Micro-fluidic chip and method based on pressing driving fluid

Abstract

The invention belongs to the technical field of micro-fluidic chips, and particularly discloses a micro-fluidic chip based on pressing driving fluid, which comprises a micro-fluidic chip body and a pressing driving pump matched with the micro-fluidic chip body, the micro-fluidic chip body comprises a liquid storage layer and a bottom plate which are stacked up and down, and the liquid storage layer is connected with a pressing driving pump; a first opening is formed in the pressing driving pump, the first opening is matched with a second opening formed in the upper surface of the liquid storage layer through a pump cavity formed in the pressing driving pump, and the second opening communicates with a serpentine channel liquid storage cavity formed in the lower surface of the liquid storage layer through a liquid storage through hole penetrating through the liquid storage layer; an N-shaped capillary explosion valve is arranged at one end, far away from the liquid storage through hole, of the serpentine channel liquid storage cavity; according to the invention, a fluid driving mode which is simple in mode, controllable in fluid and independent of external equipment can be realized, and the influence of the external driving equipment on the active microfluid driving system can be obviously reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of microfluidic chips, and in particular relates to a microfluidic chip based on pressure-driven fluid, and also relates to a method for the microfluidic chip based on pressure-driven fluid. Background Art

[0002] Current microfluidic driving methods are divided into two types: passive and active. Passive fluid driving mainly relies on self-driving forces such as capillary action, inertial force, and viscous force. It does not require input from an external source and has the advantages of simple structure and low cost. It is suitable for simple and low-cost detection scenarios. Active fluid driving requires an external power source to drive the fluid. Common driving methods include pressure drive, centrifugal drive, electric drive, thermal drive, etc. Its advantage is that it can achieve more precise and controllable fluid manipulation, which is suitable for complex applications of fine fluid management.

[0003] In 2006, Zimmermann et al. realized self-driving of fluid in microfluidic devices by designing capillary microstructures for ELISA assays. However, this method is prone to generate bubbles during the detection process, affecting the accuracy of the detection; Rocca et al. developed a new capillary-driven microfluidic chip in 2021, which can perform quantitative glucose-6-phosphate dehydrogenase and hemoglobin detection using trace samples within 2 minutes. However, the passive driving structure is complex in design, the flow state is poorly uniform, and bubbles are easily generated, making it impossible to achieve continuous differentiated control of the flow rate in the fluid channel; Jeong et al. proposed thermal driving technology in 2005, which heats the elastic thin film by heating the gas. Membrane deformation drives fluid movement; Xiao et al. proposed a fully integrated automated centrifugal microfluidic chip in 2024, which uses centrifugal force to drive fluid to achieve instant multiple molecular diagnosis; in addition, Uvarov et al. described an electrically driven micropump in 2021, which uses three peristaltic thin film actuators to drive AP electrolysis using microsecond voltage pulses; although the above active micropumps can achieve precise control of fluids, they all rely on external driving devices to operate, which increases the complexity of the system, and complex external driving devices will affect the use of active microfluidic drives in complex environments, affecting the popularity and practicality of portable POCT (point-of-care testing) technology in different application scenarios. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a microfluidic chip and method based on pressure-driven fluid, which has a fluid control effect, does not rely on external equipment, and has a simple structure.

[0005] Based on the above purpose, the present invention is achieved through the following technical solutions:

[0006] A microfluidic chip based on pressure-driven fluid comprises a microfluidic chip body and a pressure-driven pump matched with the microfluidic chip body; the microfluidic chip body comprises a liquid storage layer and a bottom plate stacked up and down, and the liquid storage layer is connected to the pressure-driven pump; a first opening is provided on the pressure-driven pump, the first opening is matched with a second opening arranged on the upper surface of the liquid storage layer through a pump cavity arranged in the pressure-driven pump, the second opening is connected with a serpentine channel liquid storage cavity arranged on the lower surface of the liquid storage layer through a liquid storage through hole penetrating the liquid storage layer, and an N-type capillary burst valve is provided at one end of the serpentine channel liquid storage cavity away from the liquid storage through hole.

[0007] Preferably, a liquid storage hole is provided at one end of the N-type capillary burst valve away from the serpentine channel liquid storage cavity, and the liquid storage hole is connected with a connected third opening arranged on the lower surface of the bottom plate through a bottom plate through hole arranged on the bottom.

[0008] Preferably, the press-driven pump comprises a hemispherical shell, a press sleeve is provided on the hemispherical shell, and the first opening is arranged at the center of the press sleeve.

[0009] Preferably, the height of the serpentine channel liquid storage chamber and the N-type capillary burst valve is 90um~110um, 100um, the width of the serpentine channel liquid storage chamber is 0.90mm~1.10mm, 1mm, the total length of the serpentine channel liquid storage chamber is 38mm~42mm, 40mm, and 4ul of liquid can be stored in a size of 40mm; the liquid storage capacity can be increased by increasing the length of the serpentine channel liquid storage chamber.

[0010] Preferably, the contraction width of the N-type capillary bursting valve is 25um, and the N-type structure increases the fluid resistance and improves the performance of the capillary bursting valve; when a pressure of 3250pa is applied at the second opening, the N-type capillary bursting valve successfully prevents the flow of liquid. When the pressure is greater than this pressure, the N-type capillary bursting valve will be broken through and the fluid will be driven.

[0011] Preferably, the press-actuated pump is made by casting PDMS material. First, a mold of the press-actuated pump needs to be made. The mold includes two layers, a base and a cover plate. After the mold is printed using photocuring printing technology, it is cleaned with isopropyl alcohol to remove uncured resin on the surface, and finally placed in an ultraviolet environment for curing for ten minutes to improve the printing quality.

[0012] Preferably, the deformation resistance of the push-driven pump is affected by the curing agent; by stretching three PDMS samples with a PDMS: curing agent ratio of 1:10, 1:15 and 1:20 to measure their deformation, the stress-strain curve shows that the elastic modulus of PDMS can be changed by the curing agent, and considering the operational friendliness and the structural strength of the pump, PDMS: curing agent of 1:15 is selected as the best ratio for the production of the PDMS push-driven pump. The production of the PDMS push-driven pump includes the following steps: first, take an appropriate amount of PDMS on the base mold, cover the cover mold, gently press the cover to make the PDMS flow out from the gap between the base and the cover, then put it into an oven and bake it at 65 degrees Celsius for 2 hours, and finally demold it.

[0013] A method for a microfluidic chip comprises the following steps: S1, preparation of a pressure-driven pump; S2, preparation of a microfluidic chip body; S3, assembly of the microfluidic chip; S4, use of the microfluidic chip.

