A honeycomb disc spring type sensing structure, processing and using method

Abstract

The application belongs to the field of optical fiber device preparation and sensing technology, and discloses a honeycomb disc spring type sensing structure, a processing method and a using method. Based on the polymer spring structure integrated manufactured on the optical fiber end face by the two-photon polymerization 3D printing technology, a sensing basis is provided for realizing high-precision micro stress detection. The polymer probe with a width less than 10 μm realizes the stress detection function in the micro-nano area, and the light curing processing precision of the structure can be realized by adjusting a series of parameters, such as laser intensity, scanning speed and cutting layer gap. The experimental results show that the sensing structure can realize high-sensitivity micro stress or strain sensing demodulation in the range of 100 με-300 με, and can keep the structure stable and realize repeated detection. According to the user requirements, the sensing structure suitable for various micro stress and strain ranges can be manufactured by adjusting the structure parameters.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber device preparation and sensing technology, and in particular to a honeycomb disc spring type sensing structure, and a processing and use method thereof. Background Art

[0002] Since the advent of the first fiber optic sensor, its application has expanded from optical networks to various sensing fields. Fiber optic sensors offer the advantage of electromagnetic interference resistance, making them suitable for applications such as high-voltage power grids and motor testing. The silicon-based materials used in optical fibers provide improved insulation and safety, which is crucial for environments such as oil platforms and nuclear equipment. Fiber optic sensors are also corrosion-resistant and have a long service life. Furthermore, the miniaturization and flexibility of optical fibers make complex environments and distributed long-distance detection possible. In recent years, advances in sensing technology have led to the emergence of fiber optic sensors with multi-parameter compatibility and high-speed response, laying the foundation for sensing applications in even more fields. Fabry-Perot fiber optic sensors have attracted much attention for their miniaturization, ultra-high sensitivity, and excellent environmental robustness. Two-photon polymerization 3D printing technology is a process with nanometer-level precision. Its core technology lies in maximizing the freedom of optical design, material functionality, and preparation efficiency. The micro-nano Fabry-Perot sensing structure manufactured on the end face of the optical fiber through this technology has a micron-level volume and a highly flat optical reflection surface. The excellent spectral quality brings sensitive spectral demodulation accuracy, providing underlying technical support for the next generation of biomedical testing, industrial Internet, and extreme environment monitoring.

[0003] This invention proposes a honeycomb disc spring sensor structure, its processing, and its use. Fabricated using a two-photon polymerization 3D printing process, the sensor is integrated onto the end face of a single-mode optical fiber. The resulting micro-nano probe structure is suitable for microstress detection in complex environments. The stress magnitude and range of this structure can be adjusted by adjusting a series of parameters, such as the spring sidewall inclination angle, the honeycomb aperture size, and the spring structure height. The structure offers advantages such as ultra-high sensitivity and an ultra-low stress detection limit. Summary of the Invention

[0004] The present invention solves the problem that current optical fiber sensors have difficulty in detecting tiny stresses and have low sensitivity. It proposes a honeycomb disc spring sensing structure, processing and use method. It is manufactured in an integrated manner on the end face of a single-mode optical fiber. A micro-nano probe is designed on the top of the spring. Detection and demodulation are achieved through the influence of stress on the length of the microcavity. The stress detection limit is low and the sensitivity is ultra-high.

[0005] The technical solution of the present invention is as follows: a honeycomb disc spring type sensing structure is integrally manufactured on the end face of a single-mode optical fiber, the main structure of which is a disc spring, forming a disc spring type Fabry-Perot microcavity; a micro-nano probe is installed on the top of the disc spring.

[0006] The disc spring has a height of 50 μm-60 μm, and an included angle between the side wall of the disc spring and the end face of the single-mode optical fiber is 57°-63°.

[0007] The included angle between the side wall of the disc spring and the end face of the single-mode optical fiber is 60°.

