JP5402534B2 - Liquid dispensing device - Google Patents

Description

  The present invention relates to a liquid dispensing apparatus for dispensing a sample or a reagent in an analyzer used in fields such as chemistry, industry, clinical practice, and biotechnology.

Various analyzers used in the fields of organic chemistry, biochemistry, medicine, etc. have liquid dispensing devices that automatically dispense a predetermined amount of a liquid sample or reagent into a well such as a microplate well or sample plate. There is something to prepare.
For example, Patent Document 1 describes a liquid dispensing apparatus that discharges a sample or the like filled in a space from the ejection unit by pressing a space connected to the ejection unit of the dispensing element with a driving unit made of a piezo element. ing. In a liquid dispensing apparatus having a dispensing element that dispenses liquid by driving such a piezo element, the magnitude and application time of the applied voltage to the piezo element, the rise time and fall time of the applied voltage, and the like are parameters. The amount of liquid droplets ejected from the ejection unit is adjusted by the control signal.
However, even if the parameters are the same, the volume of the ejected droplets changes depending on the physical properties such as surface tension and viscosity of the liquid to be dispensed, and environmental conditions such as temperature. Since the dispense volume is controlled by the number of droplets, changes in the droplet volume make quantitative dispensing difficult.

Patent Document 2 discloses a liquid dispensing device that discharges, for example, 1000 droplets onto the surface of a water-repellent substrate and obtains a droplet volume from the volume of 1000 droplets accumulated on the substrate. Is described. In this liquid dispensing apparatus, an image of 1000 droplets accumulated on a substrate is captured by a CCD camera, and the radius of the sphere is obtained from the image by using 1000 droplets as a sphere. The volume of the sphere is obtained from the obtained radius, and the droplet volume for one drop is calculated.
In this case, in the liquid dispensing apparatus, the volume of the droplet is obtained using a liquid (such as water) that has a large surface tension and tends to be spherical on the base material as a standard sample.

JP 2005-283123 A ([0026]) Japanese Patent Laying-Open No. 2005-49267 ([0013] to [0015], FIG. 3)

However, reagents used in the fields of biotechnology and the like contain a large amount of salts and organic solvents, and are easy to spread and become familiar with a water-repellent substrate. In this case, even if the driving parameters for dispensing are the same, there is a discrepancy between the droplet volume obtained using the standard sample and the droplet volume of the reagent or the like actually dispensed. There is a possibility that the injection amount cannot be calculated.
The problem to be solved by the present invention is to provide a liquid dispensing apparatus and a liquid dispensing method capable of obtaining a more accurate droplet volume regardless of the physical properties of the liquid.

The liquid dispensing apparatus according to the present invention, which has been made to solve the above problems,
a) a discharge unit that includes a discharge unit that discharges droplets from the tip and a discharge drive unit that drives discharge of droplets from the discharge unit;
b) control of the drive parameters of the ejection drive unit, and a drive control unit for recording the number of ejected droplets;
c) For quantitative determination, the volume from the bottom to a predetermined height position where the liquid droplets discharged from the discharge unit are stored can be expressed by an equation using information on the horizontal section at the predetermined height position as a variable. A liquid container;
d) an image reading device that reads a liquid level image of the liquid container for quantification when a predetermined number of droplets are stored in the liquid container for quantification;
e) based on the image reading apparatus has read the liquid level image, obtains information about the horizontal section at the height position of the liquid surface of the quantitative liquid storage portion, the quantitative liquid this horizontal section information from the equation calculating a total amount of a predetermined number of droplets stored in the accommodating portion, the liquid Shizukuyo product per drop to calculate the droplet volume per drop, which is calculated by dividing the droplets total volume number of droplets And a calculation unit that calculates the number of droplets necessary for dispensing a predetermined amount of liquid based on
The drive control unit adjusts a drive parameter of the ejection drive unit so as to eject the calculated number of droplets.

In addition, the liquid dispensing method according to the present invention is a driving parameter of the discharge driving unit of a discharge unit including a discharge unit that discharges droplets from the tip and a discharge drive unit that drives discharge of droplets from the discharge unit. A liquid dispensing method for dispensing a preset volume of a liquid sample by controlling
a) Discharge droplets from the discharge unit to the liquid container for quantification, which can express the volume from the bottom to a predetermined height position by using the information about the horizontal section at the predetermined height position as a variable. And steps to
b) reading a liquid surface image of the liquid container for quantification when a predetermined number of droplets stored in the liquid container for quantification has reached a predetermined number;
c) based on the read liquid surface image for information about the horizontal section at the height position of the liquid surface of the quantitative liquid container, stored this horizontal section information from the formula to the quantitative liquid containing portion Calculating the total amount of a predetermined number of droplets and dividing the total amount of droplets by the number of droplets to calculate the droplet volume per droplet;
d) calculating the number of droplets required to dispense a predetermined amount of liquid based on the calculated droplet volume per droplet;
e) adjusting a driving parameter of the discharge driving unit so as to discharge the calculated number of droplets.

