JP5067415B2 - Method for driving droplet discharge device - Google Patents

Description

In the present invention, when dispensing a predetermined amount of liquid in a reagent container or other liquid container used for biochemical analysis, immunological analysis, etc., the liquid in the container is accurately and accurately aspirated. The present invention relates to a droplet discharge device and a driving method that can dispense well.

A conventional pipette type droplet discharge device will be described with reference to FIG. 100 is a stepping motor, 111 is a ball screw, 112 is a drive cylinder, 113 is a piston rod, 120 is a high-speed plunger, 130 is a stepping motor, 140 is a pipette, 145 is a syringe for liquid suction, 150 is a switching valve, 160 is The second port, 170 is an on-off valve, 180 is a pressurizing / washing syringe, and 190 is a pressure feed passage.
A conventional pipette type droplet discharge device includes a pipette 140 that sucks a required amount of liquid, a liquid suction syringe 145 that performs a suction dispensing operation by the pipette 140, and the liquid suction syringe 145 and the pipette 140 that communicate with each other. A high-speed plunger 120 interposed in the middle of the pipette side flow path 200 to be connected, a pressure feed path 190 communicatively connected to the pipette side flow path 200, and a pressure connected to the terminal portion of the pressure feed path 190. A pressure / washing syringe 180 and a switching valve 150 interposed in the middle of the pressure-feeding passage 190 are configured, and the liquid sucked by the pipette 140 is dispensed in a required amount. Yes. (Patent Document 1)

Next, a case where liquid is sucked will be described. The pipette 140 is lowered and immersed in the liquid in the suctioned liquid storage container by a ball screw whose forward and reverse rotation is controlled by the stepping motor 130. Thereafter, the high-speed plunger 120 is set to ON, the switching valve 150 is set to the second port 160 in a communicating state, and the on-off valve 170 is set to a closed state. In this state, the pressurizing / washing syringe 180 pressurizes the inside of the pressure feeding channel 190 and the pipette side channel 200. The piston rod 113 descends and the liquid in the liquid container to be sucked is sucked. The piston rod 113 is connected to a drive cylinder 112 that is screwed into a ball screw 111 that is controlled to rotate in the forward and reverse directions by the stepping motor 100, and is controlled to move up and down. At this time, the pressurizing / cleaning syringe 180 is driven and controlled so that the cleaning liquid and the air are in a constant ratio in the pressure feed channel 190 and the pipette side channel 200.

A case of dispensing a liquid will be described. After the pressurizing / washing syringe 180 pressurizes the inside of the pressure feeding channel 190 and the pipette side channel 200, the pipette 140 is lowered at the dispensing position by the stepping motor 130, and the high-speed plunger valve 120 is turned on for a predetermined time. By doing so, the required amount of liquid is dispensed. The amount dispensed was controlled by the time during which the high-speed plunger 120 was in the ON state.
JP 2004-61153 A (5th page, FIG. 1)

However, according to the conventional droplet dispensing device, the pipette side flow path is pressurized so that the cleaning liquid and air are in a certain ratio. However, the air is compressed when pressurized, and a high-speed plunger is used. When it was opened, the amount of pressurization was not constant due to expansion, and the expansion rate changed due to environmental changes such as ambient temperature and atmospheric pressure.
In addition, the liquid volume is controlled by the open time of the high-speed plunger in the ON state. However, the dispersion of the dispensing volume is caused by the surface tension of the liquid and the liquid volume remaining at the nozzle tip after dispensing. It was. For this reason, there was a problem that an accurate liquid amount could not be obtained. If such variations in liquid volume occur, quantitative results cannot be obtained, and re-tests must be performed for analyzes that require quantitative properties such as DNA analysis, and expensive liquids are wasted. The problem that it ends up has arisen.
It also includes a syringe, a stepping motor for driving the piston, a ball screw for moving the piston, a sample liquid control system consisting of a high-speed blanker, etc., a switching valve, a stepping motor for driving the piston, a ball screw and the like. It consists of a pressure / cleaning system, and the liquid is discharged by the two systems, so the device is large. When dispensing work is performed simultaneously on multiple axes, the device is too large to fit in the installation space. The problem of not having occurred.
The present invention has been made in view of the above problems, and provides a small droplet discharge device and a driving method thereof, in which droplets are discharged with high accuracy and variations in droplet liquid amount can be reduced. Objective.

In order to solve the above problem, the present invention is as follows.
The present invention is processed in the steps of a suction process in which the liquid amount remaining at the tip of the nozzle is sucked, a discharge process in which a required amount of liquid is dispensed, and a suction process in which the discharged droplets are separated.
According to the present invention, the constant speed region is automatically calculated by addition / subtraction so that the driving pattern of the suction, discharge, and suction processes is constant.
In the present invention, the deceleration time is automatically calculated in the deceleration region so that the driving pattern of the suction, discharge, and suction processes has a constant movement amount.
Further, the present invention includes a drive pattern storage unit that stores the drive pattern and a command generation unit that generates the drive pattern.