[0008] The side wall of the disc spring is provided with a plurality of evenly distributed equilateral hexagonal honeycomb hollow holes, the longest diagonal of the equilateral hexagonal honeycomb hollow holes is 7.5 μm, and the center spacing between adjacent equilateral hexagonal honeycomb hollow holes is 10 μm-12 μm.

[0009] The center distance between adjacent equilateral hexagonal honeycomb hollow holes is 1.5 times the longest diagonal of the equilateral hexagonal honeycomb hollow holes.

[0010] The disc spring is manufactured based on a two-photon polymerization 3D printing process.

[0011] The micro-nano probe has a length of 10 μm-12 μm and a width of 3 μm-4 μm at the tip; the material of the micro-nano probe is a polymer material that is resistant to electromagnetic interference and corrosion.

[0012] A method for processing a honeycomb disc-shaped spring-type sensing structure comprises the following steps: removing the coating of a single-mode optical fiber and cleaning the end face; fixing the single-mode optical fiber on an optical fiber fixture; dropping photoresist on an objective lens; the image at the objective lens is deflected and transmitted through a refractive prism; filtering through an aperture; and then focusing on a CCD image sensor; connecting a computer to the CCD image sensor and a laser; under the guidance of a real-time image on the computer, moving the optical fiber fixture to continuously bring the objective lens closer to and focus on the end face of the single-mode optical fiber, and immersing the end face of the single-mode optical fiber in the photoresist, thereby completing the preliminary focusing preparation work; when the light curing process begins, the laser light emitted by the laser is emitted. The laser beam is adjusted in diameter by a beam expander, deflected by a plane mirror, propagated through a refracting prism, and converged on the end face of a single-mode optical fiber held by a fiber clamp under the focusing action of an objective lens; a computer identifies and processes the designed three-dimensional model, and the laser beam is scanned to cure the photoresist layer by layer to form a disc spring as a whole. The computer controls the laser exposure based on the three-dimensional model, and simultaneously forms equilateral hexagonal honeycomb hollow holes and disc springs; after manufacturing is completed, the single-mode optical fiber is removed and placed in a propylene glycol methyl ether acetate solution for 10-15 minutes to dissolve the uncured photoresist, and then allowed to stand in the air to complete the processing.

[0013] The Young's modulus of the photoresist is 1.5 GPa and the density is 1.26 g / cm 3 , Poisson's ratio is 0.3.

[0014] A method for using a honeycomb disc-shaped spring-type sensing structure comprises: fixing a single-mode optical fiber of the honeycomb disc-shaped spring-type sensing structure on an optical fiber fixture, with the honeycomb disc-shaped spring-type sensing structure extending 2 cm from the optical fiber fixture; establishing a working optical path: using an optical fiber circulator to connect a laser light source, a spectrometer, and the honeycomb disc-shaped spring-type sensing structure; transmitting laser light from the laser light source through the optical fiber circulator, along the core of the single-mode optical fiber, to the honeycomb disc-shaped spring-type sensing structure; and transmitting laser light reflected by the honeycomb disc-shaped spring-type sensing structure back along the original optical path, through the optical fiber circulator, to the spectrometer. When the spectrometer displays a Fabry-Perot interference spectrum, the establishment of the working optical path is complete.

[0015] When in use, first, under the monitoring of a microscope, place the honeycomb disc spring sensor structure close to the object to be measured. When the trough of the interference waveform shown by the spectrometer moves laterally by more than 1nm, it means that the micro-nano probe has contacted the surface of the object, and the working mode is entered at this time. In the working mode, first, a trough is selected as a reference in the 1550nm-1650nm band according to the waveform shape, and the wavelength value corresponding to the trough at this time is recorded. After stress is applied to the object to be measured, the wavelength value of the trough is recorded again. The wavelength change of the trough multiplied by the sensitivity is the measured stress magnitude.

