A flexible thin-film microfluidic chip, its fabrication method and application

Abstract

This invention discloses a method for fabricating a flexible thin-film microfluidic chip, belonging to the field of microfluidic technology. The method includes the following steps: using a first polydimethylsiloxane film as a substrate material, etching the substrate material using an ultraviolet femtosecond laser processing method to obtain a substrate material containing a microfluidic structure; bonding a second polydimethylsiloxane film onto the substrate material containing the microfluidic structure; and then encapsulating the sides of the bonding layer with liquid polydimethylsiloxane to obtain the flexible thin-film microfluidic chip. The fabrication method according to this invention avoids problems such as microchannel deformation, scorching, or irregular edges during processing.

Description

Technical Field

[0001] This invention relates to the field of microfluidic technology, and more specifically to a method for fabricating a flexible thin-film microfluidic chip. Background Technology

[0002] Microchannel technology, as an important component of micro-electro-mechanical systems (MEMS) and microfluidic systems, is widely used in numerous fields such as biomedicine, chemical analysis, and environmental monitoring. With the development of these fields, the application demands for microchannels are increasing, and the requirements for their structural precision, material compatibility, and fabrication processes are also gradually rising. There are many methods for fabricating microchannels, commonly including photolithography, soft etching, hot embossing, laser processing, and electrodeposition.

[0003] Photolithography is one of the most common methods for fabricating microchannels. It involves coating, exposing, and developing photosensitive materials, followed by etching to form micron-scale patterns. However, this method is complex, costly, and primarily uses silicon or glass as the substrate. Soft lithography typically combines photolithography with elastomers such as polydimethylsiloxane (PDMS) to replicate micron-scale structures on a mold surface. Soft lithography relies on elastomer molds (such as PDMS) for replication; however, due to the limited mechanical strength of PDMS, the molds are prone to wear or deformation during use, affecting fabrication accuracy, limiting dimensional precision, and resulting in poor process repeatability. Hot embossing uses high temperature and pressure to imprint micron-scale structures from a mold onto a polymer material. This method requires high temperatures and pressures, resulting in high equipment costs and a long cooling and demolding process. Electrodeposition selectively deposits metals or other materials onto a substrate surface to form microchannel structures. This method is complex, with difficulty in controlling deposition uniformity, and is limited by the available metal materials. With the continuous development of microfluidic technology, developing a simple, efficient, and versatile microchannel fabrication method applicable to various materials is a pressing issue for researchers.

[0004] In recent years, laser processing has gained increasing attention in microchannel fabrication due to its high resolution, flexibility, and mask-free operation. Laser processing is a precision machining method that utilizes high-energy-density laser beams to directly etch micron-scale structures onto material surfaces. This method is applicable to the fabrication of microchannels for various materials, and it shows particular advantages in rapid prototyping and the fabrication of microchannels for heterogeneous materials.

[0005] Laser processing technology offers new solutions for the design and development of microfluidic systems, enabling the fabrication of complex microchannels and multifunctional integration. It allows for the fabrication of high-precision, diverse material processing, non-contact machining, high efficiency, minimal or no post-processing, high repeatability, flexibility, and applicability to complex three-dimensional microchannels. Currently, CO2 lasers are commonly used in laser etching for microchannel fabrication. CO2 laser direct writing technology offers advantages in microchannel manufacturing, such as high efficiency, non-contact processing, and precision. However, the heat generated during CO2 laser processing can easily lead to localized melting or thermal damage to the material, especially when processing heat-sensitive materials such as polymers. This thermal effect can cause microchannel deformation, scorching, or irregular edges, thus affecting the performance of the microfluidic device. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for the fine removal and processing of microchannel structures using ultraviolet ultrafast lasers, providing effective technical support for the fabrication of chips that generate discrete microdroplets.

[0007] The first objective of this invention is to provide a method for fabricating a flexible thin-film microfluidic chip, comprising the following steps:

[0008] Using a first polydimethylsiloxane film as the substrate material, the substrate material was etched using an ultraviolet femtosecond laser processing method to obtain a substrate material with a microchannel structure.

[0009] A second polydimethylsiloxane film is bonded onto a substrate material containing a microfluidic structure; then, liquid polydimethylsiloxane is used to encapsulate the sides of the bonded layer to obtain a flexible thin-film microfluidic chip.

[0010] In a preferred embodiment of the present invention, the laser beam wavelength of the laser processing technology is 315nm to 400nm, for example, the laser beam wavelength is 315nm, 320nm, 340nm, 360nm, 380nm, 400nm, etc.