  Here, the “information about the horizontal cross section” refers to a radius, a diameter, and an area when the horizontal cross section at a predetermined height position of the liquid container for determination is circular, and the horizontal cross section is a polygon. When is the length or area of one side. “Liquid surface information” is information corresponding to “information about a horizontal section” and includes a radius, a diameter, a length dimension of one side, and an area.

  According to the present invention, the droplet volume per droplet is obtained using the liquid sample to be actually dispensed, and the liquid sample is discharged so that the dispensed volume of the liquid sample becomes the set volume based on the obtained droplet volume. Since the driving of the discharge driving unit of the unit is controlled, the quantitativeness of the dispensing operation is improved. Further, the quantitative liquid storage unit is configured so that the capacity from the bottom to a predetermined height position can be expressed by an expression having information on the horizontal cross section at the predetermined height position as a variable, and the quantitative liquid storage unit Since the droplet volume per droplet was obtained from the liquid level image when a predetermined number of droplets were stored in the part, various liquid samples that were difficult to form spheres on a water-repellent substrate were also collected per droplet. The droplet volume can be determined easily and accurately. Therefore, an accurate dispensing operation can be performed regardless of the physical properties of the liquid sample.

  In this case, when the liquid container for quantification is configured so that the horizontal cross-sectional area gradually increases from the lower part to the upper part, when a predetermined number of droplets are stored in the liquid container for quantification The liquid level image can be accurately read.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic of the liquid dispensing apparatus which concerns on one Example of this invention. The schematic longitudinal cross-sectional view of a dispensing element. The figure which shows a test area | region with a functional block. The figure for demonstrating the method to calculate a liquid volume from the liquid level image of the liquid stored by the recessed part. The flowchart which shows dispensing droplet fixed_quantity | quantitative_assay operation | movement. The figure for demonstrating the example of other dispensing droplet fixed_quantity | quantitative_assay operation | movement. The figure which shows the other example of the liquid container for fixed_quantity | quantitative_assay. The figure which shows another example of the liquid storage part for fixed_quantity | quantitative_assay.

  FIG. 1 schematically shows a liquid dispensing apparatus according to this embodiment. The liquid dispensing apparatus 10 has a configuration in which a table 12, a print head 14 as a discharge unit, a CCD camera 16 and a scanner 18 are accommodated in a case made up of a main body 10a and a lid 10b.

  Four dispensing elements 20 for dispensing reagents and the like are arranged and fixed in a line on the lower surface of the print head 14. As shown in FIG. 2, in the dispensing element 20, a piezo element 28 is disposed so as to surround a capillary 26 that connects a discharge portion 22 and a liquid reservoir 24 at the tip, and the capillary 26 is driven by driving the piezo element 28. Is pushed, and the droplet L is ejected from the ejection part 22. The piezo element 28 serves as an ejection driving unit of the present invention. Since the nozzle diameter of the discharge unit 22 is very small, for example, 55 μm, the dispensing element 20 can discharge droplets in the picoliter order such that the volume per droplet is 87 pl (picoliter). The liquid sample accommodated in the liquid reservoir 24 is a sample to be analyzed or a reagent used for the analysis, and includes a nucleic acid such as DNA or RNA, an enzyme, an antigen, a protein such as an antibody, a chemical reagent, or the like. Etc.

  For example, two sample plates 34 are placed on the table 12. The table 12 is a movable table that can move in the XY direction (directions indicated by arrows X and Y in FIG. 1) in a horizontal plane. At the time of dispensing, the sample plate 34 is positioned below the designated dispensing element 20, At the time of image capture, the part to be imaged on the table 12 is positioned below the scanner 18.

  The sample plate 34 is formed of a flat plate on which a membrane 341 is attached to the upper surface, for example. The membrane 341 contains, for example, molecules such as proteins, peptides, sugars, lipids, nucleic acids, and the like, which are separated and developed in one-dimensional direction by SDS (sodium dodecyl sulfate) polyacrylamide gel electrophoresis or other chromatography, or a mixture thereof. It has become. The sample plate 34 may be a slide glass on which one or a plurality of sample sections are attached.