[0016] Unlike traditional helical springs, disc springs offer greater compressive strength and, under repeated compression and stretching strain sensing conditions, provide more repeatable sensing capabilities. The evenly distributed, equilateral hexagonal honeycomb-shaped holes ensure that the reflective surface remains highly parallel to the fiber end face when the microcavity is stressed. Uneven distribution can lead to uneven stress on the sidewalls, tilting the structure, and affecting the propagation of the originally designed optical path.

[0017] Beneficial effects of the present invention:

[0018] 1) The present invention uses a two-photon polymerization 3D printing process to manufacture a sensing structure on the end face of a single-mode optical fiber. This process has strong repeatability and a process accuracy of up to 100 nanometers, which is conducive to the realization of a high-quality optical sensing structure.

[0019] 2) The core structure designed in this invention is a honeycomb disc spring sensor structure, which has the advantages of high spectral quality, low stress detection limit, and high stress sensing sensitivity. The equilateral hexagonal honeycomb hollow holes further enhance the stress sensitivity of the honeycomb disc spring sensor structure.

[0020] 3) A micro-nano probe is designed on the top of the honeycomb disc spring sensing structure, providing a basis for achieving high directivity and detection in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a processing method for manufacturing a honeycomb disc spring sensor structure based on a two-photon polymerization 3D printing process.

[0022] Figure 2 It is a three-dimensional model of the proposed honeycomb disc spring sensing structure.

[0023] Figure 3 It is the reflection interference spectrum of the proposed honeycomb disc spring sensing structure under a pressure of 33μN-100μN.

[0024] Figure 4 is the linear fitting result, and the calculated microstress sensitivity is 4.79μN / nm.

[0025] In the figure: 1-single-mode optical fiber, 2-objective lens, 3-optical fiber clamp, 4-computer, 5-CCD image sensor, 6-aperture, 7-laser, 8-beam expander, 9-plane mirror, 10-refractive prism. DETAILED DESCRIPTION

[0026] In order to make the above objects and advantages more understandable, the present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 2 The figure shows a honeycomb disc spring sensing structure with a disc spring body height of 50μm and a 60° angle between the disc spring sidewall and the end face of the single-mode fiber. It is worth noting that when the angle between the disc spring sidewall and the end face of the single-mode fiber is 50°, the risk of the honeycomb disc spring sensing structure failing to return to its original shape after being squeezed increases, with a probability of approximately 10%. When the angle is 70°, the linear fit microstress sensing sensitivity drops significantly by more than 30%. Therefore, the angle between the disc spring sidewall and the end face of the single-mode fiber is selected to be 57°-63°, with 60° being the preferred angle.

[0028] The polymer micro-nano probe is 10 μm long and 3 μm wide at its narrowest point. The longest diagonal of the equilateral hexagonal honeycomb hollow holes on the side wall is 7.5 μm, and the center spacing between adjacent equilateral hexagonal honeycomb hollow holes is 10 μm. The accuracy of the honeycomb disc spring sensor structure under this size design is as follows: Figure 4 As shown, it is 4.79μN / nm.

[0029] Experimental results show that when the center-to-center spacing of adjacent equilateral hexagonal honeycomb holes is 1.2 times the longest diagonal of the holes, the structure becomes unstable, with a 60% probability of the honeycomb disc spring sensor structure collapsing after manufacturing. When the center-to-center spacing of adjacent equilateral hexagonal honeycomb holes is 1.8 times the longest diagonal of the holes, the linear fit microstress sensing sensitivity decreases by at least 20%. Preferably, the center-to-center spacing of adjacent equilateral hexagonal honeycomb holes is designed to be 1.5 times the longest diagonal of the holes.

