A liquid metal electrode microfluidic chip for fusion and a manufacturing process thereof

Abstract

The application provides a large height-width ratio liquid metal electrode microfluidic chip for fusion and a manufacturing process thereof, and belongs to the technical field of microfluidics.The application solves the problem that the existing large height-width ratio liquid metal electrode microfluidic chip faces great challenges in the photoetching process.The chip comprises a chip substrate and a PDMS plate, the PDMS plate is arranged on the chip substrate, the PDMS plate is provided with an electrode channel and a fluid channel, the fluid channel comprises a first fluid channel, a second fluid channel and a third fluid channel, the end of the first fluid channel is communicated with the second fluid channel and forms a cross structure with the second fluid channel, the end of the third fluid channel is communicated with the second fluid channel and forms a T-shaped cross structure with the second fluid channel, and the cross structure is arranged at the front end of the T-shaped cross structure.The application is mainly used for droplet microfluidic fusion technology.

Description

Technical Field

[0001] This invention belongs to the field of microfluidics technology, and in particular relates to a microfluidic chip with a large aspect ratio liquid metal electrode for fusion and its fabrication process. Background Technology

[0002] Droplet microfluidics, a subclass of microfluidics, generates and manipulates sub-nanolithic droplets in microdevices. This technology is one of the most efficient techniques for isolating and culturing single microbial cells in closed environments. Droplet microfluidics offers several unique benefits for microbiological research. First, by encapsulating microorganisms in droplets, small numbers of cells, or even single cells, can be confined to isolated environments; interspecies competition and bias caused by differences in growth rates are eliminated, facilitating the recovery of rare or slow-growing microorganisms from complex ecosystems; and the rapid accumulation of metabolites in droplets facilitates the activation of concentration-dependent processes. Second, droplet microfluidics enables rapid droplet production and large-scale droplet analysis at rates up to 20,000 droplets per second, providing possibilities for ultra-high-throughput identification, screening, and strain improvement of microorganisms. Third, in droplet microfluidics, configurable channel designs and embedded control modules enable precise manipulation of droplets, including fusion, mixing, splitting, long-term incubation, and sorting. These methods can introduce various detection reagents or stimuli into microorganisms, create well-controlled and variable culture environments, or selectively collect improved microbial strains.

[0003] Droplet fusion technology plays a crucial role in microfluidics. Through electrowetting, surface tension control, and optical or acoustic methods, it enables the generation, movement, and fusion of droplets, allowing for high-precision, rapid, flexible, and high-throughput chemical reactions, biological analysis, and material synthesis in liquids ranging from nanoliters to microliters. This technology is widely used in biomedical analysis, chemical synthesis, drug screening, environmental monitoring, and materials science. By precisely controlling the droplet fusion process using external conditions, it significantly reduces sample and reagent consumption, improving experimental efficiency and sensitivity.

[0004] Currently, commonly used fusion electrodes are ITO, copper electrodes, and liquid metal electrodes such as gallium, which are liquid at room temperature. These electrodes either cannot be coplanar with the flow field and cannot provide a strong electric field, or require multiple photolithography steps with excessively high alignment requirements, or it is difficult to achieve a sufficiently small and precise spacing between the electrode channel and the fluid channel. Furthermore, in order to meet the droplet fusion requirements in microfluidic chips, and to reduce the electric field requirements and maintain liquid phase stability during droplet fusion in the chip, the electrode channels and fluid channels of the chip need to have a large aspect ratio. However, microfluidic chips with large aspect ratio liquid metal electrodes face significant challenges in the photolithography process. Summary of the Invention

