Biosignal sensing electrodes

Abstract

Provided is a biological signal sensing electrode having high conductivity (low impedance), good adhesion to a subject, and resistance to peeling, and no discomfort when worn. The biological signal sensing electrode comprises a laminate of a conductive film and a porous film, wherein the conductive film comprises particles of a layered material, wherein the layered material comprises one or more layers, wherein the layers comprise a layer body and a modification or termination T present on the surface of the layer body, 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, wherein the layer body is represented by the following formula: m X n , wherein M is at least one metal of Groups 3, 4, 5, 6, or 7, X is a carbon atom, a nitrogen atom, or a combination thereof, n is greater than 1 and less than 4, m is greater than n and less than 5, and the porous membrane is provided on the contact surface with the object to be tested.

Description

Technical Field

[0001] The present invention relates to a biological signal sensing electrode. Background Art

[0002] As a method for detecting biological information such as electrical signals from muscles and hearts of a subject (patient) without causing pain to the human body, a method of making a sheet-shaped electrode contact the subject and performing a measurement can be cited. For example, Patent Document 1 shows a biological electrode coating pad using a hydrophilic gel containing water and electrolytes. In addition, Patent Document 2 shows a biological potential electrode comprising (a) an electrical conductor, (b) a film having selective permeability with respect to ion conduction in order to present a dry surface to the subject, and (c) a conductive medium configured to communicate with a part of the electrical conductor and a part of the film. However, in recent years, MXene has attracted attention as a new material with electrical conductivity. MXene is a so-called two-dimensional material, which is a layered material having a morphology of one layer or multiple layers, as described later. Generally, MXene has the morphology of particles of such a layered material (which may include powder, flakes, nanosheets, etc.). Patent Document 3 shows a biological electrode formed by a contact material including this MXene.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2013 / 039151 Pamphlet

[0006] Patent Document 2: U.S. Patent No. 8,798,710

[0007] Patent Document 3: International Publication No. 2019 / 055784 Pamphlet Summary of the Invention

[0008] Problems to be solved by the invention

[0009] The bioelectrical electrode pad of Patent Document 1 changes its impedance as its moisture content changes due to drying, making it difficult to obtain a high-precision signal. Furthermore, the presence of water in the pad can cause a wet, uncomfortable feeling when worn. The biopotential electrode of Patent Document 2 has a high impedance due to its numerous layers and layer interfaces, making it difficult to obtain a high-precision signal. Furthermore, Patent Document 3 uses MXene in the portion in contact with the subject, but the MXene can detach due to contact, making stable measurements over long periods of time difficult.

[0010] An object of the present invention is to provide a biological signal sensing electrode that exhibits high conductivity (low impedance), suppresses peeling of a predetermined layered material (also referred to as "MXene" in this specification), and does not cause discomfort when worn.

[0011] Means used to solve problems

[0012] According to one aspect of the present invention, a biological signal sensing electrode is provided, wherein:

[0013] The biological signal sensing electrode comprises a stack of a conductive film and a porous film, wherein the conductive film contains particles of a layered material, and the layered material comprises one or more layers.

[0014] The layer includes a layer body and a modification or termination T present on the surface of the layer body, 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.

[0015] The main body of this layer is represented by the following formula:

[0016] M m X n

[0017] Wherein, M is at least one metal of Groups 3, 4, 5, 6, or 7,

[0018] X is a carbon atom, a nitrogen atom or a combination thereof,

[0019] n is 1 or more and 4 or less,

[0020] m is greater than n and less than 5,

[0021] The porous membrane is provided on the surface in contact with the subject.

[0022] Effects of the Invention

[0023] According to the present invention, a biological signal sensing electrode includes a stack of a conductive film and a porous film, wherein the conductive film contains particles of a specified layered material, and the porous film is arranged on a contact surface with the subject, thereby providing a biological signal sensing electrode that exhibits high conductivity (low impedance), suppresses MXene peeling, and does not cause discomfort when worn. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are diagrams illustrating a conductive film in one embodiment of a biological signal sensing electrode according to the present invention. (a) shows a schematic cross-sectional view of the conductive film, and (b) shows a schematic perspective view of MXene in the conductive film.

[0025] Figure 2Schematic cross-sectional views showing MXene, a layered material that can be used as a conductive film in one embodiment of a biological signal sensing electrode of the present invention. (a) shows a single-layer MXene, and (b) shows a multilayer (two-layer, for example) MXene.

[0026] Figure 3 This is a schematic cross-sectional view schematically showing a conductive film in another embodiment of the present invention.

[0027] Figure 4 This is a diagram illustrating the pore shape of the porous membrane in the biological signal sensing electrode of the present invention.

[0028] Figure 5 This is a schematic cross-sectional view schematically showing a biological signal sensing electrode in one embodiment of the present invention.

[0029] Figure 6 This is a schematic cross-sectional view schematically showing a biological signal sensing electrode in another embodiment of the present invention.

[0030] Figure 7 This is a schematic perspective view showing a schematic diagram of a biological signal sensing electrode in another embodiment of the present invention.

[0031] Figure 8 This is a schematic cross-sectional view schematically showing a biological signal sensing electrode in another embodiment of the present invention.