[0030] The specific implementation process of the present invention is as follows Figure 1 As shown, the details are as follows:

[0031] First, remove the coating from a single-mode fiber 1 (core diameter 8.2μm, cladding diameter 125μm), clean the end face, and secure it to the fiber fixture 3. Apply photoresist to the objective lens 2, applying just enough to completely cover the entire surface. The CCD image sensor 5 transmits an image of the surface of the objective lens 2 to the computer 4. Guided by the real-time image, slowly move the fiber fixture 3, bringing the cleaned single-mode fiber 1 closer to the objective lens. During this movement, ensure that the single-mode fiber 1 is aligned with the objective lens 2 in both the x- and y-axis directions. Then, slowly move the fiber fixture 3 perpendicular to the objective lens 2. Immerse the single-mode fiber 1 in the photoresist and then advance it further, monitoring the computer 4 display. Focus is determined by observing the sharpness of the edge of the single-mode fiber 1's end face. To confirm that the fiber end face has reached the focal plane of the objective lens, briefly release the laser exposure. Focus is verified by observing the intensity of the laser at two points. The honeycomb disc spring sensor structure was designed and 3D-modeled on a computer (the overall length and width of the disc spring should be approximately the same as the 125μm diameter of the single-mode optical fiber). The 3D model was saved in .stl format and then imported into Describe software for processing. Describe software slices the 3D model layer by layer and automatically plans the laser scanning path for efficient photocuring. To balance efficiency and accuracy, a 300nm layer spacing was used. The pre-processed 3D file guides the laser exposure of the characteristic spaces on the fiber end face, enabling 3D printing of arbitrary shapes. The structure is then placed in a propylene glycol methyl ether acetate solution for approximately 10 minutes to dissolve the uncured photoresist, and then allowed to stand in air to complete the processing.

[0032] When using the manufactured honeycomb disc spring-type sensing structure to measure stress, the working optical path must first be connected: a fiber optic circulator is used to connect a laser light source (wavelength range 470nm-2400nm), a spectrometer, and the honeycomb disc spring-type sensing structure. Laser light is emitted from the laser light source and transmitted through the fiber optic circulator along the core of single-mode optical fiber 1 to the honeycomb disc spring-type sensing structure. The laser light reflected by the honeycomb disc spring-type sensing structure returns along the original optical path and is transmitted through the fiber optic circulator to the spectrometer. When the spectrometer displays a Fabry-Perot interference spectrum, it indicates that the working optical path is complete.

[0033] When starting the measurement, first, under the microscope with a magnification of at least 10 times, slowly move the honeycomb disc spring sensor structure close to the object to be measured to avoid damage to the micro-nano probe and spring structure due to impact. When the trough of the interference waveform shown by the spectrometer moves more than 1nm laterally, it means that the honeycomb disc spring sensor structure is in contact with the surface of the object, and the working mode is entered. In the working mode, first select a trough in the 1550nm-1650nm band as a reference based on the waveform shape, and then compare it with the Figure 3 The spectral relationship between trough wavelength and microstress shown in the figure provides a rough estimate of the microstress range based on the location of the spectral trough. For example, when the interference trough is between the first and second troughs on the left, the measured microstress on the surface is between 33μN and 50μN. Specifically, using the trough corresponding to a wavelength of 1587nm as a reference, as stress increases, the trough moves to 1600nm, a wavelength change of 13nm. Multiplying this by 4.79μN / nm, the stress change is 62.3μN.

Claims

1. A honeycomb disc spring type sensing structure, characterized in that: The disc spring is manufactured in an integrated manner at the end face of a single-mode optical fiber. The main structure is a disc spring, which forms a disc spring-type Fabry-Perot microcavity. A micro-nano probe is installed on the top of the disc spring. The angle between the side wall of the disc spring and the end face of the single-mode optical fiber is 57°-63°. The side wall of the disc spring is provided with a number of evenly distributed equilateral hexagonal honeycomb hollow holes. The disc spring is manufactured based on the two-photon polymerization 3D printing process.

2. The honeycomb disc spring type sensing structure according to claim 1, characterized in that: The disc spring has a height of 50 μm-60 μm.

3. The honeycomb disc spring type sensing structure according to claim 2, characterized in that: The included angle between the side wall of the disc spring and the end face of the single-mode optical fiber is 60°.

