A microfluidic chip and method based on pressure-driven fluid

Abstract

This invention belongs to the field of microfluidic chip technology, specifically disclosing a microfluidic chip based on pressure-driven fluid, including a microfluidic chip body and a pressure-driven pump that cooperates with the microfluidic chip body; the microfluidic chip body includes a liquid storage layer and a base plate stacked on top of each other, the liquid storage layer being connected to the pressure-driven pump; the pressure-driven pump has a first opening, which cooperates with a second opening on the upper surface of the liquid storage layer through a pump cavity disposed within the pressure-driven pump, the second opening being connected to a serpentine channel liquid storage cavity disposed 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 the end of the serpentine channel liquid storage cavity away from the liquid storage through-hole; this invention can realize a simple, fluid-controllable fluid driving method that does not rely on external equipment, and can significantly reduce the impact of external driving equipment on active microfluidic driving systems.

Description

Technical Field

[0001] This invention belongs to the field of microfluidic chip technology, specifically relating to a microfluidic chip based on pressure-driven fluid, and also to a method for using the microfluidic chip based on pressure-driven fluid. Background Technology

[0002] Current microfluidic actuation methods are divided into passive and active types. Passive fluid actuation mainly relies on self-driving forces such as capillary action, inertial force, and viscous force, without the need for external source input. It has the advantages of simple structure and low cost, and is suitable for simple and low-cost detection scenarios. Active fluid actuation, on the other hand, requires an external power source to drive the fluid. Common actuation methods include pressure actuation, centrifugal actuation, electric actuation, and thermal actuation. Its advantage is that it can achieve more precise and controllable fluid manipulation, and is suitable for complex applications of fine fluid management.

[0003] In 2006, Zimmermann et al. achieved self-driven fluid flow in microfluidic devices by designing capillary microstructures for ELISA assays. However, this method was prone to bubble generation during detection, affecting accuracy. In 2021, Rocca et al. developed a novel capillary-driven microfluidic chip capable of quantitative detection of glucose-6-phosphate dehydrogenase and hemoglobin using trace samples within 2 minutes. Nevertheless, the passive drive structure is complex to design, suffers from poor flow uniformity, and is prone to bubble generation, making continuous differential control of fluid channel velocity impossible. In 2005, Jeong et al. proposed a thermally driven technology, which uses heated gas to make an elastic thin... Membrane deformation drives fluid movement; in 2024, Xiao et al. proposed a fully integrated automated centrifugal microfluidic chip that uses centrifugal force to drive fluid and achieve instantaneous multiplex molecular diagnostics; in addition, in 2021, Uvarov et al. described an electro-driven micropump that uses microsecond voltage pulses to drive AP electrolysis through three peristaltic membrane actuators. Although the above active micropumps can achieve precise fluid control, they all rely on external driving devices to operate, which increases the complexity of the system. The complex external driving devices will affect the use of active microfluidic actuation in complex environments and affect the popularization and practicality of portable POCT (point-of-care testing) technology in different application scenarios. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a microfluidic chip and method based on pressure-driven fluid control that has fluid control effects, does not rely on external devices, and has a simple structure.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] A microfluidic chip based on pressure-driven fluid includes a microfluidic chip body and a pressure-driven pump that cooperates with the microfluidic chip body. The microfluidic chip body includes a liquid storage layer and a base plate stacked on top of each other, and the liquid storage layer is connected to the pressure-driven pump. The pressure-driven pump has a first opening, which cooperates with a second opening on the upper surface of the liquid storage layer through a pump cavity disposed within the pressure-driven pump. The second opening is connected to a serpentine channel liquid storage cavity disposed on the lower surface of the liquid storage layer through a liquid storage through-hole penetrating the liquid storage layer. An N-type capillary burst valve is provided at the end of the serpentine channel liquid storage cavity away from the liquid storage through-hole.

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

[0008] Preferably, the press drive pump includes a hemispherical housing, a press sleeve is provided on the hemispherical housing, and a first opening is provided 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 or 100um, the width of the serpentine channel liquid storage chamber is 0.90mm-1.10mm or 1mm, and the total length of the serpentine channel liquid storage chamber is 38mm-42mm or 40mm. A 40mm dimension can store 4ul of liquid; the liquid storage capacity can be increased by increasing the length of the serpentine channel liquid storage chamber.

[0010] Preferably, the N-type capillary burst valve has a contraction width of 25 μm. The N-type structure increases fluid resistance and improves the performance of the capillary burst valve. When a pressure of 3250 Pa is applied at the second opening, the N-type capillary burst valve successfully blocks the liquid flow. When the pressure exceeds this, the N-type capillary burst valve will be breached, and the fluid will be driven.

[0011] Preferably, the press-driven pump is manufactured by casting PDMS material. First, a mold for the press-driven pump needs to be made. The mold consists of two layers: a base and a cover plate. After printing the mold using photopolymerization printing technology, isopropyl alcohol is used to clean it and remove uncured resin from the surface. Finally, it is placed in a UV environment for curing for ten minutes to improve the printing quality.

[0012] Preferably, the deformation resistance of the press-driven pump is affected by the curing agent. By stretching three PDMS samples with PDMS:curing agent ratios of 1:10, 1:15, and 1:20 to measure their deformation, the stress-strain curves show that the curing agent can change the elastic modulus of PDMS. Considering both operational friendliness and pump structural strength, a PDMS:curing agent ratio of 1:15 was selected as the optimal ratio for manufacturing the PDMS press-driven pump. The manufacturing process of the PDMS press-driven pump includes the following steps: First, an appropriate amount of PDMS is placed on the base mold, the cover mold is closed, and the cover is gently pressed to allow the PDMS to flow out from the gap between the base and the cover. Then, it is placed in an oven at 65 degrees Celsius for 2 hours and finally demolded.

