Controllable microstructure cantilever beam fiber optic micro force sensor, preparation and detection method

Abstract

This invention discloses a controllable microstructure cantilever beam fiber optic microforce sensor, its fabrication, and a detection method, comprising: a silicon glass insert; a single-mode fiber embedded in the silicon glass insert; a controllable microstructure cantilever beam disposed on one side of the single-mode fiber and on the surface of the silicon glass insert; the end face of the single-mode fiber, the lower surface of the controllable microstructure cantilever beam, and the upper surface of the controllable microstructure cantilever beam resonate to form the reflection spectrum of the fiber optic microforce sensor; the end face of the single-mode fiber and the lower surface of the controllable microstructure cantilever beam form an air microcavity; the lower surface of the controllable microstructure cantilever beam and the upper surface of the controllable microstructure cantilever beam form a polymer microcavity; and the end face of the single-mode fiber and the upper surface of the controllable microstructure cantilever beam form a hybrid microcavity. The novel controllable microstructure cantilever beam probe fiber optic microforce sensor of this invention has a simple structure and advantages such as high sensitivity, high mechanical strength, and ultra-low detection limit.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensor technology, and in particular to a controllable microstructure cantilever beam fiber optic microforce sensor, its preparation and detection methods. Background Technology

[0002] The detection of micro- and nano-new energy is playing an increasingly important role and significance in many engineering applications. With the development of micro- and nanotechnology and biomedical technology, the detection of micro- and nano-new energy will promote the development of fields such as biomedicine, cell biology, molecular chemistry, genetics (DNA), environmental monitoring (bacteria), food industry (microorganisms), and nano-manufacturing.

[0003] Currently, the application of micro / nano Newton force detection technology in various fields is still in the experimental research stage. Developing a micro / nano Newton force detection system that is easy to use, low in manufacturing cost, and simple in process is of great research significance. The most common MEMS micro-force sensors have the advantages of being label-free, real-time, localized, and specific in detection, and have been widely used as probes for atomic force microscopy (AFM) and other detection elements. However, their practical application is mainly limited by the large demodulation system, low detection sensitivity, and poor electromagnetic compatibility.

[0004] Fiber optic sensors offer advantages such as stable performance, small size, high sensitivity, and resistance to electromagnetic interference. Most importantly, fiber optics can replace complex and bulky spatial optical paths, significantly reducing system size. In recent years, fiber optic microforce sensors based on different fiber structures have been developed, such as fiber Bragg gratings, long-period fiber gratings, Fabry-Perot interferometers (FPIs), and Mach-Zehnder interferometers. Among these, the length of fiber Bragg gratings exceeds several millimeters, which greatly limits the sensor's compactness. In these microforce sensors, the FP interferometer formed between the microcantilever beam and the fiber end face can detect the weak vertical deformation of the cantilever, thus fiber optic FPI sensors based on microcantilever beams have gradually attracted the attention of scientists. The most direct method for integrating microcantilever beams with optical fibers is to connect a commercial microcantilever beam probe to the fiber end face. Microcantilever beams of different shapes and materials can be integrated and fabricated with the fiber end face. However, each cantilever beam must be aligned with the fiber end face using precision instruments and fixed with adhesive, which limits the repeatability and stability of the sensor.

[0005] Existing fiber-optic integrated microcantilever beam systems have been fabricated using subtractive methods such as picosecond and femtosecond laser ablation and focused ion beam processing. Picosecond laser ablation produces cantilever beams with limited processing precision, resulting in rough and thick surfaces, which severely impacts stress sensing performance based on cantilever beam deformation. Femtosecond laser ablation reduces roughness but increases manufacturing time. Microcantilever beams processed with focused ion beams are smooth and thin, but require expensive equipment and have long manufacturing times.

[0006] Therefore, existing technologies still need improvement. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a controllable microstructure cantilever beam fiber optic microforce sensor, its preparation and detection method, in order to solve the technical problems of complexity and low detection sensitivity of existing microforce sensor systems.

