Sensor, measurement system, and measurement method

Abstract

Provided are a sensor, a measurement system, and a measurement method with which it is possible to quickly and accurately, with a simple configuration, identify a minute measurement object. A substrate (3) comprises a dielectric member. An electrode (1) is formed on a surface (3A) of the substrate (3). An electrode (2) is formed on a surface (3B) of the substrate (3). A minute flow path (4) is formed in the substrate (3), enables a measurement object dispersed in a solvent of a sample solution in contact with the surfaces (3A, 3B) of the substrate (3) to pass therethrough, and can cause a measurement voltage in the longitudinal direction to be applied by means of the electrodes (1) and (2). The measurement object is identified on the basis of electrical characteristics of the measurement object at the time of passing through the minute flow path (4).

Description

Sensor, measurement system and measurement method

[0001] The present disclosure relates to sensors, measurement systems and measurement methods.

[0002] Known methods for detecting viruses, bacteria, microorganisms, or viroids (hereinafter simply referred to as viruses, etc.) include polymerase chain reaction (PCR) and immunochromatography. Other examples of such minute detection targets include disease markers for various diseases, including cancer, and extracellular vesicles for signal transduction (such as human- or microbial-derived exosomes, microvesicles, and apoptotic vesicles). These samples generally range in size from several tens to several hundreds of nanometers.

[0003] Meanwhile, as another detection method, a method of sensing viruses and the like using electrical measurement is being considered. One example of an electrical measurement method is a technique in which the target viruses and the like are dispersed in water and the viruses and the like are electrically detected as particles. From the viewpoint of preventing infectious diseases and the like and preventing their spread, there is a demand for detecting viruses and the like in environments such as indoors, livestock barns, and outdoors. The above-mentioned electrical measurement method is suitable for sensing in such environments (e.g., Patent Documents 1 and 2).

[0004] As an electrical measurement method, for example, a nanopore measurement technique has been proposed in which a analyte passing through a flow path to which an AC voltage is applied is measured (Patent Document 3). In this technique, a constant AC voltage is applied between electrodes arranged on either side of a path through which the analyte passes in a sample solution, and the AC characteristics when the analyte passes are measured, including the AC current value and the change in current phase relative to the voltage. The analyte is then measured and identified from waveforms showing the time change in the AC current value and the time change in the current phase.

[0005] JP 2020-202824 A JP 2020-098211 A JP 2023-119181 A

[0006] In the above-mentioned nanopore measurement method, the change in AC characteristics accompanying the passage of the particle to be measured, i.e., the change in AC current value and phase, is proportional to the ratio between the volume of the object to be measured and the volume of the nanopore space in the flow path to which the AC voltage is applied. Therefore, to improve the detection sensitivity of the object to be measured, it is necessary to make the volume of the nanopore space close to the volume of the particle to be measured. Therefore, the sensor that measures the object to be measured is configured to have a micro flow path.

[0007] Since the general nanopore measurement method is aimed at measuring biomolecules, silicon nitride (Si ３ N ４ ) and silicon dioxide (SiO ２ The sensors used are thin films of high-rigidity, high-brittle materials, such as graphene, with a thickness of several tens of nanometers, or monolayers such as graphene, with flow channels. These thin films are prone to brittle fracture, which has limited the practical application of nanopore measurements.

[0008] On the other hand, there is a need to establish a nanopore measurement method for measuring microorganisms such as viruses and bacteria, which have a volume approximately 100 times larger than that of biomolecules. Nanopore measurement methods for measuring microorganisms such as viruses and bacteria must overcome durability issues, such as the brittle fracture of thin films, as mentioned above, and improve the convenience of measurement.

[0009] The present disclosure has been made in consideration of the above circumstances, and aims to provide a sensor, a measurement system, and a measurement method that can quickly and accurately identify a minute measurement object with a simple configuration.

[0010] A sensor according to one aspect of the present disclosure comprises a dielectric member, a first electrode made of a conductive material formed on a first surface of the dielectric member, a second electrode made of a conductive material formed on a second surface of the dielectric member, and a microchannel formed in the dielectric member through which a measurement object dispersed in a solvent of a sample solution contacting the first and second surfaces of the dielectric member can pass, and through which a measurement AC voltage can be applied in the longitudinal direction by the first electrode and the second electrode, and the measurement object is identified based on the AC characteristics of the measurement object when the measurement AC voltage is applied and the measurement object passes through the microchannel.

[0011] A measurement system according to one aspect of the present disclosure includes a sensor for measuring a measurement object, a measurement unit for measuring AC characteristics of the measurement object by applying a measurement AC voltage to the sensor, and a processing unit for identifying the measurement object based on the AC characteristics measured by the measurement unit. The sensor includes a dielectric member, a first electrode made of a conductive material formed on a first surface of the dielectric member, a second electrode made of a conductive material formed on a second surface of the dielectric member, and a microchannel formed in the dielectric member through which the measurement object dispersed in a solvent of a sample solution contacting the first and second surfaces of the dielectric member can pass, and through which the measurement AC voltage can be applied in the longitudinal direction by the first electrode and the second electrode. The measurement system identifies the measurement object based on the AC characteristics of the measurement object when the measurement object passes through the microchannel with the measurement AC voltage applied.

[0012] A measurement method according to one aspect of the present disclosure applies a measurement AC voltage to a first electrode made of a conductive material formed on the first surface of a dielectric member and a second electrode made of a conductive material formed on the second surface of the dielectric member in the longitudinal direction of a microchannel formed in the dielectric member, through which a measurement object dispersed in a solvent of a sample solution contacting the first and second surfaces of the dielectric member can pass, and identifies the measurement object based on the AC characteristics of the measurement object when the measurement object passes through the microchannel with the measurement AC voltage applied.

[0013] The present disclosure makes it possible to provide a sensor, a measurement system, and a measurement method that can quickly and accurately identify a minute measurement object with a simple configuration.

[0014] 1 is a diagram schematically showing the configuration of a measurement system according to a first embodiment. FIG. 2 is a perspective view schematically showing the configuration of a sensor. FIG. 3 is a diagram showing the connection relationship between a sensor and a measurement unit. FIG. 4 is a perspective view showing a droplet formed on a sensor. FIG. 5 is a diagram showing a flow passing through a microchannel. FIG. 6 is a diagram schematically showing an example configuration of a measurement unit. FIG. 7 is a diagram showing an example of a solution holding structure provided on a sensor. FIG. 8 is a flowchart of measurement of a measurement object with a measurement system according to a first embodiment. FIG. 9 is a graph showing AC characteristics measured with a measurement system according to a first embodiment. FIG. 10 is a graph showing the relationship between particle diameter of a measurement object and change in current value. FIG. 11 is a diagram showing the particle diameter distribution of bacteria. FIG. 12 is a diagram showing a confusion matrix showing the classification performance of bacteria. FIG. 13 is a diagram showing a confusion matrix showing the classification performance of inactivated viruses. FIG. 14 is a diagram showing a confusion matrix showing the classification performance of exosomes. FIG. 15 is a diagram showing a confusion matrix showing the classification performance of pollen. FIG. 16 is a diagram showing an example of sensor holding in electrophoresis. FIG. 17 is a diagram showing the movement direction of a measurement object in electrophoresis and the waveform observed. FIG. 18 is a diagram showing an example of measurement results of a current waveform by electrophoresis. FIG. 19 is a diagram showing a configuration of a sensor according to a third embodiment. FIG. 19 is a diagram showing how to use a sensor according to a third embodiment. Fig. 10 is a graph showing the results of bacteria count measurement. Fig. 11 is a front view schematically showing the configuration of a sensor according to a fourth embodiment. Fig. 12 is a cross-sectional view showing the distance between electrodes of a sensor according to the first embodiment. Fig. 13 is a cross-sectional view showing the distance between electrodes of a sensor according to the fourth embodiment. Fig. 14 is a front view schematically showing the configuration of a sensor according to a fifth embodiment. Fig. 15 is a view showing a first modified example of electrode arrangement. Fig. 16 is a view showing a second modified example of electrode arrangement.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same elements are designated by the same reference numerals, and redundant explanations will be omitted as necessary.

[0016] Hereinafter, when referring to one embodiment, it means that the invention can be applied to any one of the embodiments described below or a combination of two or more embodiments, and is not limited to a specific embodiment.

[0017] Embodiment 1 Here, a measurement system for measuring microparticulate measurement targets such as viruses, bacteria, microorganisms, or viroids (hereinafter simply referred to as viruses, etc.) mainly bacteria and particles of similar size to bacteria using a nanopore measurement method will be described. Fig. 1 is a diagram schematically showing the configuration of a measurement system 100 according to the first embodiment. The measurement system 100 according to the first embodiment includes a sensor 10, a measurement unit 30, and a signal processing unit 40.

