Measuring instrument for measuring flow characteristic of liquid, and method for measuring flow characteristic of liquid

Abstract

Provided are, inter alia, a measuring instrument with which it is possible to perform advanced pressure control on at least one end side of a capillary tube when measuring the flow characteristics of a liquid using the capillary tube.　This measuring instrument 100 for measuring the flow characteristics of a liquid comprises: a capillary tube 11 having a first opening 111 and a second opening 112; a first flow path 21 connected to the first opening 111 side; a pressure adjustment unit 3 connected to the first flow path 21; a switching valve 2 for switching the connection between the first flow path 21 and the pressure adjustment unit 3; and a measurement unit for measuring the fluidity of a liquid in the capillary 11. The pressure adjustment unit 3 has a fixed capacity container 31 and a variable capacity container 32 connected to the fixed capacity container 31, and adjusts pressure by changing the capacity of the variable capacity container 32.

Description

A measuring instrument for measuring flow characteristics of liquid, and a method for measuring flow characteristics of liquid

[0001] The present invention relates to a measuring instrument for measuring flow characteristics of liquid. The present invention also relates to a method for measuring flow characteristics of liquid.

[0002] In various experiments using biological samples, biosamples and the like, there are cases where precise measurement and comparison of viscosity of trace liquid samples, measurement of viscosity that fluctuates in a short time such as blood coagulation, and the like are required.

[0003] As a viscosity measuring apparatus for a small amount of sample, an EMS viscometer and the like have been put into practical use. The minimum sample volume of an EMS viscometer is about 300 μL, but since the friction between the metal ball and the bottom surface of the glass container cannot be ignored, it may not be suitable for biological samples with relatively low viscosity.

[0004] Patent Document 1 discloses a body fluid viscosity measuring apparatus for measuring viscosity of body fluid, comprising: a flow path through which the body fluid flows under the action of force caused by capillary phenomenon; and an arithmetic means that performs regression analysis based on a moving distance that the body fluid moves along the flow path and a moving time required for the movement of the moving distance, and derives the viscosity of the body fluid, wherein the arithmetic means performs regression analysis with the square of a value based on the moving distance as an explanatory variable and the moving time as a target variable.

[0005] Patent Document 2 discloses a viscosity measuring apparatus and the like, comprising: a main body having a capillary microchannel with a first opening and a second opening; a switching valve connected to the first opening side, the switching valve having a flow path connected to the main body and a flow path connected to a flow path open to the atmosphere; a sensor for detecting the position of liquid contained in the microchannel; a storage part that stores a test liquid in contact with the opening at the second end of the microchannel and is open to the atmosphere; a mounting table for mounting the main body; and a control part provided with a liquid absorption time measuring means for measuring a moving time during which the test liquid moves a predetermined position in the capillary microchannel, and an arithmetic means for deriving the viscosity of the test liquid.

[0006] Furthermore, Non-Patent Document 1 concerns a method for evaluating the viscosity and surface tension of low-volume samples using glass capillary tubes, and demonstrates that the viscosity of sucrose solutions of various concentrations can be measured using methods described in Patent Documents 1 and 2, etc., and that values ​​consistent with literature values ​​can be obtained.

[0007] Patent Document 3 discloses a system for measuring viscosity and surface tension, which uses a measuring instrument having a capillary tube having a first opening and a second opening, a flow path connected to the first opening side, a flow path open to the atmosphere and / or a flow path connected to a pressure adjustment unit, and a measuring unit for measuring the time tn to reach the liquid level position Ln in the capillary tube.

[0008] Patent Document 4 discloses a method for measuring the flow characteristics of a test liquid using a measuring instrument that includes a push-back means for pushing back the test liquid that has flowed into the capillary tube from the second opening side toward the first opening side, a control valve for adjusting the flow of liquid in the capillary tube, and a measuring unit for measuring the time tn to reach the liquid level position Ln in the capillary tube.

[0009] Japanese Patent Publication No. 7134430, Japanese Patent Publication No. 7371850, Japanese Patent Publication No. 7593601, International Publication No. 2023 / 182484

[0010] Kenji Sakamoto et al 2020 Jpn. J. Appl. Phys. 59 107002

[0011] The aforementioned patent and non-patent documents disclose techniques for measuring the viscosity of minute amounts of liquids. These techniques are suitable for measuring the viscosity of small amounts of bodily fluids such as blood collected by puncture from fingertips or saliva. The viscosity of blood and saliva has been pointed out as an indicator of the risk of developing diabetes and diseases such as periodontal disease, and there is a need for a method to test viscosity with minute amounts, so the use of the aforementioned patent and non-patent documents is expected.

