Manufacturing method of micro-fluidic chip with controllable wettability through ultrafast laser direct writing
By employing femtosecond laser direct writing and oxygen plasma bonding, the problems of complex processes and cumbersome procedures in microfluidic chip manufacturing have been solved, enabling high-precision and simplified microfluidic chip manufacturing suitable for small-scale production.
Patent Information
- Application Number
- CN202510923832.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-04
- Publication Date
- 2025-10-28
AI Technical Summary
Existing microfluidic chip manufacturing methods suffer from problems such as complex processes, expensive equipment or high environmental requirements, insufficient processing accuracy or cumbersome procedures, especially lacking simple and efficient preparation methods for small-batch production.
By employing a method combining femtosecond laser direct writing with PET film protection and oxygen plasma bonding, microchannels are scanned and etched on the surface of a hydrophobic polymer with methyl groups, and the nanostructure is reconstructed, achieving superhydrophobic and superoleophilic properties, simplifying the manufacturing process and improving etching precision.
It achieves high-precision, simplified microfluidic chip manufacturing, with a single chip production time of less than 10 minutes. It is suitable for small-scale production, has efficient wettability control and structural controllability, and is suitable for early-stage R&D and small-batch production.
Smart Images
Figure CN120838488A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for manufacturing microfluidic chips, specifically a method for manufacturing microfluidic chips with controllable wettability via ultrafast laser direct writing. Background Technology
[0002] Microfluidics is an interdisciplinary technology that precisely manipulates microfluidics within micrometer-scale channels. Its core function lies in miniaturizing, integrating, increasing throughput, and automating laboratory operations, playing a crucial role in fields such as medical diagnostics, biological research, drug development, industrial production, and materials synthesis. Among these processes, the fabrication of microfluidic chips is integral to the entire research, verification, and production of microfluidics technology, and is one of the core processes in the entire field.
[0003] Current methods for manufacturing microfluidic chips mainly fall into three categories: photolithography and etching technology, polymer molding technology, and laser direct processing technology.
[0004] 1. Photolithography uses ultraviolet light to transfer patterns to a photoresist coating substrate, achieving submicron resolution, but the process is complex and the equipment is expensive. Etching is usually plasma etching, which can process high aspect ratio structures, but requires a vacuum environment and is relatively slow. Therefore, photolithography and etching technologies are only suitable for the fabrication of microfluidic chips with extremely high precision requirements.
[0005] 2. Soft lithography (such as PDMS molding) in polymer molding technology has low cost, short cycle and good biocompatibility, but the microfluidic chips produced by it are easy to deform and have poor batch consistency. Thermoplastic molding is suitable for large-scale production and the microfluidic chips produced by it have high mechanical strength, but high temperature will cause microstructure shrinkage and it is difficult to manufacture multilayer chips. Therefore, polymer molding technology is mostly suitable for the preparation of microfluidic chips with large batch and low processing precision.
[0006] 3. Laser direct processing has lower manufacturing costs compared to photolithography and does not require templates compared to polymer molding, making it suitable for small-batch manufacturing in the chip pre-research process. Kim et al. (Fabrication of Perfluoropolyether Microfluidic Devices Using Laser Engraving for Uniform Droplet Production. Micromachines 2024, 15, 599.) used CO2 laser direct writing technology to fabricate a cross-junction microchannel microfluidic device based on perfluoropolyether. The microchannel inner surface of their microfluidic device is smooth and can generate uniform water and oil droplets. Shan et al. (Femtosecond laser hybridfabrication of a 3D microfluidic chip for PCR application. Optics express 2020, 28, 25716-25722.) used femtosecond laser modification combined with wet etching technology. They first used laser to perform three-dimensional modification inside the material, and then used hydrofluoric acid to selectively etch along the laser modification trajectory, realizing the precision fabrication of a three-dimensional microfluidic chip inside a hard and brittle material. While the aforementioned laser processing method for fabricating microfluidic chips does not require a template, subsequent steps such as chemical immersion are still necessary for wettability modification, making the sample preparation process still cumbersome. Therefore, finding a microfluidic chip manufacturing method with a short preparation cycle, simple procedures, and high resolution remains a challenge. Summary of the Invention
[0007] The purpose of this invention is to address the shortcomings of existing technologies, such as complex and expensive photolithography processes, high environmental requirements and slow etching speeds, insufficient processing precision in polymer molding, and cumbersome laser direct processing procedures. The invention provides a method for manufacturing microfluidic chips with controllable wettability through ultrafast laser direct writing.
