JP2004251820A - Dispensing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a dispensing apparatus is assembled by using expensive components, such as a piezoelectric actuator and a solenoid valve, for generating droplets and hence the number of components increases if a drive circuit, or the like, is included, and as a result the entire apparatus becomes extremely expensive. <P>SOLUTION: A dispensing method comprises a process for sucking air from a nozzle hole from an initial state where a liquid to be dispensed fills the nozzle hole at the tip of a pipet; and a process for feeding the liquid in the direction of the nozzle hole speedily with the amount of feed that is the sum of the amount of return travel for traveling in the process of air suction operation and a discharge volume that becomes a desired amount of dispensation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dispensing method for dispensing a small amount of liquid from a hole at the tip of a pipette.
[0002]
[Prior art]
The conventional dispensing method for dispensing an amount smaller than the amount of liquid droplets (approximately 10 μl) in which the liquid falls by its own weight is to change the volume of the syringe to send the liquid to the pipette tip, and to dispense the inner wall surface of the container to be filled. A method of dispensing by applying the liquid on the surface has generally been adopted. According to this method, since the liquid that has reached the inner wall surface due to the adhesive force of the liquid does not fall to the bottom of the container by its own weight, a post-process such as moving the liquid to the bottom using centrifugal force is required. Was.
[0003]
In addition, there is concern about contamination because the tip of the pipette is brought into contact with the inner wall surface of the container. In order to solve this, for example, as described in Japanese Patent Application Laid-Open No. 2001-228060, a piezoelectric actuator is used to pressurize the liquid to forcibly make a small amount of liquid droplet, and the droplet is made to fly from the hole at the tip of the pipette. Dispensing technology has been proposed.
[0004]
Further, as another technique, a technique has been proposed in which a liquid is generated and then dispensed by jetting a liquid by pressurizing a liquid in advance and instantaneously opening and closing a solenoid valve provided in the storage tube.
[0005]
[Problems to be solved by the invention]
As described above, in the case of a minute amount dispensing, it is desirable to generate a small amount of droplets by some means and fly to dispense. However, in order to generate liquid droplets, expensive components such as piezoelectric actuators and solenoid valves are used to incorporate them into the dispensing device. It will be quite expensive.
[0006]
An object of the present invention is to solve the above-mentioned problem and to provide a dispensing method capable of generating a droplet and performing flight dispensing without using a special component such as a piezoelectric actuator.
[0007]
[Means for Solving the Problems]
The above-described object is achieved by setting a step of an operation of sucking air from the nozzle hole and a return movement amount moved in the step of the air suction operation from an initial state where the liquid to be dispensed to the nozzle hole at the tip of the pipette is filled. And a step of sending the liquid in the direction of the nozzle hole at a high speed with a feed amount obtained by adding the discharge volume integral which is the dispensed amount of the liquid.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing the dispensing method of the present invention, and FIG. 2 is a side view of the tip of the pipette 1 showing the liquid level of the liquid in three states. FIG. 3 is a partial cross-sectional view of the dispensing apparatus 10 as viewed from the side. First, the configuration of the dispensing apparatus 10 will be described below.
[0009]
The pipette 1 having a nozzle hole 1a having a diameter of about 0.6 mm at the tip is fixed by a pipette grip 6 with a screw 6a. The piston 2 that moves in contact with the inner wall surface of the pipette 1 is fixed by a screw 5 a by a piston grip 5, and the piston grip 5 is connected to the shaft 4 of the linear stepping motor 3. The pipette grip 6 and the linear stepping motor 3 are configured to be fixed to a U-shaped base 7. The linear stepping motor 3 is a motor in which the shaft 4 directly moves linearly. By transmitting a pulse train signal from the control device 20 to a driver 21 for driving the linear stepping motor 3, the speed control and the positioning control of the piston 2 in the reciprocating direction can be performed. It has become.
[0010]
Next, the dispensing method according to the present invention will be described below based on the flowchart shown in FIG. In advance, as in the initial state shown in FIG. 2A, the liquid surface 8a of the liquid 8 to be dispensed is filled up to the nozzle hole 1a at the tip of the pipette 1. Data necessary for the operation such as the dispensed amount is set in the control device 20 in advance by an operation switch or the like (not shown).
In processing step 100, when control device 20 receives a request for starting dispensing, dispensing work is started.
