Method and device for controlling liquid reciprocating flow based on magnetic force and application

Abstract

The application discloses a method and device for controlling liquid reciprocating flow based on magnetic force and application. The method provided by the application utilizes the interfacial capillary force generated by the hydrophilic magnet on the gas / liquid / solid three-phase interface formed before the liquid is separated to realize the flow control of the liquid. The method has the advantages of: 1) non-contact flow control, which can avoid the pollution caused by contact control (such as mechanical probe control); 2) the liquid is moved smoothly and quickly, no bubbles and new gas-liquid interfaces are generated, the severe friction and vibration on the gas-liquid interface are avoided, and the aerosol generation probability is reduced; 3) compared with the existing magnetic control mode for moving or disturbing the liquid by pushing force, the aerosol pollution risk is greatly reduced. In addition, the beneficial effects of only 1-2 minutes for one round of antigen-antibody combination and 5-15 minutes for one detection are realized, and the detection speed is much higher than that of the traditional immunodetection method based on a reaction cup or a microhole plate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of immunoassay. More particularly, it relates to a method and device for controlling liquid reciprocating flow based on magnetic force and applications. BACKGROUND

[0002] Aerosol pollution is an important problem in the field of biomedical diagnosis, and is also an important factor affecting the safety of detection and the accuracy of detection results. Aerosol is a colloidal dispersion system composed of air and solid and liquid particles suspended therein. Generally, aerosol with liquid small particles as the dispersed phase can be generated by friction or oscillation of the gas-liquid interface. These aerosols can easily diffuse in a small space and re-attach to solid surfaces or fall back into the liquid.

[0003] In the process of medical detection, most detection operations can cause friction or oscillation of the gas-liquid interface, such as repeated pipetting, injection, shaking and oscillation of sample solution or reagents, rapid transportation of sample solution, rapid movement of reaction vessels (such as 96-well plates, reaction cups or microfluidic chips) containing sample solution, etc., thereby generating aerosols of sample solution or reagents. Sample solution usually contains marker molecules, cells, viruses or microorganisms of diseases, and the original sample without inactivation may still be infectious. When these aerosols attach to the surface of the instrument or vessel, they will cause sample contamination and reagent contamination on the instrument and vessel; sample contamination may cause the instrument and vessel to be infectious, thereby causing infection of the detection personnel, and reagent contamination may cause corrosion of the instrument and vessel. When these aerosols fall back into the sample solution, they will cause cross-contamination of the sample solution and slight changes in the amount of reaction reagents, which may cause the sample detection result to deviate from the true sample condition.

[0004] In order to solve the problem of aerosol pollution in the process of medical detection, in manual detection in the laboratory, the detection personnel usually provide sealed conditions for the reaction vessels loaded with sample solution to reduce the efficiency of aerosol release into the environment. However, in automated detection equipment (such as fully automatic enzyme-linked immunoassay instrument, fully automatic chemiluminescence detection instrument, microfluidic immunoassay instrument, etc.), the reaction vessels are usually open to facilitate automatic pipetting, sample loading, cleaning and other steps by the equipment. In addition, in automated detection equipment, especially small-sized automated detection equipment with small operation space, magnetic stirring, centrifugation and other flow control methods that can cause severe friction and oscillation of the gas-liquid interface are usually introduced to improve sample capture efficiency and detection speed, which can generate sample solution aerosols and may cause sample cross-contamination and instrument contamination, etc.

[0005] In summary, in the full-automatic detection equipment, especially in the small full-automatic detection equipment, it is necessary to introduce a mild and efficient flow control method to reduce the risk of aerosol generation on the basis of providing higher sample capture efficiency and detection speed. As the previous research of the inventor's team obtained a reciprocating flow type enzyme-linked immunoassay method (Chinese patent number: 202010116126.0), and developed a small portable full-automatic enzyme-linked immunoassay analyzer based on the control principle of air pressure change (Chinese patent number: 202110063475.5), the reciprocating flow strategy based on air pressure control provides stable liquid flow control of flow rate, and at the same time realizes rapid immune detection. In order to further reduce the friction and collision of gas-liquid interface leading to the generation of aerosol, it is urgent to develop and research more new methods and means to overcome the aerosol pollution hidden trouble problem in the existing biomedical detection field. SUMMARY

[0006] The technical problem to be solved by the present application is to overcome the aerosol pollution hidden trouble problem in the existing biomedical detection field. Based on the way of magnetically controlled drag liquid movement, the present application provides a reciprocating flow method and device for controlling liquid based on magnetic force, which realizes stable and rapid liquid flow control and avoids the generation of aerosol pollution, greatly reducing the friction and collision of liquid at the gas-liquid interface leading to the risk of aerosol pollution.

[0007] The purpose of the present application is to provide a method for controlling liquid reciprocating flow based on magnetic force.

[0008] Another purpose of the present application is to provide a reciprocating flow device based on magnetic force control.

[0009] Still another purpose of the present application is to provide a method for controlling liquid reciprocating flow of a reciprocating flow device based on magnetic force control.

[0010] Still another purpose of the present application is to provide the application of the reciprocating flow method and device based on magnetic force control.

[0011] Still another purpose of the present application is to provide an immune detection method.

[0012] The above purposes of the present application are achieved by the following technical solutions:

[0013] The present application provides a method for controlling liquid reciprocating flow based on magnetic force. A hydrophilic magnet is added to the liquid to be tested. The hydrophilic magnet is moved to the edge of the gas-liquid interface of the liquid by an external magnetic field, and a gas / liquid / solid three-phase interface is formed on the surface of the hydrophilic magnet. Before the hydrophilic magnet separates from the liquid, the three-phase interface on the surface of the hydrophilic magnet will generate an interfacial capillary force, which is the traction force for controlling the liquid flow. The external magnetic field provides a magnetic control driving force to drag the liquid to move in the state of not completely separating from the liquid, thereby realizing the reciprocating flow control of the liquid.

[0014] After the liquid contacts and wraps the hydrophilic magnet, the hydrophilic magnet is moved to the edge of the gas-liquid interface of the liquid, and the hydrophilic magnet is continuously moved outside the liquid to separate the hydrophilic magnet from the liquid. At this time, the hydrophilic magnet breaks through the gas-liquid interface of the liquid, so that a gas / liquid / solid three-phase interface is formed on the surface of the hydrophilic magnet, which is specifically manifested as a solid / liquid contact line that surrounds the edge of the liquid on the surface of the hydrophilic magnet. Subsequently, when the hydrophilic magnet continues to attempt to separate from the liquid, the change in interfacial energy on the gas / liquid / solid three-phase interface will be generated; the change in interfacial energy is further converted into interfacial capillary force applied to the hydrophilic magnet and the liquid at the same time on the solid / liquid contact line. For the liquid, the interfacial capillary force points to the outside of the liquid along the movement direction of the hydrophilic magnet, thereby driving the liquid to move along the movement direction of the hydrophilic magnet as a traction force to achieve the control of the liquid flow. Simply put, the reciprocating flow control of the liquid is achieved by moving the hydrophilic magnet to drag the liquid to move.