[0014] Preferably, in step S1, the preparation of the pressure-driven pump comprises the following steps:

[0015] S101, drawing and printing of a press drive pump mold;

[0016] The press-actuated pump mold is configured to be composed of a base and a cover plate, and the base and cover plate of the press-actuated pump mold are drawn using modeling software, and the base and cover plate of the press-actuated pump mold are printed using printing technology. After printing, the base and cover plate are cleaned with isopropyl alcohol to remove uncured resin on the surface of the base and cover plate, and then placed in an ultraviolet environment for curing for 10 minutes to ensure the final quality of the press-actuated pump mold;

[0017] S102, evaluating the mixture ratio of the curing agent and the PDMS prepolymer;

[0018] In step S102, the effect of different curing agent ratios on the deformation resistance of the press-driven pump is first evaluated, and the selected mixture ratios for evaluation are 1:10, 1:15 and 1:20, respectively. Mixtures of curing agent and PDMS prepolymer are prepared using the above ratios; these mixtures are made into 180 μm thick PDMS samples and heated at 60°C for 2 h; the deformation of the PDMS sample is measured by stretching, thereby obtaining the stress-strain curve of each sample. The results of the stress-strain curve show that the elastic modulus of PDMS can be changed by adjusting the curing agent ratio. The lower the elastic modulus, the softer the material, and vice versa.

[0019] Considering the user-friendly operation, the driving force of the push-actuated pump needs to be as small as possible to reduce the burden. Although the 1:20 PDMS sample is soft and easy to compress, its structural strength is insufficient and it is easy to be damaged. Therefore, a 1:15 ratio of curing agent to PDMS prepolymer is selected as the optimal ratio for the push-actuated pump.

[0020] S103, casting and molding of a press-driven pump;

[0021] According to the mixture ratio selected in step S102, the curing agent and the PDMS prepolymer are mixed at a ratio of 1:15, and the mixed mixture is injected into the press-driven pump mold assembled with the base and the cover plate, and placed in a 0.8Mpa vacuum hood for 15 minutes to remove bubbles; then the cast press-driven pump mold is placed in a 60°C oven for curing for 2 hours. After curing, the base and the cover plate of the press-driven pump mold are separated, and the cured press-driven pump is taken out.

[0022] Preferably, in step S2, the preparation of the microfluidic chip body comprises the following steps:

[0023] S201, making a microfluidic chip body mold;

[0024] The manufacturing process of the SU-8 mold with a thickness of 100 μm includes the following steps:

[0025] S2011, mask production;

[0026] The designed microstructure of the liquid storage layer of the microfluidic chip is drawn into a two-dimensional drawing using AutoCAD software, which is then made into a film mask by the processor; the positive and negative phases of the photoresist are the key to determining the mask processing and microstructure formation characteristics; negative photoresist is used, which is opposite to the positive photoresist that is soluble under ultraviolet light. After exposure, the negative photoresist area remains insoluble, making the corresponding part of the mask channel transparent, causing the photoresist to solidify and cross-link, forming the desired microfluidic channel structure.

[0027] S2012, pretreatment of silicon wafer;

[0028] Before preparing the SU-8 mold, it is usually necessary to pre-treat the silicon wafer to ensure that its surface is clean and dry; after cleaning the surface of the silicon wafer with isopropanol, drying it in a 60°C oven for 10 minutes can effectively remove impurities, oil stains and other pollutants and improve the hydrophilicity of its surface.

[0029] S2013, spin coating SU-8 photoresist;

[0030] Add an appropriate amount of SU-82050 negative photoresist on the pre-treated silicon wafer, then place the silicon wafer on the tray in the center of the coating machine and fix it with a vacuum pump to prevent the silicon wafer from shifting during the spin coating process; use a multi-step spin coating method, with the first step at a speed of 500 rpm and the second step at 200 rpm. 2 Spin coating for 20 seconds at an acceleration to help the photoresist spread to form an initial film; the second step is at a speed of 1700 rpm and 300 rpm 2 Spin coating for 30 seconds under acceleration. The spin coating parameters in this step determine the thickness of the photoresist. After spin coating, let it stand for a while to make the surface flat.

[0031] S2014, pre-baking;

[0032] Use a precisely temperature-controlled HP10 adhesive baker for heating to ensure that the photoresist adheres evenly to the silicon wafer and improve its mechanical stability; first bake the silicon wafer at 65°C for 4 minutes, and then continue to bake at 95°C for 16 minutes; after baking, take out the silicon wafer and cool it to room temperature. If there is any wrinkling, put it back in the adhesive baker; through repeated cooling and heating processes, ensure that the surface of the silicon wafer is smooth and wrinkle-free.

[0033] S2015, exposure;

[0034] After the silicon wafer has cooled to room temperature, it is exposed using a H94-27 (LED) microfluidic chip processing device. The device uses UVLED as a light source and has no infrared radiation, which helps to avoid the expansion and contraction of the film. The operating steps include placing the translucent plate on the plate holder, starting the vacuum pump and fixing it using the "plate suction" button on the operation interface. Subsequently, the wafer stage is pulled out, the silicon wafer and mask are placed in turn, and the silicon wafer is fixed on the wafer stage using the "film suction" button. After the wafer stage is pushed into the extreme position, the exposure time is precisely controlled to 23 seconds according to the SU-8 thickness and mold structure requirements. Next, the "stage lift", "contact" and "exposure position" buttons on the operation interface are pressed to start the exposure process.

[0035] S2016, post-baking;

[0036] After the exposure is completed, the silicon wafer is placed in the glue drying machine again to further cross-link and cure the photoresist, thereby improving the mechanical properties and stability of the mold; the time and temperature of the post-baking need to be adjusted according to the thickness and structure of the mold; first, bake the silicon wafer at 65°C for 2 minutes, then bake at 95°C for 9 minutes, and finally wait for the silicon wafer to cool to room temperature.

[0037] S2017, development;

[0038] SU-8 negative photoresist is used. The negative photoresist undergoes a curing and cross-linking reaction in the UV-exposed area, while the unexposed area remains uncured. Subsequently, the silicon wafer that has been cooled after post-baking is placed in a developer to dissolve the unexposed part, revealing a microchannel structure pattern. The developing time varies depending on the type and thickness of the photoresist. Usually, the processed silicon wafer is placed in a glass culture dish containing a developer and rinsed for 8 minutes. Then, isopropyl alcohol is used to clean the excess developer on the surface of the silicon wafer. Finally, the surface of the silicon wafer is blown dry to obtain a preliminary SU-8 mold.

[0039] S2018, hard baking;

[0040] High-temperature hard baking treatment is used to improve the durability and stability of the SU-8 mold, which can enhance the degree of cross-linking inside the SU-82050 photoresist; the developed silicon wafer is placed in a 220°C glue baking machine and baked for 3 minutes to obtain a solid SU-8 mold, providing stable conditions for subsequent chip production.

