Microfluidic chip surface hydrophobic treatment method and equipment

Abstract

The invention discloses a micro-fluidic chip surface hydrophobic treatment method and equipment. The method comprises the following steps: placing at least one micro-fluidic chip on a placing table in a vacuum cavity; starting a vacuum generation system to extract gas in the vacuum cavity until a preset vacuum degree range is reached; introducing process gas; voltage is applied to the electrode plate in the vacuum cavity through a plasma generator, the process gas is ionized into plasma, and polymer films are deposited on the inner surface and the outer surface of the micro-fluidic chip; and when the coating time reaches a preset deposition duration, breaking the vacuum of the vacuum cavity to obtain the target micro-fluidic chip after surface hydrophobic treatment. Therefore, on the premise of adjusting parameters of plasma treatment, the same surface modification method can be used for various different base materials, hydrophobic modification is performed on the inside and outside of the chip at the same time, and the consistency of the hydrophobic surface modification layer is effectively kept.

Description

Technical Field

[0001] The invention relates to the technical field of surface engineering, and in particular to a method and equipment for hydrophobic treatment of the surface of a microfluidic chip. Background Art

[0002] In the development of microfluidic droplet chips, the uniformity and modification strength of the chip surface contact angle are very important for the process of using microfluidic chips for monodisperse microspheres or hydrogel balls. Taking PDMS-glass chips as an example, high-energy physical treatments are usually performed on the surfaces of PDMS (Polydimethylsiloxane) and glass materials, such as oxygen plasma treatment, to enhance the surface hydrophilicity and activate functional groups to achieve chemical cross-linking. However, after plasma treatment, the surface properties of PDMS change but in a transient state, and the hydrophobicity is restored in a short time. The contact angle after recovery is not uniform, and the temperature and time of thermal renaturation are difficult to estimate.

[0003] In this regard, the current mainstream chip channel modification methods also include chemical vapor deposition of fluorosilane agents, Parylene CVD vapor deposition and other vapor deposition modification methods under vacuum conditions, but this modification method is difficult to ensure that the inner wall of the channel can be uniformly and stably modified in a closed microchannel. You can also use various hydrophobic modification liquids and inject them into the chip channel through a syringe pump, but make sure that the excess modification liquid is blown dry by continuous air, otherwise, the modification liquid remaining in the microchannel will cause blockage of the chip microchannel.

[0004] In the above scheme, the commonly used fluorination treatment can be hydrophobic but reduces the adhesion and adhesion of the material surface, resulting in loose bonding. Sealing methods such as thermal bonding will cause liquid leakage after pressure is applied. The solution is to partially remove the hydrophobic surface modification layer at the seal, but it will increase the complexity and instability of the production process, and it is difficult to maintain the consistency of the hydrophobic surface modification layer. Summary of the invention

[0005] The present invention provides a method and device for hydrophobic treatment of the surface of a microfluidic chip, which solves the technical problem that the prior art usually performs hydrophobic treatment by fluorination treatment combined with local removal of the hydrophobic surface modification layer at the sealing part, which increases the complexity and instability of the production process and makes it difficult to maintain the consistency of the hydrophobic surface modification layer.

[0006] The present invention provides a method for hydrophobic treatment of the surface of a microfluidic chip, comprising:

[0007] Placing at least one microfluidic chip on a placement table in the vacuum chamber;

[0008] Turning on the vacuum generating system to extract the gas in the vacuum chamber until the preset vacuum degree range is reached;

[0009] Introducing process gas;

[0010] Applying voltage to the electrode plate in the vacuum chamber through a plasma generator to ionize the process gas into plasma so as to deposit a polymer film on the inner and outer surfaces of the microfluidic chip;

[0011] When the coating time reaches the preset deposition time, the vacuum chamber is broken to obtain a target microfluidic chip after the surface hydrophobic treatment.

[0012] Optionally, the method further comprises:

[0013] Measuring the surface contact angle of the target microfluidic chip at multiple points;

[0014] If all the surface contact angles are not within the expected contact angle range, adjusting the output power of the plasma generator according to a preset power gradient until any of the surface contact angles is within the expected contact angle range;

[0015] The coating time is adjusted according to a preset time gradient until all the surface contact angles are within the expected contact angle range.

