Thin film, digital microfluidic chip substrate and method for manufacturing same

Abstract

A thin film, a digital microfluidic chip substrate, and a method for manufacturing the same. The thin film (3) is a dielectric and hydrophobic thin film, with one surface being hydrophilic and the other being hydrophobic. Because the thin film (3) has both dielectric and hydrophobic properties, it fundamentally overcomes the irreversible damage to conventional digital microfluidic chips caused by the hydrophobic layer peeling off the dielectric layer, and greatly simplifies the manufacturing process for the dielectric and hydrophobic layers. Meanwhile, the dielectric and hydrophobic thin film has a hydrophilic surface, which, after combining with an adhesive (2), allows the thin film to be firmly attached to the upper surface of a circuit board (1). The thin film is resistant to high temperatures and does not easily peel off from the circuit board (1), thereby expanding the use scenarios of the chip and extending its lifespan.

Description

[Technical Field]

[0001] This application claims priority to Chinese Patent Application No. CN202210969277.X, filed on August 12, 2022, the contents of which are considered part of this application and are incorporated herein in their entirety.

[0002] The present application relates to the technical field of digital microfluidic chips, and in particular to thin films, digital microfluidic chip substrates, and methods for manufacturing the same. [Background technology]

[0003] Digital microfluidic chips are based on electrowetting technology, which uses electrical potentials to adjust the surface energies of solids and liquids, generating tangential thrust forces due to the asymmetry of the droplet's contact angle, resulting in asymmetric deformation at both ends of the droplet and promoting pressure differences within the droplet, thereby achieving precise manipulation of microdroplets. The basic structure of a digital microfluidic chip includes a circuit board and dielectric and hydrophobic layers disposed on the circuit board, which together form the chip substrate. The dielectric and hydrophobic layers on the circuit board are the most essential components of a digital microfluidic chip, and their dielectric and hydrophobic properties are essential for liquid manipulation.

[0004] Currently, the most important technology for manufacturing digital microfluidic chip substrates involves first forming a dielectric layer material on a printed circuit board (PCB)-based circuit substrate through a coating process, and then forming a hydrophobic layer on the dielectric layer through processes such as spin coating or spray coating. The conventional manufacturing process is complicated, the thickness of the dielectric film material suitable for the coating process is too large to provide sufficient driving force for the liquid, and the manufacturing of the hydrophobic layer requires high equipment and environmental cleanliness, resulting in high economic costs. Furthermore, the hydrophobic layer easily peels off from the dielectric film, causing irreversible damage to the digital microfluidic chip. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the inventors, after long-term research and continuous efforts, have provided a thin film, a digital microfluidic chip substrate, and a manufacturing method thereof. The thin film of the present application realizes the dual functions of a dielectric layer and a hydrophobic layer, which fundamentally solves the problem of the hydrophobic layer easily peeling off from the dielectric layer. In addition, the dielectric and hydrophobic thin film of the present application has a hydrophilic surface that helps it bond with adhesives, allowing the thin film to be firmly attached to the upper surface of a circuit board. The thin film has the effects of being resistant to high temperatures and not easily peeling off from the circuit board, which expands the use scenarios of the chip and extends the life of the chip.

[0006] In a first aspect, the present application provides a thin film having dielectric and hydrophobic properties, wherein one surface of the thin film having dielectric and hydrophobic properties is a hydrophilic surface and the other surface is a hydrophobic surface.

[0007] In a second aspect, the present application provides a digital microfluidic chip substrate comprising a circuit board, an adhesive, and a thin film according to the present application.

[0008] In a third aspect, the present application provides a method for producing a thin film according to the present application, the method comprising subjecting the thin film to a surface modification treatment. In a fourth aspect, the present application provides a method for manufacturing a digital microfluidic chip substrate according to the present application, comprising: (1) applying an adhesive to a surface of a circuit board; (2) covering the surface of the adhesive with a thin film of hydrophilic surface; The present invention provides a method comprising:

[0009] In a fifth aspect, the present application provides the use of a thin film according to the present application as a substitute for a dielectric layer and a hydrophobic layer in the manufacture of a digital microfluidic chip.

[0010] In a sixth aspect, the present application provides a digital microfluidic chip comprising a thin film according to the present application or a digital microfluidic chip substrate according to the present application.

[0011] In a seventh aspect, the present application provides a digital microfluidic system comprising a thin film according to the present application, or a digital microfluidic chip substrate according to the present application, or a digital microfluidic chip according to the present application.

