Biosignal Sensing Electrodes

Abstract

A biosignal sensing electrode comprising: a substrate and a conductive film disposed thereon; the conductive film comprising particles of a layered material comprising one or more layers; the layers comprising a material having a formula M m X n 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 and oriented parallel to the surface of the base material; a protective material containing a polymer having, as functional groups, C=O and at least one of OH and NH covers at least an end of the conductive film, the functional groups are bonded to particles of the layered material, and at least a portion of the second surface of the conductive film is exposed from the protective material.

Description

[Technical field]

[0001] The present invention relates to a biosignal sensing electrode. [Background technology]

[0002] In recent years, MXene has been attracting attention as a new material having electrical conductivity. MXene is a type of so-called two-dimensional material, and as described below, it is a layered material having the form of one or more layers. In general, MXene has the form of particles of such layered material (which may include powder, flakes, nanosheets, etc.).

[0003] Currently, various researches are being conducted on the application of MXene to various electric devices. It has been reported that MXene, in the form of a conductive film (dry film), shows high sensitivity when used as a biosignal sensing electrode for electroencephalogram sensors, electromyogram sensors, electrocardiogram sensors, etc. (see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Nicolette Driscoll, et al., "Two-Dimensional Ti3C2 MXene for High Resolution Neural Interfaces", ACS Nano, 2018, Vol. 12, Issue 10, pp. 10419-10429 [Non-Patent Document 2] Fanjie Xia, et al., "Ambient oxidation of Ti3C2 MXene initialized by atomic defects", Nanoscale, 2019, Vol. 11, Issue 48, pp. 23330-23337 [Non-Patent Document 3] Chien-Wei Wu, et al., "Excellent oxidation resistive MXene aqueous ink for micro-supercapacitor application", Energy Storage Materials, 2020, Vol. 25, pp. 563-571 [Non-Patent Document 4] Varun Natu et ai., "Edge Capping of 2D-MXene Sheets with Polyanionic Salts to Mitigate Oxidation in Aqueous Colloidal Suspensions", Angewandte Chemie International Edition, 2019, Volume 58, Issue 36, pp. 12655-12660 Summary of the Invention [Problem to be solved by the invention]

[0005] It has been reported that MXene is easily oxidized, particularly in solvents containing water (see Non-Patent Document 2). It is also known that MXene is oxidized over time in air (which usually contains water and oxygen).

[0006] Therefore, when MXene is used in the form of a conductive film (dry film) as a biosignal sensing electrode, the MXene in the conductive film is oxidized over time when it comes into contact with sweat or blood (which usually contain water) from a living body that may be the subject, or when it is exposed to air, and as a result, the sensing ability of the conductive film deteriorates over time.

[0007] Conventionally, methods proposed for preventing oxidation of MXene include mixing an aqueous dispersion of MXene particles with an aqueous sodium ascorbate solution (see Non-Patent Document 3) and adding a polyanion salt (specifically, a salt of polyphosphoric acid, polysilicic acid, or polyboric acid) to an aqueous colloidal suspension of MXene (see Non-Patent Document 4). However, these methods are methods for preventing oxidation of MXene when the MXene particles form an aqueous dispersion / suspension, and do not directly address the case where the MXene particles form a conductive film (dry film). To form a conductive film using MXene particles that have been treated for oxidation prevention using these methods, an additional process of separating the MXene particles from the liquid phase and forming a film is required.

[0008] An object of the present invention is to provide a biosignal sensing electrode that uses a conductive film containing MXene particles, and that effectively reduces deterioration of sensing ability over time. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a biosignal sensing electrode, comprising: A substrate; a conductive film disposed on the substrate, the conductive film having a first surface facing the substrate and a second surface facing away from the substrate; Including, the conductive film comprises particles of layered material comprising one or more layers; The layer comprises a compound having the following formula: M m X n (wherein M is at least one Group 3, 4, 5, 6, or 7 metal; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 to 4, m is greater than n and less than or equal to 5) 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, and oriented parallel to the surface of the base material, A biosignal sensing electrode is provided, in which a protective material including a polymer having C=O and at least one of OH and NH as functional groups covers at least an end of the conductive film, the functional groups are bonded to particles of the layered material, and at least a portion of the second surface of the conductive film is exposed from the protective material.

[0010] In one embodiment of the invention, the polymer may permeate into the conductive membrane.

[0011] In one embodiment of the present invention, the polymer may include at least one selected from the group consisting of polyvinyl alcohol, polyisocyanate-crosslinked acrylic resin, epoxy-crosslinked acrylic resin, and polyamideimide.

[0012] In one embodiment of the present invention, the protective material may further cover an outer circumferential region of the second surface of the conductive film.

[0013] In one aspect of the present invention, the biosignal sensing electrode may further include a cover disposed on the second surface of the conductive film, with a portion of the second surface being exposed from the cover.

