Preparation method and application of convex mold for mixed-scale nanofluid chip

Abstract

The present invention discloses a preparation method and application of a convex mold for a mixed-scale nanofluid chip. The processing steps of the method are as follows: first, a single crystal silicon sample is scratched using a micro-nano scratching device, and then placed in a mixed solution of silane and ethanol to allow the silane molecules to be fully adsorbed in the scratching area; then, an etching solution is used to selectively etch the single crystal silicon sample to etch out a silicon convex structure with a micron-level height and a centimeter-level length; then, a micro-nano scratching device is used to scratch the single crystal silicon surface with the silicon convex structure, and then selective etching is performed again to form a convex structure with a nanometer-level height, completing the processing of the mixed-scale nanoconvex mold structure. The present invention uses two scanning probe technologies to realize the integrated processing of a convex mold with mixed-scale characteristics on the surface of a single crystal silicon, and the processing flow is simple and the cost is low, which can improve the production efficiency of the nanofluid chip.

Description

Technical Field

[0001] The present invention relates to the field of micro-nano processing technology, and in particular to a method for preparing a convex mold for a mixed-scale nanofluid chip and its application. Background Art

[0002] Nanofluidics is an emerging science that studies the properties and applications of fluids in and around one-dimensional or multi-dimensional channels with a size of no more than 100 nm. The interaction of surface / interface forces plays an important role in fluid transport in nanochannels, and there are some unique chemical and physical phenomena in nanochannels, such as double layer overlap, ion concentration polarization, and nanofluid rectification. These characteristics promote the application of nanofluidic devices, including diodes and ion field effect transistors, in single molecule analysis, biochemical detection, energy harvesting, and DNA sequencing.

[0003] Nanofluidic devices usually require a network of microfluidic channels as a pathway to guide target molecules into the nanochannels. Nanofluidic chips with mixed-scale features (generally spanning nm to cm scales) are usually prepared using a combination of microfabrication and nanofabrication processes. However, traditional micro / nanofabrication methods for preparing mixed-scale nanofluidic chips, namely photolithography, electron beam / focused ion beam lithography, and nanoimprint lithography, face great challenges in processing cross-scale structures. Therefore, the development of a simple, low-cost integrated method for processing mixed-scale convex molds is crucial for mass production of nanofluidic chips. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned problems and provide a method for preparing and applying a convex mold for a mixed-scale nanofluid chip. The method utilizes scanning probe technology to realize the integrated processing of a convex mold with mixed-scale characteristics on the surface of single-crystal silicon. The processing flow is simple and the cost is low. The prepared convex mold is very suitable for mass production of nanofluid chips.

[0005] To achieve the above object, the present invention adopts the following technical solution:

[0006] The preparation method of the convex mold for the mixed-scale nanofluid chip has the following processing steps:

[0007] S1. Using a micro-nano scribing device, a first scribing process is performed on the surface of a clean single crystal silicon sample according to a predetermined trajectory;

[0008] S2, soaking the single crystal silicon sample after the first scratching in step S1 in a mixed solution, so that the silane molecules are fully adsorbed on the scratching area, so as to improve the etching resistance of the scratching area; the mixed solution is a mixture of silane and ethanol, or a mixture of siloxane and ethanol; the soaking time is 1-3 hours;

[0009] S3, selectively etching the single crystal silicon sample processed in step S2 using an etching solution, thereby etching a silicon convex structure with a micrometer-level height and a centimeter-level length;

[0010] S4, using a second micro-nano scratching device to scratch the single crystal silicon surface with the silicon convex structure in step S3 for a second time, forming nanoscale scratches on the single crystal silicon surface, wherein the nanoscale scratches are continuous structures;

[0011] S5. Immerse the single crystal silicon sample obtained in step S4 again in an etching solution for selective etching, thereby forming a convex structure with a nanometer height, thereby completing the integrated processing of the mixed-scale convex mold structure.

[0012] In step S1, the contact pressure used by the micro-nano scribing device during scribing is 11-20 GPa, and the speed is 0.1-1 mm / s.

[0013] In step S2, the silane or siloxane may be 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS), octadecyltrichlorosilane (OTS) or polydimethylsiloxane (PDMS), etc., which are used to enhance the wet etching mask capability.

[0014] In step S3, the etching solution is a potassium hydroxide solution (mass concentration is 20%) or a tetramethylammonium hydroxide solution (mass concentration is 25%); and the etching solution in step S5 is a potassium hydroxide solution (mass concentration is 20%).

[0015] In step S4, the contact pressure used by the second micro-nano scratching device for the second scratching is 11-13 GPa and the speed is 1-100 μm / s, the purpose of which is to form nano-scale scratches.

[0016] Furthermore, the curvature radius of the micro-nano scribing device one is greater than that of the micro-nano scribing device two.

[0017] Furthermore, the micro-nano scribing device 1 and the micro-nano scribing device 2 use different diamond probes, wherein the curvature radius of the diamond probe 1 used as the micro-nano scribing device 1 is micrometer level, and the curvature radius of the diamond probe 2 used as the micro-nano scribing device 2 is 20-50 nm.

