Method for controlling pipetting of a gas pressure pipetting pump and use thereof

Abstract

This invention relates to a pipetting control method for a pneumatic pipetting pump, belonging to the technical field of automated pipetting equipment. The pipetting control method includes a liquid level detection step, which comprises: S1: activating a real-time pneumatic pressure acquisition system to acquire the pneumatic pressure value inside the pipetting pump piston cylinder; S2: controlling the pipetting pump to move towards the liquid surface, simultaneously controlling the piston in the pipetting pump to also move towards the liquid surface at a predetermined speed, causing the piston cylinder to generate a continuous outward airflow; S3: when the pneumatic pressure sensor in the pipetting pump detects a change in the amplitude of the pneumatic pressure waveform greater than a preset liquid level trigger threshold, it is determined that contact with and detection of the liquid surface has occurred. This control method is based on pneumatic pressure feedback control of the pipetting process, which can flexibly identify the liquid level and accurately obtain the position information of the liquid object. Compared with conventional pneumatic detection, this invention has the advantages of fast pneumatic detection response speed, high pneumatic detection sensitivity, and high flexibility of adjustment.

Description

Technical Field

[0001] This invention relates to the field of automated pipetting equipment technology, and in particular to a pipetting control method and application of a pneumatic pipetting pump. Background Technology

[0002] With the rapid development of science and technology, pipetting work has become routine in laboratories of biology, chemistry, environment, pharmaceutical research and development, food, and other units such as hospitals, disease control centers, and blood banks. Faced with more complex research objects and an increasing number of samples, automated pipetting systems (or pipetting workstations) have gradually become more and more popular in the market. The pipetting transfer position and the quality of the pipetting process in the pipetting workstation determine the accuracy of pipetting and the timeliness of the experiment. Among them, the pneumatic liquid level detection and pipetting process quality monitoring system is the most important part of the pipetting equipment. It is a highly efficient, somewhat complex, and stable and accurate methodology system.

[0003] However, due to technological limitations, traditional fixed-level pipetting methods require the pipetting operation to be performed completely below the liquid level in a fixed or unknown location. This results in liquid mass loss and inaccurate actual liquid volume transfer, affecting the accuracy of the experiment.

[0004] Building upon this foundation, various technologies have been employed for liquid level detection during pipetting. For example, CN112473760A discloses a pneumatic liquid level detection method and device using a blow-suction method, which utilizes changes in air pressure at the contact surface to detect the liquid level position. CN215087261U also discloses a pneumatic pipette that accurately determines whether the pipette tip is in contact with the liquid surface by detecting the air pressure inside the cylinder and comparing the pressure difference. This avoids the problems of repeated blowing and sucking that cause accidental liquid aspiration and contamination, the need to vent the gas from the cylinder after sucking, and blowing reagents out of the test tube during blowing, all problems encountered in existing technologies.

[0005] However, all of the above solutions have problems such as the gas pressure only changing slowly when they come into contact with the liquid surface or even when they are immersed in the cavity below the liquid surface, and the gas pressure change in the cavity is slow to react, which will result in a long detection time.

[0006] To rapidly and sensitively detect the liquid level, a pipette pump, as disclosed in CN115069322A, employs a dual detection system—a pressure detection system and a capacitance detection system—to determine if the conductive pipette tip has reached the liquid level by contacting the solution to be sampled and generating a capacitance signal. However, this type of pipette pump requires a conductive pipette tip, significantly increasing consumable costs. Furthermore, the capacitance detection system is susceptible to interference from ambient magnetic fields, affecting its stability and precision, thus hindering the widespread adoption of this technology. Summary of the Invention

[0007] Therefore, it is necessary to provide a pneumatic pipetting pump control method to address the problems of low detection accuracy, certain delay, or high cost of the aforementioned automatic pipetting equipment. This control method is based on pneumatic feedback control of the pipetting process, which can flexibly identify the liquid level and accurately obtain the position information of the liquid object. Compared with conventional pneumatic detection, this invention has the advantages of fast detection response speed, high detection sensitivity, and high flexibility.

[0008] A method for controlling the pipetting of a pneumatic pipetting pump includes a liquid level detection step, wherein the liquid level detection step includes:

[0009] S1: Start the real-time air pressure acquisition system to collect the air pressure value inside the piston cylinder of the pipette pump;

[0010] S2: Control the pipette pump to move towards the liquid surface, and at the same time control the piston in the pipette pump to move towards the liquid surface at a predetermined speed, so that the piston cylinder generates a continuous outward airflow;

[0011] S3: When the difference in the amplitude of the gas pressure waveform collected by the gas pressure sensor in the pipette pump is greater than the preset liquid surface trigger threshold, it is determined that the liquid surface has been contacted and detected.

