Method for manufacturing odor sensor, and odor sensor

Abstract

The purpose of the present invention is to provide a method for manufacturing an odor sensor capable of enhancing the degree of freedom of combination of a main agent and an additive used in an odor adsorption part without lowering the detection accuracy of the odor sensor, and to provide the odor sensor. An odor adsorption part 313 has a base agent 315 that has a porous structure 316 that is continuous in a thickness direction Dr of the odor adsorption part 313 and an additive 317 added to the base agent 315, and causes a change in electrical characteristics between when an odor substance is not adsorbed onto the additive 317 and when the odor substance is adsorbed onto the additive 317. A detection part 314 is an element that outputs the electrical characteristic change as a signal. A film formation step for forming the base agent 315 as a film on the detection part 314, and an addition step for adding the additive 317 to the base agent 315 applied on the detection part 314 are provided. After the addition step, the additive 317 infiltrates the porous structure 316 of the base agent 315.

Description

Method for manufacturing odor sensor and odor sensor

[0001] The present invention relates to a method for manufacturing an odor sensor and an odor sensor.

[0002] Conventionally, in order to measure the intensity of an odor or identify the type of an odor, detection of an odor substance contained in a gas has been performed using an odor sensor. The odor sensor has, for example, an adsorption film that adsorbs an odor substance and a detection unit that detects a change in the surface state (surface characteristics) resulting from the adsorption of the odor substance onto the adsorption film (see, for example, Patent Document 1). Conductive materials such as conductive polymers like polyaniline and ionic liquid materials, which have high electron or ion conductivity (excellent conductivity) (hereinafter referred to as conductive materials), are used for the adsorption film of the odor sensor. Further, for the detection unit, a field effect transistor sensor capable of detecting an electrical property change of the adsorption film, a charge transfer type sensor array (hereinafter referred to as a CMOS sensor) as described in Non-Patent Document 1, or the like is used. The adsorption film is formed (film-formed) by adding an additive having a function of adsorbing an odor to a main agent such as a conductive polymer.

[0003] International Publication No. 2017 / 085939

[0004] Naoya Shinmei, Tatsuya Iwata, Kenichi Hashizume, Shunichiro Kuroki, Kazuaki Sawada (2017), Gas distribution imaging using a charge transfer type sensor array with a polyaniline sensitive film, The 64th Spring Meeting of the Applied Physics Society of Japan, 16p-416-6

[0005] However, some of the additives used for the adsorption film may have poor compatibility with the main agent, making film formation difficult. Therefore, it is necessary to consider the combination of the main agent and the additive, and the degree of freedom in selecting materials may be limited. Also, depending on the type of the additive, the adsorption film formed on the detection unit may not be uniformly film-formed, which may reduce the detection accuracy of the odor sensor. Furthermore, there is also a method of impregnating the additive into the main agent by applying the additive onto the main agent. In this case, however, depending on the type of the additive, the additive may not penetrate into the inside of the main agent and may only be on the surface of the main agent. In this case as well, there is a risk of reducing the detection accuracy of the odor sensor.

[0006] The present invention has been made in view of the above circumstances, and its exemplary objective is to provide a method for manufacturing an odor sensor and an odor sensor that can increase the degree of freedom in the combination of main agent and additive used in the odor adsorption part without reducing the detection accuracy of the odor sensor.

[0007] To solve the above problems, the method for manufacturing an odor sensor, as an exemplary aspect of the present invention, has the following configuration.

[0008] A method for manufacturing an odor sensor having an odor adsorption part and a base, wherein the odor adsorption part comprises a main component having a nanoporous structure continuous in the thickness direction of the odor adsorption part, and an additive added to the main component, and produces an electrical characteristic change when an odor substance is not adsorbed on the additive and when it is adsorbed, the base is an element that outputs the electrical characteristic change as a signal, and the method comprises a film formation step of forming the main component on the base, and an addition step of adding the additive to the main component coated on the base, wherein after the addition step, the additive penetrates the nanoporous structure of the main component.

[0009] To solve the above problems, the odor sensor as an exemplary aspect of the present invention has the following configuration.

[0010] An odor sensor having an odor adsorption portion and a base portion, wherein the odor adsorption portion comprises a main component having a nanoporous structure continuous in the thickness direction of the odor adsorption portion and an additive added to the main component, and produces an electrical characteristic change when an odor substance is adsorbed on the additive and when it is not; the base portion is an element that outputs the electrical characteristic change as a signal; and the additive penetrates the nanoporous structure of the main component.

[0011] Further objects or other features of the present invention will be revealed by preferred embodiments described below with reference to the accompanying drawings.

[0012] According to the present invention, it is possible to provide a method for manufacturing an odor sensor and an odor sensor that can increase the degree of freedom in the combination of main agent and additives used in the odor adsorption part without reducing the detection accuracy of the odor sensor.

[0013] A schematic diagram showing the general configuration of the odor sensor of the embodiment, (a) a top view of the odor sensor, (b) a cross-sectional view taken along the line A-A in (a). A schematic diagram showing the general configuration of the odor sensor of the embodiment, (a) a top view of the odor sensor, (b) a cross-sectional view taken along the line B-B in (a). A schematic diagram showing the general configuration of the odor data analysis device of the embodiment. A schematic diagram showing the odor sensor of Embodiment 1, (a) a schematic cross-sectional view of the odor sensor, (b) a schematic top view of the odor sensor. A diagram illustrating the manufacturing method of the odor sensor of Embodiment 1, (a) a schematic diagram showing the detection unit, (b) a schematic diagram showing the film formation process, (c) a schematic diagram showing the additive process. A schematic diagram illustrating the porous structure manufacturing method 1 of Embodiment 1, (a) a schematic diagram showing the mixing process, (b) a schematic diagram showing the first dissolution process, (c) a schematic diagram showing the coating process, (d) a schematic diagram showing the second dissolution process. Schematic diagrams, (e) Schematic diagram showing the drying process Schematic diagrams showing the results of producing odor adsorption parts by changing the amount of resin to the base agent of Embodiment 1, (a) Schematic diagram showing the odor adsorption part when the amount of resin is small, (b) Schematic diagram showing the odor adsorption part when the amount of resin is appropriate, (c) Schematic diagram showing the odor adsorption part when the amount of resin is large Diagrams explaining the porous structure production method 2 of Embodiment 1, (a) Schematic diagram showing the dissolution process, (b) Schematic diagram showing the coating process, (c) Schematic diagram showing the precipitation process, (d) Schematic diagram showing the drying process Diagrams explaining the effects of Embodiment 1, (a) Schematic diagram of the odor adsorption part of Example 2, (b) Schematic diagram of the odor adsorption part of Comparative Example 1, (c) Schematic diagram of the odor adsorption part of Example 3, (d) Schematic diagram of the odor adsorption part of Comparative Example 2 Diagram showing the schematic configuration of the odor sensor unit of Embodiment 2