[0032] Figure 9 This is a schematic cross-sectional view schematically showing a biological signal sensing electrode in another embodiment of the present invention. DETAILED DESCRIPTION

[0033] Hereinafter, the biological signal sensing electrode in the embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments.

[0034] The biological signal sensing electrode in the embodiment of the present invention comprises a laminate of a conductive film and a porous film. The conductive film contains particles of a layered material, and the layered material comprises one or more layers. First, the conductive film and the porous film are described separately.

[0035] [Conductive film]

[0036] Reference Figure 1 The conductive film 30 included in the electrode of this embodiment includes particles 10 of a predetermined layered material. The particles of the predetermined layered material included in the conductive film of this embodiment are defined as follows.

[0037] A layered material comprising one or more layers, wherein the layer comprises a layer body and a modification or termination T present on a surface of the layer body (more specifically, at least one of two mutually opposing surfaces of the layer body), 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.

[0038] The main body of this layer is represented by the following formula:

[0039] M m X n

[0040] Wherein, M is at least one metal of Groups 3, 4, 5, 6, and 7, i.e., a so-called early transition metal, and may include, for example, at least one selected from the group consisting of Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and Mn,

[0041] x is a carbon atom, a nitrogen atom or a combination thereof,

[0042] n is 1 or more and 4 or less,

[0043] m is greater than n and less than 5,

[0044] The layer body may have a lattice where each x lies within an octahedral array of M,

[0045] Layered materials can be understood as layered compounds, and can also be expressed as "M m X n T s ", s is an arbitrary number. In the past, x was sometimes used instead of s.

[0046] Representatively, n may be 1, 2, 3, or 4, but is not limited thereto.

[0047] In the above formula of MXene, M is preferably at least one selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn, and more preferably at least one selected from the group consisting of Ti, V, Cr and Mo.

[0048] Such MXenes can be synthesized by selectively etching (removing and sometimes layering) A atoms (and sometimes a portion of M atoms) from the MAX phase. The MAX phase is represented by the following formula:

[0049] M m AX n ,

[0050] In the formula, M, X, n and m are as described above, A is at least one element of Groups 12, 13, 14, 15 and 16, and Group A elements are typically represented by Groups IIIA and IVA. More specifically, it may include at least one element selected from the group consisting of Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, S and Cd, preferably Al.

[0051] And, a layer composed of A atoms is located on the m X n The crystal structure between two layers (which may have a lattice where each x is located in an octahedral array of M) represented by the MAX phase. As a representative example, when m=n+1, there are layers of X atoms arranged between n+1 layers of M atoms (these are collectively referred to as "M m x n The repeating unit is a layer of A atoms ("A atom layer") arranged as a layer next to the layer of the n+1th M atom, but is not limited thereto. The A atom layer (and sometimes a part of the M atoms) is removed by selectively etching (removing and sometimes layer-separating) the A atoms (and sometimes a part of the M atoms) from the MAX phase, and the exposed M atoms are m X n The surface modification of the layer is carried out by hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms and hydrogen atoms in the etching solution (usually an aqueous solution containing fluorine acid is used, but not limited thereto) and terminates the surface. - The etching solution can be used, for example, a method combining etching and embedding using a mixture of lithium fluoride and hydrochloric acid, which also serves as an embedding agent, or a method using fluoric acid. Afterwards, any appropriate post-treatment (for example, embedding of an embedding agent as one of the interlayer exfoliation treatments, ultrasonic treatment, manual shaking or an automatic shaker, etc.) can be appropriately used to promote the layer separation of MXene (delamination, separation of multilayer MXene into single-layer MXene). It should be noted that ultrasonic treatment may destroy MXene due to excessive shear force. Therefore, when it is desired to obtain a two-dimensional MXene with a larger aspect ratio (preferably a single-layer MXene), it is preferred to apply appropriate shear force by manual shaking or an automatic shaker.

[0052] After the above post-treatment, a centrifugal separator can be used to separate the supernatant containing a single layer of MXene and / or a small number of layers of MXene with approximately 2 to 5 layers, and a lower supernatant containing multilayer MXene. In this embodiment, the MXene contained in the supernatant and / or lower supernatant can be used as particles of a layered material. When the MXene contained in the supernatant containing a single layer or a small number of layers of MXene is used as particles of a layered material, low impedance can be easily achieved, which is preferred.

[0053] The above formula M of known MXene m X n It is expressed as follows.

[0054] Sc2C, Ti2C, Ti2N, Zr2C, Zr2N, Hf2C, Hf2N, V2C, V2N, Nb2C, Ta2C, Cr2C, Cr2N, Mo2C, Mo 1.3 C, Cr 1.3 C, (Ti, V) 2C, (Ti, Nb) 2C, W2C, W 1.3 C, Mo2N, Nb 1.3 C.Mo 1.3 Y 0.6 C (In the above formula, "1.3" and "0.6" refer to approximately 1.3 (= 4 / 3) and approximately 0.6 (= 2 / 3), respectively.)

