Sensor and Biomaterial Detection Method

Abstract

To provide a sensor that is excellent in selectivity for a detection object and has high sensitivity and a low detection limit, and provide a biological substance detection method.SOLUTION: A sensor has a first electrode, a second electrode, a third electrode, a semiconductor film that connects the first electrode and the second electrode to each other, and a solid electrolyte membrane that covers the first electrode, the second electrode, and the semiconductor film. The solid electrolyte membrane has an exposed surface that is exposed to the outside. The third electrode is configured to be arranged at a position where, when the exposed surface of the solid electrolyte membrane is in contact with conductive liquid, the electrode can apply an electric field to the exposed surface of the solid electrolyte membrane through the conductive liquid.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sensor and a method for detecting a biological substance.

Background Art

[0002] As methods for detecting biological substances such as mRNA / DNA in a test solution containing the biological substances, the PCR method (polymerase chain reaction) and next generation sequencing are known. The PCR method is a method of amplifying a specific region (target region) on a DNA sequence using a heat-resistant DNA polymerase, and since it can be detected from a single DNA molecule, it is possible to detect a specific DNA sequence with high sensitivity. Next generation sequencing is a method of fragmenting DNA to prepare a library and sequencing the DNA fragments of the library in parallel, and it is possible to comprehensively decode all the sequences of DNA from a single molecule. These methods for detecting biological substances take a long time for detection.

[0003] As a method for detecting biological substances such as DNA in a short time, the use of a sensor having a thin film transistor (TFT) structure has been studied. For example, a method has been reported in which a homo-oligomer DNA strand is immobilized using 3-aminopropyl ethoxysilane, and hybridization with the above oligomer strand is directly detected by displacement of the gate potential under a constant drain current (Non-Patent Document 1). Non-Patent Document 1 discloses a sensor having a thin film transistor structure in which a source electrode, a drain electrode, and a channel are covered with a dielectric.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a sensor for detecting a biological substance, a test solution as a sample is a mixture (liquid) in which biological substances other than the biological substance to be detected coexist. For this reason, in a sensor for detecting a biological substance, it is desirable to have excellent selectivity for the biological substance to be detected, high sensitivity, and a low detection limit. However, the sensor having a thin-film transistor structure described in Non-Patent Document 1 has a detection limit of about 1 μg / mL, and further improvement in sensitivity is desired. In order to improve the sensitivity of the sensor having a thin-film transistor structure, it is conceivable to remove the dielectric and expose the source electrode, drain electrode, and channel. However, when the source electrode and drain electrode are exposed, a direct current flows directly from the solution to the source electrode and drain electrode during measurement (leakage current), and the obtained data may be destabilized due to a pH change or the like resulting from an electrochemical reaction associated therewith. Further, if only the channel portion is to be exposed, there is a risk that the test solution will penetrate at the interface between the source electrode and drain electrode and the channel, resulting in a new factor of instability.

[0006] The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a sensor and a biological substance detection method having excellent selectivity for a detection target, high sensitivity, and a low detection limit.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have found that in a sensor having a thin-film transistor structure having a first electrode, a second electrode, a third electrode, and a semiconductor film connecting the first electrode and the second electrode, when the first electrode, the second electrode, and the semiconductor film are coated with a solid electrolyte film and an exposed surface exposed to the outside of the solid electrolyte film is in contact with a conductive liquid, the third electrode is arranged at a position where an electric field can be applied to the exposed surface of the solid electrolyte film through the conductive liquid. By configuring in this way, the generation of leakage current can be suppressed, and it becomes possible to detect a detection target with excellent selectivity, high sensitivity, and a low detection limit. The present invention has been completed based on this finding.

[0008] That is, in order to solve the above problems, the present invention provides the following means.

[0009] [1] A sensor having a first electrode, a second electrode, a third electrode, a semiconductor film connecting the first electrode and the second electrode, and a solid electrolyte film covering the first electrode, the second electrode, and the semiconductor film, wherein the solid electrolyte film is exposed to the outside In contact with the conductive liquid and has an exposed surface, configured to prevent the conductive liquid from coming into contact with the first electrode, the second electrode, and the semiconductor film wherein the third electrode is configured to be disposed at a position where an electric field can be applied to the exposed surface of the solid electrolyte film through the conductive liquid when the exposed surface of the solid electrolyte film is in contact with the conductive liquid.

[0010] [2] The sensor according to [1] above, wherein the first electrode, the second electrode, and the semiconductor film are disposed on one substrate.

[0011] [3] The sensor according to [2] above, wherein a conductive material film and a solid electrolyte film are laminated between the first electrode, the second electrode, and the semiconductor film and the substrate, and the first electrode, the second electrode, and the semiconductor film are disposed on the solid electrolyte film.

[0012] [4] The sensor according to [2] or [3] above, wherein the third electrode is further disposed on the substrate.

[0013] [5] The sensor according to any one of [1] to [4] above, wherein the solid electrolyte film has an ionic conductivity of 1×10 -8 S / cm or more.

[0014] [6] The solid electrolyte film is a metal oxide containing a rare earth element and zirconium (Zr) or a metal oxide containing a rare earth element and tantalum (Ta), and is an inorganic solid electrolyte film having a carbon (C) content of 0.5 atom% or more and 15 atom% or less, and a hydrogen (H) content of 2 atom% or more and 20 atom% or less. The semiconductor film is an inorganic semiconductor film that is a metal oxide containing at least indium (In). The sensor according to any one of [1] to [5] above.

[0015] [7] A probe molecule for capturing a biological substance is fixed to the exposed surface of the solid electrolyte film. The sensor according to any one of [1] to [6] above.

[0016] [8] A holding portion for holding the conductive liquid is provided around the exposed surface of the solid electrolyte film. The sensor according to any one of [1] to [7] above.

