Evaluation method for sensor systems and sensor elements

Abstract

To provide a sensor system which enables evaluation of the quality of a sensor element, and a method of evaluating the sensor element.SOLUTION: A sensor system is provided, comprising a sensing unit, probe molecules provided on a surface of the sensing unit, a sensor element comprising first and second electrodes electrically connected to the sensing unit, and a processing unit configured to apply a voltage between the first and second electrodes to evaluate the quality of the sensor element from electrical characteristics of the sensor element.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] Embodiments of the present invention relate to a sensor system and a method for evaluating a sensor element.

Background Art

[0002] For example, a sensor element in which the surface of graphene is functionalized with probe molecules has been proposed, but an inspection system for detecting defective elements has not been established.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Embodiments of the present invention aim to provide a sensor system and a method for evaluating a sensor element that can evaluate the quality of the sensor element.

Means for Solving the Problems

[0005] According to an embodiment of the present invention, a sensor system includes a sensor element having a sensing portion, probe molecules located on the surface of the sensing portion, a first electrode and a second electrode electrically connected to the sensing portion, and a processing device that applies a voltage between the first electrode and the second electrode and evaluates the quality of the sensor element from the electrical characteristics of the sensor element.

[0006] According to an embodiment of the present invention, a method for evaluating a sensor element evaluates the quality of the sensor element from the electrical characteristics of the sensor element in which probe molecules are located on the surface of the sensing portion and a voltage is applied between a first electrode and a second electrode electrically connected to the sensing portion.

Brief Description of the Drawings

[0007] [Figure 1] This is a schematic diagram of the sensor system according to the embodiment. [Figure 2] This is a schematic diagram of the sensor unit according to the embodiment. [Figure 3] (a) is the Id-Vg characteristic curve for a good element, and (b), (c), and (d) are schematic diagrams showing the state of the probe molecule at points b, c, and d in Figure 3(a), respectively. [Figure 4] (a) is the Id-Vg characteristic curve for the defective element, and (b), (c), and (d) are schematic diagrams showing the state of the probe molecule at points b, c, and d in Figure 4(a), respectively. [Figure 5] This graph shows the measurement results of ΔId for samples 1-5. [Modes for carrying out the invention]

[0008] Each embodiment will be described below with reference to the drawings. Drawings are schematic or conceptual, and the relationships between the thickness and width of each part, as well as the ratios of the sizes of different parts, are not necessarily identical to those of reality. Even when representing the same part, the dimensions and ratios may differ between drawings. Furthermore, identical or similar elements are assigned the same symbol.

[0009] As shown in Figure 1, the sensor system of the embodiment comprises a sensor unit 30 and a processing unit 100. The processing unit 100 includes, for example, an arithmetic unit such as a CPU, a memory device, a power supply device that generates a voltage to be applied to the sensor unit 30, and a device for reading the electrical characteristics of the sensor unit 30. The processing unit 100 processes the input signal and controls the operation of the sensor unit 30, for example, according to software stored in the memory device. The processing unit 100 determines whether the sensor element 50 is good or bad.

[0010] As shown in Figure 2, the sensor unit 30 has a sensor element 50. The sensor element 50 has a sensing part 20, a probe molecule 32, a first electrode 41, and a second electrode 42. The sensing part 20 is electrically sensitive to the proximity of a target molecule. For example, the sensing part 20 contains graphene, and the sensor element 50 has a GFET (graphene field effect transistor) structure. In addition to graphene, other materials such as carbon nanotubes can also be used as the sensing part 20.

[0011] The sensing element 20, the first electrode 41, and the second electrode 42 are supported on the substrate 10. The substrate 10 is, for example, a silicon substrate. The sensing element 20 can be provided on the substrate 10 via an underlayer. For example, a silicon oxide film can be used as the underlayer. The underlayer can also be made to function as a chemical catalyst for graphene formation.

[0012] The first electrode 41 can function as the drain electrode in the FET, and the second electrode 42 can function as the source electrode in the FET. The first electrode 41 and the second electrode 42 are electrically connected to the sensing unit 20. When a voltage is applied between the first electrode 41 and the second electrode 42 by the power supply 44, a current (drain current) Id flows between the first electrode 41 and the second electrode 42 through the sensing unit 20. The sensor system may include a measuring device 45 for measuring the drain current Id.

[0013] The probe molecule 32 is located on the surface of the sensing part 20. The location of the probe molecule 32 on the surface of the sensing part 20 means that the probe molecule 32 is bound, adsorbed, or in close proximity to the surface of the sensing part 20 by chemical, charge-induced attraction, π-π interaction, cation-π interaction, or hydrophobic interaction, thereby constraining the probe molecule 32 to the surface of the sensing part 20. The probe molecule 32 includes, for example, at least one of the following biomolecules: a protein, peptide, antibody, DNA aptamer, or a derivative thereof. The probe molecule 32 can be located on the surface of the sensing part 20 via, for example, a linker (or scaffold molecule) 33. For example, pyrene can be used as the linker 33.