[0055] Ti3C2, Ti3N2, Ti3(CN), Zr3C2, (Ti, V)3C2, (Ti2Nb)C2, (Ti2Ta)C2, (Ti2Mn)C2, Hf3C2, (Hf2V)C2, (Hf2Mn)C2, (V2Ti)C2, (Cr2Ti)C2, (Cr2V)C 2. (Cr2Nb)C2, (Cr2Ta)C2, (Mo2Sc)C2, (Mo2Ti)C2, (Mo2Zr)C2, (Mo2Hf)C2, (Mo2V)C2, (Mo2Nb)C2, (Mo2Ta)C2, (W2Ti)C2, (W2Zr)C2, (W2Hf)C2,

[0056] Ti4N3, V4C3, Nb4C3, Ta4C3, (Ti, Nb)4C3, (Nb, Zr)4C3, (Ti2Nb2)C3, (Ti2Ta2)C3, (V2Ti2)C3, (V2Nb2)C3, (V2Ta2)C3, (Nb2Ta2)C3, (Cr2Ti2)C3, (Cr2V 2)C3, (Cr2Nb2)C3, (Cr2Ta2)C3, (Mo2Ti2)C3, (Mo2Zr2)C3, (Mo2Hf2)C3, (Mo2V2)C3, (Mo2Nb2)C3, (Mo2Ta2)C3, (W2Ti2)C3, (W2Zr2)C3, (W2Hf2)C3, (Mo 2.7 V 1.3 )C3 (In the above formula, "2.7" and "1.3" respectively refer to approximately 2.7 (= 8 / 3) and approximately 1.3 (= 4 / 3).)

[0057] As a representative example, in the above formula, M can be titanium or vanadium, and X can be a carbon atom or a nitrogen atom. For example, MAX phase is Ti3AlC2, and MXene is Ti3C2T s (In other words, M is Ti, X is C, n is 2, and m is 3).

[0058] It should be noted that in the present invention, MXene may contain residual A atoms in a relatively small amount, for example, 10% by mass or less relative to the original A atoms. The residual amount of A atoms may preferably be 8% by mass or less, and more preferably 6% by mass or less. However, even if the residual amount of A atoms exceeds 10% by mass, there may be no problem depending on the application and usage conditions of the conductive film.

[0059] MXene (particles) synthesized in this way 10 Figure 2 As schematically shown in FIG. 1 , the layered material may include one or more MXene layers 7a, 7b (as an example of MXene (particles) 10, in FIG. Figure 2 (a) shows a layer of MXene10a. Figure 2 (b) shows two layers of MXene 10b, but is not limited to these examples). In more detail, the MXene layers 7a and 7b have MXene 10b. m X n The layer body represented by m X n MXene layers 1a, 1b, and modifications or terminations T 3a, 5a, 3b, 5b present on the surface of the layer bodies 1a, 1b (more specifically, at least one of the two surfaces facing each other in each layer). Therefore, MXene layers 7a, 7b are also represented as “MXene layers”. m X n T s ", s is an arbitrary number. MXene10 may have a structure in which the MXene layers are separated and exist as one layer ( Figure 2 The single-layer structure shown in (a), so-called single-layer MXene 10a), can also be a stacked structure in which multiple MXene layers are stacked separately from each other ( Figure 2 The multilayer structure shown in (b), so-called multilayer MXene 10b, may also be a mixture thereof. MXene 10 may be particles (also referred to as powder or flakes) that are aggregates of single-layer MXene 10a and / or multilayer MXene 10b. In the case of multilayer MXene, two adjacent MXene layers (e.g., 7a and 7b) may not necessarily be completely separated and may be partially in contact.

[0060] Although not limited to the present embodiment, the thickness of each layer of MXene (equivalent to the above-mentioned MXene layers 7a and 7b) is, for example, 0.8 nm or more and 5 nm or less, particularly 0.8 nm or more and 3 nm or less (mainly depending on the number of M 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 or more and 200 μm or less, particularly 1 μm or more and 40 μm or less. In the case where the MXene is a laminate (multilayer MXene), for each laminate, the interlayer distance (or gap size, Figure 2 (b) is indicated by Δd), for example, it can be greater than 0.8 nm and less than 10 nm, in particular, it can be greater than 0.8 nm and less than 5 nm, and more particularly, it can be about 1 nm. The multilayer MXene that can be included is preferably a MXene with a small number of layers obtained by interlayer exfoliation treatment. The "small number of layers" refers to, for example, that the number of stacking layers of MXene is less than 6 layers. In addition, the thickness of the multilayer MXene with a small number of layers in the stacking direction is preferably less than 10 nm. Hereinafter, this "multilayer MXene with a small number of layers" is sometimes referred to as "small-layer MXene". In addition, single-layer MXene and small-layer MXene are sometimes collectively referred to as "single-layer / small-layer MXene".

[0061] The MXene (particles) of this embodiment preferably include a monolayer MXene and a few-layer MXene, i.e., a monolayer / few-layer MXene. The MXene (particles) preferably contain monolayer / few-layer MXene with a thickness of 10 nm or less, with the ratio of 90% by volume or more, more preferably 95% by volume or more.