[0017] [9] A method for detecting a biological substance using the sensor according to any one of [1] to [8] above, A step of supplying a test liquid containing a biological substance to the exposed surface of the solid electrolyte film to capture the biological substance on the exposed surface; A step of replacing the test liquid with the conductive liquid; A step of applying a voltage between the third electrode and the first electrode and measuring the current between the first electrode and the second electrode; A step of obtaining the amount of the biological substance in the test liquid based on the voltage and the current. A method for detecting a biological substance.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a sensor and a method for detecting a biological substance that are excellent in selectivity for a detection target substance, highly sensitive, and have a low detection limit.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0020] Hereinafter, a sensor and a method for detecting a biological substance according to an embodiment of the present invention will be described in detail with reference to the drawings. The drawings used in the following description may sometimes show enlarged parts that are characteristic for the sake of easy understanding of the features of the present embodiment, and the dimensional ratios of each component may be different from the actual ones.

[0021] Figure 1 is a plan view showing an example of the sensor according to an embodiment of the present invention, and Figure 2 is a sectional view taken along line II-II' of Figure 1. As shown in FIGS. 1 and 2, the sensor 100 includes a substrate 11, a first electrode 21, a second electrode 22, a third electrode 23, a semiconductor film 24, and a solid electrolyte film 25. The semiconductor film 24 is disposed at a position connecting the first electrode 21 and the second electrode 22. The first electrode 21, the second electrode 22, and the semiconductor film 24 form a sensor chip 20. A conductive material film 12 and a solid electrolyte film 13 are laminated between the sensor chip 20 (the first electrode 21, the second electrode 22, and the semiconductor film 24), the third electrode 23, and the substrate 11, and the sensor chip 20 and the third electrode 23 are disposed on the solid electrolyte film 13. The solid electrolyte film 25 covers the sensor chip 20. The solid electrolyte film 25 has an exposed surface 25a exposed to the outside. The third electrode 23 is configured to be disposed at a position where an electric field can be applied to the exposed surface 25a of the solid electrolyte film 25 through the conductive liquid Lq when the exposed surface 25a of the solid electrolyte film 25 is in contact with the conductive liquid Lq. The conductive liquid Lq is a liquid having conductivity so that an electric field can be applied from the third electrode 23 to the exposed surface 25a. As the conductive liquid Lq, for example, an aqueous solution containing an inorganic salt can be used. The inorganic salt may be a substance that is substantially inert with respect to the detection target and the solid electrolyte film 25 during use, and is not particularly limited.

[0022] The exposed surface 25a of the solid electrolyte film 25 is preferably located opposite to the semiconductor film 24. The exposed surface 25a is preferably fixed with a capture substance for capturing the detection target. For example, when the detection target is a biological substance, a probe molecule for capturing the biological substance may be fixed. The exposed surface 25a and the third electrode 23 are surrounded by a holding portion 30 for holding the conductive liquid Lq.

[0023] The first electrode 21 is connected to a first terminal 21b via a first lead wire 21a. The second electrode 22 is connected to a second terminal 22b via a second lead wire 22a. The third electrode 23 is connected to a third terminal 23b via a third lead wire 23a.

[0024] As materials for the first electrode 21, the second electrode 22, and the third electrode 23, metal materials and metal oxides can be used. Examples of the metal materials include high melting point metals such as platinum (Pt) and alloys thereof. Examples of the metal oxides include indium tin oxide (ITO) and ruthenium oxide (RuO 2 ). The first electrode 21, the second electrode 22, and the third electrode 23 may each be a single layer or a multilayer formed by laminating a plurality of electrode material layers. The thickness of the first electrode 21, the second electrode 22, and the third electrode 23 may be, for example, in the range of 50 nm or more and 200 nm or less. The first lead wire 21a and the first terminal 21b may be made of the same material as the first electrode 21 and have the same thickness. The second lead wire 22a and the second terminal 22b may be made of the same material as the second electrode 22 and have the same thickness. The third lead wire 23a and the third terminal 23b may be made of the same material as the third electrode 23 and have the same thickness.

[0025] The semiconductor film 24 may be an inorganic semiconductor film or an organic semiconductor film. The inorganic semiconductor film contains an inorganic semiconductor. The inorganic semiconductor film is preferably formed only of an inorganic semiconductor. The inorganic semiconductor preferably contains at least one inorganic substance selected from the group consisting of indium oxide (In 2 O 3 ), zinc oxide (ZnO), In-Ga-Zn oxide (IGZO), In-Sn-Zn oxide (ITZO), Zn-Sn oxide (Zn-Sn-O), amorphous silicon (α-Si), low temperature polysilicon (LTPS), and graphene. These inorganic semiconductors may be used alone or in combination of two. Further, the inorganic semiconductor may be in an amorphous phase or a nanocrystalline phase.

[0026] The organic semiconductor film contains an organic semiconductor. The organic semiconductor film is preferably formed only of an organic semiconductor. The organic semiconductor is preferably a polycyclic aromatic hydrocarbon or a thienoacene-based compound.

[0027] The polycyclic aromatic hydrocarbon preferably contains four or more benzene rings. The polycyclic aromatic hydrocarbon is preferably an acene. The acene may have a substituent (for example, a phenyl group). Examples of the polycyclic aromatic hydrocarbon include pentacene and rubrene. Examples of the thienoacene-based compound include BTBT, DNTT, C8-DNTT, and C10-DNBOT. These organic semiconductors may be used alone or in combination of two kinds. The organic semiconductor may be in an amorphous phase or a nanocrystalline phase.

[0028] The semiconductor film 24 may be a single layer or a multilayer formed by laminating a plurality of semiconductor layers. The thickness of the semiconductor film 24 may be, for example, in the range of 5 nm or more and 80 nm or less. The length of the semiconductor film 24 (the distance between the first electrode 21 and the second electrode 22) is, for example, 50 μm or more and 200 μm or less. The width of the semiconductor film 24 (the length of contact with the first electrode 21 and the second electrode 22) may be, for example, in the range of 1 μm or more and 10,000 μm or less.

