Microfluidic chip and manufacturing method thereof

Abstract

To provide a technique for appropriately protecting an electrode of a microfluidic chip.SOLUTION: A microfluidic chip 1 includes: a substrate 10; an electrode 31; an insulating film 33; and a fluid housing part 20. The electrode 31 is arranged on the upper surface of the substrate 10. The insulating film 33 covers the upper surface of the electrode 31. The insulating film 33 is constituted of an oxide film obtained by oxidizing metal contained in the electrode 31 or a nitride film obtained by nitriding the metal contained in the electrode 31. The fluid housing part 20 is capable of housing fluid on the upper side of the insulating film 33.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a microfluidic chip and a method for manufacturing the same. [Background technology]

[0002] In the field of regenerative medicine, importance is attached to separation techniques for separating and capturing biomolecules such as cells, and a separation device that utilizes dielectrophoretic force is known as one such technique (for example, Patent Document 1). This type of separation device includes, for example, a flow path through which biomolecules flow together with a sample liquid (such as a culture liquid), and electrodes for separating the biomolecules. The separation device electrically separates the biomolecules by applying an AC voltage to the electrodes to generate an electric field in the liquid flowing in the flow path. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 207617 Summary of the Invention [Problem to be solved by the invention]

[0004] When a voltage strong enough to move biomolecules is applied to an electrode, an electrochemical reaction occurs between the metal constituting the electrode and the liquid interface, and the electrode can easily be electrolyzed. For this reason, an insulating protective film may be formed by a film formation process to protect the electrode.

[0005] However, the insulating protective film acts as a reactance (pseudo resistance) under AC voltage, lowering the voltage output level from the electrode. For this reason, when the insulating protective film is formed relatively thick (for example, when the electrode film thickness is 100 nm and the insulating protective film is 200 nm), the separation performance may be significantly reduced. On the other hand, when the insulating protective film is formed thinly (for example, 100 nm or less), the electrode surface is easily exposed due to the variation in film formation, and especially when the film is formed in one direction by sputtering or the like, the side wall portion of the electrode is easily exposed.

[0006] An object of the present invention is to provide a technique for appropriately protecting electrodes of a microfluidic chip. [Means for solving the problem]

[0007] In order to solve the above problems, a first aspect of the present invention is a microfluidic chip comprising: a substrate; an electrode disposed on one surface of the substrate; an insulating film covering one surface of the electrode and made of an oxide film obtained by oxidizing a metal contained in the electrode or a nitride film obtained by nitriding the metal; and a fluid storage section capable of storing a fluid on the one side of the insulating film. The electrode includes, in this order toward the one side, a conductive layer including a first metal having conductivity and a surface layer including a second metal different from the first metal, the insulating film being an oxide film or a nitride film of the second metal included in the surface layer, and the second metal being titanium, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound formed of any of these. . A second aspect is a microfluidic chip comprising a substrate, an electrode disposed on one surface of the substrate, an insulating film covering one surface of the electrode and made of an oxide film obtained by oxidizing a metal contained in the electrode or a nitride film obtained by nitriding the metal, and a fluid storage unit capable of storing a fluid on the one side of the insulating film. The fluid storage unit has a flow path through which the fluid flows, and the flow path is located on the one side of the insulating film. The flow path has a first end and a second end, and includes a main flow path through which the fluid flows from the first end to the second end, and a plurality of sub-flow paths through which the fluid flows, the sub-flow paths being connected to the second end of the main flow path, and the electrode applies a voltage for separating particles in the fluid flowing through the main flow path into any one of the plurality of sub-flow paths.

[0008] No. 3 The first aspect is Or the second aspect In the microfluidic chip of claim 1, the fluid storage portion stores the fluid in a state where the fluid is in contact with the insulating film.

[0009] No. 4 The aspect is , No. In a microfluidic chip of two embodiments, the electrode includes, in order toward the one side, a conductive layer including a first metal having conductivity and a surface layer including a second metal different from the first metal, and the insulating film is an oxide film or a nitride film of the second metal included in the surface layer.

[0010] No. 5 The aspect is 4In the microfluidic chip of the embodiment, the second metal is titanium, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound thereof.

[0011] No. 6 The first aspect is Dear In the microfluidic chip, the fluid storage portion has a flow channel through which the fluid flows, and the flow channel is located on the one side of the insulating film.

