WO2025169976A1 - Device, concentration measurement apparatus provided with same, and concentration measurement method using same - Google Patents

Abstract

[Problem] The present invention provides a device that can be used for a concentration measurement apparatus and a concentration measurement method, with which it is possible to selectively detect an object to be detected in a test subject and to accurately detect the presence or absence of a specific object to be detected and the concentration thereof with small energy. [Solution] Provided is a device that has an insulating substrate, at least one insulating composite layer, and a retainer part in which a test subject can be retained, wherein: the insulating composite layer has a pair of electrodes and a semiconductor layer which is in contact with the pair of electrodes; the retainer part has an ionization part for ionizing an object to be detected in the test subject; and an ion capturing part for capturing the ionized object to be detected is provided between the insulating composite layer and the retainer part.

Description

Device, concentration measuring apparatus including the same, and concentration measuring method using the same

The present invention relates to a device in which the magnitude of the current flowing between a pair of electrodes and a threshold voltage _Vth , which is the voltage value of a third electrode when current flows between the pair of electrodes, change depending on the concentration of an analyte in a test sample. More specifically, the present invention relates to a concentration measurement apparatus and a concentration measurement method for measuring the concentration of an analyte in a test fluid based on changes in the magnitude of the current and the threshold voltage _Vth .

Society 5.0, the coming super-smart society, aims to achieve both economic development and the resolution of social issues, and the IoT that will support this will require sensors to collect data.

BACKGROUND ART Electrochemical sensors using semiconductors have been known as a method for detecting the presence or absence and concentration of specific components in gas.
10 , a conventional gas sensor 200 has a configuration including a pair of electrodes 241, 242 on an insulating substrate 212 and a semiconductor layer 244 in contact with the pair of electrodes 241, 242. In such gas sensor 200, upon contact with a gas that is an analyte, the analyte in the analyte is adsorbed to the semiconductor layer 244, causing a change in the resistance value of the semiconductor layer 244. By measuring this change in the resistance value of the semiconductor layer 244, it is possible to detect the presence or absence and concentration of the analyte in the analyte.

Tin oxide ( _SnO2 ) is generally used as the semiconductor layer 244 of such a gas sensor 200. However, the tin oxide semiconductor layer 244 adsorbs any gas molecules, and therefore has low selectivity for the target substance to be detected, making it impossible to accurately detect the presence or concentration of a specific target substance in some cases.

In some gas sensors, an insulating film is formed on the semiconductor layer 244 to protect it, but insulating films also adsorb any gas molecules, resulting in low selectivity for the target substance.

Furthermore, with such gas sensors, accurate detection can be difficult because the change in the resistance value of the semiconductor layer 244 is small. In such cases, one approach is to increase the change in the resistance value of the semiconductor layer 244 by heating the semiconductor layer 244 to increase its temperature, but this requires a mechanism to heat the semiconductor layer 244 and increases the energy required for measurement.

In light of this current situation, the present invention aims to provide a device that can be used in a concentration measurement apparatus and concentration measurement method that can selectively detect a target substance in a test sample and accurately detect the presence or absence and concentration of a specific target substance using low energy.

The present invention was invented to solve the problems of the prior art described above, and the device, concentration measurement apparatus equipped with the device, and concentration measurement method using the device of the present invention include those configured as follows:

[1] A device having an insulating substrate, at least one insulating composite layer, and a storage portion capable of storing an analyte,
the insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes;
the storage unit has an ionization unit that ionizes the target substance in the test sample,
The device further comprises an ion trapping section between the insulating composite layer and the reservoir section, the ion trapping section trapping the ionized target substance.

[2] The semiconductor layer is composed of an oxide containing indium (In), zinc (Zn), and an additional element (X),
The device according to [1], wherein the additional element (X) includes at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb).

[3] The device described in [1] or [2], wherein the ion-trapping portion is an ionophore.

[4] The device described in any one of [1] to [3], wherein the ionization section includes a gas-permeable membrane.

[5] The device described in any one of [1] to [4], wherein the ionization portion is gel-like.

[6] The device described in [1] or [2], wherein the ion capture section and the ionization section are composed of an ionic liquid.

[7] The device described in [6], wherein the ionic liquid is contained in a liquid-retaining sheet.

[8] The device described in [1] or [2], wherein the ionization portion is a solid electrolyte having an electrode catalyst.