[0008] To achieve the above objectives, the technical solution provided by this invention is as follows:
[0009] A method for manufacturing a microfluidic chip with controllable wettability via ultrafast laser direct writing, characterized by the following steps:
[0010] Step 1, Preparation of the sample to be processed;
[0011] Apply a PET film to the surface of the sample to be processed;
[0012] The sample to be processed is a hydrophobic polymer with methyl groups;
[0013] Step 2: Laser direct writing scanning etching of microchannels;
[0014] Using femtosecond lasers, microchannels are scanned and etched on the sample to be processed based on the morphology of the microfluidic chip, while reconstructing the nanostructure on the surface of the microchannels.
[0015] The pulse width of the femtosecond laser is set to 50fs-200fs, the repetition frequency to 100kHz-200kHz, the single pulse energy to 10μJ-20μJ, and the scanning speed to 200mm / s-500mm / s.
[0016] Step 3, remove the PET film;
[0017] Step 4: Microfluidic chip bonding;
[0018] The sample to be processed is irradiated with oxygen plasma and bonded to the encapsulation material. Then, it is heated and ventilated to obtain a microfluidic chip.
[0019] Furthermore, in step 2, the scanning interval is 15-20 micrometers, and the scan is performed 10-13 times.
[0020] Furthermore, in step 1, the thickness of the PET film is 10-50 micrometers.
[0021] Furthermore, in step 2, the pulse width is 200 fs, the repetition frequency is 100 kHz, the single pulse energy is 20 μJ, the scanning speed is 500 mm / s, the scanning interval is 15 micrometers, and the scan is performed 10 times.
[0022] Furthermore, in step 2, the limit linewidth of the scanning etching is less than or equal to 20 micrometers.
[0023] Furthermore, in step 2, the maximum linewidth of the scanning etching is 10 micrometers.
[0024] The beneficial effects of this invention are:
[0025] 1. This invention utilizes femtosecond laser direct writing to scan and etch microchannels on the surface of the sample to be processed, and then bonds them with the encapsulation material through oxygen plasma to form a microfluidic chip. Taking advantage of the femtosecond laser's ability to simultaneously achieve subtractive processing and surface modification, as well as the hydrophobic polymer properties of the sample containing methyl groups, the micron-sized structure of the sample to be processed is scanned and etched to achieve the structural design and manufacturing of the microfluidic chip. At the same time, the nanostructure of the surface is reconstructed to achieve the control of wettability, endowing it with superhydrophobic and superoleophilic properties, and simultaneously realizing a microfluidic chip with controllable morphology and wettability.
[0026] 2. This invention combines the characteristics of hydrophobic polymer materials with methyl groups, such as PDMS, and adopts a strategy of low single-pulse energy, high scanning speed and multiple repetitions to achieve accurate etching of materials without damaging their chemical composition.
[0027] 3. This invention can achieve precision microchannel scanning and etching with a linewidth of 10 micrometers or more in a single scan without setting a template. By setting specific scanning intervals and scanning times, the contact angle of the inner wall of the microchannel can reach more than 150°, and the etching accuracy is high. The droplet generation size can be controlled from 60 to 300 micrometers depending on the width of the microchannel.
[0028] 4. The microfluidic production process of this invention is simple, comprehensively simplifies and shortens the existing microfluidic chip manufacturing process. It realizes microchannel etching and wettability control on the material surface through single laser direct writing, shortens the manufacturing cycle, and the manufacturing time of a single chip can be completed in about 10 minutes. It has important application value in the early research and development and small-scale production of microfluidic chips, and provides a more convenient method for the pre-research and preparation of small batches of chips. Attached Figure Description
[0029] Figure 1 This is a flowchart illustrating an embodiment of the present invention;
[0030] Figure 2 These are schematic diagrams of the microchannels with different processing parameters under an optical microscope in the embodiments of the present invention; wherein, (a) is a cross-sectional view of the microchannel, (b) is a schematic diagram of the structure of the microchannel, and (c) is a schematic diagram of the nanostructure on the surface of the microchannel.
[0031] Figure 3 This is a schematic diagram of the contact angles for different processing parameters in the embodiments of the present invention; (a) is the water contact angle of the sample surface to be processed before laser direct writing, (b) is the water contact angle of the microchannel surface after laser direct writing, and (c) is the water contact angle of the microchannel surface corresponding to the four sets of parameters in step 2 respectively.
[0032] Figure 4 This is a schematic diagram of the cross-shaped water-in-oil droplet generator prepared in the embodiments of the present invention and its usage process; (a) is a schematic diagram of the structure of the cross-shaped water-in-oil droplet generator under an optical microscope; (b) is a schematic diagram of the generation process of water-in-oil droplets; (c) is a schematic diagram of the structure of water-in-oil droplets of different diameters obtained under different liquid flow rates under an optical microscope; (d) is a schematic diagram of the relationship between the flow rate of water and the flow rate of oil and the droplet size; (e) is a schematic diagram of the relationship between the flow rate of water and the flow rate of oil and the number of droplets.
