JP2007198804A - Viscosity measuring instrument using particle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a viscometer for measuring the viscosity of a liquid under measurement even if the amount of the liquid is small as compared with a conventional viscometer, and accurately measuring the viscosity of the liquid in such a narrow domain that it flows within a factor of MEMS including a μ-TAS. <P>SOLUTION: An electrode pair 2 is provided in a container 1 for holding a suspension made by diffusing a particle group with their particle diameters known in a liquid under measurement, the electrode pair 2 capable of generating electric field distribution regularly arranged in the container by impressing a voltage from a power supply 3. By controlling the voltage impression on the electrode pair 2, a diffraction grating is generated owing to density distribution of the particle group caused by migration force acting on the particles in the suspension in the container 1, and thereafter, the diffraction grating is vanished. Diffracted light obtained by applying light to the container 1 is detected to find a diffusion coefficient of the particle group from a temporal change of the diffracted light in the process of vanishment while the viscosity of the liquid is calculated from the diffusion coefficient and particle diameters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a viscosity measuring device based on a new principle of measuring the viscosity of various liquids using particles, and more particularly to a viscosity measuring device capable of accurately measuring the viscosity of a liquid in a fine flow path.

  Conventionally, as a viscometer for measuring the viscosity of various liquids, a capillary viscometer, a rotational viscometer, a vibration viscometer using ultrasonic waves, and the like are known.

  The capillary tube viscometer measures the viscous resistance when a liquid to be measured such as a melt passes through the thin tube, and the liquid to be measured contained in the cylinder is caused to flow through the thin tube by being pressed by a piston. The viscosity of the liquid to be measured is determined from the flow rate of the piston at the time, the load applied to the piston, and the like (see, for example, Patent Document 1).

  The rotational viscometer rotates with the rotor immersed in the liquid to be measured, detects the braking force acting on the rotor due to the viscosity of the liquid to be measured, and converts the detection result into viscosity (for example, Patent Document 2). reference).

Furthermore, a vibration type viscometer using ultrasonic waves immerses a vibrating body equipped with a vibrator and a vibration sensor in a liquid to be measured, and applies an alternating voltage to the vibrator to give vibration to the vibrating body. A method is known in which the phase difference between the vibrator and the vibration sensor is detected, and the viscosity of the liquid to be measured is obtained from the relationship between the liquid viscosity and the phase difference obtained in advance (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 9-329539 Japanese Patent Laid-Open No. 2002-340768 Japanese Patent Laid-Open No. 11-173967

  By the way, a micro-groove technology is used to form a network of minute grooves through which a liquid flows on a substrate such as glass, and various operations and detection such as biochemistry are integrated on a single chip. In systems and elements that use MEMS technology (including comprehensive analysis systems), for example, when a chemical reaction or biological reaction occurs in a fine flow channel with a width of about several tens of μm, the flow channel is too narrow. The reaction rate may be slower than the value. From this, it is suspected that the viscosity of the liquid may increase in the fine channel.

  However, conventional viscometers such as those described above cannot measure the viscosity of the liquid in the narrow region as described above, and there is no means to prove the above suspicion.

  Further, in the conventional viscometer, the liquid to be measured necessary for measuring the viscosity is generally required on the order of several tens of cc, and the viscosity cannot be measured when the amount of the liquid to be measured is small. There is also a problem.

  The present invention has been made in view of such circumstances, and can measure the viscosity even when the amount of the liquid to be measured is small as compared with the conventional viscometer, and includes μ-TAS. An object of the present invention is to provide a particle-based viscometer that can accurately measure the viscosity of a liquid in a narrow region that flows in a MEMS element.

