Preparation method of digital micro-fluidic chip

Abstract

The invention discloses a preparation method of a digital micro-fluidic chip. The preparation method comprises the following steps: providing an insulating hydrophobic membrane; forming an adhesive layer on the surface of the insulating hydrophobic film; the insulating hydrophobic film is pressed on the surface of a circuit substrate, and the adhesive layer adheres the insulating hydrophobic film and the circuit substrate. In the application, the insulating hydrophobic film and the circuit substrate are prepared independently and are combined together through the pressing process, the insulating hydrophobic preparation process does not affect the circuit substrate, and the product quality is improved.

Description

Technical Field

[0001] The present application relates to the field of digital microfluidics technology, and in particular to a method for preparing a digital microfluidics chip. Background Art

[0002] Compared to traditional microfluidics, digital microfluidic chips based on electrowetting are highly flexible and structurally simple. By applying logical electrical signals to the digital microfluidic chip, it is possible to manipulate droplets ranging in volume from nanoliters to microliters within the chip.

[0003] The digital microfluidic chip consists of a lower substrate and an upper substrate. The lower substrate includes a circuit substrate, an insulating layer, and a hydrophobic layer, and the upper substrate includes a hydrophobic layer and a conductive substrate. Applying an electric field between the lower and upper substrates can reversibly change the contact angle of the droplet between the upper and lower substrates. The insulating layer of the lower substrate is generally coated on the circuit substrate, while the hydrophobic layer is coated on the insulating layer. In the process of preparing the insulating layer, the preparation temperature is usually greater than 300°C. However, the glass transition temperature of the circuit substrate is low, and the preparation process of the insulating layer will affect the circuit substrate and cause it to melt, reducing product quality. Summary of the Invention

[0004] One purpose of the present application is to provide a method for preparing a digital microfluidic chip that is beneficial to improving product quality.

[0005] An embodiment of the present application provides a method for preparing a digital microfluidic chip, comprising the following steps:

[0006] Providing an insulating hydrophobic membrane;

[0007] forming an adhesive layer on the surface of the insulating hydrophobic film;

[0008] The insulating hydrophobic film is pressed onto the surface of a circuit substrate, wherein the adhesive layer bonds the insulating hydrophobic film and the circuit substrate.

[0009] In some embodiments, the step of "providing an insulating hydrophobic film" includes: providing an insulating layer; and preparing a hydrophobic layer on the insulating layer.

[0010] In some embodiments, the step of "preparing a hydrophobic layer on the insulating layer" includes: providing a hydrophobic coating; coating the hydrophobic coating on the surface of the insulating layer to form a hydrophobic coating; and sintering the hydrophobic coating to form the hydrophobic layer.

[0011] In some embodiments, the hydrophobic coating comprises one or more of a tetrafluoroethylene dispersion, a tetrafluoroethylene-perfluoroalkoxy ether copolymer resin dispersion, and a polyperfluoroethylene coating.

[0012] In some embodiments, the sintering temperature is 200-350° C., and the sintering time is 20-120 minutes.

[0013] In some embodiments, before the step of "sintering the hydrophobic coating", the method further includes the following steps: baking the hydrophobic coating.

[0014] In some embodiments, the method further includes the following steps: disposing a release film on the surface of the insulating hydrophobic film, wherein the release film is located on a side of the insulating hydrophobic film away from the adhesive layer.

[0015] In some embodiments, the insulating hydrophobic film is pressed onto the circuit substrate by a hot pressing process, and the hot pressing temperature is less than or equal to 180°C.

[0016] In some embodiments, the insulating hydrophobic film is a polytetrafluoroethylene film, a tetrafluoroethylene-perfluoroalkoxy ether copolymer resin film, or a polyperfluoroethylene film.

[0017] In some embodiments, the further step of: performing surface treatment on the surface where the insulating hydrophobic film and the adhesive layer are bonded.

[0018] In the preparation method of the digital microfluidic chip provided in the embodiment of the present application, the insulating hydrophobic film and the circuit substrate are prepared independently and combined together through a pressing process. The preparation process of the insulating hydrophobic film will not affect the circuit substrate. Compared with the situation where the insulating hydrophobic film is directly formed on the circuit substrate, the preparation method of the present application is more conducive to improving product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0020] Figures 1 to 6 This is a cross-sectional view of a method for preparing a digital microfluidic chip according to one embodiment of the present application.

[0021] Figure 7 A cross-sectional view of a digital microfluidic chip provided in another embodiment of the present application.