[0012] No. 7 The aspect is 6 In a microfluidic chip of an embodiment, the flow path has a main flow path having a first end and a second end, through which the fluid flows from the first end to the second end, and a plurality of sub-flow paths through which the fluid flows, the sub-flow paths being connected to the second end of the main flow path, and the electrodes apply a voltage to separate particles in the fluid flowing through the main flow path into any one of the plurality of sub-flow paths.

[0013] No. 8 One aspect is a method for manufacturing a microfluidic chip, comprising the steps of: a) preparing a substrate having an electrode on one surface; b) forming an insulating film, which is an oxide film or a nitride film, on the one surface of the electrode by oxidizing or nitriding a metal contained in the electrode on the substrate; and c) after step b), forming a fluid storage portion capable of storing a fluid on one side of the insulating film. The electrode has, in order toward the one side, a conductive layer containing a first metal having electrical conductivity and a surface layer containing a second metal different from the first metal, The second metal is titanium, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound thereof. A ninth aspect is a method for manufacturing a microfluidic chip, comprising the steps of: a) preparing a substrate having an electrode on one surface; b) forming an insulating film, which is an oxide film or a nitride film, on the one surface of the electrode by oxidizing or nitriding a metal contained in the electrode on the substrate; and c) forming a fluid storage unit capable of storing a fluid on one side of the insulating film after the step b). The fluid storage unit has a flow path through which the fluid flows, and the flow path is located on the one side of the insulating film. The flow path has a first end and a second end, and includes a main flow path through which the fluid flows from the first end to the second end, and a plurality of sub-flow paths through which the fluid flows, the sub-flow paths being connected to the second end of the main flow path, and the electrode applies a voltage for separating particles in the fluid flowing through the main flow path into any one of the plurality of sub-flow paths.

[0014] No. 10 The aspect is 8 Aspects Or the ninth aspect In the method for producing a microfluidic chip, the step b) is a step of forming the insulating film by a thermal oxidation method or a wet oxidation method. Effect of the Invention

[0016] According to the microfluidic chip of the first aspect, the insulating film can be formed by oxidation or nitridation of the electrode surface, which makes it easier to protect the electrodes compared to forming an insulating film by a film deposition process. In addition, since the conductive layer of the first metal ensures the conductivity of the electrode, the second metal can be selected to be suitable for forming an oxide or nitride film, and the electrode can be effectively protected by the oxide or nitride film of the second metal. According to the microfluidic chip of the second embodiment, an insulating film can be formed by oxidizing or nitriding the electrode surface. Therefore, the electrodes can be protected more easily than when an insulating film is formed by a film forming process. Also, a voltage can be applied to the fluid by applying a voltage to the electrodes while the fluid is flowing through the flow channel. Also, the electrodes apply a voltage to separate particles in the fluid flowing through the main flow channel into one of a number of sub-flow channels. This allows the particles in the fluid to be separated.

[0017] No. 3 According to the microfluidic chip of the embodiment, the electrodes can be adequately protected at low cost and with fewer steps, compared to a case where a protective film is formed between the electrodes and the fluid storage portion by a film deposition process.

[0018] No. 4 According to the microfluidic chip of the embodiment, since the electrical conductivity of the electrodes can be ensured by the conductive layer of the first metal, it is possible to select the second metal suitable for forming an oxide film or a nitride film.

[0019] No. 5 According to the microfluidic chip of the embodiment, the electrodes can be effectively protected with an oxide film or nitride film of the second metal.

[0020] No. 6 According to the microfluidic chip of the embodiment, a voltage can be applied to the fluid by applying a voltage to the electrodes while causing the fluid to flow through the channel.

[0021] No. 7 According to the microfluidic chip of the embodiment, the electrodes apply a voltage for separating particles in a fluid flowing through a main channel into any one of a plurality of sub-channels, thereby allowing the particles in the fluid to be separated.

[0022] No. 8 According to the method for manufacturing a microfluidic chip of the embodiment, the insulating film can be formed by oxidizing or nitriding the electrode surface, which makes it easier to protect the electrodes compared to forming the insulating film by a film deposition process. Furthermore, since the conductive layer of the first metal ensures the conductivity of the electrode, the second metal can be selected to be suitable for forming an oxide film or a nitride film.