[0033] Figure 5 This is a schematic diagram of the structure of the cross-shaped water-in-oil droplet generator prepared in the embodiments of the present invention. Detailed Implementation
[0034] This invention provides a method for manufacturing a microfluidic chip with controllable wettability through ultrafast laser direct writing, such as... Figure 1 As shown, this embodiment takes a microfluidic chip with a depth of 100 micrometers as an example, and specifically includes the following steps:
[0035] Step 1, Preparation of the sample to be processed;
[0036] A PET film with a thickness of only 10 micrometers is attached to the surface of the sample to be processed. In this step, PET is used as a sacrificial layer to protect the surface flatness of the areas not scanned by the laser.
[0037] In this embodiment, the sample to be processed can be polydimethylsiloxane (PDMS). In other embodiments, the sample to be processed can also be other hydrophobic polymers with methyl groups. The thickness of the PET film ranges from 10 to 50 micrometers.
[0038] Methyl groups have low surface energy and a large contact angle with intrinsic water, thus polymers containing methyl groups are generally hydrophobic. Femtosecond laser-induced surface nanostructures can amplify the wetting properties of the material itself, making hydrophobic materials even more hydrophobic. Therefore, this invention utilizes the characteristics of methyl groups and femtosecond lasers, and selecting hydrophobic polymers containing methyl groups is more conducive to achieving superhydrophobic properties in microchannels after laser direct writing.
[0039] Step 2: Laser direct writing scanning etching of microchannels;
[0040] Femtosecond lasers are used to scan and etch microchannels on the sample to be processed based on the morphology of the microfluidic chip. The etching depth of the microchannels is related to the surface nanostructure, pulse width, repetition frequency, single pulse energy, scanning speed, scanning interval between each row of the progressive scan, and the number of repeated scans.
[0041] To simultaneously achieve microchannel structure fabrication and surface wettability control, this invention employs short pulse widths, high repetition rates, high scanning speeds, and low single-pulse energy. Through localized thermal accumulation, laser direct-write scanning etching is achieved. For hydrophobic polymer materials with methyl groups, such as PDMS, the strategy of low single-pulse energy, high scanning speed, and multiple repetitions can achieve accurate etching without damaging the material's chemical composition. Building upon micron-level precision etching, this invention further controls the accurate reconstruction of ablation nanoparticles through processing parameters, forming specific nanostructures on the etched microchannel surface. These nanostructures can achieve superhydrophobic properties on the inner walls of the grooves without any additional chemical modifications, greatly simplifying the microfluidic chip fabrication process. Furthermore, these nanostructures are extremely small and do not interfere with the flow of liquid within the microfluidic chip. This dual-purpose strategy ensures processing accuracy while eliminating the need for templates and superhydrophobic chemical modifications, significantly reducing the fabrication steps.
[0042] In this embodiment, a femtosecond laser with a pulse width of 200 fs, a repetition frequency of 100 kHz, a single pulse energy of 20 μJ, and a scanning speed of 500 mm / s was used to perform scanning etching to obtain four sets of typical parameters for the microchannels: a scanning spacing of 10 μm and 7 scans; a scanning spacing of 15 μm and 10 scans; a scanning spacing of 20 μm and 13 scans; and a scanning spacing of 25 μm and 20 scans. The etching depth for each set was 100 μm.
[0043] Figure 2 The image shows an electron microscope image of the microchannel etching process. It can be seen that various processing parameters can be used to construct a graded rough structure. G1, G2, G3, and G4 in the image correspond to the four sets of parameters mentioned above. Among them, group G2, with a scanning interval of 15 micrometers and 10 scans, produces nanostructures of moderate size, low surface roughness, and no molten reconstruction layer. The surface roughness is approximately 0.5 micrometers, with a water contact angle of 150.5 degrees and an oil contact angle of 0 degrees. It exhibits the lowest surface roughness and best hydrophobicity, making it the most suitable processing parameter. Although group G3 has a higher water contact angle, its surface roughness is worse than group G2. Therefore, the scanning interval and number of scans for group G2 are preferred.
[0044] The pulse width of this invention is 50fs-200fs, the repetition frequency is 100kHz-200kHz, the single pulse energy is set to 10-20μJ, the scanning speed is 200-500mm / s, the scanning interval is set to 15-20 micrometers, and the number of scans is set to 10-13.
[0045] Figure 3The figures show the changes in contact angle of the sample surface before and after laser direct writing. (a) shows the contact angle of water on the sample surface before laser direct writing, which is 114.5 degrees; (b) shows the contact angle of water on the sample surface after laser direct writing, which is 150.5 degrees, demonstrating that laser direct writing achieves the transformation of the sample from hydrophobic to superhydrophobic; (c) shows the contact angles after scanning and etching using different processing parameters in the four sets mentioned above, all of which demonstrate that laser direct writing significantly improves the sample contact angle.