[0022] Figure 8 A cross-sectional view of an insulating hydrophobic film provided in another embodiment of the present application.

[0023] Description of main component symbols

[0024] Insulation layer 11

[0025] Hydrophobic layer 12

[0026] Insulating hydrophobic films 10, 10'

[0027] Release film 20

[0028] Adhesive layer 30

[0029] Circuit board 40

[0030] Base 41

[0031] Electrode layer 42

[0032] Lower base plate 100

[0033] Upper substrate 200

[0034] Droplet 300 DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0036] In addition, for the sake of brevity and clarity, the size or thickness of various components or layers may be exaggerated in the accompanying drawings. Throughout the text, the same numerical value refers to the same element. As used herein, the terms "and / or" and "and / or" include any and all combinations of one or more related enumerated items. In addition, it should be understood that when element A is referred to as "connecting" element B, element A can be directly connected to element B, or there may be an intermediate element C and element A and element B can be indirectly connected to each other.

[0037] Further, when describing embodiments of the present application, the use of “may” refers to “one or more embodiments of the present application.”

[0038] The technical terms used herein are for the purpose of describing specific embodiments and are not intended to limit this application. As used herein, the singular is intended to include the plural, unless the context clearly indicates otherwise. It should be further understood that the term "comprising", when used in this specification, refers to the presence of the described features, values, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, values, steps, operations, elements, components and / or combinations thereof.

[0039] It should be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, the first element, component, region, layer or part discussed below may be referred to as the second element, component, region, layer or part without departing from the teachings of the exemplary embodiments.

[0040] One embodiment of the present application provides a method for preparing a digital microfluidic chip, which includes the following steps: S1, providing an insulating hydrophobic film; S2, forming an adhesive layer on the surface of the insulating hydrophobic film; S3, pressing the insulating hydrophobic film onto the surface of a circuit substrate, wherein the adhesive layer bonds the insulating hydrophobic film and the circuit substrate to obtain a lower substrate.

[0041] In step S1, the insulating hydrophobic film can be a single-layer film structure or a multi-layer film structure. In this application, a single-layer film structure refers to a structure composed of a single film layer, and a multi-layer film structure refers to a structure composed of multiple films.

[0042] See also Figures 1 to 6 In some embodiments, the insulating hydrophobic film is a multi-layer film structure, and step S1 includes the following steps S11-S12.

[0043] Step S11, please refer to Figure 1 , providing an insulating layer 11.

[0044] The material of the insulating layer 11 includes a high-temperature resistant polymer, including but not limited to polyimide (PI), polyetheretherketone (PEEK), and polyethersulfone (PESU). The insulating layer 11 can be prepared by a coating process and a baking process. The coating process includes but is not limited to spin coating and printing. The insulating layer 11 can also be a high-temperature resistant polymer film, such as a polyimide film, a polyetheretherketone film, a polyethersulfone film, etc.

[0045] In some embodiments, the thickness of the insulating layer 11 is 5 to 40 μm. The insulating layer 11 can be transparent or non-transparent. In this embodiment, the insulating layer 11 is a transparent polyimide film.

[0046] Step S12, please refer to Figure 2 A hydrophobic layer 12 is formed on the insulating layer 11 to obtain an insulating hydrophobic film 10. The insulating hydrophobic film 10 includes the insulating layer 11 and the hydrophobic layer 12 formed on the surface of the insulating layer 11.

[0047] In some embodiments, step S12 includes the following steps: first providing a hydrophobic coating, then coating the hydrophobic coating on the surface of the insulating layer 11 to form a hydrophobic coating, and then sintering the hydrophobic coating to form the hydrophobic layer 12. The hydrophobic coating is a fluoropolymer coating or a fluoropolymer dispersion.

[0048] In some embodiments, the hydrophobic coating comprises one or more of a tetrafluoroethylene dispersion, a tetrafluoroethylene-perfluoroalkoxy ether copolymer resin dispersion, and a polyperfluoroethylene coating. Compared to a hydrophobic layer made of an amorphous fluoropolymer, the hydrophobic layer made of the above hydrophobic coating has a lower cost.

[0049] In step S12, the hydrophobic coating is sintered to improve the bonding strength between the hydrophobic layer 12 and the insulating layer 11. In some embodiments, the sintering temperature is 200-350°C and the sintering time is 20-120 minutes.