[0018] Furthermore, in step S3, the etching time is 25-35 minutes, and the temperature of the etching solution is 40-50°C.

[0019] Furthermore, in step S5, the etching time is 2-4 min, and the temperature of the etching solution is 22-28°C.

[0020] Furthermore, in combination with nanotransfer technology, the mixed-scale convex mold structure obtained in step S5 can be transferred to the surface of materials such as polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA), thereby realizing mass production of mixed-scale nanofluidic chips.

[0021] The beneficial effects of the present invention are as follows:

[0022] The present invention utilizes a mixed solution of silane and ethanol to allow silane to be fully adsorbed on the scribing area, thereby improving its ability to resist etching, and can better selectively etch out preliminary mixed-scale features of centimeter-level length and micrometer-level height; during the second selective etching, a convex structure of nanometer-level height is obtained; during this period, two scanning probe technologies are used to perform different-scale scribing, thereby obtaining a convex mold structure with mixed-scale features of centimeter-level length, micrometer-level height and nanometer-level width; overall, the present invention realizes the integrated processing of convex molds with mixed-scale features on the surface of single-crystal silicon, and has a simple process and low cost, and is very suitable for nanofluid chip production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a processing flow diagram of the present invention.

[0024] Figure 2 The present invention is a schematic diagram of a physical object for machining a convex mold with mixed-scale features. DETAILED DESCRIPTION

[0025] The present invention is described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0026] Example 1

[0027] like Figure 1 As shown, in this embodiment, the method for preparing a convex mold for a mixed-scale nanofluidic chip includes the following steps:

[0028] S1. Using a micro-nano scribing device, a clean single-crystal silicon surface is scribed according to a predetermined trajectory, and the scribing motion trajectory is performed in a surface scanning mode to expose the single-crystal silicon substrate in the scribing area;

[0029] The curvature radius of the selected micro-nano scratching device is about 10 μm, and the scratching load is 20-50 mN.

[0030] S2. Place the single crystal silicon sample after the first scribing in a mixed solution of 1H,1H,2H,2H-perfluorodecyltriethoxysilane and ethanol (super pure) and soak for 2 hours to allow the silane molecules to be fully adsorbed in the scribing area, thereby improving the masking ability of the scribing area.

[0031] S3. Selectively etching the single crystal silicon sample processed in step S2 with a potassium hydroxide solution, thereby etching out a silicon convex structure with a micrometer-level height and a centimeter-level length; the selected etching time is about 30 minutes, and the etchant temperature is maintained at 40°C.

[0032] S4. On a scanning probe microscope or a scratch tester, use a micro-nano scratching device to scratch the single crystal silicon surface with the silicon convex structure in step S3.

[0033] S5. Immerse the single crystal silicon sample obtained in step S4 in a potassium hydroxide solution again for selective etching. The selected etching time is 3 min, and the etchant temperature is maintained at 26°C, thereby forming a convex structure with a nanometer height, thereby completing the integrated processing of the mixed-scale convex mold structure.

[0034] Example 2

[0035] In this embodiment, the method for preparing a convex mold for a mixed-scale nanofluidic chip comprises the following steps:

[0036] S1. Using a micro-nano scribing device, scribing is performed on a clean single crystal silicon (100) surface according to a predetermined trajectory, wherein the scribing motion trajectory is performed in a surface scanning mode to expose the single crystal silicon substrate in the scribing area;

[0037] The contact pressure used by the micro-nano scribing device during scribing is 11-17 GPa, and the speed is 0.1-1 mm / s.

[0038] S2, placing the single crystal silicon sample after the first scribing in a mixed solution of octadecyltrichlorosilane (OTS) and ethanol for 1.5 hours, so that the silane molecules are fully adsorbed on the scribing area, thereby improving the masking ability of the scribing area;

[0039] S3, selectively etching the single crystal silicon sample processed in step S2 using a tetramethylammonium hydroxide solution, thereby etching a silicon convex structure with a micrometer-level height and a centimeter-level length; the selected etching time is about 33 minutes, and the etchant temperature is maintained at 45-50° C.;

[0040] S4, using a micro-nano scratching device to scratch the single crystal silicon surface with the silicon convex structure in step S3 on a scanning probe microscope or a scratch tester;

[0041] S5. Immerse the single crystal silicon sample obtained in step S4 in a potassium hydroxide solution again for selective etching to form a convex structure with a nanometer height. The selected etching time is 2 min, and the etchant temperature is maintained at 22°C, thereby completing the integrated processing of the mixed-scale convex mold structure.

[0042] Example 3

[0043] In this embodiment, the method for preparing a convex mold for a mixed-scale nanofluidic chip comprises the following steps:

[0044] S1. Using a micro-nano scribing device, scribing is performed on a clean single crystal silicon (100) surface according to a predetermined trajectory, wherein the scribing motion trajectory is performed in a surface scanning mode to expose the single crystal silicon substrate in the scribing area;

[0045] The contact pressure used by the micro-nano scribing device during scribing is 16-20 GPa, and the speed is 0.1-1 mm / s.