[0013] A method for manufacturing a microfluidic chip includes the following steps: S1, fabrication of a press-driven pump; S2, fabrication of a microfluidic chip body; S3, assembly of the microfluidic chip; and S4, use of the microfluidic chip.

[0014] Preferably, in step S1, the preparation of the press-driven pump includes the following steps;

[0015] S101. Drawing and printing the mold for the press-driven pump;

[0016] The press-driven pump mold is set up as a base and a cover plate. The base and cover plate of the press-driven pump mold are drawn using modeling software. The base and cover plate of the press-driven pump mold are printed using printing technology. After printing, the base and cover plate are cleaned with isopropanol to remove uncured resin from the surface of the base and cover plate. Then, they are placed in a UV environment for 10 minutes to ensure the final quality of the press-driven pump mold.

[0017] S102. Evaluate the mixing ratio of curing agent and 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. The selected mixture ratios are 1:10, 1:15, and 1:20. Mixtures of curing agent and PDMS prepolymer are prepared using the above ratios. These mixtures are made into PDMS samples with a thickness of 180 μm and heat-treated at 60°C for 2 hours. The deformation of the PDMS samples is measured by tensile testing to obtain the stress-strain curves of each sample. According to the results of the stress-strain curves, 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] To ensure user-friendliness, the driving force of the press-driven pump needs to be as small as possible to reduce the workload. Although a 1:20 PDMS sample is relatively soft and easy to compress, its structural strength is insufficient and it is easily damaged. Therefore, a 1:15 ratio of curing agent to PDMS prepolymer was selected as the optimal ratio for the press-driven pump.

[0020] S103, Casting molding using a press-driven pump;

[0021] According to the mixing ratio selected in step S102, the curing agent and PDMS prepolymer are mixed at a ratio of 1:15. The mixed mixture is then injected into the press-driven pump mold assembled with the base and cover plate. The mold is placed in a 0.8 MPa vacuum chamber for 15 minutes to remove air bubbles. The poured press-driven pump mold is then placed in a 60°C oven for 2 hours to cure. After curing, the base and 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 fabrication of the microfluidic chip body includes the following steps:

[0023] S201, Fabrication of the microfluidic chip body mold;

[0024] The SU-8 mold is manufactured with a thickness of 100μm, and the specific steps include:

[0025] S2011, Mask creation;

[0026] The designed microfluidic chip reservoir layer microstructure is drawn into a two-dimensional drawing using AutoCAD software, and then fabricated into a film mask by the manufacturer. The positive and negative phase properties of the photoresist are the key to determining the mask processing and microstructure formation characteristics. Negative photoresist is used, which is the opposite of positive photoresist, which is soluble under ultraviolet light. After exposure, the negative photoresist area remains insoluble, allowing light to pass through the corresponding part of the mask channel, causing the photoresist to solidify and cross-link, forming the required microfluidic channel structure.

[0027] S2012, Pretreatment of silicon wafers;

[0028] Before preparing the SU-8 mold, the silicon wafer usually needs to be pretreated to ensure that its surface is clean and dry. After cleaning the surface of the silicon wafer with isopropanol, it can be dried in a 60°C oven for 10 minutes to effectively remove impurities, oil and other contaminants, and improve the hydrophilicity of its surface.

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

[0030] An appropriate amount of SU-82050 negative photoresist was applied to the pretreated silicon wafer. The wafer was then placed on the tray in the center of the spin coater and secured with a vacuum pump to prevent displacement during the spin coating process. A multi-step spin coating method was employed, with the first step using a spin speed of 500 rpm and a spin speed of 200 rpm. 2 Spin-coating under acceleration for 20 seconds to help the photoresist spread and form the initial film; the second step involves spin coating at 1700 rpm and 300 rpm. 2 Spin-coat under acceleration for 30 seconds. The spin-coating parameters in this step determine the thickness of the photoresist. After spin-coating, let it stand for a while to allow the surface to become smooth.

[0031] S2014, Pre-drying;

[0032] The HP10 photoresist baking machine with precise temperature control is used to heat the silicon wafer to ensure uniform adhesion of the photoresist and improve its mechanical stability. The silicon wafer is first baked at 65°C for 4 minutes, and then baked at 95°C for another 16 minutes. After baking, the silicon wafer is removed and cooled to room temperature. If wrinkles are found, it can be placed back into the photoresist baking machine. Through repeated cooling and heating processes, the surface of the silicon wafer is ensured to be smooth and wrinkle-free.

[0033] S2015, Exposure;

[0034] After the silicon wafer cools to room temperature, exposure is performed using an H94-27 (LED) microfluidic chip processing device. This device uses UV LEDs as the light source, which emits no infrared radiation and helps avoid film expansion and contraction. The operation steps include placing the transparent plate on the plate holder, starting the vacuum pump, and fixing it using the "Suction Plate" button on the operation interface. Then, the wafer stage is pulled out, and the silicon wafer and mask are placed in sequence, and the silicon wafer is fixed on the wafer stage using the "Suction Wafer" button. After pushing the wafer stage to its limit position, the exposure time is precisely controlled to 23 seconds according to the SU-8 thickness and mold structure requirements. Then, the "Stage Lift," "Contact," and "Exposure Position" buttons on the operation interface are pressed to start the exposure process.