[0014] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, "odor substance" broadly refers to a substance that can be adsorbed onto the adsorption membrane (odor adsorption part). Therefore, "odor substance" includes substances that are not generally considered to be odor-causing substances, substances that are not recognized as odor substances, or unknown odor substances. Furthermore, "odor substance" includes not only individual odor substances but also "aggregates of multiple odor substances." In the embodiments described below, the CMOS sensor refers to the sensor described in the non-patent literature mentioned above, but is not limited to a CMOS sensor.

[0015] <Odor Sensor> Figure 1 shows an odor sensor 100, where (a) is a top view of the odor sensor 100 and (b) is a cross-sectional view taken along the line A-A in (a). The odor sensor 100 has a plurality of sensor elements 110 and a substrate 120. The sensor element 110 has an adsorption film 112, a detection unit 114, and an electrode 116.

[0016] The odor sensor 100 in Figure 1 has, for example, nine sensor elements 110a to 110i. Specifically, sensor element 110a has an adsorption membrane 112a, a detection unit 114a, and an electrode 116a; sensor element 110b has an adsorption membrane 112b, a detection unit 114b, and an electrode 116b; ..., sensor element 110i has an adsorption membrane 112i, a detection unit 114i, and an electrode 116i. Note that when the sensor elements (adsorption membrane, detection unit, electrode) are not specified, the subscripts a to i (including j to l which will be described later) are omitted. The adsorption membrane 112 is a membrane that adsorbs odor substances, and its details will be described later.

[0017] The detection unit 114 detects changes in the adsorption state (also called adsorption characteristics) caused by the adsorption of odor substances onto the adsorption film 112. Note that "adsorption of odor substances onto the adsorption film 112" includes not only the adsorption of odor substances onto the surface of the adsorption film 112, but also the absorption of odor substances into the interior of the adsorption film 112. Here, the change in the adsorption state caused by the adsorption of odor substances onto the adsorption film 112 includes changes in mechanical, optical, or electrical properties due to the odor substances. The detection unit 114 outputs the change in the adsorption state of the adsorption film 112 as a signal, for example. In other words, the detection unit 114 also functions as a signal converter (transducer).

[0018] "Changes in mechanical properties" include, for example, changes in the resonant frequency of a quartz crystal microbalance (QCM), changes in the velocity of surface acoustic waves, expansion and contraction of films in piezoelectric elements, or changes in deflection. "Changes in optical properties" include changes in absorption wavelength, absorbance, fluorescence and emission characteristics, and changes in refractive index in surface plasmon resonance (SPR) elements, etc. "Changes in electrical properties" include, for example, changes in electrical conductivity, resistance, dielectric constant, and electrochemical impedance in charge-coupled elements, changes in oxidation-reduction potential in oxide semiconductor sensors, and changes in gate current, gate voltage, impedance, and band gap in field-effect transistor (FET) sensors and CMOS sensors, etc.

[0019] Examples of elements (sensors) that can be used in the detection unit 114 include the following: quartz crystal oscillator sensors (QCMs), surface acoustic wave sensors, field-effect transistor (FET) sensors, MOS field-effect transistor sensors, charge-coupled element sensors, metal oxide semiconductor sensors, organic conductive polymer sensors, electrochemical sensors, etc. The elements used in the detection unit 114 are not limited to these, and various elements can be used as appropriate depending on the purpose of use of the odor sensor 100.

[0020] The "adsorption state of odor substances to the adsorption membrane 112" includes, for example, the "amount of odor substances adsorbed to the adsorption membrane 112." The mechanical, optical, or electrical properties of the adsorption membrane 112 change as the amount of odor substances adsorbed to the adsorption membrane 112 increases or decreases, and the detection unit 114 detects the adsorption state of odor substances to the adsorption membrane 112 by detecting the amount of change.

[0021] The electrode 116 can be formed from a predetermined conductive material. Examples of predetermined conductive materials include inorganic materials and organic materials. Inorganic materials include, for example, gold, silver, platinum, chromium, titanium, aluminum, nickel, nickel alloys, silicon, etc. Organic materials include, for example, polypyrrole, polyaniline, carbon, carbon nanotubes, graphene, and other nanocarbon materials.

[0022] The substrate 120 is, for example, a flat plate having a surface 120a and a surface 120b, with the sensor element 110 mounted on one surface 120a and the electrode 116 mounted on the other surface 120b (see Figure 1(b)). The substrate 120 can be, for example, a silicon substrate, a substrate made of quartz crystal, a printed circuit board, a ceramic substrate, a resin substrate, etc. Alternatively, the substrate 120 may be a multilayer wiring board such as an interposer substrate.

[0023] <Sensor Elements> The odor sensor 100 shown in Figure 1(a) has nine sensor elements 110a to 110i arranged in a 3x3 grid, but the number and arrangement (configuration) of the sensor elements 110 are not limited to this. Also, the sensor element 110 shown in Figure 1 has a one-to-one correspondence between the detection unit 114 and the adsorption film 112, but this is not limited to this. Figure 2 shows another correspondence between the detection unit 114 and the adsorption film 112, where (a) is a top view of the odor sensor 100 and (b) is a cross-sectional view along the line B-B in (a).

[0024] As shown in Figure 2, one adsorption film 112j may correspond to three detection units 114a, 114d, and 114g, forming three sensor elements 110a, 110d, and 110g. Alternatively, one adsorption film 112k may correspond to two detection units 114b and 114c, forming two sensor elements 110b and 110c. Furthermore, one adsorption film 112l may correspond to four detection units 114e, 114f, 114h, and 114i, forming four sensor elements 110e, 110f, 110h, and 110i. In other words, one adsorption film 112 may be provided on n detection units 114 to form n sensor elements 110. Here, n is an integer of 1 or more. Furthermore, one or more sensor elements 110 may be used as reference sensor elements 110 without forming an adsorption film 112 on the detection unit 114.