[0008] The technical solution adopted by this invention to solve the technical problem is as follows:

[0009] In a first aspect, the present invention provides a controllable microstructure cantilever beam fiber optic microforce sensor, the fiber optic microforce sensor comprising:

[0010] Silicon glass inserts;

[0011] A single-mode optical fiber, wherein the single-mode optical fiber is embedded in the silicon glass insert;

[0012] A controllable microstructure cantilever beam is disposed on one side of the single-mode optical fiber and on the surface of the silicon glass insert.

[0013] The end face of the single-mode optical fiber, the lower surface of the controllable microstructure cantilever beam, and the upper surface of the controllable microstructure cantilever beam resonate to form the reflection spectrum of the optical fiber microforce sensor.

[0014] The end face of the single-mode optical fiber forms an air microcavity with the lower surface of the controllable microstructure cantilever beam; the lower surface of the controllable microstructure cantilever beam forms a polymer microcavity with the upper surface of the controllable microstructure cantilever beam; and the end face of the single-mode optical fiber forms a hybrid microcavity with the upper surface of the controllable microstructure cantilever beam.

[0015] In one implementation, the relationship between the free spectral range of the air microcavity and the cavity length is as follows:

[0016]

[0017] Where λ is the resonant wavelength, L is the cavity length of the fiber optic microforce sensor, and n is the refractive index of the cavity medium of the fiber optic microforce sensor.

[0018] In one implementation, the relationship between the wavelength change and the cavity length in the air microcavity, the polymer microcavity, and the hybrid microcavity is as follows:

[0019]

[0020] Where ΔL is the change in cavity size;

[0021] Δλ is the change in wavelength;

[0022] λ is the resonant wavelength;

[0023] L represents the cavity length of the fiber optic microforce sensor.

[0024] In one implementation, the controllable microstructure cantilever beam includes: a base, a honeycomb structure cantilever beam, and a probe. The honeycomb structure cantilever beam is located at the upper end of the base, and the probe is located at the end of the honeycomb structure cantilever beam opposite to the base.

[0025] In one implementation, the base has a cross-sectional area of ​​60μm*60μm, the honeycomb cantilever beam has a thickness of 5μm, the side length of the honeycomb cells of the honeycomb cantilever beam is 0.5μm to 15μm, and the beam length of the honeycomb cantilever beam is 60μm to 200μm.

[0026] Secondly, the present invention provides a method for fabricating a controllable microstructure cantilever beam fiber optic microforce sensor, comprising:

[0027] Adjust the printing speed and laser energy, and import the pre-generated job file into the printing software. Use the printing software to control the switching of the three-dimensional displacement platform and the laser.

[0028] Insert the optical fiber into the silicon glass insert and fix it to the optical fiber with UV-curable adhesive;

[0029] The silicon glass insert is attached to the optical fiber insertion clamp, and photoresist is dropped onto the tip of the optical fiber and immersed into the end face.

[0030] The controllable microstructure cantilever beam fiber optic microforce sensor sample was obtained by focusing the laser energy, scanning speed, line spacing and layer spacing using an objective lens according to the preset laser energy, scanning speed, line spacing and layer spacing.

[0031] The obtained sample was immersed in propylene glycol methyl ether acetate and isopropanol successively to rinse off the residual photoresist and then subjected to UV irradiation to obtain the controllable microstructure cantilever beam fiber optic microforce sensor.

[0032] In one implementation, the adjustment of printing speed and laser energy includes, prior to:

[0033] A series of controllable microcantilever beams with honeycomb structures were generated using 3D software.

[0034] The controllable micro cantilever beam generated from the CAD model is exported as an STL file, and then sliced ​​and filled using filling software to obtain the pre-generated job file.

[0035] In one implementation, an FS laser with a pulse width of 250 fs, a wavelength of 1026 nm, a scan speed of 200 m / s, and a laser power of 30 mW is used in the polymerization.

