Biosignal sensing electrodes

Abstract

The present invention provides a biological signal sensing electrode capable of sensitively detecting biological information while exhibiting high electrical conductivity without discomfort to the subject. The biological signal sensing electrode comprises, on its contact surface with the subject, a conductive composite material comprising at least particles of a layered material and a polymer. The layered material comprises one or more layers, each layer comprising a layer body represented by Ti3C2 and modifications or terminations 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 polymer is a hydrophilic polymer having polar groups, wherein the polar groups are groups that form hydrogen bonds with the modifications or terminations T of the layer.

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 for measurement can be cited. In recent years, as the above-mentioned electrode, a dry electrode that does not require gel or adhesive and has a very low possibility of causing an allergic reaction on the patient's skin has been proposed. For example, in Patent Document 1, as a device capable of non-invasively obtaining an electrocardiogram signal and extracting the electrocardiogram signals of the fetus and the mother from the electrocardiogram signal, a measuring device has been disclosed, which is embedded in a wearable device worn around the body of a pregnant subject, or includes a plurality of mounted button-type electrodes.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: U.S. Patent No. 9,579,055 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The dry electrode of Patent Document 1, mentioned above, has a protrusion to ensure good contact between the electrode and the skin. However, this protrusion causes significant discomfort to the patient. Furthermore, dry electrodes are required to exhibit high conductivity and sufficiently high sensitivity in a dry state. The present invention has been developed in light of the above circumstances, and its object is to provide a biological signal sensing electrode that can exhibit high conductivity and detect biological information with high sensitivity without causing discomfort to the subject.

[0008] Means for solving problems

[0009] According to one aspect of the present invention, there is provided a biological signal sensing electrode.

[0010] The surface in contact with the subject comprises at least a conductive composite material comprising particles of a layered material and a polymer, wherein the layered material comprises one or more layers.

[0011] The layer comprises a layer body represented by Ti3C2 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,

[0012] The polymer is a hydrophilic polymer having a polar group, and the polar group is a group that forms a hydrogen bond with the modification or terminal T of the layer.

[0013] Effects of the Invention

[0014] According to the present invention, a biological signal sensing electrode can be provided, which has a conductive composite material comprising at least particles of a predetermined layered material (also referred to as "MXene" in this specification) and a polymer on its contact surface with the subject, wherein the polymer is a hydrophilic polymer having a polar group, and the polar group is a group that forms a hydrogen bond with the modification or terminal T of the layer. Thus, the electrode can exhibit high conductivity and detect biological information with good sensitivity without the subject feeling any discomfort. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic cross-sectional view showing a conductive composite material according to one embodiment of the present invention.

[0016] Figure 2 This is a schematic cross-sectional view showing a MXene as a layered material that can be used in the conductive composite material according to one embodiment of the present invention.

[0017] Figure 3 This is a schematic perspective view showing a biological signal sensing electrode according to one embodiment of the present invention.

[0018] Figure 4 This is a schematic cross-sectional view showing a biological signal sensing electrode according to one embodiment of the present invention.

[0019] Figure 5 This is a schematic perspective view showing a biological signal sensing electrode according to another embodiment of the present invention.

[0020] Figure 6 This is a schematic cross-sectional view showing a biological signal sensing electrode according to another embodiment of the present invention.

[0021] Figure 7 This is a schematic diagram showing a usage example of a biological signal sensing electrode according to one embodiment of the present invention. DETAILED DESCRIPTION

[0022] Hereinafter, a biological signal sensing electrode according to an embodiment of the present invention and a conductive composite material used in the electrode will be described in detail; however, the present invention is not limited to this embodiment.

[0023] (Conductive composite materials)

[0024] Reference Figure 1The conductive composite material 20 used in the biological signal sensing electrode of this embodiment includes particles 10 of a predetermined layered material and a polymer 11. The polymer 11 is a hydrophilic polymer having a polar group, and the polar group is a group that forms a hydrogen bond with the modification or terminal T of the layer.

[0025] The particles of the predetermined layered material of this embodiment are defined as follows.

[0026] The present invention is a particle of a layered material comprising one or more layers, wherein the layer is a layered material (which can be understood as a layered compound and also represented by "Ti3C2T"). The layered material comprises a layer body represented by Ti3C2 (the layer body may have a lattice in which each C is located in an octahedral array of Ti) and a modified or terminated 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, at least one of the two surfaces of the layer body facing each other). x ", x is an arbitrary number, and s or z is sometimes used instead of x in the past). Hereinafter, the layered material is sometimes referred to as "Ti3C2T x " or MXene (particles).

