Self-adhesive flexible optical fiber micro-displacement sensor and preparation method thereof

Abstract

The application discloses a self-adhesive flexible optical fiber micro-displacement sensor and a preparation method thereof, which is prepared by embedding a fiber Bragg grating (FBG) into a hydrogel matrix. The application has a small detection range, is suitable for micro-scale monitoring, and can be attached to the surface of an object without additional adhesive. The self-adhesive flexible optical fiber micro-displacement sensor with different thicknesses of hydrogel matrix can be prepared according to actual needs.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and in particular to a self-adhesive flexible fiber optic micro-displacement sensor and its preparation method. Background Technology

[0002] Displacement sensors play a crucial role in various fields such as flexible wearable monitoring, ultra-precision manufacturing, aerospace, semiconductors, and military security and defense. Currently, based on their underlying conversion mechanisms, displacement sensors can be divided into two main categories: electrical and optical. Among them, fiber optic displacement sensors, which use light guiding technology for measurement, have attracted much attention due to their unique advantages, such as light weight, high sensitivity, strong flexibility, corrosion resistance, electromagnetic interference resistance, and small size.

[0003] In recent years, various fiber optic displacement sensors with different structures have emerged, such as FBG, Fabry-Perot interferometers (FPI), and U-shaped fibers. Among fiber optic structures, the typical FBG, which realizes optical microstructures through periodic refractive index modulation, is often used as a fiber optic displacement sensor for displacement detection due to its extremely high sensitivity to displacement. However, the inherent mechanical rigidity of traditional silicon-based fibers fundamentally limits their practicality in applications requiring microscale dynamic measurements.

[0004] To address this challenge in microscale displacement detection using fiber optic sensors, high spatial resolution is required. Therefore, enhancing the flexibility of the fiber optic sensing region is essential for accurate detection of localized deformations. Established methods, such as melt tapering or etching, are commonly used to fabricate microscale displacements and enhance flexibility, thereby reducing the diameter of the fiber optic sensing interface. Recently, researchers have focused on applying polymer coatings (such as PDMS, polyester, PVA, PVC layers, or hydrogels) to the fiber optic sensing interface to improve its durability. Subsequently, displacement demodulation was achieved by monitoring wavelength shifts, polarization state changes, or phase variations.

[0005] The integration of flexible materials with fiber optic waveguides not only enables precise control of sensor diameter but also provides high flexibility. As a shielding layer covering the fiber surface, this design effectively enhances the sensor's anti-interference capability. Furthermore, the flexible substrate acts as a crucial interlayer between the fiber and the object being measured, ensuring a tight fit between the sensor and the substrate. However, traditional fiber optic sensors often use adhesives or transparent tapes for bonding, which not only severely affect sensor sensitivity but also present complex manufacturing processes. Currently, flexible fiber optic displacement sensors are mainly manufactured using molding and curing processes, with thermosetting polydimethylsiloxane (PDMS) as the substrate. While these sensors can be used for displacement monitoring, they suffer from limitations such as discontinuous manufacturing processes and low sensitivity. To improve manufacturing processes and sensitivity, researchers have begun using thermoplastic materials such as PMMA and polycarbonate. By utilizing the correlation between light intensity and displacement for signal demodulation, these methods have significantly improved the detection performance of fiber optic sensors, achieving a sensitivity as high as 0.03 nm / mm. However, the inherent brittleness of thermoplastic materials makes them prone to breakage during displacement testing, thus limiting their practical application. Therefore, improving the performance of flexible displacement sensors remains crucial.

[0006] Hydrogels, as one-dimensional materials, have been widely used in sensing devices, actuators, optical components, and soft robots due to their excellent adhesion, flexibility, wettability, reactivity, and biocompatibility. Therefore, this technology shows significant application potential in displacement monitoring. For example, electrospinning technology has been used to prepare hydrogel fibers with good uniformity; a hydrogel-based fiber optic strain sensor has a strain variation range of up to 120%, which can be used to monitor human physiological movements; and hydrogel fiber dielectric layers can extend to 200% of their initial state while still capturing the amplitude and velocity of body movements. A hydrogel-based strain sensor exhibits excellent response sensitivity to high-speed, high-frequency motion. However, most research focuses on improving the sensor's sensing characteristics by modifying the hydrogel's properties, but this approach is costly. Summary of the Invention

[0007] Based on the above description, this invention proposes a self-adhesive flexible fiber optic micro-displacement sensor. By embedding a fiber Bragg grating into the encapsulation structure of a hydrogel matrix, it has a small detection range and is suitable for microscale displacement monitoring. This invention has high robustness and can be attached to the surface of an object without additional adhesive.