[0012] In capillary tube measurements, it is preferable to fill the capillary tube with a liquid sample and apply positive and negative pressure, allowing it to move back and forth multiple times. By measuring the flow velocity of the sample, viscosity and other properties can be calculated. Multiple back-and-forth movements have the advantages of coating the inner surface of the capillary tube with the sample liquid itself at the start of measurement to achieve a stable flow, and increasing the number of flow velocity measurements to improve the reliability of the measurement values. This operation requires switching between positive and negative pressures alternately and rapidly.

[0013] Furthermore, adjusting the pressure to within ±100 Pa is sometimes crucial for measuring viscosity and other properties within a capillary tube. Additionally, applying higher pressure allows the sample liquid to be pushed out of the capillary tube and replaced with a fresh sample. The pressure required for this "pushing" may be around 1000 Pa.

[0014] Under these circumstances, the present invention aims to provide a measuring instrument, etc., that can perform advanced pressure control at at least one end of a capillary tube when measuring the flow characteristics of a liquid using a capillary tube.

[0015] The inventors of this invention have conducted extensive research to solve the above problems and have found that the following invention is suitable for the above purpose, leading to the present invention. That is, the present invention relates to the following invention.

[0016] <1> A measuring instrument for measuring the flow characteristics of a liquid, comprising: a capillary tube having a first opening and a second opening; a first flow path connected to the first opening; a pressure adjustment unit connected to the first flow path; a switching valve for switching the connection between the first flow path and the pressure adjustment unit; and a measuring unit for measuring the fluidity of the liquid in the capillary tube, wherein the pressure adjustment unit comprises a fixed-volume container and a variable-volume container connected to the fixed-volume container, and the pressure is adjusted by changing the volume of the variable-volume container. <2> The measuring instrument for measuring the flow characteristics of a liquid according to <1>, wherein the variable-volume container includes a bellows section, and the pressure in the pressure adjustment unit is adjusted by adjusting the expansion and contraction of the bellows section. <3> The measuring instrument for measuring the flow characteristics of a liquid according to <2>, comprising a solenoid attached to the bellows section for adjusting the expansion and contraction of the bellows section. <4> A measuring instrument for measuring the flow characteristics of a liquid according to any one of <1> to <3>, wherein the ratio (Va / V0) of the capacity of the variable capacity container to the capacity (V0) of the fixed capacity container is 1 / 1000 to 1 / 20. <5> A measuring instrument for measuring the flow characteristics of a liquid according to any one of <1> to <4>, wherein a plurality of the variable capacity containers are attached to the fixed capacity container. <6> A measuring instrument for measuring the flow characteristics of a liquid according to any one of <1> to <5>, wherein an expandable fixed capacity container is connected to the fixed capacity container, and a switching valve is provided to switch the connection between the fixed capacity container and the expandable fixed capacity container. <7> A measuring instrument for measuring the flow characteristics of a liquid according to any one of <1> to <6>, which measures the viscosity of a liquid. <8> A method for measuring the flow characteristics of a liquid, using a measuring instrument for measuring the flow characteristics of a liquid, the instrument comprising: a capillary tube having a first opening and a second opening; a first flow path connected to the first opening; a pressure adjustment unit connected to the first flow path; a switching valve for switching the connection between the first flow path and the pressure adjustment unit; and a measuring unit for measuring the fluidity of the liquid in the capillary tube, wherein the pressure adjustment unit comprises a fixed-volume container and a variable-volume container connected to the fixed-volume container, the method comprising the step of adjusting the pressure of the pressure adjustment unit by changing the volume of the variable-volume container.

[0017] According to the measuring instrument of the present invention, viscosity can be measured and the like by performing advanced pressure control at one end of the capillary tube.

[0018] This is a schematic diagram of a measuring instrument according to the first embodiment of the present invention. This is a schematic diagram of an embodiment of the pressure adjustment unit according to the present invention. The flow path connected to the capillary tube has been omitted. This is a schematic diagram of another embodiment of the pressure adjustment unit according to the present invention. The flow path connected to the capillary tube has been omitted. This is a schematic diagram of another embodiment of the pressure adjustment unit according to the present invention. The flow path connected to the capillary tube has been omitted. This is an image showing a partial example of the pressure adjustment unit according to the present invention. This is a graph showing an example of pressure adjustment performed by the pressure adjustment unit configured in Figure 2 above. The horizontal axis of the graph represents the change in the volume of the variable volume container, and the vertical axis of the graph represents the change in pressure.

[0019] The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is just one example (representative example) of an embodiment of the present invention, and the present invention is not limited to the following unless its gist is changed. In this specification, when the expression "~" is used, it is used to mean an expression that includes the numbers before and after it.

