JP2019187808A - Carbon electrode and manufacturing method of the same - Google Patents

Abstract

To provide a new carbon electrode capable of having an extremely fine and complicated electrode array and/or structure.SOLUTION: The carbon electrode is provided which includes: a polymer sheet including at least one kind selected from a group consisting of polyimide, polyethylene naphthalate, parylene, polylactic acid and cellulose; and a continuous structure of carbon including graphite, wherein the continuous structure is at least partially embedded inside the polymer sheet. The continuous structure of carbon including graphite can be formed inside the polymer sheet including at least one kind selected from a group consisting of polyimide, polyethylene naphthalate, parylene, polylactic acid and cellulose by condensed irradiation of ultrashort pulse laser beam having a pulse energy of 0.1 nJ or more and 50 μJ or less, a wave length of 380nm or more and 1,550 nm or less, and a pulse width of 5 fs or more and 500 ps or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a carbon electrode and a manufacturing method thereof.

  The carbon electrode is an electrode using carbon as a conductive portion, and the conductive portion (carbon portion) has one or a plurality of electrode portions or electrode arrays made of carbon. Carbon electrodes are more compatible with living organisms (including cells, tissues, organs, etc.) than metal electrodes, and detect signals from living organisms or give electrical stimulation to living organisms. For example, it is used as a living body electrode because it can be finely formed.

  Since the carbon electrode is hard and brittle, and the carbon portion (conductive portion) that can be finely formed is not always durable due to the property of carbon, the carbon portion is covered and / or covered with an insulator such as a polymer. Can be protected. For example, an electrode assembly in which an electrode made of carbon fiber is embedded in an insulator coating film so that at least a part of the electrode is exposed is known (Patent Document 1). In addition, a conductive coating containing carbon black and polyester resin is provided on one side of a flexible insulating film to form an electrode plate, and an electrode pad made of an acrylic polymer material is provided on the conductive coating forming surface. Electrodes for use are also known (Patent Document 2). Moreover, after extruding into a fine wire shape a composition in which crystalline carbon fine powder and an organic binder are dispersed and composited, and then firing, the organic binder is carbonized to obtain a pure composite carbon fine wire, There is also known a carbon microelectrode in which the entire surface excluding the conductive portions at both ends is covered with an insulator such as a synthetic resin (Patent Document 3).

JP-T-2006-519981 JP-A-4-236940 Japanese Patent Laid-Open No. 3-188367

  In order to accurately detect a signal from a living body or to effectively apply an electrical stimulus to the living body, a carbon electrode having an extremely fine and complicated electrode arrangement and / or structure is desired. However, conventional carbon electrodes as described above are no longer sufficient to meet the higher demands associated with the evolution of biotechnology.

  An object of the present invention is to provide a novel carbon electrode capable of having an extremely fine and complicated electrode arrangement and / or structure, and a method for producing the same.

According to one aspect of the present invention,
A polymer sheet containing at least one selected from the group consisting of polyimide, polyethylene naphthalate, parylene, polylactic acid and cellulose;
There is provided a carbon electrode comprising a continuous structure of carbon containing graphite, wherein the continuous structure is at least partially embedded in the polymer sheet.

  In one embodiment of the present invention, the carbon electrode may be a biological electrode.

  In one aspect of the present invention, the continuous structure includes one or more first portions extending in the thickness direction of the polymer sheet and at least partially exposed from the polymer sheet. obtain.

  In the above aspect of the present invention, the continuous structure further includes a second portion extending in an in-plane direction of the polymer sheet, and the first portion and the second portion are electrically connected to each other. It's okay. For example, the second portion may be embedded in the polymer sheet or exposed from the polymer sheet.

  In the above aspect of the present invention, the carbon electrode may further include a conductive portion disposed on a surface of the polymer sheet, and the first portion and the conductive portion may be electrically connected to each other. .

  According to another aspect of the present invention, polyimide, polyethylene naphthalate is condensed and irradiated with ultrashort pulse laser light having a pulse energy of 0.1 nJ to 50 μJ, a wavelength of 380 nm to 1550 nm, and a pulse width of 5 fs to 500 ps. There is provided a method for producing a carbon electrode, comprising forming a continuous structure of carbon containing graphite in a polymer sheet containing at least one selected from the group consisting of phthalate, parylene, polylactic acid and cellulose. The

  In one aspect of the present invention, the ultrashort pulse laser beam may be an ultrashort pulse laser beam having a pulse energy of 0.1 nJ to 10 μJ, a wavelength of 500 nm to 1100 nm, and a pulse width of 5 fs to 10 ps.