[0029] The solid electrolyte film 25 may be proton-conductive. The solid electrolyte film 25 may have an ionic conductivity of 1×10 -8 S / cm or more. The ionic conductivity of the solid electrolyte film 25 may be 1×10 -2 S / cm or less. The solid electrolyte film 25 may be an inorganic solid electrolyte film or an organic solid electrolyte film.

[0030] The inorganic solid electrolyte film contains an inorganic solid electrolyte. The inorganic solid electrolyte film is preferably formed only of the inorganic solid electrolyte. The inorganic solid electrolyte film can be formed of, for example, either a metal oxide containing a rare earth element and zirconium (Zr), or a metal oxide containing a rare earth element and tantalum (Ta). The carbon (C) content of the inorganic solid electrolyte film may be in the range of 0.5 atom% or more and 15 atom% or less. Further, the hydrogen (H) content of the inorganic solid electrolyte film may be in the range of 2 atom% or more and 20 atom% or less. When the inorganic solid electrolyte film is composed of the above metal oxide and the contents of both carbon (C) and hydrogen (H) are within the above ranges, the sensor 100 becomes highly sensitive and the detection limit is significantly lowered, and also the detection stability in the presence of moisture or the like is increased. From the viewpoint of further improving these characteristics, the carbon (C) content may be in the range of 1 atom% or more and 10 atom% or less, and the hydrogen (H) content may be in the range of 5 atom% or more and 18 atom% or less.

[0031] The inorganic solid electrolyte film can be formed of, for example, any one of the following (A1) to (A5). (A1) A metal oxide containing lanthanum (La) and zirconium (Zr) (A2) A metal oxide containing lanthanum (La) and tantalum (Ta) (A3) A metal oxide containing any metal element selected from the group consisting of cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y), and zirconium (Zr) or tantalum (Ta) (A4) A metal oxide containing at least one metal element selected from the group consisting of hafnium (Hf), zirconium (Zr), and aluminum (Al) (A5) A metal oxide containing lanthanum (La), hafnium (Hf), and zirconium (Zr)

[0032] For example, when the inorganic solid electrolyte film is formed of a metal oxide containing lanthanum (La) and zirconium (Zr) (Case A1), the atomic ratio of lanthanum (La) to zirconium (Zr) may be, for example, in the range of 0.43 or more and 2.33 or less, or in the range of 1.00 or more and 2.33 or less when lanthanum (La) is taken as 1. Further, when the inorganic solid electrolyte film is formed of a metal oxide containing lanthanum (La) and tantalum (Ta) (Case A2), the atomic ratio of lanthanum (La) to tantalum (Ta) is not particularly limited. Furthermore, even when the inorganic solid electrolyte film is formed of any of the metal oxides in the above (A3) to (A5), the atomic ratio of each metal element is not particularly limited. The inorganic solid electrolyte may be in an amorphous phase.

[0033] The atomic composition ratio of the above metal oxide can be determined by performing elemental analysis using Rutherford backscattering spectrometry (RBS method) or the like. Also, the contents of carbon (C) and hydrogen (H) can be determined by performing elemental analysis using Rutherford Backscattering Spectrometry (RBS analysis), Hydrogen Forward scattering Spectrometry (HFS analysis), and Nuclear Reaction Analysis (NRA analysis).

[0034] The organic solid electrolyte film contains an organic solid electrolyte. The organic solid electrolyte film is preferably formed only of the organic solid electrolyte. The organic solid electrolyte is preferably, for example, proton conductive. As the organic solid electrolyte, for example, a polymer or an organometallic complex having a proton conductive group in the side chain may be used.

[0035] The main chain of the polymer having a proton-conductive group in the side chain may be, for example, a hydrocarbon structure or a perfluorocarbon structure. The proton-conductive group may be, for example, a sulfonic acid group. As the polymer having a proton-conductive group in the side chain, Nafion (registered trademark), which is a perfluorocarbon sulfonic acid, can be used.

[0036] The organometallic complex may be, for example, a coordination polymer. The coordination polymer may be an oxalato-bridged coordination polymer represented by the following formula (1). M 2 (ox) 3 ····(1) In the above (1), M represents a divalent or trivalent metal ion. When M is a trivalent metal ion, the oxalato-bridged coordination polymer is neutral. When M contains a divalent metal ion, the oxalato-bridged coordination polymer becomes anionic, and a counter ion may be incorporated into the oxalato-bridged coordination polymer. In the above (1), ox represents an oxalate ion (C 2 O 4 2- ).

[0037] The organic solid electrolyte may be used alone or in combination of two kinds. Further, the organic solid electrolyte may be in an amorphous phase or a nanocrystalline phase.

[0038] The solid electrolyte film 25 may be a single layer or a multilayer formed by laminating a plurality of solid electrolyte layers. The thickness of the solid electrolyte film 25 may be, for example, in the range of 1 nm or more and 100 nm or less.

[0039] As the substrate 11, for example, an insulating substrate and a semiconductor substrate can be used. Examples of the insulating substrate include high heat-resistant glass, alumina (Al 2 O 3 ) substrate, STO (SrTiO) substrate, SiO 2 / Si substrate (a substrate with a SiO 2 film formed on a Si substrate), and SiO 2Examples of the multilayer substrate include a multilayer substrate in which an STO (SrTiO) layer is formed via a layer and a Ti layer. Examples of the semiconductor substrate include a Si substrate, a SiC substrate, and a Ge substrate. The thickness of the substrate 11 is, for example, 10 μm or more and 1 mm or less.

[0040] The conductive material film 12 is a conductive material film containing a conductive material. The conductive material film 12 may be formed of only a conductive material. As the conductive material, for example, a metal material and a metal oxide can be used. Examples of the metal material include platinum (Pt), gold (Au), silver (Ag), copper (Cu), aluminum (Al), molybdenum (Mo), palladium (Pd), ruthenium (Ru), iridium (Ir), tungsten (W), titanium (Ti), and alloys of these metals. Examples of the metal oxide include indium tin oxide (ITO), ruthenium oxide (RuO 2 ) can be cited.