[0012] Compared with the prior art, the present application has the following beneficial effects:

[0013] The thin film of the present application has the dual functions of both a dielectric layer and a hydrophobic layer, fundamentally solving the problem of irreversible damage to digital microfluidic chips caused by the hydrophobic layer easily peeling off from the dielectric layer, while also greatly simplifying the manufacturing process, reducing production costs, and improving production efficiency. In addition, compared with the thickness of conventional dielectric layers, the thin film of the present application is thinner, which not only provides a greater driving force but also eliminates the problem of susceptibility to breakdown at high voltages due to its smaller thickness. Furthermore, the thin film of the present application also has a hydrophilic surface, which, after bonding with an adhesive, can be firmly attached to the upper surface of a circuit board. The thin film has the effects of being resistant to high temperatures up to 100°C and not easily peeling off from the circuit board, greatly expanding the use scenarios of the chip and extending its lifespan. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of the fabrication of a digital microfluidic chip substrate according to the present application, where 1—circuit board, 2—adhesive, and 3—thin film.

[0015] Detailed Description of the Embodiments Unless otherwise specified, all numerical values ​​expressing content, concentration, ratio, mass, percentage, technical effect, and the like used in the specification and claims should be understood to be modified in all instances by the term "approximately" or "about." Accordingly, unless otherwise indicated, the numerical parameters set forth in the following description and appended claims are approximations. Unless otherwise specified, terms used herein have the meanings commonly understood by one of ordinary skill in the art. For those skilled in the art, each numerical parameter may vary depending on the desired properties and effects sought to be obtained by the present application and should be interpreted in light of the number of significant digits and conventional rounding techniques, or as understood by one of ordinary skill in the art.

[0016] In this application, broad ranges of values ​​and parameters are described as approximations, but the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in its respective testing measurements. Every numerical range given throughout this specification includes every narrower numerical range that falls within such broader numerical range, as if such narrower numerical ranges were all expressly written herein.

[0017] Unless otherwise specified, the orientations or positions indicated by terms used in this specification and claims, such as "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," are based on the orientations or positions shown in the drawings and are intended solely to facilitate and simplify the description of this application. They do not indicate or imply that the referenced devices or elements must have a particular orientation or be configured and operated in a particular orientation, and therefore cannot be construed as limiting this application. In addition, terms such as "first," "second," and the like are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or the number of technical features depicted. Thus, a feature defined as "first," "second," and the like may explicitly or implicitly include one or more features. In this specification, unless otherwise specified, "plurality" means two or more.

[0018] In this application, the term "contact angle" refers to the angle at the point where the three phases of solid, liquid, and vapor meet, starting from the solid-liquid interface, passing through the interior of the liquid, and ending at the gas-liquid interface. This is an important parameter for characterizing the wettability of a material's surface. A contact angle equal to 0 indicates complete wettability, a contact angle less than 90° indicates partial wettability, a contact angle equal to 90° is the boundary between "wetting" and "non-wetting," a contact angle greater than 90° indicates non-wetting, and a contact angle equal to 180° indicates complete non-wetting. The contact angles of thin films in this application are measured with a contact angle measurement device using image analysis.

[0019] In this application, the expression "sliding angle" refers to the critical angle formed between an inclined surface and a horizontal plane before a droplet begins to roll off the inclined surface. The sliding angle is an important parameter that characterizes the wettability of a material surface. The sliding angle of the thin film in this application is measured by a sliding angle measurement device using an image analysis method.

[0020] In a first aspect of the present application, there is provided a thin film having dielectric and hydrophobic properties, one surface of which is a hydrophilic surface and the other surface is a hydrophobic surface.

[0021] In some embodiments of the present application, the thin film is a monolayer film.

[0022] The thin film provided by the present application realizes the dual functions of a dielectric layer and a hydrophobic layer in conventional processes, thereby fundamentally solving the problem of irreversible damage to digital microfluidic chips caused by the hydrophobic layer easily peeling off from the dielectric layer. Furthermore, the thin film provided by the present application has stable performance, good chemical and biological compatibility, and good application prospects in the biochemistry field. In addition, the thin film provided by the present application has a hydrophilic surface. After bonding the hydrophilic surface with an adhesive, the thin film can be firmly attached to the upper surface of a circuit board, and the thin film will not easily peel off from the circuit board, greatly extending the life of the chip.

[0023] In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of <90°.

[0024] In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦80°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦70°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦60°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦50°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦40°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦30°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦20°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of ≦10°. In some embodiments of the present application, the hydrophilic surface of the thin film has a contact angle of 70°, 71°, 72°, 73°, 74°, or 75°.

[0025] In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of ≧30°.

[0026] In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of 30°, 31°, 32°, 34°, or 35°.

[0027] In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of ≧40°. In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of ≧50°. In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of ≧55°. In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of ≧60°. In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of ≧65°. In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of ≧70°.

[0028] In some embodiments of the present application, the dielectric and hydrophobic thin film is a Teflon thin film.