[0011] The laser pulse width is 50fs to 10ps, for example, laser pulse widths of 50fs, 100fs, 1ps, 10ps, etc.

[0012] The laser pulse frequency is 10kHz to 100kHz, for example, laser pulse frequencies of 10kHz, 20kHz, 30kHz, 40kHz, 50kHz, 60kHz, 70kHz, 80kHz, 90kHz, 100kHz, etc.

[0013] The beam scanning speed ranges from 100 mm / s to 2000 mm / s, with specific beam scanning speeds of 100 mm / s, 500 mm / s, 1000 mm / s, 15000 mm / s, and 2000 mm / s.

[0014] The number of scans ranges from 3 to 30, including 3, 6, 9, 12, 15, 18, 21, 24, 27, and 30 scans, but is not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0015] In a preferred embodiment of the present invention, the liquid polydimethylsiloxane is prepared by cross-linking and curing polydimethylsiloxane and a curing agent in a mass ratio of 5 to 8:1.

[0016] For example, in liquid polydimethylsiloxane, the mass ratio of polydimethylsiloxane to curing agent is 5:1, 6:1, 7:1, 8:1, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0017] In a preferred embodiment of the present invention, the first polydimethylsiloxane film is prepared by cross-linking and curing polydimethylsiloxane and a curing agent in a mass ratio of 5 to 10:1; the thickness of the first polydimethylsiloxane film is 0.1 mm to 3 mm.

[0018] In the first polydimethylsiloxane film, the mass ratio of polydimethylsiloxane to curing agent is 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0019] The thickness of the first polydimethylsiloxane film is 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0020] In a preferred embodiment of the present invention, the second polydimethylsiloxane film is prepared by cross-linking and curing polydimethylsiloxane and a curing agent in a mass ratio of 8 to 15:1; the thickness of the second polydimethylsiloxane film is 0.1 mm to 1 mm.

[0021] In the second polydimethylsiloxane film, the mass ratio of polydimethylsiloxane to curing agent is 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, etc.

[0022] The thickness of the second polydimethylsiloxane film is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] In a preferred embodiment of the present invention, the microchannel opening width of the matrix material containing the microchannel structure is 10μm to 1000μm, for example, the microchannel opening width is 10μm, 200μm, 400μm, 600μm, 800μm, 1000μm, etc.

[0024] The depth ranges from 10μm to 1500μm, for example, depths of 10μm, 100μm, 300μm, 600μm, 900μm, 1200μm, 1500μm, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0025] In a preferred embodiment of the present invention, the cross-section of the microchannel in the matrix material containing the microchannel structure is rectangular, V-shaped, or trapezoidal.

[0026] The second objective of this invention is to provide a flexible thin-film microfluidic chip prepared by the above-described preparation method.

[0027] A third objective of this invention is to provide the application of the above-described flexible thin-film microfluidic chip in the fabrication of microdroplets.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) In this invention, a substrate material containing a microchannel structure is prepared by processing a substrate material using ultraviolet femtosecond laser processing. Because the femtosecond laser pulse duration is extremely short, there is almost no thermal effect, enabling fine, smooth, and high-precision microstructure processing, which is particularly suitable for the fabrication of microchannels in heat-sensitive materials such as PDMS. The preparation method according to this invention avoids problems such as microchannel deformation, scorching, or irregular edges during processing. The preparation method according to this invention can be applied to the processing of flexible thin-film microchannel chips from various materials, including colorless transparent flexible thin films.

[0030] (2) The method of the present invention can realize the personalized setting of microchannel structures with different sizes, cross-sectional shapes and path designs to meet the needs of generating discrete droplets of different sizes.

[0031] (3) The present invention uses liquid PDMS to encapsulate the microchannel structure, which successfully solves the problem of leakage that occurs during the generation of discrete droplets. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the matrix material containing the microchannel structure in Example 1.

[0033] Figure 2 This is a cross-sectional schematic diagram of the flexible thin-film microfluidic chip in Example 2.

[0034] Figure 3The images shown are microscopic views of the laser-processed microchannels on the surface of the flexible thin film in Example 1, where a is a three-dimensional structural morphology image and b is a profile image of section A.

[0035] Figure 4 The image shows a microscopic view of the intersection region of two mutually perpendicular microchannels in the laser processing of the flexible thin film surface in Example 2, where a is a three-dimensional structural morphology image and b is a profile image of section B.