  In order to solve the above problems, a viscometer using the particles of the present invention includes a container for holding a suspension obtained by diffusing particles having a known particle diameter in a liquid to be measured, direct current, frequency modulation, A power source that generates a voltage of a predetermined pattern including voltage modulation or a pattern that can be arbitrarily set, and an electrode that is provided in the container and generates an electric field distribution regularly arranged in the container by applying a voltage from the power source By controlling the application of voltage from the power source to the pair and the electrode pair, generation of a diffraction grating due to the density distribution of the particle group caused by the migration force acting on the particles in the suspension in the container, and Control means for controlling the extinction, a light source for irradiating light toward the generation site of the diffraction grating in the container, a photodetector for detecting the diffracted light of the light by the diffraction grating, and detection by the photodetector Of diffracted light intensity It is characterized by having an analysis / calculation means for obtaining the viscosity of the liquid to be measured from the result and the particle diameter of the particle group from the result and the particle diameter of the particle group, while obtaining information on the diffusion speed of the particle group from the interim change. (Claim 1).

  Here, in the present invention, the information relating to the diffusion speed of the particle group is a diffusion coefficient, and the analysis / calculation means uses the diffusion coefficient and the particle diameter of the particle group to calculate from the Einstein-Stokes equation. A configuration for calculating the viscosity of the liquid to be measured (Claim 2) can be suitably employed.

  The present invention states that particles in a liquid move by dielectrophoresis or electrophoresis, and that the ease of particle diffusion in a liquid depends on the viscosity and particle diameter of the liquid if the temperature is constant. By diffusing particles with a known particle size into the liquid to be measured and storing it in a container as a suspension, and applying a spatial periodic electric field distribution to the suspension through the electrode pair Generate a diffraction grating by particle groups, detect the intensity of the diffracted light obtained by irradiating the diffraction grating with light, and change the diffracted light over time when the electric field distribution is changed. Viscosity is obtained.

  In other words, the particles are stored in a container in the state of a suspension in which a group of particles having a known particle diameter is mixed and diffused with respect to the liquid to be measured, and a voltage is applied to the electrode pair provided in the container to bring it into the container. When a regularly arranged electric field distribution is generated, a migration force acts on the particles to generate a diffraction grating composed of particles. The diffraction grating formed of the particle group disappears by stopping the voltage application to the electrode pair or by frequency modulation or voltage modulation. When irradiating light toward the generation site of the diffraction grating by the particle group, detecting the light diffracted by the diffraction grating, and measuring the temporal change of the diffracted light intensity in the annihilation process of the diffraction grating, the temporal change is This is information on the diffusion of the particle group in the liquid to be measured. Since the particle diameter is known, the viscosity of the liquid to be measured can be calculated from the temperature at the time of measurement.

  Specifically, as in the invention according to claim 2, the particle diffusion coefficient in the liquid to be measured is obtained from the temporal change in the diffracted light intensity, and the viscosity of the liquid to be measured is calculated from the Einstein-Stokes equation. be able to.

  In the above configuration, the generation and extinction of the diffraction grating by the migration of the particle group in the liquid to be measured can be generated in a very narrow region, and by setting the thickness of the container to about several hundred μm or less, It is possible to measure the viscosity of the liquid to be measured in a region equivalent to the inside of the groove used in μ-TAS or the like. In addition, when measuring the viscosity of the liquid to be measured in the normal region other than the viscosity of the liquid to be measured in the fine region, the measurement to be performed for viscosity measurement is performed by setting the container thickness to, for example, about several mm. The amount of liquid can be reduced.

  As described above, according to the present invention, a group of particles having a known particle diameter is diffused in a liquid to be measured and stored in a container, and an electric field regularly arranged in the container is generated to generate the group of particles. From the temporal change of the diffracted light intensity in the annihilation process of the diffraction grating, the information related to the diffusion of the particles in the liquid to be measured is obtained from the information related to the diffusion and the particle diameter. Since the viscosity of the liquid to be measured is calculated, it is possible to measure the viscosity of the container in a narrow region equivalent to the flow path in the element in the MEMS such as μ-TAS. It is expected to be useful for elucidating the behavior of

  In addition to the viscosity in a narrow area, it is possible to measure the viscosity of the liquid to be measured using a small container of several mm or less when measuring normal viscosity. Compared with the viscometer based, the required amount of the liquid to be measured can be greatly reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an embodiment of the present invention, and is a diagram illustrating a schematic diagram showing an optical configuration and a block diagram showing an electrical configuration. 2 is a diagram showing both a schematic cross-sectional view of the container 1 in FIG. 1 and a circuit diagram for applying a voltage to the electrode pairs 21 and 22, and FIG. 3 shows the container 1 in FIG. It is a figure which shows the example of the pattern of the electrode pair provided.

