A method for preparing nanostructures on a flexible substrate

Abstract

A method for preparing a nanostructure on a flexible substrate comprises the following steps: preparing a PDMA flexible substrate; preparing a hexagonally closely packed polystyrene ball array on the PDMA flexible substrate to obtain a polystyrene ball array on the flexible substrate; preparing a PVA hydrosol; spin coating the PVA hydrosol on the polystyrene ball array on the flexible substrate to cover the surface of the polystyrene ball array with the PVA glue; etching the PVA glue covering the surface of the polystyrene ball array by plasma cleaning to reduce the thickness of the PVA glue layer on the surface of the polystyrene ball array so that the polystyrene balls are not completely covered by the PVA glue; depositing silver and silicon dioxide on the surface of the polystyrene ball array treated with the etched PVA glue by magnetron sputtering; and performing a surface chemical treatment with hydrofluoric acid to partially remove the silicon dioxide deposited on the surface of the polystyrene ball to obtain a silver nanostructure on the flexible substrate.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing periodic nano materials for flexible substrates, and in particular relates to a method for preparing a nano structure on a flexible substrate. Technical Background

[0002] The periodic nano pattern structure can be prepared on a flexible substrate by using magnetron sputtering, chemical reaction, plasma cleaning machine, spin coating and other technologies. The nano pattern structure is built on a flexible substrate by using the characteristics of strong adhesion, good elasticity and good biocompatibility of the flexible substrate, so that the nano pattern is closer to the human body and the human body can be detected in real time. PVA glue is built on the structure by using spin coating and other methods, and the external environment is used to affect the morphology of the PVA glue, thereby changing the morphology of the metal particles built on the PVA glue to obtain a good detection basis.

[0003] Magnetron sputtering is a type of physical vapor deposition (PVD). The general sputtering method can be used to prepare multiple materials such as metals, semiconductors, insulators, etc., and has the advantages of simple equipment, easy control, large coating area and strong adhesion. Its working principle is that electrons collide with argon atoms in the process of flying to the substrate under the action of the electric field E, ionizing them to produce Ar positive ions and new electrons; the new electrons fly to the substrate, and the Ar ions are accelerated to fly to the cathode target under the action of the electric field, and bombard the target surface with high energy, causing the target material to sputter.

[0004] Surface enhanced Raman scattering (SERS) technology overcomes the inherent weakness of weak signals in traditional Raman spectroscopy and can increase the Raman intensity by several orders of magnitude. Its enhancement factor can be as high as 10 14 ~10 15 times, which is enough to detect the Raman signal of a single molecule, which is beyond the sensitivity and measurement speed of traditional Raman. The most commonly used metals are gold and silver, but the SERS intensity of a single-layer metal film is limited, and its test range and size are greatly limited. Therefore, it is of great significance to improve the SERS intensity of a single-layer metal film, which can be fully applied in many fields such as environmental monitoring, food safety, clinical testing and disease diagnosis. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing nano patterns on a flexible substrate. The method uses PDMS glue as a flexible substrate, uses a machine film discharge method on the PDMS glue to prepare an ordered polystyrene ball array, uses a spin coating method on the surface of the polystyrene array to prepare a layer of PVA glue, and uses a plasma cleaning machine to etch the PVA glue to different degrees. Since the PVA glue is on the surface of the PS ball and has a certain thickness, the etching process first acts on the PVA glue, and by accurately controlling the etching time, the PVA glue is thinned without damaging the PS ball. Finally, silver nanoparticles are sputtered on the sample surface for 10 seconds. The surface morphology changes caused by the water absorption and dehydration of the PVA glue are used to change the gap and position of the silver nanoparticles built on it, thereby changing the SERS intensity.

[0006] The steps of the preparation method of the present invention are as follows:

[0007] S1 prepares PDMS flexible substrate;

[0008] S2 preparing a hexagonal close-packed polystyrene ball array on the PDMS flexible substrate to obtain a polystyrene ball array on the flexible substrate;

[0009] S3 prepares PVA hydrosol;

[0010] S4: spin-coating the PVA hydrosol onto the polystyrene ball array on the flexible substrate obtained in S2, so that the surface of the polystyrene ball array is covered with the PVA glue;

[0011] S5: the PVA glue covering the surface of the polystyrene ball array is plasma cleaned and etched to reduce the thickness of the PVA glue layer on the surface of the polystyrene ball array so that the polystyrene balls are not completely covered by the PVA glue.

