Forming method of micro-nano cavity structure

Abstract

The invention provides a forming method of a micro-nano cavity structure, and belongs to the field of micro-nano structure manufacturing, a cavity structure is formed on a to-be-formed surface through a laser direct writing technology, a plurality of through holes are formed in the surface of the cavity structure, and the through holes are communicated between a cavity and the external environment; a closed structure is formed on the outer surface of the cavity structure through a laser direct writing technology, the closed structure is attached to the outer surface of the cavity structure, and the through holes are closed through the closed structure at the same time; according to the forming method, the cavity structure with the holes is firstly formed, then the closed structure is formed on the surface of the cavity structure to cover the through holes, high-precision three-dimensional structure forming of the micro-nano cavity can be achieved, by means of the forming method, the structural design of the cavity can have the extremely high freedom degree, and the cavity forming difficulty is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano structure manufacturing, and in particular to a molding method of a micro-nano cavity structure. Background Art

[0002] Cavity is a micro-nano structure widely used in the field of sensing. The closed environment formed by the air layer can significantly improve the detection sensitivity and working stability of the sensor. For example, in the field of optical fiber sensing, a cavity is set at the end of the optical fiber to form optical interference; when the light wave enters the cavity and reflects at both ends, the phase difference between the reflected light waves will change with the change of the cavity length, thus forming interference fringes that can be used for signal detection. In the field of ultrasonic detection, the cavity has a reflection and resonance effect on the sound wave; after the ultrasonic wave enters the cavity, it is reflected inside it, and the phase and amplitude changes of the reflected wave can be used to measure the characteristics of the sound wave. By reducing the volume of the cavity structure, a higher degree of integration can be achieved, making the sensor device more miniaturized and easy to integrate into complex systems. Therefore, improving the processing accuracy and molding freedom of the cavity structure and developing a new micro-nano cavity packaging process are of great significance to the research in related fields.

[0003] At present, the processing of cavity structures is mainly achieved through sacrificial layers, and sacrificial materials are removed by photolithography and selective etching to form a cavity inside a closed structure. This method is widely used in micro-electromechanical systems, but this method is mainly based on two-dimensional planar processes, such as photolithography and anisotropic etching, and it is difficult to directly realize complex three-dimensional structures. Although certain three-dimensional structures can be achieved through multi-layer deposition and etching steps, these steps increase the complexity and difficulty of the process. In addition, there are also methods for preparing micro-nano cavities on optical fibers through bubble blowing, fusion, stretching discharge and other methods. These processing methods can only realize the processing of a single structure and do not have the ability to control the shape of the cavity structure in three dimensions.

[0004] It can be seen that the current limitations in achieving three-dimensional molding and preparation of micro-nano cavity structures mainly include the following issues:

[0005] (1) Limitation of molding methods. The size of micro-nano cavity structures is usually at the micrometer or even nanometer level, which requires extremely high processing accuracy. It is difficult to prepare high-precision unprecedented high structures through mechanical alignment or bubble blowing.

[0006] (2) Processing freedom limitation. Semiconductor-based micro-nano processing technologies, such as electron beam lithography, focused ion beam, and deep reactive ion etching, are usually based on planar processing methods, which make it difficult to perform structural processing in three-dimensional space, limiting the freedom of structural molding.

[0007] In summary, there is currently no effective method for the preparation and encapsulation of three-dimensional micro-nano cavity structures. Summary of the invention

[0008] In view of this, the present invention proposes a molding method for a micro-nano cavity structure to solve the problems of molding method limitations and processing freedom limitations in the current three-dimensional molding and preparation technologies for micro-nano cavity structures.

[0009] The technical solution of the present invention is implemented as follows: The present invention provides a method for forming a micro-nano cavity structure, comprising the following steps: step one, forming a cavity structure on a surface to be formed by laser direct writing technology, a cavity is opened inside the cavity structure, and a plurality of through holes are opened on the surface of the cavity structure, and the through holes are connected between the cavity and the external environment; step two, forming a closed structure on the outer surface of the cavity structure by laser direct writing technology, the closed structure is attached to the outer surface of the cavity structure, and the closed structure simultaneously closes a plurality of through holes.