[0041] S202, fabrication of microfluidic chip body;

[0042] PDMS is a silicon-based organic polymer with excellent optical transparency, flexibility and elastomeric properties. It is widely used in fields such as tissue engineering and biomedicine due to its unique biocompatibility. In addition, PDMS can be made into various microscale and nanoscale structures through a simple casting process. The combination with soft lithography technology has enabled PDMS to achieve extensive development in the fields of micromanufacturing and microfluidic device design.

[0043] After the SU-8 mold is prepared, the PDMS material is poured into the mold for curing to replicate the microchannel structure on the mold surface, which is called the PDMS casting method. Using the SYLGARDTM 184Silicone Elastomer Kit model PDMS, the PDMS and curing agent are first mixed in a mass ratio of 10:1 and stirred thoroughly until full of bubbles. The SU-8 mold is fixed to the bottom of the culture dish by using double-sided tape, and then the mixed PDMS is poured into the culture dish, placed in a 0.8Mpa vacuum cover and allowed to stand for about 15 minutes to remove bubbles. Finally, the culture dish is placed in a 60°C oven and heated for 2 hours to cure the PDMS. After the curing is completed, a scalpel is used to cut and uncover the required area to obtain a PDMS microfluidic chip with a microchannel groove reservoir layer and a bottom plate on the surface.

[0044] The upper liquid reservoir layer and the lower bottom plate are encapsulated by oxygen plasma bonding process; before bonding, a 1mm punch is used to punch the second opening of the liquid reservoir through hole on the liquid reservoir layer, and then transparent tape is used to repeatedly stick the surface to clean it, and then the liquid reservoir layer and the bottom plate are placed in the oxygen plasma equipment respectively, and oxygen plasma treatment is performed for 100s; PDMS is usually hydrophobic, and oxygen plasma treatment can introduce active groups, such as hydroxyl (-OH), carboxyl (-COOH), etc. These active groups can increase the polarity of the PDMS surface and enhance its interaction with other polar surfaces, thereby improving adhesion and achieving bonding on both sides, and finally completing the production of the PDMS microfluidic chip body.

[0045] Preferably, in step S3, the assembly of the microfluidic chip includes the following steps: after the preparation of the push-driven pump and the microfluidic chip body is completed, the microfluidic chip body and the push-driven pump are cleaned with isopropanol and deionized water respectively to remove impurities and dust on the surfaces of the two, and the microfluidic chip body and the push-driven pump are accurately aligned immediately after oxygen plasma treatment for 100s, and lightly pressed to bond them into a chip as a whole, thereby completing the assembly of the microfluidic chip;

[0046] In step S4, the use of the microfluidic chip includes the following steps: first, use a pipette to take an appropriate amount of solution and add it to the serpentine channel liquid storage cavity through the first opening, the pump cavity, the second opening, and the liquid storage through hole, close the first opening, and then squeeze and press the drive pump with your fingers to deform the pump body, drive the fluid in the serpentine channel liquid storage cavity to break through the N-type capillary burst valve, and realize controllable drive of the fluid. The flow rate of the fluid is related to the pressure and frequency of the pressing. The fluid that breaks through the N-type capillary burst valve flows out along the liquid storage hole and the bottom plate through hole; multiple integrated use of the microfluidic chip based on the press-driven fluid can be applied to enzyme-linked immunosorbent assay, for example, three such microfluidic chips based on the press-driven fluid are integrated into one chip for use, and the analyte solution to be detected, the enzyme-labeled antibody solution and the colorimetric substrate solution are added to the three serpentine channel liquid storage cavities respectively; pumping the three solutions in sequence can perform enzyme-linked immunosorbent assay.

[0047] Preferably, in step S4, the approximate calculation function of the fluid flow rate is,

[0048] Q = f·ΔV;

[0049] Wherein, Q represents the flow rate of the pressure-driven pump; f represents the pressing frequency; ΔV represents the deformation of the pressure-driven pump during extrusion;

[0050] Assuming that the pressure on the pressure-driven pump is uniform, the calculation function of the deformation variable ΔV of the pressure-driven pump is:

[0051]

[0052] Wherein, e is the logarithm of the natural base; E represents the elastic modulus of the push-driven pump; P represents the applied pressure; V0 represents the initial volume of the pump cavity; when the applied pressure increases, the deformation of the push-driven pump will also increase, and the rate of increase will gradually decrease.

[0053] Preferably, in step S4, the pressure barrier of the N-type capillary bursting valve depends on the changes in the surface tension of the fluid, the contact angle and the shape of the N-type capillary bursting valve channel. Since the cross section of the N-type capillary bursting valve channel is rectangular, the bursting pressure P of the N-type capillary bursting valve is CBV The calculation function is:

[0054]

[0055] Where γ1 represents the surface tension of the fluid; θ l represents the contact angle between the fluid and the left side of the N-type capillary burst valve channel; θ r represents the contact angle between the fluid and the right side of the N-type capillary burst valve channel; θ t Represents the contact angle between the fluid and the top of the N-type capillary burst valve channel; θ b represents the contact angle between the fluid and the bottom of the N-type capillary burst valve channel; w and h represent the width and depth of the N-type capillary burst valve channel, respectively;

[0056] Since the N-type capillary burst valve channel uses the same material, it has the same contact angle, so the burst pressure P CBV The calculation function is further simplified to:

[0057]

[0058] Among them, θ c is the contact angle between the fluid and the channel of the N-type capillary burst valve.

[0059] A microfluidic chip and method based on pressure-driven fluid, comprising the following steps:

[0060] Step 1: After bonding the press-actuated pump, the liquid storage layer and the base plate using plasma technology, bake them at 70 degrees Celsius for 20 minutes to improve the bonding quality.

[0061] Step 2: Use a pipette to inject 40ul of liquid from the second opening into the serpentine channel storage chamber.

[0062] Step 3: After the injection is completed, the pump is driven by squeezing and pressing to deform the pump body, thereby driving the liquid in the serpentine channel liquid storage chamber to break through the bursting pressure of the N-type capillary bursting valve, thereby realizing controllable driving of the fluid. The flow rate is related to the pressure and frequency of finger pressing.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] (1) The present invention can drive the microfluid in a complex environment without the need for an external driving device. The microfluid can be driven by pressing the pump to generate deformation through finger squeezing. The press-driven pump adopts a press-driven design so that it does not require an external power supply or a complex control system, which is conducive to the integration and miniaturization of the equipment, and is particularly suitable for portable equipment or on-site rapid detection.