[0023] No. 10 According to the method for manufacturing a microfluidic chip of the embodiment, the surface of the electrode can be easily oxidized, so that an insulating film can be easily formed. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a plan view of a microfluidic chip according to an embodiment. [Diagram 2] 2A and 2B are a plan view and a cross-sectional view showing a voltage application unit of the microfluidic chip shown in FIG. [Diagram 3] 1A and 1B are diagrams conceptually showing how an insulating film is formed on the surface of an electrode. [Figure 4] FIG. 13 is a diagram showing changes in impedance depending on the presence or absence of an insulating film and a protective film. [Diagram 5] FIG. 13 is a diagram showing the change in capacitance depending on the presence or absence of an insulating film. [Figure 6] FIG. 13 is a plan view showing an electrode on which a durability test was performed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the components described in the embodiment are merely examples, and are not intended to limit the scope of the present invention. In the drawings, the dimensions and numbers of each part may be exaggerated or simplified as necessary for ease of understanding.

[0027] FIG. 1 is a plan view of a microfluidic chip 1 according to an embodiment. The microfluidic chip 1 is a device that applies a voltage to a fluid. The microfluidic chip 1 is, for example, a cell sorter that separates and captures biomolecules such as cells. The microfluidic chip 1 has a substrate 10, a fluid storage unit 20, and a voltage application unit 30. Each component of the microfluidic chip 1 will be described below.

[0028] The substrate 10 is, for example, a glass substrate made of quartz or the like. The fluid storage section 20 has a structure capable of storing a fluid (such as a liquid containing biomolecules) and is made of resin, quartz glass, or the like. The fluid storage section 20 is disposed on the upper side of the substrate 10 (see FIG. 2). The fluid storage section 20 has a sidewall section 21 and a ceiling section 23 (see FIG. 2). The sidewall section 21 and the ceiling section 23 are sections that separate the space in which the fluid is stored, and form walls that stand up against the surface of the substrate 10. The ceiling section 23 is a section that blocks the upper side of the space in which the fluid is stored.

[0029] As shown in Fig. 1, the fluid storage unit 20 constitutes a flow path through which the fluid flows. Specifically, the fluid storage unit 20 has a main flow path 25 and two sub flow paths 27. The main flow path 25 has a first end 251 and a second end 252. The first end 251 is capable of being supplied with liquid. The liquid supplied to the first end 251 flows toward the second end 252.

[0030] The ends of the two sub-channels 27 are each connected to a second end 252 of the main channel 25. The main channel 25 and the two sub-channels 27 are connected to each other so that liquid can flow therethrough.

[0031] The voltage application unit 30 has a plurality of electrodes 31 arranged in a comb-like shape. As shown in FIG. 2, the plurality of electrodes 31 extend so as to cross the main flow path 25 of the fluid storage unit 20.

[0032] An AC voltage for separating biomolecules in the liquid is applied to each electrode 31 of the voltage application unit 30. When an AC voltage is applied, an electric field for separation is generated around each electrode 31. This electric field for separation acts on the biomolecules in the liquid flowing through the main channel 25, so that the biomolecules in the liquid can be sent to one of the two sub-channels 27.

[0033] Fig. 2 is a plan view and a cross-sectional view showing the voltage application unit 30 of the microfluidic chip 1 shown in Fig. 1. As shown in Fig. 2, an electrode 31 of the voltage application unit 30 is disposed on the upper surface of the substrate 10. The electrode 31 is made of a metal having electrical conductivity. Note that the term "metal" here is a concept that includes alloys.

[0034] The electrode 31 shown in FIG. 2 has a multi-layer structure, and includes, from the lower side (substrate 10 side) to the upper side, an adhesive layer 311, a conductive layer 313, and a surface layer 315 in this order. The adhesive layer 311 is a layer provided to bond the surface of the substrate 10 and the electrode 31 to each other, and contains, for example, titanium. The conductive layer 313 is made of a metal having conductivity (such as aluminum). The surface layer 315 is located at the top of the electrode 31, and contains, for example, titanium. The multi-layer structure of the electrode 31 is formed by film formation by, for example, vacuum deposition. The thickness of each layer of the electrode 31 is not particularly limited, but the thickness of the adhesive layer 311 may be 10 nm, the thickness of the conductive layer 313 may be 100 nm, and the thickness of the surface layer 315 may be 10 nm.