[9] The device described in any one of [1] to [6], wherein the ionization portion is a liquid and further includes a third electrode in contact with the liquid.

[10] The device described in any one of [1] to [8], further comprising a third electrode formed on the insulating substrate in a state insulated from the insulating composite layer.

[11] The device according to any one of [1] to [10], wherein the field-effect mobility of the semiconductor layer is 20 cm ² /Vs or more.

[12] The device according to any one of [1] to [11], wherein the OFF current between the pair of electrodes of the semiconductor layer is 1×10 ⁻¹² A or less.

[13] A device according to any one of [1] to [12],
a control device;
The control device
a voltage applying means for applying a voltage between the pair of electrodes;
a current measuring means for measuring a current flowing between the pair of electrodes when a voltage is applied by the voltage applying means;
and a concentration calculation means for calculating the concentration of the target substance in the specimen based on the inter-electrode current measured by the current measurement means.

[14] The device according to [9] or [10],
a control device;
The control device
a voltage application means for varying a voltage applied between the electrode into which a current flows out of the pair of electrodes and the third electrode;
a current measuring means for measuring a current flowing between the pair of electrodes;
a threshold voltage detection means for detecting a threshold voltage Vth, which is a voltage value of the third electrode when a current flows between the pair of electrodes, based on a voltage value applied by the voltage application means and a current value _measured by the current measurement means;
and a concentration calculation means for calculating the concentration of the target substance in the specimen based on the threshold voltage _Vth detected by the threshold voltage detection means.

[15] A concentration measurement method for detecting the concentration of an analyte in a test sample using the device according to any one of [1] to [12],
A concentration measurement method comprising measuring an inter-electrode current, which is a current value flowing between the pair of electrodes when a voltage is applied between the pair of electrodes, and measuring the concentration of an analyte in the test sample based on the inter-electrode current.

[16] A concentration measurement method for detecting the concentration of an analyte in a test sample using the device according to [9] or [10],
A concentration measurement method comprising detecting a threshold voltage _Vth , which is a voltage value of the third electrode when a current flows between the pair of electrodes, and measuring a concentration of an analyte in the test sample based on the threshold voltage _Vth .

According to the present invention, the analyte in the test sample is ionized by the ionization unit, which can then be captured by an ion capture unit that can selectively capture specific ions, such as ionophores or ionic liquids, thereby enabling the analyte in the test sample to be selectively detected.

FIG. 1 is a schematic diagram for explaining the configuration of a concentration measuring device according to this embodiment. FIG. 2 is a schematic diagram for explaining the configuration of a device used in the concentration measuring apparatus of FIG. FIG. 3 is a schematic diagram showing a modified example of a device used in the concentration measuring apparatus shown in FIG. FIG. 4 is a schematic diagram showing another modified example of the device used in the concentration measuring apparatus shown in FIG. FIG. 5 is a graph showing the results of measuring the concentration of a specimen using the concentration measuring device shown in FIG. FIG. 6 is a schematic diagram for explaining the configuration of another embodiment of the concentration measuring device of the present invention. FIG. 7 is a graph showing the results of measuring the concentration of a specimen using the concentration measuring device shown in FIG. FIG. 8 is a schematic front view showing a modified example of the device used in the concentration measuring apparatus shown in FIG. FIG. 9 is a schematic side view of the device shown in FIG. FIG. 10 is a schematic diagram for explaining the configuration of a conventional gas sensor.

Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a schematic diagram for explaining the configuration of a concentration measuring apparatus according to this embodiment, and FIG. 2 is a schematic diagram for explaining the configuration of a device used in the concentration measuring apparatus of FIG.

In this embodiment, the "analyte" refers to the substance to be detected in the analyte, and unless otherwise specified, the state of the substance is not limited, and it may be gas, liquid, or solid, as long as it is ionizable.

Furthermore, in this specification, the term "third electrode" includes both the reference electrode and the gate electrode.

As shown in FIG. 1, the concentration measurement device 50 of this embodiment includes a device 10 having an insulating substrate 12, at least one insulating composite layer 14, and a storage section 16 capable of storing an analyte, and a control device 60.

The device 10 configured as shown in FIG. 2 may also be a semiconductor element such as a field effect transistor (FET) or a metal oxide semiconductor field effect transistor (MOSFET).

The insulating substrate 12 is a substrate made of an insulating material such as glass or ceramics.