[0016] Optionally, the method further comprises:

[0017] If all the surface contact angles are not within the expected contact angle range and the output power has been adjusted, then measuring the surface contact angles of the target microfluidic chip after the process gas is introduced at multiple preset flow rates to determine the flow adjustment direction;

[0018] Adjusting the flow rate of the process gas according to the flow rate adjustment direction and the preset flow rate gradient until the surface contact angle reaches a peak value;

[0019] Jump to the step of adjusting the output power of the plasma generator according to the preset power gradient.

[0020] Optionally, the method further comprises:

[0021] If the coating time has been adjusted to the maximum time and any of the surface contact angles is not within the expected contact angle range, the vacuum generating system is driven to increase the vacuum degree in the vacuum chamber according to a preset vacuum gradient until all the surface contact angles are within the expected contact angle range.

[0022] Optionally, the process gas is a fluorinated olefin gas or a volatile gas of hexamethyldisiloxane.

[0023] Optionally, the flow rate range of the process gas is SCCM-SCCM.

[0024] Optionally, the vacuum degree range is Pa-Pa.

[0025] Optionally, the output power range of the plasma generator is WW.

[0026] Optionally, the method further comprises:

[0027] If the material of the microfluidic chip is a thermoplastic polymer, the maximum temperature in the vacuum chamber is maintained at less than °C.

[0028] The present invention also provides a microfluidic chip surface hydrophobic treatment device, comprising a control system, a vacuum generation system, a vacuum cavity, a plasma generator and a gas cylinder;

[0029] The gas cylinder is loaded with process gas;

[0030] The vacuum chamber is connected to the vacuum generating system and the gas cylinder through pipelines, and the vacuum chamber is provided with an exhaust valve;

[0031] The control system is electrically connected to the plasma generator and the gas cylinder, respectively, and is used to control the plasma generator and the input of the process gas;

[0032] The plasma generator is electrically connected to the electrode plate in the vacuum chamber to provide a high-frequency voltage.

[0033] It can be seen from the above technical solutions that the present invention has the following advantages:

[0034] The present invention places at least one microfluidic chip on a placement table in a vacuum chamber; starts a vacuum generation system to extract the gas in the vacuum chamber until a preset vacuum range is reached; introduces process gas; applies voltage to an electrode plate in the vacuum chamber through a plasma generator to ionize the process gas into plasma so as to deposit a polymer film on the inner and outer surfaces of the microfluidic chip; when the coating time reaches a preset deposition time, the vacuum chamber is broken to obtain a target microfluidic chip after surface hydrophobic treatment. Thus, under the premise of adjusting the parameters of the plasma treatment, the same surface modification method can be used for a variety of different substrates, and the inside and outside of the chip are simultaneously hydrophobically modified, effectively maintaining the consistency of the hydrophobic surface modification layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0036] Figure 1 A flow chart of the steps of a method for hydrophobic treatment of the surface of a microfluidic chip provided by an embodiment of the present invention;

[0037] Figure 2 A schematic structural diagram of a microfluidic chip surface hydrophobic treatment device provided in an embodiment of the present invention.

[0038] Figure numerals: 1. control system; 2. vacuum generating system; 3. vacuum chamber; 4. plasma generator; 5. gas cylinder; 31. placement table; 32. electrode plate; 51. air inlet valve; 52. exhaust valve. DETAILED DESCRIPTION

[0039] Surface engineering is a sub-discipline of materials science that deals with the surfaces of solid substances. It applies to chemistry, mechanical engineering and electrical engineering (particularly relevant to semiconductor manufacturing, microfluidic chip fabrication). Surface modification is the modification of the behavior of a material surface by introducing physical, chemical or biological properties that differ from those originally found on the material surface. Such modifications are usually performed on solid materials, but examples of modifications of specific liquid surfaces can also be found. Modifications can be performed by different methods to change a wide range of properties of the surface, such as: roughness, hydrophilicity, surface charge, surface energy, biocompatibility and reactivity. Surface engineering involves changing the properties of the surface phase to reduce degradation over time. This is achieved by making the surface robust to the environment in which it is used. In the field of microfluidic chip and micro-nano system manufacturing, polydimethylsiloxane (PDMS) is one of the main polymer hydrophobic materials widely used in microfluidic devices. It has a naturally hydrophobic surface with a water contact angle greater than 100°. Since the uniformity and modification intensity of the chip surface contact angle are very important for the process of using microfluidic chips for monodisperse microspheres or hydrogel spheres, in order to ensure the consistency of the particle size of droplets generated by the chip during the production process, a multi-channel parallel injection molding step emulsification structure is usually adopted to avoid the unstable hydrophobic modification step on the chip surface. While each droplet generation channel generates stable and uniform droplets at a relatively low speed, the efficiency of droplet generation is guaranteed by multi-channel parallel connection, which greatly increases the production cost of monodisperse microspheres.

