JP4830909B2 - Particle measuring device - Google Patents

Description

  The present invention relates to a particle measuring apparatus that optically measures information related to particles in a fluid, and more specifically, optically relates to information related to particles contained in a fluid from a density change accompanying particle aggregation / diffusion. TECHNICAL FIELD The present invention relates to a particle measuring apparatus for measuring automatically. The present invention can be applied to, for example, confirmation of the presence or absence of particles present in a fluid, measurement of diffusion coefficient, particle concentration, particle size (nanoparticles, microparticles), and the like.

  An electrode is provided so that an electric field is formed in a fluid containing particles, and an AC voltage is applied to the fluid to cause a dielectrophoretic phenomenon to move the particles in the fluid, thereby forming a density distribution of particle density. It is known that it can be done.

  As an optical measuring device applying such a dielectrophoresis phenomenon, dielectrophoresis was caused to particles in a liquid to form a particle concentration region, and then dielectrophoresis was stopped to diffuse particles from the particle concentration region. An apparatus for evaluating the diffusion of particles from a change in refractive index is proposed (see Patent Document 1). In this optical measuring apparatus, a local refractive index change is generated in the liquid by applying a voltage to the solution to be measured through two parallel electrodes to cause dielectrophoresis.

  In addition, as an optical measurement method improved from the above apparatus, an optical measurement method using a diffraction grating is proposed. That is, a diffracted light pattern different from the basic diffracted light pattern (modified diffracted light pattern) is generated by applying an alternating voltage to the diffraction grating electrode that generates the basic diffracted light pattern to cause dielectrophoresis of particles in the liquid. Has been proposed, and an optical measurement method (diffractive grating method using dielectrophoresis: hereinafter also referred to as a diffraction grating method) has been proposed (Patent Document). 2).

FIG. 5 is a cross-sectional view for explaining the operating principle of an optical measurement method (diffraction grating method) for measuring a change in refractive index when particles are moved using the dielectrophoresis phenomenon and the diffraction phenomenon.
A pair of two parallel linear electrodes 13a and 13b and a pair of two parallel linear electrodes 14a and 14b are alternately arranged on the glass substrate 12a constituting the wall surface of the cell holding the liquid sample. By arranging the electrodes, diffraction grating electrodes 13 and 14 having a periodic arrangement structure are formed. An AC voltage is applied from the AC power supply 15 to the diffraction grating electrodes 13 and 14. Dielectric migration between the electrodes 13a and 13b and between the electrodes 13a and 14b by applying an alternating voltage so that the electrodes 14a and 14b have opposite polarities, and by applying an alternating voltage. Causes the particles to aggregate. The regions P in which the particles are aggregated are formed at regular intervals with a period (2d) twice as long as the grating interval (d) of the diffraction grating electrodes 13 and 14.

The region P in which the particles are aggregated has a higher particle density and a different refractive index than the other regions, so that a diffraction grating having a grating interval 2d (hereinafter referred to as a density diffraction grating) is formed.
The shape of the diffraction grating electrode 13 and 14 for forming the density diffraction grating is not limited to this, and various variations are possible. For example, the diffraction grating includes a pair of electrodes and a floating portion to which no voltage is applied, and forms an array structure in which one electrode, the floating portion, and the other electrode are periodically arranged. A structure in which the diffraction grating serves as an electrode may be used. (See Embodiment 3 of Patent Document 2 above). Alternatively, the diffraction grating electrode may be formed of a transparent conductive film so that one electrode and the other electrode are alternately and periodically arranged. In this case, the diffraction grating does not appear when an AC voltage is not applied to the electrodes, and a density diffraction grating is formed when an AC voltage is applied.

