Thin film, digital microfluidic chip substrate, and method for manufacturing the 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 of Chinese Patent Application No. CN202210969277.X filed on August 12, 2022, the content of which is considered part of the present application and is incorporated herein in its entirety.

[0002] The present application belongs to the technical field of digital microfluidic chips, and particularly relates to a thin film, a digital microfluidic chip substrate, and a method for manufacturing the same.

Background Art

[0003] Digital microfluidic chips are based on electrowetting technology, which realizes precise manipulation of micro-droplets by adjusting the surface energy of solid and liquid through electric potential, generating tangential thrust through the asymmetry of the contact angle of the droplet, causing asymmetric deformation at both ends of the droplet, and promoting the pressure difference inside the droplet. The basic structure of a digital microfluidic chip includes a circuit board, a dielectric layer and a hydrophobic layer disposed on the circuit board, which together form a chip substrate. The dielectric layer and the hydrophobic layer on the circuit board are the most indispensable structures of the digital microfluidic chip, and their dielectric and hydrophobic properties are essential for liquid manipulation.

[0004] At present, the most important technology for manufacturing digital microfluidic chip substrates includes first forming a dielectric layer material by a coating process on a circuit board based on a printed circuit board (PCB), and then forming a hydrophobic layer on the dielectric layer by a process 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 liquid; the manufacturing of the hydrophobic layer requires high cleanliness of equipment and environment, leading to high economic cost; furthermore, the hydrophobic layer is easily detached from the dielectric film, causing irreversible damage to the digital microfluidic chip.

Summary of Invention

[0005] To overcome the shortcomings of prior art, the inventors, after long-term exploration and continuous attempts, provide a thin film, a digital microfluidic chip substrate, and a method for manufacturing the same. The thin film of this application achieves a dual function of a dielectric layer and a hydrophobic layer, which fundamentally solves the problem of the hydrophobic layer easily detaching from the dielectric layer. In addition, the dielectric and hydrophobic thin film of this application has a hydrophilic surface that aids in bonding with adhesives, so the thin film can be firmly attached to the upper surface of a circuit board, and the thin film has the effect of high temperature resistance and does not easily detach from the circuit board, thereby expanding the usage scenarios of the chip and extending the chip's lifespan.

[0006] In a first embodiment, the present application provides a dielectric and hydrophobic thin film in which one surface of the dielectric and hydrophobic thin film is a hydrophilic surface and the other surface is a hydrophobic surface.

[0007] In a second embodiment, 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 embodiment, the present application provides 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. In a fourth embodiment, the present application relates to a method for manufacturing a digital microfluidic chip substrate according to the present application, (1) The step of applying adhesive to the surface of the circuit board, (2) The step of covering the surface of the adhesive with a hydrophilic surface of a thin film. This provides a method that includes [something].

[0009] In a fifth embodiment, the application provides the use of a thin film according to the application as a substitute for dielectric layers and hydrophobic layers in the manufacture of digital microfluidic chips.

[0010] In a sixth embodiment, 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 embodiment, 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 to the prior art, this application has the following beneficial effects.

[0013] The thin film according to this application possesses the dual function of both a dielectric layer and a hydrophobic layer in conventional processes. This fundamentally solves the problem of irreversible damage to digital microfluidic chips caused by the easy detachment of the hydrophobic layer from the dielectric layer, while also significantly simplifying the manufacturing process, reducing production costs, and improving production efficiency. In addition, the thin film according to this application is thinner than the dielectric layer thickness of conventional films, which not only provides greater driving force but also avoids the problem of being easily destroyed by high voltage due to its thinner thickness. Furthermore, the thin film according to this application also has a hydrophilic surface, and after bonding the hydrophilic surface with an adhesive, the thin film can be firmly attached to the top surface of the circuit board. The thin film has the effect of resistance to high temperatures up to 100°C and does not easily detach from the circuit board, greatly expanding the range of chip usage scenarios and extending the chip's lifespan. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic diagram of the manufacturing process for a digital microfluidic chip substrate according to this application. Here, 1 is a circuit board, 2 is an adhesive, and 3 is a thin film.

[0015] [Detailed description of the embodiment] Unless otherwise specified, all numerical values ​​used in this specification and in the claims, such as content, concentration, ratio, mass, percentage, and technical effect, should be understood to be modified in all cases by the term "approximately" or "about." Accordingly, unless otherwise indicated, the numerical parameters described below and in the appended claims are approximate values. Unless otherwise specified, the terms used herein have meanings that are generally understood by those skilled in the art. To those skilled in the art, each numerical parameter may vary depending on the desired properties and effects to be obtained by this application and should be interpreted in light of significant figures and prior rounding techniques, or in a manner understood by those skilled in the art.