[0012] In their preliminary research, the inventors discovered that conventional techniques for detecting liquid levels using air pressure require the nozzle to contact the liquid surface, or even be submerged below it, for the air pressure within the piston cylinder to gradually change. Furthermore, the response to pressure changes within the cylinder is sluggish, resulting in a long detection time. This also increases the difficulty in designing the length of the air guide tube connecting the pressure sensor and the piston cylinder, as a longer tube leads to a slower response and less accurate liquid level readings. Additionally, the requirement of submersion to detect the liquid level means the nozzle may become contaminated with liquid during the detection process, potentially causing contamination and liquid waste in subsequent processes.

[0013] The pneumatic pipetting pump control method of the present invention controls the movement of the pipetting pump toward the liquid surface while simultaneously controlling the piston in the pipetting pump to move toward the liquid surface at a predetermined speed. This generates a continuous outward (facing the liquid surface) airflow within the piston cylinder. Therefore, when the pipetting pump tip is away from the liquid surface, the presence of the liquid surface does not affect the airflow, and the air pressure within the piston cylinder remains almost constant. When the tip of the pipetting pump touches the liquid surface, the downward airflow is instantly blocked, thereby forming a reverse air pressure. This accelerates the air pressure sensor to detect that the original air pressure environment has changed, and instantly determines that the liquid surface has been detected.

[0014] This method is highly sensitive to changes in air pressure, recognizing liquid surfaces upon contact without requiring immersion to a specific depth. It also overcomes the design limitations of considering the length of the air delivery tube. Furthermore, practical applications have shown that it has lower requirements for airflow size and speed; for example, controlling the piston at a slow speed of 2 mm / s is sufficient for sensitive liquid surface detection. Unlike pneumatic liquid level detection methods using blow-suction, this control method does not require fixed amplitude and frequency, relying solely on a specific positive correlation characteristic of acceleration to enhance sensitivity. Moreover, it determines whether contact with the liquid surface using the change in air pressure—the difference before and after—rather than a specific absolute value. Considering that air pressure often changes dynamically in different environments, this control method monitors the difference before and after the change, eliminating the need to consider pressure peaks or troughs. This significantly reduces the risk of misjudgment due to environmental interference, demonstrating the stability of the detection method and resulting in more accurate liquid surface detection.

[0015] In one embodiment, in step S2, the piston in the pipette pump is first moved upward a preset distance, and then moved towards the liquid surface at a predetermined speed. Moving the piston upward a certain distance before downward helps to create a stable outward airflow. Upon contact with the liquid surface, a reverse (inward) airflow is quickly formed, improving the reaction time for liquid surface detection. The large pressure difference at the moment of contact with the liquid surface improves the accuracy and stability of liquid surface detection and judgment, and prevents accidental contact with the liquid surface. After detecting the liquid surface, the piston quickly returns to its original position.

[0016] In one embodiment, in step S2, the starting position of the pipette pump is taken as the origin, the distance between the contact position of the liquid surface detected by the pipette pump and the origin is taken as the descent height, the depth of the liquid to be pipetted is calculated by the distance between the bottom of the container holding the liquid to be pipetted and the origin, and the volume of the liquid to be pipetted is calculated by combining the container shape.

[0017] Using the above method, it is possible to identify whether the remaining capacity of the container meets the target transfer requirements. The liquid depth is determined by comparing the obtained descent height with the pre-obtained distance between the container bottom and the origin. This, combined with the container shape, allows for the calculation of the remaining volume, identifying whether the liquid volume is sufficient or insufficient. This overcomes the problem of empty detection or empty suction when only a small sample size is available. For example, using a cylindrical container with radius r, the remaining liquid capacity V = πr²x, where x = distance between the container bottom and the origin - descent height.

[0018] In one embodiment, in step S3, the air pressure waveform amplitude undergoes the following filtering process: air pressure values ​​are collected at predetermined time points. After collecting air pressure values ​​at several time points, they are sorted according to their magnitude. The top and bottom air pressure values ​​are removed, and the remaining air pressure values ​​are averaged to determine the difference in the change of air pressure waveform amplitude. In the above filtering process, the extreme values ​​at the beginning and end of the sorted values ​​are removed to overcome the random interference inherent in the arithmetic mean filtering method. This filtering method is simple and efficient, making the judgment value more reliable and stable, and avoiding the risk of misjudgment.