[0005] In view of this, the present invention aims to propose a high aspect ratio liquid metal electrode microfluidic chip for fusion and its fabrication process, so as to solve the problem that existing high aspect ratio liquid metal electrode microfluidic chips face great challenges in the photolithography process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a microfluidic chip for fusion of high aspect ratio liquid metal electrodes, comprising a chip substrate and a PDMS board, wherein the PDMS board is disposed on the chip substrate, and electrode channels and fluid channels are formed on the PDMS board, wherein the fluid channels include a first fluid channel, a second fluid channel and a third fluid channel, wherein the end of the first fluid channel is connected to the second fluid channel and forms a cross structure with the second fluid channel, and the end of the third fluid channel is connected to the second fluid channel and forms a T-shaped cross structure with the second fluid channel, wherein the cross structure is disposed at the front end of the T-shaped cross structure, wherein the electrode channels include two first electrode channels and two second electrode channels, wherein the two first electrode channels are symmetrically disposed on the upper sides of the T-shaped cross structure, and the two second electrode channels are symmetrically disposed on the lower sides of the T-shaped cross structure, wherein the ends of the two first electrode channels and the ends of the two second electrode channels are spaced apart from the T-shaped cross structure.

[0007] Furthermore, the front ends of the first fluid channel, the second fluid channel, and the third fluid channel are respectively provided with a first injection port, a second injection port, and a third injection port.

[0008] Furthermore, filter arrays are provided at the first injection port, the second injection port, and the third injection port.

[0009] Furthermore, a collection port is provided at the end of the second fluid channel.

[0010] Furthermore, electrodes are provided in both the first electrode channel and the second electrode channel, and extension electrodes are provided at the front end of both the first electrode channel and the front end of the second electrode channel. Through holes that match the extension electrodes are provided on the PDMS board, and the extension electrodes are inserted into the through holes of the PDMS board and connected to the electrodes.

[0011] Furthermore, the electrode is made of a tin-bismuth alloy.

[0012] Furthermore, both the first and second fluid channels at the cross-shaped structure are provided with variable-diameter constriction ports.

[0013] Furthermore, both the second and third fluid channels at the front end of the T-shaped cross structure are provided with variable diameter compression ports.

[0014] This invention also provides a fabrication process for a microfluidic chip with a large aspect ratio liquid metal electrode for fusion, which includes the following steps:

[0015] Step 1: The silicon wafers used for photolithography are cleaned and blown away with high-pressure nitrogen gas to remove moisture.

[0016] Step 2: Place the cleaned silicon wafer obtained in Step 1 into a plasma machine for plasma treatment;

[0017] Step 3: Remove the silicon wafer processed in Step 2 and perform a normal soft lithography process to obtain a preliminary template;

[0018] Step 4: Perform plasma treatment on the preliminary template obtained in Step 3 to remove the problem of the developer being unable to completely wash it off due to the large aspect ratio.

[0019] Step 5: Pour PDMS material into the template obtained in Step 4, remove the vacuum and cure it to obtain a PDMS board. Cut and punch holes in the PDMS board and take out the part of the required shape.

[0020] Step 6: After hydrophilic treatment, the PDMS board obtained in step 5 is bonded to the corresponding chip substrate to obtain a microfluidic chip, and left for 2 hours to allow the hydrophilic effect to be deactivated.

[0021] Step 7: Treat the electrode channels of the microfluidic chip obtained in Step 6 with the corresponding hydrophobic reagent and dry them so that the channel walls are specially treated. Place the chip on a heating platform and put the liquid metal into the electrode channels to complete the processing of the liquid metal electrode chip with a large aspect ratio channel.

[0022] Furthermore, the photolithography process in step 3 includes the following steps:

[0023] Step 3.1: Spin coat the photoresist onto the silicon wafer and spread it evenly using a spin coater;

[0024] Step 3.2: Pre-baking, place the silicon wafer after homogenization on the heating stage;

[0025] Step 3.3: Exposure. After the pre-baked silicon wafer has cooled, the mask is aligned with the silicon wafer, and a suitable exposure time is selected for photolithography in the photolithography machine.