[0016] In this application, a wide range of numerical values ​​and parameters are described as approximations, but the numerical values ​​described in specific examples are shown as accurately as possible. However, all numerical values ​​inherently contain a certain degree of error, which inevitably arises from the standard deviation found in each test measurement. Each numerical range shown throughout this specification includes all narrower numerical ranges within such wider numerical ranges, as if all such narrower numerical ranges were explicitly stated herein.

[0017] Unless otherwise specified, the orientations or positional relationships indicated by terms used in this specification and the claims, such as “center,” “vertical,” “horizontal,” “top,” “bottom,” “front,” “back,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inside,” and “outside,” are based on the orientations or positional relationships shown in the drawings and are intended solely to facilitate and simplify the description of this application, and do not indicate or imply that the devices or elements mentioned must have a particular orientation, or must be configured and operated in a particular orientation, and therefore cannot be construed as limiting this application. In addition, terms such as “first,” “second,” etc., are used for illustrative purposes only and cannot be construed as indicating or implying relative importance, or as implicitly indicating the number of technical features shown. Thus, features defined by “first,” “second,” etc., may explicitly or implicitly include one or more features. In this specification, unless otherwise specified, “multiple” 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 at the solid-liquid interface, passing through the interior of the liquid, and ending at the gas-liquid interface. This is an important parameter that characterizes the wettability of the material 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 "wettable" and "unwettable," a contact angle greater than 90° indicates unwettable, and a contact angle equal to 180° indicates complete unwetability. The contact angle of the thin film in this application is measured using a contact angle measuring instrument that employs image analysis.

[0019] In this application, the term "slip angle" refers to the critical angle formed between an inclined surface and a horizontal plane before a droplet begins to roll down the inclined surface. The slip angle is an important parameter that characterizes the wettability of a material surface. The slip angle of the thin film in this application is measured using a slip angle measuring instrument that employs image analysis.

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

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

[0022] The thin film provided by the present application achieves 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 easy falling-off of the hydrophobic layer 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 biochemical field. In addition, the thin film provided by the present application has a hydrophilic surface; after the hydrophilic surface is bonded to an adhesive, the thin film can be firmly attached to the upper surface of a circuit board and does not easily fall off from the circuit board, thereby greatly extending the service 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 thin film is an amorphous fluoropolymer thin film (AF), a fluorinated ethylene propylene resin thin film (FEP), a fluoropolymer foam resin thin film (FFR), a fluoropolymer thin film (NXT), or a perfluoroalkoxy resin thin film (PFA).

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

[0031] In some embodiments of the present application, the thin film is a fluorinated ethylene propylene resin thin film (FEP). In some embodiments of the present application, the thin film is a perfluoroalkoxy resin thin 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 this application, the thin film has a thickness of 5 to 150 μm.

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

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

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

[0038] A second embodiment of this application provides a digital microfluidic chip substrate comprising a circuit board, an adhesive, and a thin film according to this application.

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

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

[0041] In some embodiments of this application, the circuit board and the thin film are bonded together by an adhesive, and the adhesive is bonded to the hydrophilic surface of the thin film.

[0042] In some embodiments of this application, the upper surface of the circuit board is covered with an adhesive, and the other surface of the adhesive is bonded to the hydrophilic surface of a thin film.

[0043] In some embodiments of this 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 this application, the adhesive is one or more of polyacrylic acid, polyurethane, or epoxy resin.

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

[0045] A third aspect of this application provides a method for producing a thin film according to this application, the method comprising the step of subjecting the thin film to a surface modification treatment.

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

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

[0048] In some embodiments of this application, a thin film is subjected to a surface modification treatment to obtain a hydrophilic surface having a sliding angle of ≥30°.

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

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

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

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

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

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

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

[0056] In some embodiments of this application, the surface grafting treatment may include forming hydrophilic groups on the surface of the thin film. In some embodiments of this application, the surface grafting treatment may include grafting hydrophilic molecules onto the surface of the thin film. A fourth embodiment of this application is a method for manufacturing a digital microfluidic chip substrate according to this application, (1) The step of applying adhesive to the surface of the circuit board, (2) The step of covering the surface of the adhesive with a hydrophilic surface of a thin film. This provides a method that includes [something].

[0057] In some embodiments of this application, the method further includes the step of covering the hydrophobic surface of the thin film with a protective film in step (2). In some embodiments of this application, the method is (3) Step (2) involves processing a thin film on the surface of the circuit board to obtain a desired shape, (4) The step of removing the protective film to obtain a digital microfluidic chip substrate It also includes.

