A method for controlling liquid flow sample loading pressure of flow cell sorter

Abstract

The invention discloses a method for controlling liquid flow sample loading pressure of a flow cell sorter, which belongs to the field of cell sorting. By building a liquid flow sample loading system for the flow cell sorter, an air supply path is connected to a sample path and a sheath liquid path, and the sample path and the sheath liquid path are connected to a droplet generation path. The sample path is provided with a first electrical proportional valve, which is used to adjust the air pressure in a sample tube. The sheath liquid path is provided with a second electrical proportional valve, which is used to adjust the air pressure in a sheath liquid barrel. According to Bernoulli's theorem in fluid mechanics, since #imgabs0# reflects the pressure difference corresponding to the sample loading flow rate, the pressure difference corresponding to the sample loading flow rate is replaced by the pressure difference between input and output to obtain a theoretical value of the first electrical proportional valve. The method adopts an incremental digital PID control algorithm to obtain the k-th and k-1-th pressure output values of the PID controller, thereby improving the control accuracy of the loading flow rate.

Description

Technical Field

[0001] The present invention relates to the field of cell sorting, in particular to a method for controlling liquid flow sample loading pressure of a flow cell sorter. Background Art

[0002] A flow cytometer is a device for high-throughput analysis and sorting and enrichment of cells. It performs optical detection based on physical, chemical, and immunological characteristics of cells, and then sorts and enriches specific cell subpopulations within a preselected parameter range. Compared to flow cytometers, flow cytometers also incorporate two key hardware components: a droplet generator and a nozzle. The droplet generator is mounted at the front end of the flow chamber, where a piezoelectric transducer applies ultrahigh frequency energy to the sheath fluid and sample streams to generate uniformly sized, evenly spaced droplets. The nozzle, mounted at the flow chamber outlet, features a tiny orifice that limits the size of the generated droplets, typically with an aperture of 70 to 130 μm. Due to the significant flow resistance of the nozzle's tiny orifice, the fluidics system of a flow cytometer differs significantly from that of an analyzer. In particular, the sheath fluid pressure required to achieve three-dimensional hydrodynamic focusing can be increased tenfold or even dozens of times. Fluid pumps commonly used in flow cytometers to drive sheath fluid at constant pressure or constant flow, such as diaphragm pumps, peristaltic pumps, and syringe pumps, are generally difficult to use in sorters. Therefore, flow cytometers typically use pneumatic control systems to drive the sheath fluid and sample flow at constant pressure or constant flow.

[0003] In a sorting instrument, sample flow is introduced via the pressure differential between the sample tube and the droplet generator. The sample flow rate typically needs to be controlled between 10 and 100 μL / min. The low sample flow rate places high demands on precise pressure differential control. Typically, the control accuracy of an electroproportional valve used for air pressure regulation is 1% to 5% of full-scale range, and higher-precision electroproportional valves are very expensive. To ensure that the sample flow from the tube flows into the droplet generator, the pressure in the tube must be higher than that in the droplet generator. Therefore, the range of the electroproportional valve used to control the sample flow is typically between several and 10 atmospheres. The pressure control accuracy of this proportional valve is on the same order of magnitude as the driving pressure differential for the sample flow, making sample flow control accuracy difficult to meet instrument requirements. Furthermore, changes in the sheath fluid level in the droplet generator also alter the sheath fluid pressure in the droplet generator, which in turn changes the driving pressure differential for the sample flow, resulting in changes in the sample flow rate. Furthermore, changes in the sample level in the tube also affect the driving pressure differential for the sample flow, further impacting the control accuracy of the sample flow rate.