The insulating composite layer 14 has a pair of electrodes (a first electrode 141 and a second electrode 142) and a semiconductor layer 144 in contact with the pair of electrodes 141, 142.

The storage section 16 is not particularly limited as long as it is configured to store the analyte, but in this embodiment, as described below, it is configured by a partition section 16a that surrounds the ion trapping section 18 so that the ionization section 17 provided within the storage section 16 comes into contact with the ion trapping section 18.

The storage section 16 contains an ionization section 17 that ionizes the target substance in the sample. The ionization section 17 is not particularly limited as long as it can ionize the target substance, and a solvent such as water can be used, for example. The ionization section 17 may use a solvent in its liquid form, but gelling it prevents the ionization section 17 from leaking from the storage section 16, making the concentration measurement device 50 easier to handle. The ionization section 17 can also be a solid electrolyte with an electrode catalyst. In this configuration, the target substance in the sample is ionized by the electrode catalyst, and the solid electrolyte conducts only specific ions, allowing the ion capture section 18 to capture only the target ions.

In addition, an ion trapping portion 18 is provided between the insulating composite layer 14 and the storage portion 16 .
The ion-trapping unit 18 has selectivity for the target substance in the specimen. Specifically, it has the property of selectively trapping ions of the target substance. As such an ion-trapping unit 18, for example, an ionophore such as a lithium ionophore, a potassium ionophore, a sodium ionophore, a calcium ionophore, an ammonium ionophore, an ionophore for chloride ions, or a magnesium ionophore can be used.

The method for manufacturing such an ion-trapping portion 18 is not particularly limited, but for example, when an ionophore is used, the ion-trapping portion 18 can be manufactured by the following steps.
First, polyvinyl chloride is weighed into a beaker. Here, it is preferable to use polyvinyl chloride with a degree of polymerization of about 1050 from the viewpoints of easy handling and smooth application to the insulating composite layer 14.

Next, add tetrahydrofuran as a solvent to the beaker and stir with a stirrer until the polyvinyl chloride dissolves.

Once the polyvinyl chloride has dissolved, add the plasticizer, ionophore, an anion scavenger if the substance being measured is a cation, or a cation scavenger if the substance being measured is an anion, and then stir the mixture.

As the plasticizer, for example, 2-nitrophenyl octyl ether (NPOE), bis(2-ethylhexyl) sebacate, etc. can be used.
In addition, for example, potassium tetrakis(4-chlorophenyl)borate can be used as an anion scavenger, and tridodecylmethylammonium chloride (TDDMACl) can be used as a cation scavenger.

The ionophore can be appropriately selected depending on the ion to be detected. For example, dibenzyl-14-crown-4 or TTD-14-crown-4 can be used to detect lithium ions (Li ⁺ ), bis(benzo-15 ^- crown-5) can be used to detect potassium ions (K ^{+ ), bis(12-crown-4) can be used to detect sodium ions (Na +} ), HDOPP-Ca can be used to detect calcium ions (Ca ²⁺ ), nonactin can be used to detect ammonium ions (NH ₄ ⁺ ), Bisthiourea-1 can be used to detect chloride ions (Cl ^- ), and C14-K22B5, K22B1B5, or K22B9 can be used to detect magnesium ions (Mg ²⁺ ).

Then, the solution prepared in this manner is spread on a glass petri dish and air-dried to create the ion-trapping portion 18. From the perspective of increasing the response speed (establishment of ion diffusion equilibrium), it is effective to make the ion-trapping portion 18 thinner; in this case, it is preferable to create the ion-trapping portion 18 by spin coating.

The ion trapping section 18 thus created is cut to an appropriate size and attached to the insulating composite layer 14, taking care not to trap air. The storage section 16 is then glued onto the attached ion trapping section 18 using, for example, epoxy resin, thereby completing the device 10.

The insulating composite layer 14 includes an insulating film 146 at least at a location in contact with the ion trapping section 18. The insulating film 146 also serves as a protective layer for protecting the semiconductor layer 144 from the analyte and the ionization section 17. By providing the insulating film 146, corrosion of the semiconductor layer 144 can be prevented, and the durability and reliability of the semiconductor layer 144 can be improved. Any known insulating material can be used for the insulating film 146, and corrosion-resistant materials are preferred. Examples of insulating materials include _Ta2O5 , _Si3N4 , and _SiO2 , and the thickness _thereof is preferably 0.01 μm or more _and 0.5 μm or less, and more preferably 0.03 μm or more and 0.2 μm or less.