[0050] In some embodiments, the thickness of the hydrophobic layer 12 is greater than or equal to 0.5 μm to obtain excellent hydrophobic effect.

[0051] In some embodiments, the hydrophobic coating is baked before sintering. This baking removes the solvent from the surface of the hydrophobic coating, which is the solvent in the hydrophobic coating. The baking temperature is 90-120° C., and the baking time is 3-15 minutes.

[0052] In some embodiments, after step S1 , the method for preparing a digital microfluidic chip further includes the following steps: disposing a release film on the surface of the insulating hydrophobic film 10 .

[0053] See also Figure 3 The release film 20 is disposed on the surface of the hydrophobic layer 12 facing away from the insulating layer 11 to protect the hydrophobic layer 12 .

[0054] In step S2, see Figure 4 , the adhesive layer 30 is formed on the surface of the insulating layer 11 facing away from the hydrophobic layer 12 .

[0055] The adhesive layer 30 is made of an insulating material and can be formed on the surface of the insulating hydrophobic film 10 by a coating process. Specifically, step S2 includes the following steps: applying an adhesive on the surface of the insulating hydrophobic film 10 to form an adhesive coating, and baking and curing the adhesive coating to form the adhesive layer 30.

[0056] The adhesive includes one or more of an epoxy resin adhesive, an acrylate adhesive, a polyurethane adhesive, and a silicone adhesive. In some embodiments, the adhesive includes the following components in parts by weight: 35-45 parts epoxy resin, 18-28 parts carboxyl-terminated nitrile rubber, 5-7 parts copolyamide resin, 2-4 parts polyvinyl butyral resin, and 2.8-4.2 parts amine curing agent.

[0057] In step S3, see Figure 5 After lamination, the insulating layer 11 covers the circuit substrate 40 and is bonded to the circuit substrate 40 through the adhesive layer 30 .

[0058] In this embodiment, the insulating hydrophobic film 10 is pressed onto the circuit substrate 40 via a hot pressing process, which helps improve the bonding strength between the insulating hydrophobic film 10 and the circuit substrate 40. The hot pressing temperature is less than or equal to 180°C, and the hot pressing time is 40 to 50 minutes. Preferably, the hot pressing temperature is 180°C, and the hot pressing time is 45 minutes.

[0059] The circuit substrate 40 includes a base 41 and an electrode layer 42. The electrode layer 42 is arranged on the base 41 and covers a portion of the base 41. The insulating hydrophobic film 10 covers the circuit substrate 40 and is bonded to the electrode layer 42 and the base 41 through the adhesive layer 30. The base 41 is used to support the electrode layer 42. In this embodiment, the circuit substrate 40 is a printed circuit board. The base 41 is made of an insulating polymer. The base 41 is a polymer sheet, and the base 41 includes a polymer such as polyimide, polyethylene terephthalate or polyethylene naphthalate. The glass transition temperature of these polymers is generally greater than 180°C, so the hot pressing process of pressing the insulating hydrophobic film 10 onto the circuit substrate 40 will not affect the circuit substrate 40, which is beneficial to improving product quality. In other embodiments, the base 41 can be a glass slide, photo paper, silicon wafer, etc.

[0060] The electrode layer 42 is distributed in an array and includes a plurality of electrodes distributed in an array. In some embodiments, the electrode layer 42 is a patterned electrode layer formed on the substrate 41 by inkjet printing conductive ink using an inkjet printer. The conductive ink may be, but is not limited to, nanosilver conductive ink or carbon nanotube conductive ink. In other embodiments, a conductive film is formed on the surface of the substrate 41 by chemical vapor deposition, evaporation, sputtering, or other processes, and then the conductive film is patterned by photolithography or metal etching to obtain the electrode layer 42.

[0061] See also Figure 5 and Figure 6 It can be understood that after pressing the insulating hydrophobic film 10 onto the circuit substrate 40 , the following steps are further included: removing the release film 20 to obtain the lower substrate 100 .

[0062] Lower substrate 100 includes a circuit substrate 40, an adhesive layer 30, and an insulating hydrophobic film 10. Adhesive layer 30 is sandwiched between circuit substrate 40 and insulating hydrophobic film 10. Adhesive layer 30 and insulating hydrophobic film 10 together serve as a dielectric layer, insulating the electrodes of electrode layer 42 from the liquid droplets. Lower substrate 100 can be used as a single-board digital microfluidic chip.

[0063] In some embodiments, the method for preparing a digital microfluidic chip further includes the following steps.