[0019] In one embodiment, in step S3, the air pressure waveform amplitude is filtered as follows: air pressure values ​​are collected at time points of 100±20μs. After collecting air pressure values ​​at 30±10 time points, they are sorted according to their magnitude. The air pressure values ​​at the top and bottom 5±3 are removed, and the remaining air pressure values ​​are averaged to determine the difference in the change of air pressure waveform amplitude.

[0020] In one embodiment, the liquid surface trigger threshold is set according to the percentage change rate of the air pressure waveform amplitude collected by the air pressure sensor from the reference amplitude (base value before liquid absorption). When the percentage change difference is greater than the preset liquid surface trigger threshold, it is determined that the liquid surface has been contacted.

[0021] In one embodiment, the pipetting control method of the pneumatic pipetting pump further includes a liquid aspiration step, the liquid aspiration step comprising:

[0022] S4: Controls the piston in the pipette pump to draw liquid, and simultaneously controls the pipette pump to move downwards as the liquid level drops, so that the pipette tip remains immersed in the liquid at a preset depth.

[0023] By using the liquid level following method described above, the liquid nozzle is moved during the liquid aspiration process to always maintain a certain height of immersion in the liquid surface and follow the liquid level as it descends. The liquid level following function solves the problems caused by empty aspiration or excessive insertion of the nozzle into the liquid surface at a fixed liquid level aspiration height.

[0024] In one embodiment, the pipetting control method of the pneumatic pipetting pump further includes a pipetting quality monitoring step, which is performed concurrently with the aspiration step, and includes: aspiration air monitoring, bubble monitoring and blockage monitoring;

[0025] The vacuum monitoring includes the following steps: comparing the real-time collected air pressure waveform with the preset normal pipetting waveform; when the difference in the change of the air pressure waveform amplitude during the aspiration process is less than the difference in the change of the preset vacuum waveform amplitude, it is determined to be vacuum.

[0026] The blockage monitoring includes the following steps: comparing the real-time collected air pressure waveform with the preset normal pipetting waveform; when the change amplitude of the air pressure waveform is greater than the difference between the preset normal waveform and the pressure remains low during the aspiration process, it is determined to be a blockage.

[0027] The bubble monitoring includes the following steps: comparing the real-time collected air pressure waveform with the preset normal pipetting waveform; when the change amplitude of the air pressure waveform during the aspiration process is between the difference between the preset normal waveform change amplitude and the preset aspiration waveform change amplitude, it is determined that a bubble is aspirated.

[0028] The difference in the amplitude of the normal waveform change is greater than the difference in the amplitude of the suction waveform change.

[0029] Understandably, the normal pipetting waveform and the aspiration waveform can be determined through prior experiments. By observing the different changes in air pressure, it is possible to detect in real time whether aspiration, air bubbles, or blockages occur during the pipetting process, thereby achieving intelligent monitoring and unattended automated operation.

[0030] In one embodiment, after the liquid aspiration step is completed, a droplet prevention step is further included, which includes:

[0031] S5: Real-time monitoring of the collected air pressure value, using the air pressure value at the time of liquid aspiration as the initial value for preventing liquid from falling. When the amplitude of the air pressure value waveform changes beyond the threshold, the control piston moves upward to aspirate the liquid back, so that the air pressure value returns to the initial value range for preventing liquid from falling.

[0032] In conventional techniques, after pipetting, the liquid is typically drawn upwards a small distance, removing some air and retaining it at the tip of the pipette tip to prevent dripping. However, depending on the application and airtightness, such as when the pump remains stationary in space for a long time after drawing liquid, or when airtightness is poor, dripping can occur again. Furthermore, conventional pipetting devices generally suffer from airtightness issues; even using the same pipette tip can result in inconsistent airtightness, making it difficult to set a fixed small stroke. To address this problem, the aforementioned anti-drip method utilizes the phenomenon that changes in air pressure positively correlate with the airtightness of the pipetting device itself, and employs cyclic detection to achieve cyclic compensation, ultimately maintaining a drip-free state.

[0033] It is understandable that fields such as biology and medicine require high precision in droplet control. When aspirating and then dispensing, the volume of the droplets may reach the level of 1 μl. Therefore, depending on the actual application scenario, such as 1000 μl, 200 μl, 10 μl, and different specifications of pipette tips, the volume and weight of the droplets formed will also vary greatly. Fixed stroke compensation is not suitable. The above method can flexibly preset different threshold values ​​corresponding to different changes according to the actual application scenario and set them according to the relative proportion of the initial value. This can achieve the purpose of preventing droplets from falling and accurately controlling the pipetting.

[0034] At the same time, a basic threshold is set so that compensation is only performed when the value exceeds the preset threshold, which avoids the pump performing compensation actions too frequently and extends the service life of the equipment.