[0014] In one embodiment of the present invention, the M m X n However, Ti2C, Ti3C2, Ti3(CN), (Cr2Ti)C2, (Mo2Ti)C2, (Mo2Ti2)C3, and (Mo 2.7 V 1.3 ) C3. Effect of the Invention

[0015] According to the present invention, in a biosignal sensing electrode using a conductive film containing particles of a specified layered material (also referred to as "MXene" in this specification), at least the ends of the conductive film are covered with a protective material containing a polymer having C=O and at least one of OH and NH as functional groups, and the functional groups are bonded to the MXene particles, thereby providing a biosignal sensing electrode in which deterioration of sensing ability over time is effectively reduced. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram illustrating a biosignal sensing electrode in one embodiment of the present invention, where (a) is a schematic cross-sectional view of the biosignal sensing electrode, and (b) is a schematic top view of (a). [Diagram 2] FIG. 1(a) is a schematic enlarged cross-sectional view of the area surrounded by the dashed line in FIG. 1(a), (b) is a schematic cross-sectional view of MXene particles and a polymer (derived from the protective material) in a conductive film, and (c) is a schematic oblique view of MXene particles in a conductive film. [Diagram 3] FIG. 1 is a schematic cross-sectional view showing MXene particles, a layered material that can be used for a conductive film in one embodiment of the present invention, where (a) shows a single-layer MXene particle and (b) shows a multi-layer (exemplarily two-layer) MXene particle. [Figure 4] 2 is a schematic cross-sectional view showing a modified example of the biosignal sensing electrode of FIG. 1. [Diagram 5] 1. FIG. 4 is a schematic cross-sectional view showing another modified example of the biosignal sensing electrode of FIG. [Figure 6] FIG. 11 is a diagram illustrating a biosignal sensing electrode in another embodiment of the present invention, where (a) is a schematic cross-sectional view of the biosignal sensing electrode, and (b) is a schematic bottom view of (a). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A biosignal sensing electrode and a method for manufacturing the same according to one embodiment of the present invention will be described in detail below.

[0018] 1(a)-(b), the biosignal sensing electrode 20 of this embodiment includes a substrate 11 and a conductive film 13 disposed on the substrate 11. The conductive film 13 has a first surface 13a on the substrate 11 side and a second surface 13b on the opposite side to the substrate 11. The first surface 13a and the second surface 13b face each other and may be, for example, parallel to each other. The conductive film 13 further has an end 13c. The end 13c of the conductive film 13 is a surface (end surface) connecting the first surface 13a and the second surface 13b. As described later, a protective material 15 covers at least the end 13c of the conductive film 13. At least a part of the second surface 13b of the conductive film 13 is exposed from the protective material 15, and in the illustrated embodiment, a region A of the second surface 13b (hereinafter referred to as a "sensing region") is exposed from the protective material 15. In the embodiment shown in the figure, the conductive film 13 may be connected to the lead wire 17 at any appropriate portion thereof, but this is not essential when at least the surface 11a of the substrate 11 is conductive. When the biosignal sensing electrode 20 has the lead wire 17, the length of the lead wire 17 is arbitrary, and a pad (not shown) for connecting to another electric circuit element may be formed on the side of the lead wire 17 opposite to the conductive film 13 side.

[0019] The substrate 11 may be conductive or non-conductive. The dimensions, shape, etc. of the substrate 11 may vary depending on the application of the biosignal sensing electrode 20, and the substrate 11 may be flexible or rigid. The substrate 11 may be made of any suitable material, such as a polymer, a metal, a semiconductor, or a ceramic. The substrate 11 may be made of one material or two or more materials. For example, the substrate 11 may be a polymer, a semiconductor, a ceramic, or the like, having a metal layer on the surface 11a. In this embodiment, a flexible substrate made of a polymer such as polyimide is used as the substrate 11.

[0020] 2(a)-(c), the conductive film 13 includes particles 10 of a predetermined layered material. The predetermined layered material is MXene, which is defined as follows: 1. A layered material comprising one or more layers, the layers being represented by the following formula: M m X n where M is at least one group 3, 4, 5, 6, 7 metal and may include at least one selected from the group consisting of so-called early transition metals, such as Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and Mn; X is a carbon atom, a nitrogen atom, or a combination thereof; n is 1 to 4, m is greater than n and less than or equal to 5) 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 a surface of the layer body (more specifically, on at least one of the two opposing surfaces of the layer body). m X n T s ", where s is any number, and conventionally, x is sometimes used in place of s). Typically, n can be 1, 2, 3, or 4, but is not limited thereto.

[0021] In the above formula for 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.

[0022] MXene is a compound represented by the above formula: m X n However, it is known that it can be expressed as follows: 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" mean approximately 1.3 (= 4 / 3) and approximately 0.6 (= 2 / 3), respectively), 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, 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" mean approximately 2.7 (= 8 / 3) and approximately 1.3 (= 4 / 3), respectively.)