[0026] Step 3.4: Post-baking, place the photolithographically etched silicon wafer on the heating stage;

[0027] Step 3.5: Development. After the silicon wafers have cooled down after baking, they are immersed in the developing solution and then placed in an ultrasonic cleaner.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention provides a microfluidic chip with a large aspect ratio liquid metal electrode for fusion and its fabrication process. The microfluidic chip uses PDMS to construct fluid channels and electrode channels, and improves the photolithography and cleaning process to complete the photolithography of the large aspect ratio channel, so that the large aspect ratio channel can be formed. This reduces the electric field requirement and maintains the stability of the liquid phase when performing droplet fusion in the microfluidic chip, making the droplet fusion process stable and easy to achieve.

[0030] 2. This invention provides a fusion-grade liquid metal electrode microfluidic chip with a large aspect ratio, wherein the electrode material is a tin-bismuth alloy. The tin-bismuth alloy is solid under normal conditions and has a low melting point, which not only makes the electrode easy to process, but also allows the metal to become liquid under heating, making it easy to fill the electrode channels. Moreover, it is solid at room temperature, making it easy to store and preserve, without leveling requirements, and easy to clean the fluid channels. It can ensure that the electrode channels and fluid channels are coplanar, that is, the entire fusion microfluidic chip can be obtained in one photolithography. The overall process is simplified while reducing the alignment difficulty and greatly improving the electric field strength and the accuracy of the placement position. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a schematic diagram of the overall structure of a high aspect ratio liquid metal electrode microfluidic chip for fusion according to the present invention;

[0033] Figure 2 This is an enlarged schematic diagram of the mask and mask portion structure in the fabrication process of a high aspect ratio liquid metal electrode microfluidic chip for fusion as described in this invention.

[0034] Figure 3 This is a microscopic view of a silicon wafer template used in the fabrication process of a high aspect ratio liquid metal electrode microfluidic chip for fusion, as described in this invention.

[0035] Figure 4 This is a schematic diagram of a platform for constructing PCR microreaction chambers using a high aspect ratio liquid metal electrode microfluidic chip for fusion as described in this invention in practical applications.

[0036] 1-Chip substrate, 2-PDMS board, 3-Electrode channel, 4-Fluid channel, 5-Extended electrode, 6-First fluid channel, 7-Second fluid channel, 8-Third fluid channel, 9-First electrode channel, 10-Second electrode channel, 11-First injection port, 12-Second injection port, 13-Third injection port, 14-Collection port, 15-Flow pump, 16-Microscope, 17-Signal generator. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other, and the described embodiments are only some embodiments of the present invention, not all embodiments.

[0038] See Figure 1-4 This embodiment describes a microfluidic chip for fusion of high aspect ratio liquid metal electrodes. It includes a chip substrate 1 and a PDMS board 2. The PDMS board 2 is disposed on the chip substrate 1 and has electrode channels 3 and fluid channels 4. The fluid channels 4 include a first fluid channel 6, a second fluid channel 7, and a third fluid channel 8. The end of the first fluid channel 6 communicates with the second fluid channel 7 and forms a cross-shaped structure with it. The end of the third fluid channel 8 communicates with the second fluid channel 7 and forms a T-shaped cross-shaped structure with it. The cross-shaped structure is disposed at the front end of the T-shaped cross-shaped structure. The electrode channels 3 include two first electrode channels 9 and two second electrode channels 10. The two first electrode channels 9 are symmetrically disposed on the upper sides of the T-shaped cross-shaped structure, and the two second electrode channels 10 are symmetrically disposed on the lower sides of the T-shaped cross-shaped structure. The ends of the two first electrode channels 9 and the two second electrode channels 10 are spaced apart from the T-shaped cross-shaped structure.

[0039] In this embodiment, PDMS is used to construct the fluid channel 4 and the electrode channel 3. By improving the photolithography and cleaning process, the photolithography of the channel with a large aspect ratio is completed, so that the channel with a large aspect ratio can be formed. This reduces the electric field requirement and maintains the stability of the liquid phase when performing droplet fusion in the microfluidic chip, making the droplet fusion process stable and easy to achieve.