[0040] In the process of using microfluidic droplet chips for monodisperse microspheres or hydrogel balls, in order to generate droplets of uniform particle size, a multi-channel parallel method of a stepped emulsification structure is generally used. Each droplet generation channel generates stable and uniform droplets at a relatively low speed, and the efficiency of droplet generation is ensured by multi-channel parallel connection. This method will encounter some problems when generating some monomer-polymerized microspheres or hydrogel balls. For example, after the polyacrylamide monomer water phase is configured, a certain degree of polymerization will occur during the entire droplet generation process, causing the relevant physical properties of the monomer water phase to gradually change during the droplet generation process as the droplet generation time increases, thereby affecting the consistency of the generated droplets. At the same time, the viscosity of the water phase will also change during the polymerization of the water phase. Under extreme conditions, such as excessive water phase flow or low water phase surface tension, general droplet generation chips may not be able to generate droplets. Generally, microfluidic droplet chips are made of double-sided PDMS hydrophobic material. After plasma (active gas such as oxygen or air) treatment, the plasma-treated surface is bonded to form the cavity of the chip flow channel. The plasma treatment in the flow channel reduces the contact angle of the PDMS material surface from originally >100° to about 30°, making it difficult to generate droplets in droplet chips that have not undergone PDMS thermal renaturation. However, the method of restoring the surface properties of PDMS by heating and baking has strong uncertainty, and the state of material surface recovery cannot be quantitatively controlled. After thermal renaturation of each channel for droplet generation, the properties of the PDMS material surface in the channel are different to a certain extent. In addition, PDMS material has a large adsorption capacity for biological molecules. If the generated droplets contain biological molecules such as antibodies, the surface contact angle of PDMS will gradually decrease with the adsorption of biological molecules, making it difficult to generate droplets stably. At present, the mainstream chip channel modification methods also include chemical vapor deposition of fluorosilane agents, Parylene CVD vapor deposition and other vapor deposition modification methods under vacuum conditions, but this modification method is difficult to ensure that the inner wall of the channel can be uniformly and stably modified in a closed microchannel. You can also use various hydrophobic modification liquids and inject them into the chip channel through a syringe pump, but make sure that the excess modification liquid is blown dry by continuous air, otherwise, the modification liquid remaining in the microchannel will cause blockage of the chip microchannel.

[0041] To this end, the embodiment of the present invention provides a method and device for hydrophobic treatment of the surface of a microfluidic chip, which is used to solve the technical problem that the prior art usually performs hydrophobic treatment by fluorination treatment combined with local removal of the hydrophobic surface modification layer at the sealing part, which increases the complexity and instability of the production process and makes it difficult to maintain the consistency of the hydrophobic surface modification layer. While being able to perform batch surface modification on the inner wall of the microchannel pipeline of the microfluidic chip, it can also be applied to a variety of substrates, such as PDMS, glass, PMMA (Polymethyl Methacrylate), PS (Polystyrene), PET (Polyethylene Terephthalate), PP (Polypropylene), COC (Cyclic Olefin Copolymer) / COP (Cyclic Olefin Polymer) and other thermoplastic polymers for hydrophobic modification of the surface and channel interior of mass-produced microfluidic products.

[0042] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] See also Figure 1 , Figure 1 A flow chart of the steps of a method for hydrophobic treatment of the surface of a microfluidic chip provided in an embodiment of the present invention.

[0044] The present invention provides a method for hydrophobic treatment of the surface of a microfluidic chip, comprising:

[0045] Step 101, placing at least one microfluidic chip on a placement table in a vacuum chamber;

[0046] Microfluidic chip refers to a tiny chip that integrates the basic operating units of biological and chemical laboratories (such as sample preparation, reaction, separation, detection, etc.), which can use microchannels (usually at the micrometer level) to manipulate tiny volumes (nanoliter or picoliter level) of fluid. Material selection can include but is not limited to PDMS, glass, PMMA, PS, PET, PP and COC / COP.

[0047] In this embodiment, when the microfluidic chips need to be subjected to surface hydrophobic treatment, they are placed in batches on a placement table in a vacuum chamber and fixed, and the vacuum chamber is closed.

