CN114480597B - Digital PCR-based droplet detection method and device - Google Patents
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Abstract
The invention discloses a droplet detection method and device based on digital PCR, wherein the method comprises the following steps: controlling sample injection to perform needle-setting operation on a sample droplet test tube, and detecting whether the sample injection needle reaches a preset position; sampling the sample droplet when the sample injection needle reaches a preset position; and (3) transmitting the sampled sample droplets to a detection chip through a pipeline by the negative pressure formed by the flow velocity difference, and detecting. When the sampling needle is at the preset position, the sampling is carried out again to ensure that the sampling needle is at a proper distance from the test tube, so that the condition that the sampling needle is too high or too low from the bottom of the test tube during direct sampling can be avoided, and the sampling of sample droplets is difficult or too much residue is caused. The negative pressure formed by the flow velocity difference can suck the sample droplet directly to the detection chip without passing through other elements in the pipeline, so that the integrity of the sample droplet is ensured. The bubble sensor is used for monitoring the position of the sample droplet and adjusting the detection time in real time, so that the detection accuracy and stability are further improved.
Description
Technical Field
The invention relates to the technical field of droplet detection, in particular to a droplet detection method and device based on digital PCR.
Background
The microfluidic droplet technology is a brand new technology for controlling tiny volume liquid developed on the basis of microfluidics. The droplets generated by the technology are micro-reaction units with nano-liter and even picoliter volumes, and are applied to the fields of protein crystallization, cell analysis, rapid enzyme reaction kinetics research, digital PCR (Polymerase Chain Reaction ), gene sequencing and the like. Compared with the traditional microplate method, the microfluidic droplet platform can rapidly and stably generate droplets with uniform size, and the screening flux of the microfluidic droplet technology can be improved by 1000 times, so that the microfluidic droplet technology has great potential to become a next-generation ultrahigh flux screening platform.
Digital PCR is the latest quantitative technique, which is based on single-molecule PCR method to perform quantitative nucleic acid counting, and is an absolute quantitative method. The method mainly adopts a microfluidic chip method or a microdroplet method in the current analytical chemistry hot research field to disperse a large amount of diluted nucleic acid solution into micro-reactors or microdroplets of a chip, wherein the number of nucleic acid templates of each reactor is less than or equal to 1. Thus, after PCR cycles, the reactor with the template of the nucleic acid molecule gives a fluorescent signal, and the reactor without the template has no fluorescent signal. From the relative proportions and the volume of the reactor, the nucleic acid concentration of the original solution can be deduced.
When detecting the microdroplet, the sample injection system is required to extract the microdroplet sample to the detection area, and then the optical detection equipment is used for detecting the microdroplet sample on the detection area; the traditional sampling system has fluctuation in the height from the sampling needle to the sample test tube, if the sampling needle and the test tube are stuck too close to each other for sucking samples or the sampling needle and the test tube are too far apart to cause excessive residues. The switching valve for controlling on-off and switching direction is usually arranged on the sample injection pipeline, so that the droplets pass through more pipeline paths and pipeline connection sections before entering the detection area, huge damage is easily caused to the droplets, the droplets are broken, mixed or incompletely absorbed in the conveying process, detection is difficult, and the result is inaccurate. The detection time is insufficient or overlong due to certain difference of the volumes of the samples to be detected. Meanwhile, due to the complexity of a liquid path system, the PCR detection instrument has the problems of high failure rate, difficult maintenance and the like.
Disclosure of Invention
The purpose of the invention is that: a droplet detection method and device based on digital PCR are provided, and the accuracy of droplet detection is improved.
In order to achieve the above object, the present invention provides a droplet detection method based on digital PCR, comprising: controlling sample injection to perform needle-setting operation on a sample droplet test tube, and detecting whether the sample injection needle reaches a preset position;
Sampling the sample droplets in the sample droplet test tube when the sample injection needle reaches the preset position;
And transmitting the sampled sample droplets to a detection chip through a pipeline by negative pressure formed by the flow velocity difference so that the detection chip detects the sample droplets.