  Then, in the state where the density diffraction grating is formed, when light is irradiated toward the diffraction grating cum electrodes 13 and 14 using the light source 16 and the lens optical system 17 that focuses the light source light, as shown in FIG. An original diffracted light pattern (basic diffracted light pattern: indicated by a solid line in the figure) generated by the diffraction grating electrodes 13 and 14 (period d) is generated, and derivative diffracted light generated due to the density diffraction grating (period 2d) Since a deformed diffracted light pattern generated by superimposing a pattern (shown by a broken line in the figure) is generated, a position where primary light, secondary light,. Therefore, the change in the refractive index can be detected from the change in the derived diffracted light intensity.

Then, when the voltage application is stopped again after the voltage application, the particles diffuse from the region P, and the derived diffracted light pattern disappears over time. By measuring the change, the refractive index change and the concentration change Further, the diffusion coefficient can be obtained from the concentration change based on the diffusion equation.
JP 2006-29781 A JP 2006-58196 A

By the way, when an unknown sample is measured by the diffraction grating method described above, the unknown sample is not necessarily non-conductive, and may exhibit conductivity.
When a voltage for dielectrophoresis (for example, 20 Vpp to 30 Vpp) for causing dielectrophoresis is applied between a pair of electrodes to a conductive sample, a current flows through the sample. At this time, if a voltage for dielectrophoresis measurement is applied to a highly conductive sample (a sample through which current easily flows), an excessive current flows when the applied voltage value is large, and as a result, the sample Generates heat and a convection phenomenon occurs, and in some cases, bubbles are generated in the sample. The occurrence of convection and bubbles affects the dielectrophoresis phenomenon and the diffracted light signal, and an accurate measurement result cannot be obtained.
In addition, an excessive current may cause a power failure or deteriorate the electrode. In addition, the sample to be measured may be altered.

  Therefore, the present invention provides a particle measuring apparatus capable of safely measuring particles (particle measurement by a diffraction grating method) without causing an excessive current to flow by mistake even when measuring an unknown sample. For the purpose.

  In order to solve the above problems, the particle measuring apparatus of the present invention includes a light source, a power source, a container for storing a fluid sample, a periodic electric field that is periodically arranged and a voltage is applied from the power source. An electrode pair for forming diffracted light and a photodetector for detecting diffracted light, and applying a voltage for dielectrophoresis to the electrode pair to change the particle density distribution in the fluid sample to generate a density diffraction grating, In a particle measuring apparatus that performs measurement related to particles by detecting derivative diffracted light generated by a density diffraction grating, a dielectrophoresis parameter setting unit that sets dielectrophoresis parameters including the dielectrophoresis voltage, and a current between the electrode pair Flow by controlling the current measurement unit to measure the current between the electrode pair by the current measurement unit while applying a voltage for conductivity evaluation weaker than the dielectrophoresis voltage to the electrode pair. A conductivity information acquisition control unit that acquires conductivity information of the sample, a determination data storage unit that stores a range of dielectrophoresis parameters capable of dielectrophoresis associated with the conductivity information as determination data, and Based on the conductivity information of the fluid sample and the determination data, a setting condition determination unit that determines the suitability of the set dielectrophoresis parameters, and a warning output unit that outputs warning information when an inappropriate determination is made. I have to prepare.

Here, the light source is preferably a laser light source, but any light source capable of obtaining derivative diffracted light from the fluid sample may be used.
As the power source, a power source capable of applying an AC voltage having a frequency at which particles contained in the sample can move by dielectrophoresis is used. The power source that applies the dielectrophoresis voltage and the power source that applies the conductivity evaluation voltage may be shared by changing the applied voltage using the same power source, but may be separate power sources.

  In the particle measuring apparatus according to the present invention, when a voltage for dielectrophoresis is applied to the electrode pair, derivative diffraction light is generated by forming a density diffraction grating. Therefore, by detecting the derivative diffraction light by a detector, Measure the particle size. Before performing this measurement, a voltage for evaluating conductivity that is weaker than the voltage for dielectrophoresis is applied to the electrode pair in advance, and the current value is measured by the current measuring unit. The measured current value is a physical quantity related to the conductivity of the fluid sample, and can be converted to the conductivity of the voltage fluid sample using the voltage for conductivity evaluation. Therefore, the measured current value or conductivity is acquired as the conductivity information.