[0025] <Odor Data Analysis Device> Figure 3 is a schematic diagram showing the general configuration of the odor data analysis device 200 of Embodiment 1. The odor data analysis device 200 has the odor sensor 100 and the analysis unit 220 described above.

[0026] The analysis unit 220 is for analyzing the odor data F1 output from the odor sensor 100. The analysis unit 220 mainly consists of a processing unit (CPU) 220a, and may also have a memory 220b. The memory 220b may be provided externally, separate from the analysis unit 220. The analysis unit 220 also has a data input / output port 220c. The input / output port 220c has the function of receiving the odor data F1 from the odor sensor 100 and the function of transmitting the calculated data R as a result of the calculation processing performed by the CPU 220a to the control unit (not shown). The control unit (not shown) may be the control unit of an external device, such as a personal computer, to which the odor data analysis device 200 is connected by known wired or wireless communication means.

[0027] The memory 220b stores an analysis program P for analyzing odor data F1. This analysis program P performs known calculations on the analysis unit 220, which acts as a computer, specifically the CPU 220a, which is the main component of the analysis unit 220, thereby enabling the analysis of odor data F1. Although the data analysis device 200 in Figure 3 has one odor sensor 100, it may have multiple odor sensors 100.

[0028] [Embodiment 1] The odor adsorption part (adsorption film) is formed (film-formed) by adding an additive, such as a resin (different from the main component) that has the function of adsorbing odors, to a main component such as a resin. The resin used as the main component may or may not have the function of adsorbing odors. Some additives used in the odor adsorption part have poor compatibility with the main component and are difficult to form a film on. Also, depending on the type of additive, such as whether it is acidic or basic, it may or may not be able to form a film on the detection part. Furthermore, there is a method of forming the odor adsorption part by applying the main component to the detection part and then applying the additive on top of the main component, but for example, acidic and basic additives may penetrate into the main component, while neutral additives may not penetrate into the main component. The odor adsorption part (adsorption film) of Embodiment 1 is formed by adding an additive to a main component that has a nanoporous structure continuous in the thickness direction of the odor adsorption part. Therefore, the degree of freedom of combinations of the main component and additive is improved without reducing the detection accuracy of the odor sensor, regardless of their compatibility.

[0029] <Configuration of the Odor Sensor> The odor sensor of Embodiment 1 will be described with reference to Figure 4. Figure 4 is a schematic diagram showing the odor sensor 300 of Embodiment 1, where Figure 4(a) is a schematic cross-sectional view of the odor sensor 300 and Figure 4(b) is a schematic top view of the odor sensor 300.

[0030] The odor sensor 300 of Embodiment 1 has an odor adsorption section 313 (corresponding to the adsorption film 112 described above) and a detection section 314 as a base (corresponding to the detection section 114 described above). The odor adsorption section 313 has a base agent 315 as the main component and an additive 317 (shown by hatching). The base agent 315 has a porous structure (hereinafter referred to as a porous structure) 316. The pore size of each pore in the porous structure 316 is nanoscale. As shown in Figure 4(a), the porous structure 316 has pores continuously formed in the thickness direction Dr of the odor adsorption section 313. Also, as shown in Figure 4(b), pores of various nanoscale pore sizes are formed on the surface of the base agent 315. Note that in Figure 4(b), only some of the porous structures 316 are labeled with reference numerals.

[0031] The pores formed on the surface of the base agent 315 bond with each other to form a porous structure 316 that extends to the detection unit 314. In other words, the base agent 315 is sponge-like. The base agent 315 is, for example, a resin or a conductive polymer, but is not limited to these. Polyvinyl chloride, polymethyl methacrylate, polybutyl methacrylate, polyethylene glycol, polyvinyl alcohol, polyvinylidene fluoride, cycloolefin polymer, polyaniline, polypyrrole, polythiophene, etc., or copolymers of these resins can be used as the base agent 315.

[0032] The additive 317 causes a potential change in the detection unit 314 depending on whether odor substances are adsorbed or not. The additive 317 is not only applied to the surface of the base agent 315, but also penetrates into the porous structure 316 of the base agent 315. In the odor adsorption unit 313 of Embodiment 1, since the additive 317 penetrates into the porous structure 316 formed in the base agent 315, the degree of freedom in combining the base agent 315 and the additive 317 is improved, regardless of their compatibility.

[0033] The additives may include all materials that can penetrate into the porous structure 316. For example, salts containing ionic liquids can be used as additives. The salts are composed of combinations of anions and cations, such as those described below. Anions: Anions include halide ions such as chloride ions, bromide ions, and iodide ions, chloride ions, sulfate ions, nitrate ions, borate ions, tetrachloroferrate(III) ions, tetrafluoroborate ions, hexafluorophosphate ions, hexafluoroantimonate ions, alkylsulfonate ions, alkylphosphate ions, alkylphosphinate ions, alkylphosphonate ions, alkyldithiophosphate ions, thiocyanate ions, alkylsulfate ions, aromatic sulfonate ions such as benzenesulfonic acid, carboxylate ions, bis(perfluoroalkylsulfonyl)imide anions, dicyanamide anions, and tricyanomethanide anions. Cations: Metal ions such as sodium and potassium, ammonium ions, alkylammonium ions, alkylphosphonium ions, alkylimidazolium ions, alkylpyridinium ions, alkylpiperidinium ions, alkylpiperazinium ions, alkylmorpholinium ions, alkylpyrrolidinium ions, and alkylsulfonium ions.