[0018] The sensor 10 is configured as a sensor for measuring a measurement target dispersed in a solution. FIG. 2 is a perspective view schematically illustrating the configuration of the sensor 10. In FIG. 2, the vertical direction from bottom to top of the paper is defined as the Y direction. The horizontal direction perpendicular to the Y direction and extending to the right is defined as the X direction. The direction perpendicular to the X and Y directions is defined as the Z direction. Because FIG. 2 is a perspective view, the X direction is shown as a direction slightly biased upward and to the right with respect to the horizontal direction of the paper, and the Z direction is shown as a direction biased downward and to the right with respect to the normal direction to the paper. Electrodes 1 and 2 are provided on opposite surfaces of a substrate 3, which is a flat, non-conductive member.

[0019] The sensor 10 has electrodes 1 and 2 and a substrate 3. In FIG. 2, the substrate 3 is configured as a rectangular, flat-plate-shaped dielectric member whose main surface is the X-Y plane. To prevent the electrodes 1 and 2 from peeling off, the substrate 3 is preferably made of a material that has dimensional stability equivalent to that of, for example, silicon or glass, and in particular a low coefficient of linear expansion, as well as excellent mechanical strength, smoothness, and flexibility. Furthermore, since the substrate 3 is sandwiched between the electrodes 1 and 2, it is preferably made of a dielectric material that has excellent electrical properties, in particular a low dielectric constant. Therefore, polyimide is used here as the material for the substrate 3. The polyimide used may, for example, have a linear expansion coefficient of 3 ppm / K or less, an arithmetic mean roughness of the surface of approximately 0.5 nm, a relative dielectric constant of 3.3, and a volume resistivity of 10 １６It is desirable that the resistivity is larger than Ωcm. The thickness of the substrate 3 is set to 15 μm.

[0020] Electrode 1 is formed on surface 3A on the +Z side of substrate 3. Electrode 2 is formed on surface 3B on the -Z side of substrate 3. Electrode 1 is also referred to as the first electrode, and electrode 2 is also referred to as the second electrode. Surface 3A is also referred to as the first surface, and surface 3B is also referred to as the second surface. In this configuration, electrodes 1 and 2, which are arranged opposite each other across substrate 3, are configured as electrodes of the same shape and dimensions. Electrode 1 is composed of a ring electrode 1A provided at the center of substrate 3 and a lead-out wiring 1B extending from ring electrode 1A in the Y direction. Similarly, electrode 2 has the same configuration as electrode 1 and is composed of a ring electrode 2A provided at the center of substrate 3 and a lead-out wiring 2B extending from ring electrode 2A in the Y direction. Electrodes 1 and 2 are arranged so that ring electrode 1A and ring electrode 2A are concentric. The lead-out wiring is also simply referred to as a wiring portion. The lead-out wiring 1B is also referred to as a first wiring portion, and the lead-out wiring 2B is also referred to as a second wiring portion.

[0021] In this embodiment, electrodes 1 and 2 are configured as thin-film electrodes made of silver (Ag). Electrodes 1 and 2 may be formed on substrate 3 using various fabrication methods. For example, electrodes 1 and 2 may be fabricated by patterning the shapes of electrodes 1 and 2 with Ag nanoink (KGK NANO AGK104, Kishu Giken Kogyo Co., Ltd.) using an inkjet processing device (Subfemto Inkjet Processing Device, SIJ Technology Co., Ltd.), followed by sintering at 180°C for 90 minutes. Note that the heat resistance temperature of Xenomax, which constitutes substrate 3, is 500°C or higher, allowing electrodes 1 and 2 to be fabricated without deformation even at processing temperatures that would cause warping in general polyimides. Furthermore, because polyimides such as Xenomax are brown and transparent, electrodes 1 and 2 facing each other across substrate 3 can be seen through, making it easy to align the centers of ring electrodes 1A and 2A. The method for fabricating the electrodes is not limited to this, and the electrodes may be fabricated using a patterning method such as photolithography and a film formation method such as vacuum deposition, chemical vapor deposition (CVD), plating, etc. The electrodes may also be fabricated by applying a general technique for fabricating wiring on a substrate such as a flexible printed wiring board.

[0022] A microchannel 4, which is a passage hole for the object to be measured, is formed in the substrate 3 so as to be concentric with the ring electrodes 1A and 2A. The microchannel 4 may be formed in the substrate 3 using various manufacturing methods. For example, the microchannel 4 may be formed in the substrate 3 using a laser processing machine. In this case, for example, while observing the inner regions of the ring electrodes 1A and 2A with an optical microscope, the microchannel 4 may be formed at the center position of the ring electrodes 1A and 2A by irradiating the substrate 3 with a continuous wave (CW) laser beam having a wavelength of 405 nm, an optical output of 70 mW, and a TEM00 mode for 0.1 seconds using an objective lens with an NA of 0.45.

[0023] The diameter φ0 of the microchannel 4 and the inner and outer diameters φ1 and φ2 of the ring electrodes 1A and 2A can be designed to any value suitable for the dimensions of the object to be measured. In this embodiment, bacteria are assumed to be the object to be measured, and their dimensions are on the order of several μm. Accordingly, in this embodiment, the diameter φ0 of the microchannel 4 is set to 3 μm, taking into consideration the detection sensitivity of general bacteria and preventing clogging of the microchannel 4. Furthermore, taking into consideration the formation of droplets, which will be described later, the inner diameter φ1 of the ring electrodes 1A and 2A is set to 1 mm, and the outer diameter φ2 is set to 3 mm.

[0024] The electrodes 1 and 2 are provided to apply an AC voltage in the longitudinal direction of the microchannel 4, and have been described above as having a ring-shaped portion surrounding the microchannel 4. However, the shape of the electrodes is not limited to this, and various ring-shaped electrodes may be used, such as circular, elliptical, other closed curved, or closed polygonal electrodes, as long as they surround the microchannel 4. Furthermore, as long as an AC voltage can be suitably applied to the microchannel 4, partially open ring-shaped electrodes such as partially open curved electrodes like a C-shape or partially open polygonal electrodes may be used. Furthermore, as long as an AC voltage can be suitably applied to the microchannel 4, the electrodes are not limited to closed or open ring-shaped electrodes, and various shapes may be used.

[0025] The microchannel 4 is preferably a hole having a circular cross-sectional shape when viewed along the longitudinal direction (Z direction); however, various cross-sectional shapes may be used as long as it penetrates the substrate and allows the measurement target to pass through. Furthermore, the cross-sectional dimensions of the microchannel 4 are preferably at least large enough to allow the measurement target to pass through. Furthermore, the cross-sectional dimensions of the microchannel 4 are preferably several times larger than the measurement target, for example, three times larger. The microchannel 4 may also have a cross-sectional shape that changes along the longitudinal direction. For example, the microchannel 4 may have a cone-like shape, in which the cross-sectional dimensions increase from one longitudinal end to the other. When the cross-section of the microchannel 4 is circular, for example, the microchannel 4 may be formed as a truncated cone-like channel, in which the diameter of the circular cross-section increases from one longitudinal end to the other.

[0026] The measurement unit 30 is configured to apply an AC voltage used to measure the object to the sensor 10 and measure changes in the AC voltage. Fig. 3 is a diagram showing the connection relationship between the sensor 10 and the measurement unit 30. A wire 51 connects the lead-out wiring 2B of the sensor 10 to one terminal 31 of the measurement unit 30. A wire 52 connects the lead-out wiring 1B of the sensor 10 to the other terminal 32 of the measurement unit 30.

[0027] Next, the relationship between the sensor 10 and the object to be measured will be described. In this configuration, the measurement unit 30 measures the AC characteristics when the object to be measured 5 passes through the microchannel 4 while applying an AC voltage to the electrodes 1 and 2. The measurement unit 30 then identifies the object to be measured 5 based on changes in the measured AC characteristics, i.e., changes in the waveform of the measured AC current. Note that, although an example of measuring the waveform of an AC current as the AC characteristics will be described here, the waveform of an AC voltage may also be measured if necessary.

[0028] A method for contacting the sample solution with the microchannel 4 will now be described. Fig. 4 is a perspective view showing a droplet formed on the sensor 10. In Fig. 4, the electrode 1 of the sensor 10 faces upward, and a droplet 6 of the sample solution containing the measurement object 5 dispersed in a solvent 7 is formed so as to cover the ring electrodes 1A and 2A.