[0035] S2016, Post-drying;

[0036] After exposure, the silicon wafer is baked again in a photoresist baking machine to further crosslink and cure the photoresist, thereby improving the mechanical properties and stability of the mold. The baking time and temperature 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 photoresist is used. The photoresist undergoes a curing and cross-linking reaction in the UV-exposed areas, while the unexposed areas remain uncured. Subsequently, the silicon wafer, after being baked and cooled, is placed in a developing solution to dissolve the unexposed parts and reveal a microchannel structure pattern. The developing time varies depending on the type and thickness of the photoresist. Typically, the processed silicon wafer is placed in a glass petri dish containing developing solution and rinsed for 8 minutes. Then, the excess developing solution on the surface of the silicon wafer is cleaned with isopropanol, and finally, the surface of the silicon wafer is dried by air blowing to obtain a preliminary SU-8 mold.

[0039] S2018, Hard Baking;

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

[0041] S202, Fabrication of the microfluidic chip body;

[0042] PDMS is a silicon-based organic polymer with excellent optical transparency, flexibility and elastomer properties. Its unique biocompatibility has led to its wide application in tissue engineering and biomedicine. In addition, PDMS can be fabricated into various microscale and nanoscale structures through a simple casting process. Its combination with soft lithography technology has enabled PDMS to achieve extensive development in the fields of microfabrication and microfluidic device design.

[0043] After the SU-8 mold is prepared, PDMS material is poured onto the mold and cured to replicate the microchannel structure on the mold surface. This process is called PDMS casting. Using the SYLGARD™ 184Silicone Elastomer Kit PDMS, PDMS and curing agent are first mixed at a mass ratio of 10:1 and stirred thoroughly until air bubbles are eliminated. The SU-8 mold is then fixed to the bottom of a petri dish using double-sided tape. The mixed PDMS is then poured into the petri dish and placed in a 0.8 MPa vacuum chamber for about 15 minutes to remove air bubbles. Finally, the petri dish is placed in a 60°C oven and heated for 2 hours to cure the PDMS. After curing, the desired area is cut and peeled off with a scalpel to obtain a PDMS microfluidic chip with a microchannel groove reservoir layer and a base plate on the surface.

[0044] The upper liquid storage layer and the lower substrate are encapsulated using an oxygen plasma bonding process. Before bonding, a 1mm punch is used to open the second opening of the liquid storage through-hole on the liquid storage layer. Then, transparent tape is repeatedly used to clean the surface. Afterward, the liquid storage layer and the substrate are placed in an oxygen plasma device and treated with oxygen plasma for 100 seconds. PDMS is usually hydrophobic. Oxygen plasma treatment can introduce active groups, such as hydroxyl (-OH) and carboxyl (-COOH) groups. 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 between the two sides, ultimately completing the fabrication 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 press-driven pump and the microfluidic chip body is completed, the microfluidic chip body and the press-driven pump are cleaned with isopropanol and deionized water respectively to remove impurities and dust from their surfaces. After oxygen plasma treatment for 100 seconds, the microfluidic chip body and the press-driven pump are precisely aligned and gently pressed to bond them together into a chip as a whole, thus 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 reservoir through the first opening, pump chamber, second opening, and reservoir through-hole. Seal the first opening, then squeeze and press the pump with your finger. The pump body deforms, driving the fluid in the serpentine channel reservoir to break through the N-type capillary burst valve, thus achieving controllable fluid drive. The fluid flow rate is related to the pressure and frequency of the press. The fluid that breaks through the N-type capillary burst valve flows out along the reservoir hole and the bottom plate through-hole. Multiple microfluidic chips based on press-driven fluid can be integrated and used in enzyme-linked immunosorbent assay (ELISA). For example, three such microfluidic chips based on press-driven fluid can be integrated into one chip. The analyte solution, enzyme-labeled antibody solution, and chromogenic substrate solution are added to the three serpentine channel reservoirs respectively. The three solutions are pumped in sequence to perform ELISA analysis.

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

[0048] Q = f·ΔV;

[0049] Where Q represents the flow rate of the press-driven pump; f represents the pressing frequency; and ΔV represents the deformation of the press-driven pump during compression.

[0050] Assuming the pressure on the press-driven pump is uniform, the function for calculating the deformation ΔV of the press-driven pump is:

[0051]

[0052] Where e is the logarithm of the natural base; E represents the elastic modulus of the press-driven pump; P represents the applied pressure; V0 represents the initial volume of the pump chamber; as the applied pressure increases, the deformation of the press-driven pump also increases, but the rate of increase gradually decreases.

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

[0054]

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

[0056] Because the N-type capillary burst valve channels are made of the same material, they have the same contact angle, thus the burst pressure P CBV The calculation function is further simplified to:

[0057]

[0058] Where, θ c The contact angle between the fluid and the N-type capillary burst valve channel.

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

[0060] Step 1: After bonding the press-driven pump, reservoir, and 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 40 μL of liquid into the serpentine channel reservoir through the second opening.

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

[0063] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0064] (1) This invention can drive microfluids in complex environments without the need for external driving equipment. The pump is driven by squeezing and pressing with the fingers to generate deformation, thereby driving the microfluids. The pump adopts a press-driven design, which eliminates the need for external power supply or complex control system, which is conducive to the integration and miniaturization of the equipment. It is especially suitable for portable devices or rapid on-site testing.