[0010] On the basis of the above technical solution, preferably, in step one, after the cavity structure is formed, a surface treatment is performed on the surface of the cavity structure where the through hole is opened and a modified layer is formed, and the modified layer improves the adhesion of the outer surface of the cavity structure.

[0011] More preferably, the thickness of the modified layer is 5 to 50 nm.

[0012] On the basis of the above technical solution, preferably, in step 2, after the closed structure is formed, surface treatment is performed on the outer surfaces of the cavity structure and the closed structure and a reinforcement layer is formed, and the reinforcement layer improves the sealing of the cavity structure.

[0013] On the basis of the above technical solution, preferably, the shapes and inner diameters of the plurality of through holes are different.

[0014] More preferably, the through hole is polygonal or elliptical.

[0015] More preferably, the inner diameter of the through hole is not greater than 10 μm.

[0016] On the basis of the above technical solution, preferably, the outer contour of the cavity structure is columnar or spherical.

[0017] Further preferably, when the cavity structure is columnar, one end of the cavity structure along the vertical direction of the surface to be formed is an end face, the wall surface of the cavity structure surrounding the surface to be formed in the vertical direction is an outer peripheral wall, and a plurality of through holes are arranged on the end face or the outer peripheral wall.

[0018] On the basis of the above technical solution, preferably, the surface to be molded is the optical fiber end face of the optical fiber sensor.

[0019] The molding method of a micro-nano cavity structure of the present invention has the following beneficial effects compared with the prior art:

[0020] (1) The present invention first forms a cavity structure with holes, and then forms a closed structure on the surface of the cavity structure to cover the through holes, which can achieve high-precision three-dimensional structure forming of micro-nano cavities. This forming method enables the structural design of the cavity to have extremely high degrees of freedom and greatly reduces the difficulty of cavity forming.

[0021] (2) The modified layer is arranged on the surface of the cavity structure of the present invention, which can greatly improve the bonding strength between the cavity structure surface and the closed structure. Then, by arranging a reinforcement layer on the outer surface of the cavity structure, the reinforcement layer fills the gap between the closed structure and the outer surface of the cavity structure, thereby greatly improving the sealing of the cavity structure after molding, realizing the liquid intrusion resistance design and packaging method of the cavity structure, and realizing effective sealing of the air layer through the structural design of different through-hole inner diameters and shapes and surface tension control, thereby reducing the packaging difficulty of the micro-nano cavity structure.

[0022] (3) The micro-nano cavity structure forming method proposed in the present invention can be flexibly adapted to devices such as optical fibers, thereby reducing the difficulty of integrating sensor components and increasing the degree of freedom in sensor function design. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a cross-sectional schematic diagram of the micro-nano cavity structure of the molding method of the present invention;

[0025] Figure 2 A cross-sectional schematic diagram of a micro-nano cavity structure according to another embodiment of the molding method of the present invention;

[0026] Figure 3 It is a three-dimensional schematic diagram of the micro-nano cavity structure of the molding method of the present invention;

[0027] Figure 4 A three-dimensional schematic diagram of a micro-nano cavity structure of another embodiment of the molding method of the present invention;

[0028] Figure 5 The optical and scanning electron microscopic imaging characterization result diagram of the micro-nano cavity structure of the molding method of the present invention;

[0029] Figure 6 It is a cross-sectional schematic diagram of the optical microscopic imaging characterization results of the micro-nano cavity structure of the molding method of the present invention after the surface treatment of magnetron sputtering coating;

[0030] Figure 7 It is a cross-sectional schematic diagram of optical and scanning electron microscopic imaging characterization results of the micro-nano cavity structure of the molding method of the present invention after being blocked by a closed structure;

[0031] Figure 8 A schematic diagram of the working principle of an optical fiber sensor based on a micro-nano cavity structure of the present invention;

[0032] Fig. 9 This is a comparison result diagram of the sensing signal stability of an optical fiber sensor based on a micro-nano cavity structure of the present invention when using an unblocked structure and a blocked structure.

