CN106185792A - A kind of population parameter controllable method for preparing of super-hydrophobic micro-nano compound structure - Google Patents

Abstract

The invention discloses a full-parameter controllable preparation method of a superhydrophobic micro-nano composite structure, which belongs to the technical field of micro-nano structure preparation. The method is to combine the preparation of microstructure and nanostructure, through layered preparation, that is, to realize the preparation of microstructure by photolithography, and to realize the preparation of nanostructure by colloidal soft etching and bulk silicon etching. The composite of micron and nanostructure is achieved by It is realized by compounding the nano-microsphere mask and the microstructure array. This method provides a research basis for the scientific research and engineering practice of micro-nano-structured superhydrophobic surfaces, effectively links the macroscopic phenomena and microstructures of material surfaces, and provides a basis for quantitative and qualitative exploration of the physical and chemical properties of superhydrophobic surfaces. . The method combines colloidal soft etching and bulk silicon etching, has strong process controllability, simple operation, low cost and high processing precision.

Description

A full-parameter controllable preparation method of superhydrophobic micro-nano composite structure

technical field

The invention belongs to the technical field of micro-nano structure preparation, and in particular relates to a full-parameter controllable preparation method of a super-hydrophobic micro-nano composite structure.

Background technique

Superhydrophobic is a special wetting state on the surface of materials, which is widely used in scientific research and industrial production. A superhydrophobic surface refers to a surface with a static contact angle of water droplets θ ≥ 150°. This physical property of water droplets and the surface repelling each other leads to a reduction in the contact area between the water droplet and the surface, and the water droplet is in a suspended state on the surface. Due to the superior characteristics of the superhydrophobic surface, it plays an important role in anti-fog, anti-icing, anti-snow, self-cleaning, drag reduction, desorption, corrosion resistance and oxidation resistance, etc., and has high potential application value.

Surface wetting properties are mainly determined by surface free energy and surface microscopic topography. Y T Cheng (Nanotechnology, 17(5), 1359-1362) found that the surface of the lotus leaf is a double-layer micro-nano composite structure when studying the superhydrophobicity of the lotus leaf surface. Micro-protrusions of 1-20 μm and nano-protrusion structures with an average diameter of 200 nm, and the surface is composed of a layer of wax with a bottom surface energy [Chem. The synergistic effect is the key factor for superhydrophobic properties. Therefore, constructing micro-nano structures and surface treatment has become a way to prepare super-hydrophobic surfaces.

At present, the preparation methods of superhydrophobic surface include chemical vapor deposition, electrochemistry, template method, sol-gel method, hydrothermal method, photolithography, femtosecond laser, etc. These methods are to construct micro-nano structures on different substrates, and The surface is modified with low surface energy substances to achieve superhydrophobicity. However, electrochemical, sol-gel, and hydrothermal methods all use chemical reactions to form messy micro-nano composite structures on the substrate, which cannot achieve full-parameter controllable preparation of micro-nano structures; The fluorinated film on the surface realizes superhydrophobicity. This kind of superhydrophobic surface prepared only by constructing a low-energy surface often has poor stability, short life, low binding force with the substrate, and is easily damaged; for femtosecond laser processing, it can be The controllable preparation of precise dimensions is achieved, but due to thermal effects, melting, burrs and cracks, and the need for expensive processing equipment, femtosecond laser processing is limited. Photolithography is a common method to realize the preparation of microstructures. However, the current photolithography mask can only realize the preparation of submicron and micron-scale structures. The preparation still needs to be explored.

Microscopic morphology determines macroscopic phenomena, and the controllable preparation of all parameters of micro-nano structures is realized, which provides a basis for quantitative and qualitative analysis of macroscopic phenomena. In the study of material surface wetting theory, the change of microscopic size parameters, the impact on the duty ratio of the surface morphology of the material, the impact on the size of the air pocket between the microstructure and the water droplet, and the secondary structure of the micro-nano composite structure. The impact of synergy, etc., requires quantitative and qualitative scientific research. However, at this stage, there is a lack of methods for the full parameter controllable preparation of micro-nano structures, which makes it impossible to explore its mechanism; in engineering applications, the use of micro-nano structures In the engineering practice of anti-icing on hydrophobic surfaces, it is also very important to explore the change of micro-nano structural parameters, the influence of supercooled water droplets on the substrate surface adhesion, heat transfer, and nucleation; in the field of micro-nano optics research, micro-nano The change of the size parameter of the nanostructure has a significant impact on the electromagnetic field enhancement effect and Raman effect of light on the surface of the micro-nanostructure.