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

[0066] (3) The present invention drives the pump by squeezing and pressing with the fingers, causing the pump body to deform, thereby causing the fluid in the serpentine channel storage chamber to break through the burst pressure of the N-type capillary burst valve, and the fluid to be pumped out from the third opening. This achieves a simple, fluid-controllable fluid drive method that does not rely on external equipment, which can significantly reduce the impact of external drive equipment on the active microfluidic drive system and improve the popularity and practicality of the active microfluidic drive system in complex environments. Attached Figure Description

[0067] Figure 1 This is an exploded structural diagram of the present invention;

[0068] Figure 2 This is a schematic diagram of the combined structure of the liquid channel layer;

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

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

[0071] Figure 5 This is a schematic diagram of the structure of the drive pump mold;

[0072] Figure 6 A schematic diagram of the stress-strain curves of PDMS under different proportions of curing agent;

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

[0074] In the figure, there is a press-driven pump 1, a liquid storage layer 2, a base 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 chamber 10, a liquid storage hole 11, an N-type capillary burst valve 12, and a base plate through hole 13. Detailed Implementation

[0075] The present invention will be further described in detail below through specific embodiments, but this does not limit the scope of the present invention.

[0076] Example 1

[0077] A microfluidic chip based on pressure-driven fluid, its structure is as follows: Figures 1-4 As shown, it includes a microfluidic chip body and a press-driven pump 1 that cooperates with the microfluidic chip body; the microfluidic chip body includes a liquid storage layer 2 and a base plate 3 stacked on top of each other, 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, the first opening 4 cooperates with a second opening 5 provided on the upper surface of the liquid storage layer 2 through a pump cavity provided in the press-driven pump 1, the second opening 5 is connected to a serpentine channel liquid storage cavity 10 provided 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 has a storage hole 11 at one end away from the serpentine channel storage chamber 10. The storage hole 11 is connected to a third opening 6 on the lower surface of the bottom plate 3 through a bottom plate through hole 13. The press-driven pump 1 includes a hemispherical shell with a press sleeve on it. The first opening 4 is located at the center of the press sleeve. The heights of the serpentine channel storage chamber 10 and the N-type capillary burst valve 12 are 90µm to 110µm and 100µm, respectively. The width of the serpentine channel storage chamber 10 is 0.90mm to 1.10mm and 1mm, respectively. The total length of the serpentine channel storage chamber 10 is 38mm to 42mm and 40mm, respectively.

[0079] A method for developing a microfluidic chip includes the following steps: S1, fabrication of a press-driven pump 1; including the following steps;

[0080] S101. Drawing and printing of the mold for the press-driven pump 1;

[0081] like Figure 5As shown, the press-driven pump 1 mold is set up with two parts: base 8 and cover plate 7. The base 8 and cover plate 7 of the press-driven pump 1 mold are drawn using modeling software. The base 8 and cover plate 7 of the press-driven pump 1 mold are printed using printing technology. After printing, the base 8 and cover plate 7 are cleaned with isopropanol to remove the uncured resin on the surface of the base 8 and cover plate 7. Then, they are placed in a UV environment for curing for 10 minutes to ensure the final quality of the press-driven pump 1 mold.

[0082] S102. Evaluate the mixing ratio of curing agent and PDMS prepolymer;

[0083] In step S102, the effect of different curing agent ratios on the deformation resistance of the press-driven pump 1 is first evaluated. The selected mixture ratios are 1:10, 1:15, and 1:20, and mixtures of curing agent and PDMS prepolymer are prepared using these ratios respectively. These mixtures are made into PDMS samples with a thickness of 180 μm and heat-treated at 60°C for 2 hours. The stress-strain curves of each sample are obtained by tensile measurement of the deformation of the PDMS samples, as shown in the figure. Figure 6 As shown, the stress-strain curve results indicate 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.

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

[0085] S103, Casting molding by pressing drive pump 1;

[0086] According to the mixing ratio selected in step S102, the curing agent and PDMS prepolymer are mixed at a ratio of 1:15. The mixed mixture is then injected into the mold of the press-driven pump 1 assembled from the base 8 and the cover plate 7. The mold is placed in a 0.8 MPa vacuum chamber for 15 minutes to remove air bubbles. The mold of the press-driven pump 1 is then placed in an oven at 60°C for 2 hours to cure. 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. Fabrication of the microfluidic chip body, including the following steps:

[0088] S201, Fabrication of the microfluidic chip body mold; The SU-8 mold has a thickness of 100μm, and the specific steps include:

[0089] S2011, Mask creation;

[0090] The designed microstructure of the liquid storage layer 2 of the microfluidic chip was drawn into a two-dimensional drawing using AutoCAD software, and then fabricated into a film mask by the manufacturer. The positive and negative phase properties of the photoresist are the key to determining the mask processing and microstructure formation characteristics. Negative photoresist is used, which is the opposite of positive photoresist, which is soluble under ultraviolet light. After exposure, the negative photoresist area remains insoluble, allowing light to pass through the corresponding part of the mask channel, causing the photoresist to solidify and cross-link, forming the required microfluidic channel structure.

[0091] S2012, Pretreatment of silicon wafers;

[0092] Before preparing the SU-8 mold, the silicon wafer usually needs to be pretreated to ensure that its surface is clean and dry. After cleaning the surface of the silicon wafer with isopropanol, it can be dried in a 60°C oven for 10 minutes to effectively remove impurities, oil and other contaminants, and improve the hydrophilicity of its surface.