[0046] S2, placing the single crystal silicon sample after the first scribing in a mixed solution of polydimethylsiloxane (PDMS) and ethanol and soaking for 2 hours, so that the silane molecules are fully adsorbed on the scribing area, thereby improving the masking ability of the scribing area;

[0047] S3, selectively etching the single crystal silicon sample processed in step S2 with a potassium hydroxide solution, thereby etching a silicon convex structure with a micrometer-level height and a centimeter-level length; the selected etching time is about 25 minutes, and the etchant temperature is maintained at 48° C.;

[0048] S4, using a micro-nano scratching device to scratch the single crystal silicon surface with the silicon convex structure in step S3 on a scanning probe microscope or a scratch tester;

[0049] S5. Immerse the single crystal silicon sample obtained in step S4 in a potassium hydroxide solution again for selective etching to form a convex structure with a nanometer height. The selected etching time is 3 minutes, and the etchant temperature is maintained at 28°C, thereby completing the integrated processing of the mixed-scale convex mold structure.

[0050] Example 4

[0051] For any of the above embodiments 1-3, the curvature radius of the micro-nano scribing device 1 is greater than that of the micro-nano scribing device 2.

[0052] Wherein, the micro-nano scratching device 1 and the micro-nano scratching device 2 use diamond probes with different radii.

[0053] Specifically, the curvature radius of diamond probe 1 used as micro-nano scribing device 1 is 8-12 μm, and the curvature radius of diamond probe 2 used as micro-nano scribing device 2 is 20-50 nm.

[0054] The mixed scale nanofluid chip convex mold prepared by any of the above embodiments is as follows: Figure 2 shown.

[0055] Furthermore, in combination with nanotransfer technology, the mixed-scale convex mold structure obtained in step S5 can be transferred to the surface of materials such as polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA), thereby realizing mass production of mixed-scale nanofluidic chips.

Claims

1. A method for preparing a convex mold for a mixed-scale nanofluid chip, characterized in that: The processing steps are as follows: S1. Using a micro-nano scribing device, a first scribing process is performed on the surface of a clean single-crystal silicon sample according to a predetermined trajectory to expose the single-crystal silicon substrate in the scribing area; the contact pressure used by the micro-nano scribing device during scribing is 11-20 GPa; S2, soaking the single crystal silicon sample after the first scratching in step S1 in a mixed solution, so that the silane molecules are fully adsorbed on the scratching area, so as to improve the etching resistance of the scratching area; the mixed solution is a mixture of silane and ethanol, or a mixture of siloxane and ethanol; The soaking time is 1-3h; S3, selectively etching the single crystal silicon sample processed in step S2 using an etching solution, thereby etching a silicon convex structure with a micrometer-level height and a centimeter-level length; S4, using a second micro-nano scribing device to scribble the single crystal silicon surface having the silicon convex structure in step S3 for a second time, forming nanoscale scratches on the single crystal silicon surface; the contact pressure used by the second micro-nano scribing device for scribing is 11-13 GPa, and the speed is 1-100 μm / s; S5, immersing the single crystal silicon sample obtained in step S4 again in an etching solution for selective etching to form a convex structure with a nanometer-level height; Among them, the curvature radius of the micro-nano scratching device one is greater than that of the micro-nano scratching device two; the micro-nano scratching device one uses a diamond probe one with a curvature radius of micrometer level; the micro-nano scratching device two uses a diamond probe two with a curvature radius of 20-50 nm.

2. The method for preparing a convex mold for a mixed-scale nanofluid chip according to claim 1, characterized in that: In step S2, the silane or siloxane used is: 1H,1H,2H,2H-perfluorodecyltriethoxysilane, octadecyltrichlorosilane or polydimethylsiloxane.

3. The method for preparing a convex mold for a mixed-scale nanofluid chip according to claim 1, characterized in that: The etching solution in step S3 is a potassium hydroxide solution with a mass concentration of 20% or a tetramethylammonium hydroxide solution with a mass concentration of 25%; the etching solution in step S5 is a potassium hydroxide solution with a mass concentration of 20%.

4. The method for preparing a convex mold for a mixed-scale nanofluid chip according to claim 1, characterized in that: In the step S3, the etching time is 25-35 min, and the temperature of the etching solution is 40-50°C.

5. The method for preparing a convex mold for a mixed-scale nanofluid chip according to claim 1, characterized in that: In the step S5, the etching time is 2-4 min, and the temperature of the etching solution is 22-28°C.

6. Application of the convex mold prepared by the method for preparing the convex mold for a mixed-scale nanofluid chip according to claim 1, characterized in that: The mixed-scale convex mold structure obtained in step S5 is transferred to the surface of polydimethylsiloxane or polymethyl methacrylate using nanotransfer technology to manufacture a mixed-scale nanofluid chip.

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