[0033] In the figure: 1. cavity structure; 101. cavity; 102. through hole; 2. closed structure; 3. modified layer; 4. enhanced layer. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, combined Figure 2 and Figure 3 A method for forming a micro-nano cavity structure of the present invention comprises the following steps:

[0036] Step 1: A cavity structure 1 is formed on a surface to be formed by laser direct writing technology. The cavity structure 1 can be prepared from different types of materials, and the material is determined by the photoresist used in the laser direct writing process. The material used can be acrylate photoresist, epoxy resin photoresist, hydrogel precursor, metal particle solution precursor, etc. A cavity 101 is provided inside the cavity structure 1. For example, in this embodiment, the surface to be formed is the end face of an optical fiber. The preset axis is the axis of the optical fiber extension direction. The outer contour of the cavity structure 1 in this embodiment is centrally symmetrical around a preset axis. The preset axis is perpendicular to the surface to be formed. A plurality of through holes 102 are provided on the surface of the cavity structure 1 around the axial direction of the cavity structure 1. The through holes 102 are connected between the cavity 101 and the external environment. The function of the through holes 102 is to allow the photoresist to flow out of the cavity structure 1 in the development step after laser direct writing. Laser direct writing refers to a micro-nano processing method based on the principle of two-photon polymerization. The laser used is an ultrafast laser, such as picosecond laser, femtosecond laser, etc. Laser direct writing is achieved through the linkage of a scanner and a displacement stage. The scanner can be a galvanometer, a rotating mirror, and an acousto-optic scanner, etc. The displacement stage can achieve high-precision movement based on piezoelectric, ball screw, double cross ball, etc. When forming the cavity mechanism 1, the cavity structure 1 needs to meet the forming conditions of the microporous structure and the mechanical properties of the structure at the same time. The structure will not collapse due to mechanical instability before and after processing; the size and structure of the through hole 102 are determined according to the material forming process, and the minimum formable parameters and structural dimensions are determined by parameter scanning.

[0037] In addition, if Figure 4 As shown, the through holes 102 on the surface of the cavity structure 1 may also be opened on the end face and the outer peripheral wall of the cavity structure 1 at the same time. In this case, the closed structure 2 needs to be formed on the end face and the outer peripheral wall of the cavity structure 1 at the same time to form an irregular shaped structure, which can be a ring or a broken ring. It is only required to close all the through holes 102 at the same time.

[0038] Specifically, laser direct writing uses polydimethylsiloxane (PDMS)-based photoresist as the material to make the cavity structure 1. The light source used for laser direct writing is a femtosecond laser with a wavelength of 780nm, a pulse width of 80fs, and a laser power of 25mW. A galvanometer is used as a laser scanner, and a piezoelectric displacement stage is used for high-precision motion control during the processing process. The scanning speed of the femtosecond laser focus is 10mm / s.

[0039] During processing, PDMS photoresist is dropped onto a glass substrate, and the objective lens is adjusted to obtain optimal focus, ensuring that the focus of the femtosecond laser system is precisely aligned with the substrate surface. According to the processing path file, a femtosecond laser is used to scan the photoresist layer by layer along a predetermined path, and a chain polymerization reaction is induced at the tight focus of the laser through two-photon absorption, thereby realizing the processing of a three-dimensional structure. After processing, the laser-processed sample is immersed in a developing solvent to remove the photosensitive resin that has not undergone polymerization reaction, leaving behind a solidified three-dimensional structure. Secondary curing with UV light is performed according to experimental requirements to improve the mechanical strength and surface stability of the structure. The structure is characterized using an optical microscope and an electron microscope to confirm whether the processed structure meets the design requirements; the morphological characteristics of the cavity structure 1 can be observed using an optical microscope and a scanning electron microscope, such as Figure 5 The cavity structure 1 obtained after processing has the structural features of a central cavity 101 and a plurality of through holes 102 .

[0040] Step 2: A closed structure 2 is formed on the outer surface of the cavity structure 1 around the axial direction of the cavity structure 1 by laser direct writing technology. The closed structure 2 is attached to the outer surface of the cavity structure 1 and closes several through holes 102 at the same time. The width of the closed structure 2 needs to be slightly larger than the through hole 102 to achieve the blocking of the through hole 102.