[0036] Thirdly, the present invention provides a method for detecting controllable microstructure cantilever beams using fiber optic microforce sensors, comprising:

[0037] The spectral information is obtained by using the three interferometric beams formed by the resonance of three mirrors on the fiber end face, the upper surface of the controllable microstructure cantilever, and the lower surface of the controllable microstructure cantilever in the fiber optic microforce sensor.

[0038] The spectral information is analyzed to detect the resonant wavelengths of peaks or valleys in the spectral information, and the deflection information of the controllable microstructure cantilever beam is calculated based on the resonant wavelengths.

[0039] Based on the deflection information and the elastic coefficient of the controllable microstructure cantilever, the force exerted by the biological sample on the controllable microstructure cantilever is calculated.

[0040] In one implementation, the elastic coefficient of the controllable microstructure cantilever is a coefficient obtained by in-situ quantitative nanoindentation measurement.

[0041] The present invention, by employing the above technical solution, has the following effects:

[0042] This invention proposes a novel controllable microstructure cantilever beam probe fiber optic microforce sensor. By incorporating a controllable microstructure cantilever beam within a silicon glass insert into which a single-mode fiber is inserted, the end face of the single-mode fiber, the lower surface of the controllable microstructure cantilever beam, and the upper surface of the controllable microstructure cantilever beam can resonate to form the reflection spectrum of the fiber optic microforce sensor. Furthermore, by setting an air microcavity formed by the end face of the single-mode fiber and the lower surface of the controllable microstructure cantilever beam, a polymer microcavity formed by the lower surface of the controllable microstructure cantilever beam and the upper surface of the controllable microstructure cantilever beam, and a hybrid microcavity formed by the end face of the single-mode fiber and the upper surface of the controllable microstructure cantilever beam, the fiber optic microforce sensor possesses advantages such as high sensitivity, high mechanical strength, and an ultra-low detection limit, thereby enabling high-precision detection of weak forces on the order of picoNewtons in biological samples. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the overall structure of the controllable microstructure cantilever beam fiber optic microforce sensor in one implementation of the present invention.

[0045] Figure 2This is a schematic diagram of the controllable microstructure cantilever beam in one implementation of the present invention.

[0046] Figure 3 This is a structural design and simulation analysis diagram in one implementation of the present invention.

[0047] Figure 4 This is a flowchart illustrating the fabrication process of a controllable microstructure cantilever beam fiber optic microforce sensor in one implementation of the present invention.

[0048] Figure 5 This is a schematic diagram illustrating the fabrication of a controllable microstructure cantilever beam fiber optic microforce sensor in one implementation of the present invention.

[0049] Figure 6 This is a flowchart of the detection process of the fiber optic microforce sensor for a controllable microstructure cantilever beam in one implementation of the present invention.

[0050] Figure 7 This is a test and analysis diagram of the sensor elastic coefficient in one implementation of the present invention.

[0051] Figure 8 This is a schematic diagram of the experimental apparatus in one implementation of the present invention.

[0052] Figure 9 This is a schematic diagram of the linear fitting between the sensor's reflection spectrum, spectral variables, and force in one implementation of the present invention.

[0053] In the figure: 100, silicon glass insert; 200, single-mode optical fiber; 300, controllable microstructure cantilever beam; 301, base; 302, cellular structure cantilever beam; 303, probe.

[0054] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0056] Exemplary device

[0057] Existing fiber-optic integrated microcantilever beam systems have been fabricated using subtractive methods such as picosecond and femtosecond laser ablation and focused ion beam processing. Picosecond laser ablation produces cantilever beams with limited processing precision, resulting in rough and thick surfaces, which severely impacts stress sensing performance based on cantilever beam deformation. Femtosecond laser ablation reduces roughness but increases manufacturing time. Microcantilever beams processed with focused ion beams are smooth and thin, but require expensive equipment and have long manufacturing times.