[0015] Specifically, the interfacial capillary force needs to overcome the sliding friction between the liquid end and the inner wall of the pipeline, and the total surface tension generated by the contact line of the liquid end edge on the inner wall of the pipeline, so that the liquid can be moved by the interfacial capillary force. The movement of the liquid driven by the hydrophilic magnet needs to meet the following force conditions:

[0016] F 界面毛细力 >f 液体滑动摩擦力 +f 液体表面张力

[0017] At the same time, in order to enable the hydrophilic magnet to continuously provide the interfacial capillary force for the movement of the liquid, the hydrophilic magnet needs to maintain a state of being magnetically controllable and not being separated from the liquid; at this time, after the magnetic control driving force driving the movement of the hydrophilic magnet overcomes the sliding friction between the hydrophilic magnet and the inner wall of the pipeline, it cannot further overcome the interfacial capillary force generated by the liquid on the hydrophilic magnet; the magnetic control driving force needs to meet the following force conditions:

[0018] 0<F 磁控驱动力 -f 磁体滑动摩擦力 ≤F 界面毛细力

[0019] In addition, after the hydrophilic magnet is added to the liquid to be tested, the magnetic control driving force needs to further overcome the resistance of the liquid moving in the pipeline after overcoming the sliding friction between the hydrophilic magnet and the inner wall of the pipeline; therefore, the magnetic control driving force also needs to meet the following force conditions:

[0020] F 磁控驱动力 -f 磁体滑动摩擦力 >f 液体滑动摩擦力 +f 液体表面张力

[0021] Compared with the existing magnetic control method for generating a propelling force by moving a magnet to move or disturb a liquid, the method has the characteristics of smooth and rapid liquid flow, and is not easy to cause violent friction and vibration of the liquid interface, so that the aerosol generation probability and aerosol pollution risk can be greatly reduced.

[0022] In particular, the interfacial capillary force is affected by the hydrophilic magnet properties and the liquid properties, and is limited by the hydrophilic magnet properties, the liquid properties, the pipeline size and properties, and the limit of the interfacial capillary force value can also be adjusted according to different conditions such as pipeline size, liquid type and volume, so as to adapt to other application scenarios. The preferred range of the interfacial capillary force provided by the application is: 1.251*10 -4 N < F 界面毛细力 <4.171*10 -3 N.

[0023] In particular, the magnetic control driving force is limited by the hydrophilic magnet properties, the liquid properties, the pipeline size and properties, and the limit of the magnetic control driving force can also be adjusted according to different conditions such as pipeline size, liquid type and volume, so as to adapt to other application scenarios. The preferred range of the magnetic control driving force provided by the application is: 4.5605*10 -4 N < F 磁控驱动力 <1.138*10 -2 N.

[0024] Preferably, the hydrophilic magnet is a magnetic material selected from one of a magnetic aluminum-nickel-cobalt material, a magnetic ferrite material and a magnetic neodymium-iron-boron alloy.

[0025] More preferably, the hydrophilic magnet can be flexibly changed according to the use requirements, and the shape thereof can also be flexibly changed according to the use requirements, including but not limited to a cylinder, a sphere, a cube and the like.

[0026] More preferably, the hydrophilic magnet used in the application is a cylinder of a neodymium-iron-boron alloy material.

[0027] Based on the principle of controlling liquid reciprocating flow by magnetic force, the application further provides a reciprocating flow device based on magnetic force control, comprising a support base, a microfluidic chip platform, a magnetic control driving device, an external controller and a microfluidic chip; the support base is provided with the magnetic control driving device, the microfluidic chip platform and the microfluidic chip above, and the microfluidic chip platform is arranged on both sides of the support base for supporting the microfluidic chip; the magnetic control driving device is fixed on the support base and electrically connected to the external controller at one end; the microfluidic chip comprises a bottom chip as a substrate, a middle chip providing a microfluid channel and a top chip with holes; the middle chip is provided with parallel microfluid channels, and each microfluid channel contains a hydrophilic magnet for cooperating with the magnetic force control.

[0028] Preferably, the magnetic control driving device controls magnetic force based on a stepping motor, and the magnetic control driving device comprises the stepping motor, a transmission rod and a magnetic plate; the stepping motor, the transmission rod and the magnetic plate are arranged above the support base; the stepping motor is fixed on the support base, one end of the stepping motor is mechanically connected with the transmission rod, and the other end of the stepping motor is electrically connected with an external controller; the transmission rod is arranged in parallel with the support base, and the other end of the transmission rod is fixed with the magnetic plate.

[0029] Preferably, the magnetic control driving device controls magnetic force based on an array inductor, and the magnetic control driving device comprises the array inductor and a circuit board connected with the inductor; the circuit board is arranged above the support base, and the array inductor is connected with the circuit board; the circuit board is fixed on the support base, and one end of the circuit board is electrically connected with the external controller; the array inductor is arranged in parallel with the support base, and the array inductor is arranged at a position corresponding to the position of the micro flow channel arranged in parallel in the microfluidic chip; the inductors parallel to the direction of the micro flow channel are connected in parallel, the inductors perpendicular to the direction of the micro flow channel are connected in series, and the interval between the array inductors is equal to the interval distance between the micro flow channels.

[0030] Preferably, the array inductor is as small as possible in size under the condition of meeting the requirement of providing sufficient F 磁控驱动力 .

[0031] Preferably, the array inductor is a non-shielded or semi-shielded inductor, and specifically, the array inductor can be one of a winding type, a patch type and a woven type.

[0032] The device provided by the application provides magnetic control driving force through the magnetic control driving device, connects the stepping motor with the external controller, drives the transmission rod to move the magnetic plate, thereby driving the hydrophilic magnet in the microfluidic chip to move to drag the liquid to move; or connects the array inductor circuit board with the external controller, and drives the hydrophilic magnet in the microfluidic chip to move to drag the liquid to move by sequentially connecting the inductors in each row to generate a changing magnetic field; moves the hydrophilic magnet to the edge of the gas-liquid interface of the liquid, and attempts to move the hydrophilic magnet to the outside of the liquid to make the hydrophilic magnet separate from the liquid; at this time, the hydrophilic magnet and the liquid must overcome the adhesion between them to do work, and the adhesion becomes the traction of the liquid movement; controls the amplitude of the movement of the hydrophilic magnet to be within the adhesion between the hydrophilic magnet and the liquid, so that the hydrophilic magnet continuously provides the traction for the movement of the liquid in the state of not completely separating from the liquid, thereby realizing the control of the liquid flow.