[0034] Furthermore, additives such as acids, including organic acids, can be used. Acids are, for example, proton adducts of the various anions mentioned above. Additives such as bases, including organic bases, can be used. Bases are, for example, hydroxide ion adducts or proton detaches of the various cations mentioned above. Additives such as self-assembling materials can be used. Self-assembling materials include, for example, organosilane compounds, thiols, phosphonic acids, etc., that form self-assembled monolayers. Other self-assembling materials include liquid crystal materials and organic crystals. Additives such as polymer materials can be used. Polymer materials may include, for example, general resins such as polyvinyl alcohol and fluoropolymers, as well as polymer brushes obtained by graft polymerization on the material surface. Additives such as nanoparticles can be used. Inorganic nanoparticles include various metals, semiconductors, oxide nanoparticles, etc., and may also include polymer nanoparticles made by nano-molecularizing the above polymer materials. Furthermore, the additives used are not limited to one type, and multiple types of additives may be used.

[0035] The thickness of the odor adsorption section 313 should be substantially 2 nm or more and 5 μm or less, and preferably 1 μm or less. The odor adsorption section 313 contains an adsorption component that exhibits unique adsorption characteristics for specific odor substances contained in the surrounding gas.

[0036] The detection unit 314 is an element that outputs the generated potential change as a signal. Note that the change caused by the odor adsorption unit 313 is not limited to a change in potential, but may also be a change in resistivity or impedance, and the element of the detection unit 314 may be a sensor that detects current. Examples of elements of the detection unit 314 include a photoelectric conversion element, an FET sensor, or an ISFET sensor.

[0037] The odor sensor 300 may have multiple odor adsorption units 313. Each of the multiple additives 317 in the multiple odor adsorption units 313 may exhibit unique adsorption characteristics for different odor substances, and the multiple odor adsorption units 313 may be independently arranged on the surface of the detection unit 314. Here, "independently arranged" includes the arrangement of the multiple odor adsorption units in any arrangement, such as in a row or grid.

[0038] <Method for Manufacturing an Odor Sensor> A method for manufacturing an odor sensor 300 having an odor adsorption section 313 and a detection section 314 will be described. The method for manufacturing the odor sensor 300 includes a film formation step of forming a base agent 315 on the detection section 314, and an additive step of adding an additive 317 to the base agent 315 applied on the detection section 314. The additive 317 is smaller than or equal to the pore size of the porous structure 316 and penetrates the porous structure 316 of the base agent 315.

[0039] The size of the porous structure 316 is preferably in the range of 0.5 nm to 500 nm. If the size of the porous structure 316 is smaller than 0.5 nm, the additive may not penetrate into the porous structure 316. Also, if the size of the porous structure 316 is larger than 500 nm, it will become as large as the film thickness of the odor adsorption portion 313, which may increase the porosity of the odor adsorption portion 313 and reduce its mechanical strength.

[0040] The additive 317 is preferably in the range of 0.1 nm to 500 nm. Here, most additives 317 are low molecular weight compounds, and the typical molecular size (0.1 nm to several nm) is the lower limit of the size of the additive 317. Also, the pore size of the porous structure 316 is the upper limit of the size of the additive 317. Examples of additives 317 include acids (hydrochloric acid, alkyl sulfonic acid, etc.), salts (carboxylate salts, alkyl sulfonates, ionic liquids, etc.), and self-assembling materials (liquid crystal molecules, etc.).

[0041] Figure 5 is a diagram illustrating the method for manufacturing the odor sensor 300 of Embodiment 1. On the detection unit 314 shown in Figure 5(a), an odor adsorption unit 313 containing a base agent 315 having a porous structure 316 is formed in the film formation step shown in Figure 5(b). In the addition step shown in Figure 5(c), an additive 317 is added. As a result, after the addition step, the additive 317 adheres to the surface of the base agent 315 and penetrates into the porous structure 316 of the base agent 315.

[0042] <Method 1 for producing a base material having a porous structure> A method for producing a base material 315 having a porous structure 316 (hereinafter referred to as porous structure production method 1) will be described. Porous structure production method 1 includes a mixing step and a first dissolution step before the film formation step described above. The film formation step includes a coating step and a second dissolution step. Porous structure production method 1 may also include a drying step after the second dissolution step in which the base material 315 on which the porous structure 316 has been formed is dried.

[0043] Figure 6 is a schematic diagram illustrating the porous structure fabrication method 1. Figure 6(a) is a schematic diagram showing the mixing step, Figure 6(b) is a schematic diagram showing the first dissolution step, Figure 6(c) is a schematic diagram showing the coating step, Figure 6(d) is a schematic diagram showing the second dissolution step, and Figure 6(e) is a schematic diagram showing the drying step. In the mixing step shown in Figure 6(a), the base agent 315 (white triangle) and the resin 318 (black circle) are mixed to produce a mixture 319. Here, when the base agent 315 is a resin, the resin 318 is a different resin (second resin) from the first resin, if the base agent 315 is the first resin. Note that in Figure 6(a), only some parts are labeled with reference numerals. In the first dissolution step shown in Figure 6(b), the mixture 319 is dissolved in a first solvent 320 which is a good solvent for the base agent 315 and the resin 318.

[0044] In the coating process shown in FIG. 6(c), the mixture 319 dissolved in the first solvent 320 is applied onto the detection unit 314. The coating process can be performed, for example, using a spray gun, dispenser, coater, printer, etc., and the same applies to the following other coating processes. In the second dissolution process shown in FIG. 6(d), the resin 318 is dissolved by the second solvent 321 which is a poor solvent for the base agent 315 and a good solvent for the resin 318. In the second dissolution process, the second solvent 321 may be applied to the mixture 319 dissolved in the first solvent 320, or may be sprayed as shown in the figure. Thereby, a porous structure 316 is formed on the base agent 315. In the drying process shown in FIG. 6(e), the first solvent 320 and / or the second solvent 321 are removed by drying to obtain the odor adsorption unit 313 including the base agent 315 having the porous structure 316. In FIG. 6(e), the illustration of the white triangular base agent 315 is omitted.

[0045] Here, the first solvent 320 which is a good solvent for the base agent 315 and the resin 318 means that the first solvent 320 can dissolve both the base agent 315 and the resin 318 (solubility), and the first solvent 320 is also referred to as a co-solvent. Also, the second solvent 321 which is a poor solvent for the base agent 315 means that the second solvent 321 cannot dissolve the base agent 315 (insolubility). On the other hand, the second solvent 321 which is a good solvent for the resin 318 means that the second solvent 321 can dissolve the resin 318. Thus, the base agent 315 is insoluble in the second solvent 321, but the resin 318 is soluble in the second solvent 321. By selectively dissolving the resin 318 in the mixture 319 with the second solvent 321 in this way, nanoscale pores are formed at the locations where the resin 318 was present.