According to the present invention, since the drive pattern is automatically calculated in the process of discharging the required amount of liquid, the conditions for reducing the variation in the liquid amount are easily optimized.
In addition, according to the present invention, since the drive pattern storage unit is provided, the relationship between the drive pattern and the liquid amount can be easily compared, and the liquid amount can be optimized by using the stored drive pattern.
As described above, according to the present invention, a liquid pool remaining at the tip of the nozzle is detected by the liquid level detection sensor, and the drive pattern is optimized, whereby an accurate discharge amount can be obtained. Moreover, since it has a simple structure in which a liquid level detection sensor is provided at the tip of the nozzle, it is easy to reduce the size.

Hereinafter, a specific embodiment of the droplet discharge device of the present invention will be described with reference to FIG.

FIG. 1 is a cross-sectional view showing the configuration of a droplet discharge apparatus for carrying out the method of the present invention. In the figure, 1 is a motor, 2 is a ball screw, 21 is a nut, 3 is a piston, 4 is a syringe, 5 is a nozzle, and 6 is a liquid level detection sensor.
The droplet discharge device is attached to the syringe 4 and the ball screw 2 connected to the motor 1, the nut 21 screwed into the ball screw 2, the piston 3 connected to the nut 21, and reciprocating in the syringe 4. And a liquid level detection sensor 6 arranged at the tip of the nozzle.
When the motor 1 rotates forward and backward, the piston 3 connected to the nut 21 screwed into the ball screw 2 reciprocates in the syringe 4. The liquid is sucked and discharged through the nozzle 5 provided at the discharge port of the syringe 4. The liquid level detection sensor 6 detects the presence or absence of liquid at the tip of the nozzle 5.
The liquid level detection sensor 6 has the configuration shown in FIG. The nozzle 5 is made of an insulating material such as glass or free-cutting ceramic, and the convex portions 51 are provided at two locations so as to face the tip of the nozzle 5. Further, the electrode 61 is disposed so as to be opposed to the convex portion 51.
Here, the description has been given using the nozzle 5 made of an insulator provided with the convex portion 51. However, as another nozzle shape, as shown in FIG. 3, the nozzle 5 is provided with the convex portion 51 at the tip, and aluminum or It is made of metal material such as SUS304. In the metal electrode 61, an insulating layer 62 made of a fluororesin or the like is coated on the metal electrode 61 and is fitted into the convex portion 51 of the nozzle 5.
On the contrary, the metal electrode 61 may be formed of a metal material, and the surface of the nozzle 5 made of the metal material may be formed of an insulating film such as an alumite process or a fluororesin film.

The presence or absence of liquid at the tip of the nozzle 5 is determined by a change in capacitance between the electrodes 61. The capacitance is obtained from the relationship shown in Equation 1. When there is glycerin as a liquid between the electrodes 61, the relative dielectric constant of glycerin is 42.5, so that the capacitance is detected about 42 times that in the case of air. In this way, the presence or absence of liquid is detected by detecting the capacitance proportional to the relative dielectric constant.

A state of discharging the liquid will be described with reference to FIG. When the liquid is sucked, a liquid pool due to the surface tension of the liquid is generated at the tip of the nozzle 5 as shown in FIG. At this time, a high capacitance is detected by the electrode 61.
Next, in the suction step (FIG. 4B) for sucking the amount of liquid remaining at the tip of the nozzle 5, the liquid is sucked until the capacitance value between the electrodes 61 becomes a low value. That is, the liquid is sucked until it is in an air state, and the liquid is completely in the nozzle 5.
Next, in the discharge step (FIG. 4C) in which the liquid is dispensed, the liquid is discharged from the tip of the nozzle 5 to form a droplet. Capacitance shows a high value in the state where droplets remain.
Next, in the suction step (FIG. 4D) for separating the droplets, the droplets are cut by being rapidly sucked and dropped into a measurement container (not shown). Capacitance shows a low value when sucked.
As described above, the liquid level detection sensor 6 detects the amount of liquid remaining at the tip of the nozzle 5 before the liquid is discharged, and the liquid level detection sensor 6 detects the liquid remaining at the tip of the nozzle 5. By sucking the liquid to a position where the liquid level is not detected, the variation in the discharge liquid amount is reduced regardless of the size of the liquid pool remaining at the tip of the nozzle 5. In addition, after the liquid is ejected, a suction process for separating the liquid droplets is performed, so that the liquid droplets are improved and there is no liquid pool at the tip of the nozzle 5. Decrease.