[0008] The technical solution adopted is: a self-adhesive flexible fiber optic micro-displacement sensor, including an encapsulation matrix and a sensing unit; the encapsulation matrix is ​​a hydrogel matrix with self-adhesion and flexibility; the sensing unit is a fiber Bragg grating; the fiber Bragg grating is embedded inside the hydrogel matrix.

[0009] Preferably, the thickness of the hydrogel matrix is ​​0.3-1 mm.

[0010] Preferably, the hydrogel matrix is ​​a hydrogel precursor made of acrylamide powder, N,N′-methylenebisacrylamide, sodium alginate, and cellulose nanocrystals, which is cured by ultraviolet light using a photoinitiator.

[0011] Preferably, the preparation steps of the hydrogel matrix are as follows: a. Add 0.4-0.5g of acrylamide powder, 1.0-2.0g of N,N′-methylenebisacrylamide and 0.05-0.1g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone sequentially to 0.3-0.5ml of deionized water; b. Stir the mixed solution with a magnetic stirrer to disperse the solution evenly and obtain the first solution; c. Add 0.2-0.5g sodium alginate and 0.15-0.25g cellulose nanocrystals to the first solution, and continue stirring with a magnetic stirrer to obtain the hydrogel precursor.

[0012] Preferably, the fiber Bragg grating is a single-mode fiber prefabricated grating with a center wavelength of 1550±0.3nm, a grating region length of 10mm, and a reflectivity greater than 90%.

[0013] The fabrication method of the self-adhesive flexible fiber optic micro-displacement sensor is as follows: 1) Prepare a polydimethylsiloxane mold with a rectangular cavity and fiber alignment grooves at both ends of the cavity; 2) Place the fiber Bragg grating in the fiber alignment slot so that the fiber Bragg grating is located at the center of the cavity; 3) Inject the hydrogel precursor into the polydimethylsiloxane mold to completely embed the fiber Bragg grating into the hydrogel; 4) Curing is performed under ultraviolet light to allow the hydrogel to solidify; 5) Demolding yields a self-adhesive flexible fiber optic micro-displacement sensor.

[0014] Preferably, the curing time in 4) is 3-5 minutes.

[0015] Preferably, the dimethylsiloxane mold is 35-45mm long, 8-12mm wide, and 0.3-1mm deep.

[0016] Preferably, the diameter of the fiber alignment slot is 0.2 mm.

[0017] Preferably, the sensor is used for microscale displacement measurement in the range of 0-0.1 mm, with a sensitivity of not less than 0.886 nm / mm and a detection limit of not more than 0.02 mm.

[0018] This invention features a small detection range, making it suitable for microscale monitoring, and it can be adhered to object surfaces without the need for additional adhesives. This invention is fabricated by embedding a fiber Bragg grating (FBG) into a hydrogel matrix.

[0019] This invention uses a self-adhesive hydrogel as the encapsulation matrix, achieving a firm bond between the sensor and the measured surface without the need for additional adhesives. This simplifies the usage process and avoids the impact of traditional adhesives on sensor sensitivity. By adjusting the hydrogel thickness (0.3 mm, 0.5 mm, 1 mm), the sensor sensitivity can be controlled. The 1 mm thick sensor achieves a sensitivity of 0.886 nm / mm under micro-displacement conditions, with a detection limit as low as 0.02 mm.

[0020] The hydrogel matrix has good flexibility and optical transparency (average optical transparency is close to 100%), which can effectively transfer the strain caused by displacement and maintain the optical response characteristics of FBG.

[0021] The sensor exhibits good linear response (R² = 0.992) in the micro-displacement range (0.02–0.1 mm), conforms to Hooke's Law, and is suitable for fields with high requirements for micro-scale displacement monitoring, such as aerospace and ultra-precision manufacturing.