Furthermore, the semiconductor layer 144 preferably has a field effect mobility of 20 cm ² /Vs or more, and more preferably 60 cm ² /Vs or more.

Such semiconductor layer 144 is composed of an oxide containing indium (In), zinc (Zn), and an additional element (X), where the additional element (X) is at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb).

Specifically, it is preferable that the atomic ratio of In and X satisfy the following formula (1) (X in the formula is the sum of the content ratios of the additive elements. The same applies to formulas (2) and (3) below).
0.4≦(In+X)/(In+Zn+X)≦0.8 (1)
With regard to Zn, it is preferable that the atomic ratio expressed by the following formula (2) is satisfied.
0.2≦Zn/(In+Zn+X)≦0.6 (2)
It is preferable that X satisfies the atomic ratio expressed by the following formula (3).
0.001≦X/(In+Zn+X)≦0.015 (3)

When the atomic ratios of In, Zn, and X satisfy formulas (1) to (3), the semiconductor layer 144 exhibits the field-effect mobility and OFF current described above.

In order for the semiconductor layer 144 to exhibit higher field-effect mobility and lower OFF current, it is more preferable that the atomic ratios of In, Zn, and X satisfy formula (1-2), formula (2-2), or formula (3-2).
0.43≦(In+X)/(In+Zn+X)≦0.79 (1-2)
0.21≦Zn/(In+Zn+X)≦0.57 (2-2)
0.0015≦X/(In+Zn+X)≦0.013 (3-2)

It is more preferable that the atomic ratios of In, Zn and X satisfy the formula (1-3), formula (2-3) or formula (3-3).
0.48≦(In+X)/(In+Zn+X)≦0.78 (1-3)
0.22≦Zn/(In+Zn+X)≦0.52 (2-3)
0.002<X/(In+Zn+X)≦0.012 (3-3)

It is more preferable that the atomic ratio of In, Zn and X satisfy the formula (1-4), formula (2-4) or formula (3-4).
0.53≦(In+X)/(In+Zn+X)≦0.75 (1-4)
0.25≦Zn/(In+Zn+X)≦0.47 (2-4)
0.0025≦X/(In+Zn+X)≦0.010 (3-4)

It is more preferable that the atomic ratios of In, Zn and X satisfy the formula (1-5), formula (2-5) or formula (3-5).
0.58≦(In+X)/(In+Zn+X)≦0.70 (1-5)
0.30≦Zn/(In+Zn+X)≦0.42 (2-5)
0.003≦X/(In+Zn+X)≦0.009 (3-5)

As mentioned above, the additive element (X) is one or more elements selected from Ta, Sr, and Nb. These elements can be used alone, or two or more elements can be used in combination. The additive element (X) may contain elements other than Ta, Sr, and Nb, but preferably contains only these elements.

Furthermore, the thinner the semiconductor layer 144, the greater the change in conductivity of the surface layer, which results in a greater change in the moving charge as described below, improving measurement accuracy. The thickness of such semiconductor layer 144 is preferably 0.5 μm or less, more preferably 0.1 μm or less, and particularly preferably 0.05 μm or less. There is no particular lower limit for the thickness of semiconductor layer 144, but it is generally 0.005 μm or more.

Furthermore, it is preferable that the surface 144a of the semiconductor layer 144 facing the ion-trapping section 18 is as smooth as possible. If the surface 144a of the semiconductor layer 144 is not smooth, for example, gaps may form between the insulating film 146 or the insulating film 146 may be discontinuous, reducing the adhesion between the insulating film 146 and the ion-trapping section 18 and making it impossible to accurately capture potential changes from the ion-trapping section 18. This reduces measurement accuracy and makes operation unstable.

Specifically, the maximum height Sz of the surface 144a of the semiconductor layer 144 is preferably 0.05 μm or less, more preferably 0.01 μm or less, and most preferably 0.003 μm or less. There is no particular lower limit for this maximum height Sz, but it is generally 0.0005 μm or more. Furthermore, the arithmetic mean height Sa of the surface 144a of the semiconductor layer 144 on the ion trapping section 18 side is preferably 0.03 μm or less, more preferably 0.005 μm or less, and most preferably 0.002 μm or less. There is no particular lower limit for this arithmetic mean height Sa, but it is generally 0.0002 μm or more.