A method of generating a drive pattern when droplets are ejected will be described with reference to FIG. If overshoot is applied during acceleration from the speed trapezoidal speed pattern (dotted line) (Fig. 5 (a)), the overshoot is discharged more than the set capacity. Here, considering the droplet discharge phenomenon, in order to discharge a very small amount of droplet, the acceleration obtained from Equation 2 is necessary in relation to the surface tension of the liquid. For this reason, the slope of the acceleration region cannot be adjusted. However, in the constant velocity region, even if velocity ripple occurs as shown in FIG. 5B, pulsation occurs in the liquid amount, but the liquid amount is not affected. Therefore, the movement amount of the speed pattern including the overshoot in this constant speed region is obtained by subtraction calculation so as to be equal to the movement amount of the speed trapezoid pattern.

As shown in FIG. 6, another drive pattern generation method when overshoot is added to the acceleration region is obtained by calculating the deceleration time so that the movement amount is constant. In the deceleration area, it is sufficient that the liquid is braked, so that the acceleration and the deceleration need not coincide.
As described above, in the process of discharging the liquid, the set liquid amount is easily generated by the automatic calculation of the drive pattern, so that the conditions with small variations in the liquid amount are easily optimized.

As shown in FIG. 7 (a), the control device 7 of the motor 1 includes a command generation unit 71 that sets a movement amount, an encoder signal processing unit 74 that determines the position of the motor, and a position obtained from the encoder signal processing unit 74. It is converted into a drive speed based on the position information obtained by the gain adjustment unit 72 that compares the information with the command and adjusts the gain, the current amplifier 73 that generates a current proportional to the gain, and the encoder signal processing unit 74, and the drive The speed pattern storage unit 75 stores the pattern.
If the optimum drive pattern is obtained with the speed pattern as shown in FIG. 7B by comparing the evaluation result of the liquid amount and the drive pattern, this speed pattern data is stored in the speed pattern storage unit 75. As a result, the drive pattern is optimized.
As described above, since it has a simple structure in which the liquid level detection sensor is provided at the nozzle tip, it is easy to reduce the size. In addition, a liquid pool remaining at the tip of the nozzle is detected by the liquid level detection sensor, and the drive pattern is optimized, so that an accurate discharge amount can be obtained.

This device can be applied not only to biochemical analysis such as DNA analysis, but also to dispensing devices in fields such as immunological analysis in which a small amount of liquid is handled because the droplets are ejected accurately.

1 is a side sectional view of a droplet discharge device showing a first embodiment of the present invention. Sectional drawing of the liquid level detection sensor which shows 1st Example of this invention Sectional drawing of the liquid level detection sensor provided with the insulating film which shows the 1st Example of this invention Droplet ejection procedure and liquid level detection sensor output showing the first embodiment of the present invention Correction speed pattern in a constant speed region showing the first embodiment of the present invention Correction speed pattern in the deceleration region showing the first embodiment of the present invention Control device and speed pattern data showing second embodiment of the present invention Diagram showing a conventional droplet discharge device

DESCRIPTION OF SYMBOLS 1 Motor 2 Ball screw 21 Nut 3 Piston 4 Syringe 5 Nozzle 51 Convex part 6 Liquid level detection sensor 61 Nozzle 62 Insulating layer 7 Control device 71 Command generation part 72 Gain adjustment part 73 Current amplifier 74 Encoder signal processing part 75 Speed pattern storage part 100 Stepping motor 111 Ball screw 112 Drive cylinder 113 Piston rod 120 High-speed plunger 130 Stepping motor 140 Pipette 145 Liquid suction syringe 150 Switching valve 160 Second port 170 On-off valve 180 Pressurization / washing syringe 190 Pressure feed channel 200 Pipette Side flow path

Claims (4)

A piston contained in a syringe; a nut connected to an end face of the piston protruding from the syringe; a ball screw screwed with the nut; a motor for driving the ball screw; A method for driving a droplet discharge device comprising a nozzle provided at the tip of the syringe discharge port ,
A first step of sucking the liquid material remaining in said nozzle tip,
Said nozzle tip in which the droplet is sucked by the first step, a second step of forming the required amount of liquid droplets,
A third step of separating the droplets by sucking the droplets formed in the second step and discharging the droplets ;
A method for driving a droplet discharge device, comprising: 2. The driving of the droplet discharge device according to claim 1 , wherein the driving pattern of the second step is such that a constant speed region is automatically calculated by addition and subtraction so that a moving amount of the piston becomes constant. Method. 2. The driving of the droplet discharge device according to claim 1 , wherein the driving pattern of the second step is such that a deceleration time is automatically calculated in a deceleration region so that a moving amount of the piston is constant. Method. 4. The method for driving a droplet discharge device according to claim 2, further comprising a control device including a drive pattern storage unit that stores the drive pattern and a command generation unit that generates the drive pattern. .

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