 5 also shows a schematic perspective view of another snap-type electrode. FIG. 5 shows a lead wire 32B connected to a snap portion 31B of an electrode 30B, which has a flat contact surface with the subject. Cross-sectional views of the conventional electrode are shown in FIGS. 6( a), 6( b), and 6( c) as cross-sectional views of the electrode 30B in FIG. 5 , and cross-sectional views of the electrode of this embodiment are shown in FIGS. 7 and 8. The embodiments in FIGS. 3 and 5 above include the conductive material and do not have protrusions like the electrode of Patent Document 1. The difference between the embodiments shown in FIGS. 3 and 5 is whether the contact surface with the subject is curved or flat.

[0030] The following description of the electrode of this embodiment will be given for a case in which the contact surface with the subject is flat. However, the electrode of this embodiment may also have a convex curved contact surface with the subject, as shown in FIGS. 3 and 4 . The electrode of this embodiment may have a convex curved two-dimensional surface of the substrate and a convex curved contact surface with the subject. A curved contact surface with the subject is believed to reduce discomfort when worn. Below, FIGS. 4(c) and 6(c) are compared with FIGS. 7 and 8 . Although not shown in FIGS. 7 and 8 , the electrode of this embodiment may have conductive materials 21A and 21B formed on substrates 23A and 23B, respectively, as shown in FIGS. 4(a) and 6(a), which are cross-sectional views of conventional electrodes. Increasing the proportion of conductive material in this manner can provide a highly sensitive biosignal sensing electrode.

[0031] 4(c) and 6(c) showing the conventional electrode embodiment, Ti is attached to the surface of the conventional snap-type electrodes 24A and 24B made of a conductive material. ３ C ２ T ｘ The conductive materials 22A and 22B are provided with a high concentration of Ti, and the contact surface 19 with the test object is provided with Ti, ３ C ２ T ｘ 1 and 2 indicate electrodes each provided with a high concentration of conductive material 22A, 22B. Note that the conductive material used in, for example, a substrate is referred to as a "conductive material" to distinguish it from the "conductive material" containing particles of a specific layered material in the biosignal sensing electrode of the present disclosure. Furthermore, in Figures 4, 6, and Figures 7 and 8 described below, the contact surface 19 with the subject refers to the surface that contacts the subject, and does not include the side surface of the conductive material in Figures 4, 6, 7, and 8. The conductive material constituting the snap-type electrodes 24A, 24B can be the same as that of the substrates 23A, 23B formed from the conductive material shown in Figures 4(a) and 6(a). This configuration allows for the use of a versatile extraction electrode, making it possible to provide a low-cost, highly sensitive bioelectrode sensing electrode.

[0032] Unlike conventional electrodes, the electrode of this embodiment has a conductive material formed on a region other than the edge of the two-dimensional surface of the substrate. For example, as illustrated in FIG. 7( a), the conductive material 21C is formed only inside the edge 28 of the substrate 23C on the plane (two-dimensional surface) of the substrate 23C. The conductive material is preferably formed 100 μm or more inside from the edge of the two-dimensional surface of the substrate (preferably all edges of the two-dimensional surface of the substrate). The conductive material may be formed even 500 μm or more inside, or even 1 mm or more inside, from the edge of the two-dimensional surface of the substrate. In FIG. 7( b), a recess is present near the center of the substrate 25A, and the conductive material 21C is formed inside the edge 28 (also referred to as the "peripheral edge of the two-dimensional surface") of the plane (two-dimensional surface) 27 of the substrate 25A, but outside the edge (circumferential edge) 29 of the recess (referring to the outside as viewed from the recess; the same applies below). When a recess is present near the center of the substrate, the conductive material is preferably formed at least 100 μm outside the edge of the recess in the two-dimensional surface of the substrate (preferably all edges of the recess in the two-dimensional surface of the substrate). The conductive material may be formed at least 500 μm, or even at least 1 mm outside the edge of the recess in the two-dimensional surface of the substrate. By forming the conductive material only in the area excluding the edge in the plane (two-dimensional surface) of the substrate in this way, the long-term reliability of, for example, an electrocardiogram electrode can be improved.