[0036] Figure description: 1-Matrix material, 2-Second PDMS film, 3-Microchannel, 4-Reservoir, 5-First injection port, 6-Second injection port, 7-Outlet. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] To achieve precise fabrication of microchannel structures in PDMS materials, this invention employs an ultraviolet femtosecond laser for patterned etching and micromachining of the microchannels. Due to its extremely short pulse width and high energy density, the ultraviolet femtosecond laser can form high-precision microstructures on and within the PDMS surface, reducing material damage caused by thermal effects.

[0039] Based on this, the present invention first uses CAD software to design the microchannel pattern required for the experiment and imports it into the laser processing system. The beam of the ultraviolet femtosecond laser is focused onto the surface of the PDMS material through a lens. The interaction between the laser beam and the PDMS material causes nonlinear optical effects in the material, resulting in high-precision etching. Under this high energy density, the PDMS material is rapidly removed to form the desired microchannel structure.

[0040] During laser processing, the ultra-short duration of femtosecond laser pulses prevents significant thermal diffusion in PDMS materials, thus minimizing thermal damage. Simultaneously, ultraviolet lasers possess high photon energy, enabling the precise fabrication of micron- and submicron-scale structures in PDMS materials, making them suitable for complex microfluidic network designs.

[0041] Furthermore, by adjusting parameters such as laser power, pulse frequency, and scanning speed, the depth and width of the microchannels can be precisely controlled. This non-contact processing method not only improves the processing accuracy of microchannels but also avoids material deformation or damage problems that may occur in traditional micromachining techniques.

[0042] To improve the mechanical strength and durability of PDMS microchannels, the microchannel structure is typically encapsulated after fabrication. Another layer of PDMS is chosen as the encapsulation material to form a complete microfluidic chip. After encapsulation, the microchannels can be used in biomedical analysis, chemical reactions, or other microfluidic system applications.

[0043] It should be noted that the PDMS and curing agent used in this invention were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with product number S466341.

[0044] Example 1

[0045] This embodiment provides a method for fabricating a flexible thin-film microfluidic chip, including the following steps:

[0046] Step 1: Weigh PDMS and curing agent at a mass ratio of 8:1, mix them evenly, and cure at room temperature for 2 hours to obtain a first PDMS film with a thickness of 2 mm, a length of 80 mm, and a width of 30 mm.

[0047] Step 2: Using a 343nm ultraviolet femtosecond laser with a pulse width of 209fs, a laser frequency of 100kHz, and a beam scanning speed of 1500mm / s, the ultraviolet femtosecond laser power is adjusted to 5W, and the substrate material containing a microchannel structure is obtained by processing on the first PDMS film through 6 scans. In this embodiment, the cross-section of the microchannel in the substrate material containing the microchannel structure is an inverted trapezoid, the upper base width of the inverted trapezoidal microchannel is 300μm, the lower base width is 240μm, and the microchannel depth is 150μm.

[0048] Step 3: Weigh PDMS and curing agent at a mass ratio of 15:1, mix them evenly, and cure at room temperature for 2 hours to obtain a second PDMS film with a thickness of 0.5 mm.

[0049] The second PDMS film is bonded to a substrate material containing a microfluidic structure.

[0050] Step 4: Weigh PDMS and curing agent at a mass ratio of 5:1, mix them evenly to obtain liquid polydimethylsiloxane.

[0051] Liquid polydimethylsiloxane was uniformly applied to the sides of the substrate material containing the microfluidic structure and the second PDMS film bonding layer, and then allowed to stand at room temperature for 0.5 hours to cure and form a flexible thin film microfluidic chip by encapsulating the substrate material containing the microfluidic structure and the second PDMS film.

[0052] Example 2

[0053] This embodiment provides a method for fabricating a flexible thin-film microfluidic chip, including the following steps:

[0054] Step 1: Weigh PDMS and curing agent at a mass ratio of 8:1, mix them evenly, and cure at room temperature for 2 hours to obtain a first PDMS film with a thickness of 2 mm, a length of 80 mm, and a width of 30 mm.

[0055] Step 2: Using a 343nm ultraviolet femtosecond laser with a pulse width of 209fs, a laser frequency of 100kHz, and a beam scanning speed of 1500mm / s, the ultraviolet femtosecond laser power is adjusted to 5W, and the substrate material containing a microchannel structure is obtained by processing on the first PDMS film through 15 scans. In this embodiment, the cross-section of the microchannel in the substrate material containing the microchannel structure is an inverted trapezoid, with a bottom width of 200μm, an top width of 350μm, and a microchannel depth of 400μm.