[0014] As described later, a solution containing the sample atmosphere is supplied to the surface of the sensing unit 20. Alternatively, the sample atmosphere may be supplied to the surface of the sensing unit 20 as a gas phase. The probe molecule 32 is capable of specifically recognizing target molecules that may be present in the sample atmosphere, or of specifically interacting with target molecules. When the probe molecule 32 recognizes or captures a target molecule, the target molecule comes into close proximity to the surface of the sensing unit 20, and the electronic state of the sensing unit 20 changes due to the charge of the target molecule or the structural change of the probe molecule 32 due to capturing the target molecule. By detecting this as a change in the drain current Id, the presence and concentration of target molecules in the sample atmosphere can be determined.

[0015] The processing unit 100 controls the power supply 44 and applies a voltage between the first electrode 41 and the second electrode 42. The processing unit 100 also evaluates the quality of the sensor element 50 based on its electrical characteristics obtained by the measuring device 45. This allows for the removal of defective elements and suppresses false detection of the presence or concentration of target molecules in the sample atmosphere.

[0016] The following describes specific examples of the electrical characteristics and quality evaluation methods for the sensor element 50.

[0017] The sensor system of the embodiment can further include a first liquid supply mechanism that supplies the liquid 31 to the surface of the sensing unit 20, and a gate electrode 43 that applies a voltage to the liquid 31 supplied to the surface of the sensing unit 20. The first liquid supply mechanism will be described later with reference to FIG. 1.

[0018] As shown in FIG. 2, the surface of the sensing unit 20 and the probe molecules 32 are immersed in the liquid 31. Thereby, when the probe molecules 32 are molecules derived from a living body, the ability of the probe molecules 32 to capture target molecules can be improved. The liquid 31 is, for example, an aqueous solution, and more specifically, a buffer solution.

[0019] The first electrode 41 and the second electrode 42 are, for example, coated with an insulating film (not shown), and the first electrode 41 and the second electrode 42 are not in direct contact with the liquid 31.

[0020] When the drain current described above is Id and the voltage of the gate electrode 43 is Vg, the Id-Vg characteristics can be used as an electrical characteristic that serves as an index for evaluating the quality of the sensor element 50.

[0021] An example of the Id-Vg characteristics is shown in FIGS. 3(a) and 4(a).

[0022] The processing device 100 evaluates the quality of the sensor element 50 by comparing, for example, the first Id-Vg characteristic I (solid line) when Vg is swept from a negative voltage to a positive voltage and the second Id-Vg characteristic II (dashed line) when Vg is swept from a positive voltage to a negative voltage.

[0023] For example, the second electrode 42 is grounded, and a voltage of 5 mV is applied from the power supply 44 to the first electrode 41. In this state, Id when the voltage Vg of the gate electrode 43 is swept in 10 mV steps from -500 mV to +350 mV is measured to obtain the first Id-Vg characteristic I, and Id when it is swept in 10 mV steps from +350 mV to -500 mV is measured to obtain the second Id-Vg characteristic II.

[0024] Figure 3(a) shows an example of the Id-Vg characteristics in a good element, and Figure 4(a) shows an example of the Id-Vg characteristics in a defective element. In the defective element, it was observed that the difference in Id ΔId between the first Id-Vg characteristic I and the second Id-Vg characteristic II, when Vg is the same value, tended to be larger than the ΔId of the good element.

[0025] Therefore, the processing unit 100 can evaluate the quality of the sensor element 50 from the difference ΔId of Id when Vg is the same value in the first Id-Vg characteristic I and the second Id-Vg characteristic II. The processing unit 100 can output the quality of the sensor element 50 through an interface (not shown). When the processing unit 100 evaluates the sensor element 50 as good, it executes a sensing operation using the sensor element 50. When the processing unit 100 evaluates the sensor element 50 as defective, it does not execute a sensing operation using the sensor element 50 or stops the sensing operation.

[0026] ΔId was measured for five samples, 1-5. The results are shown in Figure 5. In each sample, the sensor element had a GFET structure using graphene as the sensing element. Cocaine aptamers (nucleic acid aptamers capable of specifically recognizing or specifically interacting with cocaine molecules) were used as probe molecules. The graphene surface and the probe molecules were immersed in phosphate-buffered saline.