[0033] Further, the external controller sets motion parameters, inputs the magnetic control driving device, and drives the transmission rod to move the magnetic plate at a constant speed forward on the support base and then returns to the starting position, or sequentially connects the array inductor in each row to complete one motion cycle.

[0034] Further, the motion parameters include motion speed, motion distance and motion cycle number.

[0035] Preferably, the height of the hydrophilic magnet is less than the height of the microfluidic channel, and the width of the hydrophilic magnet is less than the width of the microfluidic channel.

[0036] The application provides a microfluidic chip manufacturing method, comprising the following steps:

[0037] S1, parallel long holes are made on the surface of a flat plastic sheet to obtain a middle layer chip;

[0038] S2, a plurality of circular holes are made on the surface of another flat plastic sheet to obtain a top layer chip;

[0039] S3, the flat bottom layer chip, the middle layer chip and the top layer chip are sequentially adhered together by an adhesive to obtain the microfluidic chip.

[0040] Preferably, the plastic sheet is one of polydimethylsiloxane, polystyrene, polypropylene, polymethyl methacrylate, polyethylene terephthalate, polyethylene, polyvinyl chloride and polyurethane.

[0041] More preferably, the long holes on the middle layer chip and the circular holes on the top layer chip with holes can be made by mechanical methods, laser cutting methods and the like.

[0042] Further preferably, the long holes on the middle layer chip are square holes with two circular holes connected to each end, the diameter of the circular holes is 0.4 cm, the length of the square holes is 2.0 cm, and the width of the square holes is 0.2 cm.

[0043] More specifically, the diameter of the circular holes on the top layer chip is 0.4 cm, and the positions of the circular holes correspond to the positions of the circular holes on the middle layer chip.

[0044] Preferably, the adhesive used when assembling the bottom layer chip, the middle layer chip and the top layer chip can be quick-drying glue, photocuring glue and the like, and can be flexibly changed according to actual use requirements.

[0045] More preferably, when assembling the bottom layer chip, the middle layer chip and the top layer chip, the bottom layer chip and the top layer chip form the bottom and the top of the square holes of the middle layer chip respectively, thereby forming the microfluidic channel; at this time, the circular holes of the top layer chip correspond to the circular holes of the middle layer chip one by one.

[0046] The application provides a method for controlling the reciprocating flow of liquid based on a magnetic force control liquid reciprocating flow device, which specifically comprises the following steps:

[0047] S1, placing a microfluidic chip above a microfluidic chip platform;

[0048] S2, injecting a liquid to be controlled into the microfluidic channel of the microfluidic chip;

[0049] S3, inputting motion parameters including motion speed, motion distance and motion cycle number to the magnetic control driving device through an external controller;

[0050] S4, starting the reciprocating flow device to drive the magnetic plate to move by the step motor driving transmission rod, or to drive the circuit board to connect the array inductance row by row to generate a changing magnetic field, so that the hydrophilic magnet in the microfluidic chip moves at a uniform speed from the starting position to the forward direction under the action of the magnetic control driving force, and the moving distance is equal to the motion distance set in S3;

[0051] S5, after the hydrophilic magnet in the microfluidic chip moves at a uniform speed to the set motion distance, the magnetic control driving device drives the hydrophilic magnet to move at a uniform speed back to the starting position at the speed set in S3, so as to complete a motion cycle;

[0052] S6, the reciprocating flow device repeats the steps of S4 and S5 in turn, and the repeating number is equal to the motion cycle number set in S3, so as to realize the reciprocating flow control.

[0053] The application also provides the application of the magnetic force control liquid reciprocating flow method or the magnetic force control liquid reciprocating flow device in liquid control, immune detection, nucleic acid detection and biological particle detection.

[0054] The application also provides an immune detection method, which comprises the following steps:

[0055] S1, preparing a microfluidic chip and placing it above a microfluidic chip platform;

[0056] S2, injecting a sample solution to be detected into the microfluidic channel of the microfluidic chip;

[0057] S3, setting the motion parameters of the external controller, inputting the magnetic control driving device, starting the reciprocating flow device to drive the magnetic plate to move by the step motor driving transmission rod, or to drive the circuit board to connect the array inductance row by row to generate a changing magnetic field, so that the hydrophilic magnet in the microfluidic chip moves at a uniform speed from the starting position to the forward direction at the motion speed set in S3, and the moving distance is equal to the motion distance set in S3; after the hydrophilic magnet in the microfluidic chip moves at a uniform speed to the set motion distance, the magnetic control driving device drives the hydrophilic magnet to move at a uniform speed back to the starting position at the speed set in S3, so as to complete a motion cycle;

[0058] S4, repeating the steps of S2 and S3 in turn according to the detection method, and the repeating number is equal to the motion cycle number set in S3, so as to realize the reciprocating flow control and detection.

[0059] Preferably, when the microfluidic chip is prepared in step S1, specific antibodies or antigens are coated on the bottom layer chip corresponding to the microfluidic channel position of the middle layer chip.

[0060] Preferably, the sample solution to be detected is added to the microfluidic channel from the top layer hole of the top layer of the microfluidic chip in step S2, and the capturing of the sample to be detected, the washing of the sample solution, the capturing of the second antibody, the washing of the second antibody solution, and the detection are sequentially performed.

[0061] The detection method described above, and the application further provides an optimal embodiment, which specifically comprises the following steps:

[0062] S1, coating specific antibodies or antigens on the bottom layer of the chip. Before assembling the microfluidic chip, specific antibodies or antigens are pre-coated on the bottom layer of the chip. The coated antibodies or antigens can specifically recognize the sample molecules to be detected. The size of the coated area is 0.2*0.4mm, and the position corresponds to the middle position of the square hole on the middle layer of the chip.

[0063] S2, capturing of the sample to be detected. The sample solution to be detected is added to the microfluidic channel from the top layer hole of the top layer, and then the reciprocating flow device is started to make the sample solution flow reciprocally for 5 cycles, and then the sample solution is discharged.

[0064] S3, washing of the sample solution. The washing solution is added to the microfluidic channel from the top layer hole, and the reciprocating flow device is started to make the washing solution flow unidirectionally and then be discharged. The washing is repeated for 3 times.