[0012] S6 uses magnetron sputtering to deposit silver and silicon dioxide on the surface of the polystyrene ball array treated with the PVA glue etched in S5.

[0013] S7 is subjected to surface chemical treatment with hydrofluoric acid to partially remove the silicon dioxide deposited on the surface of the polystyrene balls in S6, and obtain a silver nanostructure on a flexible substrate. Since SiO2 plays a role in spacing the silver nanoparticles during the co-sputtering process, after the SiO2 is corroded, the silver nanoparticles form obvious gaps, which are the main part of providing SERS hotspots. For a pure silver monolayer film, due to the fast sputtering rate, a compact film structure is formed without obvious gaps.

[0014] Beneficial effects of the present invention

[0015] The present invention designs and prepares a nano pattern structure prepared on a flexible substrate, which makes silver nanoparticles arranged in a spatially disordered manner, greatly enhances its Raman intensity, and forms a spatial ultra-dense hot spot distribution. PVA glue is used as a flexible spacer, and the morphology of silver nanoparticles built on PVA is changed by changing the PVA morphology, thereby changing the SERS intensity. Physical and chemical co-treatment methods are adopted. A new experimental scheme is proposed to design and prepare the nano pattern to be obtained. First, based on the preparation of a flexible substrate, PDMS glue is a polymer with good biocompatibility. With its good flexibility and elasticity, it is the best choice for a flexible substrate. Based on a polystyrene ball array and PVA glue, a nano pattern is built, and the morphology of the nano pattern is adjusted by adjusting the etching degree of the PVA glue. Finally, magnetron sputtering and co-sputtering are used to co-sputter silver and silicon dioxide nanoparticles on the sample surface, and HF is used to corrode silicon dioxide to different degrees, and finally the sample we need is formed. Since the surface of the PVA glue is etched to different degrees by a plasma cleaner, its morphology changes differently, and finally the gaps between the silver nanoparticles built on it are different. The water absorption and dehydration of PVA glue, as well as the degree of change in external activities, are used to change the position of silver nanoparticles, resulting in different SERS intensities. Since the sizes of silver nanoparticles with different powers are different, we conducted multiple experiments to find the most suitable particle size. When parameters such as power, content ratio, and air pressure are constant, the sample effect and SERS intensity are only determined by the film state formed by the etching time of PVA glue by the plasma cleaner. Therefore, the technology of the present invention changes the SERS intensity by changing the etching time of PVA glue, thereby exploring the best nano pattern effect. Thus, a new structural method is explored on a flexible substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 : Flow chart of the method according to the embodiment of the present invention;

[0017] Figure 2 :40μl of PVA glue was spin-coated on the sample. A plasma etcher was used to etch for 90s, and the sample was sputtered for 10s using a co-sputtering power of 10W for silver and 40W for silicon dioxide. After HF etching for 10s, the scanning electron microscope image was obtained;

[0018] Figure 3 : 40μl of PVA glue was spin-coated on the sample. A plasma etcher was used to etch for 120s, and the sample was sputtered for 10s using a co-sputtering power of 10W for silver and 40W for silicon dioxide. After HF etching for 10s, the scanning electron microscope image was obtained;

[0019] Figure 4: 40μl of PVA glue was spin-coated on the sample. A plasma etcher was used to etch for 150s, the sample was sputtered for 10s using a co-sputtering power of 10W for silver and 40W for silicon dioxide, and HF etching was performed for 10s to obtain a scanning electron microscope image;

[0020] Figure 5 : 40μl of PVA glue was spin-coated on the sample. A plasma etcher was used to etch for 180s, the sample was sputtered for 10s using a co-sputtering power of 10W for silver and 40W for silicon dioxide, and HF etching was performed for 10s to obtain a scanning electron microscope image;

[0021] Figure 6 : 40μl of PVA glue was spin-coated on the sample. A plasma etcher was used to etch for 210s, and the sample was sputtered for 10s using a co-sputtering power of 10W for silver and 40W for silicon dioxide. After HF etching for 10s, the scanning electron microscope image was obtained;

[0022] Figure 7 : 40μl of PVA glue was spin-coated on the sample. A plasma etcher was used to etch for 240s, and the sample was sputtered for 10s using a co-sputtering power of 10W for silver and 40W for silicon dioxide. After HF etching for 10s, the scanning electron microscope image was obtained; DETAILED DESCRIPTION

[0023] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are all conventional methods in the art.