[0023] Representatively, M m X n However, Ti2C, Ti3C2, Ti3(CN), (Cr2Ti)C2, (Mo2Ti)C2, (Mo2Ti2)C3, and (Mo 2.7 V 1.3) C3.

[0024] Such MXene particles (hereinafter simply referred to as "MXene particles") 10 can be synthesized by selectively etching (removing and optionally layer-separating) A atoms (and optionally some of the M atoms) from the MAX phase. The MAX phase has the following formula: M m AX n (wherein M, X, n and m are as defined above, and A is at least one Group 12, 13, 14, 15, 16 element, usually a Group A element, typically Group IIIA and Group IVA, and more particularly 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, and is preferably Al). and M m X n (each X may have a crystal lattice in which it is located in the octahedral array of M) between which a layer composed of A atoms is located. In the MAX phase, typically when m=n+1, one layer of X atoms is arranged between each of the n+1 layers of M atoms (collectively referred to as "M m X n The MAX phase has a repeating unit in which a layer of A atoms (also referred to as an "A layer") is arranged as a layer next to the n+1th layer of M atoms, but is not limited thereto. The A atoms (and sometimes a part of the M atoms) are selectively etched (removed and sometimes layer separated) from the MAX phase, thereby removing the A atom layer (and sometimes a part of the M atoms) to expose the M m X n 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 is not limited to this) to terminate the surface.

[0025] 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. In the etching process, stirring is performed at a temperature of room temperature or higher and 40 degrees or lower for approximately 5 hours or more and 48 hours or less. Next, as a cleaning process, the liquid after the etching process is transferred to, for example, a centrifuge tube, pure water is added and stirred, the supernatant and precipitate are separated using a centrifuge, and the supernatant is discarded. This operation is repeated 5 times or more and 20 times or less.

[0026] Thereafter, layer separation of MXene (delamination, separation of multi-layered MXene into monolayered MXene) may be promoted by any appropriate post-treatment (e.g., ultrasonic treatment, hand shaking or automatic shaker, etc.). For example, delamination treatment may be performed for a predetermined time using a mechanical shaker, vortex mixer, homogenizer, ultrasonic bath, etc. Next, the supernatant and precipitate are separated using a centrifuge, and the collected supernatant can be obtained as a dispersion of monolayered MXene particles.

[0027] In the present invention, MXene may contain a relatively small amount of residual A atoms, for example, 10 mass % or less of the original A atoms. The amount of residual A atoms may be preferably 8 mass % or less, more preferably 6 mass % or less. However, even if the amount of residual A atoms exceeds 10 mass %, there may be no problem depending on the application and use conditions of the conductive film (and the biosignal sensing electrode using the same).

[0028] The MXene particles 10 thus synthesized may be particles of layered material comprising one or more MXene layers 7a, 7b, as shown diagrammatically in FIG. 3 (non-limiting examples of MXene particles 10 include a single layer MXene particle 10a shown in FIG. 3(a) and a two layer MXene particle 10b shown in FIG. 3(b)). More specifically, the MXene layers 7a, 7b are each a layer of M m X n The layer body (Mm X n The MXene layers 7a, 7b have "M m X n T s ", where s is any number. The MXene particles 10 may be those in which the MXene layers are individually separated and present as one layer (single layer structure shown in FIG. 3(a), so-called single layer MXene particles 10a), or may be a laminate in which a plurality of MXene layers are stacked at a distance from one another (multilayer structure shown in FIG. 3(b), so-called multilayer MXene particles 10b), or a mixture thereof. The MXene particles 10 may be particles (which may also be referred to as powder or flakes) as an aggregate composed of single layer MXene particles 10a and / or multilayer MXene particles 10b. In the case of multilayer MXene particles, two adjacent MXene layers (e.g. 7a and 7b) do not necessarily have to be completely separated, and may be partially in contact.

[0029] Without being limiting to this embodiment, the thickness of each MXene layer (corresponding 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 (which may vary 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) (which may correspond to the "in-plane dimension" of the particle) is, for example, 0.1 μm or more, particularly 1 μm or more, for example 200 μm or less, particularly 40 μm or less.

[0030] When the MXene particles are laminate (multilayer MXene) particles, for each laminate, the interlayer distance (or gap dimension, shown as Δd in Figure 3(b)) is, for example, 0.8 nm or more and less than 10 nm, particularly 0.8 nm or more and 5 nm or less, more particularly about 1 nm, and the maximum dimension in a plane perpendicular to the stacking direction (the two-dimensional sheet surface) (which may correspond to the "in-plane dimension" of the particle) is, for example, 0.1 μm or more, particularly 1 μm or more, for example 100 μm or less, particularly 20 μm or less.