[0029] In some embodiments of the present application, the film is an amorphous fluoropolymer film (AF), a fluorinated ethylene propylene film (FEP), a fluoropolymer foam film (FFR), a fluoropolymer film (NXT), or a perfluoroalkoxy film (PFA).

[0030] In some embodiments of the present application, the film is a fluorinated ethylene propylene film (FEP) or a perfluoroalkoxy film (PFA).

[0031] In some embodiments of the present application, the film is a fluorinated ethylene propylene film (FEP). In some embodiments of the present application, the film is a perfluoroalkoxy film (PFA).

[0032] In some embodiments of the present application, the thin film has a thickness of 5 to 200 μm.

[0033] In some embodiments of the present application, the thin film has a thickness of 5 to 150 μm.

[0034] In some embodiments of the present application, the thin film has a thickness of 10 to 100 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 90 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 80 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 70 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 60 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 50 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 40 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 30 μm. In some embodiments of the present application, the thin film has a thickness of 10 μm, 12 μm, 12.5 μm, 15 μm, 20 μm, 25 μm, or 30 μm. In some embodiments of the present application, the thin film has a thickness of 10 to 20 μm. In some embodiments of the present application, the thin film has a thickness of 12 to 18 μm. In some embodiments of the present application, the thin film has a thickness of 12 to 16 μm. In some embodiments of the present application, the thin film has a thickness of 12 to 14 μm. In some embodiments of the present application, the thin film has a thickness of 12 μm, 12.5 μm, 13 μm, 13.5 μm, or 14 μm.

[0035] In some embodiments of the present application, the thin film has a thickness of 12.5 to 25 μm.

[0036] In some embodiments of the present application, the thin film has a thickness of 12.5 μm or 25 μm.

[0037] In order to provide a sufficient driving force to the liquid, it is necessary to reduce the thickness of the dielectric layer and the hydrophobic layer. However, in the conventional manufacturing process of the dielectric layer, the thickness of the dielectric material cannot be made too thin to be suitable for the coating process, and on the other hand, a dielectric layer that is too thin is prone to breakdown under high voltage, causing damage to the chip. The thin film of the present application is much thinner than the dielectric layer manufactured by the conventional process, so it can not only provide a sufficient driving force to the liquid, but also has a higher breakdown voltage and is less prone to breakdown.

[0038] In a second aspect of the present application, there is provided a digital microfluidic chip substrate comprising a circuit board, an adhesive, and a thin film according to the present application.

[0039] In some embodiments of the present application, referring to FIG. 1, a chip substrate comprises a circuit board 1 , an adhesive 2 , and a thin film 3 .

[0040] In some embodiments of the present application, the material of the circuit board is not particularly limited, and any circuit board commonly used in the art can be used. In some embodiments of the present application, the circuit board is a copper clad board, a ceramic substrate, or an aluminum substrate.

[0041] In some embodiments of the present application, the circuit board and the membrane are bonded by an adhesive, the adhesive bonding to the hydrophilic surface of the membrane.

[0042] In some embodiments of the present application, the top surface of the circuit board is covered with an adhesive, the other surface of which is bonded to the hydrophilic surface of the thin film.

[0043] In some embodiments of the present application, the adhesive comprises one or more of polyacrylic acid, polyurethane, epoxy resin, polyimide, polystyrene, polyacrylate, or ethylene-vinyl acetate copolymer. In some embodiments of the present application, the adhesive is one or more of polyacrylic acid, polyurethane, or epoxy resin.

[0044] In some embodiments of the present application, the adhesive has a thickness of 1 to 50 μm. In some embodiments of the present application, the adhesive has a thickness of 5 to 40 μm. In some embodiments of the present application, the adhesive has a thickness of 5 to 30 μm. In some embodiments of the present application, the adhesive has a thickness of 5 to 25 μm. In some embodiments of the present application, the adhesive has a thickness of 5 to 20 μm. In some embodiments of the present application, the adhesive has a thickness of 5 to 15 μm. In some embodiments of the present application, the adhesive has a thickness of 5 to 10 μm.

[0045] In a third aspect of the present application, there is provided a method for producing a thin film according to the present application, the method comprising the step of subjecting the thin film to a surface modification treatment.

[0046] In some embodiments of the present application, the thin film is subjected to a surface modification treatment to obtain a hydrophilic surface with a contact angle of <90°.

[0047] In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦80°. In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦70°. In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦60°. In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦50°. In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦40°. In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦30°. In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦20°. In some embodiments of the present application, the hydrophilic surface has a contact angle of ≦10°. In some embodiments of the present application, the hydrophilic surface has a contact angle of 70°, 71°, 72°, 73°, 74°, or 75°.