In summary, there are many methods for preparing micro-nano structures, but none of these methods can realize the controllable preparation of all parameters of micro-nano composite structures, especially the controllable preparation of size-tunable nanostructures on micron structures. . However, the controllable preparation of full parameters of micro-nano structures has great significance for scientific research and engineering applications. Therefore, there is an urgent need to develop a simple, convenient and controllable preparation method.

Starting from the microelectromechanical (MEMS) lithography technology, combined with the method of colloidal soft etching, we first assembled the nano-microspheres into a single-layer dense nano-mask through self-assembly. Then combine a single-layer dense nanomask with a silicon substrate with a micron structure, perform soft etching on the nanospheres by RIE (oxygen plasma etching), adjust the diameter and spacing of the nanospheres, and then etch silicon through bulk silicon Substrate, the micro-nano composite structure is prepared by removing the nano-microspheres, and finally modified with fluorosilane to obtain a super-hydrophobic surface with superior properties.

Contents of the invention

The purpose of the present invention is to provide a method for the controllable preparation of silicon-based superhydrophobic micro-nano structure with full parameters. The method can precisely control the second-order fully parameter-adjustable preparation of microstructures, nanostructures and micro-nano composites.

The key point of the invention is to combine the nano mask with the micro structure array and the full parameter controllable preparation of the nano structure. The microstructure can be prepared with full parameter controllability of length, width, height and array gap through traditional photolithography technology. However, in order to compound nanostructures on microstructures, it is necessary to combine nanomasks with microstructure arrays, and then apply colloidal soft etching and bulk silicon etching to achieve full-parameter controllable preparation of nanostructures.

Technical scheme of the present invention is as follows:

A silicon-based superhydrophobic micro-nano structure with full parameter controllable preparation is a combination of micro-structure and nano-structure preparation, through layered preparation, that is, through photolithography to achieve micro-structure preparation, through colloidal soft etching and bulk silicon etching To realize the preparation of nanostructures, the compounding of micron and nanostructures is achieved through the compounding of nanosphere masks and microstructure arrays.

A method for fully parameter-controllable preparation of a silicon-based superhydrophobic micro-nano structure, characterized in that it comprises the following steps:

Step 1: Preparation of silicon-based micro-array structure: Using mature photolithography technology, through mask preparation, glue coating, exposure, development, and ICP etching, a micro-structure array with a preset size can be prepared. The micron structure is a square microcolumn, the side length of which is a = 5-20 μm, the height h = 10-60 μm, and the spacing b = 10-120 μm;

Step 2: the preparation of nanomask; This process comprises following four substeps:

Sub-step 1: configuring a monodisperse nanosphere suspension;

Sub-step 2: Treat another hydrophobic substrate with oxygen plasma to make its surface hydrophilic, spin-coat the nanosphere suspension on the substrate, and form a veined single-layer nanosphere film on the substrate;

Sub-step 3: Peel off the vein-shaped single-layer nano-microsphere film: first leave the substrate of the vein-shaped single-layer nano-microsphere film spin-coated in sub-step 2 to restore it to hydrophobicity; then spin-coat the vein-shaped single-layer nano-microsphere film The substrate of the single-layer nano-microsphere film is slowly immersed in the liquid from top to bottom, and the liquid is preferably deionized water; the vein-shaped single-layer nano-microsphere film is peeled off from the substrate and suspended on the liquid surface;

Sub-step 4: Add surfactant dropwise on the liquid surface, push and push the vein-shaped single-layer nano-microsphere film to form a dense single-layer film, and complete the secondary assembly of the air-liquid interface;

Step 3: Recombining the nanomask with the micro-array structure: on the basis of sub-step 4 of step 2, lower the liquid level, and transfer the dense monolayer film to the surface of the silicon-based micro-array structure described in step 1;

Step 4: Colloidal soft etching, adjusting the distance and radius of the nanomask;