[0065] S4, capturing of the second antibody. Then, the second antibody solution labeled with a signal probe is added to the microfluidic channel from the top layer hole. The reciprocating flow device is started to make the second antibody solution flow reciprocally for 5 cycles, and then the second antibody solution is discharged.

[0066] S5, washing of the second antibody solution. The washing solution is added to the microfluidic channel from the top layer hole, and the reciprocating flow device is started to make the washing solution flow unidirectionally and then be discharged. The washing is repeated for 3 times.

[0067] S6, result detection. According to different detection methods, various detection means can be selected.

[0068] The application further provides the application of the above-mentioned method for controlling liquid reciprocating flow by magnetic force or the reciprocating flow device controlled by magnetic force in enzyme-linked immunoassay, fluorescent immunoassay, chemiluminescence immunoassay, or localized surface plasmon resonance detection.

[0069] The application has the following beneficial effects:

[0070] The application is based on the way of magnetically controlling liquid reciprocating flow, and provides a method for controlling liquid reciprocating flow by using the interfacial capillary force generated by the hydrophilic magnet on the gas / liquid / solid three-phase interface formed before the liquid is separated, so as to realize the flow control of the liquid. The method has the characteristics of smooth and rapid liquid flow, greatly reduces the severe friction and vibration of the liquid interface, avoids the generation of aerosol pollution, and can avoid the risk of aerosol pollution. The application also provides a reciprocating flow device controlled by magnetic force. Meanwhile, the application also provides an immune detection method, which uses the reciprocating flow device for detection and can be applied to various microfluidic immune detection, and has the following characteristics:

[0071] 1) A non-contact flow control method can avoid solid pollution and liquid pollution (such as mechanical probe control) caused by conventional contact control.

[0072] 2) The flow control method can make the liquid move smoothly and quickly, and will not generate bubbles to form a new gas-liquid interface, thereby avoiding the severe friction and vibration on the gas-liquid interface.

[0073] 3) Compared with the existing magnetic control method for generating a pushing force by moving a magnet to move or disturb the liquid, the reciprocating flow device controlled by magnetic force provided by the application greatly reduces the probability of aerosol generation, thereby reducing the risk of aerosol pollution.

[0074] 4) The reciprocating flow device controlled by magnetic force provided by the application is applied to various microfluidic immune detection, and only 1-2 minutes are needed for one round of antigen-antibody combination, and only 5-15 minutes are needed for one immune detection, so that the detection speed is much higher than that of the traditional immune detection method based on a reaction cup or a microplate. BRIEF DESCRIPTION OF DRAWINGS

[0075] Figure 1 It is a principle schematic diagram of the reciprocating flow method of the reciprocating flow device provided by the application.

[0076] Figure 2 It is a schematic diagram of the reciprocating flow device controlled by a stepping motor provided by the application (supporting base-1, microfluidic chip platform-11, stepping motor-21, transmission rod-22, magnetic plate-23, external controller-3, microfluidic chip-4).

[0077] Figure 3 It is a structural schematic diagram of a microfluidic chip provided by the application (microfluidic chip-4, bottom chip-41, middle chip-42, top chip-43, microfluidic channel-421, hydrophilic magnet-422).

[0078] Figure 4 It is a flow control process of the reciprocating flow device controlled by magnetic force in Example 1.

[0079] Figure 5 is a schematic diagram of the reciprocating flow device based on array inductance control provided by the present application (support base-1, microfluidic chip platform-11, circuit board-24, array inductance-25, external controller-3, microfluidic chip-4).

[0080] Figure 6 is the qualitative result of enzyme-linked immunoassay of human immunoglobulin G (IgG) by the reciprocating flow device based on magnetic force control in Example 2.

[0081] Figure 7 is the quantitative result of enzyme-linked immunoassay of human IgG by the reciprocating flow device based on magnetic force control in Example 2.

[0082] Figure 8 is the qualitative result of fluorescence immunoassay of human IgG by the reciprocating flow device based on magnetic force control in Example 3. DETAILED DESCRIPTION

[0083] The present application will be further described in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and equipment used in the present application are conventional reagents, methods and equipment in the technical field.

[0084] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0085] Example 1 A method for controlling liquid reciprocating flow based on magnetic force

[0086] The present application aims at the aerosol pollution hidden danger problem in the field of biomedical detection, and provides a method for controlling liquid reciprocating flow based on magnetic force. A hydrophilic magnet is added to the liquid to be detected, the hydrophilic magnet is moved to the edge of the gas-liquid interface of the liquid by an external magnetic field, a gas / liquid / solid three-phase interface is formed on the surface of the hydrophilic magnet, and before the hydrophilic magnet separates from the liquid, the three-phase interface on the surface of the hydrophilic magnet will generate an interfacial capillary force, which is the traction force for controlling the liquid flow. By providing a magnetic control driving force by an external magnetic field to control the movement of the hydrophilic magnet, the reciprocating flow control of the liquid can be realized.

[0087] The present application moves the hydrophilic magnet to the edge of the gas-liquid interface of the liquid after the liquid contacts and wraps the hydrophilic magnet, and attempts to continue to move the hydrophilic magnet outside the liquid to make it separate from the liquid. At this time, the hydrophilic magnet breaks through the gas-liquid interface of the liquid, thereby forming a gas / liquid / solid three-phase interface on the surface of the hydrophilic magnet, which is specifically manifested as a solid / liquid contact line that surrounds the edge of the liquid on the surface of the hydrophilic magnet. Subsequently, when the hydrophilic magnet attempts to continue to separate from the liquid, the change in interfacial energy on the gas / liquid / solid three-phase interface will be generated; the change in interfacial energy is further converted into interfacial capillary force applied to the hydrophilic magnet and the liquid at the same time on the solid / liquid contact line. For the liquid, the interfacial capillary force points to the outside of the liquid along the movement direction of the hydrophilic magnet, thereby driving the liquid to move along the movement direction of the hydrophilic magnet as a traction force to achieve control of the liquid flow. Simply put, the reciprocating flow control of the liquid is completed by moving the hydrophilic magnet to drag the liquid to move.

[0088] The principle of controlling the reciprocating flow of the liquid based on the magnetic force provided by the present application is shown in Figure 1 The hydrophilic magnet and the liquid must overcome the interfacial capillary force between them to do work, and the interfacial capillary force becomes the traction force for the movement of the liquid; the amplitude of the control of the hydrophilic magnet is controlled within the bearing range of the interfacial capillary force between the hydrophilic magnet and the liquid, so that the hydrophilic magnet is in a critical state of not completely separating from the liquid, and the traction force for the movement of the liquid is continuously provided, thereby realizing the control of the liquid flow.