  According to the present invention, there is provided a carbon electrode including a predetermined polymer sheet and a continuous carbon structure including graphite, wherein the continuous structure is at least partially embedded in the polymer sheet. Such a continuous structure can be formed inside the predetermined polymer sheet as desired by condensing and irradiating a predetermined ultrashort pulse laser beam, so that an extremely fine and complicated electrode arrangement and / or Alternatively, a novel carbon electrode capable of having a structure and a manufacturing method thereof are provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows the manufacturing method of the carbon electrode in one embodiment of this invention, Comprising: (a) is the case where a short pulse laser beam is moved to the in-plane direction of a polymer sheet (left side figure), and thereby A continuous structure (right side view) extending in the in-plane direction formed in the polymer sheet is shown, and (b) is a case of moving ultrashort pulse laser light in the thickness direction of the polymer sheet (left side view). And the continuous structure (right side figure) extended in the thickness direction formed in the polymer sheet by it is shown. It is a figure which shows one example of the structure of the carbon electrode in one embodiment of this invention, Comprising: (a) showed the schematic permeation | transmission perspective view of the carbon electrode, (b) showed by the dotted line in (a) The schematic sectional drawing of a part is shown. It is a figure which shows another example of the structure of the carbon electrode in one embodiment of this invention, Comprising: (a) shows the schematic permeation | transmission perspective view of a carbon electrode, (b) shows by a dotted line in (a) FIG. It is a figure which shows another example of the structure of the carbon electrode in one embodiment of this invention, Comprising: (a) shows the schematic permeation | transmission perspective view of a carbon electrode, (b) shows by a dotted line in (a) FIG. It is a figure which shows another example of the structure of the carbon electrode in one embodiment of this invention, Comprising: (a) shows the schematic permeation | transmission perspective view of a carbon electrode, (b) shows by a dotted line in (a) FIG. It is a schematic diagram explaining the evaluation method (specific resistance measurement) of the laser modification part produced in the polymer sheet in the Example and comparative example of this invention. It is a graph which shows the frequency characteristic of the impedance of the laser modification part (continuous structure) produced in the polymer sheet in the Example of this invention. The STEM image (bright field (BF) STEM image) of the cross section of the laser modification part (continuous structure) produced in the polymer sheet in Example 1 of this invention and its vicinity is shown. FIG. 9 shows a partially enlarged view (bright field (BF) STEM image) of the STEM image in the vicinity of the laser irradiation center portion of FIG. 8. (A) shows the EELS spectrum in five places (Position 1-5) shown in FIG. 8, (b) shows the EELS spectrum of diamond, graphite, and amorphous carbon.

  The carbon electrode and the manufacturing method thereof according to one embodiment of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to such an embodiment.

The carbon electrode of this embodiment is
A predetermined polymer sheet;
A continuous carbon structure including graphite, and the continuous structure is at least partially embedded in the polymer sheet.

  The carbon electrode of this embodiment can be manufactured by forming a continuous structure of carbon containing graphite inside the polymer sheet by condensing and irradiating a predetermined ultrashort pulse laser beam. .

  By condensing and irradiating a predetermined polymer sheet with a predetermined ultrashort pulse laser beam, the present inventors condense the ultrashort pulse laser beam not only on the surface of the polymer sheet but also inside. Acquired the unique knowledge that the polymer present in the irradiated part can be modified to carbon, more specifically graphite, and the ultra-short pulse laser light focusing irradiation part is inside the polymer sheet (and if necessary, In other words, by moving (or scanning) one-dimensionally, two-dimensionally or three-dimensionally on the surface), carbon parts containing graphite obtained by polymer modification can be continuously drawn and formed as desired. For example, it has been found that a continuous carbon structure including graphite can be formed as desired inside (and on the surface) of the polymer sheet.

  For example, as shown in FIG. 1 (a), an ultrashort pulse laser beam 7 is condensed and irradiated inside a polymer sheet 1 from a condensing lens (for example, objective lens) 5, and the condensing irradiation unit 9 is formed on the polymer sheet. 1 is moved continuously in the in-plane direction of the polymer sheet 1 inside the polymer sheet 1 (moving direction is indicated by a single arrow in the left side view of FIG. 1A). The structure 3 can be formed (FIG. 1 (a) right side view). Further, for example, as shown in FIG. 1 (b), ultrashort pulse laser light 7 is condensed and irradiated from inside the polymer sheet 1 from the condensing lens 5, and the condensing irradiation part 9 is made to have a thickness of the polymer sheet 1 (In the left side of FIG. 1 (b), the moving direction is indicated by a single arrow, and in the illustrated embodiment, the moving direction is moved from a deeper position to a shallower position), inside the polymer sheet 1 Thus, the continuous structure 3 extending in the thickness direction of the polymer sheet 1 can be formed (the right side view of FIG. 1B).