[0031] The total number of layers in the MXene particle may be 1 or 2 or more, for example, 1 to 20, and the thickness in the stacking direction (which may correspond to the "thickness" of the particle) is, for example, 0.8 to 20 nm.

[0032] When the MXene particles are laminate (multilayer MXene) particles, they may be MXenes with a small number of layers. The term "small number of layers" refers to, for example, MXenes with six or fewer stacked layers. The thickness of the multilayer MXenes with a small number of layers in the stacking direction may be less than 10 nm. In this specification, this "multilayer MXene with a small number of layers" is also referred to as "few-layer MXenes."

[0033] Although not limiting this embodiment, the MXene particles may be particles (which may also be referred to as nanosheets) composed mostly of monolayer MXene and / or few-layer MXene. In this specification, monolayer MXene and few-layer MXene may be collectively referred to as "monolayer / few-layer MXene".

[0034] The above dimensions may be determined as number-average dimensions (e.g., number-average of at least 40 particles) based on photographs taken with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an atomic force microscope (AFM), or as distances in real space calculated from the position in reciprocal space of the (002) plane measured by X-ray diffraction (XRD).

[0035] 2(a), the layer of MXene particles 10 is oriented parallel to surface 11a of substrate 11. That the layer of MXene particles 10 is oriented parallel to surface 11a of substrate 11 means that the two-dimensional plane (sheet plane) of the layer of MXene particles 10 for the majority of all MXene particles 10, for example 80% or more of the total, particularly 90% or more, forms an angle of ±10° or less with surface 11a of substrate 11.

[0036] The surface 11a of the substrate 11 is the surface that contacts the first surface 13a of the conductive film 13. The conductive film 13 in which the layer of the MXene particles 10 is oriented parallel to the surface 11a of the substrate 11 may be manufactured by any suitable method. Although this embodiment is not limited to this embodiment, for example, the conductive film 13 can be formed on the substrate 11 by preparing a slurry in which the MXene particles synthesized as described above are dispersed and / or suspended in a suitable solvent, spraying the slurry onto the surface 11a of the substrate 11, and drying and removing the solvent (at least partially, preferably substantially entirely). The drying may be naturally brought about during the supply onto the substrate 11 and / or may be carried out thereafter. By such spraying and drying, the MXene particles 10 are deposited with the layer of the MXene particles 10 oriented parallel to the surface 11a of the substrate 11. The conductive film 13 obtained in this manner may be binderless.

[0037] The spraying and drying may be appropriately repeated until a desired film thickness is obtained. For example, a combination of spraying and drying may be repeated multiple times. However, when a slurry containing a relatively high concentration of MXene particles 10 is used, a relatively thick film (e.g., a thickness of 0.5 μm or more) can be obtained by performing only one spraying (and optionally drying), and the number of sprays (and optionally drying) performed until a desired film thickness is obtained can be reduced.

[0038] The thickness of the conductive film 13 is not particularly limited, and may be, for example, 200 nm or more and 20 μm or less. When the thickness of the conductive film 13 is 200 nm or more, the continuity of the film is maintained, and sensing can be performed stably. When the thickness of the conductive film 13 is 20 μm or less, the flexibility of the base material is not impaired, and stress concentration due to bending is small, so that sensing can be performed stably. Preferably, the thickness of the conductive film 13 may be 500 nm or more and / or 10 μm or less.

[0039] 1(a)-(b), at least the end 13c of the conductive film 13 is covered with a protective material 15. In this embodiment, the protective material 15 further covers the outer circumferential region of the second surface 13b of the conductive film 13, but this is not essential to the present invention. The outer circumferential region of the second surface 13b may be any region on the second surface 13b adjacent to the end 13c, and in the illustrated embodiment, it is a region of the second surface 13b excluding the sensing region A, but is not limited thereto.

[0040] The protective material 15 may include a polymer 16 having, as a functional group, (i) C=O and (ii) at least one of OH and NH. With reference to Figs. 2(a) and (b), these functional groups of the polymer 16 are bonded to the MXene particle 10, and more specifically, can form hydrogen bonds with the modified or terminal 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) of the MXene particle 10 (in Fig. 2(a), the polymer 16 in the protective material 15 and that has permeated the conductive film 13 originating from the protective material 15 is shown by a wavy line, and in Fig. 2(b), the hydrogen bond is shown by a dotted line). More specifically, with reference to Table 1, the acceptor of the functional group can form a hydrogen bond with the hydrogen donor of the modified / terminal T, and the hydrogen donor of the functional group can form a hydrogen bond with the acceptor of the modified / terminal T.