The compounding of the dense nano-microsphere mask and the micro-structure array is realized through steps two and three. Since the spacing of the nano-column array is determined by the original diameter of the nano-microsphere, the diameter of the nano-column is determined by the nanometer diameter after etching. Therefore, we etched the diameter of the closely arranged nano-microspheres through colloidal soft etching. In this way, the size of the nano-array structure can be adjusted. This step can realize the range of nano-mask diameter d=200-800nm and height h1=3μm-200nm;

Step 5: Full parameter controllable preparation of silicon-based nanostructures; this step uses metal-assisted etching to etch the silicon substrate, which is divided into two sub-steps;

Sub-step 1: Evaporate silver on the surface of the silicon base. After step 4, the diameter of the densely arranged single-layer nanospheres becomes smaller, and gaps appear between the nanospheres. Then, silver is deposited between the nanospheres by evaporating silver. Layer, using the principle of the original battery to etch the silicon base, but it should be noted that the thickness of the evaporated silver layer must not exceed the radius of the nanosphere after soft etching;

Sub-step 2: preparation of metal-assisted etching solution, a layer of silver has been evaporated between the nano-microspheres through sub-step 1, and the treated silicon substrate is etched in a mixed solution of HF and H ₂ O ₂ ;

Sub-step 3: put the silicon substrate obtained in step 4 in a drying oven for heating treatment to increase the adhesion between the nanospheres and the silicon substrate; then put it into the solution prepared in sub-step 2 for reaction. By controlling the reaction time, the depth of nano-columns can be controlled;

Sub-step 4: Soak the etched silicon substrate in tetrahydrofuran to remove the nano-microspheres;

Step 6: Fluorosilane modifies the silicon-based micro-nano composite structure to prepare a super-hydrophobic surface.

Beneficial effects of the present invention:

The present invention proposes a full-parameter controllable preparation method of a micro-nano composite structure for the first time, especially a full-scale controllable preparation of a nanostructure compounded on a micron structure. The research basis is established, and the macroscopic phenomenon and microstructure of the material surface are effectively connected, which provides a basis for quantitative and qualitative exploration of the physical and chemical properties of the superhydrophobic surface. The method combines colloidal soft etching and bulk silicon etching, has strong process controllability, simple operation, low cost and high processing precision.

Description of drawings

Figure 1 shows a schematic diagram of a silicon-based microstructure array;

Figure 2 shows a monolayer dense nano-mask overall optical microscope image;

Figure 3 shows a partial scanning electron microscope image of a single-layer dense nanosphere;

Figure 4 shows a composite optical microscope image of a nanomask and a microstructure array;

Figure 5 shows a microscopic view of the reduced diameter of the nanosphere mask after colloidal soft etching;

Figure 6 shows a scanning electron micrograph of the micro-nano composite structure;

Figure 7 shows a scanning electron microscope microscopic view of a single micro-nano composite structure;

Figure 8 shows the measurement of the static contact angle of the silicon-based micro-nano superhydrophobic surface.

detailed description

The present invention will be further described in detail below through specific examples.

Example 1

The super-hydrophobic micro-nano composite structure in this implementation case is: a silicon-based super-hydrophobic micro-nano composite structure. There are micron-scale square pillar arrays on the surface of the silicon substrate, and there are nano-micro-pillar arrays on the top of the square pillars and the end of the silicon base. The side length of the micron square column structure is a = 10 μm, the height h ₁ = 20 μm, and the distance between two adjacent micron structures is b = 20 μm; the size of the composite nanostructure on the micron structure: diameter d = 600 nm, height h ₂ = 1.5 μm, distance L = 900nm.

In this implementation case, the controllable preparation of superhydrophobic micro-nano composite structures with pre-designed dimensions includes the following steps:

Step 1: Preparation of the silicon-based micro-array structure: first, a photolithography mask is designed so that the size parameter of the micro-array structure is a=10 μm, and the spacing b=20 μm. Then, the pattern is transferred to the photoresist by photolithography, and then the silicon substrate is etched by inductively coupled plasma reactive etching (ICP), and the etching depth h ₁ =20 μm; the etching process parameters used are: radio frequency Power RF=100w, pressure 20pa; SF ₆ , gas flow rate 100 sccm/min, etching time 12s; C ₄ F ₆ , gas flow rate 80 sccm/min, passivation time 9s; etching/passivation cycle times 16 times; After etching, the photoresist was removed with acetone, rinsed with deionized water, and dried with nitrogen gas to obtain a micron structure array with a preset size, as shown in FIG. 1 .