[0027] The difference in Id ΔId when Vg is 0mV was measured between the first Id-Vg characteristic I and the second Id-Vg characteristic II, which were measured under the conditions described above. The ΔId for sample 1 was 0.0009μA, for sample 2 it was 0.0036μA, for sample 3 it was 0.068μA, for sample 4 it was 0.090μA, and for sample 5 it was 0.15μA.

[0028] After measuring the ΔId values ​​as described above, methyl benzoate was dissolved in phosphate-buffered saline for each of the samples 1-5. The molar concentration of methyl benzoate in this solution was 100 μM. Samples 1 and 2 showed a significant change in Id before and after the addition of methyl benzoate, indicating a response to methyl benzoate. Therefore, samples 1 and 2 can be considered good devices. Samples 3-5 did not show a significant change in Id before and after the addition of methyl benzoate, indicating no response to methyl benzoate. Therefore, samples 3-5 can be considered defective devices.

[0029] As shown in Figure 5 above, the quality of the sensor element can be evaluated based on the magnitude of ΔId in the first Id-Vg characteristic I and the second Id-Vg characteristic II. For example, in the example in Figure 5, ΔId = 0.04 μA can be set as the threshold for quality determination. The processing unit 100 compares the threshold stored in the storage device 200 with the measured ΔId, and determines that the element is good if ΔId is 0.04 μA or less, or less than 0.04 μA, and determines that the element is defective if ΔId is greater than 0.04 μA. Preferably, ΔId = 0.01 μA can be set as the threshold for quality determination. If even greater accuracy is required, ΔId = 0.006 μA can be set as the threshold for quality determination.

[0030] Figure 4(a), which shows the Id-Vg characteristics for a defective element, shows that the ΔId between the first Id-Vg characteristic I and the second Id-Vg characteristic II when Vg is 0 or negative is greater than the ΔId between the first Id-Vg characteristic I and the second Id-Vg characteristic II when Vg is positive. Therefore, the processing unit 100 can improve the accuracy of its quality determination by evaluating the quality of the sensor element 50 from the difference ΔId of Id when Vg is 0 or negative.

[0031] The minimum value of the Id-Vg characteristic is the charge neutral point (CNP), which is the point where the carriers (electrons or holes) contributing to conduction change. As shown in Figure 4(a), the difference between the first Id-Vg characteristic I and the second Id-Vg characteristic II becomes large in the region where Vg is lower than the value at the charge neutral point. Therefore, it is preferable to evaluate the quality of the sensor element 50 from ΔId in the region where Vg is lower than the value at the charge neutral point.

[0032] Furthermore, the processing unit 100 may evaluate the quality of the sensor element 50 from the difference ΔVg between the first Id-Vg characteristic I and the second Id-Vg characteristic II when Id is the same value. As a threshold for determining quality, ΔVg = 10mV when Id = 1μA can be set. If ΔVg is 10mV or less, or less than 10mV, it can be determined to be a good element, and if ΔVg is greater than 10mV, it can be determined to be a defective element. More preferably, as a threshold for determining quality, ΔVg = 2mV when Id = 1μA can be set.

[0033] The sensor system of this embodiment may further include a storage device 200 (shown in Figure 1) that stores the evaluation results of the quality of the sensor element 50 by the processing device 100. The threshold value for quality determination can also be stored in the storage device 200.

[0034] Figure 3(b) is a schematic diagram showing the state of probe molecule 32 at point b (Vg<0) of the first Id-Vg characteristic I shown in Figure 3(a). Figure 3(c) is a schematic diagram showing the state of probe molecule 32 at point c (near Vg=CNP) of the first Id-Vg characteristic I shown in Figure 3(a). Figure 3(d) is a schematic diagram showing the state of probe molecule 32 at point d (Vg<0) of the second Id-Vg characteristic II shown in Figure 3(a).

[0035] As shown in Figures 3(a) to 3(d), in a good device, even if Vg fluctuates, the probe molecule 32 remains in close proximity to the surface of the sensing part (graphene) 20, and it is thought that the sensing part 20 is more sensitive to the target molecule captured by the probe molecule 32.

[0036] Figure 4(b) is a schematic diagram showing the state of probe molecule 32 at point b (Vg<0) of the first Id-Vg characteristic I shown in Figure 4(a). Figure 4(c) is a schematic diagram showing the state of probe molecule 32 at point c (near Vg=CNP) of the first Id-Vg characteristic I shown in Figure 4(a). Figure 4(d) is a schematic diagram showing the state of probe molecule 32 at point d (Vg<0) of the second Id-Vg characteristic II shown in Figure 4(a).