[0027] This MXene can be synthesized by selectively etching (removing and, if appropriate, layer-separating) A atoms such as Al, Si, Sn, and In (and, if appropriate, a portion of the Ti atoms) from the MAX phase. The MAX phase has a crystal structure represented by Ti3AC2, in which a layer containing A atoms is located between two layers represented by Ti3C2 (which may have a lattice in which each C atom is located within an octahedral array of Ti). In the case of Ti3AC2, where the number of Ti atoms = the number of carbon atoms + 1, the MAX phase has a repeating unit in which a layer of carbon atoms is arranged between each of the three Ti atom layers (sometimes collectively referred to as a "Ti3C2 layer"), and a layer of A atoms ("A atom layer") is arranged as the layer immediately following the third Ti atom layer. However, this is not limiting. By selectively etching (removing and optionally layer-separating) A atoms (and optionally a portion of the Ti atoms) from the MAX phase, the A atom layer (and optionally a portion of the Ti atoms) is removed, and the hydroxyl groups, fluorine atoms, chlorine atoms, oxygen atoms, hydrogen atoms, etc. present in the etching solution (usually an aqueous solution containing fluoric acid is used, but not limited to this) modify the surface of the exposed Ti3C2 layer, thereby terminating the surface.

[0028] In the above-mentioned etching, a fluorine resin container is used and an acid such as HF, HCl, HBr, HI, sulfuric acid, phosphoric acid, and nitric acid is used for etching. For example, a method using a mixed solution of lithium fluoride and hydrochloric acid, a method using hydrofluoric acid, etc. can be used. In the above-mentioned etching process, the following process can be cited, that is, stirring is performed for about 5 hours or more and 48 hours or less at a temperature above room temperature and below 40 degrees. Then, as a cleaning process, the liquid after the etching process is transferred to a centrifugal sedimentation tube, pure water is added and stirred, and the supernatant and the precipitate are separated by a centrifugal separator, the supernatant is discarded, and the operation is repeated for more than 5 times and less than 20 times. Thereafter, a layering process is performed for a predetermined time using, for example, a mechanical oscillator, a vortex mixer, a homogenizer, an ultrasonic bath, etc. Then, the supernatant and the precipitate are separated by a centrifugal separator, and the recovered supernatant can be used as a monolayered Ti3AC2(MXene) dispersion.

[0029] It should be noted that in the present invention, the 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, 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 paste (and the conductive film obtained from the paste).

[0030] like Figure 2 As schematically shown in FIG, the MXene (particle) 10 synthesized in this way can be a layered material comprising one or more MXene layers 7a, 7b (as an example of MXene (particle) 10, in Figure 2 (a) shows one layer of MXene10a. Figure 2 (b) shows two layers of MXene 10b, but is not limited to these examples). More specifically, the MXene layers 7a and 7b have a layer body (Ti3C2 layer) 1a and 1b represented by Ti3C2 and modifications or terminations T3a, 5a, 3b, and 5b present on the surface of the layer body 1a and 1b (more specifically, at least one of the two surfaces facing each other in each layer). Therefore, the MXene layers 7a and 7b are also expressed as "Ti3C2Ti x ”, x is an arbitrary number. MXene10 can be a material in which each MXene layer is separated and exists as one layer ( Figure 2 The single-layer structure shown in (a), that is, the 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(b) The multilayer structure shown, that is, the so-called multilayer MXene10b), can also be a mixture thereof. MXene10 can be a particle (also referred to as a powder or flake) that is an aggregate containing a single layer of MXene10a and / or a multilayer of MXene10b. In this embodiment, MXene10 is preferably a particle (also referred to as a nanosheet) that is mostly composed of a single layer of MXene10a. In the case of a multilayer MXene, the two adjacent MXene layers (for example, 7a and 7b) are not necessarily completely separated, and can also be partially in contact.