[0048] At the same time, the relevant instrument parameters involved in the hydrophobic treatment of the surface of the microfluidic chip are initialized, such as the vacuum degree required for the vacuum generation system to be extracted, the deposition time, the output power of the plasma generator and the process gas flow rate.

[0049] Step 102, start the vacuum generating system to extract the gas in the vacuum chamber until the preset vacuum degree range is reached;

[0050] After the microfluidic chip is placed and the vacuum chamber is closed, the vacuum generating system connected to the vacuum chamber through a pipeline extracts the gas in the vacuum chamber according to the set instrument parameters until the set value within the preset vacuum range, such as 20Pa, is reached.

[0051] The vacuum generating system is a device used to extract gas in a closed space to reduce the gas pressure in the space to a vacuum state below atmospheric pressure. The type of vacuum generating system can be a rotary vane vacuum generating system, a diffusion vacuum generating system or a Roots vacuum generating system.

[0052] Optionally, the vacuum degree ranges from 20 Pa to 100 Pa. The vacuum degree can be increased or decreased according to the different material types of the microfluidic chip and whether the surface contact angle meets the standard as adjustment conditions, and the initial value can be set to 20 Pa.

[0053] Step 103, introducing process gas;

[0054] In this embodiment, a gas source or a liquid source is connected to the vacuum chamber, and a process gas is introduced into the vacuum chamber at a certain flow rate to provide a material basis for subsequent plasma formation.

[0055] In the specific implementation, since microfluidic chips made of different materials have different characteristics, the fluorine content and fluorine-containing groups introduced into the process gas on their surface are also different. The specific experimental evaluation can be carried out based on the bond position on the material surface and the degree of bonding with the film.

[0056] Optionally, the process gas is a fluorinated olefin gas or a volatile gas of hexamethyldisiloxane.

[0057] Optionally, the flow rate of the process gas ranges from 0 SCCM to 300 SCCM.

[0058] It should be noted that the fluorinated olefin gas can be a hydrofluorocarbon gas such as C3F6, C3F8, C4F6, C4F8 or C5F8.

[0059] Since the properties of the material surface depend on the surface morphology and the chemical composition of the outer layer of the surface, and the electronegativity of all elements is the highest, and the van der Waals atomic radius is the smallest except for hydrogen, and the atomic polarizability is the lowest, the bond energy of the single bond formed by the fluorine atom and the carbon atom is the highest compared with the bond energy of the single bond formed by the carbon atom and other atoms, and the bond length is short, the fluorine atom and the carbon atom can form a very strong covalent bond. The perfluoroalkyl chain formed by the introduction of fluorine has a unique structure. The molecular skeleton of the straight-chain perfluoroalkane is a zigzag carbon chain surrounded by fluorine atoms. Due to the small van der Waals atomic radius of the fluorine atom, it just wraps the carbon skeleton tightly, making the carbon chain less susceptible to external interference, and at the same time making the entire molecular chain more rigid and presenting a spiral conformation. This spatial barrier makes the carbon chain of perfluoroalkanes well protected by the surrounding fluorine atoms, and even the smallest atom is difficult to wedge in. In addition, due to the extremely strong electronegativity of fluorine atoms, the C-F bond has a strong polarity, and the shared electron pair is strongly biased towards the fluorine atom, so that the fluorine atom carries excess negative charge, forming a negative charge protection layer, which makes it difficult for negatively charged nucleophiles to approach carbon atoms, making it difficult for perfluoroalkanes to react chemically. After perfluoroalkanes are excited by high-energy radio frequency plasma, their stable chemical bonds are broken, thereby inserting CF2 small molecules into the groups on the surface of the material, thereby forming a uniform fluorinated modified layer deposition film. Due to the stability of the CF bond, the stability and effectiveness of the modified layer film are much higher than other physical, chemical, electrostatic and other surface modification methods. Therefore, introducing fluorine is an effective way to reduce the surface free energy of materials, and perfluoroalkane compounds have unique chemical stability and low surface free energy.