[0056] Step 3: Weigh PDMS and curing agent at a mass ratio of 15:1, mix them evenly, and cure at room temperature for 2 hours to obtain a second PDMS film with a thickness of 0.5 mm.

[0057] The second PDMS film is bonded to a substrate material containing a microfluidic structure.

[0058] Step 4: Weigh PDMS and curing agent at a mass ratio of 5:1, mix them evenly to obtain liquid polydimethylsiloxane.

[0059] Liquid polydimethylsiloxane was uniformly applied to the sides of the substrate material containing the microfluidic structure and the second PDMS film bonding layer, and then allowed to stand at room temperature for 0.5 hours to cure and form a flexible thin film microfluidic chip by encapsulating the substrate material containing the microfluidic structure and the second PDMS film.

[0060] Example 3

[0061] This embodiment provides a method for fabricating a flexible thin-film microfluidic chip, including the following steps:

[0062] Step 1: Weigh PDMS and curing agent at a mass ratio of 5:1, mix them evenly, and cure at room temperature for 2 hours to obtain a first PDMS film with a thickness of 0.1 mm, a length of 80 mm, and a width of 30 mm.

[0063] Step 2: Using a 343nm ultraviolet femtosecond laser with a pulse width of 209fs, a laser frequency of 100kHz, and a beam scanning speed of 1500mm / s, the ultraviolet femtosecond laser power is adjusted to 5W, and the substrate material containing a microchannel structure is obtained by processing on the first PDMS film through 20 scans. In this embodiment, the cross-section of the microchannel in the substrate material containing the microchannel structure is V-shaped, the upper bottom width of the V-shaped microchannel is 10μm, and the depth of the microchannel is 20μm.

[0064] Step 3: Weigh PDMS and curing agent at a mass ratio of 8:1, mix them evenly, and cure at room temperature for 2 hours to obtain a second PDMS film with a thickness of 0.1 mm.

[0065] The second PDMS film is bonded to a substrate material containing a microfluidic structure.

[0066] Step 4: Weigh PDMS and curing agent at a mass ratio of 5:1, mix them evenly to obtain liquid polydimethylsiloxane.

[0067] Liquid polydimethylsiloxane was uniformly applied to the sides of the substrate material containing the microfluidic structure and the second PDMS film bonding layer, and then allowed to stand at room temperature for 0.5 hours to cure and form a flexible thin film microfluidic chip by encapsulating the substrate material containing the microfluidic structure and the second PDMS film.

[0068] Example 4

[0069] This embodiment provides a method for fabricating a flexible thin-film microfluidic chip, including the following steps:

[0070] Step 1: Weigh PDMS and curing agent at a mass ratio of 8:1, mix them evenly, and cure at room temperature for 2 hours to obtain a first PDMS film with a thickness of 2 mm, a length of 80 mm, and a width of 30 mm.

[0071] Step 2: Using a 343nm ultraviolet femtosecond laser with a pulse width of 209fs, a laser frequency of 100kHz, and a beam scanning speed of 1500mm / s, the ultraviolet femtosecond laser power is adjusted to 5W, and the substrate material with a microchannel structure is obtained by processing on the first PDMS film through 20 scans. In this embodiment, the cross-section of the microchannel in the substrate material with the microchannel structure is rectangular, the width of the rectangular microchannel is 1000μm, and the depth of the microchannel is 1500μm.

[0072] Step 3: Weigh PDMS and curing agent at a mass ratio of 15:1, mix them evenly, and cure at room temperature for 2 hours to obtain a second PDMS film with a thickness of 0.5 mm.

[0073] The second PDMS film is bonded to a substrate material containing a microfluidic structure.

[0074] Step 4: Weigh PDMS and curing agent at a mass ratio of 5:1, mix them evenly to obtain liquid polydimethylsiloxane.

[0075] Liquid polydimethylsiloxane was uniformly applied to the sides of the substrate material containing the microfluidic structure and the second PDMS film bonding layer, and then allowed to stand at room temperature for 0.5 hours to cure and form a flexible thin film microfluidic chip by encapsulating the substrate material containing the microfluidic structure and the second PDMS film.