Here, the maximum height Sz and the arithmetic mean height Sa are surface roughness parameters defined in ISO 25178, and such parameters can be measured, for example, using a 3D surface roughness profiler (NexView, manufactured by Zygo). In this case, the measurement conditions are preferably as follows:

Measurements are made in accordance with ISO 25178 using a 50x objective lens, a 20x zoom lens, and a measurement range of 89μm x 87μm. A roughness curve with a range of 3μm x 3μm is extracted from the obtained three-dimensional surface shape. The analysis program "Mx" attached to the 3D surface roughness profile measuring instrument is then used to correct the roughness curve using the following correction conditions, and the maximum height Sz and arithmetic mean height Sa are calculated.

<Correction conditions>
-Remove:Form Remove
-Filter Type: Spline
-Filter: Low Pass
-Type: Gaussian Spline Auto

When forming the device 10 described above as an FET structure, it can be formed using the same method as conventionally known FETs and MOSFETs. For example, a conductive metal thin film can be formed on the insulating substrate 12 as the first electrode 141 and the second electrode 142 using a sputtering device, and then a thin oxide film having the above-described configuration can be formed as the semiconductor layer 144 using a sputtering device. A shadow mask can be used for patterning the first electrode 141 and the second electrode 142 and the semiconductor layer 144.

The conductive metal used as the first electrode 141 and the second electrode 142 is not particularly limited, but may be, for example, molybdenum (Mo) or tungsten (W), or an alloy of these metals with cerium oxide (CeO ₂ ), copper (Cu), silver (Ag), or the like.

Next, a ceramic thin film can be deposited thereon to form the insulating film 146. Specifically, for example, a plasma CVD apparatus such as Samco Corporation's PD-2202L can be used to deposit a SiOx thin film under the following conditions: film formation gas: SiH ₄ /N ₂ O/N ₂ mixed gas, film formation pressure: 110 Pa, and substrate temperature: 250°C to 400°C, to form the insulating film 146.

In addition, the control device 60 of the concentration measuring device 50 of this embodiment is equipped with a variable voltage source 32 (voltage application means) for applying a voltage between the first electrode 141 and the second electrode 142, and an ammeter 36 (current measurement means) for measuring the current value between the first electrode 141 and the second electrode 142.

The control device 60 has a computer equipped with a calculation means, a memory means, an input/output means, etc., and is configured to control the applied voltage of the variable voltage source 32 and measure the current value using the ammeter 36 based on a program stored in the memory means.

The control device 60 further includes an inter-electrode current detection means 61. The inter-electrode current detection means 61 is configured to control the voltage applied by the variable voltage source 32 and to receive the current value measured by the ammeter 36 as an electrical signal. Such inter-electrode current detection means 61 can be realized by a computer incorporated into the control device 60, for example.

The interelectrode current detection means 61 detects the interelectrode current Ids flowing between the first electrode 141 and the second electrode 142 using the ammeter 36 while a predetermined voltage _Vds is applied between the first electrode 141 and the second electrode 142 by the variable voltage source ₃₂ .

Here, the predetermined voltage _Vds is not particularly limited as long as it is large enough to allow a current to flow through the semiconductor layer 144. In this embodiment, since the predetermined voltage _Vds only needs to be a constant voltage, a constant voltage source can be used instead of the variable voltage source 32.

The magnitude of the inter-electrode current _Ids detected in this manner correlates with the amount of ions trapped by the ion trapping unit 18, i.e., the concentration of the analyte in the test sample. Therefore, for example, by creating a calibration curve showing the relationship between the concentration of the analyte and the inter-electrode current _Ids in advance, the concentration of the analyte can be determined based on the inter-electrode current _Ids measured using the concentration measuring device 50.

Alternatively, by performing machine learning using the correlation between the concentration of the object to be detected and the inter-electrode current I _ds as training data, it is possible to use artificial intelligence (AI) to determine the concentration of the object to be detected based on the inter-electrode current I _ds measured using the concentration measuring device 50.

The control device 60 of this embodiment further includes a concentration calculation means 64, which is configured to calculate the concentration of the detection target, as described above, based on the interelectrode current _Ids detected by the interelectrode current detection means 61. Such concentration calculation means 64 can be realized by a computer incorporated in the control device 60, etc.

FIG. 3 is a schematic diagram showing a modified example of the device 10 used in the concentration measuring apparatus 50 shown in FIG.
This concentration measuring device 50 has basically the same configuration as the concentration measuring device 50 shown in FIGS. 1 and 2, so the same components are given the same reference numerals and detailed description thereof will be omitted.