  On the table 12, a quantitative dispensing area 36 for performing quantitative dispensing work and a maintenance area 38 for the dispensing element 20 are provided. The dispensing operation for quantification is performed before the operation of dispensing the reagent or sample liquid to the sample plate 34 is started, and the volume per droplet discharged from the discharge unit 22 of the dispensing element 20 is determined. It is a work to seek. The quantitative dispensing area 36 and the quantitative dispensing work will be described later.

For example, a sponge is provided in the maintenance region 38. When liquid or dirt adheres to the tip of the dispensing element 20, the maintenance region 38 is moved under the dispensing element 20, and the dispensing element 20 is moved by the sponge. The liquid and dirt on the tip of the can be wiped off.
Although not shown, a mark as a base point serving as a reference for the position of the sample plate 34 disposed on the table 12 is provided on the surface of the table 12. The mark serves as a reference when taking out the dispensing position as information, and serves as a reference for matching the position on the image acquired by the scanner 18 with the movement of the table 12.

  The CCD camera 16 is for capturing an image of the tip of the dispensing element 20 when dispensing a reagent or the like from the dispensing element 20 and monitoring the state of dispensing, and is provided at the left end in the main body 10a. Has been placed. The CCD camera 16 is configured to capture an image of the tip of the dispensing element 20 regardless of which dispensing element 20 performs a dispensing operation on the sample plate 34 or the quantitative dispensing region 36. ing.

  Next, the quantitative dispensing region 36 and the quantitative dispensing work will be described with reference to FIGS. FIG. 3 shows the quantitative dispensing area 36 and the like on the table 12 together with functional blocks. The fixed dispensing region 36 is provided with a well 40 having, for example, a conical recess 40a whose horizontal cross section gradually increases from the lower part toward the upper part. The CCD camera 16 is configured to capture an image of the top surface of the recess 40a in addition to an image of the tip of the dispensing element 20. The image captured by the CCD camera 16 is input to the image processing device 41. The image processing device 41 includes an image storage unit 43 and an image processing unit 45. An image display unit 47 is connected to the image processing unit 45. When the drive control unit 49 notifies the image processing device 41 that the number of droplets discharged from the dispensing element 20 into the recess 40a has reached a predetermined number, the image storage unit 43 displays the image captured by the CCD camera 16. Remember. The image stored in the image storage unit 43 is subjected to image processing such as binarization and contour extraction in the image processing unit 45, and the radius of the liquid level of the liquid stored in the recess 40a is obtained. The image processing unit 45 may obtain the diameter.

FIG. 4 shows an enlarged view of the recess 40a. The recess 40a is a conical container in which the radius of the upper opening surface is R ₀ and the height from the bottom of the recess 40a to the upper opening surface is H ₀ . The values of R ₀ and H ₀ are obtained in advance.
Table Now, when the radius of the upper surface of the liquid stored in the recess 40a (liquid surface) and r _1, height h ₁ from the bottom surface of the recess 40a at that time to the liquid surface is the following equation (1) Is done.
h ₁ = r ₁ / R ₀ × H ₀ ... (1)
Therefore, the volume V1 from the bottom to the liquid level at that time is expressed by the following equation (2).
^{_{V 1 = πr 1 2 h 1}} /3 = πr 1 3 / R 0 × H 0/3 ··· (2)
In this way, if the radius r ₁ is obtained from the liquid level image captured by the CCD camera 16, the volume of the liquid stored in the recess 40a can be calculated. Expression (2) representing the relationship between the radius r _{1 of the} liquid level and the volume V _{1 of} the droplet stored in the recess 40 a is stored in advance in the calculation unit 51.

When the number of droplets ejected by the dispensing element 20 reaches a predetermined value, the drive control unit 49 reads the liquid surface radius r ₁ from the image processing unit 45 and calculates the number of droplets and the radius r ₁ . To the unit 51. The calculation unit 51 obtains the volume of the liquid in the recess 40a from the radius of the liquid surface, calculates the droplet volume per droplet from this volume and the number of droplets, and further dispenses a predetermined amount of liquid. The number of droplets necessary for the calculation is calculated. In the present embodiment, the recess 40a serves as a liquid container for determination. The “predetermined amount” is the amount of liquid sample dispensed to the sample plate 34 and is set in advance by the operator.