[0037] As shown in Figures 4(a) to 4(d), in the defective element, the restraining force of the probe molecule 32 on the surface of the sensing part (graphene) 20 is weak, and it is thought that, with fluctuations in Vg, the charged (e.g., negatively charged) probe molecule 32 moves closer to or away from the surface of the sensing part 20 in the liquid 31 due to electrostatic attraction. If the target molecule trap site of the probe molecule 32 is far from the surface of the sensing part 20, it is thought that even if the target molecule is captured at the trap site, the sensing part 20 will not be able to sense the charge of the target molecule easily.

[0038] As shown in Figure 1, the sensor system of the embodiment may further include a target molecule incorporation unit 62 that exposes a sample atmosphere containing hydrophobic target molecules to a hydrophilic organic solvent, a mixing unit 91 that mixes the organic solvent containing target molecules with an aqueous solution to create a sample solution, and a second liquid supply mechanism that supplies the sample solution to the surface of the sensing unit 20. The second liquid supply mechanism may, for example, include a pipe 95 connecting the mixing unit 91 and the sensor unit 30, and a valve 94 connected to the pipe 95.

[0039] The target molecule intake unit 62 is connected to piping 61 and piping 64. A suction / exhaust device 63 is connected to piping 64. The suction / exhaust device 63 is, for example, a pump or a fan. By driving the suction / exhaust device 63, the sample atmosphere is taken into the target molecule intake unit 62 via piping 61. In this embodiment, the object to be detected by the sensor element is a hydrophobic target molecule contained in the sample atmosphere.

[0040] The target molecule incorporation unit 62 is connected to a source of organic solvent. For example, the target molecule incorporation unit 62 is connected to an organic solvent tank 65 containing the organic solvent via piping 69, a valve 68, and piping 66. The organic solvent is a hydrophilic organic solvent, selected from the group consisting of, for example, lower alcohols such as ethanol and methanol, DMSO (Dimethyl Sulfoxide), DMF (N,N-dimethylformamide), acetone, and acetonitrile.

[0041] An organic solvent is supplied from the organic solvent tank 65 to the target molecule incorporation unit 62. The target molecule incorporation unit 62 exposes the sample atmosphere, which may contain hydrophobic target molecules, to the hydrophilic organic solvent.

[0042] The target molecule intake unit 62 is connected to a drainage pipe 77, to which a valve 76 is connected. The target molecule intake unit 62 is also connected to a metering unit 78 via pipes 73, valve 72, and pipe 74.

[0043] The organic solvent tank 65 is connected to the metering unit 78 via piping 66, valve 68, piping 71, valve 72, and piping 74.

[0044] The measuring unit 78 is connected to a drain pipe 79, to which a valve 81 is connected. The measuring unit 78 is also connected to a mixing unit 91 via a pipe 83, to which a valve 82 is connected.

[0045] A source of aqueous solution is connected to the mixing unit 91. For example, the mixing unit 91 is connected to an aqueous solution tank 84 containing the aqueous solution via a metering unit 87. A valve 86 is connected to a pipe 85 connecting the aqueous solution tank 84 and the metering unit 87. A valve 88 is connected to a pipe 89 connecting the mixing unit 91 and the metering unit 87. The aqueous solution is, for example, a phosphate buffer, a HEPES buffer, or a Tris-HCl buffer.

[0046] The mixing unit 91 is supplied with an organic solvent that may contain the target molecule from the target molecule incorporation unit 62, and further supplied with an aqueous solution from the aqueous solution tank 84. The mixing unit 91 then mixes the organic solvent that may contain the target molecule with the aqueous solution to create a sample solution.

[0047] The mixing unit 91 is connected to the sensor unit 30 via piping 95. A valve 94 is connected to piping 95. The mixing unit 91 is also connected to piping 93 for draining liquid, and a valve 92 is connected to piping 93.

[0048] The surface of the sensing element 20 in the sensor unit 30 is exposed to the flow path through which the sample liquid is supplied. The surface of the sensing element 20 and the probe molecules 32 are exposed to the sample liquid. The sensor unit 30 is connected to a drain pipe 97, and a valve 96 is connected to the pipe 97.

[0049] For example, the target molecule incorporation unit 62 has a tank that bubbles the sample atmosphere into an organic solvent. This tank is connected to the organic solvent tank 65 via piping 69, a valve 68, and piping 66. A pump 67 is connected to piping 66. By opening valve 68 to piping 69 and driving the pump 67, the organic solvent stored in the organic solvent tank 65 is supplied into the tank of the target molecule incorporation unit 62.