[0024] Embodiment 1

[0025] 1) Preparation of PDMS flexible substrate

[0026] 1a) Cleaning the culture dish: Soak the culture dish in deionized water and anhydrous ethanol respectively, then use an ultrasonic device to sonicate for 10 minutes to wash away the dust and oil stains on the surface of the culture dish. Take out the culture dish and place it on absorbent paper to absorb the remaining water.

[0027] 1b) Hydrophilic treatment. Place the culture dish in a beaker and add a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:2:6. Place the beaker on a baking sheet and heat it to boiling, and keep boiling for 10 minutes. After cooling, pour out the liquid and repeatedly ultrasonicate it with deionized water and anhydrous ethanol for 15 minutes.

[0028] 1c) Place PDMS glue and coagulant in a clean culture dish at a ratio of 10:1 and stir evenly until there are no bubbles. Place in a dust-free cabinet and let stand for two days. After it solidifies and becomes a 1*1cm flexible substrate, it is ready for use.

[0029] 2) Preparation of hexagonal close-packed polystyrene ball arrays. Polystyrene balls with a diameter of 500 nm and anhydrous ethanol were mixed in a volume ratio of 1:1, and then the polystyrene balls were evenly dispersed by ultrasonic treatment. The polystyrene ball dispersion was dropped on a large silicon wafer with a pipette to make the dispersion evenly distributed on the silicon wafer. The large silicon wafer was slowly tilted and slid into a container with a stable liquid surface to form a close-packed polystyrene ball array on the water surface. Finally, the ball array floating on the water surface was slowly scooped up with a flexible substrate, and dried after absorbing water for later use.

[0030] 3) Weigh 1% PVA powder, add deionized water, put in a magnetic stirrer, place on a stirring heating table, heat and stir at 90° until all particles in the solution are dissolved in water. 1% PVA glue is prepared.

[0031] 4) Use a spin coater to spin coat 1% PVA glue onto the sample: take 40 μl PVA glue, use a glue spreading speed of 2510 RPM, spin coat for 18 seconds, and then use a glue spreading speed of 8520 RPM, spin coat for 60 seconds.

[0032] 5) Use a plasma cleaner to etch the sample for 90 seconds to obtain different morphological effects

[0033] 6) Use magnetron sputtering to make silver and silicon dioxide co-sputtered films on the sample. Tilt the silver target and silicon dioxide target 40 degrees each and sputter them to the sample at the same time. After many tests, it is believed that the SERS enhancement effect is best when the power of silver is 10W and the power of silicon dioxide is 40W. The background pressure before starting is 4.5×10 -4 Pa, 25 sccm of Ar was introduced, the background pressure during sputtering was 1.5 Pa, and the sputtering time was 10 min. Under this condition, the element mass ratio of silver to silicon was 4:1.

[0034] 7) Use 20% by mass hydrofluoric acid for surface chemical treatment and etch for 30 seconds to etch away the silicon dioxide in the co-sputtering to form a silver nanoparticle film.

[0035] Embodiment 2

[0036] 1) Preparation of PDMS flexible substrate

[0037] 1a) Cleaning the culture dish: Soak the culture dish in deionized water and anhydrous ethanol respectively, then use an ultrasonic device to sonicate for 10 minutes to wash away the dust and oil stains on the surface of the culture dish. Take out the culture dish and place it on absorbent paper to absorb the remaining water.

[0038] 1b) Hydrophilic treatment. Place the culture dish in a beaker and add a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:2:6. Place the beaker on a baking sheet and heat it to boiling, and keep boiling for 10 minutes. After cooling, pour out the liquid and repeatedly ultrasonicate it with deionized water and anhydrous ethanol for 15 minutes.

[0039] 1c) Place PDMS glue and coagulant in a clean culture dish at a ratio of 10:1 and stir evenly until there are no bubbles. Place in a dust-free cabinet and let stand for two days. After it solidifies and becomes a 1*1cm flexible substrate, it is ready for use.

[0040] 2) Preparation of hexagonal close-packed polystyrene ball arrays. Polystyrene balls with a diameter of 500 nm and anhydrous ethanol were mixed in a volume ratio of 1:1, and then the polystyrene balls were evenly dispersed by ultrasonic treatment. The polystyrene ball dispersion was dropped on a large silicon wafer with a pipette to make the dispersion evenly distributed on the silicon wafer. The large silicon wafer was slowly tilted and slid into a container with a stable liquid surface to form a close-packed polystyrene ball array on the water surface. Finally, the ball array floating on the water surface was slowly scooped up with a flexible substrate, and dried after absorbing water for later use.