[0020] [Measuring Instrument of the Present Invention] The measuring instrument of the present invention comprises a capillary tube having a first opening and a second opening, a first flow path connected to the first opening, a pressure adjustment unit connected to the first flow path, a switching valve for switching the connection between the first flow path and the pressure adjustment unit, and a measuring unit for measuring the fluidity of the liquid in the capillary tube, wherein the pressure adjustment unit comprises a fixed-volume container and a variable-volume container connected to the fixed-volume container, and the pressure is adjusted by changing the volume of the variable-volume container, and is a measuring instrument for measuring the fluidity characteristics of a liquid.

[0021] [Method for Measurement of the Present Invention] The method for measurement of the present invention is a method for measuring the flow characteristics of a liquid using a measuring instrument for measuring the flow characteristics of a liquid, the instrument comprising: a capillary tube having a first opening and a second opening; a first flow path connected to the first opening; a pressure adjustment unit connected to the first flow path; a switching valve for switching the connection between the first flow path and the pressure adjustment unit; and a measuring unit for measuring the fluidity of the liquid in the capillary tube, wherein the pressure adjustment unit comprises a fixed-volume container and a variable-volume container connected to the fixed-volume container, and the method for measuring the flow characteristics of a liquid comprises a step of adjusting the pressure of the pressure adjustment unit by changing the volume of the variable-volume container.

[0022] Furthermore, the measurement method of the present invention can also be performed using the measuring instrument of the present invention, and the corresponding configurations in this application can be used interchangeably.

[0023] [Measuring Instrument] Figure 1 is a schematic diagram of a measuring instrument 100 according to a first embodiment of the present invention. The measuring instrument 100 includes a capillary tube 11, a pressure adjustment unit 3, and a measurement unit. The capillary tube 11 is connected to a flow path 21. The switching valve 2 is connected to the flow path 21, a flow path 22, and a flow path 23. The flow path 23 is connected to the pressure adjustment unit 3. The measuring instrument 100 can measure the flow characteristics of a liquid flowing through the microchannel 110 of the capillary tube 11. The measuring instrument 100 can measure, for example, the viscosity and surface tension of a liquid. The measuring instrument 100 may optionally include calculation units 81 to 83, a storage unit 80, and a display unit 91.

[0024] [Capillary Tube 11] The capillary tube 11 has a hollow, capillary-shaped microchannel 110, with a first opening 111 and a second opening 112 at both ends of the microchannel 110. The first opening 111 is connected to the channel of the switching valve 2 via a channel 21. The capillary tube 11 can be a commercially available capillary tube, for example, for spotting a sample in chromatography or for use as an electrode in electrophysiological experiments. The capillary tube includes those that exhibit capillary action, such as microchannels. Depending on the characteristics of the test solution and the purpose of measurement, hydrophilic or hydrophobic capillary tubes can be used.

[0025] The capillary tube 11 has a capillary-shaped microchannel 110, which is a channel of a diameter that allows capillary action to occur. Liquid enters the microchannel 110 due to the pressure within the microchannel space and the capillary force (surface tension) of the liquid. Factors such as the inner diameter of the microchannel, the surface tension of the liquid, the configuration of the switching valve, and the affinity between the microchannel and the liquid are involved. The inner diameter of a microchannel suitable for viscosity measurement using such capillary action is approximately 1 mm or less.

[0026] Furthermore, the present invention is suitable for evaluating trace amounts of liquids. It is particularly suitable for use with trace amounts of bodily fluids such as blood and saliva, which contain water as the main medium. For this reason, it is preferable to use a hydrophilic capillary tube 11 to facilitate capillary action. For example, the capillary tube 11 can be made of glass.

[0027] [Switching valve 2] Switching valve 2 is connected to the first opening 111 side via a flow path 21. Switching valve 2 also has a flow path 22 that is open to the atmosphere and a flow path 23 that is connected to the pressure adjustment unit 3. Since capillary action proceeds relatively quickly, it is preferable to use a solenoid valve for switching valve 2 that can instantaneously control the start and stop of liquid supply by an electrical signal.

[0028] [Pressure Adjustment Section 3] The pressure adjustment section 3 includes a fixed-volume container 31 and a variable-volume container 32. The pressure adjustment section 3 may also include a pressure gauge 30. The pressure adjustment section 3 is the part that is adjusted to a pressure other than atmospheric pressure.