[0060] Step 104, applying voltage to the electrode plate in the vacuum chamber by a plasma generator to ionize the process gas into plasma so as to deposit a polymer film on the inner and outer surfaces of the microfluidic chip;

[0061] A plasma generator is a device that can generate plasma. Plasma is the fourth state of matter. It is composed of a large number of free electrons, ions and neutral particles, and is electrically neutral as a whole. Plasma generators generate plasma by applying sufficient energy to the gas to ionize the gas, such as radio frequency (RF) plasma generators. The active components of plasma include: ions, electrons, atoms, free active groups, excited nuclides (metastable states), photons, etc. Plasma treatment is to change the surface properties of the sample by physical and chemical reactions such as oxidation, reduction, cracking, cross-linking and polymerization by utilizing the properties of these spark components, thereby optimizing the surface properties of the material and achieving the purposes of cleaning, modification, etching, etc.

[0062] Optionally, the output power of the plasma generator ranges from 0 W to 1000 W. The power frequency may be 13.56 MHz.

[0063] In this embodiment, an electrode plate is also provided on the other side of the vacuum chamber opposite to the placement table, and is electrically connected to the electrode plate through a plasma generator. A voltage is applied to the electrode plate according to a preset power parameter to excite the process gas using the alternating electric field generated by the radio frequency power supply to ionize it into plasma. After discharge, the circuit will automatically adjust the voltage to an appropriate value to ensure stable discharge of the circuit. At this time, the active groups (such as free radicals) in the plasma will react chemically with the atoms or molecules on the surface of the microfluidic chip, and deposit on the inner and outer surfaces of the microfluidic chip to generate a polymer film. The vacuum chamber can reduce the interference of impurity gases. Under a lower pressure environment, the molecular mean free path of the process gas increases, so that the collision interference they receive during the ionization process is reduced, which is more conducive to the generation and stability of plasma.

[0064] Taking polydimethylsiloxane (PDMS) thin film deposition as an example, if the process gas is an organic compound containing silicon and carbon, the active groups in the plasma will initiate a polymerization reaction on the chip surface. These active groups are first adsorbed on the chip surface, and then react with the subsequent active groups or gas molecules to gradually form polymer chains, and finally deposited as polymer films on the inner and outer surfaces of the microfluidic chip.

[0065] Step 105 , when the coating time reaches a preset deposition time, the vacuum chamber is broken to obtain a target microfluidic chip after the surface hydrophobic treatment.

[0066] Since plasma coating requires a certain amount of time, the deposition time can be preset for automatic operation, which can be set to 200s, 250s, 300s, 350s, etc. When the plasma coating time reaches the preset deposition time, the exhaust valve connected to the vacuum chamber can be driven to open, the vacuum chamber can be broken, and the door of the vacuum chamber can be opened to take out the target microfluidic chip after the surface hydrophobic treatment.

[0067] In actual operation, the above process can be achieved by manually placing and removing the microfluidic chip, or by automated operations such as coordinated actions of a robotic arm, etc., and the embodiments of the present invention do not limit this.

[0068] In an embodiment of the present invention, when the process gas is changed to precursor deposits such as hexafluoropropylene (C3F6) and octafluoropropane (C3F8), the surface of the sample treated by the plasma enhanced chemical vapor deposition process will polymerize into an ultra-thin fluorinated polymer film. The structure and composition of these films were characterized using Fourier transform infrared and angle-resolved X-ray photoelectron spectroscopy. The polymer film has more -CF3 groups and has a strongly branched structure. The water contact angle increases with film thickness and process gas flow, resulting in a high surface F:C ratio of the copolymer film and a decrease in surface energy, thereby forming a hydrophobic surface.

[0069] The following is a specific comprehensive example of the process of steps 101-105 of the present invention, in which different process gases, inlet flow rates, output powers and vacuum degrees are set respectively, and the sample is a microfluidic chip:

[0070] By placing the sample on the stage in the vacuum chamber, with the chip opening facing upward, closing the machine door, running the machine program, and evacuating the chamber, when the vacuum degree reaches the set value, the RF plasma begins to glow for plasma cleaning, and the process gas hexafluoropropylene (C3F6) is introduced into the chamber, and the air flow rate is adjusted to 300SCCM, the power is 300w, the vacuum degree is 20Pa, and the plasma vacuum cleaning time is 360s. After the plasma cleaning program is completed and the glow is extinguished, the sample can be taken out after the vacuum chamber returns to normal pressure. The contact angle of the treated sample surface measured using a contact angle meter can reach 107°.