[0041] [Table 1]

[0042] MXene particles 10 are susceptible to oxidation at the edges of the layer, but by orienting the layer of MXene particles 10 in the conductive film 13 parallel to the surface 11a of the substrate 11 and covering at least the ends 13c of the conductive film 13 with a protective material 15 containing a polymer 16 having the above-mentioned functional groups, the functional groups of the polymer 16 bond to the MXene particles 10 (by hydrogen bonding with the modification / terminal T) at least at the ends 13c, it is possible to effectively suppress (preferably prevent) oxidation of the MXene particles 10. Such an effect of the protective material 15 can be understood as protection of the MXene particles 10 from oxidation. Although the present invention is not bound by any theory, it is believed that components derived from the surrounding environment, such as air, or from living organisms that may be subjects, which cause oxidation of MXene particles 10 (water, water vapor, oxygen, etc.) can easily penetrate through the edge of the layer of MXene particles 10 from the end 13c of the conductive film 13, and oxidation can begin from the edge of the layer of MXene particles 10. In this embodiment, it is believed that the polymer 16 is strongly bonded (hydrogen bonded) to the MXene particles 10, thereby effectively preventing the above-mentioned components, such as water, water vapor, and oxygen, from accessing the end 13c of the conductive film 13.

[0043] Furthermore, polymer 16 having functional groups capable of forming hydrogen bonds as described above can penetrate into conductive film 13. More specifically, such polymer 16 can penetrate between MXene particles 10 in conductive film 13, and inside conductive film 13, the functional groups of polymer 16 can bond with MXene particles 10 (hydrogen bond with modification / terminal T), thereby more effectively suppressing oxidation of MXene particles 10. (Note that the portion of protective material 15 that has not penetrated conductive film 13 may also be referred to as a protective film.)

[0044] The penetration of polymer 16 into conductive film 13 may be to a depth equal to or greater than the depth of one MXene particle 10. Because protective material 15 covers end 13c, the penetration depth dt in the thickness direction from end 13c may be equal to or greater than the thickness of MXene particle 10. When protective material 15 further covers the outer peripheral region of second surface 13b, the penetration depth dp in the in-plane direction from second surface 13b may be equal to or greater than the in-plane dimension of MXene particle 10.

[0045] MXene particle 10 necessarily has at least one type of modification / terminal T selected from the group consisting of hydroxyl group, fluorine atom, chlorine atom, oxygen atom, and hydrogen atom, and therefore, as can be seen from Table 1, necessarily has at least one of modification / terminal T that can be a hydrogen donor and modification / terminal T that can be a hydrogen acceptor, so by selecting polymer 16 having, as functional groups, (i) C=O, which is a hydrogen acceptor, and (ii) at least one of OH and NH, which are hydrogen donors, it is possible to ensure that polymer 16 exhibits an interaction with MXene particle 10, and a bonding force is generated between them. In many cases, MXene particle 10 has both modification / terminal T (at least one of hydroxyl group and hydrogen atom) that can be a hydrogen donor and modification / terminal T (at least one selected from the group consisting of fluorine atom, chlorine atom, and oxygen atom) that can be a hydrogen acceptor. In such a case, by selecting a polymer 16 having as its functional groups (i) C=O, which is a hydrogen acceptor, and (ii) at least one of OH and NH, which are hydrogen donors, the polymer 16 can exhibit strong interaction with the MXene particles 10, resulting in high binding strength between them. Since the MXene particles 10 have a high proportion of acceptor modifications / terminal T, by selecting a polymer 16 having at least one of OH and NH, which are hydrogen donors, in addition to C=O, which is a hydrogen acceptor, the polymer 16 can exhibit stronger interaction with the MXene particles 10, resulting in higher binding strength to the MXene particles.

[0046] Specifically, the polymer 16 may be at least one selected from the group consisting of polyvinyl alcohol, polyisocyanate-crosslinked acrylic resin, epoxy-crosslinked acrylic resin, and polyamideimide. As shown in Table 2, these polymers have functional groups that can bond to MXene particles (hydrogen bonds with modification / terminal T), and can obtain high bonding strength with MXene particles, firmly bind MXene particles to each other, and are unlikely to peel off from the conductive film 13. However, polymers that can be used in this embodiment are not limited to these.

[0047] [Table 2]

[0048] There is no particular limitation on the method for covering the predetermined area of ​​the conductive film 13 (at least the end portion 13c and, in some cases, the outer peripheral area of ​​the second surface 13a) with the protective material 15. For example, coating, a bar coater, screen printing, or the like can be appropriately used.

[0049] When present, the lead wire 17 may be formed at any appropriate timing as long as it is finally connected to the conductive film 13. For example, the lead wire 17 may be provided on the substrate 11 before the conductive film 13 is formed, and when the substrate 11 has a metal layer on the surface 11a, the lead wire 17 may be formed integrally with the metal layer. Also, for example, the lead wire 17 may be connected (for example, by soldering) to a region of the conductive film 13 that is not covered with the protective material 15 after a predetermined region of the conductive film 13 is covered with the protective material 15.