[0040] In this embodiment, the maximum width of the fluid channel 4 is 35 micrometers, the maximum width of the electrode channel 3 is 50 micrometers, the minimum distance between the electrode channel 3 and the fluid channel 4 is 10 micrometers, and the overall height is 45 micrometers, which allows the droplets to fuse in small sizes.

[0041] In this embodiment, forward droplets are generated between the first fluid channel 6 and the second fluid channel 7 through a cross-shaped structure, and additional droplets are generated between the second fluid channel 7 and the third fluid channel 8 through a T-shaped cross structure.

[0042] In this embodiment, the front ends of the first fluid channel 6, the second fluid channel 7 and the third fluid channel 8 are respectively provided with a first injection port 11, a second injection port 12 and a third injection port 13.

[0043] In this embodiment, filter arrays are provided at the first injection port 11, the second injection port 12, and the third injection port 13. The filter arrays are rectangular arrays with the spacing between the rectangular arrays reduced from 25 micrometers to 10 micrometers. Through three steps, the final filtration is achieved to prevent impurities or particles from entering the channel, thus playing a filtering role.

[0044] In this embodiment, a collection port 14 is provided at the end of the second fluid channel 7, which is used to collect the fused droplets.

[0045] In this embodiment, electrodes are provided in both the first electrode channel 9 and the second electrode channel 10. An extension electrode 5 is provided at the front end of both the first electrode channel 9 and the front end of the second electrode channel 10. A through hole matching the extension electrode 5 is provided on the PDMS plate 2. The extension electrode 5 is inserted into the through hole of the PDMS plate 2 and connected to the electrode. The signal generator is connected to the extension electrode 5 and transmits a signal to the electrode in the electrode channel 3 through the extension electrode 5. Thus, the droplet fusion process in the T-shaped cross structure is precisely controlled by the electric field formed by the electrode in the electrode channel 3.

[0046] In this embodiment, the electrode material is a tin-bismuth alloy. The tin-bismuth alloy is solid under normal conditions and has a low melting point. This not only makes the electrode easy to process, but also allows the metal to become liquid under heating, making it easy to fill the electrode channels. Moreover, it is solid at room temperature, making it easy to store and preserve. It does not have level requirements and is easy to clean the fluid channel 4. It can ensure that the electrode channel 3 and the fluid channel 4 are coplanar, that is, the entire fused microfluidic chip can be obtained in one photolithography. The overall process is simplified, reducing the alignment difficulty and greatly improving the electric field strength and the accuracy of the placement position.

[0047] In this embodiment, both the first fluid channel 6 and the second fluid channel 7 at the cross structure are provided with a variable diameter constriction port, and both the second fluid channel 7 and the third fluid channel 8 at the front end of the T-shaped cross structure are provided with a variable diameter constriction port. The variable diameter constriction port is provided so that the droplet can be cut off as soon as possible at the variable diameter constriction port.

[0048] In this embodiment, the second fluid channel 7 at the rear end of the cross structure expands the flow channel as a whole, reserving space for droplet deformation.

[0049] In this embodiment, both the second fluid channel 7 and the third fluid channel 8 at the T-shaped intersection structure are provided with meandering serpentine channels, which are used to offset some of the fluid pressure changes.

[0050] This embodiment also provides a fabrication process for a high aspect ratio liquid metal electrode microfluidic chip for fusion, which includes the following steps:

[0051] Step 1: The silicon wafers used for photolithography are cleaned and blown away with high-pressure nitrogen gas to remove moisture.

[0052] Step 2: Place the cleaned silicon wafer obtained in Step 1 into a plasma machine for plasma treatment;

[0053] Step 3: Remove the silicon wafer processed in Step 2 and perform a normal soft lithography process to obtain a preliminary template;

[0054] Step 4: Perform plasma treatment on the preliminary template obtained in Step 3 to remove the problem of the developer being unable to completely wash it off due to the large aspect ratio.