[0071] Place the sample on the stage in the vacuum chamber, with the chip opening facing upward, close the machine door, run the machine program, evacuate the chamber, and after the vacuum reaches the set value, the RF plasma starts glowing for plasma cleaning. Introduce process gases hexafluoropropylene (C3F6) and octafluoropropane (C3F8) into the chamber at the same time, and adjust the two gas flow rates to 100SCCM and 200SCCM, power 300w, vacuum degree 20Pa, plasma vacuum cleaning time 360s, wait until the plasma cleaning program is finished and the glow is extinguished, and the vacuum chamber is restored to normal pressure before taking out the sample. The contact angle of the treated sample surface measured by the contact angle meter can reach 106°. Among them, hexafluoropropylene (C3F6) is the main polymer, and octafluoropropane (C3F8) can control the uniformity of polymerization.

[0072] Place the sample on the stage in the vacuum chamber, with the chip opening facing upward, close the machine switch door, and replace the gas cylinder in the machine with a liquid gas inlet cylinder that helps volatile liquid reagents, so that the reagent vapor volatilized by the liquid reagent can enter the vacuum chamber. Run the machine program, evacuate the chamber, and after the vacuum reaches the set value, the RF plasma begins to glow for plasma cleaning. Introduce working liquid hexamethyldisiloxane (HMDSO) into the chamber, and adjust the air flow rate to 100SCCM, power 300w, vacuum 20Pa, plasma vacuum cleaning time 600s, wait until the plasma cleaning program ends and the glow goes out, and the vacuum chamber returns to normal pressure before taking out the sample. The contact angle of the treated sample surface measured using a contact angle meter can reach 111°.

[0073] In the embodiment of the present invention, due to the difference of vacuum chamber, vacuum generation system, material of microfluidic chip, output power of plasma generator or the influence of connecting pipe, etc., the surface treatment effect of microfluidic chip may be different. To this end, further treatment can be carried out according to the size of surface contact angle in the following manner so that the surface contact angle of microfluidic chip reaches the expected range of preset contact angle. Taking PDMS and glass microfluidic chip as an example, the unbonded glass slide and PDMS block are respectively placed in fixed positions in the vacuum wall, and the initial value of the machine coating deposition parameter is set to 400w, 150s, 20Pa, 100sccm, and surface treatment is carried out to obtain the treated target microfluidic chip.

[0074] In one example of the present invention, the method further includes:

[0075] Measure the surface contact angle of the target microfluidic chip at multiple points;

[0076] If the contact angles of all surfaces are not within the expected contact angle range, adjusting the output power of the plasma generator according to a preset power gradient until the contact angle of any surface is within the expected contact angle range;

[0077] The coating time is adjusted according to the preset time gradient until the contact angle of all surfaces is within the expected contact angle range.

[0078] In this embodiment, the target microfluidic chip is measured at multiple points to determine the uniformity and angle between the contact angles of multiple points. If the contact angles of all surfaces are not within the expected range of the contact angle, the power is increased by several gradient values, such as 450w, 500w, 550, 600w, 1000w, and the contact angle is measured after the gradient experiment coating to see whether the measured surface contact angle reaches the expected value. If the single point reaches the expected value, the coating time is adjusted to increase the uniformity of the surface coating, such as the time is adjusted to 200s, 250s, 300s, 350s, etc., until the consistency of the surface contact angle of the measured product reaches the expected value.

[0079] In one example of the present invention, the method further includes:

[0080] If all surface contact angles are not within the expected contact angle range and the output power has been adjusted, the surface contact angles of the target microfluidic chip after the process gas is introduced at multiple preset flow rates are measured to determine the flow adjustment direction;

[0081] The flow rate of the process gas is adjusted according to the flow adjustment direction and the preset flow gradient until the surface contact angle reaches a peak value;

[0082] Jump to the step of adjusting the output power of the plasma generator according to the preset power gradient.

[0083] In this embodiment, if increasing the output power of the plasma generator alone has no obvious effect on the contact angle of the product surface, a gradient experiment should be conducted on the bidirectional parameters of increasing and decreasing the gas flow rate to determine the adjustment direction of the gas flow rate, such as setting the gradient experiment to 50sccm, 75sccm, 100sccm, 125sccm, 150sccm, etc., and measuring the contact angle after processing the product. The contact angle test is used to find the adjustment direction of the flow parameter. After determining the direction, the flow parameter is finely adjusted. After adjusting the flow parameter to the current optimal value, the machine processing power parameter is adjusted in the same way so that the final flow rate and the gas flow parameter reach the best match. After the product surface contact angle reaches the expected effect, the coating deposition time is adjusted by adjusting the coating time as above.

