Measurement device, method for measurement, and measurement device

Abstract

To provide a device which can effectively quantify fine particles in a sample.SOLUTION: A measurement device for measuring the amount of fine particles in a sample includes: a dielectrophoretic device having an electrode for capturing fine particles by dielectrophoresis; a power source device for applying a voltage of a frequency which generates a negative dielectrophoretic force on fine particles, to the dielectrophoretic device; a light source device for radiating light to the dielectrophoretic device; and a light detector for detecting light which has passed through the dielectrophoretic device. The electrode has at least one collection point for fine particles, and presents a shape in which the area of the electrode becomes wider to the capturing point.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an apparatus, a method, and a device for measuring the amount of fine particles such as microplastics contained in a sample. [Background technology]

[0002] There are concerns about the impact of microplastics that have flowed into rivers and the ocean on ecosystems and human health. In particular, there is currently no established technology for monitoring the amount of microplastics with a diameter of 300 μm or less. Fine particles such as microplastics have the characteristic of being able to move by dielectrophoretic force.

[0003] For example, Patent Document 1 discloses an apparatus that uses dielectrophoretic force to adsorb minute substances such as radionuclides onto a filter and remove them. Patent Document 2 discloses an apparatus that uses dielectrophoretic force to concentrate microorganisms in a sample near an electrode and calculates the number of microorganisms by measuring the impedance caused by the concentration of the microorganisms. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-077978 A [Patent Document 2] Patent No. 3669182 Summary of the Invention [Problem to be solved by the invention]

[0005] The method disclosed in Patent Document 1 is an apparatus for adsorbing fine particles onto a filter, and does not mention quantitative evaluation of fine particles. Also, the method disclosed in Patent Document 2 calculates the number of microorganisms based on the measured impedance value, but does not mention quantification methods using other means.

[0006] An object of the present invention is to provide an apparatus capable of efficiently quantifying the amount of fine particles contained in a sample. [Means for solving the problem]

[0007] The measuring apparatus of the present invention is a measuring apparatus for measuring the amount of microparticles contained in a sample, and comprises a dielectrophoretic device having an electrode for collecting the microparticles by dielectrophoresis, a power supply unit for applying to the dielectrophoretic device a voltage of a frequency that generates a negative dielectrophoretic force on the microparticles, a light source unit for irradiating the dielectrophoretic device with light, and a photodetector for detecting the light that has passed through the dielectrophoretic device, wherein the electrode has one or more collection points for the microparticles, and the area of ​​the electrode gradually increases toward the collection point.

[0008] The measurement method of the present invention is a method for measuring the amount of microparticles contained in a sample, which comprises placing the sample in a dielectrophoretic device equipped with electrodes for collecting the microparticles by dielectrophoresis, applying to the dielectrophoretic device a voltage of a frequency that generates a negative dielectrophoretic force on the microparticles, thereby moving the microparticles to a predetermined position, irradiating the dielectrophoretic device with light, detecting the light that has passed through the dielectrophoretic device, and calculating the amount of the microparticles based on the transmittance of the light, and the electrodes are equipped with one or more collection points for the microparticles, and are shaped so that the area of ​​the electrodes gradually increases toward the collection points.

[0009] The measuring device of the present invention is a measuring device for measuring the amount of microparticles contained in a sample, and is provided with an electrode for capturing the microparticles by dielectrophoresis, the electrode having one or more collection points for the microparticles, and the electrode is shaped so that the area of ​​the electrode gradually increases toward the collection point. Effect of the Invention

[0010] According to the present invention, it is possible to provide an apparatus capable of efficiently quantifying the number of particles contained in a sample. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing an outline of the configuration of a measurement device 1 according to an embodiment of the invention. [Diagram 2] 1A to 1C are diagrams illustrating the mechanism of dielectrophoresis according to an embodiment of the present invention. [Diagram 3] 2A to 2C are diagrams showing examples of transparent electrodes provided on a glass substrate 17 of a dielectrophoretic device 11 according to an embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing another example of a transparent electrode provided on a glass substrate 17 according to an embodiment of the present invention. [Diagram 5] 3 is a diagram illustrating an example of an AC voltage applied to a dielectrophoretic device 11 according to an embodiment of the invention. [Figure 6] FIG. 13 is a diagram illustrating a calibration curve of transmittance and particle number according to an embodiment of the present invention. [Figure 7] FIG. 13 is a diagram illustrating a calibration curve of particle number and integrated fluorescent luminance according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Fig. 1 is a diagram showing an outline of the configuration of a measurement device 1 according to an embodiment of the present invention. As shown in Fig. 1, the measurement device 1 includes a dielectrophoretic device (measurement device) 11, a power supply device 12, a light source device 13, a photodetector 14, a lens 15, and a signal processing circuit (computing device) 16.

[0013] The measuring device 1 is a device that measures the amount of fine particles such as microplastics (hereinafter MP) contained in a sample such as seawater. Specifically, the MP in the sample is concentrated at a predetermined position by dielectrophoretic force, and a predetermined light beam is irradiated to measure the light transmittance. Furthermore, the number of particles in the sample is calculated from the measured transmittance using a calibration curve of the particle number and transmittance.