[0035] The pneumatic pipetting pump's pipetting control method further includes a dispensing step, which comprises:

[0036] S6: Controls the piston in the pipette pump to dispense liquid, and simultaneously controls the pipette pump to move upward as the liquid level rises, so that the pipette tip remains within a preset distance from the liquid level.

[0037] By using the liquid level following method described above, the liquid nozzle is moved during the liquid aspiration process to always maintain a certain height above the liquid level and rise with the liquid level, thus solving the problem that the liquid easily sticks to the outer wall of the nozzle during the liquid separation process, resulting in inaccurate results.

[0038] The present invention also discloses a pneumatic pipetting pump, comprising: a pipetting pump assembly and a pipetting control system, wherein the pipetting control system performs pipetting operations using the control method described above.

[0039] In one embodiment, the pipette pump assembly includes a pipette pump, a drive unit, and a position sensing device. After analyzing and judging the gas pressure value inside the piston cylinder of the pipette pump collected by the pipette control system, the system issues a command to control the drive unit to drive the pipette pump and the piston therein to move. When the pipette pump is in the starting position, the position sensing device is triggered and sends a signal.

[0040] Understandably, the specific structure of the aforementioned pneumatic pipetting pump can be achieved using any conventional pneumatic pipetting equipment, as long as it can ensure real-time monitoring of the air pressure inside the piston chamber and coordinated control of the pump's lifting and lowering and piston movement to complete the suction and blowing functions.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention discloses a pneumatic pipetting pump control method, which is based on pneumatic liquid level detection. It can flexibly identify the liquid level and accurately obtain the liquid level position information, and has the characteristics of fast liquid level detection response speed and high pneumatic detection sensitivity.

[0043] Compared to capacitive level detection, pneumatic level detection is characterized by its low cost. It does not require the pipetting tip to be conductive and can be used with materials that are either conductive or non-conductive, which greatly reduces the cost of consumables.

[0044] Furthermore, this invention can be based on pneumatic detection and integrated with a pipetting quality monitoring system to form a complete system covering the entire pipetting process from start to finish, ensuring the accuracy of pipetting position and quality. This pipetting quality monitoring method can identify pipetting process malfunctions and interferences, including identifying pipetting aspiration interference, air bubble interference, and blockage interference, and can also prevent cross-contamination or interference during pipetting through a droplet anti-drip process. Attached Figure Description

[0045] Figure 1 This is a flowchart of the pipetting control method for a pneumatic pipetting pump.

[0046] Figure 2 A schematic diagram of a normal pipetting waveform obtained for monitoring gas pressure.

[0047] Figure 3 This is a flowchart of the liquid level detection process.

[0048] Figure 4 This is a flowchart of the pipetting quality monitoring workflow.

[0049] Figure 5 This is a schematic diagram of the air pressure waveforms collected under different conditions.

[0050] Figure 6 This is a flowchart illustrating the process for preventing droplets from falling.

[0051] Figure 7 This is a schematic diagram of the air pressure waveform during the droplet anti-fall control process. Detailed Implementation

[0052] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0053] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0054] Example

[0055] A method for controlling the pipetting of a pneumatic pipetting pump, the process of which is as follows: Figure 1 As shown, the process includes steps such as liquid level detection, liquid aspiration, droplet prevention, and liquid separation. The liquid aspiration process is accompanied by liquid quality monitoring to improve the accuracy and stability of liquid transfer and reduce the risks of contamination, liquid transfer errors, and failures.

[0056] It is understandable that the pipetting control method of the pneumatic pipetting pump in this embodiment can be implemented by relying on a device including a pipetting pump assembly and a pipetting control system. It only requires that the pipetting pump assembly includes a pipetting pump, a drive device and a position sensing device, that the pipetting control system can collect the air pressure value in the piston cylinder of the pipetting pump, and that the drive device can drive the pipetting pump and the piston therein to move according to the instructions of the pipetting control system.

[0057] For a normal pipetting process, the monitored normal pipetting waveform curve is as follows: Figure 2 As shown, the line segment marked 1 represents the pre-pipette stage, and A is the starting point for liquid level detection; the line segment marked 2 represents the liquid level detection process; B is the completion point of liquid level detection; C is the starting point for liquid transfer (liquid aspiration), and the starting point for monitoring air bubbles, aspiration voids, and blockages; the line segment marked 3 represents the liquid aspiration process, during which liquid aspiration operations are performed and liquid level quality monitoring operations are conducted; D is the completion point for liquid transfer, and the end point for monitoring air bubbles, aspiration voids, and blockages; E is the starting point for monitoring the droplet prevention process; and the line segment marked 4 represents the holding process after liquid transfer, during which droplet prevention operations are performed.