[0041] The conductive material film 12 may be a single layer or a multilayer formed by laminating a plurality of conductive material films. The thickness of the conductive material film 12 is, for example, 50 nm or more and 200 nm or less.

[0042] The solid electrolyte film 13 may be proton conductive. The solid electrolyte film 13 may have an ionic conductivity of 1×10 -8 S / cm or more. The ionic conductivity of the solid electrolyte film 13 may be 1×10 -2 S / cm or less. The solid electrolyte film 13 may be an inorganic solid electrolyte film or an organic solid electrolyte film. Examples of the materials of the inorganic solid electrolyte film and the organic solid electrolyte film are the same as those of the solid electrolyte film 25.

[0043] The solid electrolyte film 13 may be a single layer or a multilayer formed by laminating a plurality of solid electrolyte layers. The thickness of the solid electrolyte film 13 is, for example, in the range of 50 nm or more and 300 nm or less.

[0044] The material of the holding part 30 may be organic or inorganic. Examples of organic materials include polyimide and epoxy resin. Examples of inorganic materials include alumina and silica. The height of the holding part 30 may be, for example, in the range of 0.10 mm or more and 5 mm or less.

[0045] Next, a method for detecting a biological substance using the sensor 100 will be described. FIG. 3 is a schematic diagram for explaining a method for detecting a biological substance using the biological substance detection sensor shown in FIG. 1. (a) is an enlarged cross-sectional view of the biological substance detection sensor taken along line II-II' in FIG. 1, and (b) is an enlarged view of (a). In FIG. 3, a probe molecule 1 for capturing a biological substance is fixed to the exposed surface 25a inside the holding part 30 of the sensor 100.

[0046] The detection of the biological substance using the sensor 100 is performed as follows. First, the biological substance 2 to be detected is captured by the probe molecule 1 fixed to the exposed surface 25a of the sensor 100. Specifically, a test solution containing the biological substance 2 is injected into the holding part 30 of the sensor 100 to supply the test solution to the exposed surface 25a of the solid electrolyte film 25. Thereby, the biological substance 2 to be detected is captured by the exposed surface 25a via the probe molecule 1. The biological substance 2 is, for example, a nucleic acid such as DNA or mRNA. The probe molecule 1 is DNA or mRNA that is complementary to a part of those biological substances 2.

[0047] After the biological substance 2 is captured by the exposed surface 25a, the test solution is replaced with the conductive liquid Lq. Specifically, first, the exposed surface 25a is washed with a cleaning solution to remove, for example, biological substances (biological substances not to be detected) not captured by the probe molecule 1 or biological substances captured non-specifically. Next, the conductive liquid Lq is injected into the holding part 30 of the sensor 100 to bring the third electrode 23 into contact with the exposed surface 25a in the conductive liquid Lq. As the conductive liquid Lq, for example, phosphate buffer (PBS) can be used. Thereby, the third electrode 23 can apply an electric field to the exposed surface 25a through the conductive liquid.

[0048] Next, a voltage V is applied between the first electrode 21 and the second electrode 22. SD is applied between the first electrode 21 and the third electrode 23, and a voltage V TG In the sensor 100 of this embodiment, the electric field created by the charge of the biological material 2 captured on the exposed surface 25a via the probe molecule 1 is transmitted to the semiconductor film 24, causing a change in the electrical characteristics of the semiconductor film 24. Therefore, a voltage V SD When an electric field of SD This voltage V SD and current I SD From this relationship, the amount of the biological material 2 captured by the probe molecule 1 can be quantified, and the amount of the biological material in the test liquid can be obtained.

[0049] The sensor 100 can be manufactured, for example, as follows. (1) Deposition of the conductive material film 12 First, a substrate 11 (e.g., SiO 2 On the silicon substrate (Si substrate), a conductive material film 12 is formed. The conductive material film 12 can be formed by sputtering.

[0050] (2) Formation of solid electrolyte membrane 13 Next, the solid electrolyte membrane 13 is formed on the conductive material membrane 12. The solid electrolyte membrane 13 can be formed, for example, by applying a solid electrolyte membrane precursor solution onto the conductive material membrane 12 and heating the resulting coating film. As the solid electrolyte membrane precursor solution, a liquid in which the material of the solid electrolyte constituting the solid electrolyte membrane 13 is dissolved or dispersed can be used. As a method for applying the solid electrolyte membrane precursor solution, for example, a spin coating method, an inkjet printing method, a nanoimprint method, or the like can be used. There is no particular limitation on the heating temperature of the coating film as long as it is a temperature at which the solvent of the solid electrolyte membrane precursor solution volatilizes and the solid electrolyte membrane 13 is formed.

[0051] (3) Deposition of semiconductor film 24 Next, a semiconductor film 24 is formed on the solid electrolyte film 13. The semiconductor film 24 can be formed, for example, as follows. First, a resist film patterned by photolithography is formed on the solid electrolyte film 13. Next, a precursor solution for the semiconductor film is applied onto the solid electrolyte film 13 on which the resist film is formed, and the resulting coated film is heated to form the semiconductor film. Thereafter, the resist film is removed. As the precursor solution for the semiconductor film, a liquid in which the material of the semiconductor constituting the semiconductor film 24 is dissolved or dispersed can be used. As the coating method for the precursor solution for the semiconductor film, for example, a spin coating method, an inkjet printing method, a nanoimprint method, etc. can be used. The heating temperature of the coated film is not particularly limited as long as the solvent of the precursor solution for the semiconductor film volatilizes and the semiconductor film 24 is formed.