  However, the moving direction of the condensing irradiation unit 9 and the direction in which the continuous structure extends are not limited to these examples. The moving direction of the condensing irradiation unit 9 may be an arbitrary direction depending on the desired shape, structure, arrangement, and the like of the continuous structure 3, and two or more directions may be appropriately combined.

  Furthermore, if necessary, the ultra-short pulse laser beam condensing irradiation part 9 is moved from the inside of the polymer sheet 1 to the sheet surface 1a (surface), and from the sheet surface 1a to the inside of the polymer sheet 1. The continuous structure 3 may be exposed from the polymer sheet 1 by moving or moving along the sheet surface 1a of the polymer sheet 1 (for example, the right side view of FIG. 1B). In the middle, the exposed portion of the continuous structure 3 from the sheet surface 1a is indicated by hatching).

  In the present embodiment, the predetermined polymer sheet is a polymer sheet containing at least one selected from the group consisting of polyimide, polyethylene naphthalate (also simply referred to as PEN), parylene, polylactic acid, and cellulose. Such a polymer sheet has biological stability and is compatible and / or non-reactive with living organisms (including cells, tissues, organs, etc., and also including nerve cells and nerve tissues, muscle cells and muscle tissues, etc.). High nature. Polyimide and PEN are used as substrates for flexible electronics, and polyimide is also used for medical purposes. PEN has higher heat resistance than polyethylene terephthalate (also referred to simply as PET) (the glass transition temperature of PEN is 155 ° C, 40 ° C higher than the glass transition temperature of PET), and is thin due to its high rigidity. It has advantages such as excellent dimensional accuracy, chemical stability, and excellent gas barrier properties, and is used as a brightness enhancement film for liquid crystal panels, heat-resistant capacitors, speaker diaphragms, and the like. Parylene (also called paraxylene polymers, including Parylene N, Parylene C, Parylene D, etc.) has been approved as a biocompatible material by the FDA (American Food and Drug Administration), coronary stents, neurostimulators, artificial Used for surface inactivation of cochlea and pacemakers. Polylactic acid and cellulose are also biocompatible and are also used as substrates for flexible electronics.

  The polymer sheet may be a single layer sheet or a laminated sheet composed of a plurality of layers as long as it contains at least one of such materials, and can be prepared by any appropriate method, for example, a molded sheet. It's okay. Such a polymer sheet may be inflexible, but it is preferable that the polymer sheet has flexibility because the carbon electrode can be used for flexible applications and can be easily applied to a living body, for example. The thickness of the polymer sheet is not particularly limited, but may be, for example, 10 μm to 250 μm, typically 25 μm to 125 μm.

  The polymer sheet may be laminated to another substrate (for example, a flexible or non-flexible sheet that can be composed of other materials). Such other base material may be disposed on the side opposite to the irradiation side of the ultrashort pulse laser beam during the production of the carbon electrode of the present embodiment.

  In this embodiment, the predetermined ultrashort pulse laser beam is an ultrashort pulse laser beam having a pulse energy (that is, energy per pulse) of 0.1 nJ to 50 μJ, a wavelength of 380 nm to 1550 nm, and a pulse width of 5 fs to 500 ps. It is. When the wavelength is 380 nm or more and 1550 nm or less, sufficient penetration into the inside of the polymer sheet is enabled, and the ultrashort pulse laser beam is efficiently transmitted to a desired condensing portion inside (and on the surface) of the polymer sheet. Can be irradiated. Furthermore, the pulse energy is 0.1 nJ or more and 50 μJ or less, and the pulse width is 5 fs or more and 500 ps or less, so that ultrashort pulse laser light is condensed and irradiated inside (and on the surface) of the polymer sheet, The polymer present in the focused irradiation portion can be modified, that is, carbonized, more specifically graphitized, and the polymer present in the surrounding area is not substantially damaged by heat (for example, a cavity portion). Etc.), which can locally and selectively be modified to carbon (more specifically, graphite) inside the polymer sheet (and the surface).

  The pulse energy may be 0.1 nJ or more and 50 μJ or less, but may be, for example, 0.1 nJ or more and 10 μJ or less. The wavelength may be 380 nm or more and 1550 nm or less, and may be, for example, a wavelength of 500 nm or more and 1100 nm or less. The pulse width may be 5 fs or more and 500 ps or less, but may be 5 fs or more and 10 ps (or 10,000 fs). By making the range narrower for each condition, the shape (line width, etc.) of the graphite structure can be controlled more appropriately.