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

[0059] In some embodiments of this 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 this application, the cleaning solvent includes one or more of isopropanol, ethanol, dimethylformamide, methylpyrrolidone, or dipropylene glycol dimethyl ether.

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

[0061] In some embodiments of this 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 this 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 this application, the protective film is not particularly limited insofar as it can provide sufficient support to the thin film to facilitate subsequent handling of the thin film. In some embodiments of this application, the protective film includes one or more of polyethylene terephthalate films (PET films) or polyvinyl chloride films (PVC films). In some embodiments of this application, the protective film is a PET film.

[0063] In some embodiments of this application, the order of steps (2) and (3) may be reversed. In some embodiments of this application, the hydrophobic surface of a thin film can be covered with a protective film, the thin film covered with the protective film can 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 can be used to cover the surface of the adhesive.

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

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

[0066] A fifth aspect of this application provides the use of a thin film according to this application as a substitute for dielectric layers and hydrophobic layers in the manufacture of digital microfluidic chips.

[0067] A sixth embodiment of this application provides a digital microfluidic chip comprising a thin film according to this application or a digital microfluidic chip substrate according to this application.

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

[0069] In some embodiments of this 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 placed on a lower electrode plate, the lower electrode plate comprising a circuit board, a microelectrode array, and a thin film according to this application.

[0070] A seventh embodiment of this application provides a digital microfluidic system comprising a thin film according to this application, a digital microfluidic chip substrate according to this application, or a digital microfluidic chip according to this application.

[0071] In some embodiments of this 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 for the thin films, digital microfluidic chip substrates, and methods for manufacturing the same can be combined with one another (inso that they are not inherently contradictory), and the various embodiments formed by such combinations are considered to be part of the disclosure.

[0073] The technical solutions of this application are described below more clearly and concisely, with illustrative examples. It should be understood that the examples are for illustrative purposes only and are not intended to limit the scope of protection of this application. The scope of protection of this application is limited solely by the claims. [Examples]

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

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

[0076] Example 2: Fabrication of PFA thin film 2 (1) The raw material for PFA particles is supplied to the drying apparatus (STOLZ, CLK100), the drying temperature is set to 60°C, and the drying cycle time is set to 4 hours. (2) After drying, the raw material is supplied through a vacuum pipeline to the hopper of an inflation film apparatus (Windmoller & Holscher, VAREX II), and then inflation molding is performed under conditions of a temperature of 250°C, a speed of 100 r / min, an air cooling current of 4 A, 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 is subjected to corona treatment using a corona apparatus (AcXys Technologies, ULD500) under the 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 winding machine for later use.

[0077] Example 3: Fabrication of FEP thin film 3 (1) The raw material for FEP particles is supplied to the drying apparatus (STOLZ, CLK100), the drying temperature is set to 60°C, and the drying cycle time is set to 4 hours. (2) After drying, the raw material is supplied through a vacuum pipeline to the hopper of an inflation film apparatus (Windmoller & Holscher, VAREX II), and then inflation molding is performed under conditions of a temperature of 260°C, a speed of 50 r / min, an air cooling current of 4 A, and a cooling water temperature of 5°C to obtain an FEP thin film with a thickness of 25 μm. (3) One surface of a 25 μm FEP thin film is subjected to corona treatment using a corona apparatus (AcXys Technologies, ULD500) under the conditions of 15,000 V, 25 kHz, and an electrode gap of 1 mm to obtain an FEP thin film 3 having a hydrophilic surface. (4) The FEP thin film 3 was wound up using a winding machine for later use.

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

[0079] Example 5: Manufacturing of Chip Substrate 2 Chip substrate 2 was manufactured using the same method as in Example 4, except that the FEP thin film 1 in step (3) was replaced with a PFA thin film 2.

[0080] Example 6: Manufacturing of Chip Substrate 3 Chip substrate 3 was manufactured using the same method as in Example 4, except that the FEP thin film 1 in step (3) was replaced with FEP thin film 3.

[0081] Comparative Example 1 (1) A 25 μm Kapton adhesive tape is attached to the surface of the chip substrate as a dielectric layer. (2) Spray CYTOP evenly onto the upper surface of the Kapton adhesive tape, (3) Place the chip substrate on the heating table and set the temperature to 90°C to vitrify the chip. (4) The chip substrate is cooled and the site top is solidified to form a hydrophobic layer, thereby obtaining a conventional chip substrate having a dielectric layer and a hydrophobic layer. (5) The chip substrate from step (4) was fabricated into chips, which were then subjected to a continuous pure water flow test. Ten chips were tested, and after 30 minutes of continuous pure water flow, partial detachment of the hydrophobic layer from the dielectric layer occurred in three chips. On the other hand, ten chips fabricated from chip substrate 1 having a hydrophilic surface FEP thin film according to Example 4 were subjected to a continuous pure water flow test, and after 30 minutes of continuous pure water flow, none of the ten chips showed partial detachment. The specific procedure for the continuous pure water flow test was as follows: Silicone oil was filled into the chip cavity, then one drop of 10 μL of pure water was injected, and the electrodes were controlled to start sequentially so that the droplet could move back and forth within the chip cavity for 30 minutes.