[0089] Specifically, the interfacial capillary force needs to overcome the sliding friction between the liquid end and the inner wall of the pipeline, and the total surface tension generated by the contact line of the liquid end edge on the inner wall of the pipeline, in order to realize the movement of the liquid driven by the interfacial capillary force. The movement of the liquid driven by the hydrophilic magnet needs to meet the following force conditions:

[0090] F 界面毛细力 >f 液体滑动摩擦力 +f 液体表面张力

[0091] At the same time, in order to enable the hydrophilic magnet to continuously provide the interfacial capillary force for the movement of the liquid, the hydrophilic magnet needs to remain in a state of being magnetically controllable and not being separated from the liquid; at this time, the magnetic control driving force driving the movement of the hydrophilic magnet cannot further overcome the interfacial capillary force generated by the liquid on the hydrophilic magnet after overcoming the sliding friction between the hydrophilic magnet and the inner wall of the pipeline; the magnetic control driving force needs to meet the following force conditions:

[0092] 0<F 磁控驱动力 -f 磁体滑动摩擦力 ≤F 界面毛细力

[0093] In addition, after adding the hydrophilic magnet into the liquid to be tested, the magnetic control driving force needs to further overcome the resistance of the liquid moving in the pipeline after overcoming the sliding friction between the hydrophilic magnet and the inner wall of the pipeline; therefore, the magnetic control driving force also needs to meet the following force conditions:

[0094] F 磁控驱动力 -f 磁体滑动摩擦力 >f 液体滑动摩擦力 +f 液体表面张力

[0095] In addition, the interfacial capillary force and the magnetic control driving force are both affected by the properties of the hydrophilic magnet and the liquid, and are limited by the properties of the hydrophilic magnet, the liquid, the size and properties of the pipeline, and can be adjusted according to different conditions such as the size of the pipeline, the type and volume of the liquid, so as to adapt to other application scenarios.

[0096] The preferred range of the interfacial capillary force obtained by the present application is: 1.251*10 -4 N<F 界面毛细力 <4.171*10 -3 N, and the preferred range of the magnetic control driving force is: 4.5605*10 -4 N<F 磁控驱动力 <1.138*10 -2 N.

[0097] The hydrophilic magnet used in the present application is a magnetic material selected from one of a magnetic aluminum-nickel-cobalt material, a magnetic ferrite material and a magnetic neodymium-iron-boron alloy, and can be flexibly changed according to the use requirements, and the shape thereof can also be flexibly changed according to the use requirements, including but not limited to a cylinder, a sphere, a cube and the like. As a preferred scheme, the hydrophilic magnet used in the present application is a cylinder of a neodymium-iron-boron alloy material.

[0098] The present application provides a method for controlling the reciprocating flow of liquid based on magnetic force, which realizes stable and rapid control of liquid flow and can be applied to various microfluidic immune detection with low risk of aerosol pollution, such as enzyme-linked immune detection, fluorescent immune detection, chemiluminescent immune detection or localized surface plasmon resonance detection and the like. Unlike the existing magnetic control method which generates a pushing force by moving a magnet to move or disturb the liquid, the magnetic control method in the present application utilizes the interfacial capillary force between the hydrophilic magnet and the liquid to provide a traction force for the movement of the liquid before the hydrophilic magnet in the liquid is separated from the liquid, so as to realize the control of the liquid flow.

[0099] Example 2: A reciprocating flow device based on step motor control magnetic force

[0100] The present embodiment provides a device for realizing the control of the reciprocating flow of liquid based on magnetic force, and the schematic diagram of the device is as shown in Figure 2As shown, it comprises the following main structures: support base 1, microfluidic chip platform 11, magnetic control driving device 2, external controller 3 and microfluidic chip 4; the magnetic control driving device 2 comprises a stepper motor 21, a transmission rod 22 and a magnetic plate 23; the support base 1 is provided with the microfluidic chip platform 11 on the top, which is used for supporting the microfluidic chip 4, and the microfluidic chip platform 11 is placed above the components of the stepper motor 21, the transmission rod 22 and the magnetic plate 23; the stepper motor 21 is fixed on the support base 1, one end is mechanically connected with the transmission rod 22, and the other end is electrically connected with the external controller 3; the transmission rod 22 is parallel to the support base 1, and the other end is fixed with the magnetic plate 23.

[0101] The schematic diagram of the microfluidic chip 4 is as shown in the figure Figure 3 As shown, the microfluidic chip 4 is divided into three layers, including the bottom layer chip 41 as the substrate, the middle layer chip 42 providing microfluidic channels and the top layer chip 43 with holes; the middle layer chip 42 is provided with parallel microfluidic channels 421, and each microfluidic channel is pre-loaded with a hydrophilic magnet 422 for cooperating with magnetic force control;

[0102] Further, the size characteristics of the hydrophilic magnet are: the height is less than the height of the microfluidic channel, and the width is less than the width of the microfluidic channel.

[0103] The principle realized by the device of the application is: after the liquid is injected into the microfluidic channel, it will contact and wrap the hydrophilic magnet. The application moves the hydrophilic magnet 422 to the edge of the gas-liquid interface of the liquid; and tries to continue to move the hydrophilic magnet 422 outside the liquid to make it separate from the liquid. At this time, the hydrophilic magnet 422 breaks through the gas-liquid interface of the liquid, so that a gas / liquid / solid three-phase interface is formed on the surface of the hydrophilic magnet 422, which is specifically manifested as a solid / liquid contact line that surrounds the surface of the hydrophilic magnet 422. Subsequently, when the hydrophilic magnet 422 tries to continue to separate from the liquid, the change of the interfacial energy on the gas / liquid / solid three-phase interface will be caused; the change of the interfacial energy is further converted into the interfacial capillary force applied to the hydrophilic magnet 422 and the liquid at the same time on the solid / liquid contact line. For the liquid, the interfacial capillary force points to the outside of the liquid along the movement direction of the hydrophilic magnet 422, thereby serving as a traction force to drive the liquid to move along the movement direction of the hydrophilic magnet 422, realizing the control of the liquid flow. Simply speaking, the reciprocating flow control of the liquid is completed by moving the hydrophilic magnet 422 to drag the liquid to move.