[0052] (4) Formation of the electrode pattern Next, an electrode pattern (first electrode 21, first lead wire 21a, first terminal 21b, second electrode 22, second lead wire 22a, second terminal 22b, third electrode 23, third lead wire 23a, third terminal 23b) is formed on the solid electrolyte film 13 and the semiconductor film 24. The electrode pattern can be formed, for example, as follows. First, a resist film patterned by photolithography is formed on the solid electrolyte film 13 and the semiconductor film 24. Next, an electrode film is formed on the solid electrolyte film 13 and the semiconductor film 24 on which the resist film is formed. Thereafter, the resist film is removed. As the method for forming the electrode film, for example, a sputtering method can be used.

[0053] (5) Formation of the solid electrolyte film 25 Next, a solid electrolyte film 25 is formed on the sensor piece 20 (the first electrode 21, the second electrode 22, and the semiconductor film 24). The solid electrolyte film 25 can be formed, for example, as follows. First, a resist film is formed on the first terminal 21b, the second terminal 22b, and the third electrode 23. Next, a precursor solution for the solid electrolyte film is applied, and the obtained coating film is heated to form a solid electrolyte film. Then, the resist film is removed. As the precursor solution for the solid electrolyte film, a liquid in which the material of the solid electrolyte constituting the solid electrolyte film 25 is dissolved or dispersed can be used. As the coating method of the precursor solution for the solid electrolyte film, for example, a spin coating method, an inkjet printing method, a nanoimprint method, or the like can be used. The heating temperature of the coating film is not particularly limited as long as the solvent of the precursor solution for the solid electrolyte film volatilizes and the solid electrolyte film 25 is formed.

[0054] In the above-described sensor 100, the third electrode 23 is formed on the solid electrolyte film 13 of the substrate 11, but the position of the third electrode 23 is not limited thereto. The third electrode 23 may be disposed at a position other than on the solid electrolyte film 13 as long as it is configured to be able to apply an electric field to the exposed surface 25a of the solid electrolyte film 25 through the conductive liquid Lq when the exposed surface 25a of the solid electrolyte film 25 is in contact with the conductive liquid Lq.

[0055] FIG. 4 is a plan view showing another example of a sensor according to an embodiment of the invention, and FIG. 5 is a schematic diagram for explaining a biological substance detection method using the sensor shown in FIG. 4. FIG. 5(a) is a cross-sectional view of the sensor taken along the line V-V' of FIG. 4, and FIG. 5(b) is an enlarged view of FIG. 5(a).

[0056] The sensor 101 shown in FIGS. 4 and 5 includes a substrate 11, a first electrode 21, a second electrode 22, a third electrode 23, a semiconductor film 24, and a solid electrolyte film 25. A conductive material film 12 and a solid electrolyte film 13 are laminated between the sensor chip 20 (the first electrode 21, the second electrode 22, and the semiconductor film 24) and the substrate 11, and the sensor chip 20 and the third electrode 23 are disposed on the solid electrolyte film 13. The sensor 101 is configured such that the third electrode 23 is separated from the substrate 11 and a part of the third electrode 23 is immersed in a conductive liquid Lq held by a holding portion 30. Other configurations are the same as those of the above-described sensor 100. Therefore, the same reference numerals are used for the same or similar parts in the sensor 101 shown in FIGS. 4 and 5 and the above-described sensor 100, and the description thereof is omitted.

[0057] Detection of a biological substance using the sensor 101 can be performed as follows. First, as in the case of the above-described sensor 100, a test liquid containing the biological substance 2 is supplied to the exposed surface 25a of the solid electrolyte film 25, and the biological substance 2 is captured on the exposed surface 25a via the probe molecule 1. Next, the test liquid is replaced with the conductive liquid Lq.

[0058] A part of the third electrode 23 is immersed in the conductive liquid Lq injected into the holding portion 30 of the sensor 101. Thereby, the third electrode 23 can apply an electric field to the exposed surface 25a via the conductive liquid. The first electrode 21 and the second electrode 22 are connected to a first voltage supply unit 31, and the first electrode 21 and the third electrode 23 are connected to a second voltage supply unit 32. Quantification of the biological substance 2 captured by the probe molecule 1 can be performed in the same manner as in the case of the sensor 100 shown in FIGS. 1 to 3. That is, a voltage V SD is applied between the first electrode 21 and the second electrode 22 using the first voltage supply unit 31, and a voltage V TG is applied between the first electrode 21 and the third electrode 23 using the second voltage supply unit 32. Thereby, the current I SD flowing between the first electrode 21 and the second electrode 22 changes. Then, this voltage V SD and the current I SDFrom this relationship, the amount of the biological material 2 captured by the probe molecule 1 can be quantified, and the amount of the biological material in the test liquid can be obtained.

[0059] According to the sensors 100 and 101 of the present embodiment configured as described above, a voltage V SD is applied between the first electrode 21 and the third electrode 23, and a voltage V TG When an electric field is applied to the semiconductor film 24 through the solution and the solid electrolyte, a current I flows between the first electrode 21 and the second electrode 22. SD Since the strength of the electric field applied to the semiconductor film 24 varies depending on the amount of the biological material 2 captured on the exposed surface 25a, the sensors 100 and 101 of the present embodiment detect the voltage V SD and current I SD From the relationship, the biological material 2 captured on the exposed surface 25a can be quantified selectively and with high sensitivity. Furthermore, in the sensors 100 and 101 of the present embodiment, the first electrode 21, the second electrode 22, and the semiconductor film 24 are covered with the solid electrolyte film 25, so that when an electric field is applied from the third electrode 23 to the exposed surface 25a of the solid electrolyte film 25 via the test liquid Lq, the generation of a leak current is suppressed. By suppressing the generation of this leak current, the aforementioned instability caused by the leak current can be suppressed, and detection with higher sensitivity and lower detection limit becomes possible.

[0060] In the sensors 100 and 101 of this embodiment, since the solid electrolyte film 25 is a solid electrolyte, a larger amount of charge can be induced in the semiconductor film than if the solid electrolyte film 25 were made of an insulator or dielectric material, and a current I SD , and the mutual conductance (gm) is also large. As a result, the sensitivity is increased and the detection limit is lowered. Furthermore, since the electric field created by the charge of the biological material 2 can be collected at the semiconductor film 24 from a wider range, not just directly above the semiconductor film 24, through the solid electrolyte film 25, it becomes possible to detect the detection target with higher sensitivity and the detection limit is lowered. In particular, when the ionic conductivity of the solid electrolyte film 25 is 1×10 -8 When the thickness is 1.0 S / cm or more, these effects are more significantly observed.