[0035] In the electrode 31, the adhesive layer 311 in contact with the substrate 10 is made of titanium, so that the electrode 31 can be adhered to the substrate 10. In particular, when the substrate 10 is a glass substrate, the electrode 31 can be adhered well to the substrate 10. The surface layer 315 of the electrode 31 is provided to form an insulating film 33, which will be described later. The metal (first metal) of the conductive layer 313 is preferably more conductive than the metal (second metal) of the surface layer 315 and the metal of the adhesive layer 311. As the metal of the surface layer 315, in addition to titanium, aluminum, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound made of these may be used.

[0036] The electrode 31 does not necessarily have to be multi-layered, and may be a single layer. The electrode 31 does not necessarily have to contain two or more types of metals, and may contain only one type of metal. When the electrode 31 is made of one type of metal, for example, aluminum, titanium, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound made of these metals may be used.

[0037] 2, the upper surface of the electrode 31 is covered with an insulating film 33. The insulating film 33 is made of an oxide film obtained by oxidizing the metal constituting the electrode 31, or a nitride film obtained by nitriding the metal constituting the electrode 31. In other words, if the element symbol of the electrode metal is "M", the insulating film 33 will be M if it is an oxide film. X O Y , M for nitride film X N Y (X and Y are the numbers of elements).

[0038] FIG. 3 is a conceptual diagram showing how an insulating film 33 is formed on the surface of the electrode 31. As shown in FIG. 3, the insulating film 33 can be formed on the surface of the electrode 31 by performing an oxidation treatment or a nitriding treatment on the surface layer 315 of the electrode 31. When the surface layer 315 is oxidized, for example, a thermal oxidation method (dry thermal oxidation method or hydrothermal oxidation method) or a wet oxidation method can be applied. For example, when the surface layer 315 of the electrode 31 is made of titanium with a thickness of 10 nm, the titanium of the surface layer 315 can be oxidized by treating it for two hours using an autoclave with a water filling rate of 5 to 10% relative to the internal volume of the autoclave and a temperature of 130 to 140° C. When the surface layer 315 is nitrided, a nitriding treatment can be adopted in which the surface layer 315 is exposed to a nitriding atmosphere at a high temperature.

[0039] 2, the surface of the substrate 10 including the electrode 31 on which the insulating film 33 is formed may be covered with a protective film 40. The protective film 40 is, for example, a silicon oxide film (SiO XThe protective film 40 preferably has a thickness of 200 nm or less. As shown in FIG. 2, the protective film 40 constitutes the bottom surface of the flow path formed by the fluid storage unit 20. In other words, the upper surface of the protective film 40 forms the surface that comes into contact with the liquid flowing through the fluid storage unit 20. The insulating film 33 is a titanium oxide film (TiO X ), the adhesion between the insulating film 33 and the protective film 40 (silicon oxide film) can be improved.

[0040] It is not essential that the microfluidic chip 1 includes the protective film 40. That is, the microfluidic chip 1 does not need to include the protective film 40. In this case, the insulating film 33 located on the surface of the substrate 10 and the surface of the electrode 31 constitutes the bottom surface of the fluid storage unit 20. Therefore, when the fluid storage unit 20 stores liquid, the surface of the substrate 10 and the insulating film 33 come into contact with the liquid. Even if the protective film 40 is not provided, the insulating film 33 prevents the electrode 31 from coming into direct contact with the liquid. Therefore, the electrode 31 can be prevented from being electrolyzed when a voltage is applied. In this way, when the protective film 40 is not formed by the film formation process, the cost and number of steps related to the formation of the protective film 40 can be omitted, so that the microfluidic chip 1 can be manufactured at low cost and with a small number of steps.

[0041] The fluid storage unit 20 is attached to the upper surface of the substrate 10 after the insulating film 33 is formed on the surface of the electrode 31. In this way, the fluid storage unit 20 is disposed above the insulating film 33. When a protective film 40 is formed on the upper surface of the substrate 10, the fluid storage unit 20 may be attached to the upper surface of the substrate 10 after the protective film 40 is formed.

[0042] <Changes in electrical characteristics due to insulating films> Next, changes in the electrical characteristics of the microfluidic chip 1 depending on the presence or absence of the insulating film 33 and the protective film 40 will be described with reference to FIGS.