[0031] Although not limiting 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 (may vary mainly depending on the number of Ti atomic layers contained in each layer), and the maximum dimension in the 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 MXene is a stack (multilayer MXene), for each stack, the interlayer distance (or gap size, Figure 2 (b) (represented by Δd) is, for example, 0.8 nm or more and 10 nm or less, particularly 0.8 nm or more and 5 nm or less, more particularly about 1 nm, the total number of layers may be 2 or more, for example, 50 or more and 100,000 or less, particularly 1,000 or more and 20,000 or less, the thickness in the stacking direction is, for example, 0.1 μm or more and 200 μm or less, particularly 1 μm or more and 40 μm or less, and the maximum dimension in a plane perpendicular to the stacking direction (two-dimensional sheet surface) is, for example, 0.1 μm or more and 100 μm or less, particularly 1 μm or more and 20 μm or less. It should be noted that these dimensions can be obtained as a number average size (for example, a number average of at least 40) based on a scanning electron microscope (SEM), a transmission electron microscope (TEM) photograph, or an atomic force microscope (AFM) photograph, or as a distance in actual space calculated from the position in the reciprocal lattice space of the (002) plane measured by an X-ray diffraction (XRD) method.

[0032] In this embodiment, the polymer mixed with the particles of the layered material is a hydrophilic polymer having a polar group, and the polar group is a group that forms a hydrogen bond with the modification or terminal T of the layer.

[0033] As the polymer, it is preferred to use 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. Since these polymers are rich in -SO3-, -CONH-, -COO-, -OH, and -NH- in their molecular chains, they are similar to Ti3C2T x The high affinity of the conductive composite material makes it easy to form hydrogen bonds, for example. For these reasons, the disorder of the obtained conductive composite material is suppressed and the conductivity can be improved. As a result, a dry electrode with high sensitivity can be provided.

[0034] Among them, more preferably, one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol and sodium alginate are used. This is because these polymers have many functional groups capable of forming hydrogen bonds, which are particularly helpful for bonding with Ti3C2T x The hydrogen bonding functional groups of Ti3C2T x The formation of hydrogen bonds can provide highly sensitive electrodes. In particular, water-soluble polyurethane is rich in urethane bonds, which have both hydrogen bond donor and hydrogen bond acceptor properties. The polyvinyl alcohol is rich in OH groups that exhibit hydrogen bond donor properties. In addition, the sodium alginate molecules are highly planar and can be bonded to MXene, especially Ti3C2T x The number of functional groups forming hydrogen bonds is substantially large.

[0035] As the above polymer, a polymer having a urethane bond having both hydrogen bond donor and hydrogen bond acceptor properties is preferred. From this viewpoint, the above water-soluble polyurethane is particularly preferred. The polymer having a urethane bond is helpful for bonding with Ti3C2T x Specifically, in Ti3C2T x When the above modification or terminal T in Ti3C2T has at least one selected from the group consisting of fluorine atoms, chlorine atoms and oxygen atoms as a hydrogen acceptor, the H of the NH of the carbamate bond can act as a hydrogen donor to form a hydrogen bond. x When the above modification or the terminal T has a hydroxyl group and / or a hydrogen atom as a hydrogen donor, the O of the CO of the urethane bond can function as a hydrogen acceptor to form a hydrogen bond.

[0036] The ratio of the particles of the layered material, i.e. Ti3C2T xThe proportion of the particles of the layered material is preferably 52% by mass or more and 83% by mass or less. By setting the proportion of the particles of the layered material to 52% by mass or more, biological signals can be detected with good sensitivity. The proportion 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 above proportion is preferably 83% by mass or less, more preferably 75% by mass or less. The proportion of the particles of the layered material refers to the proportion occupied in the conductive composite material. The conductive composite material of the present invention sometimes also contains additives such as colorants and antioxidants. In this case, the proportion of the particles of the layered material refers to the proportion occupied in the conductive composite material including the above additives.

[0037] As other preferred embodiments, for the conductive composite material having a higher concentration of the particles of the above-mentioned layered material, the ratio of the particles of the above-mentioned layered material can be cited as greater than 83 mass % and as less than 94 mass %. If the conductive composite material having the above-mentioned improved concentration is used, even when the surface of the subject is difficult to detect biological signals due to the hardness of the cuticle, it is possible to measure the sample without removing the pre-treatments such as the above-mentioned cuticle in advance. From the viewpoint of detecting biological signals with higher sensitivity, the ratio of the particles of the above-mentioned layered material is more preferably set to more than 85 mass %, more preferably more than 89 mass %. It should be noted that, even in this case, from the viewpoint of ensuring the flexibility of the composite material, the ratio of the particles of the above-mentioned layered material is also preferably less than 94 mass %, more preferably less than 92 mass %.