[0061] In the sensors 100 and 101 of the present embodiment, when the solid electrolyte film 25 is a metal oxide containing a rare earth element and zirconium (Zr) or a metal oxide containing a rare earth element and tantalum (Ta), and the carbon (C) content is 0.5 atom% or more and 15 atom% or less, and the hydrogen (H) content is 2 atom% or more and 20 atom% or less, the electric field generated by the charge of the biological substance 2 captured on the exposed surface 25a is likely to be transmitted to the semiconductor film 24. Further, when the semiconductor film 24 is an inorganic semiconductor film containing at least indium (In), the amount of change in electrical characteristics due to the transmission of the electric field becomes large. Therefore, the detection target can be detected with higher sensitivity, and the detection limit becomes lower.

[0062] In the sensors 100 and 101 of the present embodiment, when the probe molecule 1 for capturing the biological substance 2 is fixed to the exposed surface 25a of the solid electrolyte film 25, the selectivity for the detection target is further improved.

[0063] Since the biological substance detection method of the present embodiment uses the above-described sensors 100 and 101, it is possible to detect the detection target with excellent selectivity, high sensitivity, and a low detection limit.

[0064] As described above in detail regarding the embodiments of the present invention, the present invention is not limited to the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. For example, in the present embodiment, a biological substance is exemplified as the detection target, but the present invention is not limited thereto. The sensors 100 and 101 of the present embodiment can detect any substance as long as it can transmit an electric field to the semiconductor film 24 by being captured on the exposed surface 25a of the solid electrolyte film 25. As the detection target, for example, an ionic substance having a charge or a substance that generates a charge by being captured on the exposed surface 25a can be used. The detection target may be an organic substance or an inorganic substance.

[0065] In addition, in the present embodiment, as a configuration for improving the selectivity of the detection target captured on the exposed surface 25a, a configuration in which the probe molecule 1 is fixed to the exposed surface 25a of the solid electrolyte film 25 has been described as an example, but the present invention is not limited thereto. For example, the exposed surface 25a may be coated with a selective permeation membrane so that only the substance that has permeated through the selective permeation membrane is captured on the exposed surface 25a.

[0066] In addition, in the present embodiment, a case where the conductive material film 12 and the solid electrolyte film 13 are laminated in this order between the sensor chip 20 (the first electrode 21, the second electrode 22, and the semiconductor film 24) and the substrate 11 has been described as an example, but the present invention is not limited thereto. For example, the sensor chip 20 may be directly disposed on the substrate 11. Further, only the solid electrolyte film 13 may be disposed between the sensor chip 20 and the substrate 11.

Example

[0067] [Example 1 of the present invention] (Film formation of conductive material film) On a silicon substrate, a silicon oxide (SiO 2 ) film with a thickness of 500 nm was formed to prepare a SiO 2 / Si substrate. On the silicon oxide film of this SiO 2 / Si substrate, a 10-nm-thick Ti layer and a 200-nm-thick Pt layer were formed in this order by sputtering to form a conductive material film having a two-layer structure of Pt / Ti.

[0068] (Film formation of solid electrolyte film) Next, a solid electrolyte film was formed on the Pt layer of the obtained conductive material film by the sol-gel method. First, a La 0.3 Zr 0.7 O solution was applied as a precursor solution for the solid electrolyte film by spin coating to form a precursor layer for the solid electrolyte film. Next, the precursor layer for the solid electrolyte film was pre-fired at 250°C in an oxygen-containing atmosphere and then main-fired at 400°C to obtain a La 0.3 Zr 0.7A solid electrolyte membrane composed of O was formed. The carbon (C) and hydrogen (H) contents of the obtained solid electrolyte membrane were measured by Rutherford backscattering spectroscopy, hydrogen forward scattering analysis, and nuclear reaction analysis, respectively. As a result, the water content of carbon (C) was 2.0 atom%, and the hydrogen (H) content was 10.1 atom%. Also, the ionic conductivity of the solid electrolyte membrane was measured using an alternating current impedance measuring device (manufactured by Biologic, SP-300). As a result, the ionic conductivity was 6.0×10 -7 S / cm.

[0069] Note that the La 0.3 Zr 0.7 O solution was prepared as follows. Lanthanum acetate trihydrate and zirconium butoxide were mixed at a ratio of 3:7 (molar ratio), and the obtained mixture was dissolved in propionic acid so as to have a concentration of 0.2 mol / kg in terms of La 0.3 Zr 0.7 O. The obtained mixed solution was refluxed in an oil bath at 110°C for 30 minutes and then filtered through a membrane filter with a pore size of 0.2 μm to obtain a 0.2 mol / kg La 0.3 Zr 0.7 O solution.

[0070] (Film formation of semiconductor film) Next, an In 2 O 3 solution was spin-coated on the solid electrolyte membrane to form a precursor layer for the semiconductor film. Then, the precursor layer for the semiconductor film was sintered at 250°C to form an inorganic semiconductor film composed of In 2 O 3 . After that, In 2 O 3 was processed into a channel shape by dry etching. The size of the semiconductor film was 300 μm in width × 50 μm in length × 20 nm in thickness. Note that the In 2 O 3 solution was prepared as follows. Indium nitrate trihydrate was used to prepare In 2 O 3It was dissolved in 2-methoxyethanol so that the concentration was 0.2 mol / kg in terms of conversion. After refluxing the obtained solution in an oil bath at 110 °C for 30 minutes, it was filtered through a membrane filter with a pore size of 0.2 μm to obtain an In 2 O 3 solution with a concentration of 0.2 mol / kg.

