A super-lubricated silicon surface and its preparation method

Abstract

This invention discloses a superlubricated silicon surface and its preparation method in the field of superlubricated surface preparation technology. It aims to solve the problems of complex preparation processes, high costs, and high material requirements in existing technologies. The preparation method includes the following steps: obtaining a silicon substrate with a rough surface using a metal catalytic etching process; hydrophobically modifying the silicon substrate; adding a lubricant dropwise to the modified silicon substrate surface until the rough surface is completely covered by the lubricant; and then tilting the silicon substrate at 10~90° and allowing it to stand, thus obtaining the superlubricated silicon surface. The preparation method of this invention is simple to operate, low in cost, and suitable for large-scale preparation applications.

Description

Technical Field

[0001] This invention relates to a superlubricated silicon surface and its preparation method, belonging to the field of superlubricated surface preparation technology. Background Technology

[0002] Superlubricated surfaces, also known as liquid-infused porous surfaces, are special surfaces developed by researchers inspired by the structure and predation process of pitcher plants in nature. They consist of a rough substrate with specific micro / nano structures and a low-surface-energy lubricant infused onto the substrate. Because of the specific micro / nano structures on the substrate surface, capillary forces can effectively lock the low-surface-energy lubricant onto the substrate surface, thereby forming a continuous, molecular-level, smooth surface with low surface energy on the substrate.

[0003] The physicochemical properties of superlubricated surfaces depend primarily on the properties of the lubricant used. When a liquid immiscible with the lubricant drips onto a superlubricated surface, the liquid quickly slides off, which is the superlubricating property of the surface. Due to its superlubricating properties, superlubricated surfaces can achieve self-cleaning, non-destructive droplet transport, and oil-water separation. Furthermore, they possess significant characteristics such as good stability and self-healing capabilities, thus showing promising application prospects and development potential in fields such as waterproofing, anti-fogging, de-icing, prevention of marine organism adhesion, and corrosion resistance.

[0004] Currently, the main methods for preparing surface-rough silicon substrates with specific micro-nano structures on superlubricated silicon surfaces include photolithography, reactive ion etching, and femtosecond laser etching. These methods involve complex processes, high costs, and have high requirements for the surface and shape of the material, making them unsuitable for large-scale preparation of superlubricated silicon surfaces. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a super-lubricated silicon surface and its preparation method, which is simple and easy to operate, inexpensive to prepare, and suitable for large-scale preparation and application.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] According to a first aspect of the invention, a method for preparing an ultra-lubricated silicon surface includes the following steps:

[0008] A silicon substrate with a rough surface was prepared using a metal catalytic etching process;

[0009] Hydrophobic modification of the silicon substrate;

[0010] Lubricant is dropped onto the modified silicon substrate surface until its rough surface is completely covered by lubricant. The silicon substrate is tilted and left to stand, and excess lubricant is removed from the silicon substrate surface to obtain an ultra-smooth silicon surface.

[0011] The metal catalytic etching process includes:

[0012] The silicon wafers were ultrasonically cleaned by immersing them sequentially in a mixed solution of acetone and ethanol and then in deionized water, and then dried.

[0013] The dried silicon wafer is immersed in an acidic metal catalytic etching solution for etching. After etching, it is immersed in a cleaning solution to remove the metal particles deposited on the surface of the silicon substrate. Then it is rinsed with deionized water and dried to obtain a silicon substrate with a rough surface.

[0014] Furthermore, the acidic metal catalytic etching solution includes catalytic metal ions, an oxidant, hydrofluoric acid, and deionized water; the etching temperature range is 20~60 ℃, and the etching time range is 1~30 min.

[0015] Furthermore, the catalytic metal ion is Cu. 2+ Ag + Au + and Pt + One or more of the following, wherein the oxidizing agent is one or more of hydrogen peroxide, nitric acid and potassium permanganate.

[0016] Furthermore, the concentration range of the catalytic metal ion is 0.01~200 mmol / L, the concentration range of the oxidant is 0.1~5 mol / L, and the concentration range of the hydrofluoric acid is 1~10 mol / L.

[0017] Furthermore, the cleaning solution is one or more of nitric acid solution, aqua regia, ammonia, hydrochloric acid and hydrogen peroxide, with a concentration range of 20~80 wt%, a cleaning temperature of 20~60℃, and a cleaning time of 2~30 min.