[0050] Sensing area A of conductive film 13 (and possibly one or more other areas, such as area B (not shown) for connecting lead wire 17) is not covered by protective material 15 and is exposed from protective material 15.

[0051] The sensing area A is an area intended and / or designed to detect a biological signal. The sensing area A may have various forms as long as it is exposed from the protective material 15 and is capable of detecting a biological signal. The sensing area A may be in direct or indirect contact with a living organism or biological tissue that may be a subject, and may be capable of directly or indirectly detecting a biological signal from the subject. A living organism may be understood as a subject in a broad sense, and biological tissue may be understood as a subject in a narrow sense. A biological tissue may be part of a living organism (e.g., a human body), but may also be separated from a living organism.

[0052] The biological tissue (measurement target) as a specimen that emits a biological signal may be, more specifically, the skin of a human body or the like, or may be blood vessels, muscles, the brain, or other organs that are located under the skin. When the measurement target is biological tissue exposed to the outside (e.g., skin), the sensing area A may be brought into contact with the biological tissue of the measurement target (directly or indirectly, as described below) to directly detect (measure) the biological signal from the biological tissue of the measurement target. When the measurement target is biological tissue that is located under another biological tissue (e.g., skin) that is exposed to the outside, the sensing area A may be brought into contact with the other biological tissue (e.g., skin) (directly or indirectly, as described below) to indirectly detect (measure) the biological signal from the biological tissue of the measurement target.

[0053] As shown in FIG. 1, the sensing region A may be exposed to the atmosphere outside the biosignal sensing electrode 20. In this case, the sensing region A may be directly contacted with a living body or a living tissue. Alternatively, the sensing region A may be covered with any appropriate other laminate (not shown). In this case, the sensing region A may be indirectly contacted with a living body or a living tissue via the other laminate. Such other laminate may be, for example, a conductive material layer, a gel or a film permeable to ions, or the like. The film permeable to ions may be a porous membrane. The porous membrane may be a membrane having a large number of fine pores and capable of selectively permeating ions or molecules having a size smaller than the diameter of the pores. Such other laminate may be formed of an organic material, an inorganic material, or a mixture thereof, without being particularly limited. For example, the organic material may be a polymer such as a hydrophilic polymer, the inorganic material may be ceramics, or a combination of these. The thickness of the other laminate may be, for example, 0.1 μm or more and 300 μm or less. The porous membrane may have an average pore size of, for example, 1 nm or more and 1 μm or less. The porous membrane may be, for example, an aggregated particulate porous membrane, a mesh-like porous membrane, a fibrous porous membrane, a porous membrane having a plurality of isolated and / or interconnected pores, a honeycomb-structured porous membrane, etc., depending on the pore shape.

[0054] The area of ​​the sensing region A is not particularly limited, but is, for example, 0.5 mm 2 More than 750mm 2 The area of ​​the sensing region A can be 0.5 mm or less. 2 By satisfying the above, the contact (direct or indirect) with the living body or living tissue (e.g., skin) that may be the subject can be improved, and stable sensing of the biological signal can be performed. 2 By setting the area of ​​the sensing region A to 2 mm or less, the influence of motion artifacts due to the movement of the subject (e.g., body movement) can be minimized, and stable sensing of biological signals can be performed. 2 and / or 500mm 2 It can be the following:

[0055] The sensing region A only needs to be in direct or indirect contact with a living body or a living tissue at least when sensing a biological signal. For example, the sensing region A (and the other laminated material, if any) may be covered with a peelable protective seal (not shown), and when sensing a biological signal with the biological signal sensing electrode 20, the protective seal may be peeled off to bring the sensing region A into direct or indirect contact (through the other laminated material) with a living body or a living tissue.

[0056] According to the biosignal sensing electrode 20 of this embodiment, by using the conductive film 13 containing the MXene particles 10, it is possible to effectively suppress the oxidation of the MXene particles 10 in the conductive film 13 as described above while realizing a relatively high conductivity (and therefore a relatively low impedance), thereby effectively reducing deterioration of the sensing ability over time. Specifically, the sensing ability can be the interface impedance between the conductive film 13 and a living body or living tissue (e.g., human skin) in the sensing region A, and typically the impedance of the conductive film measured by a three-electrode method. According to this embodiment, it is possible to effectively reduce the change over time in the impedance of the conductive film 13, and obtain high stability.

[0057] Although the biosignal sensing electrode in one embodiment of the present invention has been described in detail above, the biosignal sensing electrode in the above embodiment can be modified in various ways.

[0058] For example, as shown in Figures 4 and 5, the biosignal sensing electrodes 21, 23 may further include a cover 19 disposed on the second surface 13b of the conductive film 13, with the sensing area A (and other laminates, if present) exposed from the cover 19.