[0071] (Formation of the first electrode and the second electrode) On the solid electrolyte membrane and the semiconductor membrane, a resist membrane patterned in the shapes of the source electrode and the drain electrode was formed by photolithography. Next, on the solid electrolyte membrane and the semiconductor membrane on which the resist membrane was formed, an ITO layer with a thickness of 50 nm and an Au layer with a thickness of 500 nm were successively formed by sputtering, and then the resist membrane was removed. The first electrode, the first lead wire, the first terminal, the second electrode, the second lead wire, and the second terminal having a two-layer structure of Au / ITO were formed. The sizes of the first electrode and the second electrode were each 320 μm in width × 200 μm in length, and the distance between the first electrode and the second electrode was 50 μm.

[0072] (Film formation of the solid electrolyte film) After forming a resist membrane on the first terminal and the second terminal, a La 0.3 Zr 0.7 O solution was applied by spin coating to form a precursor layer for the solid electrolyte film. Next, the precursor layer for the solid electrolyte film was pre-fired at 250 °C in an oxygen-containing atmosphere and then fired at 400 °C to form a solid electrolyte film composed of La 0.3 Zr 0.7 O with a thickness of 20 nm. After that, the resist membrane was removed. When the carbon (C) and hydrogen (H) content rates of the obtained solid electrolyte film were measured by Rutherford backscattering spectrometry, hydrogen forward scattering analysis method, and nuclear reaction analysis method respectively, the water content rate of carbon (C) was 2.0 atom%, and the content rate of hydrogen (H) was 10.1 atom%. Thus, a sensor (the sensor shown in Fig. 4) was fabricated in which the first electrode, the second electrode, the semiconductor membrane, and the solid electrolyte film covering them were formed on the solid electrolyte membrane of the laminate.

[0073] [Comparative Example 1] A sensor was fabricated in the same manner as in Example 1 of the present invention, except that the solid electrolyte film was not formed.

[0074] [Comparative Example 2] A sensor was fabricated in the same manner as in Example 1 of the present invention, except that a resist film was formed using a photoresist (TSMR, manufactured by Tokyo Ohka Kogyo Co., Ltd.) instead of the solid electrolyte film.

[0075] [Evaluation] For the sensor fabricated in Example 1 of the present invention, a holding portion (5 mm × 10 mm) was formed around the solid electrolyte film covering the semiconductor film. For the sensor fabricated in Comparative Example 1, a holding portion (5 mm × 10 mm) was formed on the first and second electrodes around the semiconductor film. For the sensor fabricated in Comparative Example 2, a holding portion (5 mm × 10 mm) was formed on the photoresist film electrode around the semiconductor film. 0.01x phosphate buffer (PBS) was injected as a conductive liquid into the holding portion of the sensor. Next, the third electrode was immersed in the PBS in the holding portion of the sensor, and while applying a voltage V TG between the first electrode and the third electrode, the current value I G flowing through the third electrode and the I SD flowing between the first electrode and the second electrode were measured. The voltage V TG was changed from 0.2 V to 0.8 V, and the V TG -I g curve and the V TG -I SD curve were obtained. The V TG -I g curve is shown in Fig. 6(a), and the V TG -I SD curve is shown in Fig. 6(b).

[0076] From the graph in Fig. 6(a), for the sensor of Example 1 of the present invention in which the first electrode, the second electrode, and the semiconductor film are covered with the solid electrolyte film and the sensor of Comparative Example 2 in which the first electrode, the second electrode, and the semiconductor film are covered with the resist film, as the voltage V TG increases, the current value I GIt can be seen that there is almost no change in the amount of change. On the other hand, in the sensor of Comparative Example 1 in which the first electrode, the second electrode, and the semiconductor film are not coated with a solid electrolyte film, the current value I TG also increases due to the increase in the voltage V G . The current value I G is the leakage current value in which the current flowing from the first electrode to the second electrode leaks to the third electrode. Therefore, from the graph of FIG. 6(a), it can be seen that the sensor of Example 1 of the present invention significantly suppresses the generation of leakage current as compared with the sensor of Comparative Example 1.

[0077] Also, from the graph of FIG. 6(b), the sensor of Example 1 of the present invention has a larger current value I TG at each voltage V SD compared with the sensor of Comparative Example 1, and also has a large change amount of the current value I TG due to the increase in the voltage V SD . For example, when the voltage V TG is 0.8 V, the current value I SD of the sensor of Example 1 of the present invention is about 1.5 times higher at 480 μA than 310 μA of the sensor of Comparative Example 1. Therefore, the sensor of Example 1 of the present invention has a higher gm and can perform highly sensitive measurement as compared with the sensor of Comparative Example 1. On the other hand, the sensor of Comparative Example 2 has a lower current value I TG at each voltage V SD compared with the sensor of Comparative Example 1, and thus it can be seen that the gm is lower and the sensitivity is also lower as compared with the sensor of Comparative Example 1.

[0078] [Example 2 of the present invention] Using the sensor fabricated in Example 1 of the present invention, Escherichia coli was detected as follows.

[0079] (Fixation of probe DNA) A wall portion was provided around the solid electrolyte film covering the semiconductor film of the sensor to form a holding portion (5 mm × 10 mm). Next, a DNA having complementarity with a part of 16s-rRNA of Escherichia coli was immobilized on the exposed surface in the holding portion of the sensor as a probe DNA. The sequence of the probe DNA is shown in Table 1 below.

[0080]

Table 1

[0081] The probe DNA was immobilized on the holding part of the sensor according to the procedure shown in Fig. 7. First, 3-aminopropyltriethoxysilane (APTES) was bonded to the holding part (solid electrolyte film 25). Next, one aldehyde group of APTES and one aldehyde group of glutaraldehyde were reacted to bond APTES and glutaraldehyde. And finally, the other aldehyde group of glutaraldehyde and the probe DNA were reacted to immobilize 100 nmol / L of the probe DNA.