  When the number of droplets necessary to dispense a predetermined amount of liquid is calculated by the calculation unit 51 in this way, the drive control unit 49 determines the magnitude of application voltage to the piezo element 28, the application time, and the rise of the application voltage. The drive of the piezo element 28 is controlled by adjusting drive parameters including all of the time / fall time or at least one of them. Thereby, a droplet is discharged from the discharge part 22 of the dispensing element 20.

  FIG. 5 is a flowchart showing the dispensing operation process. In this embodiment, the dispensing work for quantitative determination is performed prior to the dispensing work of the liquid sample onto the sample plate 34 (hereinafter referred to as “analysis dispensing work”). First, when a drive parameter is set (S1), the drive controller 49 controls the drive of the piezo element 28 according to this drive parameter, and executes a quantitative dispensing operation (S2). When the number of droplets discharged to the recess 40a reaches a predetermined value, the drive control unit 49 takes in the liquid level L image stored in the well 40 stored in the image storage unit 43 (S3). ) The radius r of the liquid level LP is obtained by image processing (S4). The calculation unit 51 uses a calculation formula stored in advance to obtain the volume of the liquid stored in the well 40 from the radius r of the liquid surface (S5), and droplets per droplet are calculated from the liquid volume and the number of droplets. The volume is calculated (S6). Next, an amount of liquid sample to be dispensed to the sample plate 34 (hereinafter referred to as “dispensed liquid amount”) is set (S7), and the liquid of the dispensed liquid amount is dispensed from the dispensed liquid volume and the droplet volume. The number of droplets necessary for pouring is calculated (S8).

  Subsequently, the drive control unit 49 performs an analysis dispensing operation on the sample plate 34 according to the drive parameters set in S1 and the number of droplets calculated in S7 (S9). In addition, when a plurality of analytical dispensing operations are continuously performed (No in S10), a dispensing liquid amount is set before each analytical dispensing operation, and the dispensing liquid amount and one drop are set. The number of droplets is calculated from the per droplet volume.

It should be noted that the number of times the liquid level image is captured by the CCD camera 16 is set to twice, and the liquid droplet volume per droplet is obtained from the liquid surface radius at the first imaging time point and the liquid surface radius at the second imaging time point. good. Specifically, as shown in FIG. 6, if the liquid surface diameter at the first imaging time is 2r, the height is h, the liquid surface diameter at the second imaging time is 2R, and the height is H, The total volume V of the droplets discharged to the well 40 from the first imaging time point to the second imaging time point is given by the following equation.
V = πR ² H / 3−πr ² h / 3

  As described above, since the height from the bottom of the recess 40a of the well 40 to the liquid level is expressed as a function of the liquid level radius, if the liquid level radius is obtained, the first imaging time point to the second imaging time point are obtained. The total volume V of the droplets discharged to the well 40 can be obtained.

Further, the present invention is not limited to the above-described embodiments, and for example, the following modifications are possible.
In addition to the pyramid shape, the liquid container for determination may have a shape as shown in FIG. The fixed-quantity liquid container shown in FIG. 7 is a rectangle whose bottom surface is composed of sides of length d ₀ and W _a , and whose upper opening surface is a rectangle composed of sides of length d ₀ and W _b. This is a container having a height of up to H ₀ . That is, as shown in FIG. 7, it has a pair of opposite trapezoidal side surfaces. These values of d ₀ , H ₀ , W _{a and} W _b are obtained in advance.
After the start of dispensing, with respect to the liquid level at the time of first imaging, if one side in contact with the trapezoidal side surface is W ₁ among the rectangular sides forming the liquid level, the liquid level starts from the bottom of the container at the time of first imaging. The height h ₁ up to the surface is expressed by equation (3).
_{h 1 = (w 1 -w a} ) / (w b -w a) × H 0 ···· (3)
The volume from the bottom surface to the liquid surface at the time of the first imaging after the start of dispensing is expressed by equation (4).
_{V 1 = (w a + w} 1) × h 1/2 × d 0
_{= (W a + w 1)} × (w 1 -w a) / (w b -w a) × H 0/2 × d 0 ··· (4)
Accordingly, if the length w ₁ of one side of the liquid level is obtained from the image of the liquid level captured by the CCD camera 16, the droplet volume can be calculated.