[0059] More specifically, in one modified example, like the biosignal sensing electrode 21 shown in Fig. 4, the sensing region A (and the other laminated material, if any) which is a part of the second surface 13b is exposed from the protective material 15, and more specifically, the protective material 15 may cover the outer peripheral region of the second surface 13b and be present between the conductive film 13 and the cover 19. In this case, the protective material 15 may perform the function of adhering the cover 19 to the conductive film 13 and the function of adhering the cover 19 to the substrate 11. Note that, even in this example, a polymer derived from the protective material 15 may permeate into the conductive film 13.

[0060] 5, the entire second surface 13b is exposed from the protective material 15, and a part of the second surface 13b, that is, the sensing region A (and the other laminated material, if any) is exposed from the cover 19; more specifically, the protective material 15 does not cover the outer peripheral region of the second surface 13b, and may not be present between the conductive film 13 and the cover 19. In this case, the protective material 15 can function to adhere the cover 19 to the substrate 11. Note that, even in this example, a polymer derived from the protective material 15 can permeate into the conductive film 13.

[0061] In any of the modified examples, the adhesive function may be, but is not limited to, hydrogen bonding.

[0062] The size, shape, etc. of the cover 19 may vary depending on the application of the biosignal sensing electrodes 21, 23, and may be either flexible or rigid. The cover 19 may be made of any suitable material, such as, for example, a polymer, a metal, a semiconductor, a ceramic, etc. The cover 19 may be made of one material or two or more materials.

[0063] The biosignal sensing electrode of the present invention is not limited to the above-mentioned embodiment and modified examples. For example, referring to FIG. 6, a biosignal sensing electrode 25 of another embodiment includes a substrate 11 and a conductive film 13 disposed on the substrate 11, and a sensing region A (and the above-mentioned other laminated material, if present) which is a part of the second surface 13b is exposed from the protective material 15, and more specifically, the protective material 15 may cover the end 13c of the conductive film 13 and the outer peripheral region of the second surface 13b. Furthermore, in the illustrated embodiment, a cover 19 may be bonded to the end 13c of the conductive film 13 and the outer peripheral region of the second surface 13b via the protective material 15. In the biosignal sensing electrode 25, the substrate 11 may be conductive and may be connected to or integrally molded with a conductive terminal portion 12. For example, the substrate 11 and the terminal portion 12 may be made of metal. Note that in the embodiment shown in FIG. 6, the cover 19 is not essential, and the cover 19 may not be provided.

[0064] In addition, the description of the biosignal sensing electrode described with reference to FIGS. 1 to 3 can be applied to the biosignal sensing electrode described with reference to FIGS. 4 to 6 unless otherwise specified. EXAMPLES

[0065] We fabricated biosignal sensing electrode samples with different protective polymers and evaluated the stability of their sensing capabilities. We also analyzed the cross sections of the conductive films of each sample.

[0066] Sample preparation A slurry was prepared by dispersing MXene particles in water at a concentration of 10 mg / mL. The slurry prepared above was sprayed onto a gold-deposited glass slide (on the gold-deposited surface) and dried overnight in a vacuum oven (350 mmTorr) at 70 °C to form a conductive film of MXene particles on the gold-deposited glass slide. A protective material-containing liquid (described later) was then applied by screen printing to the end of the conductive film and to a predetermined area on the top surface of the conductive film (area excluding sensing area A and area B for connecting the lead wire). A corresponding polymer film (having an opening corresponding to sensing area A and an opening corresponding to area B for connecting the lead wire) was then placed on the above-mentioned predetermined area and dried in an oven at 70 °C for 5 hours. A lead wire (for evaluation) consisting of a lead wire was then soldered to the conductive film in the above-mentioned area B. The soldered portion was covered with Kapton tape so as to seal area B from the surrounding atmosphere. This produced a biosignal sensing electrode sample.

[0067] In Examples 1 to 4 and Comparative Examples 1 to 4, a liquid in which each polymer shown in Table 3 was dispersed in a solvent (for example, water in the case of polyvinyl alcohol) was used as the protective material-containing liquid (liquid containing the raw materials of the protective material). In Examples 1 to 4 and Comparative Examples 1 to 4, biosignal sensing electrode samples with different protective material polymers were produced under the same conditions except that different protective material-containing liquids were used.

[0068] -Evaluation of stability of sensing ability (impedance) Each sample was immersed in phosphate buffered saline (PBS: Quality Biological, pH 7.4) in a beaker, and the impedance of the conductive film was measured every 4 hours. The temperature of the phosphate buffered saline and the impedance measurement were room temperature. The impedance measurement was performed using an AUTOLAB potentiostat with the three-electrode method, using the sample as the working electrode (more specifically, the conductive film on the gold vapor deposition film was used as the working electrode via a lead wire), platinum as the counter electrode, and a silver / silver chloride electrode as the reference electrode (this measures the impedance between the reference electrode and the working electrode), under the condition of 10 Hz. The measured values ​​before immersion, after immersion for 12 hours, and after immersion for 24 hours are also shown in Table 3.