[0062] The total number of layers may be two or more, but for example, it may be 50 or more and 100,000 or less, and in particular, it may be 1,000 or more and 20,000 or less. The thickness of the conductive film in the stacking direction may be, for example, 0.1 μm or more and 200 μm or less, and in particular, 1 μm or more and 40 μm or less. The maximum dimension in a plane (two-dimensional sheet surface) perpendicular to the stacking direction may be, for example, 0.1 μm or more and 100 μm or less, and in particular, 1 μm or more and 20 μm or less. It should be noted that these dimensions can be obtained as the number average size (for example, at least 40 number averages) based on a photograph taken with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an atomic force microscope (AFM), or as the distance in the actual space calculated based on the position in the inverse lattice space of the (002) plane measured by the X-ray diffraction (XRD) method.

[0063] The conductive film comprising the layered particles preferably has a thickness of 0.5 μm to 20 μm. Increasing the thickness of the conductive film stabilizes and reduces impedance, so the thickness is preferably 0.5 μm or greater. The thickness is more preferably 1.0 μm or greater. From the perspective of conductivity, a thicker film is preferred. However, when flexibility is required, the film thickness is preferably 20 μm or less, and more preferably 15 μm or less.

[0064] The thickness of the conductive film can be measured, for example, by measurement with a micrometer or cross-sectional observation using a scanning electron microscope (SEM), a microscope, or a laser microscope.

[0065] As a conductive film according to an embodiment of the present invention, for example Figure 3 In the figure, the conductive thin film 30 is shown in which only the conductive two-dimensional particles 10 are stacked, but the present invention is not limited thereto.

[0066] The conductive film may also be a conductive composite material film (conductive composite material film) further comprising a polymer. The polymer may be contained as an additive such as an adhesive added when the film is formed, or may be added for strength or flexibility. In the case of the conductive composite material film, the proportion of the polymer in the conductive composite material film (when dry) exceeds 0 volume %, and preferably can be 30 volume % or less. The proportion of the polymer may further be 10 volume % or less, and further may be 5 volume % or less. In other words, the proportion of the particles of the layered material in the conductive composite material film (when dry) is preferably 70 volume % or more, and further may be 90 volume % or more, and further may be 95 volume % or more. A laminated film of two or more conductive composite materials having different proportions of the particles of the layered material may also be provided in one electrode as a conductive film.

[0067] The polymer is preferably a hydrophilic polymer having a polar group that forms a hydrogen bond with the modification or terminal T of the layer. For example, one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid, and nylon are preferably used.

[0068] Among them, more preferably one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol and sodium alginate. As the polymer, preferably a polymer having a carbamate bond having both hydrogen bond donor and hydrogen bond acceptor properties, from this viewpoint, the water-soluble polyurethane is particularly preferred.

[0069] The conductive film of the present embodiment, for example, when in the form of a sheet with a film thickness of 5 μm, preferably maintains a conductivity of 500 S / cm or more. For the conductivity, it is preferred to be able to maintain a conductivity of 1000 S / cm or more, more preferably to be able to maintain a conductivity of 1800 S / cm or more, further preferably to be able to maintain a conductivity of 2400 S / cm or more, and even more preferably to be able to maintain a conductivity of 2900 S / cm or more. There is no particular upper limit on the conductivity of the conductive film, but for example, it can be 10000 S / cm or less. The conductivity can be calculated as follows. That is, the surface resistivity can be measured by a 4-probe method, and the value obtained by multiplying the thickness [cm] by the surface resistivity [Ω / □] becomes the volume resistivity [Ω.cm], and the conductivity [S / cm] is calculated as the reciprocal thereof.

[0070] [Porous membrane]

[0071] Next, the porous membrane is described. The porous membrane is placed on the surface of the electrode that contacts the subject, with the conductive membrane directly contacting the surface opposite the contact surface. As used herein, the term "porous membrane" refers to a membrane having micropores that selectively allows ions and molecules smaller than the pore diameter to pass through.

[0072] The average pore size of the porous membrane is preferably 1 nm or more and 1 μm or less. Ions originating from the subject, i.e., the human body, pass through the porous membrane in contact with the subject and reach the conductive membrane, thereby enabling the measurement of electrodes such as myoelectricity of the subject. That is, the porous membrane has the function of preventing direct contact between the subject and the conductive membrane, and the function of a permeable membrane for the above-mentioned ions, etc. From the viewpoint of easily allowing the above-mentioned ions, etc., which become current carriers, to pass through and easily reducing impedance, the average pore size of the porous membrane is preferably 1 nm or more. The average pore size is more preferably 10 nm or more. On the other hand, from the viewpoint of fully suppressing the detachment of the conductive membrane and exerting the excellent performance of the conductive membrane for a long time, the average pore size of the porous membrane is preferably 1 μm or less, more preferably 500 nm or less. The average pore size is obtained as a number average size (e.g., at least 40 number averages) by image analysis based on a photograph taken with a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

[0073] The pore shape of the porous membrane is not limited, for example Figure 4 As schematically illustrated in FIG, it can be (a) agglomerated particle-like porous membrane having a plurality of pores 26, (b) a mesh-like porous membrane, (c) a fibrous porous membrane, (d) a porous membrane having a plurality of isolated and / or interconnected pores (in Figure 4 (d) exemplifies a porous membrane having a plurality of cylindrical pores formed perpendicular to the paper surface) or a porous membrane having a honeycomb structure (not shown).