[0004] To achieve low-flow sample flow, currently available instruments typically add a micro-flow sensor to the sample flow path for feedback control. This method can improve sample flow control to a certain extent, but it still has some problems: First, flow sensors are relatively expensive, increasing the hardware cost of the instrument; second, compared to pressure sensors, flow sensors have lower sensitivity, requiring a longer time for their output to stabilize, and cannot quickly respond to changes in pressure differentials; third, the detection accuracy of flow sensors is typically 5% to 10% of the full scale, resulting in low measurement accuracy. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide a method for controlling the liquid flow sample loading pressure of a flow cell sorter, which improves the control accuracy of the sample loading flow rate.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] A method for controlling the liquid flow sample loading pressure of a flow cell sorter comprises the following steps:

[0008] Build a flow cytometer liquid sampling system, connect the air supply path with the sample path and the sheath liquid path, the sample path and the sheath liquid path are connected to the droplet generation path, the sample path is provided with a first electrical proportional valve, the first electrical proportional valve is used to adjust the air pressure in the sample tube, and the sheath liquid path is provided with a second electrical proportional valve, the second electrical proportional valve is used to adjust the air pressure in the sheath liquid tank;

[0009] When the flow cytometer liquid sample loading system is working, the following are achieved:

[0010]

[0011] Wherein, P1 is the theoretical value output by the first electrical proportional valve; P2 is the theoretical value output by the second electrical proportional valve; P3 is the pressure value in the flow chamber; z1 is the height difference between the bottom end of the sampling needle and the output end face of the sampling needle tube in the flow chamber when the sample is injected; z2 is the height difference between the bottom end face of the sheath liquid barrel and the center of the flow chamber; h1 is the sample liquid level; h2 is the sheath liquid level; v ST is the average flow velocity of the sheath fluid in the flow chamber, v SP is the average flow rate of the sample flow in the flow chamber;

[0012] Subtracting formula (1) from formula (2) yields

[0013]

[0014] because The pressure difference corresponding to the sample loading flow rate is reflected by the pressure difference between input and output ΔPSP Substitute formula (3) Too small and can be ignored, P2 adopts the actual value of the second electrical proportional valve, so we get

[0015] P1=ΔP SP +P2-ρg(z2-z1+h1-h2) (4)

[0016] Using incremental digital PID control algorithm, we can get When u o (k)=u o (k-1)+K P (e(k)-e(k-1))+K I e(k)+K D (e(k)-2e(k-1)+e(k-2))(5)

[0017] when When u o (k)=u o (k-1)(6)

[0018] Where ε is the expected error limit percentage; u o (k),u o (k-1) are the pressure output values of the PID controller at the kth and k-1th times respectively; e(k) is the output pressure error of the first electrical proportional valve at the kth time, that is, P1(k)-P1actual(k); K P , K I , K D are the proportional, integral and differential adjustment parameters of the PID controller respectively.

[0019] Furthermore, the sample sampling needle and sampling pipeline are simplified into a slender hole model to obtain ΔP SP .

[0020] Furthermore, the sample flow rate Q SP The pressure difference ΔP between the input and output of the elongated hole model SP It is a linear relationship, that is:

[0021] ΔP SP =K SP Q SP (7)

[0022] K SP is the linear coefficient. According to formula (7), different Q SP ΔP under SP .

[0023] Furthermore, to ensure high-precision control of the sample loading flow rate, ε is 0.01% to 0.2%.

[0024] Furthermore, the data sampling rate in the flow cell sorter liquid flow sample loading pressure control method is 10 to 120 times per minute.

[0025] Furthermore, a first liquid level gauge is provided in the sample tube in the sample flow path, and the first liquid level gauge obtains the sample liquid level height h1.

[0026] Furthermore, a second liquid level gauge is provided in the sheath liquid barrel in the sheath liquid flow path, and the second liquid level gauge obtains the sheath liquid level height h2.

[0027] Furthermore, the cell sorter liquid flow loading system includes an air pressure feedback controller, which takes the expected air pressure output value and the actual pressure measurement value as input, and outputs a digital signal for controlling the first electrical proportional valve or the second electrical proportional valve through an air pressure feedback control algorithm.

[0028] Furthermore, the air pressure feedback controller is an incremental PID controller.

[0029] Furthermore, the sample flow path is provided with a first pressure gauge, which is used to monitor the output pressure P of the first electrical proportional valve in real time. 1实际 The sheath fluid flow path is provided with a second pressure gauge, and the second pressure gauge is used to monitor the output air pressure of the second electrical proportional valve in real time.

