A high-efficiency micromixer with a coarse-fine interlaced sinusoidal structure and its preparation method

Abstract

This invention discloses a high-efficiency micromixer with an alternating coarse and fine sinusoidal structure and its fabrication method. The micromixer, formed through scribing, etching, plasma treatment, and encapsulation, features microchannels with varying opening widths. These microchannels are sinusoidal in shape, with the upper opening wider than the bottom. The longitudinal cross-sections of the microchannels include V-shaped sections and trapezoidal sections (wider at the top and narrower at the bottom). According to design requirements, the longitudinal cross-sections of the microchannels gradually transition between V-shaped and trapezoidal sections, with corresponding alternating depths, thus creating the alternating coarse and fine sinusoidal structure. The fabrication method of this invention is simple and easy to operate, with low cost. By controlling the formation of amorphous material during the scribing process, the resulting three-dimensional sinusoidal micromixer enhances liquid convection, significantly improving mixing efficiency and effectively enhancing the application performance of microfluidic chips. It can be widely used in the production of microfluidic chips.

Description

Technical Field

[0001] This invention belongs to the field of micro-nano structure fabrication technology, specifically relating to a high-efficiency micromixer with a coarse-fine interlaced sinusoidal structure and its fabrication method. Background Technology

[0002] In recent years, the miniaturization and integration technologies of electronic devices have been continuously improving. Microfluidic chip technology has been widely used in fields such as biology, chemistry, and medicine. As an important component of microfluidic chip analysis systems, micromixers still need further research and development to continuously improve the microchannel structure design in order to enhance their mixing efficiency.

[0003] Due to the extremely small size of microchannels, the Reynolds number of the fluid within them is very low, as indicated by the Reynolds number formula, indicating laminar flow and making it difficult to induce secondary flow to enhance mixing. Currently, common micromixer channel structures include rectangular, serrated, circular, and straight shapes, but these simple structures struggle to significantly improve mixing efficiency. However, improving mixing efficiency is crucial for advancing microfluidic chip technology. For example, accurate detection of viruses and bacteria requires efficient mixing of anticoagulants and chemical reagents; polymerase chain reactions (PCR) necessitate the full reaction of templates, primers, enzymes, and deoxyribonucleotides; and experiments performed on microfluidic chips, such as DNA hybridization, nucleic acid detection, and drug synthesis, also place high demands on micromixer performance. Therefore, designing and fabricating high-performance micromixer channel structures is vital for the development of microfluidic chips across various fields.

[0004] Existing micromixer channel structures are mostly rectangular, serrated, circular, linear, and combinations of various shapes. Reagents can be mixed to a certain extent within the microchannels; however, achieving good mixing results requires a longer channel mixing length or a longer mixing time. Currently, numerous fabrication technologies are emerging for microfluidic chips, commonly including photolithography, 3D printing, and femtosecond laser processing. Among them:

[0005] 1. Photolithography is a chemical processing method that combines photographic reproduction with chemical etching to create precise, fine, and complex thin-layer patterns on the surface of a workpiece. It achieves high processing accuracy and is widely used in chip manufacturing. In forming microchannel structures, photolithography transfers the pattern from a photomask to a silicon wafer coated with photoresist (or photoresist). A series of production steps are then used to remove specific portions of the thin film from the silicon wafer surface. This process also utilizes chemical etching techniques.

[0006] 2. 3D printing is a rapid prototyping technology that prints powdered metal or plastic layer by layer according to a designed structure. It can improve productivity and reduce production costs, and has good repeatability.

[0007] 3. Femtosecond laser is currently the technology that can obtain the shortest pulse under experimental conditions, with an accuracy of ±5 μm.

[0008] Among the aforementioned processing methods, while photolithography offers high processing precision, its high cost makes it unaffordable for most companies. 3D printing boasts advantages such as high efficiency, flexibility, and low cost, and is a mature and widely used technology; however, its limited availability of printing materials is a fatal flaw. Femtosecond laser processing has gained widespread acceptance in recent years, but this technology is not flexible enough, is expensive, and the processed sample surface may exhibit thermal stress, which is detrimental to device performance.

[0009] Therefore, a novel micromixer structure was designed and fabricated to improve the application performance of microfluidic chips. Summary of the Invention

[0010] To address the aforementioned problems, this invention provides a high-efficiency micromixer with a coarse-fine interlaced sinusoidal structure and its preparation method. By rationally designing a three-dimensional sinusoidal microchannel structure, the formation of amorphous material during the scratching process is controlled, thereby controlling selective etching to prepare a high-efficiency three-dimensional sinusoidal micromixer. This method is simple, and the prepared micromixer can enhance liquid convection.