[0022] This invention features a simple and low-cost preparation process with good repeatability. The sensor exhibits excellent biocompatibility, allowing for comfortable and stable integration with human skin, and is suitable for continuous displacement monitoring. All materials used in this invention are commercially available reagents, suitable for mass production, and can be widely applied in the field of micro-displacement monitoring. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the self-adhesive flexible optical fiber micro-displacement sensor of the present invention; Figure 2 This is a schematic diagram of the self-adhesive flexible fiber optic micro-displacement sensor of the present invention being fixed in a stretching machine; Figure 3 For based on Figure 2 Force-displacement curve; Figure 4 This is a peeling experiment between the hydrogel and the skin interface; where a is a diagram of the apparatus and b is a graph of the force process of the hydrogel. Figure 5 A testing system for self-adhesive flexible fiber optic micro-displacement sensors; Figure 6The graph shows the response of a self-adhesive flexible fiber optic micro-displacement sensor to micro-displacements (0.02-0.1 mm). Figure a shows the spectral response of the sensor with a hydrogel thickness of 0.3 mm under different micro-displacements; Figure b shows the spectral response of the sensor with a hydrogel thickness of 0.5 mm under different micro-displacements; Figure c shows the spectral response of the sensor with a hydrogel thickness of 1 mm under different micro-displacements; and Figure d shows the corresponding sensitivity of the sensor with different hydrogel thicknesses. Figure 7 Figure 1 shows the response of a self-adhesive flexible fiber optic micro-displacement sensor to moderate displacement (0.2-4 mm). Figure 2a shows the spectral response of a sensor with a hydrogel thickness of 0.3 mm as the moderate displacement increases; Figure 3b shows the spectral response of a sensor with a hydrogel thickness of 0.5 mm as the moderate displacement increases; Figure 4c shows the spectral response of a sensor with a hydrogel thickness of 1 mm as the moderate displacement increases; and Figure 5d shows the corresponding sensitivity of sensors with different hydrogel thicknesses. Figure 8 The graph shows the relationship between sensor sensitivity and hydrogel thickness under different displacement conditions. Detailed Implementation

[0024] The technical solution of the present invention is described in detail below. The embodiments of the present invention are for illustrative purposes only, and the scale of the structure is not limited by the embodiments.

[0025] refer to Figures 1 to 8 , Example 1: This example prepares a self-adhesive flexible fiber optic micro-displacement sensor with a hydrogel matrix thickness of 0.3 mm. The self-adhesive flexible fiber optic micro-displacement sensor includes an encapsulation matrix 2 made of self-adhesive hydrogel and a fiber Bragg grating 1; the fiber Bragg grating 1 is embedded in the hydrogel matrix 2; the hydrogel matrix is ​​formed by curing a hydrogel precursor and has a thickness of 0.3 mm; the center wavelength of the fiber Bragg grating is 1550 nm and the grating region length is 10 mm.

[0026] The preparation of the hydrogel precursor was carried out under standard atmospheric pressure and 20°C, and the steps are as follows: a. Add 0.35g of acrylamide powder, 1.5g of N,N′-methylenebisacrylamide, and 0.08g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone sequentially to 0.35ml of deionized water; b. Stir the mixed solution with a magnetic stirrer for 15 minutes to ensure uniform dispersion and obtain the first solution; c. Add 0.3g sodium alginate and 0.21g cellulose nanocrystals to the first solution, and continue stirring with a magnetic stirrer for 2 hours to obtain the hydrogel precursor.

[0027] Mold preparation: A rectangular mold model with dimensions of 40 mm × 10 mm × 0.3 mm was designed using SolidWorks software. A negative mold was manufactured using a 3D printer. The polydimethylsiloxane base agent and curing agent were mixed at a ratio of 10:1 and injected into the negative mold. The mixture was cured in a 60°C oven for 2 hours. After demolding, the polydimethylsiloxane mold was obtained. Alignment grooves with a diameter of 0.2 mm were provided at both ends of the mold.

[0028] A method for fabricating a self-adhesive flexible fiber optic micro-displacement sensor, comprising the following steps; 1) Prepare a polydimethylsiloxane mold with dimensions of 40 mm (length) × 10 mm (width) × 0.3 mm (height), and aligning grooves with a diameter of 0.2 mm are provided at both ends of the cavity; 2) Place a fiber Bragg grating with a center wavelength of 1550 nm and a grating region length of 10 mm in the fiber alignment slot to ensure that the grating region is located at the center of the mold cavity; 3) Inject the hydrogel precursor into the polydimethylsiloxane mold to completely embed the fiber Bragg grating into the hydrogel matrix; 4) Curing under a UV lamp (20W, 365nm) for 3 minutes to allow the hydrogel to solidify; 5) Demolding: Separate the sensor from the mold to obtain a self-adhesive flexible fiber optic micro-displacement sensor with a thickness of 0.3 mm.