[0065] (2) The present invention adopts an N-type capillary bursting valve and a serpentine channel liquid storage chamber to achieve the storage of 4ul of liquid. The N-type capillary bursting valve is connected to the end of the serpentine channel liquid storage chamber. Compared with the capillary bursting valve of conventional structure, the N-type capillary bursting valve of the present invention can further increase the flow resistance of the fluid, increase the bursting pressure by 600Pa, and improve the liquid storage performance by 22.6%. The liquid storage capacity can also be increased by superimposing N-type capillary bursting valves and increasing the length of the serpentine channel liquid storage chamber.

[0066] (3) The present invention squeezes the press-driven pump by fingers, causing the pump body of the press-driven pump to deform, thereby causing the fluid in the serpentine channel liquid storage chamber to break through the bursting pressure of the N-type capillary bursting valve, so that the fluid is pumped out from the third opening, thereby realizing a fluid driving method that is simple, fluid-controllable, and independent of external devices, which can significantly reduce the impact of external driving devices on the active microfluidic driving system and improve the popularity and practicality of the active microfluidic driving system in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the decomposition structure of the present invention;

[0068] Figure 2 Schematic diagram of the combined structure of the liquid channel layer;

[0069] Figure 3 It is a schematic diagram of the structure of the liquid storage layer;

[0070] Figure 4 is a schematic diagram of the structure of the base plate;

[0071] Figure 5 It is a schematic diagram of the structure of the driving pump mold;

[0072] Figure 6 Schematic diagram of stress-strain curve of PDMS under different proportions of curing agent;

[0073] Figure 7 Schematic diagram of the simulated bursting pressure of the conventional structure (a) and the N-type capillary bursting valve (b).

[0074] In the figure, there is a pressure-driven pump 1, a liquid storage layer 2, a bottom plate 3, a first opening 4, a second opening 5, a third opening 6, a cover plate 7, a base 8, a liquid storage through hole 9, a serpentine channel liquid storage cavity 10, a liquid storage hole 11, an N-type capillary burst valve 12, and a bottom plate through hole 13. DETAILED DESCRIPTION

[0075] The present invention is further described in detail below through specific examples, but the scope of the present invention is not limited thereto.

[0076] Example 1

[0077] A microfluidic chip based on pressure-driven fluid, the structure of which is as follows Figure 1-Figure 4 As shown, it includes a microfluidic chip body and a press-driven pump 1 matched with the microfluidic chip body; the microfluidic chip body includes a liquid storage layer 2 and a bottom plate 3 stacked up and down, and the liquid storage layer 2 is connected to the press-driven pump 1; the press-driven pump 1 is provided with a first opening 4, and the first opening 4 is matched with a second opening 5 arranged on the upper surface of the liquid storage layer 2 through a pump cavity arranged in the press-driven pump 1, and the second opening 5 is connected with a serpentine channel liquid storage cavity 10 arranged on the lower surface of the liquid storage layer 2 through a liquid storage through hole 9 penetrating the liquid storage layer 2, and an N-type capillary burst valve 12 is provided at one end of the serpentine channel liquid storage cavity 10 away from the liquid storage through hole 9.

[0078] The N-type capillary burst valve 12 is provided with a liquid storage hole 11 at one end away from the serpentine channel liquid storage chamber 10, and the liquid storage hole 11 is connected to the third opening 6 provided on the lower surface of the bottom plate 3 through a bottom plate through hole 13 provided on the bottom. The press-driven pump 1 includes a hemispherical shell, a press sleeve is provided on the hemispherical shell, and the first opening 4 is provided at the center of the press sleeve. The height of the serpentine channel liquid storage chamber 10 and the N-type capillary burst valve 12 is 90um~110um, 100um, the width of the serpentine channel liquid storage chamber 10 is 0.90mm~1.10mm, 1mm, and the total length of the serpentine channel liquid storage chamber 10 is 38mm~42mm, 40mm.

[0079] A method for a microfluidic chip, comprising the following steps: S1, preparation of a pressure-driven pump 1; comprising the following steps;

[0080] S101, drawing and printing the mold of the press drive pump 1;

[0081] like Figure 5As shown, the mold of the press-actuated pump 1 is configured as two parts, namely, a base 8 and a cover plate 7. The base 8 and the cover plate 7 of the mold of the press-actuated pump 1 are drawn using modeling software, and the base 8 and the cover plate 7 of the mold of the press-actuated pump 1 are printed using printing technology. After printing, the base 8 and the cover plate 7 are cleaned with isopropyl alcohol to remove the uncured resin on the surface of the base 8 and the cover plate 7, and then placed in an ultraviolet environment for curing for 10 minutes to ensure the final quality of the mold of the press-actuated pump 1.

[0082] S102, evaluating the mixture ratio of the curing agent and the PDMS prepolymer;

[0083] In step S102, the influence of different curing agent ratios on the deformation resistance of the press-driven pump 1 is first evaluated. The selected mixture ratios for evaluation are 1:10, 1:15 and 1:20, respectively. Mixtures of curing agent and PDMS prepolymer are prepared using the above ratios. These mixtures are made into 180 μm thick PDMS samples and heated at 60° C. for 2 h. The deformation of the PDMS samples is measured by stretching, thereby obtaining stress-strain curves of each sample, as shown in FIG. Figure 6 As shown, according to the results of the stress-strain curve, the elastic modulus of PDMS can be changed by adjusting the curing agent ratio. The lower the elastic modulus, the softer the material, and vice versa.

[0084] Considering the user-friendly operation, the driving force of the push-actuated pump 1 needs to be as small as possible to reduce the burden. Although the 1:20 PDMS sample is soft and easy to compress, its structural strength is insufficient and it is easy to be damaged. Therefore, a 1:15 ratio of curing agent to PDMS prepolymer is selected as the optimal ratio of the push-actuated pump 1.

[0085] S103, pressing the casting molding of the driving pump 1;

[0086] According to the mixture ratio selected in step S102, the curing agent and the PDMS prepolymer are mixed in a ratio of 1:15, and the mixed mixture is injected into the press-driven pump 1 mold assembled with the base 8 and the cover plate 7, and placed in a 0.8Mpa vacuum cover for 15 minutes to remove bubbles; then the cast press-driven pump 1 mold is placed in a 60°C oven for curing for 2 hours. After curing, the base 8 and the cover plate 7 of the press-driven pump 1 mold are separated, and the cured press-driven pump 1 is taken out.

[0087] S2, preparation of the microfluidic chip body, comprising the following steps:

[0088] S201, fabrication of a microfluidic chip body mold; the manufacturing thickness of the SU-8 mold is 100 μm, specifically comprising the following steps:

[0089] S2011, mask production;

[0090] The designed microstructure of the liquid storage layer 2 of the microfluidic chip is drawn into a two-dimensional drawing using AutoCAD software, and then made into a film mask by the processor; the positive and negative phases of the photoresist are the key to determining the mask processing and microstructure formation characteristics; negative photoresist is used, which is opposite to the positive photoresist that is soluble under ultraviolet light. After exposure, the negative photoresist area remains insoluble, making the corresponding part of the mask channel transparent, causing the photoresist to solidify and cross-link, forming the desired microfluidic channel structure.