[0014] The dielectrophoretic device 11 is a device for collecting fine particles in a sample by dielectrophoresis. The dielectrophoretic device 11 includes a glass substrate 17 on which a sample is placed, and a stage 18 on which the glass substrate 17 is placed. A transparent electrode such as ITO (Indium Tin Oxide) is disposed on the glass substrate 17.

[0015] The power supply unit 12 is an AC power supply for applying a voltage to the transparent electrodes arranged on the glass substrate 17 .

[0016] The light source device 13 is a device for irradiating light onto the dielectrophoretic device 11 after the particles in the sample have been aggregated by dielectrophoresis. The light source device 13 is, for example, a laser diode.

[0017] The photodetector 14 is a device for detecting light that has passed through the dielectrophoretic device 11, out of the light irradiated from the light source device 13 to the dielectrophoretic device 11. The photodetector 14 is, for example, a photodiode.

[0018] The lens 15 is a lens for collecting the light emitted from the light source device 13 and irradiating the light onto the dielectrophoretic device 11 .

[0019] The signal processing circuit 16 calculates the light transmittance based on the intensity of the transmitted light detected by the photodetector 14. In addition, the number of particles contained in the sample is calculated using a calibration curve that calculates the number of particles from the transmittance.

[0020] Figure 2 is a diagram explaining the mechanism of dielectrophoresis. When a dielectric particle (e.g., MP) is placed in a non-uniform electric field formed by applying a voltage to a transparent electrode, a difference in force (Fdep) is generated by the induced dipole generated in the dielectric particle according to the difference in strength of the electric fields (Eleft, Eright) formed on the left and right of the particle, resulting in the movement of the induced particle. The dielectrophoretic force depends on the magnitude and frequency of the applied voltage, and the dielectric constants of the particle and medium. If the dielectric constant of the particle is larger than that of the medium, the particle moves toward the strong electric field side due to positive dielectrophoresis, and if the dielectric constant of the particle is smaller than that of the medium, the particle moves toward the weak electric field side due to negative dielectrophoresis.

[0021] In positive dielectrophoresis, the particles align in the direction of the electric field, forming pearl chains. This causes the particles to stick to the electrode, making it difficult to collect them in a specific location. On the other hand, in negative dielectrophoresis, a force acts to push the particles in the direction of the weaker electric field, causing the gathered particles to fly up from the electrode surface, making it difficult to confine them in a specific area. In addition, normal electrodes are not shaped in a way that is suitable for collecting particles by negative dielectrophoresis.

[0022] In this embodiment, the application frequency is controlled to generate a negative dielectrophoretic force, preventing the formation of pearl chains. The shape of the electrodes of the dielectrophoretic device 11 is made suitable for collecting fine particles by the negative dielectrophoretic force. In addition, since the fine particles are pushed out and fly up from the collection point in the negative dielectrophoresis, the flying up is suppressed by adding the positive dielectrophoresis.

[0023] 3 is a diagram showing an example of a transparent electrode provided on the glass substrate 17 of the dielectrophoretic device 11. FIG. 3 is a diagram showing the electrode as viewed from directly above (the direction of the light source device 13 in FIG. 1). As shown in FIG. 3, the electrode is provided with a collection point 51 for fine particles, and the area of ​​the electrode gradually increases toward the collection point 51. As the area of ​​the electrode increases, the electric field strength on the electrode weakens. In this way, by forming the electrode area gradually increasing toward the collection point 51, the fine particles are guided to the wide portion of the electrode (collection point 51) by a negative dielectrophoretic force.

[0024] 4(A) to (C) are diagrams showing other examples of transparent electrodes provided on glass substrate 17. In Figs. 4(A) to (C) as well, collection points 51 are provided, and the area of ​​the electrodes gradually increases toward each collection point 51.

[0025] FIG. 5 is a diagram illustrating an example of an AC voltage applied to the dielectrophoretic device 11. In this embodiment, a composite wave of frequencies that generate positive and negative dielectrophoresis is applied to suppress the flying up of the particles caused by negative dielectrophoresis, and trapping of the particles at the collection point 51 is achieved. In the example of FIG. 5, a composite wave of voltage / frequency 1 (10 Vpp / 1 kHz) that generates negative dielectrophoresis and voltage / frequency 2 (10 Vpp / 50 kHz) that generates positive dielectrophoresis is applied. The voltage / frequency that generates positive and negative dielectrophoresis can be determined according to the dielectric constants of the particles and the medium. In the example of FIG. 5, the particles are polystyrene beads with a diameter of Φ2 μm, and the number of particles is 1.1×10 8 The concentration is 1 / ml, the conductivity is 9μS / cm, and the flow rate is 0ml / sec.

[0026] The size of the fine particles suitable for collection by the dielectrophoretic device 11 according to this embodiment is a diameter of Φ1 μm to Φ100 μm. A frequency suitable for generating negative dielectrophoresis is 10 Hz to 10 kHz, and a frequency suitable for generating positive dielectrophoresis is 10 kHz to 10 MHz.