[0011] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0012] A method for preparing a high-efficiency micromixer with a coarse-fine alternating sinusoidal structure, comprising the following steps:

[0013] S1. On the surface of a single crystal silicon coated with silicon nitride, use a needle tip to scribble the inlet and outlet of the channel and the sinusoidal trajectory required by the design. The sinusoidal trajectory is formed by n scratches, and the scribing load should be enough to penetrate the silicon nitride.

[0014] The equation of the sinusoidal trajectory is y=Asin(ωx+φ), where the phase difference between two adjacent scratches is ∆Ф, the width between two adjacent scratches is ∆W, the cumulative phase difference of the sinusoidal channel after etching is Ф = ∆Ф × (n-1), and the total width of the sinusoidal channel is W = ∆W × (n-1). The width of the sinusoidal channel is determined by the spacing between adjacent scratches and the total number of scratches. Here, n is the total number of scratches forming the sinusoidal channel; ∆Ф is the phase difference between adjacent scratches, i.e., the distance of left and right translation; Ф is the phase difference between the top and bottom scratches, which is also the phase difference between the two channel walls after etching; ∆W is the width between adjacent scratches, i.e., the distance of up and down translation; W is the width between the top and bottom scratches, i.e., the width of the channel after etching.

[0015] S2. Immerse the single-crystal silicon etched in step S1 in an etching solution to etch the etched sinusoidal trajectory into a sinusoidal channel of a certain depth. During etching, KOH solution is used as the etching solution, and the etching temperature is 0~100°C. o C (preferred 60) o C), the etching time is 30 min to 10 h.

[0016] S3. Drill holes at the locations where the formed PDMS is aligned with the inlet and outlet of the single crystal silicon with sinusoidal channels etched in step S2, and perform plasma treatment; wherein, the plasma treatment gas is air or oxygen.

[0017] S4. Align the inlet and outlet of the single crystal silicon after plasma treatment in step S3 with the inlet and outlet of the PDMS, and package them into a micro mixer.

[0018] In step S1, the thickness of the silicon nitride deposited on the surface of the single crystal silicon is 2 nm-500 nm.

[0019] The high-efficiency micro mixer with a coarse-fine alternating sinusoidal structure prepared according to the above preparation method has microchannels with different opening widths. The microchannels are sinusoidal in shape as a whole. The upper opening of the microchannel is wider than the bottom width. The longitudinal cross-section of the microchannel includes a V-shaped cross-section and a trapezoidal cross-section that is larger at the top and smaller at the bottom in different regions.

[0020] According to the design requirements, the longitudinal cross-section of the microchannel is gradually alternating between a V-shaped cross-section and a trapezoidal cross-section that is larger at the top and smaller at the bottom according to a sine curve. The depth of the microchannel also gradually alternating according to a sine curve, thus forming a microchannel with an alternating thick and thin sine structure.

[0021] The region where the longitudinal cross-section of the microchannel is V-shaped is the narrow channel region of the microchannel, and the narrowest part of the upper opening width of the microchannel is located in this region.

[0022] The region where the longitudinal cross-section of the microchannel is a trapezoidal cross-section that is larger at the top and smaller at the bottom is the spacious channel region of the microchannel, and the widest part of the upper opening width of the microchannel is located in this region.

[0023] Furthermore, with the peak or trough of the sinusoidal structure as the center, the narrowest part of the upper opening width of the microchannel and the widest part of the upper opening width of the microchannel are located on both sides of the center.

[0024] The beneficial effects of this invention are as follows:

[0025] The preparation method of this invention is simple and easy to implement. During the preparation process, the formation of amorphous material is controlled during the scratching process, thereby controlling selective etching to prepare a high-efficiency three-dimensional sinusoidal micromixer. It is particularly suitable for the field of microfluidic chip fabrication and can manufacture a variety of complex micro-nano channel structures. Through this method, a three-dimensional sinusoidal microchannel structure can be rationally designed and prepared. The resulting micromixer can enhance liquid convection, thereby significantly improving mixing efficiency. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the processing flow of the present invention.

[0027] Figure 2 This is a schematic diagram of the channel structure of the micromixer of the present invention.

[0028] Figure 3 It corresponds Figure 2 A schematic diagram of the longitudinal cross-sectional structure of the channel.

[0029] Figure 4 A schematic diagram of Raman spectroscopy detection of the amorphous layer thickness for a micromixer according to a corresponding embodiment.