[0029] In this configuration, droplets 6 can be formed and held by utilizing the difference in surface tension between the hydrophobic polyimide substrate 3 and the hydrophilic silver electrodes 1 and 2. For example, droplets 6 can be formed by dropping a sample solution onto the center of each of the ring electrodes 1A and 2A while turning the sensor 10 upside down. For example, to improve hydrophilicity, the interiors of the silver electrodes 1 and 2 may be hydrophilized by irradiating them with vacuum ultraviolet light or atmospheric plasma. Alternatively, the interiors of the electrodes 1 and 2 may be treated with a hydrophilic coating agent. Even if the electrode surfaces are coated with a hydrophilic coating, this configuration can still perform measurements without any problems because it is designed for AC measurements. This is clearly an advantage of this configuration, which performs AC measurements.

[0030] In this case, it is desirable that the ring electrodes 1A and 2A be formed with sufficiently small dimensions so that the dropped sample solution does not spill. On the other hand, as the size of the droplet 6 becomes smaller, the ratio of surface area to volume increases, resulting in a higher solvent evaporation rate. In other words, there is a trade-off between the structural stability of the droplet 6 and the evaporation rate. Therefore, assuming a realistic measurement time of several minutes, we investigated an appropriate droplet size so that the evaporation error in the measurement would be within 0.1% in an environment with a humidity of 50% and a temperature of 23°C. Accordingly, as described above, the inner diameter φ1 of the ring electrodes 1A and 2A was set to 1 μm and the outer diameter φ2 to 3 μm. Under these conditions, the amount of sample solution dropped onto each of the ring electrodes 1A and 2A was 20 to 40 μL.

[0031] The droplet formation method described above is merely illustrative. For example, when sensor 10 is immersed in a sample solution containing a dispersed sample 5 and then pulled up vertically, droplets 6 remain inside ring electrodes 1A and 2A due to the difference in hydrophilicity between electrodes 1 and 2 and substrate 3. Droplets 6 similar to those described above may then be formed by rotating sensor 10 so that the main surface of substrate 3 is perpendicular to the horizontal direction to prevent droplets 6 from spilling out. This droplet formation method can shorten the work time and more easily form droplets than the above-described method of forming droplets on both sides of the substrate.

[0032] As described above, bacteria are assumed as the measurement target, but the measurement target is not limited to this. For example, the measurement target may be a biological sample such as a virus or a microorganism, or a substance other than a biological sample, as long as it is an object that can be dispersed in the solvent 7. Furthermore, various solvents such as ionic liquids and water may be used as the solvent 7.

[0033] As an example of a method for passing the measurement object 5 in the formed droplet 6 through the microchannel 4, a gravity-driven method will be described. FIG. 5 is a diagram showing a flow passing through the microchannel 4. When the sensor 10 is held with the electrode 1 facing upward after the droplet 6 has been formed, gravity causes a minute flow through the microchannel 4 from the droplet formed on electrode 1 toward the droplet formed on electrode 2. This flow causes the measurement object 5 to pass through the microchannel 4 from the droplet formed on electrode 1 toward the droplet formed on electrode 2.

[0034] The sensor may also be provided with a solution retention structure for retaining the sample solution. FIG. 6 shows an example of a solution retention structure provided on a sensor. In this example, a cylindrical solution retention member 71 made of a non-conductive material is provided concentrically with the electrode 1 and the microchannel 4 on the surface 3A of the substrate 3 on which the electrode 1 is provided. A cylindrical solution retention member 72 made of a non-conductive material is provided concentrically with the electrode 1 and the microchannel 4 on the surface 3B of the substrate 3 on which the electrode 2 is provided. Here, the solution retention members 71 and 72 are referred to as a solution retention structure 70. Dropping the sample solution onto the center of the solution retention member 71 thus provided allows a larger amount of sample solution to be retained on the sensor compared to the examples of FIGS. 4 and 5 . This reduces the effects of sample solution evaporation, and by increasing the amount of sample solution, the driving force for creating a flow in the microchannel 4 can be enhanced. Furthermore, the solution retention member 72 provided on the opposite surface can also retain a larger amount of sample solution due to surface tension than the examples of FIGS. 4 and 5 , thereby also reducing the effects of sample solution evaporation.

[0035] The solution holding structure shown in FIG. 6 is merely an example, and various structures may be used as long as they are provided on one or both of the substrate and the electrode and can hold the sample solution.

[0036] As described above, under conditions in which the object to be measured 5 passes through the microchannel 4, the measurement unit 30 measures the AC characteristics of the object to be measured 5, and the signal processing unit 40 identifies the object to be measured 5 using the measured AC characteristics.

[0037] The measuring unit 30 may have any configuration capable of measuring the AC characteristics of the measurement object 5. The measuring unit 30 is configured to be able to apply to the electrodes 1 and 2 an AC voltage having a frequency of several kHz to several GHz, preferably 1 kHz to 100 MHz, and more preferably 1 MHz to 10 MHz.

[0038] To ensure noise resistance, the measurement unit 30 may measure the AC voltage using a lock-in amplifier, which is excellent at detecting small repetitive signals. For example, the measurement unit 30 can use the lock-in amplifier to extract the in-phase component of the AC voltage and a phase component that is out of phase with the in-phase component. In other words, the measurement unit 30 may obtain the measured AC current value (or synthetic impedance) and the change in the phase of the current relative to the voltage.

[0039] 7 is a diagram showing a schematic configuration example of the measurement unit 30. The measurement unit 30 has a signal source 33 and a lock-in amplifier 34. The signal source 33 is inserted between a terminal 31 of the measurement unit 30 connected to the electrode 2 and an input terminal IN1 of the lock-in amplifier. The signal source 33 generates an AC voltage V of an arbitrary frequency to be applied between the electrode 1 and the electrode 2. ＡＣ The input terminal IN2 of the lock-in amplifier is connected to a terminal 32 of a measuring unit 30 which is connected to the electrode 1.

[0040] The configuration and operation of the lock-in amplifier 34 are the same as those of a general lock-in amplifier. Here, the lock-in amplifier 34 measures AC characteristics, that is, a waveform showing the time change of the AC current value and a waveform showing the phase of the AC current. The lock-in amplifier 34 measures the waveform W Ａ and a waveform W indicating the phase of the AC current. Ｐ and output to the signal processing unit 40.

[0041] The signal processing unit 40 identifies the object to be measured based on a waveform showing the time change of the AC current value and a waveform showing the phase of the AC current, which indicate the AC characteristics measured by the measurement unit 30. The signal processing unit 40 receives the waveform W Ａ and a waveform W indicating the phase of the AC current ＰReceive.

[0042] The signal processing unit 40 may identify the object to be measured 5 by applying machine learning, for example. The signal processing unit 40 may construct a trained model that can be used to identify an unknown object to be measured by performing supervised learning in which the AC characteristics of a training object to be measured and information about the training object to be measured are input to the model as training data. In this way, the signal processing unit 40 can identify the object to be measured 5 by using the output from the trained model obtained by inputting the measured AC characteristics into the trained model. It goes without saying that, even in this case, the measured AC current value and phase may also be input as the AC characteristics.

[0043] In machine learning, for example, a neural network may be used as a model. For example, machine learning using a convolution neural network (CNN) or a long short term memory (LSTM) may be applied.

[0044] Next, a description will be given of the operation when measuring the measurement target 5 using the measurement system 100 according to this embodiment.

[0045] First, the measurement object 5 dispersed in the solvent 7 is caused to flow through the microchannel 4 by the droplet method described above (step S1). Next, the measurement unit 30 applies an AC voltage to the electrodes 1 and 2 (step S2). Here, for example, the measurement unit 30 applies an AC voltage V having a frequency of 1 kHz to 100 MHz. ＡＣ is applied to the electrodes 1 and 2. Thereafter, the AC characteristics are measured (step S3), and the measurement object 5 is identified based on the measured AC characteristics (step S4).

[0046] In the above description, the measurement object 5 dispersed in the solvent 7 is caused to flow through the microchannel 4, and then an AC voltage is applied to the electrodes 1 and 2. However, this is merely an example. The measurement object 5 dispersed in the solvent 7 may be caused to flow through the microchannel 4 after applying an AC voltage to the electrodes 1 and 2.

[0047] As described above, this configuration makes it possible to realize a sensor in which electrodes are provided on a substrate with sufficient mechanical strength, thereby solving the problem of fracture of highly rigid and brittle thin films such as silicon nitride that occurs in general nanopore measurement methods, and providing a sensor with excellent durability.