Step 2: the preparation of nanomask; This process comprises following four substeps:

Sub-step 1: preparing a monodisperse nanosphere suspension; in this embodiment, polystyrene nanospheres with a diameter of 900 nm are used.

Sub-step 2: Treat another hydrophobic substrate with oxygen plasma to make its surface hydrophilic, spin-coat the nanosphere suspension on the substrate, and form a veined single-layer nanosphere film on the substrate;

Sub-step 3: Peel off the vein-shaped single-layer nano-microsphere film: first leave the substrate of the vein-shaped single-layer nano-microsphere film spin-coated in sub-step 2 to restore it to hydrophobicity; then spin-coat the vein-shaped single-layer nano-microsphere film The substrate of the single-layer nano-microsphere film is slowly immersed in the liquid from top to bottom, and the liquid is deionized water; the vein-shaped single-layer nano-microsphere film is peeled off from the substrate and suspended on the liquid surface;

Sub-step 4: Add a surfactant dropwise on the liquid surface, push and push the venation-shaped single-layer nano-microsphere film to assemble a dense single-layer film, and complete the secondary assembly of the gas-liquid interface. The single-layer dense nano-microsphere film is optically macroscopically observed The figure is shown in Figure 2, and the microscopic view of the scanning electron microscope is shown in Figure 3

Step 3: Recombination of the nanomask and the micron array structure: on the basis of substep 4 of step 2, the liquid level is lowered, and the dense monolayer film is transferred to the surface of the silicon-based micron array structure described in step 1, as shown in the figure 4 shows the composite optical microscope picture of nanomask and microstructure array.

Step 4: Colloidal soft etching, adjusting the distance and radius of the nanomask;

The compounding of the dense nano-microsphere mask and the micro-structure array is realized through steps two and three. Since the spacing of the nano-column array is determined by the original diameter of the nano-microsphere, the diameter of the nano-column is determined by the nanometer diameter after etching. Therefore, we etched the diameter of the closely arranged nano-microspheres through colloidal soft etching. In this way, the size of the nano-array structure can be adjusted, and this step can realize the range of nano-mask diameter d=200-800nm and height h1=3μm-200nm.

In the present embodiment, the application of oxygen plasma etching (RIE) to carry out soft etching of nano-microspheres specific process parameters are as follows: O ₂ gas flow 100sccm/min, CF4 gas flow 9.0sccm/min chamber pressure: 26pa, gas radio frequency The power is 100w, the etching time is 30s~120s, and the main working gas is O ₂ . The etching time determines the final diameter of the nanospheres. As shown in Figure 5, the diameter of the densely arranged nanospheres becomes smaller. There is a gap between them, which realizes the regulation of the size of the nanomask.

Step 5: full-parameter controllable preparation of silicon-based nanostructures; this step uses metal-assisted etching to etch the silicon substrate, which is divided into two sub-steps.

Sub-step 1: Evaporate silver on the surface of the silicon base. After step 4, the diameter of the densely arranged single-layer nanospheres becomes smaller, and gaps appear between the nanospheres. Then, silver is deposited between the nanospheres by evaporating silver. layer, the silicon base is etched using the principle of a galvanic cell, and in this embodiment, the thickness of the silver layer is h ₃ =40nm.

The specific process of evaporating silver on the surface of the silicon substrate is as follows: the degree of vacuum is 1.5×10 ^-4 Pa, the temperature of the evaporation source is 1100°C, and the target is silver.

Sub-step 2: preparation of metal-assisted etching solution, through sub-step 1, a layer of silver has been evaporated between the nano-microspheres, and the treated silicon substrate is etched in a mixed solution of HF and H ₂ O ₂ , Specific etching solution preparation parameters are as follows: Take 18ml of HF (mass fraction 39%) solution for experiment, 5ml H ₂ O ₂ (mass fraction 60%) solution, 77ml deionized water, and mix them evenly.