  Other conditions regarding the ultrashort pulse laser beam are appropriately determined according to the material and thickness of the polymer sheet to be actually used (or the depth of the focused irradiation portion), the desired line width of the continuous structure to be drawn and formed, and the like. Can be selected. More specifically, the repetition frequency may be, for example, 1 kHz to 1 MHz, particularly 1 kHz to 300 kHz. By increasing the repetition frequency, it is possible to add the effect of heat accumulation. Depending on the material, this effectively works for carbonization. Therefore, the polymer can be efficiently modified by controlling the repetition frequency according to the material of the polymer sheet. For example, PEN is easier to obtain the effect of modification by repetition frequency than polyimide. Therefore, if the repetition frequency is increased, modification is easier to promote. The numerical aperture of the condensing lens that can be used for the condensing irradiation may be, for example, 0.6 or more and 0.9 or less. The moving speed of the condensing irradiation part may be, for example, 0.1 μm / s or more and 500 mm / s or less, particularly 0.1 μm / s or more and 10 mm / s or less. Since the crystallinity of graphite directly affects the conductivity, a moving speed within a narrower range is preferable in order to maintain good crystallinity.

  In the present embodiment, the “continuous structure of carbon containing graphite” is composed of carbon containing graphite (modified by the ultrashort pulse laser beam) derived from the polymer contained in the polymer sheet, and , Which means a structure having a one-dimensional, two-dimensional or three-dimensional overall structure due to the continuous presence of such carbon (thus, can be understood as the “carbon part” of the carbon electrode). Such a continuous structure has conductivity because it is composed of carbon containing graphite (thus, it can be understood as a “conductive portion” of the carbon electrode), and has an electrical resistivity close to that of a living body compared to a metal. It can have impedance matching suitable for a living body. Carbon is light and highly compatible with the living body and / or non-reactive, has little in vivo degradation (even when it comes into contact with water, body fluids, etc.), has low irritation to cells / tissues, and is antithrombotic. Excellent in properties.

  The line width (or thickness) of the continuous structure drawn and formed with one line, more specifically, the dimension of the continuous structure in a cross section perpendicular to the moving direction of the condensing irradiation part (usually a substantially circular cross section) The diameter is variable (adjustable) depending on the irradiation condition of the ultrashort pulse laser beam, and is not particularly limited, but may be, for example, 0.1 μm to 100 μm, typically 1 μm to 20 μm. The overall dimensions of the continuous structure are not particularly limited, and if desired, the continuous structure can be formed in any larger dimension by overlapping drawing formations two-dimensionally and / or three-dimensionally. it can.

  Therefore, according to the present embodiment, continuous structures having various shapes and / or structures can be formed inside (and on the surface) of the polymer sheet only by a single process of condensing irradiation with ultrashort pulse laser light. It can be formed as desired, and a continuous structure having a very fine and complex electrode arrangement and / or structure can be formed.

  In the present embodiment, the continuous structure is at least partially embedded in the polymer sheet. For example, one or more parts of the continuous structure may be exposed from the polymer sheet, and the other part of the continuous structure may be embedded and protected inside the polymer sheet. One or a plurality of portions exposed from the polymer sheet can be used as an electrode portion, and when there are a plurality of electrode portions, these can be used as an electrode array. The portion of the continuous structure exposed from the polymer sheet may protrude, be flush with, or be recessed with respect to the sheet surface (sheet surface) of the polymer sheet.

More specifically, for example, as shown in FIGS. 2 to 5, the carbon electrodes 10, 13, 15, and 17 of the present embodiment are
The polymer sheet 1;
A continuous structure 3 of carbon containing graphite, and the continuous structure 3 is at least partially embedded inside the polymer sheet 1;
The continuous structure 3 may include one or more first portions 3 a that extend in the thickness direction of the polymer sheet 1 and are at least partially exposed from the polymer sheet 1. 2-5, one or more 1st part 3a is exposed from the sheet | seat surface 1a of the polymer sheet 1 (In the figure, the exposed part of one 1st part 3a is made into the arrow. However, the present invention is not limited to this. The continuous structure 3 may further include a second portion 3b extending in the in-plane direction of the polymer sheet 1, as shown in FIGS. 2 to 5, for example. In this case, the first portion 3a and the second portion 3b are electrically connected to each other. The second portion 3b may be embedded in the polymer sheet 1 (see FIGS. 2 and 4) or may be exposed from the polymer sheet 1 (see FIGS. 3 and 5). The second portion 3b is exposed from the sheet surface 1b opposite to the sheet surface 1a from which the first portion 3a is exposed, but is not limited to this.