[0043] FIG. 4 is a diagram showing the change in impedance depending on the presence or absence of insulating film 33 and protective film 40. In FIG. 4, the vertical axis indicates impedance, and the horizontal axis indicates frequency. FIG. 5 is a diagram showing the change in capacitance depending on the presence or absence of insulating film 33. In FIG. 5, the vertical axis indicates capacitance, and the horizontal axis indicates frequency. FIGS. 4 and 5 show the results of measuring the electrical characteristics (impedance and capacitance) of microfluidic chip 1 by applying an AC voltage to electrode 31 using an LCR meter. Note that a highly conductive liquid is used as the sample liquid contained in fluid container 20 in order to bring the effect of the liquid on the measured values ​​close to zero.

[0044] 4, graph G11 shows the measurement results when there is no insulating film 33 and no protective film 40. In FIG. 4, graph G12 shows the measurement results when there is an insulating film 33 and no protective film 40. In FIG. 4, graph G13 shows the measurement results when there is no insulating film 33 and no protective film 40 (SiO X 5 shows the measurement results when there is an insulating film 33 and a protective film 40 (film thickness 200 nm). Note that cross-sectional structures of devices D1, D2, and D3 corresponding to graphs G11, G12, and G13 are conceptually shown in FIG. 4. Also, in FIG. 5, graph G21 shows the measurement results when there is an insulating film 33 and a protective film 40. In FIG. 5, graph G22 shows the measurement results when there is an insulating film 33 and no protective film 40.

[0045] As shown in Fig. 4, the impedance is shifted to the high frequency side when the protective film 40 is present (graph G13) compared to when the protective film 40 is not present (graphs G11 and G12). This shift indicates that the reactance is increased due to a decrease in the current generated when an AC voltage is applied. In other words, the high reactance of the protective film 40 causes a voltage drop in the protective film 40, making it difficult to efficiently sweep the voltage into the liquid. Therefore, in order to efficiently sweep the voltage, it is preferable to make the protective film 40 as thin as possible or not to provide the protective film 40.

[0046] 4, in the case where the insulating film 33 is not present (graph G11), the reactance decreases due to the large capacitance of the electric double layer 91 formed at the interface between the electrode 31 and the solution, resulting in a low impedance. On the other hand, in the case where the insulating film 33 is present (graph G12), the impedance shifts to the high frequency side. This indicates that a capacitance component originating from the insulating film 33 is formed, and this is because the combined capacitance with the above-mentioned electric double layer 91 is smaller than when the insulating film 33 is not present. In other words, since the capacitance component originating from the insulating film 33 has a small capacity, the reactance increases, resulting in a high impedance.

[0047] As shown in Fig. 5, without the insulating film 33 (graph G21), an increase in capacitance is observed in the low-frequency region where DC components begin to appear. This increase is believed to be due to electrolysis occurring when the electrode 31 is exposed to the liquid, resulting in an increase in current. On the other hand, with the insulating film 33 (graph G22), the capacitance component shows a nearly constant value regardless of frequency. In other words, it is believed that the presence of the insulating film 33 suppresses electrolysis of the electrode 31.

[0048] Fig. 6 is a plan view showing electrode 31 on which a durability test was performed. In the durability test, a predetermined AC voltage (2 V, 10 Hz) was applied to electrode 31 with saturated saline stored in fluid storage section 20. In Fig. 6, the left side shows electrode 31 without insulating film 33, and the right side shows electrode 31 with insulating film 33. Note that in both cases, protective film 40 is not provided.

[0049] 6, it can be seen that the electrode 31 is significantly damaged compared to the case without the insulating film 33 (left) and the case with the insulating film 33 (right). As is clear from this result, by forming the insulating film 33 on the surface of the electrode 31, electrolysis of the electrode 31 due to contact with a liquid can be appropriately suppressed.

[0050] In the above embodiment, the electrodes 31 are arranged so as to generate a force that separates biomolecules moving through the main channel 25 into one of the two sub-channels 27. However, the use of the electrodes is not limited to this. For example, the electrodes may be arranged so as to measure the electrical properties (dielectric spectrum, etc.) of particles in the liquid.