Sub-step 3: heat the silicon substrate obtained in step 4 in a drying oven to increase the adhesion between the nanospheres and the silicon substrate. Specific operation: treat in step 4 at 60° C. for 1 hour. Then put it into the solution prepared in sub-step 2 for reaction. In this example, the silver-plated silicon substrate was placed in the metal-assisted etching solution for 8 minutes to react, and a nano-column array with a height of 1.5 μm was obtained.

Sub-step 4: Soak the etched silicon substrate in tetrahydrofuran for 1 hour, remove the nano-microspheres, and obtain a micro-nano composite structure as shown in FIG. 6 .

Step 6: Fluorosilane modification of the silicon-based micro-nano composite structure to prepare a surface with superior super-hydrophobic properties: put the prepared silicon-based micro-nano composite structure in a vacuum box, vacuumize for 5-15 minutes, and pass in nitrogen gas to wait for the pressure After stabilization, uncover the vacuum box, add 2-3ml of fluorosilane dropwise to the petri dish near the silicon-based micro-nano composite structure, cover the lid, and then vacuumize again. After the vacuum degree is stable, let it stand for 2-4 hours to obtain the The silicon-based micro-nano composite structure with superhydrophobic properties required in the embodiment, the static contact angle on the surface of the micro-nano composite structure is greater than 150° after testing, showing excellent superhydrophobicity, as shown in FIG. 8 .

Claims (2)

1. the method for the silica-based super-hydrophobic controlled preparation of micro-nano structure population parameter, it is characterised in that comprise the steps:

Step one: the preparation of silica-based micrometre array structure, described micrometer structure is square microtrabeculae, its square column length of side a=5～20 μ M, highly h=10～60 μm, spacing b=10～120 μm；

Step 2: the preparation of nanometer mask；This process includes following four sub-steps:

Sub-step one: the Nano microsphere suspension of configuration monodisperse system；

Sub-step two: by another hydrophobic substrate of oxygen plasma treatment so that it is surface hydrophilic, Nano microsphere suspension is spun on In this substrate, form venation shape monolayer Nano microsphere thin film on the substrate；

Sub-step three: peel off venation shape monolayer Nano microsphere thin film: first stand the venation shape monolayer in sub-step two there being spin coating The substrate of Nano microsphere thin film so that it is be recovered to hydrophobicity；Then being somebody's turn to do of venation shape monolayer Nano microsphere thin film spin coating being had Substrate is immersed in liquid the most from top to bottom；Described venation shape monolayer Nano microsphere thin film is peeled off from this substrate and is suspended in liquid Face；

Sub-step four: drip surfactant at liquid level, the crowded venation shape monolayer Nano microsphere thin film that pushes away is assembled into fine and close single thin layer Film, completes liquid-vapor interface secondary and assembles；

Step 3: nanometer mask and micrometre array structure composite: on the basis of the sub-step four of step 2, reduces liquid level, by institute State fine and close single thin film to transfer on the silica-based micrometre array body structure surface described in step one；

Step 4: colloid Soft lithograph, regulation nanometer mask spacing and radius, it is achieved nanometer mask diameter d=200～800nm are high Degree h1=3 μm～200nm range；

Step 5: the controlled preparation of silicon-based nano structure population parameter, this step uses metal auxiliary etch method etching silicon base, is divided into Two sub-steps；

Sub-step one: silicon substrate surface evaporation silver, described evaporation silver thickness is less than the radius of Nano microsphere after Soft lithograph；

Sub-step two: the silicon base handled well is placed on HF and H₂O₂Mixed solution performs etching；

Sub-step three: obtained for step 4 silicon base be placed in drying baker and carry out heat treatment, is then placed in sub-step two and is joined In solution, react, control the degree of depth of nanopillars by controlling the response time；

Sub-step four: the silicon base after etching is placed in oxolane immersion and removes Nano microsphere；

Step 6: silicon fluoride modifies silica-based micro-nano compound structure, prepares ultra-hydrophobicity surface.

2. the method for the silica-based super-hydrophobic controlled preparation of micro-nano structure population parameter as claimed in claim 1, it is characterised in that In the sub-step three of described step 2, the venation shape monolayer Nano microsphere film substrate liquid slowly that described immersion spin coating has is Deionized water.