[0033] For example, as mentioned above, the gel applied to wet electrodes used in Holter electrocardiograms dries over time. Therefore, to ensure measurement accuracy, they need to be replaced approximately every three days. Electrocardiogram measurements using Holter electrocardiograms are performed for, for example, 10 consecutive days, necessitating wet electrode replacement. As a result, problems such as the laborious replacement process and the environmental impact of waste arise. Therefore, to reduce the frequency of replacement, snap-type electrodes, for example, that do not require gel, are used. In conventional snap-type electrodes, a conductive material is applied to the electrode substrate so that the entire contact surface with the subject is made of the conductive material. The conductive material may include the layered material and have a densely layered structure. However, the edge of the electrode substrate has a small radius of curvature, and if the layered material is positioned even on the edge of the electrode substrate, as in conventional snap-type electrodes, the dense state of the layered material formed on the edge of the electrode substrate is easily lost. As a result, sweat on the skin or moisture in the environment may penetrate between the layers of the layered material, potentially causing the layered material to redisperse into the sweat on the skin or moisture in the environment. If the conductive material is redispersed, it becomes difficult to ensure long-term measurement reliability, for example, when measuring electrocardiograms for 10 consecutive days using a Holter electrocardiogram. However, as in this embodiment, by forming the conductive material at a certain distance from the edge of the substrate, a high density state is maintained throughout the layered material, including the edge, and long-term measurement stability of electrocardiograms, for example, can be ensured.

[0034] In Figures 7(a) and 7(b), a conductive material 21C is formed on a portion of a two-dimensional surface 27 of a substrate 23C and a substrate 25A made of the same material as the substrates 23A and 23B formed of the above-mentioned conductive material.

[0035] The conductive material constituting the substrate 23C and the substrate 25A can be the same as the conductive material constituting the substrates 23A and 23B of conventional electrodes, such as at least one of metal materials such as gold, silver, copper, platinum, nickel, titanium, tin, iron, zinc, magnesium, aluminum, tungsten, and molybdenum, and conductive polymers. The conductive material constituting the electrode can be, for example, a conductive material in which the particle ratio of the layered material is 52% by mass or more and 83% by mass or less. The conductive material may also have a higher particle ratio of the layered material. This allows for the realization of an electrode that has excellent conductivity and flexibility, thereby reducing discomfort when worn.

[0036] 8(a) and 8(b) show an adhesive 26 formed on the substrate in an area where the conductive material is not provided in FIGS. 7(a) and 7(b), respectively. Specifically, FIG. 8(a) shows a preferred embodiment in which a first adhesive is formed on a region including an edge 28 on a flat surface 27 of the substrate. FIG. 8(b) shows a preferred embodiment in which the shape of the two-dimensional surface of the substrate, such as the flat surface, is circular or elliptical, has a depression in the center of the substrate, and a second adhesive is formed in the depression. Note that in FIGS. 8(a) and 8(b), the first and second adhesives are collectively referred to as adhesive 26. By providing an area where the adhesive 26 is formed, the adhesive 26 adheres to the skin when in contact, improving the contact of the conductive material with the skin and improving the detection accuracy of bioelectric signals such as electrocardiograms.

[0037] The first adhesive is preferably a hydrophobic adhesive. For example, one or more adhesives selected from the group consisting of rubber-based and silicone-based adhesives can be used as the hydrophobic adhesive. The thickness of the adhesive may be, for example, 10 μm to 1 mm. The first adhesive is more preferably an adhesive made of rubber or silicone.

[0038] In the case of the contact surface of the biosignal sensing electrode of this embodiment, for example, with the subject, it is preferable that the surfaces of the conductive material and the first adhesive are approximately flush, as shown in contact surface 19 with the subject in Figures 8(a) and 8(b).

[0039] The second adhesive is preferably a hydrophilic adhesive. The second adhesive is preferably a hydrophobic adhesive having higher adhesiveness than the first adhesive. As the hydrophilic adhesive, for example, an acrylic adhesive can be used.