[0048] In measurements using the AC nanopore method, which involves applying an AC voltage to perform measurements, it is desirable to reduce the capacitance of the dielectric substrate and increase the cutoff frequency from the perspective of broadening the frequency band. Therefore, according to this configuration, compared to general nanopore measurement methods, the dielectric substrate can be made thicker, which is advantageous in terms of broadening the frequency band.

[0049] Furthermore, because the substrate can be made thick, there are more options for the material that makes up the substrate, the structure of the sensor, and the manufacturing method, which results in greater freedom in sensor design.

[0050] Below, an example of particle diameter measurement of a measurement object in this configuration will be described. In the following example, a Zurich Instruments MFIA 5 MHz was used as a measurement device including a lock-in amplifier. The low-pass filter in the lock-in amplifier was set to fifth order, with a bandwidth of 1 kHz. The measurement voltage was 0.5 Vpp. When particle drive by electrophoresis was required, a DC bias voltage of up to 2 V was applied. A tweezers probe (L2001, HIOKI) was used to connect the sensor to the measurement device.

[0051] In the signal processing unit 40, a trained model using a CNN was constructed. In the following examples, since the amount of data obtained by CNN measurements differs for each bacterium, a greater weight was assigned to bacteria with fewer data sets to prevent a decline in generalization performance due to data heterogeneity. The training data was a one-dimensional array of the values ​​of each point constituting each waveform, which was used as direct input layer data. The CNN was constructed by combining six convolutional layers, a batch normalization layer, and a pooling layer. The LeRU function was used as the activation function. During training, 60% of the total measured data was used as training data, 20% as validation data, and the remaining 20% ​​as test data. The generalization performance of the constructed classifier was evaluated using five-fold cross-validation, with the accuracy rate of the predicted value used as the evaluation index.

[0052] The solvent used was phosphate buffered saline (17-516Q, Lonza) with a pH of 7.4 and a conductivity of 17 mS / cm, and the substance to be measured was dispersed in this solvent to prepare a sample solution. To prevent aggregation of the substance to be measured, the sample solution was stirred for at least 10 seconds using a vortex mixer immediately before measurement.

[0053] Example 1: Measurement of a single particle Figure 9 is a graph showing AC characteristics measured with the measurement system according to this embodiment, using a lock-in amplifier. That is, Figure 9 shows the time response waveforms of the current and phase change. In this example, polystyrene particles (CPC1000) with a diameter of 940 nm were used as the measurement object.

[0054] In Figure 9, the upper waveform shows the absolute value of the current, and the lower waveform shows the phase of the current relative to the applied voltage. Because the path through which the AC voltage is applied is blocked by particles passing through the microchannel 4, the observed current decreases, resulting in a downward current spike waveform. Focusing on the phase, on the other hand, an upward spike waveform (advancing in phase) occurs as the object to be measured passes, indicating that the CPC1000 particles being measured exhibit a capacitive response. Furthermore, the current change and phase change occur in synchronization, indicating that these changes originate from the same particle. Thus, with this configuration, the event of the object to be measured passing through the microchannel 4 is observed as a waveform in which the current change and phase change appear in synchronization.

[0055] Example 2: Measurement of particle diameter In this measurement, the change in current is proportional to the particle volume, i.e., the cube of the particle diameter. For example, when the particle diameter is reduced to 1 / 10, the signal intensity, i.e., the change in current, becomes 1 / 1000. Therefore, as the particle diameter becomes smaller, the particle size that can be measured with a single aperture diameter becomes increasingly dependent on various noises and the configuration of the measurement system. Therefore, in this embodiment, a lock-in amplifier with a large dynamic reserve (tolerable noise current / measurement current) was used to evaluate the range of particle diameters that can be measured with an aperture diameter of 3 μm, particularly how small particles can be measured.

[0056] 10 is a graph showing the relationship between the particle diameter of the object to be measured and the change in current value. In FIG. 10, the horizontal axis shows the particle diameter, and the vertical axis shows the amount of change in current value. In FIG. 10, the R of the approximation curve obtained by fitting the measurement value using a cubic regression equation is ２Since the value was 0.999 or greater, it was confirmed that the measured current value conformed to the cube law of the analytically obtained particle diameter. It was also confirmed that particles with diameters ranging from approximately 300 nm to 3 μm could be measured with a single pore size. This means that signals with a 1000-fold difference in intensity can be measured linearly, demonstrating the advantages of the lock-in amplifier. Therefore, this configuration can achieve measurements over a wide particle size range compared to other measurement techniques. Furthermore, since particles with a diameter of 3 μm could be passed through a microchannel 4 with an inner diameter of 3 μm without clogging the microchannel 4, it was estimated that the actual pore size was slightly larger than 3 μm within the error range of SEM observation.

[0057] Example 3: Size Measurement and Classification of Bacteria Size measurements of bacteria were performed under the same conditions as in Example 2. In this example, ten types of bacteria obtained from Akita Konno Shoten Co., Ltd. were used as measurement targets. The scientific names and model numbers of the ten types of bacteria are as follows: Lacrobacillus plantarum (L1315), Enterococcus faecalis (L1390), Leuconostoc mesenteroid (L1789), Pediococcus pentosaceus (L4140), Lacrococcus lactis (L1181), Lacrobacillus fermentum (L1295), Weissella paramesentero (L1790), Enterococcus faecium (L1995), Pediococcus acidilactic (L3324), and Lactobacillus pentosus (L1317). To reduce the influence of variations in growth rate due to the type of bacteria, these bacteria were cultured in MRS (de Man, Rogosa, Sharpe) medium (Lactobacillus MRS Broth, Becton, Dickinson) at 30°C for approximately 24 hours, and then the medium was replaced with the measurement solution to prepare a sample solution.

[0058] Figure 11 shows the particle size distribution of bacteria. Because the number of detected bacteria varies depending on the type of bacteria, the values ​​on the vertical axis were normalized so that the total number of detected bacteria for each bacteria was 100%. Because bacteria are non-spherical, particle diameters were calculated as equivalent sphere diameters of equal volume and calibrated using data from the CPC1000 (particle diameter 940 nm). In this example, bacterial particle diameters ranged from approximately 800 nm to 1.5 μm. The overlap in particle sizes between bacteria indicates that it is difficult to distinguish between bacteria based solely on particle size information.

[0059] In this example, the time required to measure the particle size of each type of bacteria was approximately several minutes, from the stage of dripping the sample solution onto the sensor to forming droplets to the completion of measurement. This confirmed that this configuration allows for quick and easy particle size measurement of measurement targets.

[0060] The particle size measurements of the above-mentioned 10 types of bacteria were performed using the same sensor, but clogging of the microchannel 4 did not occur often during the measurements. Furthermore, even if clogging of the microchannel 4 did occur, the clogging could be cleared by simply mechanically shaking the sensor slightly with tweezers or the like, and remeasurement was possible. In this case, the deviation of the measurement signal before and after recovery was less than 10 ppm, so it was estimated that no partial clogging or narrowing had occurred.

[0061] Next, the classification of bacteria performed by the signal processing unit 40 in Example 3 will be described. FIG. 12 is a diagram showing a confusion matrix representing the classification performance of bacteria. In FIG. 12, the horizontal axis represents predicted values, and the vertical axis represents correct values. The values ​​in the matrix represent the accuracy rate, corresponding to the color intensity. In this matrix, the darker the diagonal line, the higher the accuracy rate and the better the classification performance. When 10 types of bacteria were classified using the above-described CNN-based classifier, an accuracy rate of 85.7%, a precision (also referred to as precision), a sensitivity (also referred to as recall), and an F1 value of 85.7% were achieved. Therefore, it was confirmed that the type of bacteria can be identified with high accuracy by combining the measurement according to this embodiment with bacterial classification using a CNN classifier.

[0062] Example 5: Classification of inactivated viruses In this example, four types of inactivated viruses, namely, two types of influenza A (H1N1 and H3N2), influenza B, and respiratory syncytial (RS) virus, were used as the measurement objects.

[0063] Fig. 13 is a diagram showing a confusion matrix representing the classification performance of inactivated viruses. In Fig. 13, as in Fig. 12, the horizontal axis represents predicted values ​​and the vertical axis represents correct values. When four types of inactivated viruses were classified using the classifier using the above-mentioned CNN, the accuracy rate was 98.64%, the precision was 98.60%, the sensitivity was 98.86%, the specificity was 99.54%, and the F1 value was 98.72%. Therefore, even when the measurement target was an inactivated virus, the type of inactivated virus could be identified with high accuracy by combining the measurement according to this embodiment with classification using a CNN classifier.