Further, the control sample injection is performed on the sample droplet test tube, and whether the sample injection needle reaches a preset position is detected, specifically:
controlling the sample injection to perform needle-down operation on the sample droplet test tube, and detecting whether the sample injection needle is positioned at the bottom of the sample droplet test tube according to data acquired by a pressure sensor; the pressure sensor is arranged on a sampling arm of the sampling needle;
When the sample injection needle does not reach the bottom of the sample droplet test tube, controlling the sample injection needle to continue to downwards detect until reaching the bottom of the sample droplet test tube;
when the sample injection needle is positioned at the bottom of the sample droplet test tube, sucking samples through a sample injection hole on the side surface of the sample injection needle; when the sample injection needle is positioned at the bottom of the sample droplet test tube, the sample injection needle can be lifted to a preset position according to preset lifting parameters, and sample suction is performed through a sample injection hole in the bottom surface of the sample injection needle.
Further, the sampled sample droplets are transported to the detection chip through a pipeline by the negative pressure formed by the flow velocity difference, specifically:
The first injector is positioned at the input end of the detection chip and is controlled to input detection oil to the detection chip through a pipeline;
The second injector is positioned at the output end of the detection chip and is controlled to extract the detection oil and the sample droplets from the output end of the detection chip;
the sample droplet is transported to the detection chip through a conduit by a negative pressure created by a difference in flow rate between the first syringe and the second syringe.
Further, before the controlling sample injection is performed on the sample droplet test tube, the method further comprises:
Before controlling the sample injection to perform a needle-down operation on the sample droplet test tube, air is injected from the sample injection needle port by using a power element so that the sample droplet can be separated from the detection oil in the pipeline when the sample droplet is conveyed to a detection chip.
Further, before the sampled sample droplet is transferred to the detection chip through the pipeline, the method further comprises:
Controlling the sampled sample droplet to pass through a bubble sensor so that the bubble sensor detects whether the sampled sample droplet is transmitted to the detection chip or not, and monitoring the sampling condition of the sampled sample droplet in real time;
And adjusting the detection time of the detection chip according to the monitoring condition of the bubble sensor on the sampled sample droplet.
Further, an electromagnetic valve is arranged between the first injector and the detection chip as well as between the second injector and the detection chip; the electromagnetic valve is used for controlling the on-off state of the liquid path and the direction conversion of the pipeline.
Further, the structure of the detection chip specifically includes:
the detection chip comprises a threaded joint and a pipeline; wherein the edge of the pipeline is of a flanging structure;
the pipeline of the detection chip is connected with the detection chip through a threaded joint;
the screwed joint compresses the flanging structure to the detection chip.
Further, an embodiment of the present invention also provides a droplet detection apparatus based on digital PCR, including: the device comprises a control module, a sampling module and a detection module;
The control module is used for controlling the sample injection to perform needle-setting operation on the sample droplet test tube and detecting whether the sample injection needle reaches a preset position;
The sampling module is used for sampling sample droplets in the sample droplet test tube when the sampling needle reaches the preset position;
The detection module is used for transmitting the sampled sample droplets to a detection chip through a pipeline by negative pressure formed by the flow velocity difference so that the detection chip detects the sample droplets.
Further, the control module controls the sample injection to perform needle-setting operation on the sample droplet test tube, and detects whether the sample injection needle reaches a preset position, specifically:
The control module controls the sample injection to perform needle-down operation on the sample droplet test tube, and detects whether the sample injection needle is positioned at the bottom of the sample droplet test tube according to data acquired by the pressure sensor; the pressure sensor is arranged on a sampling arm of the sampling needle;
When the sample injection needle does not reach the bottom of the sample droplet test tube, controlling the sample injection needle to continue to downwards detect until reaching the bottom of the sample droplet test tube;
When the sample injection needle is positioned at the bottom of the sample droplet test tube, sucking samples through a sample injection hole on the side surface of the sample injection needle; when the sample injection needle is positioned at the bottom of the sample droplet test tube, the sample injection needle can be lifted to a preset position according to preset lifting parameters, and then sample suction is performed through a sample injection hole in the bottom surface of the sample injection needle. Further, the detection module is configured to transmit the sampled sample droplet to a detection chip through a pipeline by using a negative pressure formed by the flow velocity difference, specifically:
The first injector is positioned at the input end of the detection chip and is controlled to input detection oil to the detection chip through a pipeline;
The second injector is positioned at the output end of the detection chip and is controlled to extract the detection oil and the sample droplets from the output end of the detection chip;
the sample droplet is transported to the detection chip through a conduit by a negative pressure created by a difference in flow rate between the first syringe and the second syringe.