[0104] The operation method of the device based on magnetic force control of reciprocating flow is as follows: the microfluidic chip 4 is placed above the microfluidic chip platform 11, and a liquid to be controlled is injected into the microfluidic channel 421 of the microfluidic chip 4; then the external controller 3 inputs motion parameters including motion speed, motion distance and motion cycle number to the stepping motor 21; the reciprocating flow device is started, and the stepping motor 21 drives the transmission rod 22 to move, so as to drive the magnetic plate 23 to move at a uniform speed and distance set in the external controller 3 from the starting position.

[0105] After the magnetic plate 23 moves at a uniform speed to the set motion distance, the stepping motor 21 drives the transmission rod 22 to move, so that the magnetic plate 23 moves at a uniform speed set in the external controller 3 to return to the starting position, so as to complete a motion cycle; the reciprocating flow device repeats the above operation in sequence, and the number of repetitions is equal to the number of motion cycles set in the external controller 3, so as to realize reciprocating flow control.

[0106] The embodiment also provides a manufacturing method of the microfluidic chip 4.

[0107] S1, three parallel long holes are made on the surface of a flat polymethyl methacrylate (PMMA) sheet by laser cutting, so as to obtain a middle layer chip 42; the long hole is composed of a square hole connected with two circular holes at both ends, wherein the diameter of the circular hole is 0.4 cm, the length of the square hole is 2.0 cm, and the width of the square hole is 0.2 cm;

[0108] S2, three groups of circular holes with a diameter of 0.4 cm are made on the surface of another flat PMMA sheet by laser cutting, so as to obtain a top layer chip 43;

[0109] S3, the flat bottom layer chip 41 (flat PMMA sheet), the middle layer chip 42 and the top layer chip 43 are bonded together under the condition of light irradiation by using photocuring glue as an adhesive, so as to obtain the microfluidic chip 4.

[0110] The flow process of the liquid controlled by the device is as follows: the assembled microfluidic chip 4 is placed on the microfluidic chip platform 11 of the reciprocating flow device, 40 μL of red water is added to the microfluidic channel 421 of the middle layer chip 42 through the circular hole on the top layer chip 43; then the external controller 3 inputs motion parameters including motion speed (3.11 mm / s), motion distance (2.0 cm) and motion cycle number to the stepping motor 21, and the reciprocating flow device is started to start flow control.

[0111] The results after flow control are as follows: Figure 4As shown, in the reciprocating flow process controlled by magnetic force, the hydrophilic magnet 422 does not push the liquid when moving inside the liquid. When the hydrophilic magnet 422 moves to the gas-liquid interface boundary of the liquid, it can pull the liquid in each channel to move at the same speed. When the hydrophilic magnet 422 stops moving, the liquid also stops moving immediately. The above process remains consistent in the flow control process in different flow directions.

[0112] The results show that the reciprocating flow method based on magnetic force control can realize the flow control of magnet dragging liquid movement instead of pushing or disturbing. In the control process, the movement of the liquid is smooth and fast, and there is no violent friction and oscillation of the gas-liquid interface; and no bubbles are generated to form a new gas-liquid interface, which proves that the method meets the requirement of reducing the probability of aerosol generation and has the ability to reduce the risk of aerosol pollution.

[0113] Embodiment 3: A reciprocating flow device based on array inductance controlled magnetic force

[0114] This embodiment provides a device for driving liquid reciprocating flow based on array inductance controlled magnetic force, and a schematic diagram of the device is as shown in Figure 5 As shown, it includes the following main structures: a support base 1, a microfluidic chip platform 11, a magnetic control driving device 2, an external controller 3 and a microfluidic chip 4. The magnetic control driving device 2 includes a circuit board 24 and an array inductance 25. The support base 1 is provided with the microfluidic chip platform 11 above, which is used to support the microfluidic chip 4. The microfluidic chip platform 11 is placed above the components of the circuit board 24 and the array inductance 25. The circuit board 24 is fixed on the support base 1, and the upper end is electrically connected with the array inductance 25, and one end is electrically connected with the external controller 3. The array inductance 25 is arranged in parallel with the support base 1, and the arrangement position corresponds to the position of the parallel microfluid channels 421 in the microfluidic chip 4. The inductances parallel to the direction of the microfluid channels 421 are connected in parallel, and the interval is as small as possible. The inductances perpendicular to the direction of the microfluid channels 421 are connected in series, and the interval is equal to the distance between the microfluid channels 421. The array inductance 25 is as small as possible under the condition of meeting the requirement of providing sufficient F 磁控驱动力 The array inductance 25 needs to be a non-shielded or semi-shielded inductance, specifically one of a winding type, a patch type and a woven type inductance.

[0115] The microfluidic chip 4 structure, manufacturing method, hydrophilic magnet selection, liquid control principle and parameters of this embodiment are the same as those of embodiment 2.

[0116] The operation method of the device based on magnetic force control of reciprocating flow is as follows: the microfluidic chip 4 is placed above the microfluidic chip platform 11, and a liquid to be controlled is injected into the microfluidic channel 421 of the microfluidic chip 4; then the external controller 3 inputs motion parameters including motion speed, motion distance and motion cycle number to the circuit board 24; the reciprocating flow device is started, and the circuit board 24 connects the array inductors 25 row by row according to the motion speed and distance set in the external controller 3 to generate a changing magnetic field, driving the hydrophilic magnet in the microfluidic channel 421 to move at a constant speed from the starting position to the forward direction;

[0117] After the hydrophilic magnet moves at a constant speed to the set motion distance, the circuit board 24 reversely connects the array inductors 25 row by row to generate a changing magnetic field, driving the hydrophilic magnet in the microfluidic channel 421 to move at a constant speed from the set speed in the external controller 3 to the backward direction and return to the starting position, so as to complete one motion cycle; the reciprocating flow device repeats the above operation in sequence, and the number of repetitions is equal to the number of motion cycles set in the external controller 3, so as to realize reciprocating flow control.

[0118] Example 4: Enzyme-linked immunoassay based on the reciprocating flow device based on magnetic force

[0119] 1. Preparation of a microfluidic chip for immunoassay:

[0120] S1. Partially coat goat anti-human IgG antibody on a flat PMMA sheet, and the size of the coated area is 0.2*0.4 mm, which corresponds to the middle position of the square hole on the middle layer chip 42, so as to obtain the bottom layer chip 41 coated with specific antibodies;

[0121] S2. Six parallel long holes are made on the surface of another flat PMMA sheet by laser cutting, so as to obtain the middle layer chip 42; the long hole is composed of a square hole connected with two circular holes at both ends, wherein the diameter of the circular hole is 0.4 cm, the length of the square hole is 2.0 cm, and the width is 0.2 cm;

[0122] S3. Six groups of circular holes are made on the surface of another flat plastic sheet by laser cutting, so as to obtain the top layer chip 43 with a diameter of 0.4 cm;

[0123] S4. Use light-cured glue as an adhesive to bond the bottom layer chip 41, the middle layer chip 42 and the top layer chip 43 together under light, and assemble to obtain the microfluidic chip 4.