[0064] Example 6: Classification of exosomes In this example, seven types of exosomes were used as measurement targets: COLO1 (human colon cancer), MM1 (human melanoma), SK-N-SH (human neuroblastoma), HCT116 (human colon cancer), PC3 (human prostate cancer grade IV), A549 (lung cancer), and K-562 (chronic myeloid leukemia (pleural effusion)).

[0065] Figure 14 shows a confusion matrix representing the classification performance of exosomes. In Figure 14, as in Figure 12, the horizontal axis represents predicted values ​​and the vertical axis represents correct values. When seven types of exosomes were classified using the above-described CNN-based classifier, the results were an accuracy rate of 83.37%, precision of 84.70%, sensitivity of 85.63%, specificity of 97.19%, and F1 value of 84.54%. Therefore, even when the measurement target was a smaller exosome, the type of exosome could be identified with high accuracy by combining the measurement according to this embodiment with classification using a CNN classifier.

[0066] Example 7: Pollen Classification In this example, three types of pollen, club moss, pine, and cedar, were used as the measurement objects. FIG. 15 is a diagram showing a confusion matrix representing the pollen classification performance. When the three types of pollen were classified using the classifier using the above-mentioned CNN, the accuracy rate was 98.74%, the precision was 98.60%, the sensitivity was 98.76%, the specificity was 99.40%, and the F1 value was 98.69%. Therefore, even if the measurement object was pollen, the type of pollen could be identified with high accuracy by combining the measurement according to this embodiment with classification using a CNN classifier.

[0067] Embodiment 2 In the first embodiment, the gravity-driven method was described as an example of a method for generating a flow passing through the microchannel 4. However, in the gravity-driven method, when the concentration of the analytes 5 dispersed in the sample solution is low, the number of analytes 5 passing through the microchannel 4 is reduced and the movement speed cannot be controlled, which may result in a decrease in measurement accuracy. Furthermore, to improve measurement accuracy, it is necessary to perform measurements for a long time. This reduces the throughput of the measurement work.

[0068] Therefore, in this embodiment, an electrophoresis method will be described in which the number and movement speed of the measurement objects 5 passing through the microchannel 4 can be adjusted. In this embodiment, a DC voltage V Ｄ By applying a voltage, the object to be measured 5, which is positively or negatively charged, is driven.

[0069] For example, the signal source 33 of the measuring unit 30 generates an AC voltage V ＡＣ and DC voltage V for electrophoresisＤ and may be superimposed and applied to the electrodes 1 and 2. In this case, the DC voltage V Ｄ There is no need to provide a separate power source for applying the DC voltage V, and the measurement object 5 can be driven by the electrophoresis method with a simple configuration. Ｄ The method of applying the voltage is not limited to this. A power source may be separately provided to apply a DC voltage V between the electrode 1 and the electrode 2. Ｄ may be applied.

[0070] As a result, the DC voltage V Ｄ The object to be measured 5 can be driven in a specific direction and introduced into the microchannel 4. Specifically, when the object to be measured 5 is positively charged, by applying a DC voltage for electrophoresis so that electrode 1 becomes the positive electrode and electrode 2 becomes the negative electrode, the positively charged object to be measured 5 can be moved from electrode 1 to electrode 2 via the microchannel 4. When the object to be measured 5 is negatively charged, by applying a DC voltage for electrophoresis so that electrode 1 becomes the negative electrode and electrode 2 becomes the positive electrode, the negatively charged object to be measured 5 can be moved from electrode 1 to electrode 2 via the microchannel 4.

[0071] The DC voltage V applied to the electrodes 1 and 2 Ｄ By adjusting the size and time of the flow, it is possible to adjust the speed at which the measurement object 5 passes through the minute flow channel 4. In this embodiment, the number of measurement objects 5 that pass through the minute flow channel 4 at the same time is, in principle, one.

[0072] As described above, according to the electrophoresis method, a DC voltage V applied between the electrode 1 and the electrode 2 Ｄ This allows the measurement objects 5 to be introduced into the microchannel 4 in a number and at a speed that ensures sufficient measurement accuracy.

[0073] According to the electrophoresis method, a DC voltage V applied between the electrode 1 and the electrode 2 Ｄ By switching the polarity of the electrode, the object to be measured 5 flowing through the minute flow path 4 can be moved back and forth. This makes it possible to further improve the measurement accuracy of the object to be measured 5.

[0074] Furthermore, the voltage that drives the measurement target 5 is not limited to a DC voltage. That is, the AC voltage V applied to measure AC characteristics is ＡＣ The object 5 to be measured may be moved back and forth by applying a driving AC voltage having a frequency lower than that of the AC voltage V applied to measure the AC characteristics. ＡＣ It may be applied in a superimposed manner.

[0075] In this configuration, the driving voltage can be applied using the electrodes 1 and 2 for applying the AC voltage. Therefore, there is no need to add any additional electrodes for applying the driving voltage, and the measurement object can be driven by electrophoresis without changing the configuration of the sensor 10. Furthermore, in the electrophoresis method, concentration polarization is induced by the driving voltage and the state can be measured by AC, so the surface potential of the measurement object 5 can be measured more accurately.

[0076] In the gravity-driven method, the object to be measured 5 is driven by the flow of the solvent 7 caused by gravity, and therefore the sensor 10 is described as being held so that the main surface of the substrate 3 is approximately perpendicular to the vertical direction. However, in the electrophoresis method, the sensor 10 can be driven by a DC voltage, which allows for greater flexibility in holding the sensor 10. FIG. 16 is a diagram showing an example of how the sensor 10 is held in the electrophoresis method. In the electrophoresis method, as shown in FIG. 16, for example, the sensor 10 may be held so that the main surface of the substrate 3 is approximately perpendicular to the horizontal direction. Even in this case, the object to be measured 5 can pass through the microchannel 4 in the horizontal direction by applying a DC voltage.

[0077] 16, the sensor 10 can be held, which allows for easier formation of droplets 6. For example, when the sensor 10 is immersed in a sample solution 9 containing a dispersed substance 5 and then pulled out, the droplets 6 can remain inside the ring electrodes 1A and 2A due to the difference in hydrophilicity between the electrodes 1 and 2 and the substrate 3. This allows for easier and faster measurement preparation.

[0078] Next, an example using electrophoresis will be described. Here, the measurement conditions and the measurement method are the same as those in the example of the first embodiment, except that electrophoresis is applied.

[0079] Example 8: Electrophoresis Figure 17 is a diagram schematically illustrating the movement direction of the measurement object in electrophoresis and the observed waveform. The left side of Figure 17 is a conceptual diagram of the movement direction of the measurement object, showing the movement direction of a positively or negatively charged measurement object. The right side of Figure 17 shows the relationship between the position of the measurement object in the microchannel 4 and the current waveform. As shown on the right side of Figure 17, the microchannel 4 is formed as a fine hole, for example, by a laser processing machine, and therefore the shape of the hole, for example, the diameter, is expected to be non-uniform. Therefore, in Figure 17, the microchannel 4 is shown as having a funnel-like shape whose diameter widens from the left side of the page to the right side of the page.

[0080] In this state, when the positively charged analyte 5A and the negatively charged analyte 5B are driven, the positively charged analyte 5A passes through the microchannel 4 in the left direction, i.e., from the larger diameter portion of the microchannel 4 to the smaller diameter portion. On the other hand, the negatively charged analyte 5B passes through the microchannel 4 in the right direction, i.e., from the smaller diameter portion of the microchannel 4 to the larger diameter portion. Therefore, the AC electric field profile through which the positively charged analyte 5A passes and the AC electric field profile through which the negatively charged analyte 5B passes are mutually inverted. As a result, the current value waveform measured for the positively charged analyte 5A and the current value waveform measured for the negatively charged analyte 5B are obtained as waveforms that are mutually inverted in time. Therefore, according to electrophoresis, the movement direction of the measured particles and the positive and negative zeta potentials can be simultaneously obtained.

[0081] Although the microchannel 4 has been described as having a funnel-like shape here, the shape of the microchannel 4 is not limited to this. The microchannel 4 may be formed as a cylindrical channel with a uniform diameter, or may have various shapes such as an hourglass shape with a wide diameter at both ends and a narrow diameter in the middle.

[0082] 18 shows an example of the measurement results of a current waveform by electrophoresis. In this example, particles with a diameter of 1 μm that are negatively charged by being modified with a carboxyl group (—COOH) and similar particles that are negatively charged by being modified with an amino group (—NH ２ The measurement was performed by dispersing 1 μm diameter particles, which were positively charged by modifying them with ZnO, into a sample solution. The direction of particle movement was reversed depending on the polarity of the particle charge, and it was confirmed that the current waveforms obtained were inverted in time.