  In the present invention, the “thickness direction of the polymer sheet” refers to the two sheet surfaces 1a and 1b (or these two sheets) facing each other in a state where the polymer sheet is placed on a flat place. When the planes are not parallel to each other, they are parallel to or approximately parallel to the normal line (indicated by the alternate long and short dash line in FIGS. 2 to 5B) of the virtual center plane equidistant from the two sheet planes. It means a parallel direction, for example, a direction that forms an angle of 0 ° to 30 °, particularly 0 ° to 15 ° with respect to the normal line. In the present invention, the “in-plane direction of the polymer sheet” means a direction perpendicular or substantially perpendicular to the normal line, for example, 60 ° or more and 90 ° or less, particularly 75 ° with respect to the normal line. It means a direction that forms an angle of 90 ° or more. The angle formed by the straight line (the normal line) and the direction refers to the size of the angle formed by the straight line and the direction.

  In the carbon electrode 10 exemplarily shown in FIG. 2, a plurality of second portions 3 b extend in the in-plane direction inside the polymer sheet 1, and a plurality of second portions 3 b are provided for each of the second portions 3 b. The first portions 3a are connected (and thus electrically connected to each other) and extend in the thickness direction inside the polymer sheet 1, and the end portions of the first portions 3a are exposed from the sheet surface 1a. A continuous structure 3 can be constructed. Each exposed portion of the first portion 3a can be used as an electrode portion, and can be arranged in an array, for example, can exist in a periodic arrangement. The arrangement of the electrode portions can be appropriately designed as desired. In the carbon electrode 10, a plurality of first portions 3a are connected to one second portion 3b, thereby collecting and functioning a plurality of electrode portions (exposed portions of the first portion 3a). / Can act. The carbon electrode 10 can be used, for example, by bringing the electrode parts arranged in an array in this way into contact with an object (for example, a living body described later) and applying electrical stimulation to the object from these electrode parts. However, it is not limited to this.

  In the carbon electrode 13 exemplarily shown in FIG. 3, a plurality of second portions 3 b are exposed from the sheet surface 1 b of the polymer sheet 1 and extend in the in-plane direction. On the other hand, a plurality of first portions 3a are connected (and thus electrically connected to each other) and extend in the thickness direction inside the polymer sheet 1, and the end of each first portion 3a is a sheet surface. The continuous structure 3 can be formed exposed from 1a. Each exposed portion of the first portion 3a can be used as an electrode portion, and can be arranged in an array, for example, can be present in a periodic arrangement, and the same description as in the example shown in FIG. 2 applies.

  In the carbon electrode 15 exemplarily shown in FIG. 4, a plurality of second portions 3b extend in the in-plane direction inside the polymer sheet 1, and one second portion 3b is provided for each second portion 3b. The first portions 3a are connected (and thus electrically connected to each other) and extend in the thickness direction inside the polymer sheet 1, and the end portions of the first portions 3a are exposed from the sheet surface 1a. A continuous structure 3 can be constructed. Each exposed portion of the first portion 3a can be used as an electrode portion, and can be arranged in an array, for example, can exist in a periodic arrangement. The arrangement of the electrode portions can be appropriately designed as desired. In the carbon electrode 15, a single first portion 3 a is connected to a single second portion 3 b, so that a plurality of electrode portions (exposed portions of the first portion 3 a) function / activate individually. Can be made. For example, the carbon electrode 15 is configured such that the electrode parts arranged in an array in this manner are brought into contact with an object (for example, a living body described later), an electric signal is detected at each electrode part, and the detected electric signal is measured. However, the present invention is not limited to this.

  In the carbon electrode 17 exemplarily shown in FIG. 5, a plurality of second portions 3b are exposed from the sheet surface 1b of the polymer sheet 1 and extend in the in-plane direction. On the other hand, one first portion 3a is connected (and thus electrically connected to each other) and extends in the thickness direction inside the polymer sheet 1, and the end portion of each first portion 3a is a sheet surface. The continuous structure 3 can be formed exposed from 1a. Each exposed portion of the first portion 3a can be used as an electrode portion, and can be arranged in an array, for example, can exist in a periodic arrangement, and the same description as in the example shown in FIG. 4 is applicable.