[0048] In some embodiments of the present application, the thin film is subjected to a surface modification treatment to obtain a hydrophilic surface with a sliding angle of ≧30°.

[0049] In some embodiments of the present application, the hydrophilic surface of the thin film has a sliding angle of 30°, 31°, 32°, 34°, or 35°.

[0050] In some embodiments of the present application, the hydrophilic surface has a sliding angle of ≧40°, in some embodiments of the present application, the hydrophilic surface has a sliding angle of ≧50°. In some embodiments of the present application, the hydrophilic surface has a sliding angle of ≧55°. In some embodiments of the present application, the hydrophilic surface has a sliding angle of ≧60°. In some embodiments of the present application, the hydrophilic surface has a sliding angle of ≧65°. In some embodiments of the present application, the hydrophilic surface has a sliding angle of ≧70°.

[0051] In some embodiments of the present application, the surface modification treatment is a corona treatment, a plasma treatment, a chemical treatment, a surface grafting treatment, or a photochemical modification treatment.

[0052] In some embodiments of the present application, the surface modification treatment is a corona treatment, a plasma treatment, or a chemical treatment.

[0053] In some embodiments of the present application, the surface modification treatment is a corona treatment. The corona treatment described in the present application is an electric shock treatment, which specifically involves using a corona treatment machine to perform corona discharge at high frequency and high voltage on the surface of the thin film, generating low-temperature plasma and improving the adhesion of the surface of the thin film.

[0054] In some embodiments of the present application, the plasma treatment is a low-temperature plasma treatment, which specifically involves adding sufficient energy to a gas to ionize the gas into a plasma state, and then treating the surface of the thin film with the low-temperature plasma.

[0055] In some embodiments of the present application, the chemical treatment may be a chemical oxidation treatment, which specifically involves treating the thin film with an oxidizing agent before use.

[0056] In some embodiments of the present application, the surface grafting may include forming hydrophilic groups on the surface of the thin film. In some embodiments of the present application, the surface grafting may include grafting hydrophilic molecules on the surface of the thin film. In a fourth aspect of the present application, there is provided a method for manufacturing a digital microfluidic chip substrate according to the present application, comprising: (1) applying an adhesive to a surface of a circuit board; (2) covering the surface of the adhesive with a thin film of hydrophilic surface; The present invention provides a method comprising:

[0057] In some embodiments of the present application, the method further comprises covering the hydrophobic surface of the thin film with a protective film in step (2). In some embodiments of the present application, the method comprises: (3) processing the thin film on the surface of the circuit board in step (2) to obtain a desired shape; (4) removing the protective film to obtain a digital microfluidic chip substrate; Further includes:

[0058] In some embodiments of the present application, the method further includes, in step (1), first cleaning the surface of the circuit board, and then applying an adhesive to the surface of the circuit board.

[0059] In some embodiments of the present application, the solvent for cleaning the surface of the circuit board is not particularly limited as long as there is no residue on the surface of the circuit board after cleaning. In some embodiments of the present application, the cleaning solvent includes one or more of isopropanol, ethanol, dimethylformamide, methylpyrrolidone, or dipropylene glycol dimethyl ether.

[0060] In some embodiments of the present application, in step (1), the coating process is a screen printing process. In some embodiments of the present application, in step (1), the coating process can also include first spot-applying adhesive to the surface of the circuit board, and then uniformly coating the adhesive on the surface of the circuit board by rolling.

[0061] In some embodiments of the present application, in step (2), the hydrophobic surface of the thin film is first covered with a protective film, and then the surface of the adhesive is covered with the hydrophilic surface of the thin film. In some embodiments of the present application, in step (2), the surface of the adhesive is first covered with the hydrophilic surface of the thin film, and then the hydrophobic surface of the thin film is covered with a protective film.

[0062] In some embodiments of the present application, the protective film is not particularly limited as long as it can provide the thin film with sufficient support to facilitate subsequent manipulation of the thin film. In some embodiments of the present application, the protective film includes one or more of a polyethylene terephthalate film (PET film) or a polyvinyl chloride film (PVC film). In some embodiments of the present application, the protective film is a PET film.

[0063] In some embodiments of the present application, the order of steps (2) and (3) may be reversed. In some embodiments of the present application, the hydrophobic surface of the thin film may be covered with a protective film, the thin film covered with the protective film may then be processed to obtain a thin film having a target shape, and finally, the hydrophilic surface of the thin film having the target shape may be covered on the surface of the adhesive.

[0064] In some embodiments of the present application, the processing method in step (3) is a method commonly used in the art for processing a thin film to obtain a target shape, and in some embodiments of the present application, the processing method in step (3) is a laser engraving method, a blanking method, or a punching method.