  On the other hand, in the determination data storage unit, determination data in which a range of dielectrophoresis parameters capable of dielectrophoresis measurement and conductivity information (measured current value or conductivity at the time of applying a voltage for conductivity evaluation) are related, Pre-stored. This determination data is prepared in advance by preparing a large number of liquid samples (samples for preparing determination data) having different conductivities, and changing the setting conditions of the dielectrophoresis parameters for each liquid sample to generate heat and generate bubbles. The parameter range that can be set is obtained and stored. Therefore, when the conductivity (that is, the measured current value when the voltage for conductivity evaluation is applied) is given to the unknown sample to be measured, the data for determining the parameter range that can be set for the unknown sample is: You can select from a large number of stored data.

The setting condition determination unit refers to appropriate determination data with respect to the obtained conductivity information of the fluid sample, and determines whether the dielectrophoresis measurement voltage is applied with the set dielectrophoresis parameter.
As a result of the determination, when it is determined that applying the dielectrophoresis measurement voltage with the set dielectrophoresis parameters is inappropriate, the warning output unit outputs warning information.

  According to the present invention, even when measuring an unknown sample, it is possible to prevent an excessive current from flowing by mistake by measuring the conductivity of the fluid sample in advance. Measurements can be made.

(Means and effects for solving other problems)
In the above invention, the suitability determination of the dielectrophoresis parameter may be determined using at least one of frequency, application time, and waveform in addition to the conductivity information.
Since the heat generation of the liquid sample depends not only on the applied voltage but also on the frequency, application time, and waveform, appropriate determination can be made by making a determination including these.

In the above invention, the conductivity information acquisition control unit may be configured to be able to acquire conductivity information by setting instead of the conductivity information obtained by current measurement.
Thereby, when the conductivity information of the liquid sample is known in advance, the conductivity information can be easily set only by an input operation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and it goes without saying that various aspects are included without departing from the spirit of the present invention.

(Device configuration)
FIG. 1 is a block diagram showing a configuration of a particle measuring apparatus 1 according to an embodiment of the present invention. FIG. 2 is a plan view of the particle measuring apparatus 1 (excluding the control system 20). The particle measuring apparatus 1 includes a container 11 that holds a liquid sample (which may be a gel sample), a bottom wall 12a that is a bottom surface of the container 11, and a pair of electrodes 13 and 14 for forming a periodic electric field; A power source 15 for applying an alternating voltage to the electrode 13 and the electrode 14, a light source 16, a lens optical system 17 for converging light emitted from the light source, a photodetector 18 for detecting diffracted light, an ammeter 19, And a control system 20 for controlling the entire apparatus.

  The container 11 is formed by providing a frame body serving as the side wall 12b on the bottom wall 12a. The container 11 is made of a light-transmitting material such as glass so that incident light can be applied to the electrodes 13 and 14 through the bottom wall 12a.

The electrodes 13 and 14 are formed on the bottom wall 12a using a mask patterning technique. In the present embodiment, the electrodes 13 and 14 are formed on the bottom wall 12a. However, when the container 11 is sufficiently deep, the electrodes 13 and 14 are formed on the frame 12b serving as the side wall instead of the bottom wall 12a. May be formed. Alternatively, the electrodes 13 and 14 may be formed on another glass plate and placed on the bottom wall 12a.
By putting the liquid sample into the container 11 and immersing the electrodes 13 and 14 in the liquid, the electrodes 13 and 14 come into contact with the liquid sample.

  The electrode 13 is configured such that a linear electrode unevenly distributed region 13f in which two parallel linear electrodes 13a and 13b are adjacent and a linear electrode absent region 13c in which no linear electrode is formed are alternately repeated. All the linear electrodes 13a and 13b are electrically connected by a connecting portion 13d, and have a so-called comb-shaped electrode structure.