[0082] (Preparation of test solution) Escherichia coli and an aqueous solution of sodium dodecyl sulfate (SDS) with a concentration of 1% by mass were mixed to prepare a test solution. In the test solution, the cell wall and nuclease of Escherichia coli were destroyed, and DNA and mRNA were released. As the test solution, those with Escherichia coli concentrations of 10 and 1×10 4 cells / μL were prepared.

[0083] (Detection of Escherichia coli) 2 μL of the test solution was dropped onto the holding part of the sensor and incubated at room temperature for 5 minutes. Next, the test solution was removed from the holding part of the sensor, and pure water was poured into the holding part to wash the exposed surface of the solid electrolyte film. Then, 0.01× phosphate buffer (PBS) was poured into the holding part as the conductive liquid to replace the test solution with 0.01× PBS. Next, the third electrode was immersed in the PBS of the holding part of the sensor, and while applying a voltage V TG between the first electrode and the third electrode, I SD flowing between the first electrode and the second electrode was measured. The voltage V TG was changed from 0.2 V to 0.8 V, and a V TG -I SD curve was obtained. The results are shown in Fig. 8. Also, 0.01× PBS was poured into the holding part of the sensor without dropping the test solution, and similarly, V TG -I SDA curve was obtained. The results are shown in Fig. 8.

[0084] From the graph of Fig. 8, it can be seen that the change in the current value I TG due to the increase in the voltage V SD varies depending on the number of E. coli in the test solution. When compared with the case using 0.01×PBS without E. coli, when using a test solution containing E. coli, the change in the current value I TG due to the increase in the voltage V SD is significantly reduced.

[0085] [Example 3 of the present invention] Using the sensor fabricated in Example 1 of the present invention, the DNA measurement sensitivity was evaluated as follows. In the same manner as in Example 2 of the present invention, DNA having complementarity with a part of 16s-rRNA of E. coli was immobilized on the exposed surface in the holding part of the sensor as probe DNA. Next, 2 μL of a test solution with a concentration of E. coli DNA of 0.047 μg / mL was dropped onto the holding part of the sensor and incubated at room temperature for 10 minutes. Then, the test solution was removed from the holding part of the sensor, and pure water was poured into the holding part to wash the exposed surface of the solid electrolyte film. Thereafter, 0.01×PBS was poured into the holding part as a conductive liquid to replace the test solution with 0.01×PBS. Next, in the same manner as in Example 2 of the present invention, the third electrode was immersed in the PBS in the holding part of the sensor, and while applying a voltage V TG between the first electrode and the third electrode, I SD flowing between the first electrode and the second electrode was measured. Similarly, it was performed using a test solution (blank) with a concentration of E. coli DNA of 0 μg / mL. The results are shown in Fig. 9.

[0086] From the graph of Fig. 9, it can be seen that the values of I TG for each V SD are different between the case using a test solution (blank) with a concentration of E. coli DNA of 0 μg / mL and the case using a test solution with a concentration of E. coli DNA of 0.047 μg / mL. Thus, it can be seen that the sensor fabricated in Example 1 of the present invention has a detection limit for E. coli DNA lower than 0.047 μg / mL.

Explanation of symbols

[0087] 1 Probe molecule 2 Biomaterial 11 Substrate 12 Conductive material film 13 Solid electrolyte membrane 21 First electrode 22 Second electrode 23 Third electrode 24 Semiconductor film 25 Solid electrolyte film 25a Exposed surface 30 Holding part 31 First voltage supply part 32 Second voltage supply part 100, 101 Sensor

Claims

1. A sensor having a first electrode, a second electrode, a third electrode, a semiconductor film connecting the first electrode and the second electrode, and a solid electrolyte film covering the first electrode, the second electrode, and the semiconductor film, wherein the solid electrolyte film has an exposed surface that is exposed to the outside and contacts a conductive liquid, and is configured to prevent the conductive liquid from contacting the first electrode, the second electrode, and the semiconductor film, wherein the third electrode is arranged at a position where an electric field can be applied to the exposed surface of the solid electrolyte film through the conductive liquid when the exposed surface of the solid electrolyte film is in contact with the conductive liquid.

2. The sensor according to claim 1, wherein the first electrode, the second electrode, and the semiconductor film are arranged on one substrate.

3. The sensor according to claim 2, wherein a conductive material film and a solid electrolyte film are laminated between the first electrode, the second electrode, and the semiconductor film and the substrate, and the first electrode, the second electrode, and the semiconductor film are arranged on the solid electrolyte film.

4. The sensor according to claim 2 or 3, wherein the third electrode is further arranged on the substrate.

5. The solid electrolyte film has an ionic conductivity of 1×10 －８ S / cm or more, and the sensor according to any one of claims 1 to 4.

6. The sensor according to any one of claims 1 to 5, wherein the solid electrolyte film is a metal oxide containing a rare earth element and zirconium (Zr) or a metal oxide containing a rare earth element and tantalum (Ta), and has a carbon (C) content of 0.5 atom% or more and 15 atom% or less, and a hydrogen (H) content of 2 atom% or more and 20 atom% or less. The semiconductor film is an inorganic semiconductor film that is a metal oxide containing at least indium (In).

7. The sensor according to any one of claims 1 to 6, wherein a probe molecule for capturing a biological substance is fixed to the exposed surface of the solid electrolyte film.

8. The sensor according to any one of claims 1 to 7, further comprising a holding portion for holding the conductive liquid around the exposed surface of the solid electrolyte film.

9. A method for detecting a biological substance using the sensor according to any one of claims 1 to 8, comprising a step of supplying a test liquid containing a biological substance to the exposed surface of the solid electrolyte film to capture the biological substance on the exposed surface, and a step of replacing the test liquid with the conductive liquid. A step of applying a voltage between the third electrode and the first electrode and measuring a current between the first electrode and the second electrode; A step of obtaining the amount of a biological substance in the test solution based on the voltage and the current, the biological substance detection method comprising the steps.

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