[0074] The porous membrane may be insulating or conductive. The porous membrane preferably has a conductivity lower than that of the conductive membrane. As described above, the conductivity of the conductive membrane is 500 S / cm or higher. Since the porous membrane has a conductivity lower than that of the conductive membrane, ions from the subject can be more easily transferred to the conductive membrane, and as a result, biological signals such as myoelectricity can be measured more accurately.

[0075] The material of the porous membrane is not particularly limited, and a material formed of an organic material, an inorganic material, or a mixture thereof can be used. Examples of organic materials having a lower conductivity than that of the conductive membrane include polymers, and examples of inorganic materials having a lower conductivity than that of the conductive membrane include ceramics, or a combination thereof.

[0076] The porous membrane preferably includes a hydrophilic polymer. Examples of such hydrophilic polymers include polymers rendered hydrophilic by combining a hydrophilic auxiliary agent with a hydrophobic polymer, and polymers obtained by hydrophilizing the surface of a hydrophobic polymer. Including a hydrophilic polymer in the porous membrane can further enhance adhesion to the hydrophilic conductive membrane (MXene membrane), as described above.

[0077] As hydrophilic polymers (including polymers rendered hydrophilic by combining a hydrophilic auxiliary agent with a hydrophobic polymer, and polymers obtained by hydrophilizing the surface of a hydrophobic polymer, etc.) that can further improve adhesion to the conductive film (MXene film), more preferably include one or more selected from the group consisting of polysulfone, cellulose acetate, regenerated cellulose, polyethersulfone, water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid-based water-soluble polymers, polyacrylamide, polyaniline sulfonic acid, and nylon. It is further preferred that the porous membrane be composed of at least 50% by mass of the hydrophilic polymer, and it is particularly preferred that the porous membrane be composed of at least one of the hydrophilic polymers.

[0078] In addition, enumerate on the surface of hydrophobic polymer (for example, olefin resins such as polyethylene, polypropylene, polystyrene, fluororesins such as vinyl resins such as polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyester etc.) for example by plasma treatment, various known methods such as graft polymerization processes implement the hydrophilicization treatment and the hydrophilic polymer obtained.As described hydrophobic polymer, more preferably one selected from the group consisting of polypropylene, polyethylene, polyvinylidene fluoride and polytetrafluoroethylene.Above-mentioned hydrophobic polymer can also be the laminated structure of a plurality of different hydrophobic polymers such as polypropylene and polyethylene.Also can replace described hydrophobic polymer, on the surface of ceramics such as aluminum oxide, aluminum nitride, silicon nitride, zirconium oxide, implement above-mentioned hydrophilicization treatment.

[0079] The thickness of the porous membrane is preferably 0.1 μm or more and 300 μm or less. The thinner the thickness of the porous membrane, the easier it is for ions to penetrate, and the more impedance can be reduced. From this viewpoint, the thickness of the porous membrane is preferably 300 μm or less, more preferably 200 μm or less. On the other hand, from the viewpoint of ensuring durability, the thickness of the porous membrane is preferably 0.1 μm or more. The thickness of the porous membrane can be measured, for example, by cross-sectional observation using a micrometer, a scanning electron microscope (SEM), a microscope, or a laser microscope.

[0080] The contact area between the conductive film and the porous film is not particularly limited, as long as the electrode exhibits high conductivity, suppresses MXene peeling, and does not cause discomfort when worn. The entire surface of the conductive film and the porous film may be in contact with each other, or (a) the porous film may be in contact with a portion of the conductive film, or (b) the conductive film may be in contact with a portion of the porous film. Figure 5 This is a diagram showing an example of the above-mentioned (a), in which a porous film 22 and, for example, an insulating film 25 are provided on the surface of the conductive film 21 on the subject side. Figure 6 This figure shows an example of (b), in which a porous film 22 is provided on a surface formed by a conductive film 21 and, for example, an insulating film 25. From the viewpoint of more easily achieving the above-mentioned characteristics, the contact area ratio of the surface of the conductive film on the subject side with the porous film is preferably 60% or more, more preferably 80% or more, and most preferably 100%.

[0081] As the porous membrane, in addition to using commercial products, the porous membrane can also be obtained by methods such as phase change method, melt quenching method, extraction method, electron beam irradiation method, etc. The phase change method is a method in which a film-forming solution (casting liquid) prepared by dissolving an organic polymer in an organic solvent is cast onto a glass plate, etc., and then the film is immersed in a suitable gelling liquid (organic solvent, water, etc. in which the organic polymer is insoluble) or dried, etc., and micropores are formed by the two-phase separation phenomenon generated at this time. The melt quenching method is a method in which a varnish is formed by combining a solvent and a polymer in which the solubility varies greatly depending on the temperature, and then the film is rapidly solidified. The extraction method (replication method) is a method in which an additive that can be easily extracted in a subsequent process is added to a polymer solution or dispersion, and after the polymer is formed into a film, the additive is extracted by a suitable method. The electron beam irradiation method is a production method in which electron beams (charged particles) are irradiated onto a polymer thin film of about 10 μm to form particle tracks on the film, and then etching is performed with a solvent to expand the tracks and form micropores.