[0046] Here, as an example of the base agent 315, polyaniline, as an example of the resin 318, polyethylene glycol, as an example of the first solvent 320 (co-solvent), N-methylpyrrolidone (NMP), and as an example of the second solvent 321 (poor solvent), water can be respectively cited.

[0047] <Amount of Resin 318>In the mixing process described in FIG. 6(a), the ratio of resin 318 to base agent 315 will be described. FIG. 7 is a schematic diagram showing the results of fabricating odor adsorption parts by changing the amount of resin relative to the base agent. FIG. 7(a) is a schematic diagram showing odor adsorption part 313a (odor sensor 300a) when the amount of resin 318 relative to base agent 315 is small. FIG. 7(b) is a schematic diagram showing odor adsorption part 313 (odor sensor 300) of Embodiment 1 where the amount of resin 318 relative to base agent 315 is appropriate. FIG. 7(c) is a schematic diagram showing odor adsorption part 313b (odor sensor 300b) when the amount of resin 318 relative to base agent 315 is large. In each case, enlarged top surface schematic diagrams of odor adsorption parts 313, 313a, and 313b are shown below the white arrows.

[0048] As shown in FIG. 7(a), when the amount of resin 318 relative to base agent 315 is less than the appropriate amount (predetermined amount), the base agent 315 becomes too dense, so a porous structure 316 continuous in the thickness direction Dr cannot be fabricated, and it was difficult to add additive 317 to base agent 315. As shown in FIG. 7(c), when the amount of resin 318 relative to base agent 315 is more than the appropriate amount, the base agent 315 becomes too sparse, so the base agent 315 does not become uniform, and aggregates 315a of the base agent 315 are formed, resulting in a non-uniform film. On the other hand, as shown in FIG. 7(b), when the amount of resin 318 relative to base agent 315 is appropriate, a porous structure 316 continuous in the thickness direction Dr can be formed, and an odor adsorption part 313 with an appropriate density can be fabricated. The amount of resin 318 added is 1 to 10 times that of base agent 315 by weight ratio.

[0049] <Method 2 for producing a base material having a porous structure> A method for producing a base material 315 having a porous structure 316 (hereinafter referred to as porous structure production method 2) will be described. Porous structure production method 2 has a dissolution step before the film formation step described above. The film formation step has a coating step and a deposition step. Porous structure production method 2 may also have a drying step after the deposition step in which the base material 315 on which the porous structure 316 has been formed is dried. Figure 8 is a diagram illustrating porous structure production method 2. Figure 8(a) is a schematic diagram showing the dissolution step, Figure 8(b) is a schematic diagram showing the coating step, Figure 8(c) is a schematic diagram showing the deposition step, and Figure 8(d) is a schematic diagram showing the drying step.

[0050] In the dissolution step shown in Figure 8(a), the base agent 315 is dissolved in a third solvent 322, which is a good solvent for the base agent 315. The third solvent 322 is a solvent that can dissolve the base agent 315. As the first solvent 320 mentioned above is also a good solvent for the base agent 315, the first solvent 320 can be used as the third solvent 322.

[0051] In the coating step shown in Figure 8(b), the base agent 315 dissolved in the third solvent 322 is applied onto the detection unit 314. In the precipitation step shown in Figure 8(c), the third solvent 322 in which the base agent 315 is dissolved is replaced with a fourth solvent 323, which is a poor solvent for the base agent 315, and the base agent 315 is precipitated. The fourth solvent 323 is a solvent that cannot dissolve the base agent 315. Note that the second solvent 321 mentioned above is also a poor solvent for the base agent 315, so the second solvent 321 can be used as the fourth solvent 323. In the drying step shown in Figure 8(d), the third solvent 322 and / or the fourth solvent 323 are removed by drying to obtain a base agent 315 having a porous structure 316. Note that in Figure 8(d), the white triangle representing the base agent 315 is omitted.

[0052] Here, polyaniline is given as an example of the base agent 315, N-methylpyrrolidone (NMP) as an example of the third solvent 322 (cosolvent), and water as an example of the fourth solvent 323 (poor solvent).

[0053] <Substitution Method> One method for substituting the third solvent 322 with the fourth solvent 323 is as follows: The third solvent 322 in which the base agent 315 is dissolved is applied to the detection unit 314 and left for a predetermined time in a space where the fourth solvent 323 has vaporized. As a result, the third solvent 322 is gradually replaced by the fourth solvent 323, and the base agent 315 slowly precipitates (settles). This makes it possible to obtain a base agent 315 in which a porous structure 316 has been formed. For example, if the base agent 315 is polyaniline, the third solvent 322 is a solvent that is a good solvent for polyaniline, and the fourth solvent 323 is water, then polyaniline having a porous structure 316 can be obtained by leaving the third solvent 322 in which the base agent 315 is dissolved in a high-humidity environment for a predetermined time. For example, the third solvent 322 is left in an environment with a humidity of 60% or higher for one day (a predetermined time). Another example of a third solvent 322 (good solvent) is NMP.

[0054] Alternatively, for example, the third solvent 322 in which the base agent 315 is dissolved is applied to the detection unit 314, and the vapor of the fourth solvent 323 is applied to the third solvent 322 in which the base agent 315 is dissolved for a predetermined time. As a result, the third solvent 322 is replaced by the fourth solvent 323, and a porous structure 316 is formed in the base agent 315. For example, if the base agent 315 is polyaniline, the third solvent 322 is a solvent that is a good solvent for polyaniline, and the fourth solvent 323 is water, then polyaniline having a porous structure 316 can be obtained by applying water vapor to the third solvent 322 in which the base agent 315 is dissolved for a predetermined time. For example, the third solvent 322 is applied to water vapor for 10 minutes to 1 hour (a predetermined time). Here, an example of the third solvent 322 (a good solvent) is NMP.

[0055] The method for forming the porous structure 316 in the base agent 315 is not limited to the porous structure fabrication method 1 and porous structure fabrication method 2 described above, but may be other methods. For example, a method of depositing the base agent 315 as nanoparticles is also applicable.