[0046] Step 3, surface cleaning;
[0047] After the scanning etching is completed, the PET film is removed, and the sputtered ablation material falls off along with the film.
[0048] Step 4: Microfluidic chip bonding;
[0049] The sample to be processed is irradiated with oxygen plasma, then stably bonded to the encapsulation material, and finally heated and ventilated to obtain a microfluidic chip. Oxygen plasma treatment causes PDMS to temporarily lose hydrophobic groups, but the hydrophobicity is quickly restored after heating and ventilating. Commonly used encapsulation materials include glass or other thin films.
[0050] In this embodiment, step 2 uses four sets of parameters to obtain four different microfluidic chips, which have certain differences in effect. Analyzing the data of the four sets of microfluidic chips reveals the reasons for the differences in wettability. When the scanning interval is too small (G1 group), the heat accumulation of the previous row does not completely disappear during line-by-line scanning, and the sample to be processed will be etched again, resulting in fewer nanoparticles and more molten material observed under an electron microscope, which is not conducive to the amplification of wettability (the transition from hydrophobic to superhydrophobic). When the scanning interval is too large (G4 group), there are unscanned gaps between the scanning intervals, which is not conducive to the regularity of the microstructure of the microchannel. Therefore, a scanning interval of 15 micrometers and 10 scans are most suitable for G2 group.
[0051] like Figure 4 and Figure 5 As shown, a classic cross-shaped water-in-oil droplet generator was prepared using the above method and the parameters of group G2. Due to the high preparation precision of this invention, its inner wall has good superhydrophobic and superoleophobic properties, and the generation of oil droplets at the hundred-micron level is stable and continuous. Figure 4(a) is a schematic diagram of the cross-shaped water-in-oil droplet generator under an optical microscope, demonstrating the high precision of the ultrafast laser processing technology in this invention. The minimum linewidth in the figure is 50 micrometers. Due to the influence of the spot diameter and heat-affected zone of the femtosecond laser, the minimum linewidth of this invention during a single scan can reach 20 micrometers or less, with a maximum linewidth of 10 micrometers, which is superior to other laser direct writing methods for manufacturing microchannels. (b) shows the generation process of water-in-oil droplets in the cross-shaped water-in-oil droplet generator. (c) shows the generated water-in-oil droplets of different diameters. In this embodiment, the size of the microfluidic droplets generated is 60-300 micrometers, and the uniformity of the generated droplets is good. (d) and (e) show that by controlling the flow rate of water and oil, water-in-oil dispersions with a diameter of 60-300 micrometers can be generated, with stable droplet size and a high number of droplets generated per second, up to 500.
Claims
1. A method for manufacturing a microfluidic chip with controllable wettability via ultrafast laser direct writing, characterized in that, Includes the following steps: Step 1, Preparation of the sample to be processed; Apply a PET film to the surface of the sample to be processed; The sample to be processed is a hydrophobic polymer with methyl groups; Step 2: Laser direct writing scanning etching of microchannels; Using femtosecond lasers, microchannels are scanned and etched on the sample to be processed based on the morphology of the microfluidic chip, while reconstructing the nanostructure on the surface of the microchannels. The pulse width of the femtosecond laser is set to 50fs-200fs, the repetition frequency to 100kHz-200kHz, the single pulse energy to 10μJ-20μJ, and the scanning speed to 200mm / s-500mm / s. Step 3, remove the PET film; Step 4: Microfluidic chip bonding; The sample to be processed is irradiated with oxygen plasma and bonded to the encapsulation material. Then, it is heated and ventilated to obtain a microfluidic chip.
2. The method for manufacturing a microfluidic chip with controllable wettability via ultrafast laser direct writing according to claim 1, characterized in that: In step 2, the scanning interval is 15-20 micrometers, and the scan is performed 10-13 times.
3. The method for manufacturing a microfluidic chip with controllable wettability via ultrafast laser direct writing according to claim 2, characterized in that: In step 1, the thickness of the PET film is 10-50 micrometers.
4. The method for manufacturing a microfluidic chip with controllable wettability via ultrafast laser direct writing according to any one of claims 1-3, characterized in that: In step 2, the pulse width is 200 fs, the repetition frequency is 100 kHz, the single pulse energy is 20 μJ, the scanning speed is 500 mm / s, the scanning interval is 15 micrometers, and the scan is performed 10 times.
5. The method for manufacturing a microfluidic chip with controllable wettability via ultrafast laser direct writing according to claim 4, characterized in that: In step 2, the maximum linewidth of the scanning etching is less than or equal to 20 micrometers.
6. The method for manufacturing a microfluidic chip with controllable wettability via ultrafast laser direct writing according to claim 5, characterized in that: In step 2, the maximum linewidth of the scanning etching is 10 micrometers.