[0030] Figure 5 This is a schematic diagram of the performance test of the present invention.

[0031] Figure 6 This is a schematic diagram comparing the test performance indicators of the micro-mixer obtained in the embodiment with those of the YRCSAR channel.

[0032] The attached figures are labeled as follows: 1 microchannel, 2 upper opening of microchannel, 3 bottom of microchannel, 4 V-shaped longitudinal section of microchannel, and 5 trapezoidal longitudinal section of microchannel. Detailed Implementation

[0033] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] like Figure 1 As shown, a single-crystal silicon substrate with a certain thickness of silicon nitride (2 nm-500 nm) was selected as the substrate. KOH was used as the etching solution to fabricate a high-efficiency micromixer with a coarse-fine interlaced sinusoidal structure. The specific steps are as follows:

[0035] S1. Use a needle tip to scribble the inlet and outlet of the microchannel and the designed sinusoidal structure trajectory on the single crystal silicon coated with silicon nitride. The scribing load is 1~100 mN, and the scribing load should be enough to penetrate the silicon nitride.

[0036] S2. Immerse the silicon wafer marked in S1 in KOH solution for etching, etching the marked sinusoidal trajectory into microchannels of a certain depth; the etching temperature is 20~80℃. o C, the optimal temperature is 60 oC; Etching time: 1~6 h.

[0037] S3. The silicon wafer with microchannels etched in S2 is subjected to plasma treatment together with the formed PDMS (holes are drilled where the PDMS is aligned with the inlet and outlet of the silicon wafer); wherein, the plasma treatment gas is air or oxygen, and the power is selected according to the requirements: high power, medium power or low power. In this embodiment, the plasma treatment power is high power > 300 W, and the time is 3 min.

[0038] S4. Align the silicon wafer after plasma treatment in S3 with the PDMS inlet and outlet for encapsulation.

[0039] The high-efficiency micro-mixer with a coarse-fine alternating sinusoidal structure prepared according to the above method has a sinusoidal structure in the microchannel as a whole. The upper opening of the microchannel is wider than the bottom width. The longitudinal cross-section of the microchannel includes a V-shaped cross-section and a trapezoidal cross-section that is larger at the top and smaller at the bottom in different regions. According to the design requirements, the longitudinal cross-section of the microchannel is gradually alternating between the V-shaped cross-section and the trapezoidal cross-section that is larger at the top and smaller at the bottom according to a sinusoidal curve, and the depth of the microchannel also gradually alternating according to a sinusoidal curve, thereby forming a microchannel with a coarse-fine alternating sinusoidal structure.

[0040] The region where the longitudinal cross-section of the microchannel is V-shaped is the narrow channel region of the microchannel, and the narrowest part of the upper opening width of the microchannel is located in this region.

[0041] The region where the longitudinal cross-section of the microchannel is a trapezoidal cross-section that is larger at the top and smaller at the bottom is the spacious channel region of the microchannel, and the widest part of the upper opening width of the microchannel is located in this region.

[0042] Furthermore, with the peak or trough of the sinusoidal structure as the center, the narrowest part of the upper opening width of the microchannel and the widest part of the upper opening width of the microchannel are located on both sides of the center.

[0043] The design requirements in this embodiment result in the following: Figure 2-3 The microchannel structure shown includes:

[0044] (1) When the longitudinal section of the microchannel is a V-shaped section, the upper opening width of the microchannel is greater than 40 μm and less than 50 μm.

[0045] (2) According to the longitudinal section design of the microchannel, when the longitudinal section of the microchannel is a V-shaped section, the depth of the microchannel is greater than 15μm and less than 25μm.

[0046] (3) According to the longitudinal section design of the microchannel described above, when the longitudinal section of the microchannel is a trapezoidal section with a larger upper section and a smaller lower section, the upper opening width of the microchannel is greater than 50μm and less than 80μm.

[0047] (4) According to the longitudinal section design of the microchannel described above, when the longitudinal section of the microchannel is a trapezoidal section with a larger top and a smaller bottom, the bottom width of the microchannel is greater than 5μm and less than 10μm.

[0048] (5) Based on the longitudinal cross-section design of the microchannel described above, when the cross-section of the microchannel is a trapezoidal cross-section with a larger top and a smaller bottom, the depth of the microchannel is greater than 25μm and less than 30μm.