[0084] In one example of the present invention, the method further includes:

[0085] If the coating time has been adjusted to the maximum time and there is any surface contact angle that is not within the expected contact angle range, the vacuum generating system is driven to increase the vacuum degree in the vacuum chamber according to the preset vacuum gradient until all surface contact angles are within the expected contact angle range.

[0086] In this embodiment, the vacuum degree in the cavity is related to the density of the ionized active gas in the cavity, and is generally set to 20Pa. If the uniformity of the contact angle on the surface of the product still cannot meet the requirements by adjusting the coating time, you can try to increase the vacuum degree while increasing the coating time.

[0087] The length of the coating time depends on the temperature tolerance of the chip. For example, glass and PDMS materials are not sensitive to temperature, so there is no clear requirement for the temperature rise during long-term treatment in the vacuum chamber. At this time, the temperature in the vacuum chamber can be gradually increased until the contact angle of all surfaces is within the expected contact angle range.

[0088] In one example of the present invention, the method further includes:

[0089] If the material of the microfluidic chip is a thermoplastic polymer, the maximum temperature in the vacuum chamber is maintained at less than 70°C.

[0090] In this embodiment, the thermoplastic polymer can be PMMA, PS, COC, PC or TPU, etc. Since the thermoplastic polymer will cause the microfluidic chip to be deformed due to heat if the coating time is long, affecting the use of the product. Therefore, the coating time of such microfluidic chips should not be too long, or water cooling equipment should be added around the vacuum cavity to keep the maximum temperature in the cavity below 70°C.

[0091] In addition, to further ensure the performance of the microfluidic chip, the maximum temperature can be controlled below 65°C.

[0092] In another example of the present invention, the surface treatment process parameters of the product material can be determined by exploring the coating deposition using the product material, and then the bonded small batch products such as 5-10 pieces are placed in a fixed position in a certain layer in the vacuum chamber, and the surface treatment parameters explored before are used to treat the small batch products. After treatment, the contact angle meter is also used to measure the different surface contact angles on the same product and the surface contact angles of products at different positions. The processing power, gas flow, processing time, and vacuum degree are adjusted in the same way as the adjustment method mentioned above, and the coating process parameters are adjusted according to the degree and uniformity of the surface contact angle and the product performance yield. After the process parameters of the small batch products are adjusted, the production capacity is gradually enlarged and the process parameters of the treatment are repeatedly adjusted using the same method, thereby effectively reducing the product loss caused by the adjustment.

[0093] In an embodiment of the present invention, at least one microfluidic chip is placed on a placement table in a vacuum chamber; a vacuum generation system is turned on to extract the gas in the vacuum chamber until a preset vacuum range is reached; a process gas is introduced; a voltage is applied to an electrode plate in the vacuum chamber by a plasma generator to ionize the process gas into plasma so as to deposit a polymer film on the inner and outer surfaces of the microfluidic chip; when the coating time reaches a preset deposition time, the vacuum chamber is broken to obtain a target microfluidic chip after surface hydrophobic treatment. Thus, under the premise of adjusting the parameters of the plasma treatment, the same surface modification method can be used for a variety of different substrates, and the inside and outside of the chip are simultaneously hydrophobically modified, effectively maintaining the consistency of the hydrophobic surface modification layer.

[0094] See also Figure 2 , Figure 2 A schematic structural diagram of a microfluidic chip surface hydrophobic treatment device in an embodiment of the present invention is shown.

[0095] The embodiment of the present invention provides a microfluidic chip surface hydrophobic treatment device, comprising a control system 1, a vacuum generating system 2, a vacuum chamber 3, a plasma generator 4 and a gas cylinder 5;

[0096] Gas cylinder 5 is loaded with process gas;

[0097] The vacuum chamber 3 is connected to the vacuum generating system 2 and the gas cylinder 5 through pipelines, and the vacuum chamber 3 is provided with an exhaust valve 52;

[0098] The control system 1 is electrically connected to the plasma generator 4 and the gas cylinder 5 respectively, and is used to control the plasma generator 4 and the input of the process gas;

[0099] The plasma generator 4 is electrically connected to the electrode plate 32 in the vacuum chamber 3 to provide a high-frequency voltage.