  The apparatus includes a container 1 filled with a sample suspension L in which particles having a known particle diameter are dispersed in a liquid to be measured for viscosity, an electrode pair 2 provided in the container 1, A power source 3 for applying a voltage to the electrode pair 2, an irradiation optical system 4 for irradiating light to the container 1, and a diffraction due to a density distribution of particle groups generated in the container 1 by applying a voltage to the electrode pair 2. A detection optical system 5 that measures the diffracted light from the grating, a sample transport unit 6 that supplies the sample suspension L into the container 1, a temperature measurement unit 7 that measures the temperature inside the container 1, and the entire apparatus. The control / data collection / analysis unit 8 is mainly configured to control the data and process the data by taking in the outputs from the detection optical system 5 and the temperature measurement unit 7.

  As shown in FIG. 2, the container 1 has a rectangular parallelepiped shape as a whole including walls 11 and 12 made of a transparent material and parallel to each other, and the electrode pair 2 is formed on the inner surface of the wall 12. Is formed. In this example, the container 1 has an interval between the wall bodies 11 and 12 of several hundred μm or less, and the material of the container 1 including these wall bodies 11 and 12 is, for example, quartz glass, It can be easily manufactured by applying MEMS technology.

  As illustrated in FIG. 3, the electrode pair 2 includes substantially comb-shaped electrodes 21 and 22, and each of the electrodes 21 and 22 includes a plurality of linear electrode pieces 21 a, 21 a, and 22 a that are parallel to each other. .. 22a and connecting portions 21b and 22b connecting these electrode pieces 21a, 21a, 22a,. In each electrode 21, 22, each electrode piece 21 a, 21 a and 22 a, 22 a has two electrode pieces 21 a, 21 a or 22 a, 22 a adjacent to each other, and no electrode piece exists The electrode non-existing regions are alternately formed, and the two electrode pieces 21a, 21a or 22a, 22a of the electrode piece unevenly-distributing region of one electrode are in the electrode piece non-existing region of the other electrode; It has become. Thereby, as a whole, the electrode pieces 21a and 22a are alternately arranged in parallel with each other at a predetermined interval, and the electrode pieces 21a and 22a are arranged while being insulated from each other. The width of each electrode piece 21a, 22a is about 10 μm.

  A voltage from the electrode power source 3 is applied to the above electrode pair 2 under the connection as shown in FIG. 2, and an electric field distribution is generated in the suspension L accommodated in the container 1 by the application of this voltage. Due to the electric field distribution, the particle group in the sample suspension L migrates as described later, and a diffraction grating is generated by the density distribution of the particle group. The output voltage of the electrode power source 3, in other words, the voltage applied to the electrode pair 2 is controlled by the control / data collection / analysis unit 8 as described later.

The irradiation optical system 4 outputs substantially monochromatic light in a state of being formed into a substantially parallel light beam, and the output light is irradiated toward the formation surface of the electrode pair 2 of the container 1. As the light source of the irradiation optical system 4, a light source that emits only monochromatic light such as a laser or an LED can be preferably used. However, a continuous wavelength light source that is pseudo-monochromatic with a bandpass filter or a spectroscope is used. Also good.
The detection optical system 5 is arranged in the direction in which, for example, the first-order diffracted light diffracted by the diffraction grating based on the density distribution of the particle group in the container 1 to be described later out of the light from the irradiation optical system 4 is emitted. The detection optical system 5 includes, for example, an aperture 5a and a photodetector 5b. By this detection optical system 5, the change in the intensity of the diffracted light produced by the diffraction grating due to the density distribution of the particles in the container 1 is measured in time series.