[0029] Example 2: In this example, a self-adhesive flexible fiber optic micro-displacement sensor with a hydrogel matrix thickness of 0.5 mm is prepared. The self-adhesive flexible fiber optic micro-displacement sensor includes an encapsulation matrix 2 made of self-adhesive hydrogel and a fiber Bragg grating 1. The fiber Bragg grating 1 is embedded in the hydrogel matrix 2. The hydrogel matrix is ​​formed by curing a hydrogel precursor and has a thickness of 0.5 mm. The center wavelength of the fiber Bragg grating is 1550 nm and the grating region length is 10 mm.

[0030] The height of the mold was adjusted to 0.5 mm, that is, the polydimethylsiloxane mold was 40 mm (length) × 10 mm (width) × 0.5 mm (height), and the remaining preparation steps were the same as in Example 1.

[0031] Example 3: In this example, a self-adhesive flexible fiber optic micro-displacement sensor with a hydrogel matrix thickness of 1.0 mm was prepared. The self-adhesive flexible fiber optic micro-displacement sensor includes an encapsulation matrix 2 made of self-adhesive hydrogel and a fiber Bragg grating 1. The fiber Bragg grating 1 is embedded in the hydrogel matrix 2. The hydrogel matrix is ​​formed by curing a hydrogel precursor and has a thickness of 1.0 mm. The center wavelength of the fiber Bragg grating is 1550 nm and the grating region length is 10 mm.

[0032] The height of the mold was adjusted to 1.0 mm, that is, the polydimethylsiloxane mold was 40 mm (length) × 10 mm (width) × 1.0 mm (height), and the remaining preparation steps were the same as in Example 1.

[0033] Pull-out and peel tests of hydrogel and optical fiber: This experiment tested the self-adhesive flexible fiber optic micro-displacement sensors prepared in Examples 1, 2, and 3. Tensile tests were used to verify the reliability of the interfacial adhesion between the hydrogels of different thicknesses and the optical fibers. (1) Measure the maximum force F required to pull the optical fiber out of the hydrogel. max To calculate the shear strength of the interface In Formula 1, F max D is the maximum force during stretching and retraction. f and L f These represent the diameter and effective length of the optical fiber embedded in the hydrogel matrix, respectively.

[0034] like Figure 1 , Figure 2 As shown, the free end of the optical fiber of the sensor is held in the upper jaw 4 of the stretching machine. PDMS is wrapped around the upper jaw 4 to prevent the optical fiber from being crushed by the upper jaw, while the hydrogel region is held in the lower jaw 3. Stretching and extraction tests were performed at a speed of 20 mm / min. The tensile force hindering the separation of the hydrogel and the optical fiber was measured, and three average values ​​of the tensile force were determined based on self-adhesive flexible optical fiber micro-displacement sensors with hydrogel heights of 0.3, 0.5, and 1 mm, respectively. Because the optical fiber is well embedded in the hydrogel, it is not completely detached from the hydrogel when it breaks. Therefore, the typical displacement of the stretching machine was set to 12 mm, which is far greater than the currently disclosed displacement value.

[0035] from Figure 3 The force-displacement curves show peak applied forces of 0.09, 0.57, and 0.78 ± 0.01 Newtons, corresponding to shear strengths of... The values ​​were 11.46, 72.61, and 99.36 ± 0.01 kPa, respectively.

[0036] like Figure 4 As shown, the bioadhesion and interfacial toughness between the hydrogel and the skin interface were assessed using an adhesion-peel test according to the 180° peel test standard. The peel test, which evaluates adhesion performance, requires a certain amount of energy to separate the hydrogel from the substrate by a unit area. The interfacial adhesion force or peel toughness (Δ) can be defined as: (2), in formula 2, The maximum force during peeling is given by W, and the width of the hydrogel is given by W. The hydrogels prepared according to Examples 1, 2, and 3 were adhered to a skin-like substrate and peeled off using a stretcher. After three cycles of measurement, the average maximum force was 0.42 Newtons, and the width of the hydrogel was 10 mm. Therefore, the following conclusions were drawn. It is 0.084 Newtons per millimeter.