[0055] Step 5: Pour PDMS material into the template obtained in Step 4, remove the vacuum and cure it to obtain PDMS board 2. Cut and punch holes in the PDMS board 2 and take out the part of the required shape.

[0056] Step 6: After hydrophilic treatment, the PDMS board 2 obtained in step 5 is bonded to the corresponding chip substrate 1 to obtain a microfluidic chip, and placed for 2 hours to allow the hydrophilic effect to be deactivated.

[0057] Step 7: Treat the electrode channel 3 of the microfluidic chip obtained in Step 6 with the corresponding hydrophobic reagent and dry it so that the channel wall is specially treated. Place it on a heating platform and put liquid metal into the electrode channel 3 to complete the processing of the liquid metal electrode chip with a large aspect ratio channel.

[0058] In this embodiment, during the cleaning process in step 1, the components are immersed in the corresponding solutions in the order of acetone, alcohol, and deionized water, and then placed in an ultrasonic cleaner for 2 minutes.

[0059] In step 2 of this embodiment, the silicon wafer needs to be placed in a plasma machine. Preferably, the plasma treatment is performed at an oxygen flow rate of 40 sccm and a power of 90W for 1 minute. The pretreatment plasma treatment is to make the photoresist bond more tightly to the silicon wafer, so that the photoresist can maintain high strength during the ultrasonic process under a large aspect ratio.

[0060] In this embodiment, negative photoresist (hereinafter referred to as negative photoresist) SU-8 3035 is used for photolithography.

[0061] In this embodiment, step 3 of the photolithography process includes the following steps:

[0062] Step 3.1: Spin coat the photoresist onto the silicon wafer and spread it evenly using a spin coater;

[0063] Step 3.2: Pre-baking, place the silicon wafer after homogenization on the heating stage;

[0064] Step 3.3: Exposure. After the pre-baked silicon wafer has cooled, the mask is aligned with the silicon wafer, and a suitable exposure time is selected for photolithography in the photolithography machine.

[0065] Step 3.4: Post-baking, place the photolithographically etched silicon wafer on the heating stage;

[0066] Step 3.5: Development. After the silicon wafers have cooled down after baking, they are immersed in the developing solution and then placed in an ultrasonic cleaner.

[0067] In this embodiment, the pre-baking in step 3.2 preferably involves placing the silicon wafer after photoresist homogenization on a heating stage, raising the temperature from room temperature to 65°C and holding it for 10 minutes, then raising the temperature from 65°C to 95°C and holding it for 35 minutes to allow the photoresist to spread evenly.

[0068] In this embodiment, the post-baking step 3.4 preferably involves placing the exposed silicon wafer on a heated stage. The temperature is increased from room temperature to 65°C and held for 20 minutes, then increased from 65°C to 95°C and held for 15 minutes. This fully promotes the crosslinking reaction of the negative photoresist, ensuring that the photoresist has good chemical resistance and mechanical stability after development.

[0069] In the development process of step 3.5 in this embodiment, the silicon wafer after post-baking is cooled and placed in the negative photoresist developer solution propylene glycol monomethyl ether acetate, and ultrasonic treatment is performed in an ultrasonic cleaner. Since the pretreatment process involves plasma treatment, the bonding effect between the photoresist and the silicon wafer can be better. After cleaning with the negative photoresist developer solution, no white flocculent matter is precipitated when cleaning with IPA isopropanol.

[0070] In this embodiment, after the silicon wafer is developed, it needs to be placed in a plasma machine in step 4. Preferably, the oxygen flow rate is maintained at 100 sccm and the power at 100W for 25 minutes to clean away any remaining, difficult-to-clean parts, thus obtaining a complete template. The partial structure of the template under a microscope is shown in the figure below. Figure 3 As shown, plasma treatment after development is performed to remove residual epoxy monomers that are difficult to remove by the developer from the template by high-energy plasma (the negative adhesive is composed of epoxy monomers and photoinitiators, which undergo a cross-linking reaction under ultraviolet light, causing the epoxy monomers to connect, and the negative adhesive developer can dissolve the epoxy monomers), so that the template with a large aspect ratio channel can be clearly washed out.