[0029] The measuring instrument of the present invention can perform advanced pressure adjustment using the pressure adjustment unit 3. This pressure adjustment allows for adjustments of, for example, ±1000 Pa or ±100 Pa. This makes it possible to handle situations such as (A) when rapid pressure setting is required, (B) when stable and accurate pressure setting is required, and (C) when pressure setting is required that allows for sample replacement.

[0030] [Pressure Gauge 30] The first measurement method (system) of the present invention and the second measurement method (system) of the present invention require a clearly defined first specified pressure P1 and a second specified pressure P2. To determine these specified pressures, it is preferable that the pressure adjustment unit 3 uses a pressure gauge 30 to measure the pressure. Various pressure gauges that measure atmospheric pressure can be used. In particular, in the present invention, it is preferable to use a differential pressure gauge that can measure pressures in increments of 10 Pa, 1 Pa, or 0.5 Pa with a measurement range of approximately ±1,000 Pa, ±500 Pa, or ±300 Pa relative to atmospheric pressure.

[0031] [Fixed Volume Container 31] The pressure adjustment unit 3 has a fixed volume container 31. The fixed volume container 31 is a container that serves as the reference for pressure adjustment. It is preferable to use a fixed volume container 31 that is highly rigid and resistant to deformation. For example, the fixed volume container 31 can be made of a thick resin, glass, metal, or other material.

[0032] [Variable Volume Container 32] The pressure adjustment unit 3 has a variable volume container 32. The variable volume container 32 is connected to the fixed volume container 31. The variable volume container 32 can be made of a flexible and deformable material. It can also be made of a material that can maintain its deformed state. For example, a thin resin container can be used as a material that is easily deformable. Furthermore, by fixing the deformed state, the pressure resulting from changing the volume of the variable volume container 32 can be maintained.

[0033] The variable-volume container 32 can, for example, have its volume adjusted by attaching a pinchcock to a tube and opening and closing the pinchcock. Alternatively, by attaching a solenoid to a bellows-shaped container, the opening and closing of the bellows-shaped container can be adjusted by the movement of the solenoid.

[0034] The pressure in the pressure regulator 3 is adjusted from the capacity V0 of the fixed-capacity container 31 and the capacity of the variable-capacity container 32 as follows. First, the capacity V0 is constant. The variable-capacity container 32 has a capacity V before pressure setting. The fixed-capacity container 31 and the variable-capacity container 32 are at atmospheric pressure P0 when the vent control valve (omitted in Figure 1) is open. When setting the pressure, the vent control valve is closed to isolate the fixed-capacity container 31 and the variable-capacity container 32 from the atmosphere, and then the capacity of the variable-capacity container 32 is changed to V'. When the capacity change (V' - V) is positive (i.e., expansion), the pressure inside the container is negative (negative pressure: ΔP < 0) compared to atmospheric pressure. When the capacity change (V' - V) is negative (i.e., compression), the pressure inside the container is positive (positive pressure: ΔP > 0) compared to atmospheric pressure. The pressure change ΔP due to a change in the volume of a variable-volume container can be expressed by the following general formula, provided that the absolute value of the volume change (V' - V) is sufficiently smaller than the volume V0 of a fixed-volume container: ΔP = P0 × ((V - V') / V0)

[0035] To create positive pressure, the pressure adjustment unit 3 is opened to atmospheric pressure to increase the shape of the variable volume container 32 and increase its capacity V. After the pressure adjustment unit 3 is shut off from atmospheric pressure P0, the shape of the variable volume container 32 is reduced to decrease its capacity V' and the pressure in the pressure adjustment unit 3 is increased.

[0036] To create negative pressure, the pressure adjustment unit 3 is opened to atmospheric pressure, reducing the shape of the variable volume container 32 and decreasing its volume V. After the pressure adjustment unit 3 is shut off from atmospheric pressure P0, the shape of the variable volume container 32 is increased to increase its volume V' and the pressure in the pressure adjustment unit 3 is lowered.

[0037] The flow path 21 connected to the capillary tube 11 and the pressure adjustment unit 3 are connected so that the connection state can be switched by a switching valve 2. After setting the pressure adjustment unit 3 to an arbitrary pressure for measurement, connecting the capillary tube 11 to the flow path of the pressure adjustment unit 3 causes the liquid in the microchannel 110 of the capillary tube 11 to flow at the pressure of the pressure adjustment unit 3, allowing the fluidity at that time to be evaluated.

[0038] [Liquid reservoir section 4] The liquid to be measured is placed in the microchannel 110 of the capillary tube 11, and its fluidity is evaluated. In Figure 1, the liquid is contained in the microchannel 110 as a liquid column 51, with both ends of the sample liquid inside the capillary tube.