Compared with the prior art, the droplet detection method and device based on digital PCR have the beneficial effects that: according to the embodiment of the invention, the sample injection is controlled to perform needle-down operation on the sample droplet test tube, the position of the sample injection needle in the sample droplet test tube is detected, when the sample injection needle is in the preset position, the sample droplet is sampled, and the sampled sample droplet is transmitted to the detection chip for detection through the negative pressure formed by the flow velocity difference. By detecting the position of the sample injection needle, sampling is performed again when the sample injection needle is at a preset position, so that a proper distance between the sample injection needle and the test tube is ensured, and a proper amount of sample droplets are taken. The negative pressure formed by the flow velocity difference after sampling directly sucks the sample droplet to the detection chip, so that the sample droplet is ensured to completely enter the detection chip, and the accuracy and the stability of detection can be improved.
In addition, the detection chip of the embodiment of the invention adopts a threaded connection method, and a pipeline flanging technology is added on the basis of a mature cutting sleeve joint sealing technology, so that the tightness of a pipeline and the chip is ensured. The method can ensure that the sealing effect can still be achieved when the size becomes smaller due to the problem of different batches of pipelines. Compared with the traditional glue mode which needs to wait for glue to solidify when detecting the chip installation, all pipelines connected with the chip need to be replaced when being replaced, and meanwhile, compared with the traditional glue mode which needs to wait for glue to solidify well and then debug the instrument, the method has the advantages that the operation simplicity and convenience are effectively improved, and the operation requirement is lower.
Drawings
FIG. 1 is a flow chart of an embodiment of a droplet detection method based on digital PCR according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the workflow of a bubble sensor according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of an embodiment of a droplet detection device based on digital PCR according to an embodiment of the present invention;
Fig. 4 is a schematic structural diagram of a detection chip according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made more apparent and fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
Referring to fig. 1, fig. 1 is a schematic flow chart of an embodiment of a droplet detection method based on digital PCR according to an embodiment of the present invention, as shown in fig. 1, the method includes steps 101 to 103, and the steps are as follows:
step 101: and controlling the sample injection to perform needle-setting operation on the sample droplet test tube, and detecting whether the sample injection needle reaches a preset position.
In the embodiment of the invention, a pressure sensor is arranged on a sampling arm of the sampling needle and used for detecting the position of the sampling needle in the sample droplet test tube, and when the sampling needle reaches the bottom of the sample droplet test tube, the sampling is carried out through a sampling hole on the side surface of the sampling needle. When the sample injection needle is positioned at the bottom of the sample droplet test tube, the sample injection needle can be lifted to a preset position according to preset lifting parameters, and then sample suction is performed through a sample injection hole in the bottom surface of the sample injection needle.
As a preferable scheme of the embodiment of the invention, a movable shaft mechanism is also arranged and connected with the sample injection needle for lifting the sample injection needle to a proper position. When the pressure sensor detects that the sample injection needle is positioned at the bottom of the sample droplet test tube, the sample injection needle is lifted to a lifting parameter distance from the bottom of the test tube according to the set lifting parameter. The lifting parameters are determined based on factors such as the particular sample droplet tube size, the amount of sample droplet aspirated, and the like. In the embodiment of the invention, the movable shaft mechanism controls sample injection to perform needle feeding operation, and after the pressure sensor detects that the sample injection needle reaches the bottom of the test tube, the movable shaft mechanism stops moving downwards, at the moment, the lifting parameter is 1mm, and then the movable shaft mechanism lifts upwards by 1mm again, at the moment, the sample injection needle is 1mm away from the bottom of the test tube. In the action of taking a sample by taking a sample under a sample injection needle, a method of detecting the bottom first by a pressure sensor and then lifting is adopted, so that the distance between the needle opening position and the bottom of the test tube can be adjusted according to corresponding lifting parameters without being too high or too low under the condition that dimensional errors exist in the test tube and a clamp for placing the test tube.
As a preferred embodiment of the present invention, a small volume of air is injected from the needle port of the sample injection needle by the motive element prior to the sample injection needle entering the sample droplet tube for needle insertion. In digital PCR detection, the sample injection needle and the tubing between the sample injection needle and the detection chip are filled with detection oil, and a small section of air is injected into the sample injection needle by using an injector before the sample droplet is sucked by the lower needle, so that the sucked sample droplet is separated from the detection oil between the tubing by a distance.
Step 102: and when the sample injection needle reaches the preset position, sampling the sample droplets in the sample droplet test tube.