[0083] In the first and second embodiments, droplets 6 are attached to the sensor 10 for measurement, resulting in a transient and short-term measurement. However, in actual measurements, it is anticipated that continuous measurement of a measurement target dispersed in a larger amount of sample solution (so-called in-situ measurement) may be required. Therefore, in this embodiment, a sensor capable of continuous measurement of a measurement target dispersed in a larger amount of sample solution will be described.

[0084] 19 is a diagram schematically illustrating the configuration of a sensor 20 according to the third embodiment. The sensor 20 has a configuration in which the substrate 3 of the sensor 10 is replaced with a solution holding portion 8.

[0085] The solution holding portion 8 has a cylindrical portion 8A whose axis is in the direction perpendicular to the plane of the drawing (Y direction), and a bottom portion 8B that closes the bottom of the cylindrical portion 8A, i.e., the end portion on the -Y side. The cylindrical portion 8A and the bottom portion 8B can be made of the same material as the substrate 3.

[0086] Electrode 1 is formed on an outer surface 8C of cylindrical portion 8A. Electrode 2 is formed on an outer surface 8D of cylindrical portion 8A. Microchannel 4 is formed as a hole provided in cylindrical portion 8A so as to be positioned at the center of ring electrode 1A and ring electrode 2A.

[0087] The other configurations of the sensor 20 are the same as those of the sensor 10, so redundant explanations will be omitted.

[0088] Next, measurements using the sensor 20 will be described. The solution holding portion 8 of the sensor 20 can hold a sample solution in a space surrounded by the cylindrical portion 8A and the bottom portion 8B. FIG. 20 is a diagram showing how to use the sensor 20. As shown in FIG. 20 , the sensor 20 is temporarily submerged in the sample solution 9 and then pulled up so that the opening of the solution holding portion 8 faces upward. This allows the sample solution 9 to be stored in the space surrounded by the cylindrical portion 8A and the bottom portion 8B so that the liquid level is above the microchannel 4. In this state, the sensor 20 is immersed in the sample solution 9 so that the liquid level outside the solution holding portion 8 is higher than the liquid level inside. A pressure of approximately 30 Pa is generated by immersing the sensor 20 in the sample solution 9 so that the liquid level outside the solution holding portion 8 is higher than the liquid level inside the solution holding portion 8. For example, if the hydraulic head difference H between the inside and outside of the solution holding portion 8 is 3 mm, a pressure of approximately 30 Pa is generated. Furthermore, since the liquid levels inside and outside the solution holding portion 8 are lower than the upper end of the solution holding portion 8, the portions of the lead-out wirings 1B and 2B exposed above the liquid surface are electrically insulated by the solution holding portion 8. This allows the measurement of the measurement object 5 while the measurement object 5 passes through the microchannel 4.

[0089] Next, an example of measurement using the sensor 20 will be described. Here, the measurement conditions and the measurement method are the same as those in the example of the first embodiment, except that the sensor 20 is used.

[0090] Example 9: Here, a culture solution of bacteria (Pediococcus pentosaceus, L4140) was used as the sample solution, and the number of bacteria was measured for two minutes every two hours while the sensor 20 was immersed. FIG. 21 is a graph showing the results of the bacterial count measurement. As a comparative example, FIG. 21 also shows the optical density of the bacteria measured every two hours. As shown in FIG. 21, the measurement results using the sensor 20 showed a certain bias in the number of detected bacteria compared to the optical density, but it was confirmed that the measurements generally followed a similar trend.

[0091] As described above, the sensor 20 allows measurement of an object to be measured more easily in long-term measurements or continuous measurements without forming droplets each time.

[0092] Note that the sensor 20 may also perform measurements by applying electrophoresis, as described in embodiment 2. When applying electrophoresis to the sensor 20, the measurement object can be driven by a driving voltage, and therefore the liquid levels inside and outside the solution holding portion 8 may be at the same height.

[0093] In the above-described embodiment, a sensor has been described in which ring electrodes 1A and 2A are arranged so as to overlap each other when viewed along the Z axis. In this case, the distance between ring electrodes 1A and 2A in the Z axis direction becomes short, and as a result, the capacitance between ring electrodes 1A and 2A may affect the high-frequency characteristics of particle detection. Therefore, in this embodiment, a sensor capable of improving the high-frequency characteristics of particle detection will be described.

[0094] A sensor according to this embodiment will now be described. Fig. 22 is a front view schematically illustrating the configuration of a sensor 80 according to embodiment 4. As shown in Fig. 22, the sensor 80 has a configuration in which the electrodes 1 and 2 of the sensor 10 are replaced with electrodes 81 and 82, respectively.

[0095] The electrode 81 has a ring electrode 81A and a lead wire 81B. The ring electrode 81A has an inner diameter of φ ＩＮ１ , outer diameter is φ ＯＵＴ１ The lead wiring 81B is led out in the −X direction from the outer edge of the ring electrode 81A, and then bent in the +Y direction to extend to the +Y side end of the substrate 3.

[0096] The electrode 82 includes a ring electrode 82A and a lead wire 82B. The ring electrode 82A is concentric with the ring electrode 81A and has an inner diameter of φ ＩＮ２ , outer diameter is φ ＯＵＴ２ In this configuration, the ring electrode 82A has an outer diameter φ ＯＵＴ２ is the inner diameter φ of the ring electrode 81A ＩＮ１The ring electrodes 81A and 82A are designed so that the distance between the ring electrode 81A and the ring electrode 82A is smaller than the distance between the ring electrode 81A and the ring electrode 82A. Therefore, when viewed from the direction along the Z axis, the ring electrode 82A is disposed so as to be contained within the ring electrode 81A. The lead-out wiring 82B is led out from the outer edge of the ring electrode 82A in the +X direction, then bent in the +Y direction, and extends to the +Y side end of the substrate 3.

[0097] Therefore, in this configuration, when viewed from the direction along the Z axis, only a portion of the −X side of the ring electrode 81A and a portion of the lead wiring 82B overlap.

[0098] In this configuration, when the sensor 80 is viewed from the direction along the Z axis, the electrodes 81 and 82 are arranged so that only a portion of them overlap, and the rest of the electrodes do not overlap with each other. Therefore, the shortest distance between the electrodes 81 and 82 can be made longer than in the sensors according to the first to third embodiments.

[0099] 23 is a cross-sectional view showing the distance between the electrodes of sensor 10 according to the first embodiment. Fig. 23 shows a cross section of sensor 10 in the YZ plane. In sensor 10, ring electrode 1A and ring electrode 2A overlap when viewed from the Z-axis direction. Therefore, the shortest distance between ring electrode 1A and ring electrode 2A is distance d1 in a direction parallel to the Z-axis direction.

[0100] FIG. 24 is a cross-sectional view showing the distance between electrodes of sensor 80 according to the fourth embodiment. FIG. 24 shows a cross section of sensor 80 in the Y-Z plane. In sensor 80, ring electrodes 81A and 82A are arranged so as not to overlap when viewed from the Z-axis direction. Therefore, the shortest distance between ring electrodes 81A and 82A is distance d2, which connects the inner edge of ring electrode 81A and the outer edge of ring electrode 82A in a direction inclined with respect to the Z-axis direction. Therefore, distance d2 is longer than distance d1, and therefore it can be understood that the capacitance between electrodes 81 and 82 of sensor 80 is smaller than the capacitance between electrodes 1 and 2 of sensor 10.

[0101] Therefore, according to this configuration, it is possible to improve the frequency characteristics by reducing the capacitance between the electrodes 81 and 82. This makes it possible to improve the accuracy of sample detection and sample identification.

[0102] The ring electrode is merely one example of a closed annular shape, and may be any of various closed annular shapes, such as not only a perfect circle but also an ellipse, an egg shape, or a polygon.

[0103] Furthermore, each of the electrodes 81 and 82 may be disposed on either end of the microchannel 4. That is, each of the electrodes 81 and 82 may be disposed on either of the two surfaces of the substrate 3. For example, when the microchannel 4 is funnel-shaped as shown in Fig. 17, the electrode 81 may be disposed on the larger diameter side of the microchannel 4, and the electrode 82 may be disposed on the smaller diameter side. Furthermore, the electrode 81 may be disposed on the smaller diameter side of the microchannel 4, and the electrode 82 may be disposed on the larger diameter side.