[0039] When storing the liquid as a liquid column 51, or when evaluating the fluidity during continuous storage using surface tension, etc., a device having a liquid reservoir 4, as shown in the measuring instrument 100 in Figure 1, can be used.

[0040] The liquid reservoir 4 contains the test liquid 5. Alternatively, the second opening 112 of the capillary tube 11 can be in contact with the test liquid 5 contained in the liquid reservoir 4. Note that in Figure 1, the measuring instrument 100 has been moved to a position where the second opening 112 is intentionally separated in order to evaluate the liquid column 51.

[0041] The volume of the test solution 5 contained in the liquid reservoir 4 can be appropriately set depending on the type of test solution and various conditions affecting viscosity and surface tension (such as the diameter of the microchannel), but it can be in the range of 500 μL or less, 300 μL or less, 100 μL or less, or 50 μL. While no lower limit is necessary for measuring fluidity, a lower limit such as 1 μL or more, or 10 μL or more, may be set.

[0042] [Test Solution 5] Test Solution 5 can be any liquid used as a sample to evaluate its flow characteristics. This liquid may contain various components dissolved or dispersed in it. Samples of biological origin such as blood or saliva can also be used. Emulsions, polymer solutions, and particulate turbidiform solutions can also be used.

[0043] [Mounting platform 7] The capillary tube 11, liquid reservoir 4, and sensors 6 (sensors 61-66) are arranged and integrated on the mounting platform 7. The mounting platform 7 is also structured so that the inclination of the microchannel of the capillary tube 11 can be set to approximately horizontal or to an inclination according to the purpose. Furthermore, the platform is configured so that the second opening 112 of the capillary tube 11 can come into contact with the test liquid 5 when the test liquid 5 is contained in the liquid reservoir 4.

[0044] [Sensor 6 (sensors 61 to 66)] Sensor 6 (sensors 61 to 66) is a sensor that detects the liquid level of the test liquid 5 flowing through the capillary 11. A plurality of sensors 61 to 66 are arranged in parallel in the microchannel 110 of the capillary 11 at predetermined intervals. Each of sensors 61 to 66 can detect a fluctuation in the microchannel 110 at the corresponding position.

[0045] For example, each of sensors 61 to 66 can be an optical sensor configured to detect fluctuations of the liquid level in the microchannel 110. When the liquid 51 is sucked into the microchannel 110, the liquid level becomes easily noticeably observable by optical means due to the difference in refractive index and / or the difference in light scattering between the liquid and the gas in the space. Each of sensors 61 to 66 can detect whether the liquid levels L1 to L6 pass therethrough.

[0046] [Timing unit 60] The timing unit 60 measures the time (arrival time) at which the liquid level reaches each of sensors 61 to 66. The timing unit 60 is also connected to the switching valve 2, and starts timing the detection time by sensors 61 to 66 triggered by the switching of the switching valve 2.

[0047] In this way, sensors 61 to 66 and the timing unit 60 constitute a measurement unit that measures the arrival time tn (t1 to t6) taken for the liquid level of the test liquid 5 to reach the liquid level positions Ln (Ln1 to L6) of the capillary 11.

[0048] It is preferable that the measuring instrument of the present invention has a stop sensor for detecting the liquid level position of the capillary 11, and when the stop sensor detects the liquid level, it transmits a signal to stop the switching valve 2 and closes the switching valve 2 to stop it, thereby stopping the flow of the liquid in the capillary 11.

[0049] The stop sensor may be installed for stopping purposes near the first opening 111 and just before the second opening 112 of the capillary tube 11. Alternatively, detection by sensors installed for timing, such as sensor 65 and sensor 66, may be used in conjunction with the stop sensor. The capillary tube 11 is disposable and can be replaced as needed, but if liquid enters the flow path 21, the measuring instrument 100 may become contaminated, and recovery work may become complicated.

[0050] In addition to using a signal to stop flow when a stop sensor detects the liquid level, a stop signal may also be issued to stop flow after a certain period of time has elapsed since the start of flow. The certain period of time before stopping can be set appropriately depending on the length, flow rate, etc. For example, it can be set to 3 to 10 seconds or 5 to 8 seconds.

[0051] As disclosed in Patent Documents 1 to 4, the movement of liquid within a capillary depends on the inner diameter of the capillary, as well as the viscosity and surface tension of the liquid. Furthermore, when the capillary is inclined relative to the horizontal, the movement of the liquid depends on the kinematic viscosity (the ratio of viscosity to density). Therefore, by understanding the movement of the liquid column within the capillary, it is possible to determine the viscosity, kinematic viscosity, surface tension, and other properties.