[0058] To address the aforementioned technical issues, this embodiment proposes a novel controllable microstructure cantilever beam probe fiber optic microforce sensor. Compared to traditional force sensors, the proposed microforce sensor exhibits significantly higher force sensitivity than other types of fiber optic force sensors. Furthermore, this device also boasts advantages such as small size, resistance to electromagnetic interference, good biocompatibility, flexible manufacturing, high mechanical strength, small detection limit, and fast detection speed.

[0059] like Figure 1 As shown, this embodiment provides a controllable microstructure cantilever beam fiber optic microforce sensor, comprising:

[0060] The device comprises a silicon glass insert 100, a single-mode optical fiber 200, and a controllable microstructure cantilever beam 300; wherein the single-mode optical fiber 200 is embedded in the silicon glass insert 100; the controllable microstructure cantilever beam 300 is disposed on one side of the single-mode optical fiber 200 and on the surface of the silicon glass insert 100.

[0061] like Figure 2 As shown, in this embodiment, the controllable microstructure cantilever beam 300 includes: a base 301, a honeycomb structure cantilever beam 302, and a probe 303. The honeycomb structure cantilever beam 302 is located at the upper end of the base 301, and the probe 303 is located at the end of the honeycomb structure cantilever beam 302 opposite to the base 301.

[0062] The following specific examples illustrate the structural design and principle of the controllable microstructure cantilever beam fiber optic microforce sensor in this embodiment:

[0063] In this embodiment, the controllable microstructure cantilever beam fiber optic microforce sensor utilizes fiber optic transmission to replace the complex optical rod path of an atomic force microscope system, acquiring signals through optical interference. For example... Figure 1 As shown, the controllable microstructure cantilever beam fiber optic microforce sensor consists of a silicon glass insert 100, a single-mode fiber 200 (SMF), and a controllable microstructure cantilever beam 300.

[0064] The reflection spectrum of this controllable microstructure cantilever beam fiber optic microforce sensor is formed by the three-beam interference resulting from the resonance of the end face of the single-mode fiber 200, the lower surface of the controllable microstructure cantilever beam 300, and the upper surface of the controllable microstructure cantilever beam 300. Specifically, the end face of the single-mode fiber 200 and the lower surface of the controllable microstructure cantilever beam 300 form a beam of length L. Air An air microcavity (FPI1) ​​is formed on the upper and lower surfaces of the controllable microstructure cantilever beam 300. A length L is formed on the upper and lower surfaces of the controllable microstructure cantilever beam 300. Poly The polymer microcavity (FPI2) is then constructed. Finally, the end face of the single-mode fiber 200 forms a length L with the upper surface of the controllable microstructure cantilever beam 300. Air +L PolyHybrid microcavities (FPI3).

[0065] In this embodiment, the light intensity of the hybrid microcavity (FPI3) is relatively weaker than that of the air microcavity (FPI1) ​​and the polymer microcavity (FPI2). Furthermore, once the controllable microstructure cantilever beam fiber optic microforce sensor is fabricated, the lengths formed by the upper and lower surfaces of the controllable microstructure cantilever beam 300 do not change with the external environment, and the light intensity of the polymer microcavity (FPI2) remains constant. Therefore, the change in the reflection spectrum is due to the change in the air microcavity (FPI1) ​​caused by the application of force to the probe 303 of the controllable microstructure cantilever beam 300. The free spectral range of the air microcavity (FPI1) ​​can be calculated using the following formula:

[0066]

[0067] Where λ is the resonant wavelength, L is the length of the entire sensor cavity, and n is the refractive index of the entire sensor cavity medium.