[0058] The pipetting control method of the present invention will be described below with reference to a specific application scenario. However, it is understood that the following process flow can be flexibly adjusted according to equipment requirements and testing conditions.

[0059] First, liquid level detection is performed; the workflow is as follows: Figure 3 As shown.

[0060] S1: Start the real-time air pressure acquisition system to collect the air pressure value inside the piston cylinder of the pipette pump.

[0061] When the equipment is started and the pipetting process is performed, the gas pressure acquisition chip built into the pipetting pump is initialized and the liquid level detection parameters are adapted. At the same time, the software obtains the current gas pressure value as the benchmark value for analysis and judgment such as suction monitoring, bubble monitoring, and blockage monitoring during the pipetting process, and keeps this acquisition system monitoring the gas pressure value in the piston cylinder of the pipetting pump in real time.

[0062] In this embodiment, the parameters for parameter adaptation are: the maximum stroke and speed of the pipette pump in the vertical direction, the liquid surface trigger threshold for detecting the liquid surface, the liquid surface detection sensitivity, and the liquid surface following speed.

[0063] Understandably, liquid surface detection sensitivity refers to the speed of reaction when contacting the liquid surface during detection. It is the magnitude of pressure change when contacting the liquid surface under the same environment and method. This can be achieved by setting and adjusting the gain parameter of the pressure sensor, which can be adjusted to 1x, 2x, 4x, and 16x. For example, if the initial pressure is 1000, under sensitivity A (1x gain), a pressure change from 1000 to 1200 indicates a liquid surface has been detected. Under sensitivity B (2x gain), a pressure change from 1000 to 1400 indicates a liquid surface has been detected.

[0064] S2: Control the pipette pump to move towards the liquid surface (i.e. downwards), and at the same time control the piston in the pipette pump to move towards the liquid surface at a predetermined speed, so that the piston cylinder generates a continuous outward airflow.

[0065] To create a stable outward airflow and improve the accuracy and stability of liquid level detection, in this embodiment, the piston in the pipette pump is first moved upward a certain distance (e.g., 30mm), and then moved towards the liquid surface at a predetermined speed.

[0066] Understandably, this stroke can be defined according to the time requirements of the detection. For example, if the function of liquid level detection is required to be completed within 3 seconds, the piston movement time should be greater than 3 seconds. Taking a movement speed of 2mm / s as an example, the upward movement distance should be greater than 6mm, because the movement speed of this stroke can be relatively fast. In this embodiment, it can move directly 30mm.

[0067] The above operation controls the pipette pump to move towards the liquid surface while simultaneously controlling the piston in the pipette pump to move towards the liquid surface at a predetermined speed. This causes the piston cylinder to generate a continuous outward airflow. Therefore, when the pipette tip is away from the liquid surface, the presence of the liquid surface does not affect the airflow, and the air pressure in the piston cylinder remains almost constant. When the tip of the pipette tip contacts the liquid surface, the downward airflow is instantly blocked, thus forming a reverse air pressure. This accelerates the air pressure sensor to detect that the original air pressure environment has changed, and instantly determines that the liquid surface has been detected.

[0068] Furthermore, in this embodiment, to avoid the problem of empty detection or suction when there are only a few samples, a position sensing device such as a photoelectric switch can be used to record and locate the starting position of the pipette pump. The starting position of the pipette pump is taken as the origin, and the distance between the contact position of the liquid surface detected by the pipette pump and the origin is taken as the descent height. The depth of the liquid to be pipetted is calculated by the distance between the bottom of the container holding the liquid to be pipetted and the origin. The volume of the liquid to be pipetted is calculated by combining the shape of the container.

[0069] For example, when the equipment starts up and a pipetting process is performed, the pipetting pump is first controlled to return to its starting position. A photoelectric switch is installed at this starting position to detect and determine the starting position of the pipetting pump, and this starting position is defined as the origin position. It is understandable that this return-to-start-position operation can be confirmed by combining multiple pipetting pump assembly modules and individual pipetting pump control, and appropriate photoelectric switches and other components can be set as needed.

[0070] Using the above method, it is possible to determine whether the remaining capacity of the container meets the target transfer requirements. By comparing the obtained descent height with the pre-obtained distance between the bottom of the container and the origin, and combining this with the container shape, the remaining volume can be calculated to determine whether the liquid volume is sufficient or insufficient. For example, using a cylindrical container with radius r, the remaining liquid capacity V = πr²x, where x = distance between the bottom of the container and the origin - descent height.