  In the above configuration, the container 1 in a state in which particles having a known particle size, preferably monodispersed and uniform particle size, and about 10 to 100 nm as an example of the particle size are dispersed in the liquid to be measured. When an AC voltage is applied from the electrode power source 3 between the electrodes 21 and 22 constituting the electrode pair 2 in the state introduced into the electrode pair 2, the distribution of the electric field corresponding to the electrode pattern becomes the sample suspension L in the container 1. The high-density region P of the particle group is formed by dielectrophoresis based on the electric field distribution. In the electrode pattern shown in FIG. 2, a high density region P of particle groups is formed in a portion where the electrode piece 21 a of one electrode 21 and the electrode piece 22 a of the other electrode 22 are adjacent to each other. Accordingly, the high density region P of the particle group is formed in parallel with each other at a pitch twice the pitch of the electrode pieces 21a and 22a, and a diffraction grating is generated by the high density region P of the plurality of particle groups. Is done. In such a diffraction grating generation state, for example, by stopping the application of voltage to the electrode pair, the particle group starts to diffuse, and the spatial density of the particle group in the sample suspension L becomes uniform. The diffraction grating due to the density distribution of the group will eventually disappear.

By irradiating light from the irradiation optical system 4 to the diffraction grating due to the density distribution of the particle group, the light is diffracted by the diffraction grating, and the intensity of the diffracted light gradually becomes weaker in the process of extinction of the diffraction grating. Go. FIG. 4 is a graph showing an example of a voltage waveform applied to the electrode pair 2 and a temporal change in the intensity of diffracted light by the diffraction grating created by the density distribution of the particle group. In this example, a sine wave-like AC voltage having a constant voltage V ₀ is applied to the electrode pair 2, a dielectrophoresis is caused to act on the particles, a diffraction grating is generated, and the application of the voltage is stopped to stop the dielectrophoretic force. The example which stopped the effect | action of is shown.

The temporal change in the diffracted light intensity during the annihilation process of the diffraction grating due to the density distribution of the particle group depends on the ease of diffusion of the particles in the liquid to be measured. That is, the diffusion coefficient of the particle group can be obtained by measuring the change of the diffracted light intensity with respect to time t. For example, the temporal change I (t) of the first-order diffracted light has the following relationship with the diffusion coefficient D.
I (t) ∝exp [-2 · q ² · D · t] (1)
Where q is the pitch (grating period) of the diffraction grating due to the density distribution of the particles as Λ,
q = 2π / Λ (2)
It is.

On the other hand, the diffusion coefficient D of the particles in the liquid is known to satisfy the following Einstein-Stokes equation using the Boltzmann constant k, where η is the viscosity of the liquid, d is the particle diameter of the particles, and T is the absolute temperature. It has been.
D = kT / 3πηd (4)

  In the control / data collection / analysis unit 8, the diffusion coefficient D of the particles in the sample suspension is calculated from the temporal change I (t) of the first-order diffracted light based on the output of the detection optical system 5 using the equation (1). While calculating, the viscosity η of the liquid to be measured is calculated using the diffusion coefficient D, the temperature detection value T from the temperature measurement unit 7, and the known particle diameter d.

  Here, as described above, the interval between the walls 11 and 12 is as narrow as several hundreds μm or less, and the viscosity η obtained by the above calculation is a value representing the viscosity of the liquid to be measured in the narrow region. It becomes. Actually, when the interval between the wall bodies 11 and 12 of the container 1 is sufficiently wide, the diffusion coefficient takes a constant value even when the interval is changed, but the interval is as narrow as several hundred μm or less as described above. Then, the diffusion coefficient becomes small. This means that when the liquid is in a narrow area, the liquid has a value different from the viscosity in a wide area, and the behavior of the liquid in μ-TAS or the like can be confirmed.

  In the above embodiment, the container 1 is narrow, and the viscosity of the liquid to be measured in the narrow region is calculated. However, the viscometer of the present invention is not limited to the viscosity in such a narrow region. It is also possible to perform the same measurement as described above by sufficiently widening the interval between one wall body 11 and 12. In this case, for example, by setting the interval between the wall bodies 11 and 12 to about several millimeters, the required amount of the sample for measurement can be greatly reduced as compared with various existing viscometers. .