[0051] Although the present invention has been described in detail, the above description is merely illustrative in all respects, and the present invention is not limited thereto. It is understood that countless variations not illustrated can be envisioned without departing from the scope of the present invention. The configurations described in the above embodiments and variations can be appropriately combined or omitted as long as they are not mutually contradictory. [Explanation of symbols]

[0052] 1. Microfluidic chip 10 Substrate 20 Fluid storage section 25 Main channel 27 Subchannel 31 electrode 33 Insulating film 251 First end 252 Second end 313 Conductive Layer 315 Surface layer

Claims

1. A microfluidic chip, comprising: A substrate; An electrode disposed on one surface of the substrate; an insulating film covering one surface of the electrode and made of an oxide film obtained by oxidizing a metal contained in the electrode or a nitride film obtained by nitriding the metal; a fluid storage portion capable of storing a fluid on the one side of the insulating film; Equipped with The electrodes are arranged in the order toward the one side as follows: a conductive layer including a first metal having electrical conductivity; a surface layer including a second metal different from the first metal; Including, the insulating film is an oxide film or a nitride film of the second metal contained in the surface layer, The second metal is titanium, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound thereof.

2. A microfluidic chip, comprising: A substrate; An electrode disposed on one surface of the substrate; an insulating film covering one surface of the electrode and made of an oxide film obtained by oxidizing a metal contained in the electrode or a nitride film obtained by nitriding the metal; a fluid storage portion capable of storing a fluid on the one side of the insulating film; Equipped with The fluid storage portion has a flow path through which the fluid flows, the flow path is located on the one side of the insulating film, The flow path is a main flow path having a first end and a second end, the main flow path through which the fluid flows from the first end to the second end; a plurality of sub-flow paths connected to the second end of the main flow path and through which the fluid flows; having The electrodes apply a voltage to separate particles in the fluid flowing through the main channel into any one of the plurality of sub-channels.

3. The microfluidic chip according to claim 1 or 2, The fluid storage portion stores the fluid in a state where the fluid is in contact with the insulating film.

4. The microfluidic chip according to claim 2, The electrodes are arranged in the order toward the one side as follows: a conductive layer including a first metal having electrical conductivity; a surface layer including a second metal different from the first metal; Including, The insulating film is an oxide film or a nitride film of the second metal contained in the surface layer.

5. The microfluidic chip according to claim 4, The second metal is titanium, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound thereof.

6. The microfluidic chip according to claim 1 , The fluid storage portion has a flow path through which the fluid flows, The microfluidic chip, wherein the flow channel is located on the one side of the insulating film.

7. 7. The microfluidic chip according to claim 6, The flow path is a main flow path having a first end and a second end, the main flow path through which the fluid flows from the first end to the second end; a plurality of sub-flow paths connected to the second end of the main flow path and through which the fluid flows; having The electrodes apply a voltage to separate particles in the fluid flowing through the main channel into any one of the plurality of sub-channels.

8. A method for manufacturing a microfluidic chip, comprising the steps of: a) providing a substrate having an electrode on one surface; b) forming an insulating film, which is an oxide film or a nitride film, on the surface of the electrode on the one side by oxidizing or nitriding a metal contained in the electrode on the substrate; c) after the step b), forming a fluid storage portion capable of storing a fluid on one side of the insulating film; Including, The electrodes are arranged in the order a conductive layer including a first metal having electrical conductivity; a surface layer including a second metal different from the first metal; having The step b) is a step of forming the insulating film by oxidizing or nitriding the second metal of the surface layer, The method for manufacturing a microfluidic chip, wherein the second metal is titanium, indium, tin, copper, molybdenum, silver, chromium, tantalum, tungsten, silicon, or a metal compound thereof.

9. A method for manufacturing a microfluidic chip, comprising the steps of: a) providing a substrate having an electrode on one surface; b) forming an insulating film, which is an oxide film or a nitride film, on the surface of the electrode on the one side by oxidizing or nitriding a metal contained in the electrode on the substrate; c) after the step b), forming a fluid storage portion capable of storing a fluid on one side of the insulating film; Including, The fluid storage portion has a flow path through which the fluid flows, the flow path is located on the one side of the insulating film, The flow path is a main flow path having a first end and a second end, the main flow path through which the fluid flows from the first end to the second end; a plurality of sub-flow paths connected to the second end of the main flow path and through which the fluid flows; having The electrode applies a voltage for separating particles in the fluid flowing through the main channel into any one of the plurality of sub-channels.

10. A method for producing a microfluidic chip according to claim 8 or 9, comprising the steps of: The method for producing a microfluidic chip, wherein the step b) is a step of forming the insulating film by a thermal oxidation method or a wet oxidation method.

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