[0082] [Biological signal sensing electrode]

[0083] The biological signal sensing electrode of this embodiment includes a stack of conductive membranes and porous membranes in direct contact, and the porous membrane is provided on the contact surface with the subject, and is not limited to a specific form. Regarding the electrode, a soft electrode with flexibility is considered from a solid state electrode. However, from the perspective of tracking with the biological body (skin) and suppressing electrode cracks, it is preferred to have as much flexibility as possible.

[0084] As one embodiment of the biological signal sensing electrode, Figure 7 A schematic perspective view illustrating a snap-fit electrode. Figure 7 A schematic perspective view of a snap-on type electrode is shown in which a lead wire 32 is connected to a snap-on portion 31 of an electrode 30 having a flat surface that contacts a subject. Figure 8 Schematically shown Figure 7 An example of a cross-sectional view of the electrode 30.

[0085] exist Figure 8 In the embodiment, the conductive film 21 is formed on a base material 23 formed of a conductive material. By forming the conductive film 21 and the porous film 22 as the contact surface with the subject, a biological signal sensing electrode with high sensitivity and reduced discomfort when worn can be provided.

[0086] Examples of the conductive material constituting the substrate 23 include at least one material selected from metal materials such as gold, silver, copper, platinum, nickel, titanium, tin, iron, zinc, magnesium, aluminum, tungsten, molybdenum, and conductive polymers.

[0087] As another embodiment, Figure 9 As shown, the substrate can also be a conventional snap-fit electrode 24. The conductive material constituting this snap-fit electrode can be the same material as the conductive material used for substrate 23. This configuration utilizes a versatile extraction electrode, thereby providing a low-cost, highly sensitive biological signal sensing electrode.

[0088] In another embodiment, when the conductive film is a conductive composite material film of a MXene film and a polymer, the electrode may be a laminated film of the conductive composite material film and a porous film and may not have a substrate.

[0089] The living body signal sensing electrodes of this embodiment do not contain water, as in Patent Document 1, and therefore do not experience the discomfort of being soaked when worn. Furthermore, if moisture is present, as in Patent Document 1, impedance changes due to drying may occur. In contrast, the living body signal sensing electrodes of this embodiment are dry electrodes, thus avoiding such impedance changes due to drying and providing high signal reliability.

[0090] The biological signal sensing electrode of this embodiment includes a low-impedance MXene film as an electrical conductor, so the signal accuracy is high. In addition, the stacking of the conductive film (MXene film) and the porous film is flexible, so there is no need to set a layer for following the skin. Therefore, in the biological signal sensing electrode of this embodiment, the number of layers is small, and low impedance can be achieved more easily. In contrast, for example, in Patent Document 2, the electrical conductor is hard, and from the perspective of following the skin, a layer of conductive medium must be provided. As a result, the number of layers is large and the impedance becomes high.

[0091] Furthermore, in the biological signal sensing electrode of this embodiment, the conductive film is protected by a porous film, and the contact layer with the subject is a porous film, thereby preventing MXene from detaching from the conductive film. The porous film has ion conductivity that easily allows ions from the subject to pass through, and has low impedance.

[0092] Direct contact between the conductive film and the porous membrane enhances the adhesion between the hydrophilic conductive film (MXene film) and the porous membrane, which preferably comprises a hydrophilic polymer. This high adhesion is ensured even without the need for an intermediate layer containing an adhesive or the like between the conductive and porous membranes. As a result, with fewer layers, the distance traveled by ions from the specimen through the porous membrane to the conductive membrane is shortened, making it easier to achieve low impedance and further improving the sensitivity of the electrode.

[0093] [Method for manufacturing biological signal sensing electrode]

[0094] The method for producing the electrode of the present embodiment using the MXene produced as described above is not particularly limited. When the conductive film of the present embodiment has a sheet-like form, the electrode can be formed as exemplified below.

[0095] First, a MXene aqueous dispersion or a MXene organic solvent dispersion containing the MXene particles (layered material particles) in a solvent is prepared. The solvent of the MXene aqueous dispersion is typically water, but other liquid substances may also be included in addition to water in relatively small amounts (e.g., 30% by mass or less, preferably 20% by mass or less, based on the total weight).

[0096] More specifically, as described above, a MXene-containing aqueous medium can be obtained at any appropriate time by performing the following operation: subjecting the MXene-containing aqueous mixture obtained by selectively etching A atoms from the MAX phase to solid-liquid separation (e.g., sedimentation, centrifugation, etc.), partially removing the aqueous solvent (liquid phase) from the mixture, adding fresh aqueous solvent to the mixture, and applying shear force to the mixture. This operation can be performed once or, in some cases, can be repeated two or more times.

[0097] Before drying, a MXene-containing aqueous medium, such as a MXene aqueous dispersion or a MXene organic solvent dispersion, can be used to form a precursor of the conductive film (also referred to as a "precursor film"). The method for forming the precursor film is not particularly limited, and examples thereof include coating, filtration, and spraying.