[0040] 4(b) and 6(b) showing the embodiment of the conventional electrode, the conductive materials 21A and 21B are formed on the substrates 23A and 23B made of a conductive material, respectively, and further, Ti is formed on the contact surface 19 with the test object rather than the conductive materials 21A and 21B. ３ C ２ T ｘ Conductive materials 22A and 22B having a high ratio of Ti are formed, respectively. That is, Figures 4(b) and 6(b) correspond to conventional biosignal sensing electrodes in which the ratio of particles in the layered material is higher in the contact portion with the subject than in the non-contact portion with the subject. Although not shown, in Figures 7 and 8, two or more conductive materials having different ratios of particles in the layered material as in Figures 4(b) and 6(b) may also be stacked. If the conductive material has this configuration, Ti ３ C ２ T ｘ Since a high concentration of conductive material is formed on each surface that comes into contact with the subject, a biosignal sensing electrode with higher sensitivity can be provided. Therefore, even when the surface of the subject is difficult to detect biosignals from, for example, a patient with a thick stratum corneum, measurement can be performed without performing pretreatment that involves inflammation, such as removing the stratum corneum. Furthermore, the conductive material may be provided so that the proportion of particles of the layered material increases stepwise or in a gradient from the substrate formed of the conductive material toward the surface that comes into contact with the subject.

[0041] An example of a configuration in which the proportion of particles of the layered material is higher in the portion in contact with the test specimen than in the portion not in contact with the test specimen is where the proportion of particles of the layered material in the portion in contact with the test specimen is greater than 83 mass % and not more than 94 mass %, and the proportion of particles at half the thickness of the conductive material in a cross section of the electrode perpendicular to the contact surface with the test specimen is not less than 52 mass % and not more than 83 mass %.

[0042] As mentioned above, Ti３ C ２ T ｘ By using a conductive material containing the above, the impedance at the interface between the skin and the electrode is reduced compared to conventional electrodes, making it possible to detect necessary signals without providing protrusions. Therefore, as shown in Fig. 9, a plurality of biosignal sensing electrodes 30 of this embodiment can be attached to the skin of a subject's arm to measure, for example, myoelectric potential. In Fig. 9, 32 denotes lead wires, 33 denotes a cable, and 34 denotes an analysis system.

[0043] There are no particular limitations on the method for producing an electrode comprising the conductive material of this embodiment using the above-mentioned MXene. When the conductive material of this embodiment preferably contains a polymer and has a sheet-like form, for example, the layered material and the polymer can be mixed to form a coating film, as shown in the following example.

[0044] First, an MXene aqueous dispersion, an MXene dispersion in an organic dispersion medium, or MXene powder, in which MXene particles (particles of a layered material) are present in a dispersion medium, is mixed with a polymer. The dispersion medium of the MXene aqueous dispersion is typically water, and in some cases, it may contain a relatively small amount of other liquid substance in addition to water (for example, 30% by mass or less, preferably 20% by mass or less, based on the total).

[0045] The MXene particles and polymer can be stirred using a dispersing device such as a homogenizer, a propeller stirrer, a thin film rotary stirrer, a planetary mixer, a mechanical shaker, or a vortex mixer.

[0046] The slurry, which is a mixture of the MXene particles and polymer, can be applied to a substrate (e.g., a substrate) by any method. Examples of suitable methods include spray coating using a nozzle such as a one-fluid nozzle, a two-fluid nozzle, or an airbrush; slit coating using a table coater, comma coater, or bar coater; screen printing; metal mask printing; spin coating; and drop coating. As described above, the substrate can be a substrate made of a metal material, resin, or the like suitable for a biosignal sensing electrode.

[0047] The coating and drying steps may be repeated multiple times as necessary until a film of the desired thickness is obtained. Drying and curing may be carried out, for example, at a temperature of 400° C. or less using an atmospheric pressure oven or a vacuum oven.