  In the carbon electrode of this embodiment, the continuous structure is at least partially embedded inside the polymer sheet (preferably, in the carbon electrode shown in FIGS. 2 and 4, the continuous structure is an electrode portion. Therefore, the carbon electrode of this embodiment can exhibit high durability. Such a continuous structure can be directly and locally formed inside (and on the surface of) the polymer sheet by condensing irradiation with ultrashort pulse laser light, so that a highly durable carbon electrode can be easily formed. Can be manufactured. The carbon electrode manufacturing method of the present embodiment can be carried out only by a single process of focused irradiation of ultrashort pulse laser light. For example, a conductive material containing carbon is formed on an insulating substrate (for example, a mask). This is an extremely simple process that does not require a printing step, and thereafter a step of coating such a printing site with an insulating material.

  Since the carbon electrode of this embodiment has both the polymer sheet and the continuous structure have biological stability with respect to the living body and has high compatibility and / or non-reactivity, the living body electrode (or It can be suitably used as a biological probe. The biological electrode functions as an input / output device (or interface) in contact with a living body for detecting a signal from the living body or applying an electrical stimulus to the living body. For example, an electroencephalogram, an electrocardiogram, an electromyogram is used. It can be used to measure biological signals such as diagrams and nystagmus, or to provide electrical stimulation to cells, muscle fibers, cranial nerves, etc. for the purpose of culture, treatment, diagnosis, and the like. In the carbon electrode of the present embodiment, the part exposed from the polymer sheet of the continuous structure functions as an input / output unit for the living body, and the other part of the continuous structure is embedded and protected inside the polymer sheet. ing. In this embodiment, the continuous structure can have an extremely fine and complicated electrode arrangement and / or structure desired for a biological electrode, which cannot be realized by printing or the like. For example, acquisition of a biological signal to be measured Can be sized, periodically arranged and / or structured to fit the site where it is desired, or where electrical stimulation is desired to be applied. Therefore, the carbon electrode of this embodiment can measure with high accuracy to accurately capture a biological signal, or can be appropriately connected to cells, muscle fibers, cranial nerves, and the like to effectively provide electrical stimulation. Therefore, it can act as a stable electrode for a living body. The carbon electrode of the present embodiment may be non-invasive, may be brought into contact with the living body surface for a long period of time, or may be left in the living body, and long-term monitoring is possible.

  However, the carbon electrode of the present embodiment can be used for other uses other than the biological electrode. For example, the carbon electrode of the present embodiment can be used for an electronic circuit and / or an element (for example, a sensor, a coil, etc.) that requires a very fine and complicated electrode arrangement and / or structure. In particular, in this embodiment, by drawing and forming a continuous structure while changing the conditions for ultrashort pulse laser light, it is possible to continuously change the characteristics such as the structure and electrical resistivity, It is possible to form an electronic circuit and / or an element (for example, a sensor, a coil, etc.) having a function that has not existed before.

  Although the carbon electrode of this embodiment has been described in detail above, the carbon electrode of this embodiment can be variously modified.

  For example, in the carbon electrode of the present invention, other conductive portions (or conductive members) may be additionally used in addition to the continuous carbon structure including graphite. In one modification, the carbon electrode may further include a conductive portion disposed on the surface of the polymer sheet, and the first portion and the conductive portion of the continuous structure may be electrically connected to each other. More specifically, for example, in the carbon electrodes 13 and 17 described above with reference to FIGS. 3 and 5, the continuous structure 3 includes the second portion 3 b extending in the in-plane direction of the polymer sheet 1. Instead of the second portion 3b, a conductive portion disposed on the surface of the polymer sheet 1 may be provided. Such a conductive portion can be disposed in the same region as the second portion 3b on the surface of the polymer sheet 1 (see FIGS. 3 and 5, the conductive portion is the sheet surface 1a where the first portion 3a is exposed). It can be arranged on the surface of the sheet surface 1b on the opposite side of the sheet surface, but is not limited to this). Such a conductive portion can be made of a conductive material different from the continuous structure, and preferably can be made of a conductive material that exhibits a higher strength than carbon. Examples of such materials include metals such as gold (Au), platinum (Pt), iridium (Ir), titanium (Ti), and copper (Cu), and conductive polymers such as polythiophene polymers. When the carbon electrode is used as a bioelectrode, the conductive portion is made of a material that is not subject to corrosion even when in contact with the living body, such as a corrosion-resistant metal such as gold, platinum, iridium, and titanium, or a polythiophene polymer. The conductive polymer is preferably used. Such a conductive portion is formed on the surface of the polymer sheet after forming a continuous structure inside (and on the surface of) the polymer sheet (for example, after forming the first portion 3a and replacing the second portion 3b). It can be formed in the region. Since the formation of the continuous structure is performed by the focused irradiation of ultrashort pulse laser light, forming the conductive portion after the formation of the continuous structure eliminates the concern that the conductive portion will be destroyed by the laser light. Can do. The method for forming the conductive portion is not particularly limited. For example, when the conductive portion is made of metal, sputtering can be applied, and when the conductive portion is made of a conductive polymer, electrolytic polymerization is applied. be able to.