[0038] As described later, two or more composite materials having different ratios of the layered material particles may be provided on one electrode. In this case, at least a portion of the conductive composite material satisfies the ratio of the layered material particles.

[0039] The conductive composite material in the biological signal sensing electrode of this embodiment is not limited to a specific form as long as it is present at least on the contact surface of the electrode with the subject. Examples of conductive composite materials include solid materials and flexible soft materials. When the conductive composite material has a sheet-like form, its thickness can be measured, for example, by measurement using a micrometer or cross-sectional observation using a scanning electron microscope (SEM), a microscope, or a laser microscope.

[0040] As shown in the examples described below, the conductive composite material of this embodiment preferably maintains a conductivity of 500 S / cm or more when it is in the form of a sheet with a film thickness of 5 μm. The above conductivity can be maintained at a conductivity of preferably 1000 S / cm or more, more preferably 1800 S / cm or more, further 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 for example, it can be 20,000 S / cm or less. The conductivity can be calculated as follows. That is, the surface resistivity is measured using the four-probe method, and the value obtained by multiplying the thickness [cm] by the surface resistivity [Ω / □] is the volume resistivity [Ω.cm], and the reciprocal of the volume resistivity [S / cm] can be calculated.

[0041] (Biological signal sensing electrode)

[0042] The biological signal sensing electrode of this embodiment is not limited to a specific form as long as it includes the conductive composite material at least on the surface in contact with the subject. As mentioned above, the conductive composite material can be a solid material or a flexible soft material.

[0043] As one embodiment of the biological signal sensing electrode, Figure 3 Schematic perspective view of a snap-type electrode is shown in FIG. Figure 3 FIG. 3 is a diagram showing a lead wire 32A connected to a buckle portion 31A of an electrode 30A having a convex curved surface in contact with a subject. Figure 3 A cross-sectional view of the electrode 30A is shown in FIG. Figure 4 (a) Figure 4 (b) and Figure 4 (c). In addition, as another embodiment of the biological signal sensing electrode, Figure 5 3 is a schematic perspective view of a snap-fit type electrode in which a lead wire 32B is connected to a snap-fit portion 31B of an electrode 30B whose contact surface with the subject is a flat surface. Figure 5 A cross-sectional view of the electrode 30B is shown in FIG. Figure 6 (a) Figure 6 (b) and Figure 6 (c) in.

[0044] above Figure 3 and Figure 5 The embodiment has the above-mentioned conductive composite material and does not have protrusions like the electrode of Patent Document 1. Figure 3 and Figure 5 The difference between the embodiments is whether the contact surface with the subject is a curved surface or a flat surface. Figure 4 (a) with Figure 6 (a) Figure 4 (b) with Figure 6 (b) Figure 4 (c) with Figure 6 (c) Each has the same structure.

[0045] Figure 4 (a) and Figure 6 In (a), the conductive composite materials 21A and 21B are formed on the substrates 23A and 23B formed of the conductive material. By forming the conductive composite materials 21A and 21B as described above, a highly sensitive biological signal sensing electrode can be provided. In particular, by forming the conductive composite materials 21A and 21B as described above, a highly sensitive biological signal sensing electrode can be provided. Figure 4 As shown in (a), the contact surface with the subject is curved, which can reduce discomfort when wearing it.

[0046] As the conductive material constituting the substrates 23A and 23B, at least one material selected from the group consisting of metal materials such as gold, silver, copper, platinum, nickel, titanium, tin, iron, zinc, magnesium, aluminum, tungsten, molybdenum, and conductive polymers can be cited. Figure 4 (a) and Figure 6 The conductive composite materials 21A and 21B in (a) may be, for example, those containing particles of the aforementioned layered material in a ratio of 52% to 83% by mass. This allows for the realization of electrodes that are both highly conductive and flexible, further reducing discomfort when worn.

[0047] Figure 4 (b) and Figure 6 In (b), the conductive composite materials 21A and 21B are formed on the substrates 23A and 23B respectively. In addition, Ti3C2T2 is formed on the contact surface with the subject. x According to this structure, since Ti3C2T is formed on the contact surface with the subject, x The high concentration of conductive composite materials 22A and 22B provides a more sensitive biological signal sensing electrode. This allows measurements to be performed even in cases where biological signals are difficult to detect from the subject's surface, such as in patients with thick stratum corneum, without requiring pretreatment associated with inflammation, such as removing the stratum corneum.