[0124] 2. Enzyme-linked immunoassay for detecting human IgG:

[0125] (1) Sample capture. The magnetic reciprocating flow device based on the present application was used, and 40 μL of human IgG solution was added to the microfluidic channel 421 in the top layer hole of the top layer chip 43 on the microfluidic chip 4, and then the external controller 3 (the motion parameter settings of the reciprocating flow control were the same as in Example 1) was set to start the reciprocating flow device, so that the sample solution reciprocated for 5 cycles, and then the sample solution was discharged.

[0126] (2) Sample solution washing. 40 μL of washing solution was added to the microfluidic channel 421 in the top layer hole of the top layer chip 43, and then the reciprocating flow device was started to make the washing solution unidirectionally flow and be discharged; the washing solution was a phosphate buffer solution containing Tween-20. The washing was repeated 3 times.

[0127] (3) Second antibody capture. Then, 40 μL of horseradish peroxidase-labeled rabbit anti-human IgG antibody solution was added to the microfluidic channel 421 in the top layer hole of the top layer chip 43. The reciprocating flow device was started to make the second antibody solution reciprocate for 5 cycles, and then the second antibody solution was discharged.

[0128] (4) Second antibody solution washing. 40 μL of washing solution (the composition of the washing solution was the same as in (2) above) was added to the microfluidic channel 421 in the top layer hole of the top layer chip 43, and then the reciprocating flow device was started to make the washing solution unidirectionally flow and be discharged. The washing was repeated 3 times.

[0129] (5) Result detection. 40 μL of color developing solution was added to the microfluidic channel 421 in the top layer hole of the top layer chip 43, and the reciprocating flow device was started to make the color developing solution flow for 5 cycles. Then, 20 μL of stopping solution was added to the microfluidic channel 421 in the top layer hole of the top layer chip 43, and the reciprocating flow device was started to make the color developing solution flow for 5 cycles. The color of the liquid in each channel was analyzed to obtain the detection result.

[0130] The qualitative detection result of the enzyme-linked immunoassay using the reciprocating flow device is shown in Figure 6 . The left side of Figure 6 is a physical diagram of the qualitative detection result, and the information in the diagram includes 6 parallel microfluidic channels, of which the left three microfluidic channels are the detection channels of negative samples, and the right three microfluidic channels are the detection channels of positive samples. Obviously, the color results in the negative sample detection channels and the positive sample detection channels have strong distinguishability, which can be effectively applied to qualitative detection. The color data of these detection channels were extracted and classified and compared according to the sample type, which is the histogram on the right side of Figure 6 . According to the histogram, the color gray scale of the negative samples and the positive samples is obviously different, which further proves that the negative and positive results have strong distinguishability, indicating that the detection method in this embodiment can be effectively applied to the qualitative detection of distinguishing negative and positive samples.

[0131] The results of the quantitative detection using the reciprocating flow device for enzyme-linked immunoassay are shown in Figure 7 . Figure 7 The left image is a real image of the quantitative detection results, and the information contained in the image includes six parallel microchannels, which are the detection channels of the blank sample and IgG samples with different concentrations from left to right, and the concentrations are arranged in ascending order. Obviously, the color results in the six detection channels are enhanced with the increase of the IgG concentration in the sample, indicating that the detection method in this embodiment can provide visual results for quantitative detection. The color data of these detection channels are extracted, and the change of the color intensity with the sample concentration is analyzed and fitted, that is, Figure 7 the linear fitting curve on the right. According to the curve, the detection results of different concentrations of positive samples in this embodiment have a clear linear relationship with the concentration, which can be effectively applied to quantitative detection.

[0132] Example 5 Fluorescent immunoassay based on the magnetic reciprocating flow device

[0133] The fluorescent immunoassay based on the magnetic reciprocating flow device of Example 3 is used, and the preparation of the microfluidic chip 4 for immunoassay is the same as that of Example 2. The capture of the sample to be tested for human IgG, the washing of the sample solution, and the capture operation method of the second antibody using the reciprocating flow device are the same as those of Example 4. Subsequently, 40 μL of fluorescent microsphere-labeled rabbit anti-human IgG antibody solution is added to the microfluidic channel from the top layer sample addition hole of the top layer chip 43, and the reciprocating flow device is started to make the second antibody solution reciprocate for 5 cycles, and then the second antibody solution is discharged. The washing of the second antibody solution is performed in the same manner as in Example 2, and the processed microfluidic chip 4 is placed in an ultraviolet dark box, and the detection results are analyzed according to the fluorescence intensity in the coated area.

[0134] The results of the qualitative detection using the reciprocating flow device for fluorescent immunoassay are shown in Figure 8 . Figure 8 is a real image of the bottom layer chip after the microfluidic chip described in this embodiment completes the fluorescent detection, and the results of the fluorescent detection should appear in the middle part of each detection channel, i.e. the area between each group of relatively round holes. Among them, the microfluidic channel between the three groups of round holes on the left carries out the detection of the negative sample, and there is no obvious fluorescent spot mark in the middle part of the detection channel; relatively, the microfluidic channel between the three groups of round holes on the right carries out the detection of human IgG with concentrations of 7.3, 73 and 730 ng / mL, respectively, and there are visible fluorescent spot marks in the middle part of the detection channel, and the fluorescence intensity changes significantly with the increase of the concentration of human IgG. The results show that there is a strong distinction between the results of the negative sample, the results of the low-concentration positive sample and the results of the high-concentration positive sample in this embodiment, which can effectively carry out immunoassay.

[0135] In summary, the reciprocating flow method and device based on magnetic force control provided by the application can be applied to various microfluidic immunoassays. The interfacial capillary force generated by the gas / liquid / solid three-phase interface formed by the hydrophilic magnet before the liquid is separated is used as the traction force for the movement of the liquid, the flow control of the liquid is realized, the non-contact flow control is realized, the pollution caused by the contact control (such as mechanical probe control) can be avoided; at the same time, the liquid moves smoothly and quickly, no bubbles and new gas-liquid interfaces are generated, the violent friction and vibration on the gas-liquid interface are avoided, and the probability of aerosol generation is reduced; compared with the existing magnetic control mode of moving or disturbing the liquid by pushing force, the aerosol pollution risk is greatly reduced. In addition, the microfluidic immunoassay using the device provided by the application only needs 1-2 minutes for one round of antigen-antibody combination and only needs 5-15 minutes for one detection, and the detection speed is much faster than that of the traditional immunoassay method based on reaction cup or microplate.