[0050] An atmosphere collection port is formed at one end of piping 61. The other end of piping 61 is located in the organic solvent in the tank of the target molecule intake unit 62. One end of piping 64 is located in the gas phase above the organic solvent in the tank of the target molecule intake unit 62, and the other end of piping 64 is an exhaust port. An intake and exhaust device 63 is connected between the tank of the target molecule intake unit 62 and the exhaust port of piping 64. By operating the intake and exhaust device 63, the sample atmosphere taken into piping 61 from the atmosphere collection port is bubbling into the organic solvent in the tank of the target molecule intake unit 62, and the target molecules in the sample atmosphere dissolve in the organic solvent.

[0051] The tank of the target molecule intake unit 62 is connected to the metering unit 78 via piping 73, valve 72, and piping 74. By opening valve 72 to piping 73 and driving the pump 75 connected to piping 74, an organic solvent containing the target molecule from the tank of the target molecule intake unit 62 is supplied to the metering unit 78.

[0052] A method for detecting a target molecule using the sensor system of the embodiment may include the steps described below.

[0053] (Step 1) The intake and exhaust device 63 is activated, and the sample atmosphere is introduced into the target molecule intake unit 62 through the piping 61. The valve 68 is then switched to a state that connects piping 66 and piping 69, and the pump 67 is activated to supply organic solvent from the organic solvent tank 65 to the target molecule intake unit 62. In this target molecule intake unit 62, the target molecules in the sample atmosphere dissolve in the organic solvent.

[0054] Hydrophobic target molecules are poorly soluble in aqueous solutions but dissolve in organic solvents and disperse within them. Therefore, hydrophobic target molecules can be efficiently incorporated into liquids from the air.

[0055] (Step 2) The valve 72 is switched to a state that connects pipe 73 and pipe 74, and the pump 75 is driven to supply the organic solvent containing the target molecules from the target molecule intake unit 62 to the metering unit 78. In addition, the valve 86 is opened to supply the aqueous solution from the aqueous solution tank 84 to the metering unit 87.

[0056] The aqueous solution may contain, for example, a labeled molecule that has an affinity for the target molecule. The labeled molecule is hydrophilic and dissolved in the aqueous solution. Examples of aqueous solutions include phosphate buffer, HEPES buffer, and Tris-HCl buffer. The number of labeled molecules is greater than the number of target molecules. The labeled molecule is either a molecule with a larger molecular weight than the target molecule, a charged molecule, or a polar molecule with polarization. Examples of labeled molecules include arginine, arginine methyl ester, arginine amide, nucleic acid aptamer, or peptide.

[0057] (Step 3) Valve 82 is opened to supply a first predetermined amount of organic solvent (which may contain the target molecule) measured in the metering unit 78 to the mixing unit 91. Valve 88 is also opened to supply a second predetermined amount of aqueous solution measured in the metering unit 87 to the mixing unit 91. As a result, in the mixing unit 91, a sample solution is prepared in which the first predetermined amount of organic solvent (which may contain the target molecule) is mixed with the second predetermined amount of aqueous solution.

[0058] Hydrophilic organic solvents diffuse in aqueous solutions, and the organic solvent and the aqueous solution become miscible. When the organic solvent contains target molecules, the target molecules rapidly disperse into the aqueous solution, yielding the sample solution. Because the target molecules are hydrophobic, they remain in an unstable state in the sample solution. Although the target molecules are hydrophobic, they are dispersed in the hydrophilic organic solvent when mixed with an aqueous solution. Since this hydrophilic organic solvent mixes with the aqueous solution, the target molecules can be efficiently dispersed into the aqueous solution with less energy than directly incorporating the hydrophobic target molecules into the aqueous solution without the intermediary organic solvent.

[0059] Furthermore, as mentioned above, labeled molecules are dispersed in aqueous solutions. Therefore, labeled molecules are also dispersed in the sample solution. The sample solution is an aqueous solution obtained by diluting an organic solvent with an aqueous solution, and the hydrophobic target molecules in the sample solution are in an unstable state. These unstable target molecules associate with nearby labeled molecules. For example, limonene as a target molecule and arginine amide as a labeled molecule combine through π-π interactions to form an aggregate.

[0060] (Step 4) The sample solution is supplied from the mixing unit 91 to the sensor unit 30 via the piping 95 by opening the valve 94. The sensor unit 30 then measures the electrical properties (for example, the Id-Vg properties described above) corresponding to the target molecule in the sample solution.

[0061] When a target molecule is captured by the probe molecule 32 and approaches the surface of the sensing element 20, the electronic state of the surface of the sensing element 20 changes, causing a fluctuation in Id. This fluctuation in Id makes it possible to detect the presence and concentration of the target molecule in the sample solution.