[0030] Compared with the prior art, the flow cell sorter liquid flow sample pressure control method of the present invention builds a flow cell sorter liquid flow sample system, connects the air supply path with the sample path and the sheath liquid path, and the sample path and the sheath liquid path are connected with the droplet generation path. The sample path is provided with a first electrical proportional valve, which is used to adjust the air pressure in the sample tube, and the sheath liquid path is provided with a second electrical proportional valve, which is used to adjust the air pressure in the sheath liquid barrel. According to Bernoulli's theorem in fluid mechanics, since What is reflected is the pressure difference corresponding to the sample loading flow rate. The pressure difference between the input and output is used to replace the pressure difference corresponding to the sample loading flow rate to obtain the theoretical value of the first electrical proportional valve. The incremental digital PID control algorithm is used to control it, and the k-th and k-1-th pressure output values of the PID controller are obtained, thereby improving the control accuracy of the loading flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of the method for controlling the liquid flow sample loading pressure of a flow cell sorter according to the present invention;

[0032] Figure 2 Schematic diagram of the structure of the liquid flow sample loading system of the flow cell sorter of the present invention;

[0033] Figure 3This is a control block diagram of the liquid flow loading system of the flow cell sorter of the present invention.

[0034] In the figure: 10, air supply path; 11, compressor; 12, filter; 13, water mist separator; 14, pressure reducing valve; 15, gas storage tank; 16, safety valve; 20, sample flow path; 21, first electrical proportional valve; 22, first pressure gauge; 23, sample tank; 24, sample tube; 25, sampling needle; 26, first liquid level gauge; 30, sheath liquid flow path; 31, second electrical proportional valve; 32, second pressure gauge; 33, sheath liquid barrel; 34, second liquid level gauge; 35, flow meter; 40, droplet generation flow path; 41, third pressure gauge; 42, flow chamber; 43, flow chamber; 44, nozzle. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] See also Figure 1 The present invention provides a method for controlling the liquid flow sample loading pressure of a flow cell sorter, comprising the following steps:

[0038] Build a flow cytometer liquid sampling system, connect the air supply path with the sample path and the sheath liquid path, the sample path and the sheath liquid path are connected to the droplet generation path, the sample path is provided with a first electrical proportional valve, the first electrical proportional valve is used to adjust the air pressure in the sample tube, and the sheath liquid path is provided with a second electrical proportional valve, the second electrical proportional valve is used to adjust the air pressure in the sheath liquid tank;

[0039] When the flow cytometer liquid sample loading system is working, the following are achieved:

[0040]

[0041] Wherein, P1 is the theoretical value output by the first electrical proportional valve; P2 is the theoretical value output by the second electrical proportional valve; P3 is the pressure value in the flow chamber; z1 is the height difference between the bottom end of the sampling needle and the output end face of the sampling needle tube in the flow chamber when the sample is injected; z2 is the height difference between the bottom end face of the sheath liquid barrel and the center of the flow chamber; h1 is the sample liquid level; h2 is the sheath liquid level; v ST is the average flow velocity of the sheath fluid in the flow chamber, v SP is the average flow rate of the sample flow in the flow chamber;

[0042] Subtracting formula (1) from formula (2) yields

[0043]

[0044] because The pressure difference corresponding to the sample loading flow rate is reflected by the pressure difference between input and output ΔP SP Substitute formula (3) Too small and can be ignored, P2 adopts the actual value of the second electrical proportional valve, so we get

[0045] P1=ΔP SP +P2-ρg(z2-z1+h1-h2) (4)

[0046] Using incremental digital PID control algorithm, we can get When u o (k)=u o (k-1)+K P (e(k)-e(k-1))+K I e(k)+K D (e(k)-2e(k-1)+e(k-2))(5)

[0047] when When u o (k)=u o (k-1)(6)

[0048] Where ε is the expected error limit percentage; u o (k),u o (k-1) are the pressure output values of the PID controller at the kth and k-1th times respectively; e(k) is the output pressure error of the first electrical proportional valve at the kth time, that is, P1(k)-P1actual(k); K P , K I , K D are the proportional, integral and differential adjustment parameters of the PID controller respectively.