[0052] For example, as shown in Figure 1, when the entire sample liquid is contained within a horizontally positioned capillary tube, and both ends of the sample liquid column are inside the capillary tube, applying a constant pressure will cause the liquid column to move at a constant velocity within the capillary tube. The velocity of the motion is inversely proportional to the viscosity of the liquid. In other words, the velocity v of the liquid column within the capillary tube has the following relationship with viscosity η: v ∝ 1 / η

[0053] As an example, let's estimate the magnitude of the migration velocity v when the sample is pure water (viscosity: 0.001 Pa·s). When the inner diameter of the capillary tube is 0.68 mm and the sample volume is 5 μL, the sample contained in the capillary tube will form a liquid column approximately 13.6 mm long. If the pressure difference at both ends of the capillary tube is 1 / 1000 of an atmosphere (100 Pa), the velocity v of the liquid column will be approximately 10 cm / s. The velocity v of the liquid column is proportional to the pressure difference at both ends of the liquid column.

[0054] To determine the viscosity of a liquid sample, it is desirable to measure it by moving the sample back and forth multiple times within a capillary tube. To move the sample back and forth, it is necessary to rapidly switch between positive and negative pressure. Furthermore, accurate and reproducible pressure settings are required to accurately determine viscosity. By pushing the first sample, after measurement is complete, out of the capillary tube and exchanging it for a second sample, and comparing the movement speed under the same capillary tube and pressure, an accurate comparison of the viscosities of the two samples can be made. If a sample with a precisely known viscosity (e.g., pure water) is used as the second sample, the viscosity of the first sample can be accurately determined. The pressure required to "push" the sample is approximately 1000 Pa. The pressure required to measure viscosity by reciprocating the sample liquid column contained within the capillary tube is approximately ±100 Pa.

[0055] [Calculation Units 81-83] Calculation units 81-83 are parts for calculating the desired flow characteristics, as appropriate based on known patent documents 1-4, etc., depending on the state of the capillary tube and the liquid. Calculation units 81-83 may be used individually, or multiple units may be combined to evaluate the desired flow characteristics. The measuring instrument 100 can be realized by applying a program to a personal computer, tablet terminal, smartphone, etc., to enable the calculation units 81-83 to function.

[0056] [Storage Unit 80] The storage unit 80 is a part that stores the measured values ​​obtained when performing the measurement of the present invention, the calculation formulas for calculating each processing data, and the program for performing that processing.

[0057] [Display Unit 91] The display unit 91 is a monitor that displays various conditions such as measured viscosity and surface tension, pressure control status, and regression equations for calculation.

[0058] The pressure adjustment section of the measuring instrument of the present invention will be described in more detail below.

[0059] [Bellows section] A variable-volume container preferably includes a bellows section, and the pressure in the pressure adjustment section is adjusted by adjusting the expansion and contraction of the bellows section.

[0060] [Solenoid] Preferably, the variable displacement container has a solenoid attached to the bellows section to adjust the expansion and contraction of the bellows section. A solenoid is a functional component that uses electromagnetic force to convert electrical energy into mechanical motion. This operation can be applied to create pull solenoids, or push solenoids that use push bars to create a pushing action. When used in the present invention, a suitable solenoid mechanism is adopted depending on the purpose, such as whether the bellows section of the variable displacement container is for positive pressure or negative pressure, and how much pressure change is to be made. Since the solenoid can be electrically changed to a push-pull setting, it can be used in combination with the bellows section to stably, easily, quickly, and accurately adjust the amount of change in the volume of the variable displacement container.

[0061] [Capacity] In the measuring instrument of the present invention, the ratio (Va / V0) of the capacity of the variable capacity container to the capacity (V0) of the fixed capacity container is preferably 1 / 10000 to 1 / 20. The lower limit of the ratio (Va / V0) can more preferably be 1 / 5000 to, 1 / 2000 to, 1 / 1000, etc. The upper limit of the ratio (Va / V0) can be ~1 / 50 to, ~1 / 100 to, ~1 / 200, etc. By making the capacity of the variable capacity container appropriately smaller than the capacity of the fixed capacity container, it is possible to contribute to fine pressure adjustment.

[0062] The measuring instrument of the present invention can consist of a fixed-volume container to which multiple variable-volume containers are attached. Figure 2 is a schematic diagram of an embodiment of the pressure adjustment unit according to the present invention. A syringe-type variable-volume container (1) or a variable-volume container with a bellows section (2) can be connected to the fixed-volume container. The pressure in these fixed-volume containers can be measured by a pressure sensor. When adjusting these pressures, the vent control valve connected to the atmosphere can be appropriately controlled to open or shut off the pressure regulator 3 from the atmosphere. After adjusting the pressure, a switching valve (2 in Figure 1) connected to a capillary tube to start flow can be appropriately controlled.