When the motion shaft lifts the sample injection needle to a position which is at a distance from the lifting parameter of the bottom of the sample droplet test tube according to the lifting parameter, namely, the sample injection needle is at a preset position, the sample droplet is sucked into a liquid path pipeline of the detection system through the sample injection needle.
Step 103: and transmitting the sampled sample droplets to a detection chip through a pipeline by negative pressure formed by the flow velocity difference so that the detection chip detects the sample droplets.
In the embodiment of the invention, the input end and the output end of the detection chip are respectively provided with one injector, after sampling is completed, the detection oil is input into the detection chip by the injectors at the input end of the detection chip, the detection oil in the detection chip is sucked out by the injectors at the output end of the detection chip, and sample droplets in the pipeline are sucked into the detection chip by negative pressure formed by the flow velocity difference between the two injectors. When the sample droplet is sucked into the detection chip, the optical detection system detects the sample droplet, and the output end injector extracts the detection oil in the detection chip and the detected sample droplet.
As a preferable scheme of the embodiment of the invention, the pipeline in front of the input end injector, the output end injector and the detection chip is respectively provided with an electromagnetic valve for controlling the on-off state of the liquid path in the pipeline and the pipeline reversing. Meanwhile, in the embodiment of the invention, the sample droplets do not need to pass through the electromagnetic valve, so that the risk of damaging the sample droplets due to the existence of a plurality of sharp corner structures in the electromagnetic valve is avoided. In view of the fact that a complete fluid circuit system requires multiple solenoid valves to effect control, as an alternative to embodiments of the present invention, a ten-way valve may be used in place of the solenoid valves.
As a further preferable scheme of the embodiment of the invention, a bubble sensor is arranged in front of the input end of the detection chip and is used for positioning the sample sucking position. Referring to fig. 2, fig. 2 is a schematic workflow diagram of a bubble sensor according to an embodiment of the present invention. Because the sample injection needle and the liquid path pipeline are filled with detection oil, according to the flowing characteristic of the liquid in the pipeline (the central flowing speed of the pipeline is the maximum), part of sample droplets can move in advance relative to the sample main body, and part of samples can enter other pipelines or injectors, so that the part of sample droplets cannot be detected, and the accuracy of PCR detection is affected. The use of a bubble sensor can ensure that a sample droplet is sucked to a designated channel location, independent of sample droplet volume variations, channel flow characteristics, etc. When the bubble sensor detects the first section of air which is injected into the sample injection needle in advance, the bubble sensor starts to judge whether the sample droplet is sucked into the pipeline to-be-detected position or not, monitors the sample injection condition of the sample droplet in real time, and detects the air in the sample injection needle at the moment after the sample droplet injection is completed. When the bubble sensor detects the second section of air, the sample droplet is prompted to enter the detection chip for detection. The detection time can be timely adjusted through monitoring the sample injection condition of the sample droplets by the bubble sensor. If the preset detection sample droplet volume is less than or equal to 50 microliters, the corresponding detection time is 100 seconds, when the situation that the sample droplet is more than 50 microliters occurs, the detection time is 100 seconds, but the sample droplet at the moment does not completely enter the detection chip, so that the bubble sensor does not detect the second section of air yet, at the moment, the mobile terminal receives the detection progress of the bubble sensor, a corresponding instruction is sent to prolong the detection time, and other elements in the pipeline continue to execute the sample droplet detection operation until the bubble sensor detects the second section of air, so that the sample droplet is ensured to completely enter the detection chip for detection. In addition, when the air bubble sensor does not detect the second air segment after the detection time exceeds the specified value, the air bubble sensor can be used as a judging standard of instrument faults, fault detection is carried out on instruments in the droplet detection device, and development of droplet detection work is promoted.
According to the droplet detection method based on digital PCR, the moving shaft is arranged to control the sample injection to perform needle feeding operation on the sample droplet test tube, the pressure sensor is arranged to detect the position of the sample injection needle on the sample droplet test tube, the sample injection needle is lifted to a proper position away from the bottom of the test tube according to the lifting parameter, and then sample suction is performed, so that the problem that sampling is difficult or excessive due to the fact that the distance between the sample injection needle and the bottom of the test tube is too low or too high when dimensional errors exist in the test tube and a clamp for placing the test tube can be avoided. After the sample droplets are absorbed, the sample droplets are directly adsorbed to the detection chip to be detected through negative pressure formed by the flow velocity difference of the injectors at the two ends of the detection chip, so that the sample droplets can be ensured to completely enter the detection chip, and the accuracy and the stability of detection can be improved.