[0100] In an embodiment of the present invention, the vacuum chamber 3 can be fixed in a cabinet frame, and the left and right sides are removable doors, through which the user can place the microfluidic chip into or take it out of the vacuum chamber 3. The vacuum generating system 2 is composed of a bellows, a KF connector, a vacuum pump and an oil mist filter, and the core component is a vacuum pump or a vacuum pump group. Among them, the gas cylinder 5 can be loaded with process gas or volatile liquid. It is connected to the vacuum chamber 3 through a pipeline of the gas cylinder 5.

[0101] After the microfluidic chip is placed on the placement table 31 of the vacuum chamber 3, if the control system 1 receives the instruction information, the vacuum generation system 2 is started to extract the gas in the vacuum chamber 3 until the set vacuum degree, such as 20Pa, is reached, and an instruction is issued with a preset flow value to open the air inlet valve 51 between the gas cylinder 5 and the vacuum chamber 3 to connect the gas cylinder 5 and the vacuum chamber 3, so that the process gas enters the vacuum chamber 3; the plasma generator 4 is started with a preset output power, so that it uses high-frequency conversion technology to form a high-frequency voltage and apply it to the electrode plate 32, so as to ionize the process gas in the vacuum chamber 3 and generate plasma; the plasma is deposited on the inner and outer surfaces of the microfluidic chip on the placement table 31 to form a polymer film; until the coating time reaches the preset deposition time, an instruction is issued to start the exhaust valve 52 to break the vacuum chamber, and after cooling to room temperature, the vacuum chamber 3 is opened to take out the microfluidic chip.

[0102] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for hydrophobic treatment of the surface of a microfluidic chip, characterized in that: include: Placing at least one microfluidic chip on a placement table in the vacuum chamber; Turning on the vacuum generating system to extract the gas in the vacuum chamber until the preset vacuum degree range is reached; Introducing process gas; Applying voltage to the electrode plate in the vacuum chamber through a plasma generator to ionize the process gas into plasma so as to deposit a polymer film on the inner and outer surfaces of the microfluidic chip; When the coating time reaches the preset deposition time, the vacuum chamber is broken to obtain a target microfluidic chip after the surface hydrophobic treatment.

2. The method according to claim 1, characterized in that The method further comprises: Measuring the surface contact angle of the target microfluidic chip at multiple points; If all the surface contact angles are not within the expected contact angle range, adjusting the output power of the plasma generator according to a preset power gradient until any of the surface contact angles is within the expected contact angle range; The coating time is adjusted according to a preset time gradient until all the surface contact angles are within the expected contact angle range.

3. The method according to claim 2, characterized in that The method further comprises: If all the surface contact angles are not within the expected contact angle range and the output power has been adjusted, then measuring the surface contact angles of the target microfluidic chip after the process gas is introduced at multiple preset flow rates to determine the flow adjustment direction; Adjusting the flow rate of the process gas according to the flow rate adjustment direction and the preset flow rate gradient until the surface contact angle reaches a peak value; Jump to the step of adjusting the output power of the plasma generator according to the preset power gradient.

4. The method according to claim 2 or 3, characterized in that: The method further comprises: If the coating time has been adjusted to the maximum time and any of the surface contact angles is not within the expected contact angle range, the vacuum generating system is driven to increase the vacuum degree in the vacuum chamber according to a preset vacuum gradient until all the surface contact angles are within the expected contact angle range.

5. The method according to claim 1, characterized in that The process gas is a fluorinated olefin gas or a volatile gas of hexamethyldisiloxane.

6. The method according to claim 1, characterized in that The flow rate range of the process gas is 0 SCCM-300 SCCM.

7. The method according to claim 1, characterized in that The vacuum degree ranges from 20Pa to 100Pa.

8. The method according to claim 1, characterized in that The output power range of the plasma generator is 0W-1000W.

9. The method according to claim 1, characterized in that: The method further comprises: If the material of the microfluidic chip is a thermoplastic polymer, the maximum temperature in the vacuum chamber is maintained at less than 70°C.

10. A microfluidic chip surface hydrophobic treatment device, characterized in that: It includes a control system, a vacuum generating system, a vacuum chamber, a plasma generator and a gas cylinder; The gas cylinder is loaded with process gas; The vacuum chamber is connected to the vacuum generating system and the gas cylinder through pipelines, and the vacuum chamber is provided with an exhaust valve; The control system is electrically connected to the plasma generator and the gas cylinder, respectively, and is used to control the plasma generator and the input of the process gas; The plasma generator is electrically connected to the electrode plate in the vacuum chamber to provide a high-frequency voltage.

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