[0041] 3) Weigh 1% PVA powder, add deionized water, put in a magnetic stirrer, place on a stirring heating table, heat and stir at 90° until all particles in the solution are dissolved in water. 1% PVA glue is prepared.

[0042] 4) Use a spin coater to spin coat 1% PVA glue onto the sample: take 40 μl PVA glue, use a glue spreading speed of 2510 RPM, spin coat for 18 seconds, and then use a glue spreading speed of 8520 RPM, spin coat for 60 seconds.

[0043] 5) Use a plasma cleaner to etch the sample for 120s to obtain different morphological effects

[0044] 6) Use magnetron sputtering to make silver and silicon dioxide co-sputtered films on the sample. Tilt the silver target and silicon dioxide target 40 degrees each and sputter them to the sample at the same time. After many tests, it is believed that the SERS enhancement effect is best when the power of silver is 10W and the power of silicon dioxide is 40W. The background pressure before starting is 4.5×10 -4 Pa, 25 sccm of Ar was introduced, the background pressure during sputtering was 1.5 Pa, and the sputtering time was 10 min. Under this condition, the ratio of silver to silicon dioxide was 4:1.

[0045] 7) Use 20% by mass hydrofluoric acid for surface chemical treatment and etch for 30 seconds to etch away the silicon dioxide in the co-sputtering to form a silver nanoparticle film.

[0046] Embodiment 3

[0047] 1) Preparation of PDMS flexible substrate

[0048] 1a) Cleaning the culture dish: Soak the culture dish in deionized water and anhydrous ethanol respectively, then use an ultrasonic device to sonicate for 10 minutes to wash away the dust and oil stains on the surface of the culture dish. Take out the culture dish and place it on absorbent paper to absorb the remaining water.

[0049] 1b) Hydrophilic treatment. Place the culture dish in a beaker and add a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:2:6. Place the beaker on a baking sheet and heat it to boiling, and keep boiling for 10 minutes. After cooling, pour out the liquid and repeatedly ultrasonicate it with deionized water and anhydrous ethanol for 15 minutes.

[0050] 1c) Place PDMS glue and coagulant in a clean culture dish at a ratio of 10:1 and stir evenly until there are no bubbles. Place in a dust-free cabinet and let stand for two days. After it solidifies and becomes a 1*1cm flexible substrate, it is ready for use.

[0051] 2) Preparation of hexagonal close-packed polystyrene ball arrays. Polystyrene balls with a diameter of 500 nm and anhydrous ethanol were mixed in a volume ratio of 1:1, and then the polystyrene balls were evenly dispersed by ultrasonic treatment. The polystyrene ball dispersion was dropped on a large silicon wafer with a pipette to make the dispersion evenly distributed on the silicon wafer. The large silicon wafer was slowly tilted and slid into a container with a stable liquid surface to form a close-packed polystyrene ball array on the water surface. Finally, the ball array floating on the water surface was slowly scooped up with a flexible substrate, and dried after absorbing water for later use.

[0052] 3) Weigh 1% PVA powder, add deionized water, put in a magnetic stirrer, place on a stirring heating table, heat and stir at 90° until all particles in the solution are dissolved in water. 1% PVA glue is prepared.

[0053] 4) Use a spin coater to spin coat 1% PVA glue onto the sample: take 40 μl PVA glue, use a glue spreading speed of 2510 RPM, spin coat for 18 seconds, and then use a glue spreading speed of 8520 RPM, spin coat for 60 seconds.

[0054] 5) Use a plasma cleaner to etch the sample for 150 seconds to obtain different morphological effects

[0055] 6) Use magnetron sputtering to make silver and silicon dioxide co-sputtered films on the sample. Tilt the silver target and silicon dioxide target 40 degrees each and sputter them to the sample at the same time. After many tests, it is believed that the SERS enhancement effect is best when the power of silver is 10W and the power of silicon dioxide is 40W. The background pressure before starting is 4.5×10 -4Pa, 25 sccm of Ar was introduced, the background pressure during sputtering was 1.5 Pa, and the sputtering time was 10 min. Under this condition, the ratio of silver to silicon dioxide was 4:1.