[0071] In step 5 of this embodiment, PDMS prepolymer is poured onto the template and submerges the top of the mold. Vacuum is then drawn to completely remove air bubbles from the PDMS prepolymer. After curing at 80°C for 2 hours, the template is peeled off to obtain PDMS board 2. After hydrophilic treatment, PDMS board 2 is attached to chip substrate 1 and then heated at 80°C for 1 hour for bonding.

[0072] In this embodiment, the ratio of PDMS to curing agent in the PDMS prepolymer is 10:1. Stir thoroughly for 5 minutes until a large number of bubbles are generated to ensure thorough mixing.

[0073] In this embodiment, the template is silanized before PDMS is poured in. Trimethylchlorosilane reagent is used for treatment. 200 μL of trimethylchlorosilane reagent is pipetted into a vacuum vessel, kept at -85 kPa, and treated for 3 min. After the pressure is restored to normal, the vessel is left to stand for 5 min without opening the lid to allow the reagent to settle evenly to the surface.

[0074] In step 6 of this embodiment, the PDMS board 2 and the corresponding chip substrate 1 are placed in a plasma machine for plasma treatment, and then placed on a hot plate for heating to perform thermal bonding to obtain a microfluidic chip, and left for 2 hours to make the hydrophilic effect ineffective.

[0075] In this embodiment, the chip substrate used in the bonding process is float glass, which is ultrasonically cleaned in the order of acetone, alcohol, and deionized water, and then dried with high-pressure nitrogen.

[0076] In this embodiment, the plasma treatment is performed at an oxygen flow rate of 30 sccm and a power of 100W for 1 minute, followed by heating on a hot plate.

[0077] In this embodiment, the plasma-treated PDMS board 2 and the chip substrate 1 are thermally bonded on a hot plate and heated at 80°C for 2 hours.

[0078] In this embodiment, in step 7, a hydrophobic agent is introduced into the electrode channel 3, and the solvent is evaporated by heating on a hot plate. The needle is removed, a section of the electrode channel 3 is inserted, and the needle is placed on a heating platform. The molten alloy on the surface is placed into the electrode channel 3 from the other end of the electrode channel 3. Capillary action is used to make the molten liquid metal flow towards the needle tip, thus constructing the electrode channel 3.

[0079] In this embodiment, a hydrophobic agent (which can be replaced by automotive glass hydrophobic agent) is injected into the electrode channel to ensure that the channel is filled. Then, it is placed in a hot plate in a fume hood and heated at 90°C for 2 hours to allow the hydrophobic agent to evaporate.

[0080] In this embodiment, hydrophobic treatment is used to enhance the capillary effect during subsequent injection of molten alloy.

[0081] In this embodiment, a tin-bismuth alloy is used. This alloy has a melting point of 70°C. It can be solid at room temperature to ensure its connection strength and prevent leakage, which is convenient for experiments and cleaning. At the same time, it can be easily filled into the channel when heated, which is easy to process.

[0082] In this embodiment, a hollow iron rod is used as the extension electrode 5, which can be removed from the flat needle head.

[0083] In this embodiment, the hydrophobic microfluidic chip is placed on a hot plate at 105°C and preheated for 10 min (PDMS has low thermal conductivity) to raise the overall temperature to 105°C. One end of the tin-bismuth alloy is heated to melt and introduced into one end of the electrode channel. Under the action of capillary action, the molten liquid metal quickly and evenly fills the electrode channel and contacts the extension electrode 5 to form a circuit.