[0071] S3: When the difference in the amplitude of the gas pressure waveform collected by the gas pressure sensor in the pipette pump is greater than the preset liquid surface trigger threshold, it is determined that the liquid surface has been contacted and detected, and the pipette pump piston is controlled to reset (i.e., return to the initial position of the piston, ready to start the pipetting operation according to the predetermined pipetting volume).

[0072] The aforementioned liquid surface trigger threshold is set based on the percentage change rate of the air pressure waveform amplitude collected by the air pressure sensor relative to the reference amplitude. When the percentage change difference is greater than the preset liquid surface trigger threshold, it is determined that the liquid surface has been touched.

[0073] In this embodiment, the above-mentioned air pressure waveform amplitude undergoes the following filtering process: air pressure values ​​are collected at 100μs intervals, resulting in 30 time points. These values ​​are then sorted according to their magnitude, and the top and bottom five values ​​are removed. The remaining values ​​are then averaged to determine the difference in the air pressure waveform amplitude. In this filtering process, the first and last extreme values ​​are removed after sorting to overcome the random interference inherent in the arithmetic mean filtering method. This filtering method is simple and efficient, making the judgment value more reliable and stable, and avoiding the risk of misjudgment.

[0074] The aforementioned pneumatic liquid level detection method determines whether the liquid surface has been touched by using the percentage rate of change of air pressure on a reference, rather than by using a fixed air pressure change value. This overcomes the problem of misjudgment caused by the inapplicability of air pressure values ​​due to external factors such as atmospheric pressure environment and temperature environment, and greatly enhances the stability of air pressure detection.

[0075] S4: Controls the piston in the pipette pump to draw liquid, and simultaneously controls the pipette pump to move downwards as the liquid level drops, so that the pipette tip remains immersed in the liquid at a preset depth.

[0076] By using the liquid level following method described above, the liquid nozzle is moved during the liquid aspiration process to always maintain a certain height of immersion in the liquid surface and follow the liquid level as it descends. The liquid level following function solves the problems caused by empty aspiration or excessive insertion of the nozzle into the liquid surface at a fixed liquid level aspiration height.

[0077] S4': Along with the above aspiration steps, a pipetting quality monitoring step is performed. The pipetting quality monitoring step includes: aspiration void monitoring, air bubble monitoring, and blockage monitoring, in order to achieve the purpose of automatically judging and monitoring the quality of the pipetting process in an unattended program.

[0078] Pipette quality monitoring workflow as follows Figure 4 As shown.

[0079] 1) Vacuum monitoring: The real-time collected air pressure waveform is compared with the preset normal pipetting waveform. When the difference in the change of air pressure waveform amplitude during the aspiration process is less than the difference in the change of preset vacuum waveform amplitude, it is determined to be vacuum.

[0080] 2) Blockage monitoring: The real-time collected air pressure waveform is compared with the preset normal pipetting waveform. When the change in air pressure waveform during the aspiration process is greater than the difference between the preset normal waveform and the waveform remains in a low-pressure state, it is determined to be a blockage.

[0081] 3) Bubble monitoring: The real-time collected air pressure waveform is compared with the preset normal pipetting waveform. When the change amplitude of the air pressure waveform during the aspiration process is between the difference between the preset normal waveform change amplitude and the preset aspiration waveform change amplitude, it is determined that a bubble is aspirated.

[0082] The difference in amplitude of the above-mentioned normal waveform is greater than the difference in amplitude of the vacuuming waveform.

[0083] The monitoring principle described above is as follows: before the pipette pump draws liquid, the pipeline is connected to the atmosphere, and a specific atmospheric pressure value is maintained in the air pressure closed pipeline. If air is drawn in, the original air pressure changes only slightly and remains basically unchanged, and the difference in the amplitude of the air pressure waveform approaches zero. If air bubbles are drawn in, the difference in the amplitude of the air pressure waveform is small, that is, the change range is between the preset difference in the amplitude of the normal waveform and the preset difference in the amplitude of the air-drawn waveform. If a blockage occurs in the pipette tip, the pressure value drops sharply, and the sensor will be able to detect this abnormality.

[0084] Understandably, when the pipette pump is performing a dispensing operation, a specific positive pressure value is maintained in the air pressure closed line. If a clot occurs and blocks the pipette tip, the pressure value will rise sharply, and this abnormal change can also be detected by the module.

[0085] In this embodiment, the normal pipetting waveform and the aspiration waveform are determined through prior experiments. By observing the different changes in air pressure, it is possible to detect in real time whether aspiration, air bubbles, or blockages occur during the pipetting process.