  According to the above modification, even when an electrode portion is provided on the surface of the polymer sheet, the electrode portion is high by applying a conductive portion made of a conductive material having a higher strength than carbon. A carbon electrode exhibiting durability can be obtained.

(Examples 1-5 and Comparative Examples 1-6)
As the polymer sheet, each sheet having the material and thickness shown in Table 1 was prepared. In Table 1, PI means polyimide, PEN means polyethylene naphthalate, PET means polyethylene terephthalate, PE means polyethylene, PP means polypropylene, PC means polycarbonate, PS means polystyrene, PVC means polyvinyl chloride.

  With respect to each polymer sheet, ultrashort pulse laser light is condensed and irradiated through an objective lens as a condensing lens, and the condensing irradiation part is moved as shown in FIG. A laser modified portion corresponding to a continuous structure having a structure as shown in b) was formed on the polymer sheet. Table 1 also shows the laser light irradiation conditions, the used condensing lens (objective lens), and the moving speed (scanning speed) of the condensing irradiation part.

  The polymer sheet having the laser-modified portion formed therein is cut along the plane passing through the center line of the laser-modified portion (see the cut surface X in FIG. 6A), and the laser on the cut surface Line width (corresponding to the diameter of the substantially circular cross section of the laser modified portion in the cross section perpendicular to the center line) of the modified portion (corresponding to the first portion 3a and the second portion 3b of the continuous structure 3) ) Was measured. Further, the sample is cut out in the region surrounded by the dotted line in FIG. 6A, and corresponds to the laser modified portion 3 ′ (first portion 3a) in the cut surface X of the sample shown in FIG. The first portion 3a and the second portion 3b are considered to have the same electrical characteristics), and the probes 11 are brought into contact with each other in the vicinity of both ends in the length direction, and the specific resistance of the laser modified portion 3 ′ is determined by the two-terminal method. (Electrical resistivity) was measured. The measurement voltage of specific resistance was 1V. Table 1 shows the measurement results of the line width and specific resistance of the laser modified portion. In Table 1, the symbol “-” means that it was out of the measurable range (thus, it was an insulator).

  As understood from Examples 1 to 5 in Table 1, in polyimide, polyethylene naphthalate, parylene C, polylactic acid and cellulose, the specific resistance lower than the specific resistance of the material of the original polymer sheet in the laser modified portion. In particular, it was confirmed that a low specific resistance of 10 Ωcm or less, more specifically 6 Ωcm or less was obtained, in other words, conductivity was obtained. On the other hand, as understood from Comparative Examples 1, 4 and 6, in polyethylene terephthalate, polycarbonate, and polyvinyl chloride, the specific resistance of the laser modified portion is too high, and it has “conductivity”. However, it was confirmed to be suitable for functioning as an electrode. In the comparative examples 2, 3 and 6, polyethylene, polypropylene and polystyrene are not modified in the first place (only the pores are opened or melted) or only deteriorated (the structure of the original polymer is changed but remains an insulator). The specific resistance could not be measured.

  With respect to Examples 1 to 5 in which it was confirmed that the laser modified portion had conductivity, the frequency characteristics of the impedance of the laser modified portion were measured. The results are shown in FIG. 7 (the vertical axis indicates the absolute value (Ω) of the impedance (Z), and the horizontal axis indicates the frequency (Hz)). The measuring instrument used was an E4980A precision LCR meter manufactured by Agilent Technologies. From FIG. 7, in all cases of Examples 1 to 5, the laser modified portion formed on each polymer sheet exhibits good conductivity with respect to the frequency range of 1 to 100 Hz which is important for the living body. Was confirmed.