[0018] Furthermore, the hydrophobic modification method involves immersing the silicon substrate in a hydrophobic modification solution at a temperature range of 10~60℃ for 1~12 h, followed by washing with deionized water and drying.

[0019] Furthermore, the hydrophobic modification solution comprises a hydrophobic modifier and ethanol, wherein the hydrophobic modifier is one or more of the following silane coupling agents containing hydrophobic long chains: dodecyltrimethoxysilane, octyltriethoxysilane, hexadecyltrimethoxysilane, octadecyltrichlorosilane, heptadecafluorodecyltrimethoxysilane, and tridecafluorooctyltriethoxysilane; and the concentration range of the hydrophobic modification solution is 1~15 mmol / L.

[0020] Furthermore, the drying process is carried out at a temperature range of 30-60°C for 5-30 minutes.

[0021] Furthermore, the tilt angle of the silicon substrate ranges from 10 to 90°, the settling time is from 0.5 to 5 hours, and the lubricant is one or more of silicone oil, perfluorosilicone oil, and perfluoropolyether.

[0022] According to a second aspect of the invention, an ultra-lubricated silicon surface is also provided, which is prepared by any of the above-described preparation methods.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0024] The superlubricating silicon surface prepared by this invention can form a continuous and stable lubricant layer on the silicon substrate surface due to the combined effect of capillary action and van der Waals forces, and has a self-healing function. Due to the low surface energy characteristics of the lubricant, the superlubricating silicon surface prepared by this invention has a small sliding angle and good self-cleaning and anti-icing properties.

[0025] The preparation method provided by this invention can be used to prepare a variety of different micro and nano structures on the surface of silicon substrates. The operation is simple and easy, and the preparation cost is low. It has positive significance for the large-scale preparation and application of superlubricated silicon surfaces in the future. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of a method for preparing an ultra-lubricated silicon surface according to an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of an SEM image of a silicon substrate with a rough surface prepared in Example 1 of the present invention.

[0028] Figure 3 This is a schematic diagram of an SEM image of a silicon substrate with a rough surface prepared in Example 2 of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] For the purposes of this specification and the appended claims, unless otherwise stated, all expressions, percentages, or proportions, and other numerical values ​​used in this specification and the appended claims, are to be understood to be modified by the term "about" in all cases. Furthermore, all scopes disclosed herein include their endpoints and can be combined independently.

[0032] Example 1:

[0033] A method for preparing an ultra-lubricated silicon surface includes the following steps:

[0034] 1. Preparation of silicon substrates with rough surfaces using metal-catalyzed etching process.

[0035] (1) The silicon wafers cut into 25 mm × 25 mm were immersed in a mixture of acetone and ethanol and then in deionized water for ultrasonic cleaning. After that, they were dried with N2, compressed air or other inert gas to remove dirt from the surface of the silicon wafers.

[0036] (2) The cleaned and dried silicon wafer was immersed in an acidic metal catalytic etching solution for etching. The components and concentrations of the acidic metal catalytic etching solution, excluding deionized water, were 1 mmol / L AgNO3, 5 mol / L HF, and 1 mol / L H2O2, respectively. After etching, a nanoporous structure was formed on the surface of the silicon substrate. The etching temperature was 25℃ and the etching time was 5 min.

[0037] (3) The silicon substrate with nanoporous surface structure formed after etching is immersed in HNO3 cleaning solution for cleaning to remove the metal Ag particles deposited on the surface of the silicon substrate; the cleaning solution used in this cleaning process is 69 wt% HNO3 solution, the cleaning temperature is 25℃, and the cleaning time is 10 min; the cleaned silicon substrate is immersed in deionized water for ultrasonic cleaning and dried with N2, compressed air or other inert gas to obtain a silicon substrate with a rough surface.

[0038] 2. Hydrophobic modification of silicon substrates with rough surfaces.

[0039] The silicon substrate with a rough surface from step 1 was immersed in an ethanol solution containing octyltriethoxysilane for hydrophobic modification. The concentration of octyltriethoxysilane in the ethanol solution was 2 mmol / L, the immersion temperature was 20℃, and the immersion time was 3 h.

[0040] The silicon substrate after hydrophobic modification was cleaned with deionized water and dried at 40°C for 30 min to obtain a silicon substrate with a hydrophobic rough surface.

[0041] 3. Lubricant is injected into the modified silicon substrate surface to form a super-slippery surface.