[0048] above Figure 4 (b) and Figure 6(b) It corresponds to a biological signal sensing electrode in which the proportion of the particles of the layered material is higher in the portion in contact with the subject than in the portion not in contact with the subject. In particular, it corresponds to a biological signal sensing electrode in which the proportion of the particles of the layered material is higher on the side closer to the portion in contact with the subject, for example, higher in the region from the contact surface to about 1 / 3 of the thickness, compared to the position of 1 / 2 of the thickness of the conductive composite material in the cross section of the electrode perpendicular to the contact surface with the subject. As described above Figure 4 (b) and Figure 6 As shown in (b), two or more conductive composite materials having different particle ratios of the layered materials may be stacked in a single electrode. Alternatively, the conductive composite material may be provided so that the particle ratio of the layered materials increases in a stepwise or gradient manner from the substrates 23A and 23B formed of the conductive material to the surface in contact with the subject.

[0049] As examples of ways in which the proportion of particles of the above-mentioned layered material is higher in the contact portion with the subject than in the non-contact portion with the subject, there can be cited ways in which the proportion of particles of the above-mentioned layered material is greater than 83 mass % and less than 94 mass % in the contact portion with the subject, and is greater than 52 mass % and less than 83 mass % at a position of 1 / 2 of the thickness of the conductive composite material in a cross-section of the electrode perpendicular to the contact surface with the subject.

[0050] Figure 4 (c) and Figure 6 (c) shows that the contact surfaces of conventional snap-fit electrodes 24A and 24B made of conductive material with the subject are provided with Ti3C2T x Electrodes 22A and 22B contain a high concentration of conductive composite material. The conductive material constituting the snap-on electrodes 24A and 24B can be the same as that used for the substrates 23A and 23B formed from the aforementioned conductive material. This configuration utilizes a versatile extraction electrode, enabling the provision of a low-cost, highly sensitive biological signal sensing electrode.

[0051] Although not shown, Figure 4 (a) and Figure 6 The conductive composite materials 21A and 21B in (a) can also be replaced by Ti3C2T x The conductive composite materials 22A and 22B have high concentrations.

[0052] If Ti3C2T is used as described above x The conductive composite material can reduce the impedance of the interface between the skin and the electrode compared to conventional electrodes, and can detect the necessary signals even without protrusions. Figure 7As shown, an operation of attaching a plurality of biological signal sensing electrodes 30 of this embodiment to the skin of a subject's forearm to measure, for example, myoelectricity can be exemplified. Figure 7 In the figure, 32 is a lead, 33 is a cable, and 34 is an analysis system.

[0053] There are no particular limitations on the method for producing an electrode comprising the conductive composite material of this embodiment using the MXene produced as described above. When the conductive composite material of this embodiment has a sheet-like form, for example, the layered material can be mixed with a polymer as exemplified below to form a coating film.

[0054] 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. Depending on the circumstances, other liquid substances may be included in addition to water in a smaller amount (e.g., 30% by mass or less, preferably 20% by mass or less, based on the total weight).

[0055] The stirring of the MXene particles and the polymer can be performed 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.

[0056] The slurry of the mixture of the MXene particles and the polymer is applied to a substrate (e.g., a substrate), and the coating method is not limited. For example, a method of spray coating using a nozzle such as a single-fluid nozzle, a two-fluid nozzle, an airbrush, a slit coating using a benchtop coater, a comma-shaped blade coater, or a rod coater, screen printing, metal mask printing, and a coating method based on spin coating, dipping, or dripping can be cited. As mentioned above, the substrate can be appropriately formed of a metal material, resin, or the like suitable for a biological signal sensing electrode.

[0057] The coating and drying can be repeated as needed until a film of desired thickness is obtained. Drying and curing can be performed, for example, in an atmospheric oven or a vacuum oven at a temperature of 400 degrees or less.

[0058] While one embodiment of the present invention has been described in detail above, various modifications are possible. It should be noted that the present invention's biological signal sensing electrode can also be manufactured using methods different from those of the above-described embodiment.