[0136] The above embodiments are preferred embodiments of the application, but the embodiments of the application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the application shall be equivalent replacement modes and shall be included in the protection scope of the application.

Claims

1. A method of controlling the reciprocating flow of a liquid based on magnetic force, characterized by, Hydrophilic magnets are added to the liquid to be tested, and the hydrophilic magnets are controlled to drag the liquid to move in a state of not completely separating from the liquid by an external magnetic field, so that the reciprocating flow of the liquid can be controlled; wherein the gas / liquid / solid three-phase interface capillary force formed by the hydrophilic magnets on the edge surface of the gas-liquid interface of the liquid serves as the driving force for the movement of the liquid, and the liquid sliding friction, the liquid surface tension, the magnetic control driving force generated by the external magnetic field, and the magnet sliding friction need to meet the following force conditions: ； ； 。 2. The method of claim 1, wherein, The hydrophilic magnet is a magnetic material selected from one of a magnetic aluminum-nickel-cobalt material, a magnetic ferrite material, and a magnetic neodymium iron boron alloy.

3. A reciprocating flow device based on magnetic force control, characterized by, The device for implementing the method of claim 1 or 2 comprises a support base (1), a microfluidic chip platform (11), a magnetic control driving device (2), an external controller (3), and a microfluidic chip (4); the support base (1) is provided above with the magnetic control driving device (2), the microfluidic chip platform (11), and the microfluidic chip (4), and the microfluidic chip platform (11) is arranged on both sides of the support base (1) to support the microfluidic chip (4); the magnetic control driving device (2) is fixed on the support base (1) and electrically connected to the external controller (3) at one end; the microfluidic chip (4) comprises a bottom chip (41) as a substrate, a middle chip (42) provided with micro flow channels, and a top chip (43) provided with holes; the middle chip (42) is provided with parallelly arranged micro flow channels (421), and each micro flow channel contains a hydrophilic magnet (422) for cooperating with magnetic force control.

4. The apparatus of claim 3, wherein, The magnetic control driving device (2) comprises a stepping motor (21), a transmission rod (22), and a magnetic plate (23); the stepping motor (21), the transmission rod (22), and the magnetic plate (23) are arranged above the support base (1); the stepping motor (21) is fixed on the support base (1) and mechanically connected to the transmission rod (22) at one end and electrically connected to the external controller (3) at the other end; the transmission rod (22) is arranged in parallel with the support base (1) and fixed with the magnetic plate (23) at the other end.

5. The apparatus of claim 3 wherein, The magnetic control driving device (2) comprises an array of inductors (25) and a circuit board (24) connected to the inductors; the support base (1) is provided above with the circuit board (24), and the circuit board (24) is connected above with the array of inductors (25) in a power connection manner; the circuit board (24) is fixed on the support base (1) and electrically connected to the external controller (3) at one end; the array of inductors (25) is arranged in parallel with the support base (1), and the array of inductors (25) is arranged at positions corresponding to the positions of the parallelly arranged micro flow channels (421) in the microfluidic chip (4), the inductors parallel to the direction of the micro flow channels (421) are connected in parallel, the inductors perpendicular to the direction of the micro flow channels (421) are connected in series, and the interval between the array of inductors (25) is equal to the interval distance between the micro flow channels (421).

6. The apparatus of claim 3, wherein The height of the hydrophilic magnet (422) is less than the height of the micro flow channel (421), and the width of the hydrophilic magnet (422) is less than the width of the micro flow channel (421).

7. A method of controlling the reciprocating flow of a liquid based on the apparatus of any one of claims 3 to 6, characterized in that, Specifically includes the following steps: S1, placing the microfluidic chip (4) above the microfluidic chip platform (11); S2, inject the liquid to be controlled into the microfluidic channel (421) of the microfluidic chip (4); S3, input the motion parameters including the motion speed, motion distance and motion cycle number into the magnetic control driving device (2) through the external controller (3); S4, start the reciprocating flow device, and make the hydrophilic magnet (422) in the microfluidic chip (4) move at a constant speed from the starting position to the forward direction under the action of the magnetic control driving force, the motion distance being equal to the motion distance set in S3; S5, after the hydrophilic magnet (422) in the microfluidic chip (4) moves at a constant speed to the set motion distance, the hydrophilic magnet (422) is driven by the magnetic control driving device (2) to move at a constant speed back to the starting position at the speed set in S3, so as to complete one motion cycle; S6, repeat the steps of S4 and S5 in sequence, the repeating number being equal to the motion cycle number set in S3, so as to realize the reciprocating flow control.

8. The application of the method of claim 1 or 2, or the device of any one of claims 3-6 in liquid control, immune detection, nucleic acid detection and biological particle detection.

9. An immunoassay method characterized in that, The detection is performed by using the device of any one of claims 3-6 or the method of claim 7, and specifically includes the following steps: S1, prepare the microfluidic chip (4), coat specific antibodies or antigens on the microfluidic channel (421) of the middle layer chip (42) corresponding to the bottom chip (41), and place the prepared microfluidic chip (4) above the microfluidic chip platform (11); S2, inject the sample solution to be detected into the microfluidic channel (421) of the microfluidic chip (4); S3, set the motion parameters of the external controller (3), input the magnetic control driving device (2), start the reciprocating flow device, and make the stepping motor (21) drive the transmission rod (22) to drive the magnetic plate (23) to move, or make the circuit board (24) sequentially connect the array inductors (25) to generate a changing magnetic field, so that the hydrophilic magnet (422) in the microfluidic chip (4) moves at a constant speed from the starting position to the forward direction, the motion distance being equal to the motion distance set in S3; after the hydrophilic magnet (422) in the microfluidic chip (4) moves at a constant speed to the set motion distance, the hydrophilic magnet (422) is driven by the magnetic control driving device (2) to move at a constant speed back to the starting position at the speed set in S3, so as to complete one motion cycle; S4, set the steps of S2 and S3 to be repeated in sequence according to the detection method, the repeating number being equal to the motion cycle number set in S3, so as to realize the reciprocating flow control and perform the detection.

10. The method of claim 9, wherein, In step S2, the sample solution to be detected is added into the microfluidic channel (421) from the top layer hole of the top layer chip (43) of the microfluidic chip (4), and the capture of the sample to be detected, the washing of the sample solution, the capture of the second antibody and the washing of the second antibody solution are performed in sequence, and the reciprocating flow device is started to perform the detection.

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