[0068] When the probe 303 of the controllable microstructure cantilever beam 300 is subjected to a certain force, the honeycomb structure cantilever beam 302 in the controllable microstructure cantilever beam 300 deforms, and the optical path difference of the entire sensor cavity changes along with the interference fringes. By detecting the resonant wavelength of the peaks or valleys in the interference spectrum, the degree of bending of the honeycomb structure cantilever beam 302 can be determined. The correspondence between the wavelength change (Δλ) of the entire sensor cavity change (ΔL) and the cavity length can be simplified as follows:

[0069]

[0070] By monitoring the drift of the interference spectrum, the change in cavity length can be inferred, and then the external force applied to probe 303 can be measured.

[0071] In this embodiment, the controllable microstructure cantilever beam 300 is a polymer microcantilever beam. To optimize the overall sensing characteristics of the sensor, controllable microstructure cantilever beams 300 of different shapes are designed in this embodiment. This embodiment uses a honeycomb structure cantilever beam.

[0072] Honeycomb metamaterials are a novel type of porous topological material with advantages such as variable topology, light weight, and high specific stiffness. Compared with ordinary porous topological materials, these materials exhibit better notch resistance, fracture resistance, and high resilience. Due to their unique mechanical and physical properties, these materials have been introduced into cantilever structures for topology optimization of the internal microstructure. Exploring the mechanical theory of microfabrication of such metamaterials from the perspectives of 3D design, manufacturing, and application is of great significance. By employing the controlled variable method, the details of the honeycomb microcantilever beams are completely consistent, except for the differences in the side length of the cells and the length of the cantilever beam. The cross-sectional area of ​​the base 301 of the controllable microstructure cantilever beam 300 is 60μm*60μm, which improves the adhesion to the end face of the silicon glass insert 100. By maintaining the thickness of the base 301 at 5μm, the side length of the honeycomb cells in the honeycomb cantilever beam 302 is increased from 0.5μm to 15μm, and the beam length of the honeycomb cantilever beam 302 is increased from 60μm to 200μm. The front end of the honeycomb structure cantilever beam 302 is designed as a cuboid block to improve deflection sensitivity.

[0073] To investigate the static mechanical properties of the controllable microstructure cantilever beam 300, in this embodiment, force sensor models with different structural parameters and the same stress were established using COMSOL Multiphysics software. The simulation results are as follows: Figure 3 As shown.

[0074] like Figure 3 As shown in (a) to (d), this embodiment establishes a quantitative relationship between microstructure size and controllable hardness to predict size and guide the fabrication of controllable microstructure cantilever beams. The material parameters of the honeycomb structure cantilever beam 302, including Young's modulus, Poisson's ratio, and density, are 2.34 GPa, 0.33, and 1499 kg / m³, respectively. 3 ) -1 A physical field from solid mechanics is selected, and the same 1μN microforce is applied to probe 303. A steady-state solver is used to calculate the deformation of the cantilever beam 302 of the honeycomb structure under a finely meshed finite-domain decomposition, with the deformation of each stressed region as follows: Figure 3 As shown in (a) and (b). One variation is that the deflection of the cantilever beam 302 in the honeycomb structure increases with the side length of the honeycomb cells, as... Figure 3 As shown in (a), the bending deformation of the cantilever beam 302 in this deformable honeycomb structure exhibits a good linear relationship of 0.99984 with the side length of the honeycomb unit, as shown in Figure (a). Figure 3 As shown in (c).

[0075] Another variation scheme Figure 3As shown in (b), the deflection of the honeycomb structure cantilever beam 302 increases with the length (L) of the cantilever beam, and the deflection of the honeycomb structure cantilever beam 302 is linearly related to the cube of the cantilever beam length (L3), such as... Figure 3 As shown in (d), the smaller side length (a) and beam length (L) reduce the effective area of ​​the honeycomb cantilever beam 302. The smaller the effective surface area of ​​the honeycomb cantilever beam 302, the greater the bending deformation and the higher the sensitivity of the sensor. This result is consistent with the theoretical formula for rectangular cantilever beams and can provide theoretical guidance for the adjustment and control design of the elastic coefficient k of the honeycomb cantilever beam.