[0076] The flexible thin-film microfluidic chip prepared in Example 1 is as follows: Figure 1 and Figure 2 As shown, the flexible thin-film microfluidic chip includes a substrate material 1, a second PDMS film 2, a microchannel 3, a liquid reservoir 4, a first injection port 5, a second injection port 6, and an outlet 7.

[0077] In the preparation of microdroplets, the first injection port 5 and the second injection port 6 are connected to an external inlet tube via a disposable intravenous infusion needle, and the outlet port 7 is directly connected to the outlet tube. The external inlet tube has an inner diameter of φ0.05~φ0.5mm and an outer diameter of φ0.5~φ2mm; the external outlet tube has an inner diameter of φ0.1~φ1mm and an outer diameter of φ0.5~φ2mm. Driven by the pump, the discrete phase liquid enters from the second injection port 6, and the continuous phase liquid enters from the first injection port 5. The discrete and continuous phase liquids meet at the intersection. The discrete phase liquid continues to extend to form a "plug-like" or "jet-like" liquid column, which is then clamped by the shearing and squeezing action of the continuous phase liquid, dispersing into droplets in the continuous phase liquid as tiny volume units. These droplets flow into the storage tank and then flow out through the outlet port 7. The profile of the A-section of the flexible thin film microchannel prepared by ultraviolet femtosecond laser in Example 1 was measured using a confocal microscope. Figure 3 As shown, the bottom width is approximately 240μm, the top width is approximately 300μm, the depth is approximately 150μm, and the cross-sectional profile is an inverted trapezoidal structure.

[0078] The profile of section B at the intersection of the flexible thin-film microchannel chip prepared by ultraviolet laser in Example 2 was measured using confocal microscopy. Figure 4 As shown, the bottom width is approximately 200μm, the top width is approximately 350μm, and the depth is approximately 400μm.

[0079] As can be seen, this invention successfully fabricates trapezoidal microchannels on a PDMS substrate. The microchannel structure is regular, and the surface shows no obvious damage. The encapsulated microchannels exhibit excellent flow conductivity, making them suitable for applications in cell culture and analysis in biomedicine.

[0080] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0081] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for fabricating a flexible thin-film microfluidic chip, characterized in that, Includes the following steps: Using a first polydimethylsiloxane film as the substrate material, the substrate material was etched using an ultraviolet femtosecond laser processing method to obtain a substrate material containing a microchannel structure; A second polydimethylsiloxane film is bonded onto a substrate material containing a microfluidic structure; then, liquid polydimethylsiloxane is used to encapsulate the sides of the bonded layer to obtain a flexible thin-film microfluidic chip.

2. The method for fabricating a flexible thin-film microfluidic chip according to claim 1, characterized in that, The laser beam wavelength of the laser processing technology is 315nm~400nm, the laser pulse width is 50fs~10ps, the laser pulse frequency is 10kHz~100kHz, the beam scanning speed is 100mm / s~2000mm / s, and the number of scans is 3 to 30.

3. The method for fabricating a flexible thin-film microfluidic chip according to claim 1, characterized in that, Liquid polydimethylsiloxane is prepared by cross-linking and curing polydimethylsiloxane and curing agent in a mass ratio of 5 to 8:

1.

4. The method for fabricating a flexible thin-film microfluidic chip according to claim 1, characterized in that, The first polydimethylsiloxane film is prepared by cross-linking and curing polydimethylsiloxane and a curing agent in a mass ratio of 5 to 10:1; the thickness of the first polydimethylsiloxane film is 0.1 mm to 3 mm.

5. The method for fabricating a flexible thin-film microfluidic chip according to claim 1, characterized in that, The second polydimethylsiloxane film is prepared by cross-linking and curing polydimethylsiloxane and a curing agent in a mass ratio of 8 to 15:1; the thickness of the second polydimethylsiloxane film is 0.1 mm to 1 mm.

6. The method for fabricating a flexible thin-film microfluidic chip according to claim 1, characterized in that, The microchannel opening width of the matrix material containing the microchannel structure is 10μm to 1000μm, and the depth is 10μm to 1500μm.

7. The method for fabricating a flexible thin-film microfluidic chip according to claim 1, characterized in that, The microchannel cross-section of the matrix material containing the microchannel structure is rectangular, V-shaped, or trapezoidal.

8. The flexible thin-film microfluidic chip prepared by the preparation method according to any one of claims 1-7.

9. The application of the flexible thin-film microfluidic chip according to claim 7 in the preparation of microdroplets.

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