[0064] Step S4, see Figure 7 , the lower substrate 100 and the upper substrate 200 are assembled to form a microfluidic chip.

[0065] The upper substrate 200 includes a circuit substrate (not shown) and an insulating hydrophobic film (not shown) disposed on the circuit substrate. A gap is provided between the upper substrate 200 and the lower substrate 100 for the droplets 300 to move.

[0066] See also Figure 8 In other embodiments, the insulating hydrophobic film 10' is a single-layer film structure. In the case where the insulating hydrophobic film 10' is a single-layer film structure, step S1 includes the following steps: providing an insulating hydrophobic film 10' having a single-layer film structure, and performing surface treatment on the insulating hydrophobic film 10'.

[0067] The insulating hydrophobic film 10' having a single-layer film structure is a polytetrafluoroethylene film, a tetrafluoroethylene-perfluoroalkoxy ether copolymer resin film, or a polytetrafluoroethylene film. Surface treatment can increase the surface energy of the insulating hydrophobic film 10', thereby improving the bonding strength between the insulating hydrophobic film and the adhesive layer. In this embodiment, the surface where the insulating hydrophobic film 10' is bonded to the adhesive layer is surface treated. Surface treatments include corona treatment, sodium treatment, and the like. In some embodiments, the thickness of the insulating hydrophobic film 10' is 6 to 40 μm.

[0068] In the preparation method of the microfluidic chip provided in the embodiment of the present application, the insulating hydrophobic film 10 and the circuit substrate 40 are prepared independently and combined together through a pressing process. The preparation process of the insulating hydrophobic film 10 will not affect the circuit substrate 40. Compared with the situation where the insulating hydrophobic film is directly formed on the circuit substrate, the preparation method of the present application is more conducive to improving product quality.

[0069] Some specific embodiments are listed below to better illustrate the present application.

[0070] Example 1

[0071] The fluoropolymer coating was coated on a polyimide film with a thickness of 12.5 μm to a thickness of 2 μm, and then baked at 90°C for 3 minutes, and then immediately heated to 255°C and sintered for 30 minutes to form a hydrophobic layer on the surface of the polyimide film to obtain an insulating hydrophobic film, and then the release paper was composited with the insulating hydrophobic film.

[0072] An epoxy adhesive (halogen-free epoxy resin adhesive) was coated on the side of the polyimide film away from the hydrophobic layer with a coating thickness of 15 μm, and then baked at 160° C. for 3 minutes to form an adhesive layer on the other side of the polyimide film.

[0073] The insulating hydrophobic film is pressed onto the surface of the circuit board through the adhesive layer at a pressing temperature of 180°C and a pressing pressure of 100kgf / cm 3 The pressing time is 120 minutes. After pressing, the chip is baked at 160°C for 60 minutes to obtain a digital microfluidic chip.

[0074] Example 2

[0075] The tetrafluoroethylene dispersion was uniformly dispersed by rotating it in a ball mill at 30-50 rpm for 30-60 minutes. The tetrafluoroethylene dispersion was then coated onto a 25 μm thick polyimide film to a thickness of 2 μm. The film was then baked at 120°C for 15 minutes and then immediately heated to 300°C and sintered for 30 minutes to form a hydrophobic layer on the polyimide film surface, thereby obtaining an insulating hydrophobic film. The insulating hydrophobic film was then laminated with a release paper.

[0076] An epoxy adhesive (halogen-free epoxy resin adhesive) was coated on the side of the polyimide film away from the hydrophobic layer with a coating thickness of 15 μm, and then baked at 160° C. for 3 minutes to form an adhesive layer on the other side of the polyimide film.

[0077] The insulating hydrophobic film is pressed onto the surface of the circuit board through the adhesive layer at a pressing temperature of 180°C and a pressing pressure of 100kgf / cm 3 The pressing time is 120 minutes. After pressing, the chip is baked at 160°C for 60 minutes to obtain a digital microfluidic chip.

[0078] Example 3

[0079] A fluoropolymer film (12.5 μm) was ultrasonically cleaned. The top surface of the fluoropolymer film was then wrapped for protection and immersed in a naphthalene sodium surface treatment solution (21.4% naphthalene, 3.8% sodium, 74.8% diethylene glycol dimethyl ether) for 6 hours. The film was then washed with water to convert the bottom surface of the fluoropolymer film from a hydrophobic state to a hydrophilic state, facilitating subsequent adhesive application.