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

[0094] An appropriate amount of SU-82050 negative photoresist was applied to the pretreated silicon wafer. The wafer was then placed on the tray in the center of the spin coater and secured with a vacuum pump to prevent displacement during the spin coating process. A multi-step spin coating method was employed, with the first step using a spin speed of 500 rpm and a spin speed of 200 rpm. 2 Spin-coating under acceleration for 20 seconds to help the photoresist spread and form the initial film; the second step involves spin coating at 1700 rpm and 300 rpm. 2 Spin-coat under acceleration for 30 seconds. The spin-coating parameters in this step determine the thickness of the photoresist. After spin-coating, let it stand for a while to allow the surface to become smooth.

[0095] S2014, Pre-drying;

[0096] The HP10 photoresist baking machine with precise temperature control is used to heat the silicon wafer to ensure uniform adhesion of the photoresist and improve its mechanical stability. The silicon wafer is first baked at 65°C for 4 minutes, and then baked at 95°C for another 16 minutes. After baking, the silicon wafer is removed and cooled to room temperature. If wrinkles are found, it can be placed back into the photoresist baking machine. Through repeated cooling and heating processes, the surface of the silicon wafer is ensured to be smooth and wrinkle-free.

[0097] S2015, Exposure;

[0098] After the silicon wafer cools to room temperature, exposure is performed using an H94-27 (LED) microfluidic chip processing device. This device uses UV LEDs as the light source, which emits no infrared radiation and helps avoid film expansion and contraction. The operation steps include placing the transparent plate on the plate holder, starting the vacuum pump, and fixing it using the "Suction Plate" button on the operation interface. Then, the wafer stage is pulled out, and the silicon wafer and mask are placed in sequence, and the silicon wafer is fixed on the wafer stage using the "Suction Wafer" button. After pushing the wafer stage to its limit position, the exposure time is precisely controlled to 23 seconds according to the SU-8 thickness and mold structure requirements. Then, the "Stage Lift," "Contact," and "Exposure Position" buttons on the operation interface are pressed to start the exposure process.

[0099] S2016, Post-drying;

[0100] After exposure, the silicon wafer is baked again in a photoresist baking machine to further crosslink and cure the photoresist, thereby improving the mechanical properties and stability of the mold. The baking time and temperature 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 photoresist is used. The photoresist undergoes a curing and cross-linking reaction in the UV-exposed areas, while the unexposed areas remain uncured. Subsequently, the silicon wafer, after being baked and cooled, is placed in a developing solution to dissolve the unexposed parts and reveal a microchannel structure pattern. The developing time varies depending on the type and thickness of the photoresist. Typically, the processed silicon wafer is placed in a glass petri dish containing developing solution and rinsed for 8 minutes. Then, the excess developing solution on the surface of the silicon wafer is cleaned with isopropanol, and finally, the surface of the silicon wafer is dried by air blowing to obtain a preliminary SU-8 mold.

[0103] S2018, Hard Baking;

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

[0105] S202, Fabrication of the microfluidic chip body;

[0106] PDMS is a silicon-based organic polymer with excellent optical transparency, flexibility and elastomer properties. Its unique biocompatibility has led to its wide application in tissue engineering and biomedicine. In addition, PDMS can be fabricated into various microscale and nanoscale structures through a simple casting process. Its combination with soft lithography technology has enabled PDMS to achieve extensive development in the fields of microfabrication and microfluidic device design.

[0107] After the SU-8 mold is prepared, PDMS material is poured onto the mold and cured to replicate the microchannel structure on the mold surface, a process known as PDMS casting. Using the SYLGARD™ 184Silicone Elastomer Kit PDMS, PDMS and curing agent are mixed at a mass ratio of 10:1 and stirred thoroughly until air bubbles are eliminated. The SU-8 mold is then fixed to the bottom of a petri dish using double-sided tape. The mixed PDMS is then poured into the petri dish, placed in a 0.8 MPa vacuum chamber, and left to stand for about 15 minutes to remove air bubbles. Finally, the petri dish is placed in a 60°C oven and heated for 2 hours to cure the PDMS. After curing, the desired area is cut and peeled off using a scalpel to obtain a PDMS microfluidic chip with a reservoir layer 2 and a base plate 3 on the surface, featuring microchannel grooves.

[0108] The upper liquid storage layer 2 and the lower substrate 3 are encapsulated using an oxygen plasma bonding process. Before bonding, a 1mm punch is used to open the second opening 5 of the liquid storage through-hole 9 on the liquid storage layer 2. Then, transparent tape is repeatedly used to clean the surface. Afterward, the liquid storage layer 2 and the substrate 3 are placed in an oxygen plasma device and treated with oxygen plasma for 100 seconds. PDMS is usually hydrophobic. Oxygen plasma treatment can introduce active groups, such as hydroxyl (-OH) and carboxyl (-COOH) groups. 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 between the two sides, ultimately completing the fabrication 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 press-driven pump 1 and the microfluidic chip body is completed, the microfluidic chip body and the press-driven pump 1 are cleaned with isopropanol and deionized water respectively to remove impurities and dust from their surfaces. After oxygen plasma treatment for 100 seconds, the microfluidic chip body and the press-driven pump 1 are precisely aligned and gently pressed to bond them together into a chip whole, thus completing the assembly of the microfluidic chip;

[0110] S4. Use of the microfluidic chip; 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 10 through the first opening 4, pump chamber, second opening 5, and reservoir through-hole 9. Seal the first opening 4, and then squeeze and press the pump 1 with your finger. The pump body deforms, driving the fluid in the serpentine channel reservoir 10 to break through the N-type capillary burst valve 12, realizing controllable fluid drive. The fluid flow rate is related to the pressure and frequency of the press. The fluid that breaks through the N-type capillary burst valve 12 flows out along the reservoir hole 11, bottom plate through-hole 13, and third opening 6. Multiple microfluidic chips based on press-driven fluid can be integrated and used in enzyme-linked immunosorbent assay (ELISA). For example, three such microfluidic chips based on press-driven fluid can be integrated into one chip for use. The analyte solution, enzyme-labeled antibody solution, and chromogenic substrate solution are added to the three serpentine channel reservoirs 10 respectively. The three solutions are pumped in sequence to perform ELISA analysis.