[0086] like Figure 5 The figures show the gas pressure waveforms collected under different conditions: vacuum aspiration, bubble aspiration, blockage, and normal pipetting. As can be seen from the figures, when bubbles are aspirated, the gas pressure waveform amplitude is small due to the small amount of gas absorbed. When cavitation occurs, the gas pressure waveform amplitude changes only slightly, unlike the slight change in pressure after bubble aspiration. When blockage occurs, the negative pressure created by suction cannot be replenished with liquid in time, resulting in a sharp drop in the gas pressure waveform amplitude, which remains at a low pressure for a prolonged period. Therefore, by observing the different changes in gas pressure, it is possible to detect in real time whether accidents such as vacuum aspiration, bubbles, or blockage have occurred during pipetting.

[0087] S5: Real-time monitoring of the acquired air pressure value, using the air pressure value at the time of liquid aspiration as the initial value for drop prevention. When the amplitude of the air pressure waveform exceeds a threshold, the piston is controlled to move upward, drawing back the liquid and restoring the air pressure value to the initial range. The workflow of this droplet prevention step is as follows: Figure 6 As shown.

[0088] In conventional techniques, after pipetting, the liquid is typically drawn upwards a small distance, removing some air and retaining it at the tip of the pipette tip. This is a method to prevent dripping. However, depending on the application and airtightness, such as when the pump remains stationary in space for a long time after drawing liquid, or when airtightness is poor, dripping can occur again. Furthermore, conventional pipetting devices generally suffer from poor airtightness, and even when using the same pipette tip, inconsistent airtightness can occur. To address this issue, the aforementioned anti-drip method utilizes the characteristic that changes in air pressure positively reflect the airtightness of the pipetting device itself. It employs cyclic detection to achieve cyclic compensation, ultimately maintaining a drip-free state. This effectively solves the problem of cross-contamination during liquid transfer in laboratories in biological, chemical, environmental, pharmaceutical research and development, food industries, as well as in hospitals, disease control centers, blood banks, and other institutions.

[0089] Considering that fields such as biology and medicine require high precision in droplet control, and the volume of liquid to be controlled at the 1μl level may be achieved when dispensing after aspiration, pipette tips of different specifications with large differences in 1000μl, 200μl, and 10μl will produce droplets with large differences in volume and weight, making fixed stroke compensation unsuitable.

[0090] In this embodiment, after the liquid is collected and sucked into the pipette tip by the piston pump, the air pressure acquisition sensor monitors the percentage change in the amplitude of the air pressure waveform in the piston cylinder. When the air pressure waveform changes, the program's adaptive algorithm controls the pump motor to drive the piston to move vertically upward a certain distance, driving the liquid to be drawn back a certain volume, so that the liquid in the pipette tip remains in its original position, preventing droplets from falling. This solves the problems of pipetting accuracy deviation and cross-contamination caused by droplets falling during the pipetting process, whether the pipetting is static or dynamic. The air pressure waveform diagram is shown below. Figure 7 As shown, points 1, 3, and 5 indicate detected changes in air pressure, while points 2, 4, and 6 indicate droplet compensation operations.

[0091] The above method flexibly presets different threshold values ​​for different changes according to the actual application scenario, and sets them according to the relative proportion of the initial value, so as to achieve the purpose of both preventing droplet falling and precise control of liquid transfer.

[0092] Meanwhile, this embodiment sets a basic threshold so that compensation is only performed when the value exceeds the preset threshold, which avoids the pump performing compensation actions too frequently and extends the service life of the equipment.

[0093] S6: Controls the piston in the pipette pump to dispense liquid, and simultaneously controls the pipette pump to move upward as the liquid level rises, so that the pipette tip remains within a preset distance from the liquid level.

[0094] By using the liquid level following method described above, the liquid nozzle is moved during the liquid aspiration process to always maintain a certain height above the liquid level and rise with the liquid level, thus solving the problem that the liquid easily sticks to the outer wall of the nozzle during the liquid separation process, resulting in inaccurate results.

[0095] S7: Empty the liquid.

[0096] The aforementioned emptying function completely empties the liquid from the pipette tip, primarily addressing issues of incomplete separation and clogging. The pipette pump adaptively reserves a stroke for air purging after resetting. This means that even without liquid being drawn in, the pump can automatically expel some air. Based on this design, after liquid is drawn in, when the emptying function is activated, the pipette pump's stroke is the volume of liquid drawn in plus the reserved stroke, thus achieving complete liquid expulsion. After emptying, the pipette pump automatically resets and reserves another stroke for air purging. The emptying function can be used cyclically during pipetting.