[0056] 7) Use 20% by mass hydrofluoric acid for surface chemical treatment and etch for 30 seconds to etch away the silicon dioxide in the co-sputtering to form a silver nanoparticle film.

[0057] Embodiment 4

[0058] 1) Preparation of PDMS flexible substrate

[0059] 1a) Cleaning the culture dish: Soak the culture dish in deionized water and anhydrous ethanol respectively, then use an ultrasonic device to sonicate for 10 minutes to wash away the dust and oil stains on the surface of the culture dish. Take out the culture dish and place it on absorbent paper to absorb the remaining water.

[0060] 1b) Hydrophilic treatment. Place the culture dish in a beaker and add a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:2:6. Place the beaker on a baking sheet and heat it to boiling, and keep boiling for 10 minutes. After cooling, pour out the liquid and repeatedly ultrasonicate it with deionized water and anhydrous ethanol for 15 minutes.

[0061] 1c) Place PDMS glue and coagulant in a clean culture dish at a ratio of 10:1 and stir evenly until there are no bubbles. Place in a dust-free cabinet and let stand for two days. After it solidifies and becomes a 1*1cm flexible substrate, it is ready for use.

[0062] 2) Preparation of hexagonal close-packed polystyrene ball arrays. Polystyrene balls with a diameter of 500 nm and anhydrous ethanol were mixed in a volume ratio of 1:1, and then the polystyrene balls were evenly dispersed by ultrasonic treatment. The polystyrene ball dispersion was dropped on a large silicon wafer with a pipette to make the dispersion evenly distributed on the silicon wafer. The large silicon wafer was slowly tilted and slid into a container with a stable liquid surface to form a close-packed polystyrene ball array on the water surface. Finally, the ball array floating on the water surface was slowly scooped up with a flexible substrate, and dried after absorbing water for later use.

[0063] 3) Weigh 1% PVA powder, add deionized water, put in a magnetic stirrer, place on a stirring heating table, heat and stir at 90° until all particles in the solution are dissolved in water. 1% PVA glue is prepared.

[0064] 4) Use a spin coater to spin coat 1% PVA glue onto the sample: take 40 μl PVA glue, use a glue spreading speed of 2510 RPM, spin coat for 18 seconds, and then use a glue spreading speed of 8520 RPM, spin coat for 60 seconds.

[0065] 5) Use a plasma cleaner to etch the sample for 180s to obtain different morphological effects

[0066] 6) Use magnetron sputtering to make silver and silicon dioxide co-sputtered films on the sample. Tilt the silver target and silicon dioxide target 40 degrees each and sputter them to the sample at the same time. After many tests, it is believed that the SERS enhancement effect is best when the power of silver is 10W and the power of silicon dioxide is 40W. The background pressure before starting is 4.5×10 -4 Pa, 25 sccm of Ar was introduced, the background pressure during sputtering was 1.5 Pa, and the sputtering time was 10 min. Under this condition, the ratio of silver to silicon dioxide was 4:1.

[0067] 7) Use 20% by mass hydrofluoric acid for surface chemical treatment and etch for 30 seconds to etch away the silicon dioxide in the co-sputtering to form a silver nanoparticle film.

[0068] Embodiment 5

[0069] 1) Preparation of PDMS flexible substrate

[0070] 1a) Cleaning the culture dish: Soak the culture dish in deionized water and anhydrous ethanol respectively, then use an ultrasonic device to sonicate for 10 minutes to wash away the dust and oil stains on the surface of the culture dish. Take out the culture dish and place it on absorbent paper to absorb the remaining water.

[0071] 1b) Hydrophilic treatment. Place the culture dish in a beaker and add a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:2:6. Place the beaker on a baking sheet and heat it to boiling, and keep boiling for 10 minutes. After cooling, pour out the liquid and repeatedly ultrasonicate it with deionized water and anhydrous ethanol for 15 minutes.

[0072] 1c) Place PDMS glue and coagulant in a clean culture dish at a ratio of 10:1 and stir evenly until there are no bubbles. Place in a dust-free cabinet and let stand for two days. After it solidifies and becomes a 1*1cm flexible substrate, it is ready for use.

[0073] 2) Preparation of hexagonal close-packed polystyrene ball arrays. Polystyrene balls with a diameter of 500 nm and anhydrous ethanol were mixed in a volume ratio of 1:1, and then the polystyrene balls were evenly dispersed by ultrasonic treatment. The polystyrene ball dispersion was dropped on a large silicon wafer with a pipette to make the dispersion evenly distributed on the silicon wafer. The large silicon wafer was slowly tilted and slid into a container with a stable liquid surface to form a close-packed polystyrene ball array on the water surface. Finally, the ball array floating on the water surface was slowly scooped up with a flexible substrate, and dried after absorbing water for later use.