[0080] An epoxy adhesive (halogen-free epoxy resin adhesive) was coated on the bottom surface of the fluoropolymer film with a coating thickness of 25 μm, and then baked at 160° C. for 3 minutes to form an adhesive layer on the bottom surface of the fluoropolymer film.

[0081] The fluoropolymer film is laminated to the circuit board surface through the adhesive layer at a lamination temperature of 180°C and a lamination pressure of 100 kgf / cm 3 The pressing time is 120 minutes. After pressing, the chip is baked at 160°C for 60 minutes to obtain a digital microfluidic chip.

[0082] The digital microfluidic chips prepared in Examples 1-3 were subjected to droplet electrowetting tests. The droplet electrowetting angles measured in each example are shown in Table 1.

[0083] The water drop angle was measured according to "GB / T 30693-2014_Measurement of the contact angle of water on plastic films." Adjacent electrodes on the circuit board were connected to the amplifier and ground terminals of the signal amplifier, respectively. Deionized water was dripped onto the digital microfluidic chip. The water drop angle on the chip was recorded as θ0 when the chip was powered off. The water drop angle on the chip when the amplifier was powered on was recorded as θ. 300V Then, after turning off the amplifier, the angle of the water drop on the chip is recorded as θ t .

[0084] Table 1

[0085] <![CDATA[θ0]]> <![CDATA[θ 300V ]]> <![CDATA[θ t ]]> <![CDATA[Δθ(θ0-θ 300V )]]> <![CDATA[θ h (θ0-θ t )]]> Example 1 115.52 83.92 109.10 31.60 6.42 Example 2 114.68 82.15 110.65 32.53 4.03 Example 3 115.37 83.66 110.89 31.71 4.48

[0086] As can be seen from Table 1, the microfluidic chip manufactured using the insulating hydrophobic membrane of the present application can meet the preset electrowetting contact angle response.

[0087] The above disclosure is only a preferred embodiment of the present application, and certainly cannot be used to limit the present application. Therefore, equivalent changes made based on the present application are still within the scope covered by the present application.

Claims

1. A method for preparing a digital microfluidic chip, characterized in that: The following steps are involved: Providing an insulating hydrophobic film; forming an adhesive layer on the surface of the insulating hydrophobic film; The insulating hydrophobic film is pressed onto the surface of a circuit substrate, wherein the adhesive layer bonds the insulating hydrophobic film and the circuit substrate.

2. The method for preparing a digital microfluidic chip according to claim 1, wherein: The step of "providing an insulating hydrophobic film" includes: Provide insulation; A hydrophobic layer is prepared on the insulating layer.

3. The method for preparing a digital microfluidic chip according to claim 2, wherein: The step of "preparing a hydrophobic layer on the insulating layer" comprises: Provide hydrophobic coatings; Applying the hydrophobic coating on the surface of the insulating layer to form a hydrophobic coating; The hydrophobic coating layer is sintered to form a hydrophobic layer.

4. The method for preparing a digital microfluidic chip according to claim 3, wherein: The hydrophobic coating comprises one or more of tetrafluoroethylene dispersion, tetrafluoroethylene-perfluoroalkoxy ether copolymer resin dispersion, and polyperfluoroethylene coating.

5. The method for preparing a digital microfluidic chip according to claim 3, wherein: The sintering temperature is 200-350° C., and the sintering time is 20-120 minutes.

6. The method for preparing a digital microfluidic chip according to claim 3, wherein: Before the step of "sintering the hydrophobic coating", the method further includes the following steps: The hydrophobic coating is baked.

7. The method for preparing a digital microfluidic chip according to claim 1, wherein: The following steps are also included: A release film is provided on the surface of the insulating hydrophobic film, wherein the release film is located on a side of the insulating hydrophobic film away from the adhesive layer.

8. The method for preparing a digital microfluidic chip according to claim 1, wherein: The insulating hydrophobic film is pressed onto the circuit substrate through a hot pressing process, and the hot pressing temperature is less than or equal to 180°C.

9. The method for preparing a digital microfluidic chip according to claim 1, wherein: The insulating hydrophobic film is a polytetrafluoroethylene film, a tetrafluoroethylene-perfluoroalkoxy ether copolymer resin film or a polyperfluoroethylene film.

10. The method for preparing a digital microfluidic chip according to claim 9, wherein: The following steps are also included: The surface where the insulating hydrophobic film and the adhesive layer are bonded is subjected to surface treatment.

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