[0041] Specifically, the closed structure 2 is made of acrylate-based photoresist IP-S, which covers and closes the through hole 102 to form a closed and sealed cavity structure 1. The thickness of the closed structure used to seal the PDMS film cavity structure is 2 μm. When using a 20x objective lens (NA0.8) for processing, the laser power is 32.5 mW, the scanning speed is 100 mm / s, the slice filling line spacing is 300 nm, and the scanning layer spacing is 500 nm. Figure 5 By comparing the microscopic optical and electron microscope images before and after processing, it is confirmed whether the closed structure 1 after molding has indeed filled and blocked the through hole 102 to form an overall composite material structure; at this time, the air layer in the internal cavity 101 will appear brightly colored under an optical microscope for easy judgment. The closed structure 2 reduces the time and alignment difficulty of processing and blocking each through hole 102 separately, thereby improving the efficiency of the overall structure processing and the blocking success rate.

[0042] exist Figure 1In a preferred embodiment shown, in step 1, after the cavity structure 1 is formed, a surface treatment is performed on the surface of the cavity structure 1 where the through hole 102 is opened, and a modified layer 3 is formed. The function of the modified layer 3 is to improve the adhesion of the outer surface of the cavity structure 1, thereby improving the connection strength between the closed structure 2 and the cavity structure 1. The modified layer 3 is a layer of physical deposition coating, so it can be processed using physical vapor deposition technology; physical vapor deposition technology is to convert materials from solid to vapor by physical methods, and then condense on the substrate to form a thin film. The modified layer 3 can use a deposited film of materials such as indium tin oxide (ITO), titanium oxide (TiO2), silicon oxide (SiO2) or gold. The chemical surface modification uses a solution immersion method to control the surface hydrophilicity and hydrophobicity of the formed structure, and a silane coupling agent is used to improve the surface adhesion of the polymer. The silane coupling agent is a silane reagent of the type of trimethoxysilane, triethoxysilane, triisopropoxysilane, etc., such as methyl acrylate trimethoxysilane, vinyl triethoxysilane or methyl isoacrylate triisopropoxysilane.

[0043] exist Figure 1 In a preferred embodiment shown, the thickness of the modified layer 3 is 5 to 50 nm. Specifically, the present invention uses a physical vapor deposition method based on magnetron sputtering to deposit an ITO film on the surface of the cavity structure 1 to form a modified layer 3. Since PDMS is a hydrophobic material, it is difficult to perform secondary laser direct writing processing of other structures on the surface of the cavity structure 1 made of the formed PDMS. The ITO film usually has a high surface energy and hydrophilicity. After it is plated on the PDMS surface, the surface of the PDMS structure can show strong hydrophilicity. At the same time, the ITO film can be used as a reflective interface to improve the resolution of the spectrum. During the magnetron sputtering process, high-purity argon gas is used as the working gas, and a DC power supply forms a voltage difference between the target material and the substrate. The argon ions are accelerated by the electric field and collide with the target surface, sputtering indium tin oxide from the target surface and depositing it on the opposite optical fiber surface to form a thin film. The process parameters used in this paper are: DC power supply power is set to 80W, working voltage is 335V, working current is 233mA, argon gas flow rate is 10SCCM, and coating time is 5min. An ITO metal film with a thickness of about 5nm is deposited on the surface of the target PDMS microcavity structure, such as Figure 5 As shown, the thickness of the modified layer 3 is adjusted according to the design requirements of the cavity structure 1 of different types and different preparation materials. After the modified layer 3 is formed, the color characteristic change of the cavity structure 1 can be observed through an optical microscope. The surface of the PDMS cavity structure 1 after coating presents thin film interference color, such as Figure 5 as shown in (b).

[0044] exist Figure 1In a preferred embodiment shown, in step 2, after the closed structure 2 is formed, the outer surfaces of the cavity structure 1 and the closed structure 2 are subjected to surface treatment and a reinforcement layer 4 is formed, and the reinforcement layer 4 improves the sealing of the cavity structure 1. The formation of the reinforcement layer 4 can be achieved by depositing a coating layer or attaching a thin film layer. The deposition coating method uses physical or chemical deposition to deposit the reinforcement layer 4 on the surface of the micro-nano cavity structure 1; a metal or metal oxide layer is used to achieve good chemical stability and sealing. The reinforcement layer 4 is attached by thermal spraying or coating packaging methods to form a uniform polymer layer on the surface of the cavity structure 1, and the polymer is used to fill the tiny gap between the contact surface of the closed structure 2 and the cavity structure 1, thereby providing good sealing. By modifying or coating the surface of the micro-nano cavity structure 1, the adhesion of the cavity structure 1 to different interfaces can be improved, thereby providing an effective anti-liquid intrusion design for the micro-nano cavity structure 1.