[0063] Figure 3 is a schematic diagram of another embodiment of the pressure adjustment unit according to the present invention. This pressure adjustment unit has a variable-capacity container with three bellows sections with capacities of 1 mL, 2 mL, and 5 mL attached to a fixed-capacity container. This combination allows for precise pressure control in multiple stages.

[0064] The measuring instrument of the present invention may have an expandable fixed-capacity container connected to a fixed-capacity container, and a switching valve for switching the connection between the fixed-capacity container and the expandable fixed-capacity container. Figure 4 is a schematic diagram of another embodiment of the pressure adjustment unit according to the present invention. For example, by connecting a fixed-capacity unit (2) of 900 mL to a fixed-capacity unit (1) of 100 mL, the total capacity of the fixed-capacity unit can be changed, and therefore the amount of pressure change by the variable-capacity unit can also be changed.

[0065] Figure 5 shows an example of a part of the pressure adjustment unit according to the present invention. This image shows a variable displacement container with a solenoid attached to the bellows section. In this case, a push-type solenoid is attached. As shown on the left side of Figure 5, when the solenoid power is OFF and in standby mode, the bellows section is expanded. Then, as shown on the right side of Figure 5, when the solenoid power is ON and in air discharge mode, the bellows section is compressed.

[0066] Figure 6 is a graph showing an example of pressure adjustment performed by the pressure adjustment unit according to the present invention. A glass container was used as the fixed-volume unit. A digital pipette with a full scale of 10 mL was connected to it as a variable-volume container (1) (Figure 2). In addition, a container with a bellows section made of silicone rubber was attached as a variable-volume container (2). A push-type solenoid was attached to control the compression of the bellows. A pressure sensor was attached to the fixed-volume container to measure the pressure displacement. By providing a vent with a valve as shown in Figure 2, the pressure adjustment unit can be instantly isolated from the atmosphere, and the pressure can be returned to atmospheric pressure in a short time.

[0067] The plots on the graph were created by reading the pressure displacement when the pipette volume was immediately reduced by 0 mL, 2.0 mL, 4.0 mL, 5.0 mL, and 6.0 mL, respectively, after closing the vent and isolating the container from the atmosphere. This confirmed that pressure control using a variable volume container could be performed in steps multiple times, demonstrating excellent controllability. As is clear from this graph, it was confirmed that the pressure could be accurately adjusted by several hundred Pascals with good reproducibility relative to the international standard value of atmospheric pressure, 101325 Pascals (1013 hectopascals).

[0068] On the other hand, when the bellows were compressed by passing current through the solenoid (Figure 5, right) to reduce their volume, the pressure displacement was 1180 Pa. Reading from the graph, the change in bellows volume was calculated to be 5.0 mL. It was confirmed that by combining a solenoid and bellows, a predetermined pressure can be quickly created with simple operation involving only switching the current on and off. Furthermore, as shown in Figures 3 and 4, multiple bellows and multiple fixed-volume containers can be combined. With such a configuration, a wide range of pressures can be easily and quickly achieved with control using only a few bits of digital signals.

[0069] As an example, consider the case where three bellows of different capacities are used as a variable-capacity container, as shown in Figure 3 (see Table 1). Each bellows is independently paired with a solenoid. When signal 1 is sent to the solenoid control circuit, current flows through the solenoid, compressing the bellows. When signal 0 is sent to the solenoid control circuit, the current is cut off, and the bellows expand back to their initial state. The sizes of the compressed (and expanded) capacities are as shown in Figure 3: #1: 1.0 mL, #2: 2.0 mL, and #3: 5.0 mL. The signal [0,0,0] in Table 1 corresponds to a state where no current flows through any of the solenoids, and all three bellows are in the expanded state. The signal [1,0,0] corresponds to a state where only bellows #1 is compressed. At this time, the capacity change of the variable-capacity container is -1.0 mL. Using this state as the starting point for capacity reference, when signal [0,0,0] is sent, the bellows return to the expanded state. The capacity change at this time is +1.0 mL. Next, when the signal [1,1,0] is sent, bellows #1 and #2 are compressed. The volume change at this time is -3.0 mL. Similarly, when the signal [1,1,1] is sent, all three bellows are compressed. The volume change at this time is -8.0 mL. Using this state as the starting point for volume measurement, when the signal [0,0,0] is sent, the bellows expand and return to their initial state. The volume change at this time is +8.0 mL.