In the concentration measuring device 50 of this embodiment, the ionization unit 17 has a gas-permeable membrane 17a. The gas-permeable membrane 17a has the property of selectively allowing only the desired gas to pass through. An example of such a gas-permeable membrane 17a is polydimethylsiloxane (PDMS).

By configuring it in this way, even when the analyte is a gas containing multiple components, the gas-permeable membrane 17a allows only the gas containing the target substance to pass through, improving selectivity for the target substance and enabling more accurate detection of the presence or absence and concentration of the target substance in the sample.

FIG. 4 is a schematic diagram showing another modified example of the device 10 used in the concentration measuring apparatus 50 shown in FIG.
This concentration measuring device 50 has basically the same configuration as the concentration measuring device 50 shown in FIGS. 1 and 2, so the same components are given the same reference numerals and detailed description thereof will be omitted.

In the concentration measuring device 50 of this embodiment, the ionization unit 17 and the ion trapping unit 18 are made of an ionic liquid 19 .
In this way, by providing ionic liquid 19 in storage section 16, when a test sample is introduced into storage section 16, ionic liquid 19 ionizes the target substance in the test sample and captures the ionized target substance, thereby making it possible to measure the concentration of the target substance in the test sample, similar to the embodiment shown in Figures 1 and 2.

The ionic liquid 19 can be selected appropriately depending on the ions to be detected, and examples include [EMIM] and [BF4].

Such ionic liquid 19 may remain in liquid form, but by gelling it or incorporating the ionic liquid 19 into a liquid-retaining sheet such as filter paper, the ionic liquid 19 will not leak from the reservoir 16, making the concentration measuring device 50 easier to handle.

Example 1
FIG. 5 is a graph showing the results of measuring the concentration of a specimen using the concentration measuring device 50 shown in FIG.

In this example, NH3 _- containing gas and _{C2H5OH -} containing gas were used as specimens, and _{the NH3 concentration and C2H5OH concentration were} measured between 0 ppm and 1000 ppm. Note that [EMIM][BF4] was used as the ionic liquid 19, and measurements were performed with _NH3 as the detection target.

As shown in Figure 5, it was confirmed that for the NH3 _- containing gas, the inter-electrode current _Ids changes with changes in the _NH3 concentration, whereas for _{the C2H5OH -} containing gas, the inter-electrode current _Ids does not change even when the _C2H5OH concentration changes.

From this, it was confirmed that by measuring the inter-electrode current I _ds using the concentration measuring device 50 of this embodiment, it is possible to detect the presence or absence and concentration of a specific detection target.

FIG. 6 is a schematic diagram for explaining the configuration of another embodiment of the concentration measuring device of the present invention.
This concentration measuring device 50 basically has the same configuration as the concentration measuring device 50 shown in FIGS. 1 to 5, so the same components are given the same reference numerals and detailed description thereof will be omitted.

In the concentration measuring device 50 of this embodiment, the ionization unit 17 is a liquid, and the device further includes a reference electrode 161 as a third electrode that is in contact with the ionization unit 17 that is a liquid.
The control device 60 also includes a variable voltage source 34 (voltage application means) for applying a voltage between the first electrode 141 and the reference electrode 161, and a voltmeter 38 (voltage measurement means) for measuring the voltage value between the first electrode 141 and the reference electrode 161.

In this embodiment, the control device 60 has a computer equipped with a calculation means, a memory means, an input/output means, etc., and is configured to control the applied voltage of the variable voltage source 32 and the variable voltage source 34, measure current values using the ammeter 36, and measure voltage values using the voltmeter 38 based on a program stored in the memory means.

The control device 60 further includes a threshold voltage detection means 62. The threshold voltage detection means 62 is configured to control the voltages applied by the variable voltage sources 32 and 34, and to receive the current and voltage values measured by the ammeter 36 and voltmeter 38 as electrical signals. Such a threshold voltage detection means 62 can be realized by a computer incorporated into the control device 60, for example.

The threshold voltage detection means 62 gradually increases the voltage Vg applied between the first electrode 141 and the reference electrode 161 by the variable voltage source 34 while applying a predetermined voltage _Vds between the first electrode 141 and the second electrode 142 by the variable voltage source 32. Then, the threshold voltage detection means 62 measures the threshold voltage _Vth by detecting a change in the current _Id flowing between the first electrode 141 and the second electrode 142 by the ammeter 36 and detecting a change in the voltage _Vg between the first electrode 141 and the reference electrode ₁₆₁ by the voltmeter 38.