[0045] Specifically, a hydrogel coating encapsulation method can be used to form a gel coating as a reinforcement layer 4 on the surface of the cavity structure 1, and the surface gel structure is used to fill the tiny gaps of the molded structure, thereby providing better sealing. The hydrogel material used is polyethylene glycol diacrylate (PEGDA), and 0.1%wt of methylene blue is doped in the gel as a photoinitiator. The PEGDA solution is spin-coated to form a film with a thickness of 5 μm, and a hydrogel film is formed after UV photopolymerization. The formed hydrogel is then covered on the surface of the blocked cavity structure 1 to form a micro-nano cavity structure 1 encapsulated by the reinforcement layer 4 of the hydrogel coating.

[0046] exist Figure 3 In a preferred embodiment shown, the shapes and inner diameters of the plurality of through holes 102 are different. By optimizing the structure of the through holes 102 on the surface of the cavity structure 1, the surface micropores of the cavity structure 1 are designed to be composed of through holes 102 of different sizes and structures, and the surface tension of the solution is controlled by matching the structures and sizes of the different through holes 102, so that the cavity structure 1 can resist liquid intrusion by utilizing the surface tension of the liquid.

[0047] exist Figure 3 In a preferred embodiment shown, the through hole 102 is polygonal or elliptical, preferably square, circular, or triangular, preferably such that the minimum tension angle of the liquid surface is greater than the minimum angle at which the liquid enters the cavity 101 .

[0048] exist Figure 3 In a preferred embodiment shown, the inner diameter of the through hole 102 is not greater than 10 μm, otherwise it is difficult to meet the requirement of the minimum tension angle of the liquid surface.

[0049] exist Figure 2In a preferred embodiment shown, the outer contour of the cavity structure 1 is a column or a sphere. The cavity 101 can also be designed to be square, circular or any geometric shape; when the cavity structure 1 is a column, it is beneficial to design the height of the air layer of the cavity 101 inside it to be adjustable according to needs.

[0050] exist Figure 2 In a preferred embodiment shown, when the cavity structure 1 is in the shape of a column, one end of the cavity structure 1 along its axial direction is an end face, the wall surface of the cavity structure 1 surrounding its axial direction is an outer peripheral wall, and a plurality of through holes 102 are evenly arranged on the end face or the outer peripheral wall. The annularly distributed through holes 102 can enhance the structural symmetry and structural strength of the cavity structure 1.

[0051] exist Figure 8 and Fig. 9 In a preferred embodiment shown, the surface to be molded is the end face of the optical fiber of the optical fiber sensor, and the micro-nano cavity structure 1 is used to detect the physical signal. The optical fiber sensor is a micro-detector based on the principle of interference or resonance. By processing different types of micro-nano cavity structures 1, the detection capability of different physical signal changes, such as temperature, pressure, flow rate and sound waves, etc., can be realized; for example, the sensor based on the interference effect detects the change of the interference fringes to detect the change of the tiny physical quantity, such as pressure, temperature, flow rate and sound waves, etc.; or, the sensor based on the resonance effect detects the change of the resonant wavelength to detect the change of the environment. The sensitivity of the sensor is related to the thickness of the thin film cavity 101. In addition, a focusing lens can be integrated on the surface of the cavity structure 1 for collecting the detection signal to enhance the detection sensitivity and test stability of the detection signal; or a signal amplifier can be integrated on the surface of the cavity structure 1 to enhance the contrast of the detection signal.