[0049] By using the scribing in step S1 and the sinusoidal trajectory of the scribing, the formation of amorphous material can be effectively controlled. The smaller the spacing between the scribing lines, the thicker the amorphous layer, and the shallower the channel depth after etching. Figure 4 As shown, corresponding Figure 2 , 3 In the diagram, the amorphous layer is thicker at point A and thinner at point C.

[0050] To meet the design requirements, a fully packaged micromixer was obtained, and its mixing performance was tested. The results are as follows: Figure 5 As shown. The corresponding test pairs are as follows. Figure 6 As shown, (a) is a mixing effect diagram of the coarse and fine interlaced sinusoidal channels of the micro mixer obtained in the embodiment, and (b) is a mixing effect diagram of the YRCSAR channel. It can be seen that the channel length of the structure obtained in this embodiment is significantly shortened and the mixing efficiency is significantly improved.

Claims

1. A method for preparing a high-efficiency micromixer with a coarse-fine alternating sinusoidal structure, characterized in that... The steps are as follows: S1. On a single-crystal silicon surface coated with silicon nitride, the inlet and outlet of the channel and the designed sinusoidal trajectory are etched using a diamond needle tip. The etching load is preferably sufficient to penetrate the silicon nitride. The etch consists of n scratches, which, after etching in step S2, form a sinusoidal trajectory. The equation of the sinusoidal trajectory is y = Asin(ωx + φ), where the phase difference between two adjacent scratches is ∆Ф, the width between two adjacent scratches is ∆W, the cumulative phase difference of the sinusoidal channel after etching is Ф = ∆Ф × (n-1), and the total width of the sinusoidal channel is W = ∆W × (n-1); The width of the sinusoidal channel is determined by the spacing between adjacent scratches and the total number of scratches; where n is the total number of scratches forming the sinusoidal channel; ∆Ф is the phase difference between adjacent scratches, i.e., the distance of left and right translation; Ф is the phase difference between the top scratch and the bottom scratch, which is also the phase difference between the two channel walls after etching; ∆W is the width between adjacent scratches, i.e., the distance of up and down translation; W is the width between the top scratch and the bottom scratch, i.e., the width of the channel after etching; S2. Immerse the single crystal silicon after step S1 in the etching solution for etching, and etch the etched sinusoidal trajectory into a sinusoidal channel of a certain depth. During etching, KOH solution was used as the etching solution, the etching temperature was 0~100℃, and the etching time was 30 min~10 h. S3. Drill holes at the locations where the formed PDMS is aligned with the inlet and outlet of the single crystal silicon with sinusoidal channels etched in step S2, and perform plasma treatment. S4. Align the inlet and outlet of the single crystal silicon surface after plasma treatment in step S3 with the inlet and outlet of the PDMS, and package them into a micro mixer.

2. The method for preparing a high-efficiency micromixer with a coarse-fine interlaced sinusoidal structure according to claim 1, characterized in that: In step S1, the thickness of the silicon nitride deposited on the surface of the single crystal silicon is 2 nm-500 nm.

3. The high-efficiency micromixer with a coarse-fine interlaced sinusoidal structure prepared by the method according to claim 1 or 2, characterized in that: The micro mixer has microchannels with varying opening widths. The microchannels are sinusoidal in shape, with the upper opening being wider than the bottom. The longitudinal cross-section of the microchannels varies in different regions, including a V-shaped cross-section and a trapezoidal cross-section that is wider at the top and narrower at the bottom. According to the design requirements, the longitudinal cross-section of the microchannel is gradually alternating between a V-shaped cross-section and a trapezoidal cross-section that is larger at the top and smaller at the bottom according to a sine curve. The depth of the microchannel also gradually alternating according to a sine curve, thus forming a microchannel with an alternating thick and thin sine structure.

4. A high-efficiency micromixer with a coarse-fine alternating sinusoidal structure according to claim 3, characterized in that: The region where the longitudinal cross-section of the microchannel is V-shaped is the narrow channel region of the microchannel, and the narrowest part of the upper opening width of the microchannel is located in this narrow channel region.

5. A high-efficiency micromixer with a coarse-fine alternating sinusoidal structure according to claim 3, characterized in that: The longitudinal cross-section of the microchannel is a trapezoidal region that is larger at the top and smaller at the bottom, which is the spacious channel region of the microchannel. The widest part of the upper opening of the microchannel is located in this spacious channel region.

6. A high-efficiency micromixer with a coarse-fine alternating sinusoidal structure according to claim 3, characterized in that: Centered on the crest or trough of a sinusoidal structure, the narrowest part of the upper opening width of the microchannel and the widest part of the upper opening width of the microchannel are located on opposite sides of the center.

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