  In the above embodiment, an alternating voltage is applied to the electrode pair 2 to generate a dielectrophoretic force on the particles to generate a diffraction grating based on the density distribution of the particles, and then the application is stopped. The particles may be diffused by applying an AC voltage with a frequency at which dielectrophoretic force is likely to be generated to generate a diffraction grating, and then modulating the frequency to a frequency at which dielectrophoretic force is less likely to occur. It may be changed. The waveform of the AC voltage is arbitrary such as a sine wave or pulse. There may be a case where a positive force for moving the particles to the vicinity of the electrode pair 2 having a high electrolytic density due to dielectrophoresis and a case where a negative force for moving the particles away from the electrode may be applied. Further, a direct current voltage may be applied to the electrode pair 2 to collect the particles by applying an electrophoretic force to the particles.

  Moreover, in the above embodiment, as the electrode pair 2, the electrode pieces 21 a and 22 a of the electrodes 21 and 22 are alternately arranged two by two. Thus, the grating periods of the diffraction grating formed by the electrode pieces 21a and 22a and the diffraction grating due to the density distribution of the particle group are different, and the m + 1 order diffracted light from the diffraction grating due to the density distribution of the particle group is changed to the electrode pieces 21a and 22a. Therefore, only the diffracted light from the diffraction grating due to the density distribution of the particle group can be detected. However, the present invention is not limited to this, and it is also possible to adopt an electrode configuration in which the electrode pieces 21a and 22a are alternately arranged one by one. In this case, the diffracted light is emitted from the diffraction grating due to the density distribution of the particle group. Diffracted light and the diffracted light from the electrode pieces 21a and 22a are detected at the same time, but the temporal change of the diffracted light occurs only in the diffracted light due to the density distribution of the particle group. The same effects as those described above can be achieved. The width of the electrode pieces 21a and 22a is not limited to 10 μm, and may be about 1 μm to 10 μm. The pitch (grating period) Λ of the diffraction grating due to the density distribution of the particles may be about 1 μm to 100 μm.

  Furthermore, in the above embodiment, the sample liquid transporting part 6 for introducing the sample suspension L in which the particle group is dispersed in the liquid to be measured into the container 1 is provided. Needless to say, the sample suspension 1 can be filled with the sample suspension, and the container 1 can be positioned at a defined site in the apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of embodiment of this invention, and is the figure which writes together and shows the schematic diagram showing an optical structure, and the block diagram showing an electric structure. FIG. 2 is a diagram illustrating a schematic cross-sectional view of the container 1 in FIG. 1 and a circuit diagram for applying a voltage to electrode pairs 21 and 22. It is a figure which shows the example of the pattern of the electrode pair provided in the container 1 in FIG. It is a graph which shows the example of the time change of the diffracted light intensity by the voltage waveform applied with respect to the electrode pair 2 of embodiment of this invention, and the diffraction grating which the density distribution of a particle group produces.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Container 2 Electrode pair 21, 22 Electrode 21a, 22a Electrode piece 21b, 22b Connection part 3 Electrode power supply 4 Irradiation optical system 5 Detection optical system 6 Sample liquid transport part 7 Temperature measurement part 8 Control / data collection / analysis part P High density area

Claims (2)

  A container for holding a suspension obtained by diffusing particles having a known particle size in a liquid to be measured, and a power source for generating a voltage of a predetermined pattern including DC, frequency modulation, voltage modulation or a pattern that can be arbitrarily set And an electrode pair that is provided in the container and generates a distribution of electric fields regularly arranged in the container by applying a voltage from the power source, and by controlling the application of the voltage from the power source to the electrode pair, Generation of diffraction grating due to density distribution of particle groups caused by migration force acting on particles in suspension in container, control means for controlling disappearance thereof, and direction of generation of diffraction grating in container A light source for irradiating light, a photodetector for detecting diffracted light of the light by the diffraction grating, and a diffusion rate of the particle group from a temporal change in diffracted light intensity detected by the light detector. When you ask for information Moni, the result and from the particle diameter of the particle group, the viscosity measuring apparatus using the particles characterized in that it comprises an analysis and calculation means for calculating the viscosity of the test liquid.   The information related to the diffusion of the particle group is a diffusion coefficient, and the analysis / calculation means calculates the viscosity of the liquid to be measured from the Einstein-Stokes equation using the diffusion coefficient and the particle diameter of the particle group. A viscosity measuring device using the particles according to claim 1.

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