[0091] S2012, pretreatment of silicon wafer;

[0092] Before preparing the SU-8 mold, it is usually necessary to pre-treat the silicon wafer to ensure that its surface is clean and dry; after cleaning the surface of the silicon wafer with isopropanol, drying it in a 60°C oven for 10 minutes can effectively remove impurities, oil stains and other pollutants and improve the hydrophilicity of its surface.

[0093] S2013, spin coating SU-8 photoresist;

[0094] Add an appropriate amount of SU-82050 negative photoresist on the pre-treated silicon wafer, then place the silicon wafer on the tray in the center of the coating machine and fix it with a vacuum pump to prevent the silicon wafer from shifting during the spin coating process; use a multi-step spin coating method, with the first step at a speed of 500 rpm and the second step at 200 rpm. 2 Spin coating for 20 seconds at an acceleration to help the photoresist spread to form an initial film; the second step is at a speed of 1700 rpm and 300 rpm 2 Spin coating for 30 seconds under acceleration. The spin coating parameters in this step determine the thickness of the photoresist. After spin coating, let it stand for a while to make the surface flat.

[0095] S2014, pre-baking;

[0096] Use a precisely temperature-controlled HP10 adhesive baker for heating to ensure that the photoresist adheres evenly to the silicon wafer and improve its mechanical stability; first bake the silicon wafer at 65°C for 4 minutes, and then continue to bake at 95°C for 16 minutes; after baking, take out the silicon wafer and cool it to room temperature. If there is any wrinkling, put it back in the adhesive baker; through repeated cooling and heating processes, ensure that the surface of the silicon wafer is smooth and wrinkle-free.

[0097] S2015, exposure;

[0098] After the silicon wafer has cooled to room temperature, it is exposed using a H94-27 (LED) microfluidic chip processing device. The device uses UVLED as a light source and has no infrared radiation, which helps to avoid the expansion and contraction of the film. The operating steps include placing the translucent plate on the plate holder, starting the vacuum pump and fixing it using the "plate suction" button on the operation interface. Subsequently, the wafer stage is pulled out, the silicon wafer and mask are placed in turn, and the silicon wafer is fixed on the wafer stage using the "film suction" button. After the wafer stage is pushed into the extreme position, the exposure time is precisely controlled to 23 seconds according to the SU-8 thickness and mold structure requirements. Next, the "stage lift", "contact" and "exposure position" buttons on the operation interface are pressed to start the exposure process.

[0099] S2016, post-baking;

[0100] After the exposure is completed, the silicon wafer is placed in the glue drying machine again to further cross-link and cure the photoresist, thereby improving the mechanical properties and stability of the mold; the time and temperature of the post-baking need to be adjusted according to the thickness and structure of the mold; first, bake the silicon wafer at 65°C for 2 minutes, then bake at 95°C for 9 minutes, and finally wait for the silicon wafer to cool to room temperature.

[0101] S2017, development;

[0102] SU-8 negative photoresist is used. The negative photoresist undergoes a curing and cross-linking reaction in the UV-exposed area, while the unexposed area remains uncured. Subsequently, the silicon wafer that has been cooled after post-baking is placed in a developer to dissolve the unexposed part, revealing a microchannel structure pattern. The developing time varies depending on the type and thickness of the photoresist. Usually, the processed silicon wafer is placed in a glass culture dish containing a developer and rinsed for 8 minutes. Then, isopropyl alcohol is used to clean the excess developer on the surface of the silicon wafer. Finally, the surface of the silicon wafer is blown dry to obtain a preliminary SU-8 mold.

[0103] S2018, hard baking;

[0104] High-temperature hard baking treatment is used to improve the durability and stability of the SU-8 mold, which can enhance the degree of cross-linking inside the SU-82050 photoresist; the developed silicon wafer is placed in a 220°C glue baking machine and baked for 3 minutes to obtain a solid SU-8 mold, providing stable conditions for subsequent chip production.

[0105] S202, fabrication of microfluidic chip body;

[0106] PDMS is a silicon-based organic polymer with excellent optical transparency, flexibility and elastomeric properties. It is widely used in fields such as tissue engineering and biomedicine due to its unique biocompatibility. In addition, PDMS can be made into various microscale and nanoscale structures through a simple casting process. The combination with soft lithography technology has enabled PDMS to achieve extensive development in the fields of micromanufacturing and microfluidic device design.

[0107] After the SU-8 mold is prepared, the PDMS material is poured into the mold for curing to replicate the microchannel structure on the mold surface, which is called the PDMS casting method. Using the SYLGARDTM 184Silicone Elastomer Kit model PDMS, the PDMS and curing agent are first mixed in a mass ratio of 10:1 and stirred thoroughly until full of bubbles. The SU-8 mold is fixed to the bottom of the culture dish by using double-sided tape, and then the mixed PDMS is poured into the culture dish, placed in a 0.8Mpa vacuum cover and allowed to stand for about 15 minutes to remove bubbles. Finally, the culture dish is placed in a 60°C oven and heated for 2 hours to cure the PDMS. After the curing is completed, a scalpel is used to cut and uncover the required area to obtain a PDMS microfluidic chip with a liquid storage layer 2 and a bottom plate 3 with microchannel grooves on the surface.

[0108] The upper liquid storage layer 2 and the lower bottom plate 3 are packaged by oxygen plasma bonding process; before bonding, a 1 mm punch is used to punch through the second opening 5 of the liquid storage through hole 9 on the liquid storage layer 2, and then the surface is repeatedly taped with transparent tape to clean it, and then the liquid storage layer 2 and the bottom plate 3 are respectively placed in the oxygen plasma equipment and treated with oxygen plasma for 100 seconds; PDMS is usually hydrophobic, and oxygen plasma treatment can introduce active groups, such as hydroxyl (-OH), carboxyl (-COOH), etc. These active groups can increase the polarity of the PDMS surface and enhance its interaction with other polar surfaces, thereby improving adhesion and achieving bonding on both sides, and finally completing the production of the PDMS microfluidic chip body.