In this case, in device 10 having the configuration described above, when the voltage applied to reference electrode 161 is set to be equal to or less than the threshold voltage _Vth , the semiconductor layer 144 preferably has an OFF current, which is the current flowing from first electrode 141 to second electrode 142 or the current flowing from second electrode 142 to first electrode 141, of 1× ¹⁰ A or less, and more preferably 1× ¹⁰ A or less. Such a small OFF current makes it possible to detect the threshold voltage _Vth with higher accuracy even if a small voltage is applied between the first electrode 141 and the second electrode 142 when detecting the threshold voltage _Vth , as will be described later.

In the device 10 configured as described above, it is known that the threshold voltage _Vth varies depending on the amount of analyte ions trapped in the ion-trapping unit 18. Therefore, by measuring this threshold voltage _Vth , the concentration of the analyte contained in the specimen can be detected.

The method for measuring the threshold voltage _Vth is not particularly limited, and may involve detecting the voltage _Vg when the current _Id starts to flow between the first electrode 141 and the second electrode 142, or gradually reducing the voltage _Vg from a state in which the current _Id is flowing and detecting the voltage _Vg when the current _Id stops flowing. A conventionally known method may be used, such as changing the voltage _Vg and determining the value of _Vds when the current _Id reaches a predetermined value (e.g., 1× ¹⁰ A) as the threshold voltage _Vth . However, from the viewpoint of more accurate measurement, it is preferable to keep the voltage _Vds constant, apply a voltage _Vg within a predetermined range, measure the current _Id that flows at that time, calculate an approximate line of _√Id with respect to _Vg within the predetermined range using the least squares method, and determine the value of _Vg when _√Id = 0 on the approximate line as the threshold voltage _Vth .

Since there is a correlation between the threshold voltage _Vth measured in this manner and the concentration of the target substance, for example, by creating in advance a calibration curve showing the relationship between the concentration of the target substance and the threshold voltage _Vth , it is possible to determine the concentration of the target substance based on the threshold voltage _Vth measured using the concentration measuring device 50.

Alternatively, by performing machine learning using teacher data in which the concentration of the object to be detected and the threshold voltage _Vth are associated with each other, it is possible to use artificial intelligence (AI) to determine the concentration of the object to be detected based on the threshold voltage _Vth measured using the concentration measuring device 50.

The concentration calculation means 64 of this embodiment is configured to calculate the concentration of the detection target, as described above, based on the threshold voltage _Vth detected by the threshold voltage detection means 62. Such concentration calculation means 64 can be realized by a computer incorporated in the control device 60, etc.

Example 2
FIG. 7 is a graph showing the results of measuring the concentration of a specimen using the concentration measuring device 50 shown in FIG.

In this example, an _NH3- containing gas was used as the analyte, and the _NH3 concentration was measured between 0 ppm and 10 ppm. Water was used as the ionization unit 17, and ammonium ionophore was used as the ion trapping unit 18, and the measurement was performed with _NH3 as the detection target.

FIG. 7(a) shows the results of the threshold voltage _Vth detected when the NH ₃ concentration was 0 ppm to 0.5 ppm, and FIG. 7(b) shows the results of the threshold voltage Vth detected when the NH ₃ concentration was 1 ppm to 10 ppm.

7(a) and 7(b), it was confirmed that the threshold voltage _Vth changes with the change in _NH3 concentration. From this, it was confirmed that the presence or absence and concentration of a specific detection target can be detected by measuring the threshold voltage _Vth using the concentration measurement device 50 of this embodiment.

FIG. 8 is a schematic front view showing a modified example of the device 10 used in the concentration measuring apparatus 50 shown in FIG. 6, and FIG. 9 is a schematic side view of the device 10 shown in FIG.
This concentration measuring device 50 basically has the same configuration as the concentration measuring device 50 shown in FIGS. 1 to 6, so the same components are given the same reference numerals and detailed description thereof will be omitted.

In the concentration measuring device 50 of this embodiment, as shown in Figures 8 and 9, a gate electrode layer 13 is provided between the insulating substrate 12 and the insulating composite layer 14. The gate electrode layer 13 has a gate electrode 131, which is a third electrode formed on the insulating substrate 12, and an insulating film 132 for insulating between the gate electrode 131 and the insulating composite layer 14.