[0048] Although the biosignal sensing electrode according to one embodiment of the present disclosure has been described in detail above, various modifications are possible. Note that the biosignal sensing electrode according to the present disclosure may be manufactured by a method different from that of the above-described embodiment. The disclosure of this specification may include the following aspects. <1> A biosignal sensing electrode comprising: a substrate; and a conductive material formed on a flat surface of the substrate, the conductive material including particles of a layered material including one or more layers, the conductive material having a contact surface on the side opposite to the substrate side where the entire surface of the conductive material comes into contact with a test subject, the layer being made of Ti. ３ C ２and a modification or termination T (T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer main body, wherein the conductive material is formed on a portion other than the end portion on the flat surface of the base material. <2> The biosignal sensing electrode according to <1>, having a first adhesive on the end portion on the flat surface of the base material. <3> The biosignal sensing electrode according to <2>, wherein the first adhesive is a hydrophobic adhesive. <4> The biosignal sensing electrode according to <3>, wherein the first adhesive is an adhesive made of rubber or silicone. <5> The biosignal sensing electrode according to any one of <1> to <4>, wherein the flat surface of the base material is circular or elliptical, wherein the base material has a depression in the center, and wherein a second adhesive is disposed in the depression. <6> The biosignal sensing electrode according to any one of <1> to <5>, wherein the conductive material and the first adhesive are substantially flush with each other. <7> The biosignal sensing electrode according to <5> or <6>, wherein the second adhesive is a hydrophilic adhesive. <8> The biosignal sensing electrode according to any one of <1> to <7>, wherein the conductive material includes a polymer, and the polymer is one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, sodium alginate, a water-soluble acrylic acid polymer, polyacrylamide, polyaniline sulfonic acid, and nylon.

[0049] This application claims priority from Japanese Patent Application No. 2024-022204, which is incorporated herein by reference.

[0050] The biosignal sensing electrodes of the present disclosure may be used in any suitable application, and may be preferably used in devices that extract and measure biosignals such as electromyogram signals and electrocardiogram signals.

[0051] 1a, 1b Layer body (M ｍ X ｎLayer) 3a, 5a, 3b, 5b Modified or terminated T 7a, 7b MXene layer 10, 10a, 10b MXene (layered material) 11 Polymer 19 Analyte contact surface of conductive material 20, 21A, 21B, 21C, 21D Conductive material 22A, 22B High-concentration MXene conductive material 23A, 23B, 23C, 23D Substrate formed of conductive material 24A, 24B, 25A, 25B Conventional snap-type electrode 26 Adhesive 27 Planar (two-dimensional) surface 28 Edge on planar (two-dimensional) surface 29 Edge of recess 30, 30A, 30B Biosignal sensing electrode 31A, 31B, 31C, 31D Snap portion of electrode 32, 32A, 32B Lead wire 33 Cable 34 Analysis System

Claims

1. A biosignal sensing electrode comprising: a substrate having a two-dimensional surface; and a conductive material including particles of a layered material including one or more layers formed on the two-dimensional surface of the substrate, the conductive material having a contact surface on the side opposite to the substrate that contacts a test subject, wherein the layer is made of Ti. ３ C ２ and a modification or termination T (wherein T is at least one selected from the group consisting of a hydroxyl group, a fluorine atom, a chlorine atom, an oxygen atom, and a hydrogen atom) present on the surface of the layer body, wherein the conductive material is formed on a region other than the end portion of the two-dimensional surface of the substrate.

2. The biosignal sensing electrode according to claim 1, having a first adhesive on the edge of the two-dimensional surface of the substrate.

3. The biosignal sensing electrode according to claim 2, wherein the first adhesive is a hydrophobic adhesive.

4. The biosignal sensing electrode according to claim 3, wherein the first adhesive is an adhesive made of rubber or silicone.

5. A biosignal sensing electrode according to any one of claims 1 to 4, wherein the shape of the two-dimensional surface of the substrate is circular or elliptical, the substrate has a depression in the center of the two-dimensional surface, and the depression has a second adhesive.

6. A biosignal sensing electrode according to any one of claims 1 to 5, wherein the surfaces of the conductive material and the first adhesive are substantially flush with each other.

7. The biosignal sensing electrode according to claim 5 or 6, wherein the second adhesive is a hydrophilic adhesive.

8. A biosignal sensing electrode according to any one of claims 1 to 7, wherein the conductive material includes a polymer, and the polymer is one or more types of polymer selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymer, polyacrylamide, polyaniline sulfonic acid, and nylon.

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