[0065] In some embodiments of the present application, in step (4), the protective film is removed after the adhesive has been cured. In some embodiments of the present application, the curing time of the adhesive is 5 to 60 seconds. In some embodiments of the present application, the curing time of the adhesive is 10 to 50 seconds. In some embodiments of the present application, the curing time of the adhesive is 10 to 40 seconds. In some embodiments of the present application, the curing time of the adhesive is 10 to 30 seconds. In some embodiments of the present application, the curing time of the adhesive is 10 to 20 seconds. In some embodiments of the present application, the curing time of the adhesive is 15 seconds.

[0066] In a fifth aspect of the present application, there is provided the use of a thin film according to the present application as a substitute for a dielectric layer and a hydrophobic layer in the manufacture of a digital microfluidic chip.

[0067] In a sixth aspect of the present application, there is provided a digital microfluidic chip comprising a thin film according to the present application or a digital microfluidic chip substrate according to the present application.

[0068] In some embodiments of the present application, the digital microfluidic chip may have a three-layer structure, specifically including an upper electrode plate, a lower electrode plate, and a cavity between the upper and lower electrode plates through which a test solution can move, the lower electrode plate including a circuit board, a microelectrode array, and a thin film according to the present application, and the filler between the upper and lower electrode plates may be air or silicone oil.

[0069] In some embodiments of the present application, the digital microfluidic chip employs a coplanar electrode design, in which there is no upper electrode plate structure, and both the positive and negative electrodes are disposed on the lower electrode plate, which comprises a circuit board, a microelectrode array, and a thin film according to the present application.

[0070] In a seventh aspect of the present application, there is provided a digital microfluidic system comprising a thin film according to the present application, or a digital microfluidic chip substrate according to the present application, or a digital microfluidic chip according to the present application.

[0071] In some embodiments of the present application, the digital microfluidic system may include, but is not limited to, a sample injection system, a nucleic acid extraction system, a detection system, a reaction system, and the like.

[0072] The various embodiments and preferences described above relating to the thin films, digital microfluidic chip substrates, and methods of manufacturing the same of the present application can be combined with each other (unless they are essentially contradictory to each other), and the various embodiments formed by such combinations are considered to be part of the present disclosure.

[0073] The technical solutions of the present application will be explained more clearly and distinctly in conjunction with examples as examples below. It should be understood that the examples are for illustrative purposes only and are not intended to limit the scope of protection of the present application. The scope of protection of the present application is limited only by the claims. [Example]

[0074] Unless otherwise specified, the materials and equipment used in the examples are conventional materials and equipment that are commercially available.

[0075] Example 1: Preparation of FEP thin film 1 (1) Feed the raw material FEP particles into a drying device (STOLZ, CLK100), set the drying temperature to 60°C, and set the drying cycle time to 4 hours. (2) After drying, the raw material was fed through a vacuum pipeline into the hopper of a blown film machine (Windmoller & Holscher, VAREX II), and then blown film molding was carried out under the conditions of a temperature of 260°C, a speed of 100 r / min, an air-cooled circular current of 4A, and a cooling water temperature of 5°C to obtain a 12.5 μm thick FEP thin film. (3) One surface of the 12.5 μm FEP thin film was subjected to corona treatment using a corona device (AcXys Technologies, ULD500) under conditions of 15,000 V, 25 kHz, and an electrode gap of 1 mm to obtain FEP thin film 1 having a hydrophilic surface; (4) The FEP thin film 1 was wound up using a winder for later use.

[0076] Example 2: Preparation of PFA thin film 2 (1) The raw material of PFA particles was fed into a drying device (STOLZ, CLK100), the drying temperature was set to 60°C, and the drying cycle time was set to 4 hours. (2) After drying, the raw material was fed through a vacuum pipeline into the hopper of a blown film machine (Windmoller & Holscher, VAREX II), and then blown film molding was carried out under the conditions of a temperature of 250°C, a speed of 100 r / min, an air-cooled circular current of 4A, and a cooling water temperature of 5°C to obtain a PFA thin film with a thickness of 12.5 μm. (3) After inflation molding, one surface of the 12.5 μm PFA thin film was subjected to corona treatment using a corona device (AcXys Technologies, ULD500) under conditions of 15,000 V, 25 kHz, and an electrode gap of 1 mm to obtain a PFA thin film 2 having a hydrophilic surface; (4) The PFA thin film 2 was wound up using a winder for later use.