[0052] Specifically, this embodiment provides a use of a micro-nano cavity structure 1 for an optical fiber sensor, and a sensor working method based on the interference principle, such as Figure 8 As shown in (a), combined with Figure 7, the light Iin emitted by the light source S301 is transmitted to the end face of the optical fiber after passing through the circulator S302, where it is refracted and reflected. The light source is emitted from the end face of the optical fiber, and the end face of the optical fiber forms the first reflection surface S303 of the FP interference cavity and forms reflected light I1; the transmitted part of the light beam reaches the second reflection surface S304 and is reflected to form reflected light I2. The light beam undergoes multiple reflections and transmissions in the FP cavity, and I1 and I2 interfere with each other on the return path to form an interference waveform. The circulator then transmits the output light Iout formed after the interference to the detector S305 for analysis. When the signal to be measured changes and causes the structural parameters of the FP cavity to change, such as the optical thickness of the cavity or the effective refractive index of the medium in the cavity, the phase difference between I1 and I2 will change, resulting in a Δλ shift in the interference spectrum. This shift is detected and analyzed by the detector S305, thereby obtaining information about the detection signal, such as Figure 8 As shown in (b). By comparing the difference in sensing signal stability between the unblocked structure and the blocked structure of the sensor of this embodiment, it can be found that: when the cavity structure 1 is open, water will enter the cavity 101 during the liquid environment measurement, causing the refractive index in the cavity 101 to change; at the same time, the existence of the water interface will produce disturbances, causing the spectral signal to shift, affecting the detection stability. After the cavity structure 1 is sealed, an air layer is formed in the FP interferometer cavity, and the internal medium of the cavity 101 does not change after being immersed in the solution, thereby improving the working stability of the detector. Fig. 9 As shown in (a), the reflection spectrum of the open cavity structure 1 in the water environment has a large random shift, and the wavelength change of the interference spectrum trough is 0.84nm; in contrast, Fig. 9 As shown in (b), the spectrum stability of the cavity structure 1 after plugging is significantly better, and the wavelength change of the interference spectrum trough is only 0.06nm. Therefore, the multi-step laser direct writing and surface treatment process proposed in the present invention can effectively improve the stability of the optical fiber sensor working underwater.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for forming a micro-nano cavity structure, characterized in that: The following steps are involved: Step 1: forming a cavity structure (1) on a surface to be formed by laser direct writing technology, wherein a cavity (101) is provided inside the cavity structure (1), and a plurality of through holes (102) are provided on the surface of the cavity structure (1), wherein the through holes (102) are connected between the cavity (101) and the external environment; Step 2: forming a closed structure (2) on the outer surface of the cavity structure (1) by laser direct writing technology; the closed structure (2) is attached to the outer surface of the cavity structure (1); and the closed structure (2) simultaneously closes a plurality of through holes (102).

2. The method for forming a micro-nano cavity structure according to claim 1, characterized in that: In the step 1, after the cavity structure (1) is formed, a surface treatment is performed on the surface of the cavity structure (1) where the through hole (102) is opened, and a modified layer (3) is formed, wherein the modified layer (3) improves the adhesion of the outer surface of the cavity structure (1).

3. The method for forming a micro-nano cavity structure according to claim 3, characterized in that: The thickness of the modified layer (3) is 5 to 50 nm.

4. The method for forming a micro-nano cavity structure according to claim 1, characterized in that: In the second step, after the closed structure (2) is formed, surface treatment is performed on the outer surfaces of the cavity structure (1) and the closed structure (2) to form a reinforcement layer (4), wherein the reinforcement layer (4) improves the sealing performance of the cavity structure (1).

5. The method for forming a micro-nano cavity structure according to claim 1, characterized in that: The shapes and inner diameters of the plurality of through holes (102) are different.

6. The method for forming a micro-nano cavity structure according to claim 5, characterized in that: The through hole (102) is polygonal or elliptical.

7. The method for forming a micro-nano cavity structure according to claim 5, characterized in that: The inner diameter of the through hole (102) is no greater than 10 μm.

8. The method for forming a micro-nano cavity structure according to claim 1, characterized in that: The outer contour of the cavity structure (1) is column-shaped or spherical.

9. The method for forming a micro-nano cavity structure according to claim 8, characterized in that: When the cavity structure (1) is in the shape of a column, one end of the cavity structure (1) in the vertical direction of the surface to be formed is an end face, the wall surface of the cavity structure (1) in the vertical direction surrounding the surface to be formed is an outer peripheral wall, and the plurality of through holes (102) are arranged on the end face or on the outer peripheral wall.

10. The method for forming a micro-nano cavity structure according to claim 1, characterized in that: The surface to be formed is the optical fiber end face of the optical fiber sensor.

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