[0062] Furthermore, if the target molecule is uncharged and has a small molecular weight (for example, a molecular weight of 300 or less), it may be difficult to detect the change in the electronic state of the surface of the sensing part 20 due to the proximity of the target molecule. According to this embodiment, as described above, the target molecule associates with the label molecule, so when the target molecule is captured by the probe molecule 32, the label molecule also comes into close proximity to the surface of the sensing part 20. Here, if the label molecule has a strong charge, such as arginine amide, or has a large molecular weight (for example, 500 or more), such as nucleic acid or peptide, it is possible to detect the change in the electronic state of the sensing part 20 due to the proximity of this label molecule (for example, the proximity of the charge of the label molecule or the change in the distribution of ions at the solution interface due to the proximity of a large label molecule). As a result, even if detection is difficult with only the proximity of the target molecule, it becomes possible to detect the presence and concentration of the target molecule in the sample solution by detecting the proximity of the label molecule.

[0063] (Step 5) Valve 76 is opened to discharge the remaining organic solvent that the sample atmosphere in the target molecule intake unit 62 was exposed to from the target molecule intake unit 62 through pipe 77. Also, valve 92 is opened to discharge the remaining sample solution in the mixing unit 91 through pipe 93.

[0064] (Step 6) Valves 68 and 72 are opened to the sides of pipes 69 and 73, respectively, and valve 81 is also opened to drain the organic solvent from the organic solvent tank 65 into pipe 79 via the target molecule intake unit 62 and the metering unit 78. The target molecule intake unit 62 and the metering unit 78 are washed with the organic solvent in the organic solvent tank 65, which is not exposed to the sample atmosphere. Target molecules are discharged from the target molecule intake unit 62 and the metering unit 78.

[0065] (Step 7) Valves 68 and 72 are opened to the side of piping 71 to supply the organic solvent from the organic solvent tank 65 to the metering unit 78 through piping 71. The organic solvent is supplied from the organic solvent tank 65 to the metering unit 78 without passing through the target molecule intake unit 62. In addition, valve 86 is opened to supply the aqueous solution from the aqueous solution tank 84 to the metering unit 87 through piping 85.

[0066] (Step 8) Valve 82 is opened to supply the same first predetermined amount of organic solvent (which does not contain the target molecule) measured in the metering unit 78 to the mixing unit 91. Valve 88 is also opened to supply the same second predetermined amount of aqueous solution (which does not contain the target molecule) measured in the metering unit 87 to the mixing unit 91. As a result, a control solution is created in the mixing unit 91 in which the first predetermined amount of organic solvent (which does not contain the target molecule) is mixed with the second predetermined amount of aqueous solution. The solution supplied from the mixing unit 91 to the sensor unit 30 through the piping 95 becomes liquid 31. The aqueous solution of organic solvent that has incorporated the target molecule is called the sample solution.

[0067] (Step 9) The control solution is supplied from the mixing unit 91 to the sensor unit 30 via piping 95 by opening valve 94. By comparing the measurement signal (electrical characteristics) of the sensor element 50 exposed to the control solution that does not contain the target molecule with the measurement signal (electrical characteristics) of the sensor element 50 exposed to the sample solution, if the target molecule is present in the sample solution, high-precision detection of the target molecule with corrected disturbance noise can be performed.

[0068] According to this embodiment, hydrophobic target molecules are concentrated and incorporated into the organic solvent, and the aqueous solution of the organic solvent (sample solution) containing the incorporated target molecules is exposed to the surface of the sensing unit 20. Therefore, the detection sensitivity of the target molecules can be increased compared to when the hydrophobic target molecules are directly incorporated into the aqueous solution.

[0069] Biomolecules (e.g., peptides, DNA aptamers, etc.) function in aqueous solutions. Therefore, when a biomolecule is used as a probe molecule 32, exposure of the surface of the sensing part 20 to an organic solvent alters or destroys the structure of the biomolecule probe molecule 32, reducing its ability to capture target molecules.

[0070] Furthermore, because graphene is hydrophobic, it has a high affinity for organic solvents, and exposure of the graphene surface as the sensitive part 20 to organic solvents may cause damage. This damage raises concerns that organic solvents may penetrate the adhesion surface between the graphene and the substrate film, and the interface between the first and second electrodes 41 and 42 and the protective insulating film covering them, potentially inducing delamination of the graphene and the protective insulating film.

[0071] In this embodiment, the sample solution, which is an aqueous solution obtained by diluting an organic solvent with an aqueous solution, is exposed to the surface of the sensing part 20, so the above problem does not occur.

[0072] The control solution can be used as the liquid 31 supplied to the surface of the sensing part 20 when evaluating the quality of the sensor element 50. Alternatively, only the aqueous solution in the aqueous solution tank 84 may be used as the liquid 31 supplied to the surface of the sensing part 20. The first liquid supply mechanism that supplies the liquid 31 to the surface of the sensing part 20 may include at least the aqueous solution tank 84 and piping 85, 89, and 95 connecting the aqueous solution tank 84 and the sensor unit 30.