[0049] For details, please refer to Figure 2The flow cytometer liquid loading system includes an air supply circuit 10, a sample circuit 20, a sheath liquid circuit 30, and a droplet generation circuit 40. The sample circuit 20 and the sheath liquid circuit 30 are respectively connected to the air supply circuit 10. The air supply circuit 10 drives the sample in the sample circuit 20 and the sheath liquid in the sheath liquid circuit 30. The sample circuit 20 and the sheath liquid circuit 30 are connected to the droplet generation circuit 40. The sample in the sample circuit 20 and the sheath liquid in the sheath liquid circuit 30 enter the droplet generation circuit 40 to generate droplets.

[0050] The air supply circuit 10 comprises a compressor 11, a filter 12, a mist separator 13, a pressure reducing valve 14, and an air tank 15, connected in sequence. A safety valve 16 is mounted on the air tank 15. The pressure reducing valve 14 is used to initially regulate the output pressure of the compressor 11, which can be adjusted manually or electrically. This output pressure is typically set to 1.2 to 2 times the maximum supply pressure in the sheath fluid flow path 30, but not exceeding the maximum allowable input pressure of the first and second electrical proportional valves 21 and 31. The air tank 15 stores the compressed gas after the pressure reduction by the pressure reducing valve 14. The safety valve 16 ensures the safety of the air supply pressure at its downstream end. The safety valve 16 can be a pressure switch with a built-in contact spring. When the pressure in the air tank 15 exceeds 80% to 100% of the maximum allowable input pressure of the first or second electrical proportional valves 21 and 31, the safety valve 16 automatically opens and releases air, reducing the pressure in the air tank 15 to the set value. Otherwise, the safety valve 16 remains closed.

[0051] The sample flow path 20 includes a first electrical proportional valve 21, a first pressure gauge 22, a sample tank 23, a sample tube 24, and a sampling needle 25, which are connected in sequence. A first liquid level gauge 26 is installed in the sample tube 24. The first electrical proportional valve 21 is used to adjust the air pressure in the sample tube 24; the first pressure gauge 22 is used to monitor the output air pressure of the first electrical proportional valve 21 in real time; the compressed gas output by the first electrical proportional valve 21 is input into the sample tank 23 to drive the sample under positive pressure; the sample tube 24 is fixed in the sample tank 23, and the sample in the sample tube 24 flows out through the sampling needle 25 under air pressure; the sampling needle 25 is equipped with a first liquid level gauge 26, which is a capacitive level gauge and is used for sample transmission and monitoring the liquid level of the sample in the sample tube 24.

[0052] The sheath fluid flow path 30 includes a second electrical proportional valve 31, a second pressure gauge 32, a sheath fluid tank 33, and a flow meter 35, which are connected in sequence. A second level gauge 34 is mounted on the sheath fluid tank 33. The second electrical proportional valve 31 is used to adjust the air pressure in the sheath fluid tank 33; the second pressure gauge 32 is used to monitor the output pressure of the second electrical proportional valve 31 in real time. The compressed gas output by the second electrical proportional valve 31 is input into the sheath fluid tank 33 to drive the sheath fluid with positive pressure. The second level gauge 34 is mounted in the sheath fluid tank 33 to monitor the sheath fluid level. The flow meter 35 is connected to the sheath fluid pipeline to measure the flow rate of the sheath fluid. The second level gauge 34 is preferably a float-type or ultrasonic continuous level sensor.

[0053] The droplet generation flow path 40 includes a flow chamber 42, a flow cell 43, and a nozzle 44, which are connected in sequence. A third pressure gauge 41 is mounted on the flow chamber 42. The flow chamber 42 in the droplet generation flow path 40 is used for three-dimensional hydrodynamic focusing of the sample. After the sheath fluid and sample flow into the flow chamber 42, the sheath fluid envelops the sample to achieve single-cell arrangement of cells in the sample. The third pressure gauge 41 is connected to the pipeline in the flow chamber 42 to monitor the hydraulic pressure of the fluid in the flow chamber 42. The inlet of the flow chamber 43 is connected to the outlet of the flow chamber 42 for flow cytometry analysis of cells. The inlet of the nozzle 44 is connected to the outlet of the flow chamber 43. The inner diameter of the nozzle 44 is between 70 and 130 μm, and is used to generate droplets of stable size.