[0027] (Quantitative particle count) Next, a method for quantifying the number of particles collected using the dielectrophoretic device 11 will be described. In this embodiment, the number of particles in a sample is quantified using the transmitted light intensity. Specifically, the transmittance is calculated based on the intensity of light irradiated by the light source device 13 and the intensity of the transmitted light detected by the photodetector 14, and the number of particles is evaluated based on a calibration curve of the number of particles and the transmittance.

[0028] FIG. 6 is a diagram illustrating a calibration curve of transmittance and particle number. As shown in FIG. 6, the transmittance decreases as the number of particles increases. The calibration curve in FIG. 6 can be obtained using the calibration curve of particle number and fluorescent integrated brightness obtained using fluorescent particles. FIG. 7 is a diagram illustrating a calibration curve of particle number and fluorescent integrated brightness. For the calibration curve in FIG. 7, the number of particles is counted visually, and the integrated brightness is obtained by digitally processing the image data. It was confirmed from FIG. 7 that there is a proportional relationship between the number of particles and the integrated brightness. This allowed us to obtain a conversion formula from integrated brightness to the number of particles.

[0029] In the example of Fig. 6, in areas where the particle number is less than about 250, the calibration curve is obtained by visually counting the number of particles from images of actual particles. On the other hand, in areas where the particle number is more than about 250, the fluorescent integrated brightness is measured using fluorescent particles, and the particle number is calculated from the integrated brightness using the calibration curve in Fig. 7.

[0030] When obtaining a calibration curve, the fluorescence brightness is underestimated in areas where the particles overlap to form multiple layers, which can result in a large error between the calculated value and the experimental value. For this reason, by applying a composite wave that generates positive and negative dielectrophoresis using the dielectrophoretic device 11 according to this embodiment, the multi-layered particles become flat, making it possible to reduce the error.

[0031] As described above, according to this embodiment, by controlling the frequency applied to the dielectrophoretic device 11, it is possible to efficiently collect particles in a specific area while preventing the formation of pearl chains by the negative dielectrophoretic force due to the particles. In addition, by making the shape of the electrodes of the dielectrophoretic device 11 gradually wider toward the collection point, it is possible to make the shape suitable for collecting particles by negative dielectrophoresis. In addition, by applying a composite wave of frequencies that generate negative dielectrophoresis and positive dielectrophoresis, it is possible to suppress the particles from flying up from the collection point due to the negative dielectrophoretic force, and to more efficiently collect the particles.

[0032] In addition, the transmittance of light irradiated onto a sample in which fine particles have been collected is measured, and the amount of fine particles contained in the sample is calculated using a calibration curve showing the relationship between the number of particles and the transmittance. This makes it possible to easily measure the number of particles without using fluorescent particles, for example. [Explanation of symbols]

[0033] 1...measuring device, 11...dielectrophoretic device, 12...power supply device, 13...light source device, 14...photodetector, 15...lens, 16...signal processing circuit, 17...glass substrate, 18...stage, 51...collection point

Claims

1. A measuring device for measuring the amount of particles contained in a sample, comprising: a dielectrophoretic device including an electrode for collecting the fine particles by dielectrophoresis; a power supply unit that applies to the dielectrophoretic device a voltage having a frequency that generates a negative dielectrophoretic force on the microparticles; a light source device that irradiates the dielectrophoretic device with light; a photodetector that detects the light transmitted through the dielectrophoretic device; The electrode is The measuring device has one or more collection points for the fine particles, and the area of ​​the electrodes gradually increases toward the collection points.

2. The power supply device is The measuring device according to claim 1 , wherein a composite wave of a frequency that generates negative dielectrophoresis in the particles and a frequency that generates positive dielectrophoresis in the particles is applied.

3. The power supply device is 3. The measuring device according to claim 2, wherein a composite wave having a frequency of 10 Hz to 10 kHz for generating negative dielectrophoresis and a frequency of 10 kHz to 10 MHz for generating positive dielectrophoresis is applied.

4. 4. The measurement device according to claim 1, further comprising a calculation device that calculates an amount of fine particles contained in the sample from the transmittance of light transmitted through the dielectrophoretic device, using a calibration curve showing the relationship between the number of particles and the transmittance.

5. A method for measuring the amount of particles contained in a sample, comprising: The sample is placed in a dielectrophoresis device having electrodes for collecting the fine particles by dielectrophoresis; applying to the dielectrophoretic device a voltage having a frequency that generates a negative dielectrophoretic force on the microparticles, thereby moving the microparticles to a predetermined position; Irradiating the dielectrophoretic device with light; Detecting the light transmitted through the dielectrophoretic device; Calculating the amount of the fine particles based on the light transmittance; The electrode is The measurement method comprises one or more collection points for the fine particles, and the area of ​​the electrodes is gradually increased toward the collection points.

6. A measuring device for measuring the amount of particles contained in a sample, comprising: an electrode for collecting the fine particles by dielectrophoresis; the electrode comprises one or more collection points for the particulates; A measuring device, wherein the electrode is shaped so that the area of ​​the electrode gradually increases toward the collection point.

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