[0084] In this embodiment, in order to stabilize the extension electrode and prevent the electrode channel (maximum 50 micrometers) from being broken due to stretching when the alligator clip wire is connected to the extension electrode during the power-on process, AB glue is used to fix the extension electrode 5. The two phases of AB glue are mixed in a 1:1 ratio, stirred and then applied to the extension electrode 5 to increase stability.

[0085] The high aspect ratio liquid metal electrode microfluidic chip for fusion described in this invention can be applied to the construction of microreaction chambers, solution and material synthesis, etc. In this embodiment, the construction of a PCR reaction microchamber is taken as an example: the corresponding oil phase solution is introduced into the first injection port 11 as the external phase, and the system that needs to be fused to form a whole, mixed with each other and reacted to shorten the storage time is introduced into the second injection port 12 and the third injection port 13. By adjusting the corresponding flow rate and voltage, the construction of the droplet microreaction system chamber can be realized at the T-shaped cross structure.

[0086] The microfluidic chip fabricated using the above process is used to construct PCR microreaction chambers. A schematic diagram of the platform for constructing PCR microreaction chambers in practical applications is shown below. Figure 4 As shown, this fusion experimental platform consists of three flow pumps 15, a microfluidic chip, a signal generator 17, and a microscope 16.

[0087] Three flow pumps 15 generate thrust on the syringe, causing the liquid in the syringe to be injected into the microfluidic chip through the first injection port 11, the second injection port 12, and the third injection port 13, respectively. The first injection port 11 is controlled by the flow pump 15 to inject the oil phase, while the second injection port 12 and the third injection port 13 are controlled to inject the corresponding water phase.

[0088] In this embodiment, the syringe and the microfluidic chip are mechanically connected via a flat needle, a Teflon tube, and an injection tube.

[0089] In this embodiment, fluorinated oil is used as the oil phase, and one of the two aqueous phases is the PCR reaction system, probe and primer 1, and the other aqueous phase is the DNA dilution solution and primer 2.

[0090] In this embodiment, a suitable flow rate is selected so that the droplets from the two droplet generation ports can be arranged sequentially at the electrodes.

[0091] In this embodiment, the microfluidic chip is electrically connected to the signal generator 17 via alligator clip wires.

[0092] In this embodiment, due to the arrangement of the electrode channel 3 and its distance from the fluid channel 4, the electric field requirement is reduced. If alligator clip wires are used to connect the electrodes on opposite sides of the fluid channel respectively, the voltage can be reduced to below 25V. When the voltage is applied, the droplets merge and can be observed in real time at the microscope 16, and the flow rate of the flow pump 15 can be adjusted.

[0093] In this embodiment, the fused droplets were collected through a subsequent collection port, placed into an eight-tube array, and then placed in a PCR instrument for corresponding PCR thermal cycling. The fluorescence effect was then observed under a fluorescence microscope.

[0094] The PCR mentioned above is polymerase chain reaction, which can be understood as an in vitro DNA replication technology. The PCR thermal cycle involves the unwinding of the DNA double strand, the binding of primers to single strands, and the reverse extension of primers to replicate DNA at a specific temperature.

[0095] The embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A liquid metal electrode microfluidic chip for fusion, characterized in that: It includes a chip substrate (1) and a PDMS plate (2) arranged on the chip substrate (1), the PDMS plate (2) is provided with an electrode channel (3) and a fluid channel (4), the fluid channel (4) includes a first fluid channel (6), a second fluid channel (7) and a third fluid channel (8), the end of the first fluid channel (6) communicates with the second fluid channel (7) and forms a cross structure with the second fluid channel (7), the end of the third fluid channel (8) communicates with the second fluid channel (7) and forms a T-shaped cross structure with the second fluid channel (7), the cross structure is arranged at the front end of the T-shaped cross structure, the electrode channel (3) includes two first electrode channels (9) and two second electrode channels (10), the two first electrode channels (9) are symmetrically arranged on the upper two sides of the T-shaped cross structure, and the two second electrode channels (10) are symmetrically arranged on the lower two sides of the T-shaped cross structure, the ends of the two first electrode channels (9) and the two second electrode channels (10) are arranged at intervals with the T-shaped cross structure, and electrodes are arranged in the first electrode channel (9) and the second electrode channel (10), and the material of the electrode is tin-bismuth alloy.