[0042] Silicon oil was dropped onto the surface of the hydrophobically modified silicon substrate until the rough surface of the silicon substrate was completely covered by the silicone oil. Then the covered silicon substrate was tilted at 30° and left for 2 hours. The excess silicone oil on the surface of the silicon substrate was removed to obtain a uniform and completely covered super-smooth silicon surface.

[0043] Example 2:

[0044] 1. Preparation of silicon substrates with rough surfaces using metal-catalyzed etching process.

[0045] (1) The silicon wafers cut into 25 mm × 25 mm were immersed in a mixture of acetone and ethanol and then in deionized water for ultrasonic cleaning, and then dried with N2 to remove dirt from the surface of the silicon wafers.

[0046] (2) The cleaned and dried silicon wafer was immersed in an acidic metal catalytic etching solution for etching. The components and concentrations of the acidic metal catalytic etching solution, excluding deionized water, were 1 mmol / L AgNO3, 60 mmol / L Cu(NO3)2, 5.2 mol / L HF, and 0.9 mol / L H2O2, respectively. After etching, a nanoporous structure was formed on the surface of the silicon substrate. The etching temperature was 25℃ and the etching time was 5 min.

[0047] (3) The silicon substrate with nanoporous surface structure formed after etching is immersed in HNO3 cleaning solution for cleaning to remove the metal Cu particles deposited on the surface of the silicon substrate; the cleaning solution used in this cleaning process is 69 wt% HNO3 solution, the cleaning temperature is 25℃, and the cleaning time is 10 min; the cleaned silicon substrate is immersed in deionized water for ultrasonic cleaning and then dried with N2 to obtain a silicon substrate with a rough surface.

[0048] 2. Hydrophobic modification of silicon substrates with rough surfaces.

[0049] The silicon substrate with a rough surface from step 1 was immersed in an ethanol solution containing octyltriethoxysilane for hydrophobic modification. The concentration of octyltriethoxysilane in the ethanol solution was 2 mmol / L, the immersion temperature was 25℃, and the immersion time was 6 h.

[0050] The silicon substrate after hydrophobic modification was cleaned with deionized water and dried at 40°C for 30 min to obtain a silicon substrate with a hydrophobic rough surface.

[0051] 3. Lubricant is injected into the modified silicon substrate surface to form a super-slippery surface.

[0052] Silicon oil was dropped onto the surface of the hydrophobically modified silicon substrate until the rough surface of the silicon substrate was completely covered by the silicone oil. Then the covered silicon substrate was tilted at 45° and left for 3 hours. The excess silicone oil on the surface of the silicon substrate was removed to obtain a uniform and completely covered super-smooth silicon surface.

[0053] The material properties obtained in Embodiments 1-2 of the present invention will be analyzed below with reference to the accompanying drawings.

[0054] like Figures 2-3 As shown, Figure 2 and Figure 3 These are SEM images of the silicon substrates with rough surfaces prepared in Examples 1 and 2, respectively. As can be seen from the images, the pore size of the silicon substrate is between 50 and 500 nm, indicating that the prepared silicon substrate surfaces all have micro-nano porous structures. Low surface energy lubricants can be effectively locked onto the substrate surface by capillary force, thereby forming a continuous molecular-level low surface energy smooth surface on the substrate.

[0055] Next, contact angle and sliding angle tests were performed on the super-slippery silicon surfaces obtained in Examples 1 and 2.

[0056] Contact angle testing can be used to characterize the wetting ability of a material surface. When a water droplet forms a large contact angle on a material surface, it indicates that the material surface has good hydrophobic properties. When testing the contact angle of a water droplet on a superlubricated silicon surface, the superlubricated silicon sample needs to be placed on a horizontal stage, and ultrapure water is slowly dropped onto the superlubricated silicon surface. After the droplet stabilizes, the contact angle is measured. During the test, it is important to repeat the test and take the average value. The contact angle test results show that the contact angle range of the water droplet on the superlubricated silicon surface in Example 1 is 110~125°, and the contact angle range of the water droplet on the superlubricated silicon surface in Example 2 is 105-120°, indicating that the prepared superlubricated silicon surface has good hydrophobic properties.