[0109] S3, assembly of the microfluidic chip; the assembly of the microfluidic chip includes the following steps: after the preparation of the push-driven pump 1 and the microfluidic chip body is completed, the microfluidic chip body and the push-driven pump 1 are cleaned with isopropanol and deionized water respectively to remove impurities and dust on the surfaces of the two, and the microfluidic chip body and the push-driven pump 1 are immediately accurately aligned after oxygen plasma treatment for 100s, and lightly pressed to bond them into a chip as a whole, thereby completing the assembly of the microfluidic chip;

[0110] S4. Use of microfluidic chip; The use of microfluidic chip includes the following steps: first, take an appropriate amount of solution with a pipette and add it to the serpentine channel liquid storage chamber 10 through the first opening 4, the pump cavity, the second opening 5, and the liquid storage hole 9, close the first opening 4, and then squeeze and press the drive pump 1 with your fingers, the pump body is deformed, and the fluid in the serpentine channel liquid storage chamber 10 is driven to break through the N-type capillary burst valve 12, so as to realize the controllable drive of the fluid. The flow rate of the fluid is related to the pressure and frequency of the pressing. The fluid that breaks through the N-type capillary burst valve 12 flows out along the liquid storage hole 11, the bottom plate through hole 13, and the third opening 6; the microfluidic chip based on the press-driven fluid is used in multiple integrations, and it can be applied to enzyme-linked immunosorbent assay, for example, three such microfluidic chips based on the press-driven fluid are integrated into one chip for use, and the analyte solution to be detected, the enzyme-labeled antibody solution and the color substrate solution are added to the three serpentine channel liquid storage chambers 10 respectively; the three solutions can be pumped in sequence to perform enzyme-linked immunosorbent assay.

[0111] The approximate calculation function of the fluid flow rate is:

[0112] Q = f·ΔV;

[0113] Wherein, Q represents the flow rate of the pressing drive pump 1; f represents the pressing frequency; ΔV represents the deformation of the pressing drive pump 1 during squeezing;

[0114] Assuming that the pressure on the pressure-driven pump 1 is uniform, the calculation function of the deformation amount ΔV of the pressure-driven pump 1 is:

[0115]

[0116] Among them, e is the logarithm of the natural base; E represents the elastic modulus of the press-driven pump 1; P represents the applied pressure; V0 represents the initial volume of the pump cavity; when the applied pressure increases, the deformation of the press-driven pump 1 will also increase, and the rate of increase will gradually decrease.

[0117] The pressure barrier of the N-type capillary bursting valve 12 depends on the changes in the surface tension of the fluid, the contact angle and the shape of the channel of the N-type capillary bursting valve 12. Since the cross section of the channel of the N-type capillary bursting valve 12 is rectangular, the bursting pressure P of the N-type capillary bursting valve 12 is CBV The calculation function is:

[0118]

[0119] Where γ1 represents the surface tension of the fluid; θ l represents the contact angle between the fluid and the left side of the channel of the N-type capillary burst valve 12; θ r represents the contact angle between the fluid and the right side of the channel 12 of the N-type capillary burst valve; θ trepresents the contact angle between the fluid and the top of the channel of the N-type capillary burst valve 12; θ b represents the contact angle between the fluid and the bottom of the channel of the N-type capillary burst valve 12; w and h represent the width and depth of the channel of the N-type capillary burst valve 12, respectively;

[0120] Since the N-type capillary burst valve 12 channels are made of the same material, they have the same contact angle, so the burst pressure P CBV The calculation function is further simplified to:

[0121]

[0122] Among them, θ c is the contact angle between the fluid and the channel of the N-type capillary burst valve 12.

[0123] Example 2

[0124] A microfluidic chip based on pressure-driven fluid, the preparation method of which includes: S1, preparation of a pressure-driven pump 1; S2, preparation of a microfluidic chip body; S3, assembly of the microfluidic chip based on pressure-driven fluid; S4, use of the microfluidic chip based on pressure-driven fluid.

[0125] S1. The preparation of the press-driven pump 1 comprises the following steps:

[0126] S101, drawing and printing a mold of a press-driven pump 1;

[0127] The press-actuated pump 1 is casted by PDMS (polydimethylsiloxane) material. During preparation, the mold of the press-actuated pump 1 is first designed using Solidworks 3D modeling software, such as Figure 5 As shown, the mold of the press-driven pump 1 is divided into two layers, namely, a base 8 and a cover plate 7. Printing technology is used to ensure high precision and good surface finish, and it is suitable for use as a PDMS mold. After printing, it is cleaned with isopropyl alcohol to remove uncured resin on the surface, and then placed in an ultraviolet environment for curing for 10 minutes to ensure the final quality of the mold.

[0128] S102, evaluating the ratio of the curing agent and the PDMS prepolymer mixture;

[0129] To evaluate the effect of different curing agent ratios on the deformation resistance of the press-actuated pump 1, mixtures of curing agent and PDMS prepolymer were prepared in ratios of 1:10, 1:15, and 1:20, respectively; these mixtures were made into 180 μm thick PDMS samples and heated at 60°C for 2 h; the deformation of the PDMS samples was measured by stretching, thereby obtaining stress-strain curves, such as Figure 6As shown; according to the results of the stress-strain curve, the elastic modulus of PDMS can be changed by adjusting the curing agent ratio. The lower the elastic modulus, the softer the material, and vice versa.

[0130] Considering the user-friendly operation, the driving force of the push-actuated pump 1 needs to be as small as possible to reduce the burden. Although the 1:20 PDMS sample is soft and easy to compress, its structural strength is insufficient and it is easy to be damaged. Therefore, a 1:15 ratio of curing agent to PDMS prepolymer is selected as the optimal ratio of the push-actuated pump 1.

[0131] S103, pressing the casting molding of the driving pump 1;

[0132] After the mold is prepared, the curing agent and PDMS prepolymer are mixed in a ratio of 1:15 and poured into the mold, and placed in a 0.8Mpa vacuum hood for 15 minutes to remove bubbles; the cast mold is placed in a 60°C oven for curing for 2 hours. After curing, the base 8 and cover plate 7 of the mold are separated, and the press drive pump 1 is taken out.

[0133] S2, preparation of a microfluidic chip body having a serpentine channel liquid storage cavity 10 and an N-type capillary burst valve 12, comprising the following steps:

[0134] S201, mold making; the manufacturing thickness of the SU-8 mold is 100 μm, specifically comprising the following steps:

[0135] S2011, mask production;

[0136] In this embodiment, the designed microstructure of the liquid storage layer 2 of the microfluidic chip is drawn into a two-dimensional drawing using AutoCAD software, which is then made into a film mask by the processor; the positive and negative phases of the photoresist are the key to determining the mask plate processing and microstructure formation characteristics; this embodiment uses negative photoresist, which is opposite to the positive photoresist that is soluble under ultraviolet light. After exposure, the negative photoresist area remains insoluble, making the corresponding part of the mask channel transparent, causing the photoresist to solidify and cross-link, forming the desired microfluidic channel structure.

[0137] S2012, pretreatment of silicon wafer;

[0138] Before preparing the SU-8 mold, it is usually necessary to pre-treat the silicon wafer to ensure that its surface is clean and dry; after cleaning the surface of the silicon wafer with isopropanol, drying it in a 60°C oven for 10 minutes can effectively remove impurities, oil stains and other pollutants and improve the hydrophilicity of its surface.