2. The liquid metal electrode microfluidic chip for fusion according to claim 1, wherein: The front ends of the first fluid channel (6), the second fluid channel (7) and the third fluid channel (8) are respectively provided with a first injection inlet (11), a second injection inlet (12) and a third injection inlet (13).

3. The liquid metal electrode microfluidic chip for fusion according to claim 2, wherein: The first injection inlet (11), the second injection inlet (12) and the third injection inlet (13) are provided with a filter array.

4. The liquid metal electrode microfluidic chip for fusion according to claim 2, wherein: The end of the second fluid channel (7) is provided with a collection port (14).

5. The liquid metal electrode microfluidic chip for fusion according to claim 2, wherein: The front ends of the first electrode channel (9) and the second electrode channel (10) are provided with an extension electrode (5), the PDMS plate (2) is provided with a through hole matched with the extension electrode (5), and the extension electrode (5) is inserted into the through hole of the PDMS plate (2) and connected with the electrode.

6. The liquid metal electrode microfluidic chip for fusion according to claim 1, wherein: The first fluid channel (6) and the second fluid channel (7) at the cross structure are provided with a variable-diameter constriction.

7. The liquid metal electrode microfluidic chip for fusion according to claim 1, wherein: The second fluid channel (7) and the third fluid channel (8) at the front end of the T-shaped cross structure are provided with a variable-diameter constriction.

8. A process for fabricating a microfluidic chip for fusion of liquid metal electrodes as claimed in any one of claims 1 to 7, wherein: It includes the following steps: Step 1: The silicon wafer for photoetching is cleaned, and high-pressure nitrogen is used to blow it away to make it away from the humid state; Step 2: The cleaned silicon wafer obtained in step 1 is put into a plasma machine for plasma treatment; Step 3: The silicon wafer treated in step 2 is taken out and subjected to normal soft photoetching process to obtain a preliminary template; Step 4: The preliminary template obtained in step 3 is subjected to plasma treatment to remove the condition that the developing solution is difficult to completely clean; Step 5: The template obtained in step 4 is subjected to PDMS material pouring, vacuum extraction and solidification to obtain a PDMS plate (2), and the PDMS plate (2) after cutting and punching is taken out to obtain the required shape part; Step 6: After hydrophilic treatment, the PDMS board (2) obtained in step 5 is bonded to the corresponding chip substrate (1) to obtain a microfluidic chip, and placed for 2 hours to make the hydrophilic effect ineffective. Step 7: Treat the electrode channel (3) of the microfluidic chip obtained in Step 6 with the corresponding hydrophobic reagent and dry it so that the channel wall is specially treated. Place it on the heating platform, put the liquid metal into the electrode channel (3), heat one end of the tin-bismuth alloy to melt, and pass it into one end of the electrode channel (3). Under the action of capillary action, the molten liquid metal quickly and evenly fills the electrode channel (3) to complete the processing of the liquid metal electrode chip of the channel.

9. The process of claim 8, wherein the process further comprises: The photolithography process in step 3 includes the following steps: Step 3.1: Spin coat the photoresist onto the silicon wafer and spread it evenly using a spin coater; Step 3.2: Pre-baking, place the silicon wafer after homogenization on the heating stage; Step 3.3: Exposure. After the pre-baked silicon wafer has cooled, the mask is aligned with the silicon wafer, and a suitable exposure time is selected for photolithography in the photolithography machine. Step 3.4: Post-baking, place the photolithographically etched silicon wafer on the heating stage; Step 3.5: Development. After the silicon wafers have cooled down after baking, they are immersed in the developing solution and then placed in an ultrasonic cleaner.

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