[0059] Example

[0060] [Example 1]

[0061] ■Preparation of MAX particles

[0062] TiC powder, Ti powder, and Al powder (all manufactured by Kojundo Chemical Laboratory Co., Ltd.) were placed in a ball mill containing zirconia beads at a molar ratio of 2:1:1 and mixed for 24 hours. The resulting mixed powder was calcined at 1350°C for 2 hours under an Ar atmosphere. The resulting calcined body (MAX block) was crushed with an end mill until the maximum size was 40 μm or less. This yielded Ti3AlC2 particles, which are MAX particles.

[0063] Preparation of MXene dispersion

[0064] Weigh 1g of Ti3AlC2 particles (powder) prepared by the above method, use a fluorine resin container, add it to 10mL of 9mol / L hydrochloric acid together with 1g of LiF and stir it with a stirrer at 35°C for 24 hours to perform etching treatment to obtain a solid-liquid mixture (suspension) containing solid components from Ti3AlC2 powder. The solid-liquid mixture (suspension) after etching is transferred to a centrifugal sedimentation tube, pure water is added and stirred, and the supernatant is separated from the precipitate by a centrifugal separator, and the supernatant is discarded. Repeat this operation 10 times for cleaning. Thereafter, a mechanical oscillator is used to treat it for a predetermined time and perform layering treatment. Thereafter, the supernatant is recovered by centrifugation and used as a MXene dispersion.

[0065] The above MXene dispersion, pure water and the polymers shown in Table 1 were mixed to obtain Ti3C2T x A MXene / polymer composite material with a ratio (after film formation and drying) of 52% to 83% by mass was stirred with a propeller stirrer and the resulting slurry was spray-coated onto a PET film using a two-fluid nozzle. This spray irradiation and drying in a dryer were repeated 15 times until the MXene / polymer composite film reached a thickness of 5 μm. After coating, the film was dried in an atmospheric oven at 80°C for approximately 30 minutes to obtain a MXene / polymer composite film.

[0066] ■Determination of electrical conductivity of MXene / polymer composite membranes

[0067] The conductivity of the MXene / polymer composite film was determined. The conductivity was determined by measuring the surface resistivity (Ω) and thickness (μm) at three locations for one sample. The value obtained by multiplying the thickness [cm] by the surface resistivity [Ω / □] was the volume resistivity [Ω.cm], and the conductivity [S / cm] as the reciprocal thereof was determined. The arithmetic mean of the three conductivities thus obtained was adopted. The surface resistivity was determined using a 4-probe method. When measuring the surface resistivity, a low resistivity meter (Mitsubishi Chemical Analytech Co., Ltd., Loresta AX MCP-T370) was used. In addition, a micrometer (Mitsutoyo Co., Ltd., MDH-25MB) was used when measuring the thickness. The results are shown in Table 1. It should be noted that the measurement accuracy of the conductivity is 2 significant figures (the same applies to Table 2 below). In Table 1, the case where the electrical conductivity was 500 S / cm or more was judged as good (○), and the case where the electrical conductivity was less than 500 S / cm was judged as poor (×).

[0068] [Table 1]

[0069] Types of MXene Conductivity [S / cm] determination <![CDATA[Ti3C2T x ]]> 4000 ○ <![CDATA[Ti2CT x ]]> 100 × <![CDATA[Cr2TiC2T x ]]> 200 × <![CDATA[Cr2VC2T x ]]> 180 ×

[0070] According to the results in Table 1, as MXene mixed with polymer, Ti2CT x 、Cr2TiC2T x and Cr2VC2T x Compared with Ti3C2T x It shows a remarkably high electrical conductivity. By using the highly conductive Ti3C2T x , an electrode with high sensitivity can be obtained.

[0071] [Example 2]

[0072] In addition to setting the type of MXene to Ti3C2T x MXene / polymer composite films were prepared in the same manner as in Example 1, except that the polymers listed in Table 2 were used in addition to the water-soluble polyurethane. The electrical conductivity was measured. The results are shown in Table 2. In Table 2, electrical conductivities of 2900 S / cm or higher are considered very good (◎), electrical conductivities of less than 2900 S / cm and 500 S / cm or higher are considered good (○), and electrical conductivities of less than 500 S / cm are considered poor (×).