[0037] like Figure 5 As shown, displacement response is the main performance indicator of a displacement sensor. The self-adhesive flexible fiber optic micro-displacement sensors prepared in Examples 1, 2, and 3 were tested using a detection system. The detection system mainly consists of a broadband light source (BLS), a high-precision micro-displacement platform, an optical spectrum analyzer (OSA), and a computer. During displacement measurement, the hydrogel at both ends of the self-adhesive flexible fiber optic micro-displacement sensor is fixed to the high-precision micro-displacement platform using clamps, and the fiber ends are connected to the BLS and OSA respectively. The high-precision micro-displacement platform is set to a stepping speed of 0.005 mm / pulse. When the platform reaches the target displacement, the device pauses, and the OSA records the corresponding spectrum of the self-adhesive flexible fiber optic micro-displacement sensor, thereby realizing the measurement of displacement response.

[0038] The response of the self-adhesive flexible fiber optic micro-displacement sensor to micro-displacement directly determines its detection limit, and micro-displacement measurement itself places higher demands on sensor performance. To test the detection capability and limit of the self-adhesive flexible fiber optic micro-displacement sensors prepared in Examples 1, 2, and 3 under micro-displacement conditions, a high-precision micro-displacement platform was set with a step size of 0.02 mm. Figure 5 As shown, the responses of the three sensors were measured in the micro-displacement range of 0.02 mm to 0.1 mm.

[0039] Figure 6 As shown, with increasing applied micro-displacement, the reflectance spectra of self-adhesive flexible fiber optic micro-displacement sensors prepared with different hydrogel thicknesses all exhibit a significant redshift. Furthermore, the magnitude of the spectral redshift increases with increasing hydrogel thickness. This phenomenon can be attributed to the micro-deformation of the hydrogel under external displacement, which alters the effective refractive index of the FBG. Repeated tests demonstrate that the sensor possesses good stability and repeatability, confirming the stability of the prepared self-adhesive flexible fiber optic micro-displacement sensor in micro-displacement measurement.

[0040] Linear fitting was performed on the center wavelength and applied strain for the three hydrogel thicknesses, and the measured micro-displacement sensitivities were 0.239 nm / mm, 0.655 nm / mm, and 0.886 nm / mm, respectively, with corresponding coefficients of determination (R²) of 0.997, 0.949, and 0.992. Figure 6As shown in (d), the sensitivity increases with increasing hydrogel thickness, verifying the effectiveness of the designed sensor. The detection limit (LOD) for micro-displacement detection is as low as 0.02 mm.

[0041] Although the deformation of hydrogels under external forces is typically nonlinear, the fabricated hydrogel-based self-adhesive flexible fiber optic micro-displacement sensor exhibits a significant linear response within the tested micro-displacement range, conforming to Hooke's law for linear elastic materials. The study demonstrates that this sensor maintains high sensitivity to micro-displacements even before the nonlinear characteristics of the hydrogel become apparent, laying the foundation for practical micro-displacement monitoring in engineering applications.

[0042] Mid-displacement testing of self-adhesive flexible fiber optic micro-displacement sensors Medium displacement measurement is a common application scenario for displacement sensors. To test the performance of the self-adhesive flexible fiber optic micro-displacement sensors prepared in Examples 1, 2, and 3 under medium displacement conditions, the microstage step size was set to 0.2 mm. Figure 7 As shown, the response characteristics of three sensors were tested in a medium displacement range of 0.2 mm to 4 mm.

[0043] like Figure 7 As shown in (a)-(c), the reflectance spectra of fiber optic sensors with different hydrogel thicknesses exhibit a significant redshift with increasing application of a moderate displacement. However, the redshift amplitude gradually decreases with increasing hydrogel thickness.

[0044] After performing nonlinear binomial fitting on the center wavelength and displacement for three hydrogel thicknesses, the sensitivities under moderate displacement conditions were measured to be 0.012 nm / mm, 0.044 nm / mm, and 0.128 nm / mm, respectively, with corresponding coefficients of determination (R²) of 0.995, 0.993, and 0.989. Figure 7 As shown in (d), the sensitivity increases with increasing hydrogel thickness, confirming the functional effectiveness of the sensor of the present invention. However, the overall sensitivity is still significantly lower than the observation value under micro-displacement conditions.