[0082] Comparative Example 2 The chip substrate of Comparative Example 2 was manufactured 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 FEP thin film without hydrophilization treatment.

[0083] Comparative Example 3 The chip substrate of Comparative Example 3 was manufactured 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 without hydrophilization treatment.

[0084] Performance testing 1. Measurement of the contact angle parameter of the thin film The contact angle of the thin films was 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 procedure was as follows. (1) Place the thin film on the test stand, (2) Turn on the power to the measuring instrument, drop 10 μm of pure water onto 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 a thin film The dielectric constant of the thin film was measured using the three-terminal method with an impedance measuring instrument (Wayne Kerr, WK6500B), and the measurement procedure was as follows. (1) The thin film sample is secured to the measuring instrument using a test fixture for securing dielectric material, (2) Fix the two electrodes of the measuring instrument to the test fixture and start the measurement. (3) The dielectric constant of the thin film was calculated using a software program for an impedance measuring instrument.

[0086] 3. Measurement of the 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 preheat for 15 minutes. (2) Open the door of the apparatus, place the thin film sample between the two electrodes, and close the door of the apparatus. (3) Set the parameters in the tester software and start the test. (4) The voltage curve and breakdown voltage values ​​were output by the equipment's software program.

[0087] 4. Measurement of gas permeability of thin films The gas permeability of the thin film was measured using a differential pressure method gas permeability tester (Labthink, VAC-V2). (1) Cut out a thin film sample and measure its thickness. (2) The test bench should be coated with vacuum grease, and any grease on the discs in the cavity should be carefully wiped off. If there is grease on the edges of the filter paper, the filter paper should be replaced (chemical analysis filter paper, 0.2-0.3 mm thick). (3) Close the needle valve of the gas permeable chamber and turn on the power to the vacuum pump. (4) Place the filter paper on the disc of the test bench, then place the prepared sample on top, keeping the sample wrinkle-free and flat, lightly press the sample so that it makes good contact with the vacuum grease of the test bench, open the needle valve of the low-pressure chamber, the sample should be tightly attached to the filter paper under vacuum, embed the O-ring in the groove of the top cover, place the top cover over and tighten it, (5) Open the needle valve and block valve of the high-pressure chamber, start vacuuming 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 to fill the high-pressure chamber with test gas, and set the gas pressure in the high-pressure chamber to (1.0~1.1) × 10 5 The pressure should be kept within the Pa range, and if it is too high, the block valve should be opened to release the pressure. (7) Turn on the power switches of the host and computer, enter 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, and complete the test preparation. (8) Close the exhaust needle valves of the high-pressure chamber and the low-pressure chamber and start the gas permeability test. (9) In order to eliminate the nonlinear phase at the start of the test, a preliminary gas permeability test should be performed for 10 minutes, after which the formal gas permeability test should be started, and the pressure change value ΔP in 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 over the same time interval and stable permeation was achieved. The differential pressure values ​​for at least three consecutive time intervals were obtained, and their arithmetic mean was calculated to determine the gas permeation rate and gas permeability of the sample.

[0088] 5. Measurement of the temperature stability of thin films The temperature stability of the thin film was tested using a thin film thermal shrinkage tester (Saicheng Instrument, RSY-01). (1) Cut out a thin film sample measuring 15 mm x 130 mm, and make holes at both ends of the sample with a spacing of 100 mm and a hole diameter of 5 mm. (2) Hold the sample by passing it through the jigs at both ends of the tester to ensure the flatness of the sample, (3) Turn on the power of 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 acceptable.

[0089] 6. Testing the adhesive strength of the chip substrate. The adhesive strength of the chip substrate is measured using a HANDPI general-purpose tensile tester. HP-500 Measured using [this method]. (1) Peel off the thin film from the coated chip substrate from the short side, ensuring the thin film is perpendicular to the chip substrate. Then, attach the thin film to the tester's jig and tighten the screw to secure the thin film. (2) Lower the tester until the chip substrate is in contact with the test stand. (3) Use a jig to fix the chip substrate to the test stand, (4) The tester was powered on, and the output tensile peak value was used as the adhesive strength of the chip substrate.