[0139] S2013, spin coating SU-8 photoresist;

[0140] Add an appropriate amount of SU-82050 negative photoresist on the pre-treated silicon wafer, then place the silicon wafer on the tray in the center of the coating machine and fix it with a vacuum pump to prevent the silicon wafer from shifting during the spin coating process; use a multi-step spin coating method, with the first step at a speed of 500 rpm and the second step at 200 rpm. 2 Spin coating for 20 seconds at an acceleration to help the photoresist spread to form an initial film; the second step is at a speed of 1700 rpm and 300 rpm 2 Spin coating for 30 seconds under acceleration. The spin coating parameters in this step determine the thickness of the photoresist. After spin coating, let it stand for a while to make the surface flat.

[0141] S2014, pre-baking;

[0142] Use a precisely temperature-controlled HP10 adhesive baker for heating to ensure that the photoresist adheres evenly to the silicon wafer and improve its mechanical stability; first bake the silicon wafer at 65°C for 4 minutes, and then continue to bake at 95°C for 16 minutes; after baking, take out the silicon wafer and cool it to room temperature. If there is any wrinkling, put it back in the adhesive baker; through repeated cooling and heating processes, ensure that the surface of the silicon wafer is smooth and wrinkle-free.

[0143] S2015, exposure;

[0144] After the silicon wafer has cooled to room temperature, it is exposed using a H94-27 (LED) microfluidic chip processing device. The device uses UVLED as a light source and has no infrared radiation, which helps to avoid the expansion and contraction of the film. The operating steps include placing the translucent plate on the plate holder, starting the vacuum pump and fixing it using the "plate suction" button on the operation interface. Subsequently, the wafer stage is pulled out, the silicon wafer and mask are placed in turn, and the silicon wafer is fixed on the wafer stage using the "film suction" button. After the wafer stage is pushed into the extreme position, the exposure time is precisely controlled to 23 seconds according to the SU-8 thickness and mold structure requirements. Next, the "stage lift", "contact" and "exposure position" buttons on the operation interface are pressed to start the exposure process.

[0145] S2016, post-baking;

[0146] After the exposure is completed, the silicon wafer is placed in the glue drying machine again to further cross-link and cure the photoresist, thereby improving the mechanical properties and stability of the mold; the time and temperature of the post-baking need to be adjusted according to the thickness and structure of the mold; first, bake the silicon wafer at 65°C for 2 minutes, then bake at 95°C for 9 minutes, and finally wait for the silicon wafer to cool to room temperature.

[0147] S2017, development;

[0148] The present embodiment uses SU-8 negative photoresist, which undergoes a curing and cross-linking reaction in the UV-exposed area, while the unexposed area remains uncured. Subsequently, the silicon wafer after post-baking and cooling is placed in a developer to dissolve the unexposed part, thereby presenting a microchannel structure pattern. The developing time varies depending on the type and thickness of the photoresist. Usually, the processed silicon wafer is placed in a glass culture dish containing a developer and rinsed for 8 minutes. Then, the excess developer on the surface of the silicon wafer is cleaned with isopropyl alcohol, and finally, the surface of the silicon wafer is blown dry to obtain a preliminary SU-8 mold.

[0149] S2018, hard baking;

[0150] High-temperature hard baking treatment is used to improve the durability and stability of the SU-8 mold, which can enhance the degree of cross-linking inside the SU-82050 photoresist; the developed silicon wafer is placed in a 220°C glue baking machine and baked for 3 minutes to obtain a solid SU-8 mold, providing stable conditions for subsequent chip production.

[0151] S202. Fabrication of microfluidic chip

[0152] PDMS is a silicon-based organic polymer with excellent optical transparency, flexibility and elastomeric properties. It is widely used in fields such as tissue engineering and biomedicine due to its unique biocompatibility. In addition, PDMS can be made into various microscale and nanoscale structures through a simple casting process. The combination with soft lithography technology has enabled PDMS to achieve extensive development in the fields of micromanufacturing and microfluidic device design.

[0153] After the SU-8 mold is prepared, the PDMS material is poured into the mold for curing to replicate the microchannel structure on the mold surface, which is called the PDMS casting method. This embodiment uses the SYLGARDTM 184Silicone Elastomer Kit model PDMS. First, the PDMS and the curing agent are mixed in a mass ratio of 10:1 and stirred thoroughly until full of bubbles. The SU-8 mold is fixed to the bottom of the culture dish by using double-sided tape, and then the mixed PDMS is poured into the culture dish, placed in a 0.8Mpa vacuum cover and allowed to stand for about 15 minutes to remove bubbles. Finally, the culture dish is placed in a 60°C oven and heated for 2 hours to cure the PDMS. After the curing is completed, a scalpel is used to cut and uncover the required area to obtain a PDMS microfluidic chip with a liquid storage layer 2 and a bottom plate 3 with microchannel grooves on the surface.

[0154] In this embodiment, an oxygen plasma bonding process is used to encapsulate the upper liquid storage layer 2 and the lower bottom plate 3; before bonding, a 1 mm punch is used to punch through the second opening 5 of the liquid storage through hole 9 on the liquid storage layer 2, and then a transparent tape is used to repeatedly stick the surface to clean it, and then the liquid storage layer 2 and the bottom plate 3 are respectively placed in an oxygen plasma device and treated with oxygen plasma for 100 seconds; PDMS is usually hydrophobic, and oxygen plasma treatment can introduce active groups, such as hydroxyl (-OH), carboxyl (-COOH), etc. These active groups can increase the polarity of the PDMS surface and enhance its interaction with other polar surfaces, thereby improving adhesion, achieving bonding on both sides, and finally completing the production of the PDMS microfluidic chip body.

[0155] S3, assembly of microfluidic chip based on pressure-driven fluid;

[0156] After completing the preparation of the pressure-driven pump 1 and the microfluidic chip body, the two components are assembled into an integrated microfluidic chip; first, the microfluidic chip and the pressure-driven pump 1 are cleaned with isopropyl alcohol and deionized water respectively to remove impurities and dust on the surface, and the microfluidic chip and the pressure-driven pump 1 are immediately accurately aligned after 100s of oxygen plasma treatment, and lightly pressed to bond them into a chip as a whole, thereby completing the preparation of the microfluidic chip body for the pressure-driven fluid.