[0070]

[0071] In addition to solenoid control, another signal is provided to control the opening and closing of the vent control valve (Figure 3), and by linking the opening and closing of the vent control valve with the compression / expansion of the bellows, positive or negative pressure can be freely created. For example, if the vent is open and the bellows are compressed, an amount of air corresponding to the compression volume is pushed out of the container. If the vent is closed in this state and the signal [0,0,0] is sent to the solenoid, the bellows expand and the inside of the container becomes negative pressure. If the vent valve is opened while the signal [0,0,0] is still sent to the solenoid, air flows in through the vent and the inside of the container quickly returns to atmospheric pressure. If the vent valve is closed at the moment the pressure returns to atmospheric pressure, and then the bellows are compressed, the inside of the container becomes positive pressure corresponding to the compression volume. In other words, by manipulating a few bits of digital signal, pressure changes such as from atmospheric pressure to positive pressure, positive pressure to atmospheric pressure, negative pressure to positive pressure, and positive pressure to negative pressure can be achieved quickly.

[0072] This invention can be used for measuring the viscosity of liquids and is industrially useful.

[0073] 100 Measuring instrument 11 Capillary tube 110 Microchannel 111 First connection 112 Second connection 2 Switching valve 21-23 Flow path 3 Pressure adjustment unit 30 Pressure gauge 31 Fixed volume container 32 Variable volume container 4 Liquid reservoir 5 Test liquid 51 Liquid column 6, 61-66 Sensor 60 Timing unit 7 Mounting platform 80 Memory unit 81-83 Calculation unit 91 Display unit

Claims

1. A measuring instrument for measuring the flow characteristics of a liquid, comprising: a capillary tube having a first opening and a second opening; a first flow path connected to the first opening; a pressure adjustment unit connected to the first flow path; a switching valve for switching the connection between the first flow path and the pressure adjustment unit; and a measuring unit for measuring the fluidity of the liquid in the capillary tube, wherein the pressure adjustment unit comprises a fixed-volume container and a variable-volume container connected to the fixed-volume container, and the pressure is adjusted by changing the volume of the variable-volume container.

2. The measuring instrument for measuring the flow characteristics of a liquid according to claim 1, wherein the variable volume container includes a bellows section, and the pressure in the pressure adjustment section is adjusted by adjusting the expansion and contraction of the bellows section.

3. A measuring instrument for measuring the flow characteristics of a liquid according to claim 2, comprising a solenoid attached to the bellows and used to adjust the expansion and contraction of the bellows.

4. A measuring instrument for measuring the flow characteristics of a liquid according to claim 1, wherein the ratio (Va / V0) of the capacity of the variable-capacity container to the capacity (V0) of the fixed-capacity container is 1 / 10000 to 1 / 20.

5. A measuring instrument for measuring the flow characteristics of a liquid according to claim 1, wherein a plurality of variable-volume containers are attached to the fixed-volume container.

6. A measuring instrument for measuring the flow characteristics of a liquid according to claim 1, comprising an expandable fixed-capacity container connected to the fixed-capacity container, and a switching valve for switching the connection between the fixed-capacity container and the expandable fixed-capacity container.

7. The measuring instrument for measuring the flow characteristics of a liquid according to claim 1, wherein the variable volume container includes a bellows section, and the pressure of the pressure adjustment section is adjusted by adjusting the expansion and contraction of the bellows section, and a solenoid attached to the bellows section is used to adjust the expansion and contraction of the bellows section, and a plurality of the variable volume containers are attached to the fixed volume container.

8. A measuring instrument for measuring the flow characteristics of a liquid according to claim 7, wherein the ratio (Va / V0) of the capacity of the variable-capacity container to the capacity (V0) of the fixed-capacity container is 1 / 10000 to 1 / 20.

9. A measuring instrument for measuring the flow characteristics of a liquid according to claim 8, comprising an expandable fixed-capacity container connected to the fixed-capacity container, and a switching valve for switching the connection between the fixed-capacity container and the expandable fixed-capacity container.

10. A measuring instrument for measuring the viscosity of a liquid, according to any one of claims 1 to 9, for measuring the flow characteristics of a liquid.

11. A method for measuring the flow characteristics of a liquid, using a measuring instrument for measuring the flow characteristics of a liquid, the instrument comprising: a capillary tube having a first opening and a second opening; a first flow path connected to the first opening; a pressure adjustment unit connected to the first flow path; a switching valve for switching the connection between the first flow path and the pressure adjustment unit; and a measuring unit for measuring the fluidity of the liquid in the capillary tube, wherein the pressure adjustment unit comprises a fixed-volume container and a variable-volume container connected to the fixed-volume container, the method comprising the step of adjusting the pressure of the pressure adjustment unit by changing the volume of the variable-volume container.

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