[0074] 3) Weigh 1% PVA powder, add deionized water, put in a magnetic stirrer, place on a stirring heating table, heat and stir at 90° until all particles in the solution are dissolved in water. 1% PVA glue is prepared.

[0075] 4) Use a spin coater to spin coat 1% PVA glue onto the sample: take 40 μl PVA glue, use a glue spreading speed of 2510 RPM, spin coat for 18 seconds, and then use a glue spreading speed of 8520 RPM, spin coat for 60 seconds.

[0076] 5) Use a plasma cleaner to etch the sample for 210s to obtain different morphological effects

[0077] 6) Use magnetron sputtering to make silver and silicon dioxide co-sputtered films on the sample. Tilt the silver target and silicon dioxide target 40 degrees each and sputter them to the sample at the same time. After many tests, it is believed that the SERS enhancement effect is best when the power of silver is 10W and the power of silicon dioxide is 40W. The background pressure before starting is 4.5×10 -4 Pa, 25 sccm of Ar was introduced, the background pressure during sputtering was 1.5 Pa, and the sputtering time was 10 min. Under this condition, the ratio of silver to silicon dioxide was 4:1.

[0078] 7) Use 20% by mass hydrofluoric acid for surface chemical treatment and etch for 30 seconds to etch away the silicon dioxide in the co-sputtering to form a silver nanoparticle film.

[0079] Embodiment 6

[0080] 1) Preparation of PDMS flexible substrate

[0081] 1a) Cleaning the culture dish: Soak the culture dish in deionized water and anhydrous ethanol respectively, then use an ultrasonic device to sonicate for 10 minutes to wash away the dust and oil stains on the surface of the culture dish. Take out the culture dish and place it on absorbent paper to absorb the remaining water.

[0082] 1b) Hydrophilic treatment. Place the culture dish in a beaker and add a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:2:6. Place the beaker on a baking sheet and heat it to boiling, and keep boiling for 10 minutes. After cooling, pour out the liquid and repeatedly ultrasonicate it with deionized water and anhydrous ethanol for 15 minutes.

[0083] 1c) Place PDMS glue and coagulant in a clean culture dish at a ratio of 10:1 and stir evenly until there are no bubbles. Place in a dust-free cabinet and let stand for two days. After it solidifies and becomes a 1*1cm flexible substrate, it is ready for use.

[0084] 2) Preparation of hexagonal close-packed polystyrene ball arrays. Polystyrene balls with a diameter of 500 nm and anhydrous ethanol were mixed in a volume ratio of 1:1, and then the polystyrene balls were evenly dispersed by ultrasonic treatment. The polystyrene ball dispersion was dropped on a large silicon wafer with a pipette to make the dispersion evenly distributed on the silicon wafer. The large silicon wafer was slowly tilted and slid into a container with a stable liquid surface to form a close-packed polystyrene ball array on the water surface. Finally, the ball array floating on the water surface was slowly scooped up with a flexible substrate, and dried after absorbing water for later use.

[0085] 3) Weigh 1% PVA powder, add deionized water, put in a magnetic stirrer, place on a stirring heating table, heat and stir at 90° until all particles in the solution are dissolved in water. 1% PVA glue is prepared.

[0086] 4) Use a spin coater to spin coat 1% PVA glue onto the sample: take 40 μl PVA glue, use a glue spreading speed of 2510 RPM, spin coat for 18 seconds, and then use a glue spreading speed of 8520 RPM, spin coat for 60 seconds.

[0087] 5) Use a plasma cleaner to etch the sample for 240s to obtain different morphological effects

[0088] 6) Use magnetron sputtering to make silver and silicon dioxide co-sputtered films on the sample. Tilt the silver target and silicon dioxide target 40 degrees each and sputter them to the sample at the same time. After many tests, it is believed that the SERS enhancement effect is best when the power of silver is 10W and the power of silicon dioxide is 40W. The background pressure before starting is 4.5×10 -4 Pa, 25 sccm of Ar was introduced, the background pressure during sputtering was 1.5 Pa, and the sputtering time was 10 min. Under this condition, the ratio of silver to silicon dioxide was 4:1.