[0069] Referring to Table 3, in Examples 1 to 4 (polymers: polyvinyl alcohol, polyisocyanate-crosslinked acrylic resin, epoxy-crosslinked acrylic resin, polyamideimide), even after 24 hours of immersion, almost no change was observed in the impedance measurements over time, indicating high stability. On the other hand, in Comparative Examples 1 to 4 (polymers: polyethylene, polypropylene, fluorine-based resin, ethylene-vinyl acetate copolymer resin), even after 12 hours of immersion, a change was observed in the impedance measurements over time, indicating poor stability.

[0070] [Table 3]

[0071] Cross-sectional analysis of conductive films The conductive film was cut and the exposed cross section was analyzed by infrared spectroscopy (IR) to determine whether or not a polymer was detected. The results are also shown in Table 3. In Examples 1 to 4 (polymers: polyvinyl alcohol, polyisocyanate-crosslinked acrylic resin, epoxy-crosslinked acrylic resin, polyamideimide), a polymer was detected inside the conductive film. On the other hand, in Comparative Examples 1 to 4 (polymers: polyethylene, polypropylene, fluorine-based resin, ethylene-vinyl acetate copolymer resin), a polymer was not detected inside the conductive film.

[0072] From the above results, it is believed that the polymers of Examples 1 to 4 have functional groups of C=O and at least one of OH and NH, can penetrate into the conductive film, and the functional groups of the polymer can bond to the MXene particles (hydrogen bond with the modified / terminated T), strongly bonding the MXene particles together, preventing the intrusion of water, etc. originating from saline from the ends of the conductive film, and effectively reducing oxidation of the MXene particles, thereby preventing changes in impedance over time and achieving high stability. On the other hand, the polymers of Comparative Examples 1 to 4 do not have functional groups of C=O and at least one of OH and NH, and therefore do not achieve the above-mentioned effects. [Industrial Applicability]

[0073] The biosignal sensing electrode of the present invention may be used for any appropriate application, and may be used by directly or indirectly contacting the sensing area of ​​the conductive film with a living body or living tissue (e.g., human skin, etc.) that may be a subject to sense a biosignal, but is not limited to this.

[0074] This application is based on and claims priority to U.S. Provisional Patent Application No. 63 / 231,850, filed with the U.S. Patent and Trademark Office on August 11, 2021, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0075] 1a, 1b layer body (M m X n layer) 3a, 5a, 3b, 5b Modified or terminal T 7a, 7b MXene layers 10, 10a, 10b MXene (layered material) particles 11 Base material 12 Terminal section 13 Conductive film 13a 1st page 13b Side 2 13c end 15 Protective materials 16 Polymers 17 Lead Line 19 Cover 20, 21, 23, 25 Biosignal Sensing Electrodes A Sensing Area dp Penetration depth in the in-plane direction dt Penetration depth in thickness direction

Claims

1. A biosignal sensing electrode, comprising: a substrate; a conductive film disposed on the substrate, the conductive film having a first surface on the substrate side and a second surface opposite to the substrate; wherein the conductive film contains particles of a layered material including one or more layers; the layer has the following formula: M ｍ X ｎ (wherein M is at least one metal of Groups 3, 4, 5, 6, and 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 5 or less) and includes a layer body represented by the formula 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, and is oriented parallel to the surface of the substrate; A protective material containing a polymer having C=O and at least one of OH and NH as functional groups covers at least an end portion of the conductive film, the functional groups are bonded to the particles of the layered material, and at least a part of the second surface of the conductive film is exposed from the protective material. The biosignal sensing electrode.

2. The biosignal sensing electrode according to claim 1, wherein the polymer penetrates into the conductive film.

3. The biosignal sensing electrode according to claim 1 or 2, wherein the polymer includes at least one selected from the group consisting of polyvinyl alcohol, polyisocyanate-crosslinked acrylic resin, epoxy-crosslinked acrylic resin, and polyamideimide.

4. The biosignal sensing electrode according to claim 1 or 2, wherein the protective material further covers an outer peripheral region of the second surface of the conductive film.

5. The biosignal sensing electrode according to claim 1 or 2, further including a cover disposed on the second surface of the conductive film, and a part of the second surface being exposed from the cover.

6. Said M ｍ X ｎ is at least one selected from the group consisting of Ti ２ C, Ti ３ C ２ , Ti ３ (CN), (Cr ２ Ti)C ２ , (Mo ２ Ti)C ２ , (Mo ２ Ti ２ )C ３ , and (Mo ２．７ V １．３ )C ３ The biological signal sensing electrode according to claim 1 or 2, represented by at least one selected from the group consisting of

Images