[0056] <Example 1> The odor adsorption section 313 of Example 1 was prepared by the porous structure preparation method 1. Polyaniline was used as the base agent 315. Polyethylene glycol (PEG) was used as the resin 318. Polyethylene glycol is a water-soluble polymer compound. N-methylpyrrolidone was used as the first solvent 320. Water was used as the second solvent 321. Hydrochloric acid was used as the additive 317. A CMOS sensor was used as the detection unit 314. In Example 1, a porous structure 316 was formed in the base agent 315, and a good odor adsorption section 313 was obtained.

[0057] <Example 2> The odor adsorption section 313 of Example 2 was prepared by the porous structure preparation method 1. Polyvinyl chloride (PVC) was used as the base agent 315. Polyethylene glycol (PEG) was used as the resin 318, as in Example 1. NMP was used as the first solvent 320. Water was used as the second solvent 321. Ionic liquid (imidazolium salt) was used as the additive 317. A CMOS sensor was used as the detection section 314.

[0058] <Comparative Example 1 to Example 2> In Comparative Example 1, a base agent without a porous structure 316 was applied to the detection unit 314. This is the same as Example 1, except that the base agent does not have a porous structure 316.

[0059] <Example 2 and Comparative Example 1> Figure 9 illustrates the effect of Embodiment 1. Figure 9(a) shows a schematic top view of the odor adsorption section 313 of Embodiment 2, and Figure 9(b) shows a schematic top view of the odor adsorption section 313c of Comparative Example 1. In both cases, an enlarged schematic diagram of the upper diagram is shown below the white arrow. In Embodiment 2 of Figure 9(a), a porous structure 316 was formed and confirmed as a microstructure. The microstructure made it difficult to see the detection section 314 below the odor adsorption section 313. Note that the microstructure is shown with hatching in Figure 9. In Embodiment 2, when the additive 317 was added to the base agent 315, the additive 317 could penetrate into the porous structure 316.

[0060] On the other hand, in Comparative Example 1 of Figure 9(b), a uniform film of the base agent was formed, and the microstructure could not be observed. Because the microstructure could not be observed, the detection unit 314 below the odor adsorption unit 313c was visible. In the case of Figure 9(b), the additive 317 only sits on the surface of the base agent and cannot penetrate into the base agent.

[0061] <Example 3> The odor adsorption section 313 of Example 3 was prepared by porous structure preparation method 1. Polymethyl methacrylate (PMMA) (acrylic resin) was used as the base agent 315. Polyethylene glycol (PEG) was used as the resin 318, as in Example 1. NMP was used as the first solvent 320. Water was used as the second solvent 321. Ionic liquid (imidazolium salt) was used as the additive 317. A CMOS sensor was used as the detection section 314.

[0062] <Comparative Example 2 to Example 3> In Comparative Example 2, a base agent without a porous structure 316 was applied to the detection unit 314. Except that the base agent does not have a porous structure 316, it is the same as Example 3.

[0063] <Example 3 and Comparative Example 2> Figure 9(c) shows a schematic top view of the odor adsorption section 313 of Example 3, and Figure 9(d) shows a schematic top view of the odor adsorption section 313d of Comparative Example 2. In both cases, an enlarged schematic diagram of the upper diagram is shown below the white arrow. In Example 3 of Figure 9(c), a porous structure 316 was formed and could be confirmed as a microstructure. Due to the microstructure, the detection section 314 below the odor adsorption section 313 became difficult to see. In Example 3, when the additive 317 was added to the base agent 315, the additive 317 could penetrate into the porous structure 316.

[0064] On the other hand, in Comparative Example 2 of Figure 9(d), a uniform film of the base agent was formed, and the microstructure could not be observed. Because the microstructure could not be observed, the detection unit 314 below the odor adsorption unit 313d was visible. In the case of Figure 9(d), the additive 317 only sits on the surface of the base agent and cannot penetrate into the base agent.

[0065] As described above, Embodiment 1 provides a method for manufacturing an odor sensor and an odor sensor that can increase the degree of freedom in the combination of main agent and additives used in the odor adsorption part without reducing the detection accuracy of the odor sensor.

[0066] [Embodiment 2] The odor sensor according to Embodiment 2 will be described below.

[0067] <Configuration of Odor Sensor> In an odor sensor, an adsorption film is formed on the surface of the base to adsorb specific odor substances. This adsorption film is formed by adding additives to a film material such as a conductive polymer film.

[0068] A quartz crystal oscillator (QCM) sensor can be used as the base. Other sensors that can be used as the base include, for example, surface acoustic wave sensors, field-effect transistors (FETs), charge-coupled element sensors, MOS field-effect transistors, metal oxide semiconductor sensors, organic conductive polymer sensors, electrochemical sensors, piezoelectric element sensors, and SPR sensors. Depending on the base used, the physical quantities that constitute the odor data F1 may include frequency, potential, mass, wavelength and intensity of light and sound, resistance, and current.

[0069] As the membrane material constituting the adsorption film, conductive polymers including conductive resins such as polyaniline, polypyrrole, and polythiophene can be used. Ionic liquids, general-purpose resins, plasticizers, and salts can also be used as membrane materials. Furthermore, inorganic materials such as gold, silver, platinum, chromium, titanium, aluminum, nickel, nickel-based alloys, and silicon can be used for the electrodes. Other materials such as carbon, carbon nanotubes, and graphene (nanocarbon materials) can also be used.

[0070] As additives, for example, inorganic ions, organic acid anions, and polymeric acid anions can be used. Examples of inorganic ions include chloride ions, chloride ions, bromide ions, sulfate ions, nitrate ions, and borate ions. Examples of organic acid anions include alkyl sulfonic acids, benzenesulfonic acids, and carboxylic acids. Examples of polymeric acid anions include organic acid anions such as alkyl sulfonic acids, benzenesulfonic acids, and carboxylic acids, as well as polymeric acid anions such as polyacrylic acid and polystyrene sulfonic acid. Other possible additives include host materials such as cyclodextrins and crown ether derivatives, organic base materials such as alkylamines, arylamines, and nitrogen-containing heterocyclic compounds, and hydrogen-bonding materials such as urea derivatives and thiourea derivatives. Various ionic liquids can also be used as additives.