[0104] In the fourth embodiment, the sensor was described as being provided with an electrode having a closed ring shape. In contrast, in the present embodiment, a sensor will be described in which the shape of the electrode is changed to further reduce the capacitance between two electrodes provided on both sides of the substrate 3.

[0105] A sensor according to this embodiment will now be described. Fig. 25 is a front view schematically illustrating the configuration of a sensor 80 according to embodiment 5. As shown in Fig. 25, a sensor 90 has a configuration in which the electrodes 81 and 82 of the sensor 80 are replaced with electrodes 91 and 92, respectively.

[0106] The electrode 91 has a C-shaped electrode 91A and a lead wire 91B. The C-shaped electrode 91A has the same inner diameter φ as the ring electrode 81A. ＩＮ１ and external diameter φ ＯＵＴ１ The C-shaped electrode 91A is an electrode having the shape of the letter C, in other words, an open ring shape, with a portion of the +X side removed compared to the ring electrode 81A. The lead-out wiring 91B has the same configuration as the lead-out wiring 81B, and therefore a duplicated description will be omitted.

[0107] The electrode 92 has a ring electrode 92 A and a lead wire 92 B. The ring electrode 92 A and the lead wire 92 B have the same configuration as the ring electrode 82 A and the lead wire 82 B, respectively, and therefore a duplicated description will be omitted.

[0108] In this configuration, the +X side of the C-shaped electrode 91A is open so that it does not overlap with the ring electrode 92A when the sensor 90 is viewed along the Z axis. As a result, when the sensor 90 is viewed along the Z axis, the electrodes 91 and 92 are arranged so that they do not overlap with each other over the entire length. Therefore, the shortest distance between the electrodes 91 and 92 can be made longer than in the sensor 80 according to the fourth embodiment. As a result, the capacitance between the electrodes 91 and 92 can be further reduced, improving the frequency characteristics. This can further improve the accuracy of sample detection and sample identification.

[0109] The ring electrode is merely an example of an open annular shape, and may be any of various closed annular shapes, such as a perfect circle, an ellipse, an egg, a polygon, etc. The C-shaped electrode is merely an example of an open annular shape, and may be any of various open annular shapes, such as a perfect circle, an ellipse, an egg, a polygon, etc.

[0110] Other Embodiments The present disclosure has been described above with reference to the embodiments, but the present disclosure is not limited to the above-described embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0111] In the above embodiment, the electrodes are described as being made of silver, but this is merely an example. For example, various metals such as gold and platinum can be used, and it is more preferable to use electrochemically stable metals, such as noble metals. The electrodes may also be made of various conductors, such as organic conductive materials. Furthermore, the electrodes may be formed using nanoink in which a metal material is dispersed.

[0112] In the above embodiment, the substrate and the solution holding portion are described as being made of polyimide, but this is merely an example. For example, the substrate and the solution holding portion may be made of various dielectric materials, such as various resins, including fluororesins such as Teflon (registered trademark), polycarbonate, and engineering plastics such as PEEK (polyether ether ketone), rubber, and elastomer.

[0113] In the second embodiment, the droplet 6 is formed on the sensor 10 and measurement is performed, but this is merely an example. For example, the sensor 10 can be used to perform continuous measurement (in-situ measurement) in the same manner as the sensor 20 according to the third embodiment. In this case, for example, the sensor 10 can be immersed in the sample solution so that the lead wires 1B and 2B are exposed above the liquid surface of the sample solution, and the wires 51 and 52 can be connected to the exposed portions of the lead wires 1B and 2B, thereby performing continuous measurement (in-situ measurement).

[0114] Identification of the object to be measured is not limited to the example using the current value and phase of the AC signal described above. For example, the signal processing unit 40 may be configured to calculate a composite impedance and a phase from the measurement results of the measurement unit 30 and identify the object to be measured using the calculated composite impedance and phase. For example, the signal processing unit 40 may use the composite impedance and the phase to calculate parameters corresponding to the resistance component, zeta potential, and dielectric constant of the object to be measured 5, respectively, and identify the object to be measured 5 using the calculated parameters corresponding to the resistance component, zeta potential, and dielectric constant. In this case, for example, the object to be measured 5 may be identified by mapping the parameters corresponding to the resistance component, zeta potential, and dielectric constant of the object to be measured 5 on a three-dimensional coordinate system with the axes of the resistance component, zeta potential, and dielectric constant. Here, the parameter corresponding to the resistance component is a parameter corresponding to the size of the object to be measured 5. The parameter corresponding to the zeta potential is a parameter corresponding to the surface potential of the object to be measured 5. The parameter corresponding to the dielectric constant is a parameter corresponding to the structure of the object to be measured 5, such as a spherical shell structure or membrane capacitance, or a parameter corresponding to the material of the object to be measured 5.

[0115] Since the size, surface potential, and structure differ depending on the measurement object 5, the resistance component, zeta potential, and dielectric constant, which are parameters corresponding to these, are calculated, and the parameters corresponding to the resistance component, zeta potential, and dielectric constant of the measurement object 5 are mapped on a three-dimensional coordinate system, thereby making it possible to classify the measurement object 5. For example, by mapping the measurement results of multiple types of measurement objects 5 on a three-dimensional coordinate system and accumulating the data, it is possible to improve the accuracy in identifying the measurement object 5.

[0116] In the above embodiment, the electrodes 1 and 2 have been described as having the same shape when viewed along the longitudinal direction of the microchannel 4, i.e., when viewed along the Z direction, but this is merely an example. As long as it is possible to measure the AC characteristics when the measurement object passes through the microchannel 4, the electrodes 1 and 2 may have different shapes.

[0117] For example, the lead wire 1B of electrode 1 and the lead wire 2B of electrode 2 may be positioned at different positions when viewed along the longitudinal direction of the microchannel 4, i.e., when viewed along the Z direction. FIG. 26 is a diagram showing a first modified example of the arrangement of electrodes 1 and 2. FIG. 26 shows the arrangement when viewed from a direction in which electrode 1 is on the front side and electrode 2 is on the back side, with electrode 1 indicated by a solid line and electrode 2 indicated by a dashed line. In this example, the lead wire 1B of electrode 1 and the lead wire 2B of electrode 2 are positioned at positions shifted from each other in the X direction, which is the horizontal direction on the paper. By separating the lead wires 1B and 2B, leakage current between the lead wires 1B and 2B can be suppressed, thereby improving the measurement accuracy of AC characteristics.

[0118] FIG. 27 shows a second modified example of the arrangement of electrodes 1 and 2. The observation direction and display method of the electrodes in FIG. 27 are the same as those in FIG. 26. In this example, lead-out wire 1B is arranged to extend from ring electrode 1A toward the +Y side, and lead-out wire 2B is arranged to extend from ring electrode 2A toward the -Y side. In other words, lead-out wire 1B and lead-out wire 2B are arranged to extend in opposite directions, in other words, in directions rotated 180 degrees around the center of the ring electrode. In this case, by further separating lead-out wire 1B and lead-out wire 2B, leakage current between lead-out wire 1B and lead-out wire 2B can be further suppressed. Therefore, this configuration also improves the measurement accuracy of AC characteristics.

[0119] The arrangement of the lead-out wires shown in Figures 26 and 27 is merely an example, and other arrangements are possible as long as the lead-out wires 1B and 2B can be spaced apart. For example, the lead-out wires 1B and 2B can be spaced apart in a direction other than the horizontal direction of the paper. Furthermore, the lead-out wires 1B and 2B can be provided so as to extend radially in a direction rotated by an angle other than 180 degrees. Furthermore, one or both of the lead-out wires 1B and 2B can be curved wires or bent in any direction so that the lead-out wires 1B and 2B are spaced apart.

[0120] In the above embodiment, the two electrodes provided on the sensor are made of flat conductive material, but the electrodes are not limited to this. For example, the electrodes may be made of a conductive porous material other than a dense conductive material.

[0121] Furthermore, in the above-described embodiment, the sample is detected while an AC voltage is applied to the sensor, but the detection of the sample is not limited to this. It is also possible to detect the sample while a DC voltage is applied to the sensor according to the above-described embodiment.

[0122] In the above-described embodiment, the analyte is described as being dispersed in a sample solution, but this is merely an example. The analyte may be transported by other methods as long as it can pass through the flow path extending between the two electrodes. For example, the analyte may be dispersed in a gas and passed through the flow path by the gas flow.