FIG. 8 shows another modification of the liquid container for quantitative determination. The liquid container for quantitative determination shown in FIG. 8 has a combination of a conical shape and a cylindrical shape, and the horizontal cross-sectional area from the bottom to the height h ₀ is constant, but the height exceeds h ₀ . And the horizontal cross section gradually increases. In this case, set such that the height h of the liquid level of the quantitative liquid accommodating portion when a predetermined number of droplets stored is greater than the height h _0. Then, since the volume of the liquid droplet stored in the container can be expressed by an expression having the liquid surface area as a variable, the volume of the liquid droplet stored in the container is obtained from the captured liquid surface image. As a result, the volume per droplet can be determined.

  The formula for obtaining the volume of liquid stored in the liquid container for determination is information obtained by performing image processing of the liquid level image captured by the CCD camera, for example, when the liquid level is circular, the diameter, radius, liquid level Is a polygonal shape, it can be expressed by an expression having the length dimension of one side as a variable. In addition, it can also be expressed by a formula having the liquid surface area as a variable.

  The dispensing element may use a syringe pump as a drive source. The control signal in this case can be a drive parameter including at least one of the stroke, speed, and acceleration of the plunger of the syringe pump. In FIG. 1, the CCD camera is configured to be able to capture not only the image of the tip of the dispensing element 20 but also the image of the upper surface of the recess 40a. However, at least the image of the upper surface of the recess 40a can be captured. I can do it.

DESCRIPTION OF SYMBOLS 10 ... Liquid dispensing apparatus 12 ... Table 14 ... Print head 16 ... CCD camera (image reading apparatus)
DESCRIPTION OF SYMBOLS 18 ... Scanner 20 ... Dispensing element 22 ... Discharge part 28 ... Piezo element 34 ... Sample plate 36 ... Fixed quantity dispensing area 40 ... Well 41 ... Image processing apparatus 43 ... Image storage unit 45 ... Image processing unit 47 ... Image display unit 49 ... Drive control unit 51 ... Calculation unit

Claims (4)

a) a discharge unit that includes a discharge unit that discharges droplets from the tip and a discharge drive unit that drives discharge of droplets from the discharge unit;
b) control of the drive parameters of the ejection drive unit, and a drive control unit for recording the number of ejected droplets;
c) The volume from the bottom to the predetermined height position where the liquid droplets discharged from the discharge unit are stored can be expressed by an expression using information on the horizontal section at the predetermined height position as a variable. A liquid container;
d) an image reading device that reads a liquid level image of the liquid container for quantification when a predetermined number of droplets are stored in the liquid container for quantification;
e) Based on the liquid level image read by the image reading device, information on a horizontal section at the height position of the liquid level of the liquid container for quantitative determination is obtained, and the liquid for quantitative determination is obtained from the horizontal sectional information and the formula. calculating a total amount of a predetermined number of droplets stored in the accommodating portion, the liquid Shizukuyo product per drop to calculate the droplet volume per drop, which is calculated by dividing the droplets total volume number of droplets And a calculation unit that calculates the number of droplets necessary for dispensing a predetermined amount of liquid based on
The liquid dispensing apparatus, wherein the drive control unit adjusts a drive parameter of the ejection drive unit so as to eject the calculated number of droplets.   The liquid dispensing apparatus according to claim 1, wherein the liquid container for quantitative determination is configured so that a horizontal cross-sectional area gradually increases from the lower part toward the upper part. By controlling the drive parameters of the discharge drive unit of a discharge unit including a discharge unit that discharges droplets from the tip and a discharge drive unit that drives discharge of droplets from the discharge unit, In a liquid dispensing method for dispensing a liquid sample,
a) Discharge droplets from the discharge unit to the liquid container for quantification, which can express the volume from the bottom to a predetermined height position by using the information about the horizontal section at the predetermined height position as a variable. And steps to
b) reading a liquid surface image of the liquid container for quantification when a predetermined number of droplets stored in the liquid container for quantification has reached a predetermined number;
c) based on the read liquid surface image for information about the horizontal section at the height position of the liquid surface of the quantitative liquid container, stored this horizontal section information from the formula to the quantitative liquid containing portion Calculating the total amount of a predetermined number of droplets and dividing the total amount of droplets by the number of droplets to calculate the droplet volume per droplet;
d) calculating the number of droplets required to dispense a predetermined amount of liquid based on the calculated droplet volume per droplet;
e) adjusting the drive parameters of the discharge drive unit so as to discharge the calculated number of droplets.   The liquid dispensing method according to claim 3, wherein the liquid container for quantitative determination is configured so that a horizontal cross-sectional area gradually increases from the lower part toward the upper part.

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