[0054] Please continue reading Figure 3 The control module of the liquid flow loading system of the flow cytometer includes a microprocessor and a central controller to monitor or control the liquid flow system. Among them, the analog-to-digital converter (A / D) in the microprocessor is used to receive in real time the output electrical signals (current signals or voltage signals) of the first pressure gauge 22, the second pressure gauge 32, and the third pressure gauge 41 for monitoring the pressure, as well as the output electrical signals of the first liquid level gauge 26 and the second liquid level gauge 34 for monitoring the liquid level, and convert the received electrical signals into corresponding digital signals; the microprocessor receives the expected air pressure output value (theoretical value) of the first electrical proportional valve 21 and the second electrical proportional valve 31 output by the central controller; the microprocessor includes a pneumatic pressure feedback controller, which takes the expected air pressure output value and the actual pressure measurement value as input, and outputs a digital signal for controlling the first electrical proportional valve 21 and the second electrical proportional valve 31 through a pneumatic pressure feedback control algorithm; the digital-to-analog converter (D / A) in the microprocessor converts the digital signal output by the pneumatic pressure feedback controller into an analog electrical signal, and outputs the analog electrical signal to the actuator, namely the first electrical proportional valve 21 or the second electrical proportional valve 31 respectively; the resolution of the A / D or D / A chip is preferably 16 bit or 24 bit; the pneumatic pressure feedback controller is preferably an incremental PID controller.

[0055] The central controller calculates or outputs the expected air pressure output value of the first or second electrical proportional valve 21, 31, based on input information such as the fluid flow state, nozzle model, and sample injection flow rate set by the instrument user in the host computer software. The fluid flow state includes, but is not limited to, power-on, normal operation, bubble removal, power-off, and cleaning states. The nozzle model refers to the nozzle aperture size used in flow cell sorters, such as the commonly used 70μm, 85μm, 100μm, or 130μm. The sample injection flow rate is set by the instrument user in the host computer software, with a typical flow rate setting range of 10 to 120μL / min. The central controller then outputs the automatically calculated expected air pressure output value to the microprocessor as an input variable for the microprocessor.

[0056] This reflects the flow rate of sample loading, because v SP Very small, for v SP The measurement is very inconvenient. Therefore, in practical applications, it is necessary to simplify the sample sampling needle 25 and the sampling pipeline into a slender hole model. Through actual experiments, it can be obtained that for the horizontally placed slender hole model, the sample flow rate Q SP The pressure difference ΔP between the input and output of the model SP It is a linear relationship, that is:

[0057] ΔP SP =K SP Q SP (7)

[0058] K SP is the linear coefficient. According to formula (7), different Q SP ΔP under SP .

[0059] To ensure high-precision control of the sample flow rate, ε is set to 0.01% to 0.2%. The sensor sampling rate has a significant impact on the three adjustment parameters of the PID controller. At the same time, considering the response time of each pressure gauge and level gauge, the data sampling rate is 10 to 120 times / minute.

[0060] The flow cell sorter liquid flow sample pressure control method of the present invention is to build a flow cell sorter liquid flow sample system, connect the air supply path 10 with the sample flow path 20 and the sheath liquid flow path 30, the sample flow path 20 and the sheath liquid flow path 30 are connected to the droplet generation flow path 40, the sample flow path 20 is provided with a first electrical proportional valve 21, the first electrical proportional valve 21 is used to adjust the air pressure in the sample tube 24, the sheath liquid flow path 30 is provided with a second electrical proportional valve 31, the second electrical proportional valve 31 is used to adjust the air pressure in the sheath liquid barrel 33; according to Bernoulli's theorem in fluid mechanics, since What is reflected is the pressure difference corresponding to the sample loading flow rate. The pressure difference corresponding to the sample loading flow rate is replaced by the pressure difference of the input and output to obtain the theoretical value of the first electrical proportional valve 21. The incremental digital PID control algorithm is used to control it, and the k-th and k-1-th pressure output values of the PID controller are obtained, thereby improving the control accuracy of the loading flow rate.