[0077] Example 3: Preparation of FEP thin film 3 (1) Feed the raw material FEP particles into a drying device (STOLZ, CLK100), set the drying temperature to 60°C, and set the drying cycle time to 4 hours. (2) After drying, the raw material was fed through a vacuum pipeline into the hopper of a blown film machine (Windmoller & Holscher, VAREX II), and then blown film molding was carried out under the conditions of a temperature of 260°C, a speed of 50 r / min, an air-cooled circular current of 4A, and a cooling water temperature of 5°C to obtain a 25 μm-thick FEP thin film. (3) One surface of the 25 μm FEP thin film was subjected to corona treatment using a corona device (AcXys Technologies, ULD500) under conditions of 15,000 V, 25 kHz, and an electrode gap of 1 mm to obtain FEP thin film 3 having a hydrophilic surface; (4) The FEP thin film 3 was wound up using a winder for later use.

[0078] Example 4: Manufacturing of chip substrate 1 (1) Clean the surface of the circuit board with isopropanol. (2) The surface of the circuit board of step (2) is uniformly coated with adhesive by a screen printing process, the adhesive is polyacrylic acid, and the printing thickness is 5-10 μm; (3) Covering the hydrophobic surface of the FEP thin film 1 with a PET protective film; (4) The circuit board on which the adhesive of step (2) is printed is covered flat with the hydrophilic surface of the thin film of step (3) by rolling; (5) Place the product from step (4) under a UV light source for 15 seconds to cure the adhesive. (6) Exposing the FEP thin film 1 on the surface of the circuit board to a laser to engrave a target shape; (7) The PET protective film on the hydrophobic surface of the FEP thin film 1 was removed, and thus the chip substrate 1 was obtained.

[0079] Example 5: Manufacture of chip substrate 2 The chip substrate 2 was produced by the same method as in Example 4, except that the FEP thin film 1 in step (3) was replaced with the PFA thin film 2.

[0080] Example 6: Manufacture of chip substrate 3 Chip substrate 3 was produced by the same method as in Example 4, except that FEP thin film 1 was replaced with FEP thin film 3 in step (3).

[0081] Comparative Example 1 (1) A 25 μm thick KAPTON adhesive tape is attached to the surface of the chip substrate as a dielectric layer. (2) Spray CYTOP evenly onto the top surface of the Kapton adhesive tape. (3) The chip substrate is placed on a heating table and the temperature is set to 90°C to vitrify the cytop. (4) cooling the chip substrate and solidifying the Cytop to form a hydrophobic layer, thus obtaining a conventional chip substrate having a dielectric layer and a hydrophobic layer; (5) The chip substrate of step (4) was fabricated into a chip, which was then subjected to a continuous pure water transfer test. Ten chips were tested, and after 30 minutes of continuous pure water transfer, partial detachment of the hydrophobic layer from the dielectric layer occurred in three chips. Meanwhile, ten chips fabricated from chip substrate 1 with a hydrophilic FEP thin film of Example 4 were subjected to the continuous pure water transfer test. After 30 minutes of continuous pure water transfer, none of the ten chips showed partial detachment. The specific procedure for the continuous pure water transfer test was as follows: Silicone oil was filled into the cavity of the chip, and then a 10 μL droplet of pure water was injected. The electrodes were controlled and started sequentially, allowing the droplet to move back and forth within the cavity of the chip for 30 minutes.

[0082] Comparative Example 2 The chip substrate of Comparative Example 2 was produced by the same method as in Example 4, except that FEP thin film 1 in step (3) was replaced with a 12.5 μm FEP thin film that had not been subjected to hydrophilic treatment.

[0083] Comparative Example 3 The chip substrate of Comparative Example 3 was produced by the same method as in Example 4, except that the FEP thin film 1 in step (3) was replaced with a 12.5 μm PFA thin film that had not been subjected to hydrophilic treatment.

[0084] Performance Test 1. Parameter measurement of thin film contact angle The contact angles of the thin films were measured using a contact angle measuring instrument (SINDIN, SDC-350) to characterize the hydrophilicity of the hydrophilic surface and the hydrophobicity of the hydrophobic surface of the thin films. Sixty thin films were tested, and the test procedures were as follows: (1) Place the thin film on the test stand. (2) Turn on the measuring device, drop 10 μm of pure water at the measurement position, and start the test. (3) The measurement software was automatically executed and the contact angle value was output.

[0085] 2. Measurement of the dielectric constant of thin films The dielectric constant of the thin film was measured by the three-terminal method using an impedance measuring instrument (Wayne Kerr, WK6500B), and the measurement procedure was as follows. (1) The thin film sample is attached to the measuring device using a test jig for attaching dielectric materials. (2) Fix the two electrodes of the measuring device to the test jig and start the measurement. (3) The dielectric constant of the thin film was calculated by the software program of the impedance measuring instrument.