4. The honeycomb disc spring type sensing structure according to claim 1, characterized in that: The longest diagonal of the equilateral hexagonal honeycomb hollow holes is 7.5 μm, and the center distance between adjacent equilateral hexagonal honeycomb hollow holes is 10 μm-12 μm.

5. The honeycomb disc spring type sensing structure according to claim 4, characterized in that: The center distance between adjacent equilateral hexagonal honeycomb hollow holes is 1.5 times the longest diagonal of the equilateral hexagonal honeycomb hollow holes.

6. The honeycomb disc spring type sensing structure according to claim 1, characterized in that: The micro-nano probe has a length of 10 μm-12 μm and a width of 3 μm-4 μm at the tip; the material of the micro-nano probe is a polymer material that is resistant to electromagnetic interference and corrosion.

7. A method for processing the honeycomb disc spring type sensor structure according to any one of claims 1 to 6, characterized in that: The coating of the single-mode optical fiber (1) is removed and the end face is cleaned. The single-mode optical fiber (1) is fixed on the optical fiber clamp (3); photoresist is dropped on the objective lens (2), and the image at the objective lens (2) is deflected and transmitted through the refractive prism (10), filtered by the aperture (6), and focused on the CCD image sensor (5); the computer (4) is connected to the CCD image sensor (5) and the laser (7) respectively; under the guidance of the real-time image of the computer (4), the objective lens (2) is continuously approached and focused on the end face of the single-mode optical fiber (1) by moving the optical fiber clamp (3), and the end face of the single-mode optical fiber (1) is immersed in the photoresist, completing the preliminary focusing preparation work; when the light curing process begins, the laser (7) outputs The emitted laser beam is adjusted in diameter by a beam expander (8), deflected by a plane reflector (9), and propagated through a refracting prism (10). The beam is focused by an objective lens (2) and converges on the end face of a single-mode optical fiber held by an optical fiber clamp (3); a computer (4) identifies and processes the designed three-dimensional model, and the laser beam is subjected to a scanning operation to solidify the photoresist layer by layer to form a disc spring as a whole. The computer (4) controls whether the laser is exposed according to the three-dimensional model, and simultaneously forms an equilateral hexagonal honeycomb hollow hole and a disc spring; after the manufacturing is completed, the single-mode optical fiber (1) is removed and placed in a propylene glycol methyl ether acetate solution for 10-15 minutes to dissolve the uncured photoresist, and then left to stand in the air to complete the processing.

8. The processing method according to claim 7, characterized in that: The Young's modulus of the photoresist is 1.5 GPa and the density is 1.26 g / cm 3 , Poisson's ratio is 0.

3.

9. A method for using the honeycomb disc spring type sensing structure according to any one of claims 1 to 6, characterized in that: A single-mode optical fiber (1) with a honeycomb disc spring-type sensing structure is fixed on an optical fiber clamp (3), and the honeycomb disc spring-type sensing structure extends 2 cm from the optical fiber clamp (3); Build a working optical path: The optical fiber circulator connects the laser light source, the spectrometer and the honeycomb disc spring type sensor structure; the laser is emitted from the laser light source through the optical fiber circulator, and is transmitted along the core of the single-mode optical fiber (1) to the honeycomb disc spring type sensor structure. The laser reflected by the honeycomb disc spring type sensor structure returns along the original optical path and is transmitted to the spectrometer through the optical fiber circulator. When the spectrometer displays a Fabry-Perot interference spectrum, it indicates that the construction of the working optical path is completed; When in use, first, under the monitoring of a microscope, place the honeycomb disc spring sensor structure close to the object to be measured. When the trough of the interference waveform shown by the spectrometer moves laterally by more than 1nm, it means that the micro-nano probe has contacted the surface of the object, and the working mode is entered at this time. In the working mode, first, a trough is selected as a reference in the 1550nm-1650nm band according to the waveform shape, and the wavelength value corresponding to the trough at this time is recorded. After stress is applied to the object to be measured, the wavelength value of the trough is recorded again. The wavelength change of the trough multiplied by the sensitivity is the measured stress magnitude.

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