[0061] The above embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patented invention. It should be noted that those skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention. These variations and improvements are equivalent modifications and improvements to the above embodiments based on the essential technology of the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for controlling the liquid flow sample loading pressure of a flow cell sorter, characterized in that: The following steps are involved: Build a flow cytometer liquid sampling system, connect the air supply path with the sample path and the sheath liquid path, the sample path and the sheath liquid path are connected to the droplet generation path, the sample path is provided with a first electrical proportional valve, the first electrical proportional valve is used to adjust the air pressure in the sample tube, and the sheath liquid path is provided with a second electrical proportional valve, the second electrical proportional valve is used to adjust the air pressure in the sheath liquid tank; When the flow cytometer liquid sample loading system is working, the following are achieved: Wherein, P1 is the theoretical value output by the first electrical proportional valve; P2 is the theoretical value output by the second electrical proportional valve; P3 is the pressure value in the flow chamber; z1 is the height difference between the bottom end of the sampling needle and the output end face of the sampling needle tube in the flow chamber when the sample is injected; z2 is the height difference between the bottom end face of the sheath liquid barrel and the center of the flow chamber; h1 is the sample liquid level; h2 is the sheath liquid level; v ST is the average flow velocity of the sheath fluid in the flow chamber, v SP is the average flow rate of the sample flow in the flow chamber; Subtracting formula (1) from formula (2) yields because The pressure difference corresponding to the sample loading flow rate is reflected by the pressure difference between input and output ΔP SP Substitute formula (3) Too small and can be ignored, P2 adopts the actual value of the second electrical proportional valve, so we get P1=ΔP SP +P2-ρg(z2-z1+h1-h2) (4) Using incremental digital PID control algorithm, we can get When u o (k) = u o (k - 1)+K P (e(k)-e(k - 1))+K I e(k)+K D (e(k)-2e(k - 1)+e(k - 2))(5) when When u o (k)=u o (k-1)(6) Where ε is the expected error limit percentage; u o (k),u o (k-1) are the pressure output values of the PID controller at the kth and k-1th times respectively; e(k) is the output pressure error of the first electrical proportional valve at the kth time, that is, P1(k)-P1actual(k); K P , K I , K D are the proportional, integral and differential adjustment parameters of the PID controller respectively.

2. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 1, wherein: The sample sampling needle and sampling pipeline are simplified into a slender hole model to obtain ΔP SP .

3. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 2, wherein: Sample flow rate Q SP The pressure difference ΔP between the input and output of the elongated hole model SP It is a linear relationship, that is: ΔP SP =K SP ·Q SP (7) K SP is the linear coefficient. According to formula (7), different Q SP ΔP under SP .

4. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 1, wherein: To ensure high-precision control of the sample loading flow rate, ε is 0.01% to 0.2%.

5. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 1, wherein: The data sampling rate in the flow cell sorter liquid flow sample loading pressure control method is 10 to 120 times per minute.

6. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 1, wherein: A first liquid level gauge is provided in the sample tube in the sample flow path, and the first liquid level gauge obtains the sample liquid level height h1.

7. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 1, wherein: A second liquid level gauge is provided in the sheath liquid barrel in the sheath liquid flow path, and the second liquid level gauge obtains the sheath liquid level height h2.

8. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 1, wherein: The cell sorter liquid flow loading system includes an air pressure feedback controller, which takes the expected air pressure output value and the actual pressure measurement value as input, and outputs a digital signal for controlling the first electrical proportional valve or the second electrical proportional valve through an air pressure feedback control algorithm.

9. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 8, characterized in that: The air pressure feedback controller is an incremental PID controller.

10. The method for controlling liquid flow sample loading pressure of a flow cytometer according to claim 8, wherein: The sample flow path is provided with a first pressure gauge, which is used to monitor the output pressure P of the first electrical proportional valve in real time. 1实际 The sheath fluid flow path is provided with a second pressure gauge, and the second pressure gauge is used to monitor the output air pressure of the second electrical proportional valve in real time.

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