[0123] The object to be measured may also be present in a vacuum or an atmosphere so dilute that it can be considered a vacuum. Even in this case, a driving DC voltage, an AC voltage, or a combination of these may be applied to the object to drive it and cause it to pass through the flow path. In this case, the sensor according to the above-described embodiment may be used, for example, in outer space. The sensor according to the above-described embodiment may be applied to measure minute objects to be measured in outer space, such as dust particles, or relatively large objects to be measured, such as rocks and space debris. The sensor according to the above-described embodiment may also be used in a vacuum chamber of various vacuum devices, such as a measuring device or a manufacturing device. This may allow the behavior of minute objects in the vacuum chamber to be measured.

[0124] In the above embodiment, the measurement unit is described as measuring the voltage using a lock-in amplifier, but this is merely an example. The measurement unit may have any configuration as long as it can measure the voltage between two electrodes.

[0125] In the above-described embodiments, the measurement target may be a biological particle, an inorganic particle, or an organic particle. The biological particle may include a virus, a mycoplasma, a bacterium, an exosome, a viroid, an obelisk, a biomolecule, a cell, or an extracellular vesicle.

[0126] In the above embodiment, a CNN model constructed by machine learning is used to classify the measurement objects, but this is merely an example. For example, any model, such as a model based on a network other than CNN, may be applied.

[0127] The present invention has been described above in accordance with the above-mentioned embodiment, but the present invention is not limited to the configuration of the above-mentioned embodiment, and naturally includes various modifications, alterations, and combinations that a person skilled in the art can make within the scope of the invention as defined in the claims of this application.

[0128] This application claims priority based on Japanese Patent Application No. 2023-185427, filed October 30, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0129] 1, 2, 81, 82, 91, 92 Electrodes 1A, 2A, 81A, 82A, 92A Ring electrodes 1B, 2B, 81B, 82B, 91B, 92B Lead wiring 3 Substrate 3A, 3B Surface 4 Microchannel 5, 5A, 5B Measurement object 6 Droplet 7 Solvent 8 Solution holding portion 8A Cylindrical portion 8B Bottom portion 8C, 8D Surface 9 Sample solution 10, 20, 80, 90 Sensor 30 Measurement portion 31, 32 Terminal 33 Signal source 34 Lock-in amplifier 40 Signal processing portion 51, 52, 61, 62 Wiring 70 Solution holding structure 71, 72 Solution holding member 91A C-shaped electrode 100 Measurement system IN1, IN2 Input terminal OUT1, OUT2 Output terminal

Claims

1. A sensor comprising: a dielectric member; a first electrode made of a conductive material formed on a first surface of the dielectric member; a second electrode made of a conductive material formed on a second surface of the dielectric member; and a flow path formed in the dielectric member through which a measurement object can pass in a first direction intersecting the first and second surfaces of the dielectric member and through which a measurement voltage can be applied in the first direction by the first electrode and the second electrode, wherein the measurement object is identified based on the electrical characteristics of the measurement object when the measurement voltage is applied and the measurement object passes through the flow path.

2. The sensor described in claim 1, wherein the first electrode is an electrode having an open or closed shaped portion surrounding an end of the flow path on the first surface, and the second electrode is an electrode having an open or closed shaped portion surrounding an end of the flow path on the second surface.

3. The sensor of claim 2, wherein the first electrode has a first annular shaped portion, open or closed, surrounding an end of the flow path at the first surface, and the second electrode has a second annular shaped portion, open or closed, surrounding an end of the flow path at the second surface.

4. The sensor described in claim 3, wherein the first electrode has a first lead-out wiring led out from the outer edge of the first annular shaped portion, the second electrode has a second lead-out wiring led out from the outer edge of the second annular shaped portion, and the first lead-out wiring and the second lead-out wiring are arranged so as not to overlap each other when viewed along a direction perpendicular to the first and second faces.

5. The sensor according to claim 3, wherein the first annular portion and the second annular portion are arranged so as not to overlap each other when viewed from a direction perpendicular to the first and second faces.

6. The sensor according to claim 5, wherein, when viewed from a direction perpendicular to the first and second faces, the distance from the flow path to the outer edge of the second annular portion is closer than the distance from the flow path to the inner edge of the first annular portion.

7. The sensor described in claim 6, wherein the first electrode has a first lead-out wiring led out from an outer edge of the first annular shaped portion, the second electrode has a second lead-out wiring led out from an outer edge of the second annular shaped portion, the first annular shaped portion is configured as an open ring, and the first annular shaped portion and the second lead-out wiring are arranged such that, when viewed in a direction perpendicular to the first and second faces, the second lead-out wiring passes through the open portion of the ring of the first annular shaped portion.

8. The sensor according to claim 1 or 2, wherein the measurement voltage is an AC voltage, and the electrical characteristic of the object to be measured is an AC characteristic.

9. The sensor according to claim 8, wherein the frequency of the AC voltage is 100 MHz or less.

10. The sensor according to claim 8, wherein the object to be measured is driven along the direction in which the flow path extends by further applying a DC voltage between the first electrode and the second electrode.

11. The sensor according to claim 8, wherein the object to be measured is driven along the longitudinal direction of the flow path by applying a DC voltage whose polarity is periodically inverted between the first electrode and the second electrode.

12. The sensor according to claim 8, wherein the object to be measured is driven along the longitudinal direction of the flow path by applying a driving AC voltage having a lower frequency than the measurement AC voltage between the first electrode and the second electrode.

13. The sensor according to claim 1 or 2, wherein the dielectric member is configured as a flat plate-like member.

14. The sensor according to claim 1 or 2, wherein the object to be measured is dispersed in a solvent of a sample solution.

15. The sensor described in claim 14, wherein each of the first and second electrodes has an electrode portion that is immersed in the sample solution so that the flow path is below the liquid surface of the sample solution, and a wiring portion that is connected to the electrode portion and is used for applying a voltage and measuring the electrical characteristics.

16. The sensor of claim 14, wherein the first electrode is configured to hold a droplet of the sample solution by surface tension on the end of the flow path surrounded by the first electrode, and the second electrode is configured to hold a droplet of the sample solution by surface tension on the end of the flow path surrounded by the second electrode.

17. The sensor of claim 14, wherein the dielectric member has a tubular member and a bottom portion closing one end of the tubular member, the first surface being an outer surface of the tubular member, and the second surface being an inner surface of the tubular member.

18. The sensor described in claim 17, wherein the first and second electrodes are immersed in the sample solution such that the flow path is below the surface of the sample solution and a portion of the first electrode and a portion of the second electrode are exposed above the surface of the sample solution, the surface of the sample solution outside the tubular member and the surface of the sample solution inside the tubular member are at the same height or different heights, and the application of voltage to the first and second electrodes and the measurement of the electrical characteristics are performed via the portions of the first and second electrodes exposed above the surface of the sample solution.

19. The sensor according to claim 1 or 2, wherein the object to be measured includes biological particles, inorganic particles and organic particles, and the biological particles include at least viruses, mycoplasma, bacteria, exosomes, viroids, obelisks, biomolecules, cells and extracellular vesicles.

20. The sensor according to claim 1 or 2, wherein the object to be measured is identified using a change in current value and a change in phase obtained by using the measured electrical characteristic, and the obtained change in current value and change in phase.

21. The sensor of claim 1 or 2, wherein the object to be measured is identified based on the output of a model constructed by supervised learning using previously measured electrical characteristics of the object to be measured for learning and information identifying the object to be measured for learning as teacher data, the measured electrical characteristics being input into the model.

22. A measurement system comprising: a sensor for measuring an object to be measured; a measurement unit for measuring electrical characteristics of the object to be measured by applying a measurement AC voltage to the sensor; and a processing unit for identifying the object to be measured based on the electrical characteristics measured by the measurement unit, wherein the sensor comprises: a dielectric member; a first electrode made of a conductive material formed on a first surface of the dielectric member; a second electrode made of a conductive material formed on a second surface of the dielectric member; and a flow path formed in the dielectric member through which the object to be measured dispersed in a solvent of a sample solution contacting the first and second surfaces of the dielectric member can pass, and through which the measurement voltage can be applied in a first direction intersecting the first and second surfaces by the first and second electrodes, wherein the object to be measured is identified based on the electrical characteristics of the object to be measured when the object to be measured passes through the flow path with the measurement voltage applied.

23. A measurement method comprising the steps of: applying a measurement voltage in a first direction intersecting the first and second surfaces to a flow path formed in a dielectric member, through which a measurement object dispersed in a solvent of a sample solution contacting the first and second surfaces of the dielectric member can pass, by a first electrode made of a conductive material formed on the first surface of the dielectric member and a second electrode made of a conductive material formed on the second surface of the dielectric member; and identifying the measurement object based on the electrical characteristics of the measurement object when the measurement object passes through the flow path with the measurement voltage applied.

Images