[0097] The above-mentioned pneumatic pipetting pump's pipetting control method improves sensitivity and stability during liquid level detection, eliminates the need for high-cost special consumables such as conductive materials, avoids radiation emission exceeding standards, and efficiently performs various operations from tube to plate, such as serum separation, bacterial culture transfer, and nucleic acid transfer.

[0098] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0099] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for controlling the pipetting of a pneumatic pipetting pump, characterized in that, The liquid level detection step includes: S1: Start the real-time air pressure acquisition system to collect the air pressure value inside the piston cylinder of the pipette pump; S2: First, control the piston in the pipette pump to move upward a preset distance, then control the pipette pump to move towards the liquid surface, and at the same time control the piston in the pipette pump to move towards the liquid surface at a predetermined speed, so that the piston cylinder generates a continuous outward airflow. S3: When the gas pressure sensor in the pipette pump detects a change in the amplitude of the gas pressure waveform that is greater than the preset liquid surface trigger threshold, it is determined that the liquid surface has been contacted and detected. The gas pressure waveform amplitude is filtered as follows: gas pressure values ​​are collected at predetermined time points. After collecting gas pressure values ​​at several time points, they are sorted according to their magnitude. Several gas pressure values ​​at the top and bottom of the sort are removed. The remaining gas pressure values ​​are averaged and used as the difference in the amplitude of the gas pressure waveform.

2. The pipetting control method for a pneumatic pipetting pump according to claim 1, characterized in that, In step S2, the starting position of the pipette pump is taken as the origin, and the distance between the contact point of the liquid surface detected by the pipette pump and the origin is taken as the descent height. The depth of the liquid to be pipetted is calculated by the distance between the bottom of the container holding the liquid to be pipetted and the origin. The volume of the liquid to be pipetted is calculated by combining the shape of the container.

3. The pipetting control method for a pneumatic pipetting pump according to claim 1, characterized in that, In step S3, the air pressure waveform amplitude is filtered as follows: air pressure values ​​are collected at time points of 100±20μs. After collecting air pressure values ​​at 30±10 time points, they are sorted according to their magnitude. The air pressure values ​​at the top and bottom 5±3 are removed. The remaining air pressure values ​​are averaged and used as the difference in the change of air pressure waveform amplitude.

4. The pipetting control method for a pneumatic pipetting pump according to claim 1, characterized in that, It also includes a liquid aspiration step, which includes: S4: Controls the piston in the pipette pump to draw liquid, and simultaneously controls the pipette pump to move downwards as the liquid level drops, so that the pipette tip remains immersed in the liquid at a preset depth.

5. The pipetting control method for a pneumatic pipetting pump according to claim 4, characterized in that, It also includes a pipetting quality monitoring step, which is performed concurrently with the aspiration step, and the pipetting quality monitoring step includes: aspiration air monitoring, bubble monitoring and blockage monitoring; The vacuum monitoring includes the following steps: comparing the real-time collected air pressure waveform with the preset normal pipetting waveform; when the difference in the change of the air pressure waveform amplitude during the aspiration process is less than the difference in the change of the preset vacuum waveform amplitude, it is determined to be vacuum. The blockage monitoring includes the following steps: comparing the real-time collected air pressure waveform with the preset normal pipetting waveform; when the change amplitude of the air pressure waveform is greater than the difference between the preset normal waveform and the pressure remains low during the aspiration process, it is determined to be a blockage. The bubble monitoring includes the following steps: comparing the real-time collected air pressure waveform with the preset normal pipetting waveform; when the change amplitude of the air pressure waveform during the aspiration process is between the difference between the preset normal waveform change amplitude and the preset aspiration waveform change amplitude, it is determined that a bubble is aspirated. The difference in the amplitude of the normal waveform change is greater than the difference in the amplitude of the suction waveform change.

6. The pipetting control method for a pneumatic pipetting pump according to any one of claims 1-5, characterized in that, After the liquid aspiration step is completed, a droplet prevention step is also included, which includes: S5: Real-time monitoring of the collected air pressure value, using the air pressure value at the time of liquid aspiration as the initial value to prevent liquid from falling. When the amplitude of the air pressure value waveform changes beyond the threshold, the control piston moves upward to aspirate the liquid back, so that the air pressure value returns to the initial value range.

7. The pipetting control method for a pneumatic pipetting pump according to claim 6, characterized in that, It also includes a separation step, which includes: S6: Controls the piston in the pipette pump to dispense liquid, and simultaneously controls the pipette pump to move upward as the liquid level rises, so that the pipette tip remains within a preset distance from the liquid level.

8. A pneumatic pipette pump, characterized in that, include: A pipetting pump assembly and a pipetting control system, wherein the pipetting control system performs pipetting operations using the control method described in any one of claims 1-7.

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