[0073] In the sensor element evaluation method of the embodiment, a solution containing probe molecules 32 in a solvent can be supplied to the surface of the sensing part 20, the solvent can be evaporated, and then liquid 31 can be supplied to the surface of the sensing part 20. For example, after supplying the solution containing probe molecules 32 to the surface of the sensing part 20, the solvent is evaporated by drying the surface of the sensing part 20 at room temperature for a predetermined time or longer. As a result, as shown in Figures 3(b) to (d) above, the probe molecules 32 are more likely to be confined in close proximity to the surface of the sensing part 20, making it easier to produce a good sensor element. For example, a buffer solution can be used as the solvent.

[0074] Furthermore, in the sensor element evaluation method of the embodiment, if the sensor element 50 is evaluated as good, target molecules can be supplied to the surface of the sensing part 20 and its electrical characteristics can be measured. If it can be confirmed that the sensing part 20 is sensitive to the target molecules during this measurement of electrical characteristics, the sensor element can be confirmed as a good element.

[0075] The embodiments may include the following sensor systems and methods for evaluating sensor elements.

[0076] [Configuration 1] A sensor element having a sensing portion, a probe molecule located on the surface of the sensing portion, and a first electrode and a second electrode electrically connected to the sensing portion, A processing device that applies a voltage between the first electrode and the second electrode and evaluates the quality of the sensor element based on its electrical characteristics, A sensor system equipped with the following features. [Configuration 2] The sensing element is a sensor system according to configuration 1, including graphene. [Configuration 3] A first liquid supply mechanism that supplies liquid to the surface of the sensing part, A gate electrode that applies a voltage to the liquid supplied to the surface of the sensing part, Furthermore, The sensor system according to configuration 1 or 2, wherein when the current flowing between the first electrode and the second electrode through the sensing portion is Id and the voltage of the gate electrode is Vg, the electrical characteristics are Id-Vg characteristics. [Structure 4] The sensor system according to configuration 3, wherein the processing device evaluates the quality of the sensor element by comparing a first Id-Vg characteristic obtained when Vg is swept from a negative voltage to a positive voltage with a second Id-Vg characteristic obtained when Vg is swept from a positive voltage to a negative voltage. [Composition 5] The sensor system according to configuration 4, wherein the processing device evaluates the quality of the sensor element based on the difference in Id when Vg is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic. [Composition 6] The sensor system according to configuration 5, wherein the processing device evaluates the quality of the sensor element based on the difference in Id when Vg is 0 or negative. [Composition 7] The sensor system according to configuration 4, wherein the processing device evaluates the quality of the sensor element based on the difference in Vg when Id is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic. [Structure 8] A target molecule incorporation unit that exposes a sample atmosphere containing hydrophobic target molecules to a hydrophilic organic solvent, A mixing unit that mixes the organic solvent containing the target molecule with an aqueous solution to prepare a sample solution, A second liquid supply mechanism that supplies the sample liquid to the surface of the sensing part, A sensor system described in any one of configurations 1 to 7, further comprising the above. [Composition 9] The sensor system according to any one of configurations 1 to 8, further comprising a storage device for storing the evaluation results of the quality of the sensor element by the processing device. [Configuration 10] The sensor system according to any one of configurations 1 to 9, wherein the probe molecule comprises at least one of a protein, peptide, antibody, DNA aptamer, or a biomolecule derived thereof. [Composition 11] A method for evaluating a sensor element, wherein a probe molecule is positioned on the surface of the sensing part, and a voltage is applied between a first electrode and a second electrode electrically connected to the sensing part, and the quality of the sensor element is evaluated based on the electrical characteristics of the sensor element. [Composition 12] A liquid is supplied to the surface of the sensing part. A voltage is applied from the gate electrode to the liquid supplied to the surface of the sensing part. A method for evaluating a sensor element according to configuration 11, wherein the Id-Vg characteristic is measured as the electrical characteristic when the current flowing between the first electrode and the second electrode through the sensing part is Id and the voltage of the gate electrode is Vg. [Composition 13] A method for evaluating a sensor element according to configuration 12, which evaluates the quality of the sensor element by comparing a first Id-Vg characteristic obtained when Vg is swept from a negative voltage to a positive voltage with a second Id-Vg characteristic obtained when Vg is swept from a positive voltage to a negative voltage. [Composition 14] A method for evaluating a sensor element according to configuration 13, wherein the quality of the sensor element is evaluated based on the difference in Id when Vg is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic. [Composition 15] The processing apparatus evaluates the quality of the sensor element according to configuration 14, based on the difference in Id when Vg is 0 or negative. [Composition 16] A method for evaluating a sensor element according to configuration 13, wherein the quality of the sensor element is evaluated based on the difference in Vg when Id is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic. [Composition 17] A solution containing the probe molecule in a solvent is supplied to the surface of the sensing part. A method for evaluating a sensor element according to any one of configurations 12 to 16, wherein the solvent is evaporated and the liquid is supplied to the surface of the sensing part. [Composition 18] A method for evaluating a sensor element according to any one of configurations 11 to 17, wherein if the sensor element is evaluated as good, a target molecule is supplied to the surface of the sensing part and the electrical characteristics are measured.