[0057] The sliding angle refers to the angle at which a droplet begins to slide on an inclined material surface, and it can be used to characterize the sliding performance of a droplet on a material surface. A small sliding angle indicates that the material surface has good superlubricating properties. When testing the sliding angle of a water droplet on a superlubricated silicon surface, the superlubricated silicon sample is placed on a tiltable horizontal stage. Ultrapure water is slowly dripped onto the superlubricated silicon surface. After the droplet stabilizes, the superlubricated silicon sample is slowly tilted until the droplet begins to slide. The angle at which the superlubricated surface begins to slide is measured. During the test, it is important to repeat the test and take the average value. The sliding angle test results show that the sliding angle of the superlubricated silicon surface in Example 1 is 2-5°, and the sliding angle of the superlubricated silicon surface in Example 2 is 2-4.5°. These test results indicate that water droplets easily slide on the prepared superlubricated surface, indicating that the superlubricated silicon surface has good superlubricating properties.

[0058] In summary, the silicon substrate surface prepared by the method provided by this invention has a variety of different micro-nano porous structures. Therefore, a continuous and stable lubricant layer can be formed on the silicon substrate surface through the combined action of capillary action and van der Waals forces. The operation is simple and low-cost, which is conducive to the large-scale preparation and application of superlubricated silicon surfaces.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an ultra-lubricated silicon surface, characterized in that: Includes the following steps, A silicon substrate with a rough surface was prepared using a metal catalytic etching process; Hydrophobic modification of the silicon substrate; Lubricant is dropped onto the modified silicon substrate surface until its rough surface is completely covered by lubricant. The silicon substrate is tilted and left to stand, and excess lubricant is removed from the silicon substrate surface to obtain an ultra-smooth silicon surface. The metal catalytic etching process includes: The silicon wafers were ultrasonically cleaned by immersing them sequentially in a mixed solution of acetone and ethanol and then in deionized water, and then dried. A dry silicon wafer is immersed in an acidic metal catalytic etching solution for etching. After etching, it is immersed in a cleaning solution to remove metal particles deposited on the surface of the silicon substrate. Then, it is rinsed with deionized water and dried to obtain a silicon substrate with a rough surface. The acidic metal catalytic etching solution includes catalytic metal ions, an oxidant, hydrofluoric acid, and deionized water. The etching temperature range is 20~60 ℃, and the etching time range is 1~30 min.

2. The method for preparing a super-lubricated silicon surface according to claim 1, characterized in that: The catalytic metal ion is Cu. 2+ Ag + Au + and Pt + One or more of the following, wherein the oxidizing agent is one or more of hydrogen peroxide, nitric acid and potassium permanganate.

3. The method for preparing a super-lubricated silicon surface according to claim 1, characterized in that: The concentration range of the catalytic metal ion is 0.01~200 mmol / L, the concentration range of the oxidant is 0.1~5 mol / L, and the concentration range of the hydrofluoric acid is 1~10 mol / L.

4. The method for preparing a super-lubricated silicon surface according to claim 1, characterized in that: The cleaning solution is one or more of nitric acid solution, aqua regia, ammonia, hydrochloric acid and hydrogen peroxide, with a concentration range of 20~80 wt%, a cleaning temperature of 20~60℃, and a cleaning time of 2~30 min.

5. The method for preparing a super-lubricated silicon surface according to claim 1, characterized in that: The method of hydrophobic modification involves immersing the silicon substrate in a hydrophobic modification solution at a temperature range of 10~60℃ for 1~12 h, followed by washing with deionized water and drying.

6. The method for preparing a super-lubricated silicon surface according to claim 5, characterized in that: The hydrophobic modification solution comprises a hydrophobic modifier and ethanol. The hydrophobic modifier is one or more of the following silane coupling agents containing hydrophobic long chains: dodecyltrimethoxysilane, octyltriethoxysilane, hexadecyltrimethoxysilane, octadecyltrichlorosilane, heptadecafluorodecyltrimethoxysilane, and tridecafluorooctyltriethoxysilane. The concentration range of the hydrophobic modification solution is 1~15 mmol / L.

7. The method for preparing a super-lubricated silicon surface according to claim 5, characterized in that: The drying process is carried out at a temperature range of 30~60℃ for 5~30 minutes.

8. The method for preparing a super-lubricated silicon surface according to claim 1, characterized in that: The tilt angle of the silicon substrate ranges from 10 to 90°, and the settling time is from 0.5 to 5 hours. The lubricant is one or more of silicone oil, perfluorosilicone oil, and perfluoropolyether.

9. A super-smooth silicon surface, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8.

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