[0045] This decrease in sensitivity can be attributed to the nonlinear elastic properties of the hydrogel matrix. Under moderate displacement conditions, the hydrogel itself undergoes nonlinear deformation, which in turn induces nonlinear displacement of the embedded optical fiber, leading to a nonlinear change in the effective refractive index of the FBG. Repeated tests show good consistency in the results. Although the sensitivity to moderate displacement is lower than that to micro displacement, the sensor still exhibits reliable and stable performance in moderate displacement measurements.

[0046] like Figure 8As shown, the sensitivity of the hydrogel-based self-adhesive flexible fiber optic micro-displacement sensor is related to the thickness of the hydrogel matrix under different displacement conditions. The sensitivity of the self-adhesive flexible fiber optic micro-displacement sensors prepared in Examples 1, 2, and 3 generally decreases with increasing applied displacement. However, within a specific displacement range, the sensitivity increases with increasing hydrogel thickness. Under micro-displacement measurement conditions (0.02-0.1 mm), the sensor sensitivity reaches a peak of 0.886 nm / mm, indicating that this hydrogel-based sensor has high sensitivity characteristics in micro-displacement measurement.

Claims

1. A self-adhesive flexible fiber optic micro-displacement sensor, characterized in that, It includes an encapsulation matrix and a sensing unit; the encapsulation matrix is ​​a hydrogel matrix with self-adhesion and flexibility; the sensing unit is a fiber Bragg grating; the fiber Bragg grating is embedded inside the hydrogel matrix.

2. The self-adhesive flexible fiber optic micro-displacement sensor according to claim 1, characterized in that, The thickness of the hydrogel matrix is ​​0.3-1 mm.

3. The self-adhesive flexible fiber optic micro-displacement sensor according to claim 1, characterized in that, The hydrogel matrix is ​​a hydrogel precursor made of acrylamide powder, N,N′-methylenebisacrylamide, sodium alginate, and cellulose nanocrystals, which is cured by ultraviolet light using a photoinitiator.

4. The self-adhesive flexible fiber optic micro-displacement sensor according to claims 1 to 3, characterized in that, The preparation steps of the hydrogel precursor are as follows: a. Add 0.4-0.5g of acrylamide powder, 1.0-2.0g of N,N′-methylenebisacrylamide and 0.05-0.1g of 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone sequentially to 0.3-0.5ml of deionized water; b. Stir the mixed solution with a magnetic stirrer to disperse the solution evenly and obtain the first solution; c. Add 0.2-0.5g sodium alginate and 0.15-0.25g cellulose nanocrystals to the first solution, and continue stirring with a magnetic stirrer to obtain the hydrogel precursor.

5. The self-adhesive flexible fiber optic micro-displacement sensor according to claim 1, characterized in that, The fiber Bragg grating is a single-mode fiber prefabricated grating with a center wavelength of 1550±0.3nm, a grating region length of 10mm, and a reflectivity greater than 90%.

6. A method for fabricating a self-adhesive flexible fiber optic micro-displacement sensor as described in any one of claims 1-5, characterized in that, The steps are as follows: 1) Prepare a polydimethylsiloxane mold with a rectangular cavity and fiber alignment grooves at both ends of the cavity; 2) Place the fiber Bragg grating in the fiber alignment slot so that the fiber Bragg grating is located at the center of the cavity; 3) Inject the hydrogel precursor into the polydimethylsiloxane mold to completely embed the fiber Bragg grating into the hydrogel; 4) Curing is performed under ultraviolet light to allow the hydrogel to solidify; 5) Demolding yields a self-adhesive flexible fiber optic micro-displacement sensor.

7. The method for fabricating a self-adhesive flexible fiber optic micro-displacement sensor according to claim 6, characterized in that, The curing time in step 4) is 3-5 minutes.

8. The method for fabricating a self-adhesive flexible fiber optic micro-displacement sensor according to claim 6, characterized in that, The dimethylsiloxane mold is 35-45mm long, 8-12mm wide, and 0.3-1mm deep.

9. The method for fabricating a self-adhesive flexible fiber optic micro-displacement sensor according to claim 6, characterized in that, The diameter of the optical fiber alignment slot is 0.2 mm.

10. The application of the self-adhesive flexible fiber optic micro-displacement sensor according to claims 1-5 in microscale displacement monitoring, characterized in that, The sensor is used for microscale displacement measurement in the range of 0-0.1 mm, with a sensitivity of not less than 0.886 nm / mm and a detection limit of not more than 0.02 mm.

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