[0071] <Arrangement of Odor Sensors> Odor sensors can be used by arranging multiple adsorption films on the surface of one or more bases. In this case, for example, multiple different adsorption films, each having unique adsorption characteristics for different odor substances, can be arranged in a line. Alternatively, multiple adsorption films can be arranged vertically and horizontally in groups of multiples to create a planar arrangement.

[0072] By using information about the arrangement of adsorption films with different adsorption characteristics as an encryption key or passcode, security can be enhanced in various situations. This odor sensor, or the entire system including it, can be used as a security system utilizing odor.

[0073] <Anonymization of Odor Database> Figure 10 is a schematic diagram of the odor sensor unit 1010 according to Embodiment 2. The odor sensor unit 1010 has five odor sensors 1010a to 1010e. The odor sensors 1010a to 1010e use, for example, a quartz crystal oscillator sensor (QCM) as the base portion 1002. In this Embodiment 2, the five odor sensors 1010a to 1010e are arranged in a row in order. Adsorption films 1004a to 1004e are formed on the surface of each of the five base portions 1002, and each of the adsorption films 1004a to 1004e corresponds to an odor sensor 1010a to 1010e. The adsorption films 1004a to 1004e are formed by adding additives 1006a to 1006e to a conductive polymer film 1005. Due to the differences in the properties of each additive 1006a to 1006e, the adsorption films 1004a to 1004e exhibit different adsorption properties for adsorbing different odor substances.

[0074] Let's assume that this odor sensor 1010 detects the odors of three types of gases, Ga, Gb, and Gc, and stores them in the database DB1. The detection results when gases Ga, Gb, and Gc are detected by odor sensors 1010a to 1010e are as follows: The numbers in parentheses are the output values ​​of odor sensors 1010a to 1010e, respectively. Gas Ga: (0, 5, 10, 5, 0) Gas Gb: (2, 4, 6, 8, 10) Gas Gc: (10, 8, 6, 4, 2)

[0075] If these output values ​​are stored directly in the odor database DB, and the information in that odor database DB is stolen, the detection results from the odor sensors 1010a to 1010e for gases Ga to Gc will be easily exposed to the thief. However, for example, if the arrangement order of the output values ​​of the five odor sensors 1010a to 1010e is changed, and the output values ​​from the odor sensors 1010a to 1010e are stored in the odor database DB with the changed arrangement order, and if the information of this changed order is managed separately from the odor database DB as an encryption key, then even if the information in the database DB is stolen, the thief will not be able to easily obtain the detection results from the odor sensors 1010a to 1010e for gases Ga to Gc.

[0076] For example, if the order of the output values ​​of the five odor sensors 1010a to 1010e is (1, 3, 5, 2, 4), then the detection results for each gas Ga to Gc stored in the odor database DB will be as follows: Gas Ga: (0, 10, 0, 5, 5) Gas Gb: (2, 6, 10, 4, 8) Gas Gc: (10, 6, 2, 8, 4)

[0077] Without an encryption key, the detection results from the odor sensors 1010a to 1010e for gases Ga to Gc cannot be reproduced in the correct sensor order. However, by using the encryption keys (1, 3, 5, 2, 4), the detection results for gases Ga to Gc in the odor database DB can be decrypted in the correct order from the odor sensors 1010a to 1010e. This measure improves the security of the odor data stored in the odor database DB.

[0078] Furthermore, for example, the order of the sensor array within an odor sensor unit used to detect odor data stored in the odor database DB can be changed from the order of the sensor array within an odor sensor unit sold to the user, and this change can be used as an encryption key. In addition, when producing multiple odor sensor units, changing the sensor array within each unit or each lot and managing this change as an encryption key can further contribute to improving the confidentiality and management of odor data.

[0079] <Entry / Exit Management Using Odor> By using the odor sensor unit 1010 shown in Figure 10, entry / exit management using odor can be realized, for example. Locking and unlocking of entry / exit is performed using a gas with a specific odor. Here, the odor used for entry / exit will be called the "odor key". The odor key may be, for example, a specific perfume or an individual's body odor. By linking the odor sensor unit 1010 with an entry / exit control system that controls the locking and unlocking of room doors, door unlocking can be achieved using the odor key.

[0080] Here, for example, the system can be configured so that the door cannot be unlocked by the scent key alone, and only after entering the sensor array information within the scent sensor unit 1010 as a password can it be unlocked. For example, the detection result for unlocking the door is (2, 4, 6, 8, 10), and this information is stored in a database in the access control system or in the cloud. If the scent key detection result from the scent sensor unit 1010 is (2, 6, 10, 4, 8), the door cannot be unlocked. However, when the sensor array information (1, 3, 5, 2, 4) within the scent sensor unit 1010 is entered, the detection result of (2, 6, 10, 4, 8) is converted to (2, 4, 6, 8, 10). The converted detection result is compared with the detection result stored in the database, and if they match, the door can be unlocked.

[0081] <Industrial Applicability> Furthermore, by using the odor sensor and the method for analyzing the odor data detected by the odor sensor described in the above embodiment, it is possible to quickly and accurately identify odor substances contained in a gas containing multiple different odor substances. It is also possible to reduce the load on the processing unit. When discriminating between the odor of a specific gas and that of another gas, it is possible to discriminate between the two quickly and with high accuracy. In addition, when identifying odor substances contained in the detected gas by comparing the detected odor data with odor data stored in a database, etc., it is possible to compare them quickly and with high accuracy.

[0082] Furthermore, the odor sensors 1010a to 1010e in Embodiment 2 can be replaced with the odor sensor 300 in Embodiment 1. In this case, even in Embodiment 2, it is possible to provide an odor sensor manufacturing method and an odor sensor that can increase the degree of freedom in the combination of main agent and additives used in the odor adsorption part without reducing the detection accuracy of the odor sensor.