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

[0112] Q = f·ΔV;

[0113] Where Q represents the flow rate of the press-driven pump 1; f represents the pressing frequency; and ΔV represents the deformation of the press-driven pump 1 during pressing.

[0114] Assuming the pressure on the press-driven pump 1 is uniform, the function for calculating the deformation ΔV of the press-driven pump 1 is:

[0115]

[0116] Where 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; as the applied pressure increases, the deformation of the press-driven pump 1 also increases, and the rate of increase gradually decreases.

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

[0118]

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

[0120] Because the N-type capillary burst valve uses the same material for all 12 channels, they have the same contact angle, thus the burst pressure P... CBV The calculation function is further simplified to:

[0121]

[0122] Where, θ c The contact angle between the fluid and the 12-channel N-type capillary burst valve.

[0123] Example 2

[0124] A microfluidic chip based on pressure-driven fluid is fabricated by means of: S1, fabrication of pressure-driven pump 1; S2, fabrication of microfluidic chip body; S3, assembly of microfluidic chip based on pressure-driven fluid; S4, use of microfluidic chip based on pressure-driven fluid.

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

[0126] S101. Drawing and printing the mold for the press-driven pump 1;

[0127] The press-driven pump 1 is cast from PDMS (polydimethylsiloxane) material. During fabrication, the mold for the press-driven pump 1 is first designed using Solidworks 3D modeling software, such as... Figure 5 As shown, the mold for the press-driven pump 1 consists of two layers: a base 8 and a cover plate 7. Printing technology is used to ensure high precision and good surface finish, making it suitable for use as a PDMS mold. After printing, isopropyl alcohol is used for cleaning to remove uncured resin from the surface, and then the mold is placed in a UV environment for 10 minutes to ensure the final quality of the mold.

[0128] S102, Evaluate the ratio of curing agent to PDMS prepolymer mixture;

[0129] To evaluate the effect of different curing agent ratios on the deformation resistance of the press-driven pump 1, mixtures of curing agent and PDMS prepolymer were prepared at ratios of 1:10, 1:15, and 1:20. These mixtures were then used to prepare PDMS samples with a thickness of 180 μm and heat-treated at 60 °C for 2 h. The deformation of the PDMS samples was measured by tensile testing to obtain stress-strain curves, such as... Figure 6As shown; according to the stress-strain curve results, the elastic modulus of PDMS can be changed by adjusting the ratio of curing agent. The lower the elastic modulus, the softer the material, and vice versa.

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

[0131] S103, Casting molding by pressing drive 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. The mold is then placed in a 0.8 MPa vacuum chamber for 15 minutes to remove air bubbles. The mold is then placed in a 60°C oven for 2 hours to cure. After curing, the base 8 and cover plate 7 of the mold are separated, and the press drive pump 1 is removed.

[0133] S2. The fabrication of a microfluidic chip body having a serpentine channel liquid storage chamber 10 and an N-type capillary burst valve 12 includes the following steps:

[0134] S201, Mold fabrication; The SU-8 mold is 100μm thick, and the specific steps include:

[0135] S2011, Mask creation;

[0136] In this embodiment, AutoCAD software is used to draw the designed microstructure of the liquid storage layer 2 of the microfluidic chip into a two-dimensional drawing, which is then fabricated into a film mask by the manufacturer. The positive and negative phase properties of the photoresist are the key to determining the mask processing and microstructure formation characteristics. In this embodiment, negative photoresist is used. In contrast to positive photoresist, which is soluble under ultraviolet light, the negative photoresist area remains insoluble after exposure, allowing light to pass through the corresponding part of the mask channel, which leads to the photoresist curing and cross-linking to form the required microfluidic channel structure.

[0137] S2012, Pretreatment of silicon wafers;

[0138] Before preparing the SU-8 mold, the silicon wafer usually needs to be pretreated to ensure that its surface is clean and dry. After cleaning the surface of the silicon wafer with isopropanol, it can be dried in a 60°C oven for 10 minutes to effectively remove impurities, oil and other contaminants, and improve the hydrophilicity of its surface.

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

[0140] An appropriate amount of SU-82050 negative photoresist was applied to the pretreated silicon wafer. The wafer was then placed on the tray in the center of the spin coater and secured with a vacuum pump to prevent displacement during the spin coating process. A multi-step spin coating method was employed, with the first step using a spin speed of 500 rpm and a spin speed of 200 rpm. 2 Spin-coating under acceleration for 20 seconds to help the photoresist spread and form the initial film; the second step involves spin coating at 1700 rpm and 300 rpm. 2 Spin-coat under acceleration for 30 seconds. The spin-coating parameters in this step determine the thickness of the photoresist. After spin-coating, let it stand for a while to allow the surface to become smooth.