  The same applies to the electrode 14, and the linear electrode unevenly distributed region 14 f adjacent to the two parallel linear electrodes 14 a and 14 b and the linear electrode absent region 14 c where no linear electrode is formed are alternately repeated. In this manner, all the linear electrodes 14a and 14b are electrically connected by the connecting portion 14d to form a comb-type electrode structure.

Then, the linear electrodes 14a and 14b of the electrode 14 are arranged at the position of the linear electrode absence region 13c of the electrode 13, and the linear electrodes 13a and 13b of the electrode 13 and the linear electrode 14a of the electrode 14 are arranged. , 14b are continuously arranged at equal intervals so that electrodes having a periodic structure are formed by the linear electrodes 13a, 13b, 14a, 14b.
Furthermore, in this embodiment, the electrode itself is formed as a diffraction grating by forming the electrode with a metal film.

  The dimensions of the electrodes having the periodic structure are preferably about 0.5 μm to 20 μm for both the electrode width d1 and the electrode interval d2, but the shape and dimensions are not particularly limited. For example, the electrode width d1 and the electrode interval d2 may be different dimensions, or the shape does not have to be configured linearly. In the present embodiment, a linear electrode having an electrode width of 10 μm and an electrode interval of 10 μm is used. In this case, the grating interval d of the diffraction grating is d1 + d2.

  The AC power supply 15 uses a power supply that can adjust the applied voltage, frequency, application time, and waveform by an input operation. Specifically, for example, the applied voltage value is variable from 0 V to 100 V, the frequency is 10 kHz to 10 MHz, the applied time is continuous from 0.01 second, and the waveform is variable from a sine wave, a triangular wave, and a square wave. Is used.

The type of the light source 16 may be selected according to the liquid sample to be measured. For example, it is preferable to use a He—Ne laser light source (wavelength 633 nm) or another laser light source.
The lens optical system 17 is configured to converge the light source light and irradiate the electrodes 13 and 14 (diffraction grating). In this embodiment, the transmission diffracted light is measured, but the incident angle of the light source light (and the position of the detector 18) can be adjusted so that the transmitted diffracted light and the reflected light are reflected depending on the measurement object and the measurement purpose. Any of the diffracted light may be measured. When measuring transmitted diffracted light, the incident angle may be set so that total reflection does not occur at the interface with the liquid sample. For example, the incident angle may be incident vertically.

  The photodetector 18 is disposed on the upper side of the liquid sample when detecting transmitted diffraction light. When detecting the reflected diffracted light, it is arranged on the lower side of the liquid sample. The light detector 18 is provided with an angle adjusting mechanism for measuring the diffraction angle so that the diffraction angle can be detected together with the intensity of the diffracted light. A photodiode or CCD is used for the photodetector 18. Instead of providing the angle adjustment mechanism, the diffraction angle may be measured using an array sensor in which a plurality of elements are two-dimensionally arranged.

  Next, the control system 20 will be described. The control system 20 includes a computer system including a CPU 21, a memory (ROM, RAM, HDD) 22, an input device 23 (keyboard, mouse, etc.), a display device 24 (liquid crystal display, etc.), an input / output interface, and the like. In addition to control and calculation processing, various setting inputs and operation inputs, various data display, and warning display are performed.

  The CPU 21 performs control to execute various processes and functions. Of these, the processes and functions executed in connection with the present invention will be described in the form of blocks. The dielectrophoresis parameter setting unit 31, the conductivity information acquisition control unit 32, the setting condition determination unit 33, the warning output unit 34, and the measurement control unit. 35.

  The memory 22 includes a conductivity evaluation parameter storage area 41, a dielectrophoresis parameter storage area 42, and a determination information storage area 43 in addition to a work area necessary for the arithmetic processing by the CPU 21.