[0083] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes are possible within the scope of its gist. For example, the present invention includes the following: (Gist 1) A method for manufacturing an odor sensor having an odor adsorption part and a base, wherein the odor adsorption part has a main component having a nanoporous structure continuous in the thickness direction of the odor adsorption part, and an additive added to the main component, and produces an electrical characteristic change when an odor substance is not adsorbed on the additive and when it is adsorbed, the base is an element that outputs the electrical characteristic change as a signal, the method comprising a film formation step of forming the main component on the base, and an addition step of adding the additive to the main component coated on the base, wherein after the addition step, the additive penetrates the nanoporous structure of the main component. (Purpose 2) The film-forming step may include a mixing step of mixing the main component and the resin to produce a mixture before the film-forming step, and a first dissolution step of dissolving the mixture in a first solvent that is a good solvent for the main component and the resin, and the film-forming step may include a coating step of applying the mixture dissolved in the first solvent onto the base, and a second dissolution step of dissolving the resin with a second solvent that is a poor solvent for the main component and a good solvent for the resin. (Purpose 3) The film-forming step may include a dissolution step of dissolving the main component in a third solvent that is a good solvent for the main component before the film-forming step, and the film-forming step may include a coating step of applying the main component dissolved in the third solvent onto the base, and a precipitation step of replacing the third solvent in which the main component is dissolved with a fourth solvent that is a poor solvent for the main component to precipitate the main component. (Purpose 4) The main component may be a resin. (Purpose 5) The main component may be polyvinyl chloride, polymethyl methacrylate, polyvinylidene fluoride, cycloolefin polymer, polybutyl methacrylate, polyethylene glycol, polyvinyl alcohol, or copolymers of these resins. (Purpose 6) The main component may be a conductive polymer. (Purpose 7) The conductive polymer may be a group of conductive resins including polyaniline, polypyrrole, and polythiophene.(Purpose 8) An odor sensor having an odor adsorption part and a base, wherein the odor adsorption part has a main component having a nanoporous structure continuous in the thickness direction of the odor adsorption part, and an additive added to the main component, and produces an electrical characteristic change when an odor substance is not adsorbed on the additive and when it is adsorbed, the base is an element that outputs the electrical characteristic change as a signal, and the additive penetrates the nanoporous structure of the main component. (Purpose 9) The main component may be a resin. (Purpose 10) The main component may be polyvinyl chloride, polymethyl methacrylate, polyvinylidene fluoride, cycloolefin polymer, polybutyl methacrylate, polyethylene glycol, polyvinyl alcohol, or copolymers of these resins. (Purpose 11) The main component may be a conductive polymer. (Purpose 12) The conductive polymer may be a group of conductive resins including polyaniline, polypyrrole, and polythiophene.

[0084] 100 Odor sensor 110, 110a-110l Sensor element 112, 112a-112l Adsorption film 114, 114a-114l Detection unit 116, 116a-116l Electrode 120 Substrate, 120a, 120b Surface 200 Data analysis device 220 Analysis unit 220a CPU, 220b Memory, 220c Input / output port 300, 300a, 300b Odor sensor 313, 313a-313d Odor adsorption unit 314 Detection unit 315 Base agent, 315a Aggregates 316 Porous structure 317 Additive 318 Resin 319 Mixture 320 First solvent, 321 Second solvent, 322 Third solvent, 323 Fourth solvent 1002 Base 1004a-1004e Adsorption film 1005 Conductive polymer film 1006a-1006e Additive 1010 Odor sensor unit 1010a-1010e Odor sensor DB, DB1 Database Dr Thickness direction F1 Odor data Ga-Gc Gas P Analysis program R Calculated data

Claims

1. A method for manufacturing an odor sensor having an odor adsorption part and a base, wherein the odor adsorption part comprises a main component having a nanoporous structure continuous in the thickness direction of the odor adsorption part, and an additive added to the main component, and produces an electrical characteristic change when an odor substance is not adsorbed on the additive and when it is adsorbed, the base is an element that outputs the electrical characteristic change as a signal, and the method comprises a film formation step of forming the main component on the base, and an addition step of adding the additive to the main component coated on the base, wherein after the addition step, the additive penetrates the nanoporous structure of the main component.

2. A method for manufacturing an odor sensor according to claim 1, comprising: a mixing step of mixing the main component and a resin to produce a mixture before the film-forming step; a first dissolution step of dissolving the mixture in a first solvent that is a good solvent for the main component and the resin; and the film-forming step comprising: a coating step of applying the mixture dissolved in the first solvent onto the base; and a second dissolution step of dissolving the resin with a second solvent that is a poor solvent for the main component and a good solvent for the resin.

3. A method for manufacturing an odor sensor according to claim 1, comprising a dissolution step of dissolving the main component in a third solvent which is a good solvent for the main component before the film formation step, the film formation step comprising a coating step of applying the main component dissolved in the third solvent onto the base, and a precipitation step of replacing the third solvent in which the main component is dissolved with a fourth solvent which is a poor solvent for the main component, thereby precipitating the main component.

4. The method for manufacturing an odor sensor according to claim 1, wherein the main component is a resin.

5. The method for producing an odor sensor according to claim 1, wherein the main component is polyvinyl chloride, polymethyl methacrylate, polyvinylidene fluoride, cycloolefin polymer, polybutyl methacrylate, polyethylene glycol, polyvinyl alcohol, or copolymers of these resins.

6. The method for producing an odor sensor according to claim 1, wherein the main component is a conductive polymer.

7. The method for producing an odor sensor according to claim 6, wherein the conductive polymer is a group of conductive resins including polyaniline, polypyrrole, and polythiophene.

8. An odor sensor having an odor adsorption portion and a base portion, wherein the odor adsorption portion comprises a main component having a nanoporous structure continuous in the thickness direction of the odor adsorption portion, and an additive added to the main component, and produces an electrical characteristic change when an odor substance is adsorbed on the additive and when it is not; the base portion is an element that outputs the electrical characteristic change as a signal; and the additive penetrates the nanoporous structure of the main component.

9. The odor sensor according to claim 8, wherein the main component is a resin.

10. The odor sensor according to claim 8, wherein the main component is polyvinyl chloride, polymethyl methacrylate, polyvinylidene fluoride, cycloolefin polymer, polybutyl methacrylate, polyethylene glycol, polyvinyl alcohol, or copolymers of these resins.

11. The odor sensor according to claim 8, wherein the main component is a conductive polymer.

12. The odor sensor according to claim 11, wherein the conductive polymer is a group of conductive resins including polyaniline, polypyrrole, and polythiophene.

Images