As a representative example of Examples 1 to 5, FIG. 8 shows a STEM image (bright field (BF) STEM image) of a cross section of the laser modified portion and the vicinity thereof in Example 1. In FIG. 8, a central portion obtained by condensing and irradiating ultrashort pulse laser light is indicated by a dotted line as a “laser irradiation central portion”. As can be understood from FIG. 8, the part irradiated with the ultrashort pulse laser beam is modified to be black compared to the other part not irradiated (“laser non-irradiated part”). It was observed that this focused irradiation portion was locally and selectively modified. 9A shows a partially enlarged view (bright field (BF) STEM image) of the STEM image in the laser modified portion of FIG. 8, and FIG. 9B is a further enlarged view (bright field). (BF) STEM image). 9A and 9B, a layer structure considered to be a layered structure of carbon was observed in the laser modified portion. Furthermore, the EELS spectrum (also simply referred to as “EELS spectrum”) at the CK loss edge was observed by electron energy loss spectroscopy (EELS) at five locations (Positions 1 to 5) where the layered structure was observed in FIG. The results are shown in FIG. In addition, FIG. 10B shows the result of measuring the EELS spectra of diamond, graphite, and amorphous carbon in the same manner as the standard spectrum (reference) of the carbon-based material. Referring to FIGS. 10 (a) and (b), the EELS spectra of Positions 1 and 5 located in the laser modification part are the π * peak near 282 eV corresponding to the presence of the sp ² orbit and the sp ³ orbit. Since the σ * peak near 288 eV corresponding to the presence is clearly seen, it almost coincides with the EELS spectrum of graphite, indicating the presence of graphite. Therefore, it was confirmed that this laser modified portion is a carbon continuous structure containing graphite. On the other hand, the EELS spectrum of Positions 2 to 4 located in the laser non-irradiated part is similar to the EELS spectrum of amorphous carbon, but the shape at 290 to 300 eV is different from the EELS spectrum of amorphous carbon. It was shown to remain a molecule. Examples 2 to 4 also showed the same results as in Example 1.

  From these results, in the polymer sheet containing at least one selected from the group consisting of polyimide, polyethylene naphthalate, parylene C and other parylene, polylactic acid and cellulose, a predetermined ultrashort pulse laser beam By focusing and irradiating, the inside (and surface) of the polymer sheet can be locally and selectively modified into graphite, and therefore, a continuous carbon structure containing graphite can be formed. In addition, it was confirmed that such a continuous structure exhibits good conductivity and can be used as an electrode (electrode part or electrode structure).

(Example 6)
A 125 μm thick sheet made of polyethylene naphthalate was prepared as a polymer sheet. Under the same conditions as in Example 2, the polymer sheet was subjected to focused irradiation with an ultrashort pulse laser beam as a focusing lens through an objective lens, as shown in FIGS. 2 (a) and 2 (b). A laser modified portion corresponding to a continuous structure having a structure was formed on the polymer sheet. When the line width of the laser modified portion (corresponding to the first portion 3a and the second portion 3b of the continuous structure 3) was measured in the same manner as described above, it was about 3 μm.

  The carbon electrode of the present invention can have an extremely fine and complicated electrode arrangement and / or structure, and can be used as a wide variety of electrodes including biomedical electrodes.

DESCRIPTION OF SYMBOLS 1 Polymer sheet 1a Sheet surface 3 Continuous structure 3 'Laser modification part 3a 1st part 3b 2nd part 5 Condensing lens 7 Ultrashort pulse laser light 9 Condensing irradiation part 10, 13, 15, 17 Carbon electrode 11 probe

Claims (9)

A polymer sheet containing at least one selected from the group consisting of polyimide, polyethylene naphthalate, parylene, polylactic acid and cellulose;
A carbon electrode comprising: a carbon continuous structure including graphite, wherein the continuous structure is at least partially embedded in the polymer sheet.   The carbon electrode according to claim 1, which is a living body electrode.   The continuous structure includes one or more first portions extending in a thickness direction of the polymer sheet and at least partially exposed from the polymer sheet. Carbon electrode.   4. The continuous structure according to claim 3, wherein the continuous structure further includes a second portion extending in an in-plane direction of the polymer sheet, and the first portion and the second portion are electrically connected to each other. Carbon electrode.   The carbon electrode according to claim 4, wherein the second portion is embedded in the polymer sheet.   The carbon electrode according to claim 4, wherein the second portion is exposed from the polymer sheet.   The carbon electrode according to claim 3, wherein the carbon electrode further includes a conductive portion disposed on a surface of the polymer sheet, and the first portion and the conductive portion are electrically connected to each other.   A group consisting of polyimide, polyethylene naphthalate, parylene, polylactic acid and cellulose by condensing and irradiating an ultrashort pulse laser beam having a pulse energy of 0.1 nJ to 50 μJ, a wavelength of 380 nm to 1550 nm and a pulse width of 5 fs to 500 ps A method for producing a carbon electrode, comprising forming a continuous structure of carbon containing graphite in a polymer sheet containing at least one selected from the above.   The carbon electrode manufacturing method according to claim 8, wherein the ultrashort pulse laser beam is an ultrashort pulse laser beam having a pulse energy of 0.1 nJ to 10 μJ, a wavelength of 500 nm to 1100 nm, and a pulse width of 5 fs to 10 ps.