First, an air suction operation is performed in processing step 110. In the air suction operation, the control device 20 sends a predetermined number of pulses to the driver 21, moves the piston 2 in a direction opposite to the discharge direction, and sucks air from the nozzle hole 1a. The state of the liquid surface 8b at this time is shown in FIG. In order to prevent air bubbles from entering the pipette 1 during the air suction operation, it is preferable that the pulse train signal during the suction operation be operated slowly with a lower frequency signal as the viscosity of the liquid is higher.
[0011]
Subsequently, the process of the processing step 120 described below is executed by a human or a robot hand toward the container 9 to which the tip of the pipette 1 is to be dispensed. In processing step 120, control device 20 sends a relatively high-speed pulse train signal to driver 21. The number of pulses at this time is a feed amount (number of pulses) obtained by adding a discharge body integral that is a desired dispensing amount to the return movement amount of the air suction operation in the processing step 110. When the process of this processing step 120 is performed, the liquid starts to move toward the nozzle hole 1a from the state of FIG. 2B, and collides with the nozzle hole 1a to form a droplet, and finally a desired dispensing is performed. By discharging the amount, the droplet 8d is fly-injected into the container 9, and the dispensing operation is completed (processing step 130). If the position of the liquid level 8c after this dispensing operation is almost the same as the liquid level position 8a in the initial state, it means that the desired dispensing amount has been dispensed with high accuracy.
[0012]
Subsequently, when dispensing to another container 9 is performed, the tip of the pipette 1 is directed to another container 9 by hand or a robot hand, and the processes of the processing steps 110 and 120 of the dispensing method described above are performed. Just do it.
[0013]
According to the experiment of the inventor, the inner diameter of the used pipette 1 was 2 mm, the nozzle hole diameter was 0.6 mm, the movement amount per pulse of the shaft 4 of the linear stepping motor 3 was 10.2 μm, and the air suction was performed. The number of return pulses is set to 60 pulses, so the return movement amount is about 0.6 mm. When the dispensed volume is, for example, 1 μL, the inner diameter of the pipette 1 is 2 mm, and the displacement of the piston 2 for the discharge volume is 0.318 mm, which is 31 pulses in terms of the number of pulses. Therefore, the feed amount at the time of moving in the processing step 120 is 91 pulses (approximately 0.9 mm) obtained by adding 31 pulses corresponding to the dispensed discharge volume to 60 pulses of the air suction operation. Regarding the sending speed, if the speed is too slow, the droplet 8d is not formed, and if the speed is too fast, the ejection speed of the droplet 8d increases, and the droplet 8d vigorously enters the container 9, and the rebounding droplet causes the contamination. It's not good to be too slow or too fast.
[0014]
According to the experiment of the present inventor, when the nozzle hole diameter is 0.6 mm, the feeding speed is preferably in the range of 60 to 120 mm / s, and particularly, when the piston 2 is operated at about 70 mm / s, the droplet 8d is formed. , The capacity is stable. When pure water was dispensed by the above-described method and the weight thereof was measured by an electronic balance, a good result of about ± 10% accuracy was obtained by dispensing 1 μL.
[0015]
In addition, even when the dispensed amount is relatively large, droplets may adhere to the tip of the pipette 1 at the end of discharging the liquid. In this case, a tip touch operation for attaching to the inner wall surface of the container 9 has conventionally been performed. Was. However, by performing the above-described dispensing method, the droplets attached to the tip can be surely dispensed by flying, and the tip touch operation can be omitted.
[0016]
【The invention's effect】
According to the present invention, from the initial state in which the liquid to be dispensed up to the nozzle hole at the tip of the pipette is reduced to a step of an operation of sucking air from the nozzle hole and a return movement amount moved in the step of the air suction operation. The step of sending the liquid in the direction of the nozzle hole at a high speed with a feed amount obtained by adding the discharge volume integral to obtain a desired dispensing amount is provided. A dispensing method that can be formed can be provided.
[Brief description of the drawings]
FIG. 1 is a flowchart showing one embodiment of a dispensing method of the present invention.
FIG. 2 is a side view of a pipette tip showing a liquid level position of a liquid according to one embodiment of the dispensing method of the present invention.
FIG. 3 is a partial cross-sectional view of a dispensing device 10 of one embodiment according to the dispensing method of the present invention as viewed from a side.
[Explanation of symbols]
1 is a pipette, 1a is a nozzle hole, 2 is a piston, 3 is a motor (linear stepping motor), 8 is a liquid, 8d is a droplet, 9 is a container, 10 is a dispensing device, 20 is a control device, 21 is a driver, 100 is an air suction operation step, and 110 is a droplet discharge operation step.

Claims (1)

From the initial state in which the liquid to be dispensed to the nozzle hole at the tip of the pipette is filled, a desired dispensing amount is added to the step of suctioning air from the nozzle hole and the return movement amount moved in the step of air suction operation. A step of sending out the liquid in the direction of the nozzle hole at a high speed with a feed amount obtained by adding the integral of the discharge body.

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