[0141] S2014, Pre-drying;

[0142] The HP10 photoresist baking machine with precise temperature control is used to heat the silicon wafer to ensure uniform adhesion of the photoresist and improve its mechanical stability. The silicon wafer is first baked at 65°C for 4 minutes, and then baked at 95°C for another 16 minutes. After baking, the silicon wafer is removed and cooled to room temperature. If wrinkles are found, it can be placed back into the photoresist baking machine. Through repeated cooling and heating processes, the surface of the silicon wafer is ensured to be smooth and wrinkle-free.

[0143] S2015, Exposure;

[0144] After the silicon wafer cools to room temperature, exposure is performed using an H94-27 (LED) microfluidic chip processing device. This device uses UV LEDs as the light source, which emits no infrared radiation and helps avoid film expansion and contraction. The operation steps include placing the transparent plate on the plate holder, starting the vacuum pump, and fixing it using the "Suction Plate" button on the operation interface. Then, the wafer stage is pulled out, and the silicon wafer and mask are placed in sequence, and the silicon wafer is fixed on the wafer stage using the "Suction Wafer" button. After pushing the wafer stage to its limit position, the exposure time is precisely controlled to 23 seconds according to the SU-8 thickness and mold structure requirements. Then, the "Stage Lift," "Contact," and "Exposure Position" buttons on the operation interface are pressed to start the exposure process.

[0145] S2016, Post-drying;

[0146] After exposure, the silicon wafer is baked again in a photoresist baking machine to further crosslink and cure the photoresist, thereby improving the mechanical properties and stability of the mold. The baking time and temperature 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] This embodiment uses SU-8 photoresist. The photoresist undergoes a curing and cross-linking reaction in the UV-exposed areas, while the unexposed areas remain uncured. Subsequently, the silicon wafer, after being baked and cooled, is placed in a developing solution to dissolve the unexposed parts, revealing a microchannel structure pattern. The developing time varies depending on the type and thickness of the photoresist. Typically, the processed silicon wafer is placed in a glass petri dish containing developing solution and rinsed for 8 minutes. Then, excess developing solution on the surface of the silicon wafer is cleaned with isopropanol, and finally, the surface of the silicon wafer is dried by air blowing to obtain a preliminary SU-8 mold.

[0149] S2018, Hard Baking;

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

[0151] S202, Fabrication of the Microfluidic Chip Body

[0152] PDMS is a silicon-based organic polymer with excellent optical transparency, flexibility and elastomer properties. Its unique biocompatibility has led to its wide application in tissue engineering and biomedicine. In addition, PDMS can be fabricated into various microscale and nanoscale structures through a simple casting process. Its combination with soft lithography technology has enabled PDMS to achieve extensive development in the fields of microfabrication and microfluidic device design.

[0153] After the SU-8 mold is prepared, PDMS material is poured onto the mold and cured to replicate the microchannel structure on the mold surface. This process is called PDMS casting. In this embodiment, SYLGARD™ 184Silicone Elastomer Kit PDMS is used. First, PDMS and curing agent are mixed at a mass ratio of 10:1 and stirred thoroughly until air bubbles are eliminated. The SU-8 mold is fixed to the bottom of the petri dish using double-sided tape. Then, the mixed PDMS is poured into the petri dish and placed in a 0.8 MPa vacuum hood for about 15 minutes to remove air bubbles. Finally, the petri dish is placed in a 60°C oven and heated for 2 hours to cure the PDMS. After curing, the required area is cut and peeled off with a scalpel to obtain a PDMS microfluidic chip with a liquid storage layer 2 and a base plate 3 on the surface with microchannel grooves.

[0154] In this embodiment, an oxygen plasma bonding process is used to encapsulate the upper liquid storage layer 2 and the lower substrate 3. Before bonding, a 1mm punch is used to open the second opening 5 of the liquid storage through hole 9 on the liquid storage layer 2. Then, transparent tape is repeatedly used to clean the surface. After that, the liquid storage layer 2 and the substrate 3 are placed in an oxygen plasma device and treated with oxygen plasma for 100 seconds. PDMS is usually hydrophobic. Oxygen plasma treatment can introduce active groups, such as hydroxyl (-OH) and carboxyl (-COOH). 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 between the two sides, ultimately completing the fabrication of the PDMS microfluidic chip body.

[0155] S3. Assembly of microfluidic chips based on pressure-driven fluid;

[0156] After completing the fabrication of the press-driven pump 1 and the microfluidic chip body, the two components are assembled into an integrated microfluidic chip. First, the microfluidic chip and the press-driven pump 1 are cleaned with isopropanol and deionized water respectively to remove impurities and dust from the surface. After oxygen plasma treatment for 100 seconds, the microfluidic chip and the press-driven pump 1 are precisely aligned and gently pressed to bond them together into a chip. This completes the fabrication of the press-driven fluid microfluidic chip body.

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

[0158] When using a pressure-driven fluid microfluidic chip: First, use a pipette to take an appropriate amount of solution and add it to the serpentine channel reservoir 10 through the first opening 4, pump chamber, second opening 5, and reservoir through-hole 9. Seal the first opening 4, and then squeeze the pump 1 with your finger to drive the fluid in the serpentine channel reservoir 10 to break through the N-type capillary burst valve 12, thus achieving controllable fluid drive. The fluid flow rate is related to the pressure and frequency of the finger press. The fluid that breaks through the N-type capillary burst valve 12 flows out along the reservoir hole 11, bottom plate through-hole 13, and third opening 6. Multiple pressure-driven fluid microfluidic chips can be integrated and used in enzyme-linked immunosorbent assay (ELISA). For example, three such pressure-driven fluid microfluidic chips can be integrated into one chip. The analyte solution, enzyme-labeled antibody solution, and chromogenic substrate solution can be added to the three serpentine channel reservoirs 10 respectively. The three solutions can be pumped in sequence to perform ELISA analysis.