[0098] In more detail, the aqueous medium containing MXene is applied to the substrate directly or after appropriate adjustment (for example, dilution with an aqueous solvent or addition of an adhesive). As a coating method, for example, a method of spraying using a nozzle such as a single-fluid nozzle, a two-fluid nozzle, a spray gun, etc., a slit coating method using a desktop coater, a comma coater, a rod coater, screen printing, metal mask printing, spin coating, dip coating, drop coating, etc. are cited. As the substrate, a substrate formed of a metal material, a resin, etc. suitable for a biological signal sensing electrode can be appropriately used. By coating on any appropriate substrate (which can constitute a prescribed component together with the conductive film, or can ultimately be separated from the conductive film), a precursor film can be formed on the substrate.

[0099] Alternatively, the MXene-containing aqueous medium is appropriately adjusted (e.g., diluted with an aqueous solvent) and filtered through a filter (which may constitute a predetermined component together with the conductive film or may ultimately be separated from the conductive film) provided on a suction filter, thereby at least partially removing the aqueous solvent. This allows the precursor to be formed on the filter. The filter is not particularly limited, but a membrane filter or the like may be used. This filtration allows the production of a conductive film without the use of adhesives or the like.

[0100] Next, the precursor formed by the above is dried as described above. Figure 3 As schematically shown in FIG, a conductive film 30 is obtained. In the present invention, "drying" refers to removing the aqueous solvent that may be present in the precursor.

[0101] Drying can be performed under mild conditions such as natural drying (typically, placement in an air atmosphere at room temperature and pressure) or air drying (blowing air), or under more aggressive conditions such as hot air drying (blowing heated air), heat drying, and / or vacuum drying. For example, drying can be performed using an atmospheric pressure oven or a vacuum oven at a temperature of 400°C or less.

[0102] The formation and drying of the precursor may be repeated as needed until the desired conductive film thickness is obtained. For example, a combination of spraying and drying may be repeated multiple times.

[0103] Even when the conductive film comprises a polymer, the method for producing an electrode comprising the conductive composite material is not particularly limited. When the conductive composite material of this embodiment has a sheet-like form, for example, as exemplified below, the layered material can be mixed with a polymer to form a coating film.

[0104] First, a MXene aqueous dispersion, MXene organic solvent dispersion, or MXene powder containing the MXene particles (layered material particles) in a solvent is mixed with a polymer. The solvent of the MXene aqueous dispersion is typically water, but other liquid substances may also be included in relatively small amounts (e.g., 30% by mass or less, preferably 20% by mass or less, based on the total weight) in addition to water.

[0105] The MXene particles and the polymer can be stirred using a dispersion device such as a homogenizer, a propeller stirrer, a thin film gyratory stirrer, a planetary stirrer, a mechanical vibrator, or a vortex mixer.

[0106] The slurry of the mixture of the MXene particles and the polymer is applied to a substrate (e.g., a substrate), but the coating method is not limited. For example, a method of spraying using a nozzle such as a single-fluid nozzle, a two-fluid nozzle, a spray gun, a slit coating method using a desktop coater, a comma coater, a rod coater, screen printing, a metal mask printing method, and a coating method based on spin coating, dip coating, and drop coating are cited. As described above, the substrate can be appropriately formed of a metal material, resin, or the like suitable for a biological signal sensing electrode.

[0107] The coating and drying may be repeated as needed to obtain a desired film thickness. For example, drying and curing may be performed in an atmospheric oven or a vacuum oven at a temperature below 400 degrees.

[0108] After forming a MXene film by any of the above methods, before drying / curing the MXene film, a commercially available product may be stacked as a porous film as described above, and then the MXene film may be dried / cured, or after drying / curing the MXene film, a porous film may be formed on the surface of the MXene film by the above-mentioned phase change method or the like.

[0109] The above details the biological signal sensing electrode according to one embodiment of the present invention, but various modifications are possible. It should be noted that the biological signal sensing electrode according to the present invention can also be manufactured using a method different from that in the above embodiment.

[0110] Example

[0111] Modulation of MAX particles

[0112] TiC powder, Ti powder, and Al powder (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were placed in a ball mill containing zirconia balls at a molar ratio of 2:1:1 and mixed for 24 hours. The resulting mixed powder was sintered at 1350°C for two hours under an Ar atmosphere. The resulting sintered body (MAX block) was crushed to a maximum size of 40 μm or less using an end mill. This yielded Ti3AlC2 particles as MAX particles.

[0113] Preparation of MXene dispersion

[0114] The Ti3AlC2 particles (powder) prepared by the above method were weighed 1 g, and a fluorine resin container was used to add 1 g of LiF to 10 mL of 9 mol / L hydrochloric acid. The mixture was stirred with a stirrer at 35 ° C for 24 hours to perform etching to obtain a solid-liquid mixture (suspension) containing solid components derived from the Ti3AlC2 powder. The solid-liquid mixture (suspension) after etching was transferred to a centrifuge tube, pure water was added for stirring, and the supernatant and precipitate were separated by a centrifugal separator, and the supernatant was discarded. This was repeated 10 times to clean it. Afterwards, a mechanical vibrator was used to treat it for a specified time, thereby performing a stratification process. Afterwards, the supernatant was recovered by centrifugal separation and used as a MXene aqueous dispersion.