[0086] 3. Measurement of breakdown voltage of thin films The breakdown voltage of the thin film was measured using a voltage breakdown tester (Ainuo Instrument Co., Ltd., AN96), and the test procedure was as follows: (1) Turn on the voltage breakdown tester and let it preheat for 15 minutes. (2) Open the door of the device, place the thin film sample between the two electrodes, and close the door. (3) Set the parameters in the tester software and start the test. (4) The voltage curve and breakdown voltage value were output by the instrument's software program.

[0087] 4. Measuring gas permeability of thin films The gas permeability of the thin films was measured using a gas permeability tester (Labthink, VAC-V2) based on the differential pressure method. (1) Cut out a thin film sample and measure its thickness. (2) Coat the test bench with vacuum grease. If there is grease on the disc in the cavity, wipe it off carefully. If there is grease on the edge of the filter paper, replace it (filter paper for chemical analysis, thickness 0.2-0.3 mm). (3) Close the needle valve of the gas permeable chamber and turn on the vacuum pump. (4) Place the filter paper on the disc of the test bench, then place the conditioned sample on it. The sample should be kept flat and wrinkle-free. Lightly press the sample to ensure good contact with the vacuum grease on the test bench. Open the needle valve of the low-pressure chamber, and the sample should be tightly attached to the filter paper under vacuum. Insert the O-ring into the groove of the top cover, then place the top cover on and tighten it. (5) Open the needle valve and block valve of the high-pressure chamber, start evacuation until the pressure is 27 Pa or less, and then continue degassing for 3 hours or more to remove gas and water vapor adsorbed on the sample. (6) Close the block valve, open the test gas cylinder, turn on the gas source switch, fill the high-pressure chamber with the test gas, and set the gas pressure in the high-pressure chamber to (1.0-1.1) x 10 5 Pa range, and if the pressure is too high, open the block valve to release the pressure. (7) Turn on the power switch of the host and computer, and input the name and thickness of the sample on the test bench, the volume parameter of the low-pressure chamber, and the name of the test gas using the keyboard, respectively, to prepare for the test; (8) Close the exhaust needle valves of the high-pressure chamber and the low-pressure chamber to start the gas permeability test. (9) In order to eliminate the nonlinear phase at the beginning of the test, a preliminary gas permeability test should be carried out for 10 minutes, and then the formal gas permeability test should be started, and the pressure change value ΔP of the low-pressure chamber and the test time t should be recorded; (10) The test was continued until the change in pressure difference became constant at the same time interval and stable permeability was achieved. The differential pressure values ​​for at least three consecutive time intervals were obtained and their arithmetic averages were calculated to calculate the gas permeability and gas permeability of the sample.

[0088] 5. Temperature Stability Measurement of Thin Films The temperature stability of the thin films was tested using a thin film heat shrinkage tester (Saicheng Instrument, RSY-01). (1) Cut out a thin film sample measuring 15 mm x 130 mm, and drill holes at both ends of the sample with a hole spacing of 100 mm and a hole diameter of 5 mm. (2) The sample is held through the jigs at both ends of the tester to ensure the sample is flat. (3) Turn on the tester, set the temperature to 100°C, and start heating. (4) The shrinkage rate of the thin film at 100°C was output by a tester, and a value of less than 0.8% was considered to be within the acceptable range.

[0089] 6. Chip substrate adhesion test The chip substrate adhesion was measured using a HANDPI general purpose tensile tester. (1) Peel off the thin film from the short side of the coated chip substrate while ensuring that the thin film is perpendicular to the chip substrate, then attach the thin film to the tester jig and tighten the screws to secure the thin film. (2) Lower the tester until the chip substrate touches the test stand. (3) Fix the chip substrate to the test stand using a jig; (4) The tester was turned on, and the output tensile peak value was taken as the adhesive strength of the chip substrate.

[0090] 7. Measurement of the sliding angle of thin films The sliding angle of the thin film was measured using a sliding angle measuring instrument (SINDIN, SDC-350) to characterize the hydrophilicity of the hydrophilic surface and the hydrophobicity of the hydrophobic surface of the thin film. Sixty thin films were tested, and the test procedure was as follows: (1) Place the film-coated chip substrate on the test table. (2) Turn on the measuring device, drop 10 μm of pure water at the measurement position, and start the test. (3) The measurement software was automatically run and the sliding angle value was output.

[0091] Experimental results and discussion

[0092] [Table 1]

[0093] [Table 2]

[0094] As can be seen from Tables 1 and 2, the thin films of Examples 1 to 3 have better dielectric constants, and their hydrophobic surfaces have larger contact angles, achieving the dual functions of a dielectric layer and a hydrophobic layer compared to conventional processes. In addition, the thin films of Examples 1 to 3 have higher breakdown voltages, better gas permeability, and better temperature stability, and are wrinkle-free even at high temperatures up to 100°C, making them widely applicable to a variety of environments.