Data stored in the memory 22 will be described.
The conductivity evaluation parameter storage area 41 includes conductivity evaluation applied voltage, applied voltage frequency, application time, and waveform parameters as conductivity evaluation parameters necessary for measurement for evaluating the conductivity of the liquid sample. I remember it. The applied voltage for conductivity evaluation is set to a voltage value lower than the voltage for dielectrophoresis so that the liquid sample never generates heat or bubbles when a voltage is applied to the liquid sample. . For example, the voltage for dielectrophoresis is normally set at 10 to 40 Vpp, but the applied voltage for conductivity evaluation is set to about 1 to 10 Vpp.

  The dielectrophoresis parameter storage area 42 stores parameters relating to dielectrophoresis conditions when performing particle measurement by the diffraction grating method. This parameter is stored when the measurer performs an input operation when the dielectrophoresis parameter setting unit 31 described later prompts the measurer to input.

  The determination data storage area 43 stores determination data used when determining the suitability of the dielectrophoresis parameters. Specifically, the settable range of applied frequency and dielectrophoresis current corresponding to each conductivity (or the measured current value when the voltage for conductivity evaluation is applied) is the application time, voltage value for dielectrophoresis measurement. Further, although not shown, it is set for each applied waveform (sine wave, triangular wave, etc.). FIG. 3A to FIG. 3F are diagrams illustrating an example of stored determination data. Data defining such usable boundaries is stored for each conductivity.

Next, the CPU 21 will be described.
The dielectrophoresis parameter setting unit 31 performs control for setting dielectrophoresis parameters necessary for particle measurement by the diffraction grating method. Specifically, on the screen of the display device 24, control of the screen display that prompts the input of the dielectrophoresis voltage, dielectrophoresis frequency, application time of the dielectrophoresis voltage, and voltage waveform is performed, and the operator inputs these parameters. When the parameter input by the measurer is performed, control is performed to store these input values in the dielectrophoresis parameter storage area 42 of the memory 22 as set values.

  The conductivity information acquisition control unit 32 uses the conductivity evaluation parameters stored in advance in the conductivity evaluation parameter storage area 41 immediately before executing the particle measurement by the diffraction grating method. A voltage (conductivity evaluation voltage) is applied between them, and the ammeter 19 controls to measure the current value at that time. The measurement current value acquired in this way is acquired as the conductivity information of the liquid sample.

  The setting condition determination unit 33 includes determination data (see FIG. 3) stored in the determination data storage area 43, and conductivity information (measurement current value) of the fluid sample acquired by the conductivity information acquisition control unit 32. Based on the above, an operation is performed to determine whether or not measurement with the dielectrophoresis voltage included in the set dielectrophoresis parameter is possible.

  The warning output unit 34 outputs warning information when it is determined that it is inappropriate to apply the dielectrophoresis voltage with the set dielectrophoresis parameters as a result of the determination. As for the output warning information, a warning display is displayed on the screen by the display device 24, and a warning sound is emitted by a speaker (not shown).

  When the set dielectrophoresis parameters are appropriate, the measurement control unit 35 performs control to execute the original particle measurement by applying the dielectrophoresis voltage.

(Measurement operation)
Next, the measurement operation by the above apparatus will be described. FIG. 4 is a diagram showing an operation flow when the particle measuring apparatus 1 performs measurement by the diffraction grating method using dielectrophoresis.
The liquid sample to be measured is filled in the container 11 in advance. When the particle measuring device 1 is activated, first, an input screen for prompting parameter input is displayed on the display device 24 in order to set parameters for dielectrophoresis. The measurer uses the input device 23 to input dielectrophoresis parameters (dielectrophoresis voltage, frequency, application time, waveform). When these inputs are made, they are stored in the memory 22 (S101).