[0157] S4. Use of microfluidic chips based on pressure-driven fluids;

[0158] When using a microfluidic chip based on pressure-driven fluid: first use a pipette to take an appropriate amount of solution and add it to the serpentine channel liquid storage chamber 10 through the first opening 4, the pump cavity, the second opening 5, and the liquid storage through hole 9, close the first opening 4, and then squeeze the pressure-driven pump 1 with your fingers to drive the fluid in the serpentine channel liquid storage chamber 10 to break through the N-type capillary burst valve 12 to achieve controllable driving of the fluid. The flow rate of the fluid is related to the pressure and frequency of the finger pressing. The fluid that breaks through the N-type capillary burst valve 12 flows out along the liquid storage hole 11, the bottom plate through hole 13, and the third opening 6; the microfluidic chip based on pressure-driven fluid can be integrated and used in multiple ways, and can be applied to enzyme-linked immunosorbent assay. For example, three such microfluidic chips based on pressure-driven fluid are integrated into one chip for use, and the analyte solution to be detected, the enzyme-labeled antibody solution, and the color substrate solution are added to the three serpentine channel liquid storage chambers 10 respectively; the three solutions can be pumped in sequence to perform enzyme-linked immunosorbent assay.

[0159] The above description is only a preferred embodiment of the present invention, but is not limited to the above examples. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A microfluidic chip based on pressure-driven fluid, characterized in that: It comprises a microfluidic chip body and a press-driven pump matched with the microfluidic chip body; the microfluidic chip body comprises a liquid storage layer and a bottom plate stacked up and down, and the liquid storage layer is connected to the press-driven pump; a first opening is provided on the press-driven pump, and the first opening is matched with a second opening arranged on the upper surface of the liquid storage layer through a pump cavity arranged in the press-driven pump, and the second opening is connected with a serpentine channel liquid storage cavity arranged on the lower surface of the liquid storage layer through a liquid storage through hole penetrating the liquid storage layer, and an N-type capillary burst valve is provided at one end of the serpentine channel liquid storage cavity away from the liquid storage through hole.

2. The microfluidic chip based on pressure-driven fluid according to claim 1, characterized in that: The N-type capillary burst valve has a liquid storage hole at one end away from the serpentine channel liquid storage cavity, and the liquid storage hole is connected with a third opening arranged on the lower surface of the bottom plate through a bottom plate through hole arranged on the bottom.

3. The microfluidic chip based on pressure-driven fluid according to claim 2, characterized in that: The press-driven pump comprises a hemispherical shell, a press sleeve is arranged on the hemispherical shell, and the first opening is arranged at the center of the press sleeve.

4. The microfluidic chip based on pressure-driven fluid according to claim 3, characterized in that: The height of the serpentine channel liquid storage cavity and the N-type capillary burst valve is 90um-110um, the width of the serpentine channel liquid storage cavity is 0.90mm-1.10mm, and the total length of the serpentine channel liquid storage cavity is 38mm-42mm.

5. A method according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1, preparation of a pressure-driven pump; S2, preparation of a microfluidic chip body; S3, assembly of the microfluidic chip; and S4, use of the microfluidic chip.

6. The method of the microfluidic chip according to claim 5, characterized in that: In step S1, the preparation of the press-driven pump includes the following steps: S101, drawing and printing of a press drive pump mold; The press-actuated pump mold is configured to be composed of a base and a cover plate, and the base and the cover plate of the press-actuated pump mold are drawn using modeling software, and the base and the cover plate of the press-actuated pump mold are printed using printing technology. After printing, the base and the cover plate are cleaned with isopropyl alcohol to remove uncured resin on the surface of the base and the cover plate, and then placed in an ultraviolet environment for curing; S102, evaluating the mixture ratio of the curing agent and the PDMS prepolymer; S103, casting and molding of a press-driven pump; According to the mixture ratio selected in step S102, the mixed mixture is injected into the press-driven pump mold with the base and the cover plate assembled, and placed in a vacuum cover; the cast press-driven pump mold is then placed in an oven for curing, and after curing, the base and the cover plate of the press-driven pump mold are separated, and the cured press-driven pump is taken out.

7. The method of the microfluidic chip according to claim 5, characterized in that: In step S2, the preparation of the microfluidic chip body includes the following steps: S201, making a microfluidic chip body mold, which includes the following steps: S2011, making a mask; S2012, pre-treatment of silicon wafers; S2013, spin coating photoresist; S2014, pre-baking; S2015, exposure; S2016, post-baking; S2017, development; S2018, hard baking; S202, fabrication of the microfluidic chip body.

8. The method of the microfluidic chip according to claim 5, characterized in that: In step S3, the assembly of the microfluidic chip includes the following steps: after the preparation of the push-driven pump and the microfluidic chip body is completed, the microfluidic chip body and the push-driven pump are cleaned with isopropyl alcohol and deionized water respectively to remove impurities and dust on the surfaces of the two, and the microfluidic chip body and the push-driven pump are accurately aligned immediately after oxygen plasma treatment, and lightly pressed to bond them into a chip as a whole, thereby completing the assembly of the microfluidic chip; In step S4, the use of the microfluidic chip includes the following steps: First, use a pipette to take an appropriate amount of solution and add it to the serpentine channel reservoir through the second opening. Then use your fingers to squeeze and press the drive pump, causing the pump body to deform, driving the fluid in the serpentine channel reservoir to break through the N-type capillary burst valve, thereby achieving controllable drive of the fluid. The flow rate of the fluid is related to the pressure and frequency of pressing.

9. The method of the microfluidic chip according to claim 8, characterized in that: In step S4, the approximate calculation function of the fluid flow rate is, Q = f·ΔV; Wherein, Q represents the flow rate of the pressure-driven pump; f represents the pressing frequency; ΔV represents the deformation of the pressure-driven pump during extrusion; Assuming that the pressure on the pressure-driven pump is uniform, the calculation function of the deformation variable ΔV of the pressure-driven pump is: Wherein, e is the logarithm of the natural base; E represents the elastic modulus of the pressure-driven pump; P represents the applied pressure; and V0 represents the initial volume of the pump cavity.

10. The method of the microfluidic chip according to claim 9, characterized in that: In step S4, the pressure barrier of the N-type capillary bursting valve depends on the changes in the surface tension of the fluid, the contact angle and the shape of the N-type capillary bursting valve channel. Since the cross section of the N-type capillary bursting valve channel is rectangular, the bursting pressure P of the N-type capillary bursting valve is CBV The calculation function is: Where γ1 represents the surface tension of the fluid; θ l represents the contact angle between the fluid and the left side of the N-type capillary burst valve channel; θ r represents the contact angle between the fluid and the right side of the N-type capillary burst valve channel; θ t Represents the contact angle between the fluid and the top of the N-type capillary burst valve channel; θ b represents the contact angle between the fluid and the bottom of the N-type capillary burst valve channel; w and h represent the width and depth of the N-type capillary burst valve channel, respectively; Since the N-type capillary burst valve channel is made of the same material, it has the same contact angle, so the burst pressure P CBV The calculation function is further simplified to: Among them, θ c is the contact angle between the fluid and the channel of the N-type capillary burst valve.

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