[0089] 7) Use 20% by mass hydrofluoric acid for surface chemical treatment and etch for 30 seconds to etch away the silicon dioxide in the co-sputtering to form a silver nanoparticle film.

Claims

1. A method for preparing a nanostructure on a flexible substrate, characterized in that: The following steps are involved: S1 prepares PDMS flexible substrate; S2 preparing a hexagonal close-packed polystyrene ball array on the PDMS flexible substrate to obtain a polystyrene ball array on the flexible substrate; S3 prepares PVA hydrosol; S4: spin-coating the PVA hydrosol onto the polystyrene ball array on the flexible substrate obtained in S2, so that the surface of the polystyrene ball array is covered with the PVA glue; S5. The PVA glue covering the surface of the polystyrene ball array is plasma cleaned and then etched to reduce the thickness of the PVA glue layer on the surface of the polystyrene ball array so that the polystyrene balls are not completely covered by the PVA glue. The etching time ranges from 90s to 240s. S6 uses magnetron sputtering to deposit silver and silicon dioxide on the surface of the polystyrene ball array after the PVA glue is etched in S5; S7: The silicon dioxide deposited on the surface of the polystyrene sphere in S6 is subjected to surface chemical treatment with hydrofluoric acid to obtain a silver nanostructure on a flexible substrate; The method for preparing a hexagonally close-packed polystyrene ball array on the PDMS flexible substrate in step S2 comprises the following steps: Mix polystyrene beads with a diameter of 500 nm and anhydrous ethanol in a volume ratio of 1:1, and then evenly disperse the polystyrene beads by ultrasonic treatment to obtain a polystyrene bead dispersion. Take a silicon wafer, use a pipette to drop the polystyrene bead dispersion on the silicon wafer, so that the polystyrene bead dispersion is evenly distributed on the silicon wafer, and slowly slide the silicon wafer into a vessel with a stable liquid surface to form a dense array of polystyrene beads on the water surface. Finally, use the PDMS flexible substrate obtained in S1 to slowly pick up the bead array floating on the water surface and absorb water and dry it. In step S6, the magnetron sputtering includes the following steps: The silver target and the silicon dioxide target were tilted 40 degrees toward the flexible substrate and sputtered simultaneously. The power of silver sputtering was 10 W, the power of silicon dioxide sputtering was 40 W, and the background pressure before sputtering was 4.5×10 -4 Pa, 25 sccm of Ar was introduced, the background pressure during sputtering was 1.5 Pa, the sputtering time was 10 min, and the element mass ratio of deposited silver and silicon was 4:

1.

2. A method for preparing a nanostructure on a flexible substrate as claimed in claim 1, characterized in that: The step S1 specifically includes the following steps: 1a Cleaning the culture dish: Soak the culture dish in deionized water and anhydrous ethanol respectively, and then use ultrasonic cleaning to remove the dust, dirt and oil stains on the surface of the culture dish; 1b Place the culture dish in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:2:6, heat the mixed solution to boiling and keep it for 10 minutes, take out the culture dish, cool it, and then repeatedly ultrasonically clean it with deionized water and anhydrous ethanol; 1c. Place PDMS glue and coagulant in a mass ratio of 10:1 in the culture dish cleaned in step 1b, stir evenly until there are no bubbles, and let stand to solidify in a dust-free environment to obtain a PDMS flexible substrate.

3. The method for preparing a nanostructure on a flexible substrate as claimed in claim 1, characterized in that: In step S3, the method for preparing the PVA hydrosol comprises the following steps: Weigh PVA powder according to the mass ratio of PVA powder to deionized water of 1:100, add deionized water, put in a magnetic stirrer, place on a stirring heating table, heat and stir at 90°C until all the particles in the solution are dissolved in water.

4. The method for preparing a nanostructure on a flexible substrate as claimed in claim 1, characterized in that: In step S4, the spin coating process is as follows: On the 1*1 cm flexible substrate, take 40 μl of PVA hydrosol, set the spin coating speed to 2510 RPM, and spin coating for 18 seconds to spread the glue. Set the spin coating speed to 8520 RPM and spin coating for 60 seconds to spread the glue.

5. A method for preparing a nanostructure on a flexible substrate as claimed in claim 4, characterized in that: The process of performing surface chemical treatment with hydrofluoric acid in step S7 is as follows: The surface was chemically treated with a 20% by mass hydrofluoric acid aqueous solution for 30 seconds.

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