Even when the gate electrode layer 13 is provided in this manner, similar to the concentration measuring device 50 shown in FIG. 6 , the threshold voltage _Vth can be measured by detecting a change in the voltage _Vg between the first electrode 141 and the gate electrode 131 using the voltmeter 38, and the concentration of the object to be detected can be obtained based on the threshold voltage _Vth .

The above describes a preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications are possible without departing from the scope of the present invention.

10 Device 12 Insulating substrate 13 Gate electrode layer 131 Gate electrode 132 Insulating film 14 Insulating composite layer 141 First electrode 142 Second electrode 144 Semiconductor layer 144a Surface 146 Insulating film 16 Reservoir 16a Partition 161 Reference electrode 17 Ionization section 17a Gas permeable membrane 18 Ion trapping section 19 Ionic liquid 32 Variable voltage source 34 Variable voltage source 36 Ammeter 38 Voltmeter 50 Concentration measuring device 60 Control device 61 Inter-electrode current detection means 62 Threshold voltage detection means 64 Concentration calculation means

Claims (16)

A device having an insulating substrate, at least one insulating composite layer, and a reservoir capable of storing an analyte,
the insulating composite layer has a pair of electrodes and a semiconductor layer in contact with the pair of electrodes;
the storage unit has an ionization unit that ionizes the target substance in the test sample,
The device further comprises an ion trapping section between the insulating composite layer and the reservoir section, the ion trapping section trapping the ionized target substance. the semiconductor layer is composed of an oxide containing indium (In), zinc (Zn) and an additional element (X),
The device of claim 1 , wherein the additional element (X) includes at least one element selected from tantalum (Ta), strontium (Sr), and niobium (Nb). The device of claim 1, wherein the ion-trapping moiety is an ionophore. The device described in claim 1, wherein the ionization portion includes a gas-permeable membrane. The device described in claim 1, wherein the ionization portion is gel-like. The device described in claim 1, wherein the ion capture section and the ionization section are composed of an ionic liquid. The device described in claim 6, wherein the ionic liquid is contained in a liquid-retaining sheet. The device described in claim 1, wherein the ionization portion is a solid electrolyte having an electrode catalyst. The device described in claim 1, wherein the ionization portion is a liquid and further comprises a third electrode in contact with the liquid. The device described in claim 1, further comprising a third electrode formed on the insulating substrate and insulated from the insulating composite layer. 10. The device of claim 1, wherein the semiconductor layer has a field effect mobility of 20 cm ^<2> /Vs or greater. 2. The device according to claim 1, wherein the OFF current between the pair of electrodes of the semiconductor layer is 1×10 ⁻¹² A or less. A device according to any one of claims 1 to 12;
a control device;
The control device
a voltage applying means for applying a voltage between the pair of electrodes;
a current measuring means for measuring a current flowing between the pair of electrodes when a voltage is applied by the voltage applying means;
and a concentration calculation means for calculating the concentration of the target substance in the specimen based on the inter-electrode current measured by the current measurement means. A device according to claim 9 or 10;
a control device;
The control device
a voltage application means for varying a voltage applied between the electrode into which a current flows out of the pair of electrodes and the third electrode;
a current measuring means for measuring a current flowing between the pair of electrodes;
a threshold voltage detection means for detecting a threshold voltage Vth, which is a voltage value of the third electrode when a current flows between the pair of electrodes, based on a voltage value applied by the voltage application means and a current value _measured by the current measurement means;
and a concentration calculation means for calculating the concentration of the target substance in the test sample based on the threshold voltage _Vth detected by the threshold voltage detection means. A concentration measurement method for detecting a concentration of an analyte in a test specimen using the device according to any one of claims 1 to 12, comprising:
A concentration measurement method comprising measuring an inter-electrode current, which is a current value flowing between the pair of electrodes when a voltage is applied between the pair of electrodes, and measuring the concentration of an analyte in the test sample based on the inter-electrode current. A concentration measurement method for detecting a concentration of an analyte in a test specimen using the device according to claim 9 or 10, comprising:
A concentration measurement method comprising detecting a threshold voltage _Vth , which is a voltage value of the third electrode when a current flows between the pair of electrodes, and measuring a concentration of an analyte in the test sample based on the threshold voltage _Vth .