[0073] [Table 2]

[0074] Types of polymers Conductivity [S / cm] determination Organic polyurethane 150 × Water-soluble polyurethane 4000 ◎ polyvinyl alcohol 3000 ◎ Sodium alginate 3500 ◎ Acrylic acid water-soluble polymer 1000 ○ polyacrylamide 950 ○ Polyaniline sulfonic acid 900 ○ nylon 700 ○ paraffin 100 ×

[0075] The results in Table 2 show that the conductivity of the composite material is low when organic polyurethane and paraffin are used as polymers. The reasons for this are as follows. First, paraffin (a type of hydrocarbon compound, a general term for alkanes with 20 or more carbon atoms) has low polarity and is therefore x The low affinity of the composite material makes it more complex, which is considered to be the reason for the low conductivity. In addition, the organic polyurethane and the small amount of residual organic solvent and Ti3C2T x The affinity of the prepared composite material is low, and the disorderliness thereof becomes high, which is considered to be the reason for the low electrical conductivity.

[0076] In contrast, water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic acid water-soluble polymers, polyacrylamide, polyaniline sulfonic acid and nylon have good affinity with Ti3C2T x The composite material has high conductivity and can realize a dry electrode with high sensitivity. It can be considered that the polymer constituting the composite material judged as ○ and ◎ is rich in -SO3-, -CONH-, -COO-, -OH, and -NH- in the molecular chain as mentioned above, and is easy to react with Ti3C2T x Among them, water-soluble polyurethane, polyvinyl alcohol and sodium alginate form hydrogen bonds with Ti3C2T x The composite materials showed sufficiently high conductivity of 3000 S / cm or more. The reason for this is that the polymers constituting the composite materials judged as ◎ have a large amount of x hydrogen bonding functional groups.

[0077] The most preferred is Ti3C2T x Composite materials with water-soluble polyurethane. It can be considered that, as mentioned above, water-soluble polyurethane has more x The composite material has a functional group capable of hydrogen bonding, and unlike the above-mentioned organic polyurethane, it has good affinity with a subject containing a large amount of water. When the water-soluble polyurethane is present on the outermost surface of the composite material, it is easy to detect biological signals when in contact with the subject.

[0078] Industrial applicability

[0079] The biological signal sensing electrode of the present invention can be preferably used as the following electrodes, that is, it can detect biological information such as electrical signals from muscles and heart with good sensitivity without the subject feeling discomfort, for example, for measuring EEG (brain waves), ECG (electrocardiogram), EMG (electromyogram), and EIT (electrical impedance tomography).

[0080] This application claims priority based on Japanese Patent Application No. 2020-131864, which is incorporated herein by reference.

[0081] Description of Reference Numerals

[0082] 1a, 1b layer main body (M m X n layer), 3a, 5a, 3b, 5b modified or terminated T, 7a, 7b MXene layer, 10, 10a, 10b MXene (layered material), 11 polymer, 20, 21A, 21B conductive composite material, 22A, 22B high-concentration MXene conductive composite material, 23A, 23B substrate formed of a conductive material, 24A, 24B conventional snap-fit electrode, 30, 30A, 30B biological signal sensing electrode, 31A, 31B snap-fit portion of electrode, 32, 32A, 32B lead wire, 33 cable, 34 analysis system.

Claims

1. A biological signal sensing electrode, The surface of the device in contact with the subject comprises at least a conductive composite material comprising particles of a layered material and a polymer, wherein the layered material comprises one or more layers. The layer comprises a layer body represented by Ti3C2 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 polymer is a hydrophilic polymer having a polar group, wherein the polar group is a group that forms a hydrogen bond with the modification or terminal T of the layer, The polymer is one or more polymers selected from the group consisting of water-soluble polyurethane, polyvinyl alcohol, sodium alginate, acrylic water-soluble polymer, polyacrylamide, polyaniline sulfonic acid, and nylon.

2. The biological signal sensing electrode according to claim 1, The proportion of the layered material particles is higher on the side closer to the contact portion with the subject than at a position half the thickness of the conductive composite material in a cross section of the electrode perpendicular to the contact surface with the subject.

3. The biological signal sensing electrode according to claim 1, wherein The ratio of the particles of the layered material is 52% by mass or more and 83% by mass or less.

4. The biological signal sensing electrode according to claim 1, wherein The proportion of the particles of the layered material is greater than 83% by mass and not more than 94% by mass.

5. The biological signal sensing electrode according to claim 1, The proportion of particles of the layered material is greater than 83 mass % and less than 94 mass % in the contact portion with the subject, and is greater than 52 mass % and less than 83 mass % at a position 1 / 2 of the thickness of the conductive composite material in a cross-section of the electrode perpendicular to the contact surface with the subject.

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