[0077] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0078] 10...Substrate, 20...Sensing part, 30...Sensor unit, 31...Liquid, 32...Probe molecule, 41...First electrode, 42...Second electrode, 43...Gate electrode, 50...Sensor element, 100...Processing device, 200...Memory device

Claims

1. A sensor element having a sensing portion, a probe molecule located on the surface of the sensing portion, and a first electrode and a second electrode electrically connected to the sensing portion, A processing device that applies a voltage between the first electrode and the second electrode and evaluates the quality of the sensor element based on its electrical characteristics, A first liquid supply mechanism that supplies liquid to the surface of the sensing part, A gate electrode that applies a voltage to the liquid supplied to the surface of the sensing part, Equipped with, When the current flowing between the first electrode and the second electrode through the sensing portion is Id and the voltage of the gate electrode is Vg, the electrical characteristics are Id-Vg characteristics. The processing device is a sensor system that evaluates the quality of the sensor element by comparing a first Id-Vg characteristic obtained when Vg is swept from a negative voltage to a positive voltage with a second Id-Vg characteristic obtained when Vg is swept from a positive voltage to a negative voltage.

2. The sensor system according to claim 1, wherein the sensing element includes graphene.

3. The sensor system according to claim 1 or 2, wherein the processing device evaluates the quality of the sensor element based on the difference in Id when Vg is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic.

4. The sensor system according to claim 3, wherein the processing device evaluates the quality of the sensor element from the difference in Id when Vg is 0 or negative.

5. The sensor system according to claim 1 or 2, wherein the processing device evaluates the quality of the sensor element from the difference in Vg when Id is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic.

6. A target molecule incorporation unit that exposes a sample atmosphere containing hydrophobic target molecules to a hydrophilic organic solvent, A mixing unit that mixes the organic solvent containing the target molecule with an aqueous solution to prepare a sample solution, A second liquid supply mechanism that supplies the sample solution to the surface of the sensing part, The sensor system according to claim 1 or 2, further comprising:

7. The sensor system according to claim 1 or 2, further comprising a storage device for storing the evaluation results of the quality of the sensor element by the processing device.

8. The sensor system according to claim 1 or 2, wherein the probe molecule comprises at least one of a protein, peptide, antibody, DNA aptamer, or a biomolecule derived thereof.

9. A method for evaluating a sensor element, wherein a probe molecule is positioned on the surface of the sensing part, and a voltage is applied between a first electrode and a second electrode electrically connected to the sensing part, and the quality of the sensor element is evaluated based on the electrical characteristics of the sensor element, A liquid is supplied to the surface of the sensing part. A voltage is applied from the gate electrode to the liquid supplied to the surface of the sensing part. When the current flowing between the first electrode and the second electrode through the sensing part is Id and the voltage of the gate electrode is Vg, the Id-Vg characteristic is measured as the electrical characteristic. A method for evaluating a sensor element, which involves comparing a first Id-Vg characteristic obtained when Vg is swept from a negative voltage to a positive voltage with a second Id-Vg characteristic obtained when Vg is swept from a positive voltage to a negative voltage, to evaluate the quality of the sensor element.

10. The method for evaluating a sensor element according to claim 9, wherein the quality of the sensor element is evaluated based on the difference in Id when Vg is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic.

11. The method for evaluating a sensor element according to claim 10, wherein the quality of the sensor element is evaluated from the difference in Id when Vg is 0 or negative.

12. The method for evaluating a sensor element according to claim 9, wherein the quality of the sensor element is evaluated based on the difference in Vg when Id is the same value in the first Id-Vg characteristic and the second Id-Vg characteristic.

13. A solution containing the probe molecule in a solvent is supplied to the surface of the sensing part. A method for evaluating a sensor element according to any one of claims 9 to 12, wherein the liquid is supplied to the surface of the sensing part after the solvent has evaporated.

14. If the sensor element is evaluated as good, a method for evaluating a sensor element according to any one of claims 9 to 12, wherein a target molecule is supplied to the surface of the sensing part and the electrical characteristics are measured.

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