  Subsequently, in order to evaluate the conductivity of the liquid sample, the conductivity is evaluated using the conductivity evaluation parameters stored in the memory 22 in advance. That is, a voltage for conductivity evaluation is applied between the electrode pairs 13 and 14 and current measurement is performed by the ammeter 19 (S102). The applied voltage at this time is much weaker than the voltage for dielectrophoresis and has a voltage value that never generates heat or bubbles. Then, the measurement current value that is the measurement result is acquired as the conductivity information of the liquid sample, and is used for appropriateness determination described later.

  Subsequently, based on the conductivity information (measured current value) and the set dielectrophoresis parameter, the corresponding determination data is selected from the memory 22, and the suitability of the set dielectrophoresis parameter is determined (S103). . For example, when the determination data in FIG. 3 is selected and FIG. 3B is selected as the determination data when the migration voltage is 30 Vpp, the application time is 0.1 second, and the frequency is 500 KHz. Then, it is determined whether the electrophoretic current value is within the usable range in light of the selected determination data.

  When the determination result is within the usable range, the set dielectrophoresis parameters are actually set (S104). Thereby, particle measurement by the diffraction grating method is executed, and the measurement is finished (S106).

  On the other hand, when the determination result is out of the usable range, a warning display and a warning sound are generated on the display device 24 (S105), and the measurement is terminated. This prevents an excessive current from flowing (S106).

  In the operation flow, in S102, current measurement was actually performed by an ammeter, and the conductivity was evaluated. However, depending on the sample, the conductivity of the liquid sample may be known in advance, and in that case, it is possible to save the trouble of performing current measurement by directly inputting the parameter value of the conductivity. .

  The present invention can be used in a particle measuring apparatus using a diffraction grating method based on dielectrophoresis.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of the particle | grain measuring apparatus which is one Embodiment of this invention. The top view of the particle | grain measuring apparatus (except a control part) of FIG. The figure explaining an example of the data for determination which determines the suitability of a dielectrophoresis parameter. The figure which shows an example of an operation | movement flow. Sectional drawing explaining the principle of operation of the diffraction grating method. The figure explaining the diffracted light pattern by a particle | grain measuring apparatus.

Explanation of symbols

11: Container 12: Bottom walls 13, 14 Electrode 15: Power source 16: Light source 18: Light detector 19: Ammeter 20: Control system 21: CPU
22: Memory 31: Dielectrophoresis parameter setting unit 32: Conductivity information acquisition control unit 33: Setting condition suitability determination unit 34: Warning output unit 41: Conductivity evaluation parameter storage area 42: Dielectrophoresis parameter storage area 43: Determination Data storage area

Claims (3)

A light source, a power source, a container for storing a fluid sample, an electrode pair that is periodically arranged to apply a voltage from the power source to form a periodic electric field, and a photodetector that detects diffracted light Prepared,
Particles that measure particles by applying a voltage for dielectrophoresis to the electrode pair to generate a density diffraction grating by changing the particle density distribution in the fluid sample and detecting the derived diffracted light generated by the density diffraction grating In the measuring device,
A dielectrophoresis parameter setting unit for setting dielectrophoresis parameters including the dielectrophoresis voltage;
A current measuring unit for measuring a current between the electrode pair;
Conductivity for obtaining conductivity information of fluid sample by performing control to measure current between electrode pairs by current measurement unit while applying voltage for conductivity evaluation weaker than dielectrophoresis voltage to electrode pair An information acquisition control unit;
A determination data storage unit that stores a range of dielectrophoresis parameters capable of dielectrophoresis associated with conductivity information as determination data;
A setting condition determination unit that determines suitability of the set dielectrophoresis parameters based on the obtained conductivity information and determination data of the fluid sample,
A particle measuring apparatus comprising: a warning output unit that outputs warning information when an inappropriate determination is made. The particle measuring apparatus according to claim 1, wherein the suitability determination of the dielectrophoresis parameter is performed using at least one of frequency, application time, and waveform in addition to the conductivity information. The particle measuring apparatus according to claim 1, wherein the conductivity information acquisition control unit is configured to be able to acquire conductivity information by setting instead of conductivity information obtained by current measurement.