Example 2
Referring to fig. 3, fig. 3 is a schematic structural diagram of an embodiment of a droplet detection device based on digital PCR according to an embodiment of the present invention, including: sample droplet 1, movable axis mechanism 2, pressure sensor 3, sampling arm 4, sample needle 5, bubble sensor 6, detection chip 7, waste liquid bottle 8, first solenoid valve 9, second solenoid valve 10, first syringe 11, second syringe 12 and oil bottle 13.
When the sample droplet 1 is stored in the test tube, any power element is used before the sample injection needle enters the sample droplet storage, in the embodiment of the invention, a small section of air is injected into the needle opening of the sample injection needle by using an injector, so that the sample droplet can not be mixed with the detection oil in the sample injection needle to be separated by a certain distance when the sample injection needle sucks samples. After air is injected, the sample injection needle 5 is controlled to enter the sample droplet test tube through the movable shaft mechanism 2, the pressure sensor 3 is arranged on the sampling arm 4 connected with the sample injection needle 5 and used for detecting the position of the sample injection needle 5 in the sample droplet test tube, when the sample injection needle 5 is positioned at the bottom of the sample droplet test tube, the pressure sensor 3 gives out a prompt, at the moment, the movable shaft mechanism 2 stops moving downwards, and the sample injection needle 5 is lifted to a distance from the lifting parameter of the bottom of the sample droplet test tube according to the lifting parameter provided by the background, namely, a preset position suitable for sampling.
When the sample injection needle 5 is in the preset position, the sucking of the sample droplet 1 into the channel through the sample injection needle 5 is started. After the sample droplet 1 is sucked, the first electromagnetic valve 9 and the second electromagnetic valve 10 are opened, the first injector 11 injects the detection oil to the input end of the detection chip, and the detection oil is stored in the oil bottle 13. At the same time, the second syringe 12 starts to draw the detection oil at the output end of the detection chip, and the sample droplet in the pipeline is sucked into the detection chip for detection by the negative pressure formed by the flow velocity difference between the first syringe 11 and the second syringe 12. When the detection is started, the second syringe 12 draws out the sample droplet and the detection oil from the detection chip, and transfers the waste liquid generated in the detection process to the waste liquid bottle 8. As an alternative to embodiments of the present invention, a ten-way valve may be used instead of a solenoid valve, reducing the complexity of the instrument structure and the failure rate.
In the embodiment of the invention, a bubble sensor 6 is further arranged in front of the input end of the detection chip and used for positioning the sample sucking position, so that the sample droplet 1 can be sucked to a designated pipeline position, and the influence of the volume change of the sample droplet, the pipeline flow characteristic and the like is avoided.
As a preferred embodiment of the present invention, the detection chip 7 is screwed with the pipeline. Referring to fig. 4, fig. 4 is a schematic structural diagram of a detection chip according to an embodiment of the present invention, where the detection chip includes a chip fixture 1, a threaded joint 2, and a pipeline 3. The chip clamp 1 is used for placing a detection chip and plays a role in protection. The edge of the pipeline 3 is also provided with a flanging structure, and the threaded joint 2 compresses the flanging structure of the pipeline 3 on the detection chip, so that the sealing connection between the detection chip and the pipeline is realized. The method for detecting the connection between the chip and the pipeline adopts the technology of adding the pipeline flanging on the basis of the current mature cutting sleeve joint sealing technology, and the technology are combined to further improve the sealing property of the connection between the pipeline and the chip.
The more detailed working principle and the flow of steps of the droplet detecting device of this embodiment can be, but not limited to, those described in embodiment 1.
According to the droplet detection device based on digital PCR, a detection chip adopts a threaded connection method, and a pipeline flanging technology is added on the basis of a mature ferrule joint sealing technology, so that the tightness of a pipeline and the chip is ensured. The method can ensure that the sealing effect can still be achieved when the size becomes smaller due to the problem of different batches of pipelines. Compared with the traditional glue mode which needs to wait for glue to solidify when detecting the chip installation, all pipelines connected with the chip need to be replaced when being replaced, and meanwhile, compared with the traditional glue mode which needs to wait for glue to solidify well and then debug the instrument, the method can effectively improve the operation simplicity and has lower operation requirement.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and substitutions can be made by those skilled in the art without departing from the technical principles of the present invention, and these modifications and substitutions should also be considered as being within the scope of the present invention.