[0115] Fabrication of biological signal sensing electrode samples

[0116] A hydrophilic porous membrane (manufactured by Merck, product number GPWP04700, hydrophilic polyethersulfone (PES) membrane, thickness of about 175 μm, pore size of 0.22 μm) was cut with scissors to an area of 196 mm. 2 On the obtained film, an aqueous dispersion containing 4.5% by mass of MXene was sprayed for 3 seconds, and then temporarily dried using a dryer. After repeating the spraying and temporary drying five times, the film was formally dried in an oven at 80°C and 30 minutes to obtain a conductive film (MXene film) with a thickness of 5 μm. The laminated film of the conductive film (MXene film) and the hydrophilic porous film was used as a biological signal sensing electrode sample. As a comparative example 1, a sample was prepared in which only a MXene film (with an area of 196 mm) was used instead of the above-mentioned porous film. 2 A biosensing electrode sample was prepared in the same manner as above, except for a MXene film with a thickness of 5 μm. Furthermore, as Comparative Example 2, a commercially available bioelectrode, a monitoring electrode manufactured by 3M (Product No. 2228), was also prepared.

[0117] The impedance of the biological signal sensing electrode sample (MXene film + porous film) of this embodiment, the impedance of the biological signal sensing electrode sample (MXene film only) of Comparative Example 1, and the impedance of the commercially available electrode of Comparative Example 2 were measured by the following method.

[0118] Each of the electrodes (samples) was placed in contact with a substance obtained by removing the skin of a chicken, which is considered equivalent to human skin, and the impedance was measured using an impedance measurement device Autolab (manufactured by Metrohm Autolab). The measurement conditions were a measurement frequency of 1 Hz, 10 Hz, or 1000 Hz and an effective voltage of 10 mV.

[0119] As the measurement level,

[0120] The working electrode and the counter electrode are both at the level of the biological signal sensing electrode of this embodiment produced above.

[0121] The working electrode and the counter electrode are both at the level of the biological signal sensing electrode (MXene film only) of Comparative Example 1, and

[0122] The working electrode and the counter electrode were all at the level of the commercially available biological electrode of Comparative Example 2, a total of three levels. This time, the measurement was performed using two electrodes, so no reference electrode was used. The following Table 1 shows the measurement results.

[0123] [Table 1]

[0124]

[0125] According to the results of Table 1 above, the impedance of the biological signal sensing electrode sample (MXene film + porous membrane) of this embodiment is equivalent to that of the MXene film alone at any frequency, and even if a porous membrane is formed, the impedance increase is small. It can also be seen that the impedance of the biological signal sensing electrode sample of the present invention is lower than the impedance of the commercially available Ag / AgCl gel electrode, and as a biological signal electrode, the resistance is sufficiently low. In addition, in the biological signal sensing electrode of the present invention, the MXene film is in direct contact with the porous membrane and has good adhesion. Therefore, there is no need to provide an adhesive layer between the MXene film and the porous membrane. As a result, the number of layers is suppressed, and a low and stable impedance is exhibited. In addition, according to this embodiment, the MXene film does not contact the subject, so the peeling of MXene can be suppressed, and the measurement can be performed stably over a long period of time. In addition, it is not a material that contains moisture, etc., so the discomfort of wearing can be reduced.

[0126] Industrial applicability

[0127] The biological signal sensing electrode of the present invention can be preferably used in a device for extracting and measuring biological signals such as electromyographic signals and electrocardiographic signals, for example.

[0128] This application claims priority based on Japanese Patent Application No. 2020-165302, which is incorporated herein by reference.

[0129] Description of Reference Numerals

[0130] 1a, 1b layer main body (M m X n layer);

[0131] 3a, 5a, 3b, 5b modified or terminal T;

[0132] 7a, 7b MXene layers;

[0133] 10, 10a, 10b MXene (layered materials);

[0134] 21 conductive film;

[0135] 22 porous membrane;

[0136] 23. a substrate formed of a conductive material;

[0137] 24 Previous snap-on electrodes;

[0138] 25 Insulating film;

[0139] 26 holes;

[0140] 30 biological signal sensing electrodes;

[0141] 31. the buckling portion of the electrode;

[0142] 32 leads.

Claims

1. A biological signal sensing electrode, wherein: The biological signal sensing electrode comprises a stack of a conductive film and a porous film, wherein the conductive film contains particles of a layered material, and the layered material comprises one or more layers. The layer includes a layer body and a modification or termination T present on the surface of the layer body, 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. The layer body is represented by the following formula: M m X n Wherein, M is at least one metal of Groups 3, 4, 5, 6, or 7, X is a carbon atom, a nitrogen atom or a combination thereof, n is 1 or more and 4 or less, m is greater than n and less than 5, The porous membrane comprises a hydrophilic polymer, The porous membrane is provided on the surface in contact with the subject.

2. The biological signal sensing electrode according to claim 1, wherein: The conductive film includes a polymer.

3. The biological signal sensing electrode according to claim 1 or 2, wherein: The average pore diameter of the porous membrane is 1 nm or more and 1 μm or less.

4. The biological signal sensing electrode according to any one of claims 1 to 3, wherein The porous film has a thickness of 0.1 μm or more and 300 μm or less.

5. The biological signal sensing electrode according to any one of claims 1 to 4, wherein: The conductive film has a thickness of 0.5 μm or more and 20 μm or less.

Images