[0095] As can be seen from Comparative Example 1, in conventional chips having a dielectric layer and a hydrophobic layer, the hydrophobic layer easily peels off from the dielectric layer, but no partial peeling is observed in chips manufactured using the thin film of the present application. Therefore, the thin film of the present application fundamentally solves the problem of irreversible damage to digital microfluidic chips caused by the easy peeling off of the hydrophobic layer from the dielectric layer. In addition, the manufacturing method of the chip substrate of the present application is simpler than the conventional complicated manufacturing process.

[0096] As can be seen from Table 1, the surface of the corona-treated thin film has a sliding angle of 30° to 35° and a contact angle of 70° to 75°, and is therefore hydrophilic. As can be seen from Examples 4 to 6 and Comparative Examples 2 and 3, the thin films after hydrophilic treatment in Examples 4 to 6 have stronger adhesion to the circuit board, can be firmly attached to the upper surface of the circuit board, and do not easily fall off the circuit board, even after being immersed in a solvent during use of the digital microfluidic chip, thereby extending the life of the chip.

Claims

1. A thin film having dielectric and hydrophobic properties, one surface of which is a hydrophilic surface and the other surface of which is a hydrophobic surface.

2. 10. The film of claim 1, wherein the hydrophilic surface of the film has a contact angle of <90[deg.].

3. 3. The membrane of claim 1 or 2, wherein the hydrophilic surface of the membrane has a sliding angle of ≥ 30°.

4. The thin film according to any one of claims 1 to 3, wherein the thin film having dielectric and hydrophobic properties is a Teflon thin film.

5. 5. The film of claim 4, which is an amorphous fluoropolymer film, a fluorinated ethylene propylene resin film, a fluoropolymer foam resin film, a fluoropolymer resin film, or a perfluoroalkoxy resin film.

6. 6. The thin film according to claim 4, which is a fluorinated ethylene propylene resin thin film or a perfluoroalkoxy resin thin film.

7. The thin film according to any one of claims 1 to 6, having a thickness of 5 to 200 µm.

8. The thin film according to claim 7, wherein the thickness of the thin film is 10 to 100 μm.

9. 9. The thin film of claim 8, wherein the thickness of the thin film is 12.5 to 25 μm.

10. 10. The film of claim 9, wherein the film has a thickness of 12.5 μm or 25 μm.

11. A digital microfluidic chip substrate comprising a circuit board, an adhesive, and the thin film according to any one of claims 1 to 10.

12. The digital microfluidic chip substrate of claim 11 , wherein the circuit board and the membrane are bonded by an adhesive, the adhesive being bonded to a hydrophilic surface of the membrane.

13. 13. The digital microfluidic chip substrate of claim 11 or 12, wherein the adhesive is one or more of polyacrylic acid, polyurethane, epoxy resin, polyimide, polystyrene, polyacrylate, or ethylene-vinyl acetate copolymer.

14. A method for manufacturing a thin film according to any one of claims 1 to 10, comprising the step of subjecting the thin film to a surface modification treatment.

15. 15. The method of claim 14, wherein the thin film is subjected to a surface modification treatment to obtain a hydrophilic surface with a contact angle of <90°.

16. 16. The method according to claim 14 or 15, wherein the thin film is subjected to a surface modification treatment to obtain a hydrophilic surface with a contact angle of ≥ 30°.

17. The method according to any one of claims 14 to 16, wherein the surface modification treatment is a corona treatment, a plasma treatment, a chemical treatment, a surface grafting treatment, or a photochemical modification treatment.

18. The method according to any one of claims 14 to 17, wherein the surface modification treatment is a corona treatment.

19. A method for manufacturing a digital microfluidic chip substrate according to any one of claims 11 to 13, comprising: (1) applying an adhesive to a surface of a circuit board; (2) covering the surface of the adhesive with a thin film of hydrophilic surface; A method comprising:

20. 20. The method of claim 19, further comprising the step of covering the hydrophobic surface of the thin film with a protective film in step (2).

21. (3) processing the thin film on the surface of the circuit board in step (2) to obtain a desired shape; (4) removing the protective film to obtain a digital microfluidic chip substrate; 21. The method of claim 19 or 20, further comprising:

22. Use of a thin film according to any one of claims 1 to 10 as a replacement for dielectric and hydrophobic layers in the manufacture of digital microfluidic chips.

23. A digital microfluidic chip comprising the thin film according to any one of claims 1 to 10 or the digital microfluidic chip substrate according to any one of claims 11 to 13.

24. A digital microfluidic system comprising the thin film according to any one of claims 1 to 10, or the digital microfluidic chip substrate according to any one of claims 11 to 13, or the digital microfluidic chip according to claim 23.

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