Claims (6)
1. A method of droplet detection based on digital PCR, comprising:
Controlling sample injection to perform needle-setting operation on a sample droplet test tube, and detecting whether the sample injection needle reaches a preset position; wherein the sample introduction is controlled to perform a needle-down operation on the sample droplet test tube; when the sample injection needle does not reach the bottom of the sample droplet test tube, controlling the sample injection needle to continue to downwards detect until reaching the bottom of the sample droplet test tube;
Sampling the sample droplets in the sample droplet test tube when the sample injection needle reaches the preset position; detecting whether the sample injection needle is positioned at the bottom of the sample droplet test tube according to data acquired by the pressure sensor; the pressure sensor is arranged on a sampling arm of the sampling needle; when the sample injection needle is positioned at the bottom of the sample droplet test tube, lifting the sample injection needle to the preset position according to preset lifting parameters, and sucking samples through a sample injection hole in the bottom surface of the sample injection needle;
A first injector is arranged at the input end of the detection chip, a second injector is arranged at the output end of the detection chip, and the sample droplets are transmitted to the detection chip through the pipeline by virtue of negative pressure formed by the flow velocity difference between the first injector and the second injector so as to be detected by the detection chip; the first injector is positioned at the input end of the detection chip and is controlled to input detection oil to the detection chip through a pipeline; the second injector is positioned at the output end of the detection chip and is controlled to extract the detection oil and the sample droplets from the output end of the detection chip.
2. The digital PCR-based droplet detection method of claim 1, wherein prior to controlling the sample injection to needle the sample droplet tube, further comprising:
Before controlling the sample injection to perform a needle-down operation on the sample droplet test tube, air is injected from the sample injection needle port by using a power element so as to separate the sample droplet from the detection oil in the pipeline when the sample droplet is conveyed to a detection chip.
3. The method of claim 1, wherein prior to transferring the sampled sample droplets to the detection chip via the pipeline, further comprising:
Controlling the sampled sample droplet to pass through a bubble sensor so that the bubble sensor detects whether the sampled sample droplet is transmitted to the detection chip or not, and monitoring the sampling condition of the sampled sample droplet in real time;
And adjusting the detection time of the detection chip according to the monitoring condition of the bubble sensor on the sampled sample droplet.
4. The method for detecting droplets based on digital PCR according to claim 1, wherein a solenoid valve is provided between each of the first syringe and the second syringe and the detection chip; the electromagnetic valve is used for controlling the on-off state of the liquid path and the direction conversion of the pipeline.
5. The method for detecting droplets based on digital PCR according to any one of claims 1 to 4, wherein the detection chip has a structure comprising:
the detection chip comprises a threaded joint and a pipeline; wherein the edge of the pipeline is of a flanging structure;
the pipeline of the detection chip is connected with the detection chip through a threaded joint;
the screwed joint compresses the flanging structure to the detection chip.
6. A digital PCR-based droplet detection device, comprising: the device comprises a control module, a sampling module and a detection module;
the control module is used for controlling the sample injection to perform needle-setting operation on the sample droplet test tube and detecting whether the sample injection needle reaches a preset position; wherein the sample introduction is controlled to perform a needle-down operation on the sample droplet test tube; when the sample injection needle does not reach the bottom of the sample droplet test tube, controlling the sample injection needle to continue to downwards detect until reaching the bottom of the sample droplet test tube;
The sampling module is used for sampling sample droplets in the sample droplet test tube when the sampling needle reaches the preset position; detecting whether the sample injection needle is positioned at the bottom of the sample droplet test tube according to data acquired by the pressure sensor; the pressure sensor is arranged on a sampling arm of the sampling needle; when the sample injection needle is positioned at the bottom of the sample droplet test tube, lifting the sample injection needle to the preset position according to preset lifting parameters, and sucking samples through a sample injection hole in the bottom surface of the sample injection needle;
The detection module is used for arranging a first injector at the input end of the detection chip, arranging a second injector at the output end of the detection chip, and transmitting the sample droplet to the detection chip through the pipeline by virtue of negative pressure formed by the flow velocity difference between the first injector and the second injector so as to enable the detection chip to detect the sample droplet; the first injector is positioned at the input end of the detection chip and is controlled to input detection oil to the detection chip through a pipeline; the second injector is positioned at the output end of the detection chip and is controlled to extract the detection oil and the sample droplets from the output end of the detection chip.
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