[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 within the protection scope of the present invention.

Claims

1. A microfluidic chip based on pressure-driven fluid, characterized in that, The device includes a microfluidic chip body and a press-driven pump that cooperates with the microfluidic chip body. The microfluidic chip body includes a liquid storage layer and a base plate stacked on top of each other. The liquid storage layer is connected to the press-driven pump. The press-driven pump has a first opening, which cooperates with a second opening on the upper surface of the liquid storage layer through a pump cavity disposed within the press-driven pump. The second opening is connected to a serpentine channel liquid storage cavity disposed on the lower surface of the liquid storage layer through a liquid storage through-hole. 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. A liquid storage hole is provided at one end of the N-type capillary burst valve away from the serpentine channel liquid storage cavity. The liquid storage hole is connected to a third opening on the lower surface of the base plate through a base plate through-hole. The press-driven pump includes a hemispherical housing, on which a press sleeve is provided, and a first opening is located at the center of the press sleeve.

2. The microfluidic chip based on pressure-driven fluid according to claim 1, characterized in that, The height of the serpentine channel liquid storage chamber and the N-type capillary burst valve is 90um to 110um, the width of the serpentine channel liquid storage chamber is 0.90mm to 1.10mm, and the total length of the serpentine channel liquid storage chamber is 38mm to 42mm.

3. A method for preparing and using a microfluidic chip according to any one of claims 1-2, characterized in that, The process includes the following steps: S1, preparation of the press-driven pump; S2, preparation of the microfluidic chip body; S3, assembly of the microfluidic chip; S4, use of the microfluidic chip.

4. The preparation and use method according to claim 3, characterized in that, In step S1, the preparation of the press-driven pump includes the following steps; S101. Drawing and printing the mold for the press-driven pump; The press-driven pump mold is set up as a base and a cover plate. The base and cover plate of the press-driven pump mold are drawn using modeling software. The base and cover plate of the press-driven pump mold are printed using printing technology. After printing, the base and cover plate are cleaned with isopropanol to remove the uncured resin on the surface of the base and cover plate. Then, they are placed in a UV environment for curing. S102. Evaluate the mixing ratio of curing agent and PDMS prepolymer; S103, Casting molding using a press-driven pump; According to the mixture ratio selected in step S102, the mixed mixture is injected into the press drive pump mold assembled with the base and cover plate, and placed in a vacuum hood; then the cast press drive pump mold is placed in an oven for curing, and after curing, the base and cover plate of the press drive pump mold are separated, and the cured press drive pump is taken out.

5. The preparation and use method according to claim 3, characterized in that, In step S2, the fabrication of the microfluidic chip body includes the following steps: S201. Fabrication of the microfluidic chip body mold, which includes the following steps: S2011. Fabrication of the photomask; S2012. Pretreatment of the silicon wafer; S2013. Spin coating of photoresist; S2014. Pre-baking; S2015. Exposure; S2016. Post-baking; S2017. Development; S2018. Hard baking; S202, Fabrication of the microfluidic chip body.

6. The preparation and use method according to claim 3, characterized in that, In step S3, the assembly of the microfluidic chip includes the following steps: After the preparation of the press-driven pump and the microfluidic chip body is completed, the microfluidic chip body and the press-driven pump are cleaned with isopropanol and deionized water respectively to remove impurities and dust from their surfaces. Immediately after oxygen plasma treatment, the microfluidic chip body and the press-driven pump are precisely aligned and gently pressed to bond them together into a chip as a whole, thus 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, squeeze and press the pump with your finger. The pump body deforms, driving the fluid in the serpentine channel reservoir to break through the N-type capillary burst valve, thus achieving controllable fluid drive. The fluid flow rate is related to the pressure and frequency of the press.

7. The preparation and use method according to claim 6, characterized in that, In step S4, the approximate calculation function for the fluid flow rate is: Q = f·ΔV; Where Q represents the flow rate of the press-driven pump; f represents the pressing frequency; and ΔV represents the deformation of the press-driven pump during compression. Assuming the pressure on the press-driven pump is uniform, the function for calculating the deformation ΔV of the press-driven pump is: Where e is the logarithm of the natural base; E represents the elastic modulus of the press-driven pump; P represents the applied pressure; and V0 represents the initial volume of the pump chamber.

8. The preparation and use method according to claim 7, characterized in that, In step S4, the pressure barrier of the N-type capillary burst valve depends on the fluid surface tension, contact angle, and the shape of the N-type capillary burst valve channel. Since the cross-section of the N-type capillary burst valve channel is rectangular, the burst pressure P of the N-type capillary burst valve... CBV The calculation function is: Where γ1 represents the surface tension of the fluid; θ l θ represents the contact angle between the fluid and the left side of the N-type capillary burst valve channel. r θ represents the contact angle between the fluid and the right side of the N-type capillary burst valve passage. t θ represents the contact angle between the fluid and the top of the N-type capillary burst valve passage. b The contact angle between the fluid and the bottom of the N-type capillary burst valve channel is indicated; w and h represent the width and depth of the N-type capillary burst valve channel, respectively. Because the N-type capillary burst valve channels are made of the same material, they have the same contact angle, thus the burst pressure P CBV The calculation function is further simplified to: Where, θ c The contact angle between the fluid and the N-type capillary burst valve channel.

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