[0090] 7. Parameter measurement of the sliding angle of the thin film 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 coated chip substrate on the test stand. (2) Turn on the power to the measuring instrument, drop 10 μm of pure water onto the measurement position, and start the test. (3) The measurement software was executed automatically and the value of the slip angle 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 1-3 have a better dielectric constant, their hydrophobic surfaces have a larger contact angle, and they achieve the dual function of dielectric and hydrophobic layers in conventional processes. In addition, the thin films of Examples 1-3 have a higher breakdown voltage, better gas permeability, and better temperature stability, are wrinkle-free under high temperature conditions of 100°C, and are therefore widely applicable to various 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 detaches from the dielectric layer, but no partial detachment is observed in chips manufactured using the thin film of this application. Therefore, the thin film of this application fundamentally solves the problem of irreversible damage to digital microfluidic chips caused by the easy detachment of the hydrophobic layer from the dielectric layer. In addition, the manufacturing method of the chip substrate of this application is simpler compared to conventional complex manufacturing processes.

[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 to 3, the thin films after hydrophilization treatment in Examples 4 to 6 have higher adhesion to the circuit board, can be firmly attached to the upper surface of the circuit board, do not easily detach from the circuit board, and do not easily detach from the circuit board even after being immersed in a solvent during use of the digital microfluidic chip, thus extending the chip's lifespan.

Claims

1. A digital microfluidic chip substrate comprising a circuit board, an adhesive, and a thin film, The thin film has dielectric and hydrophobic properties, A digital microfluidic chip substrate in which one surface of the thin film is a hydrophilic surface made hydrophilic by a surface modification treatment, and the other surface is a hydrophobic surface.

2. The digital microfluidic chip substrate according to claim 1, wherein the hydrophilic surface of the thin film has a contact angle of <90°.

3. The digital microfluidic chip substrate according to claim 1, wherein the hydrophilic surface of the thin film has a sliding angle of ≥ 30°.

4. The digital microfluidic chip substrate according to claim 1, wherein the thin film is a Teflon thin film.

5. The digital microfluidic chip substrate according to claim 4, wherein the thin film is an amorphous fluoropolymer thin film, a fluorinated ethylene propylene resin thin film, a fluoropolymer foam resin thin film, a fluoropolymer resin thin film, or a perfluoroalkoxy resin thin film.

6. The digital microfluidic chip substrate according to claim 4, wherein the thin film is a fluorinated ethylene propylene resin thin film or a perfluoroalkoxy resin thin film.

7. The digital microfluidic chip substrate according to claim 1, wherein the thin film has a thickness of 5 to 200 μm.

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

9. The digital microfluidic chip substrate according to claim 8, wherein the thickness of the thin film is 12.5 to 25 μm.

10. The digital microfluidic chip substrate according to claim 9, wherein the thickness of the thin film is 12.5 μm or 25 μm.

11. The digital microfluidic chip substrate according to claim 1, wherein the circuit board and the thin film are bonded by the adhesive, and the adhesive is bonded to the hydrophilic surface of the thin film.

12. The digital microfluidic chip substrate according to claim 1, wherein the adhesive is one or more of polyacrylic acid, polyurethane, epoxy resin, polyimide, polystyrene, polyacrylate, or ethylene-vinyl acetate copolymer.

13. A method for manufacturing a digital microfluidic chip substrate according to any one of claims 1 to 12, comprising the step of subjecting a thin film to a surface modification treatment.

14. The method according to claim 13, wherein the thin film is subjected to the surface modification treatment to obtain the hydrophilic surface having a contact angle of <90°.

15. The method according to claim 13, wherein the thin film is subjected to the surface modification treatment to obtain the hydrophilic surface having a contact angle of ≥30°.

16. The method according to claim 13, wherein the surface modification treatment is corona treatment, plasma treatment, chemical treatment, surface graft treatment, or photochemical modification treatment.

17. The method according to claim 13, wherein the surface modification treatment is corona treatment.

18. A method for manufacturing a digital microfluidic chip substrate as described in claim 1, (1) The step of applying the adhesive to the surface of the circuit board, (2) The step of covering the surface of the adhesive with the hydrophilic surface of the thin film. Methods that include...

19. The method according to claim 18, further comprising the step of covering the hydrophobic surface of the thin film with a protective film in step (2).

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

21. A digital microfluidic chip comprising a digital microfluidic chip substrate according to any one of claims 1 to 12.

22. A digital microfluidic system comprising a digital microfluidic chip substrate according to any one of claims 1 to 12.

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