[0076] It is worth mentioning that the silicon glass insert 100 of the controllable microstructure cantilever beam probe fiber microforce sensor in this embodiment can be changed to other ferrule materials that can insert optical fibers; the honeycomb cell structure of the honeycomb structure cantilever beam 302 can be changed, such as cuboid, cylinder, truss structure, etc.; the size of the base 301 of the controllable microstructure cantilever beam 300, the honeycomb structure cantilever beam 302 and the probe 303 can all be adaptively changed.

[0077] This embodiment achieves the following technical effects through the above technical solution:

[0078] This embodiment proposes a novel controllable microstructure cantilever beam probe fiber optic microforce sensor. By setting a controllable microstructure cantilever beam in a silicon glass insert into which a single-mode fiber is inserted, the end face of the single-mode fiber, the lower surface of the controllable microstructure cantilever beam, and the upper surface of the controllable microstructure cantilever beam can resonate to form the reflection spectrum of the fiber optic microforce sensor. Furthermore, by setting an air microcavity between the end face of the single-mode fiber and the lower surface of the controllable microstructure cantilever beam, a polymer microcavity between the lower surface and the upper surface of the controllable microstructure cantilever beam, and a hybrid microcavity between the end face of the single-mode fiber and the upper surface of the controllable microstructure cantilever beam, the fiber optic microforce sensor has the advantages of high sensitivity, high mechanical strength, and ultra-low detection limit, thus enabling high-precision detection of weak forces on the order of picoNewtons in biological samples.

[0079] Exemplary Method 1

[0080] like Figure 4 As shown, this embodiment of the invention provides a method for fabricating a controllable microstructure cantilever beam fiber optic microforce sensor, used to fabricate the controllable microstructure cantilever beam fiber optic microforce sensor as described above, including the following steps:

[0081] Step S101: Adjust the printing speed and laser energy, and import the pre-generated job file into the printing software. Use the printing software to control the switching of the three-dimensional displacement platform and the laser.

[0082] Step S102: Insert the optical fiber into the silicon glass insert and fix the UV-cured adhesive onto the optical fiber;

[0083] Step S103: Place the silicon glass inserter with the optical fiber insertion clamp, and drop photoresist onto the tip of the optical fiber and immerse it in the end face;

[0084] Step S104: According to the preset laser energy, scanning speed, line spacing and layer spacing, the laser is focused using an objective lens to obtain a sample of the controllable microstructure cantilever beam fiber optic microforce sensor.

[0085] In step S105, the obtained sample is immersed in propylene glycol methyl ether acetate and isopropanol in turn to rinse off the residual photoresist and then subjected to UV irradiation to obtain the controllable microstructure cantilever beam fiber optic microforce sensor.

[0086] In this embodiment, before step S101, the following steps are also included:

[0087] Step S101a: A series of controllable microcantilever beams with honeycomb structures are generated using 3D software;

[0088] Step S101b: Export the generated controllable micro cantilever beam as an STL file using the CAD model, and use filling software to slice and fill it to obtain the pre-generated job file.

[0089] In step S104, an FS laser with a pulse width of 250 fs, a wavelength of 1026 nm, a scanning speed of 200 m / s, and a laser power of 30 mW is used in laser polymerization. By polymerization using the FS laser, a sample of a controllable microstructure cantilever beam fiber optic microforce sensor can be obtained.

[0090] The following specific examples illustrate the fabrication method of the controllable microstructure cantilever beam fiber optic microforce sensor in this embodiment:

[0091] In this embodiment, a controllable microstructure cantilever beam at the end of an optical fiber is prepared by femtosecond laser using two-photon polymerization (TPP).

[0092] like Figure 5 As shown, a series of probes for controllable microstructure cantilever beams are first produced using SOLIDWORKS software. Then, the CAD model is exported as an STL file, and DeScribe software is used for slicing and filling.

[0093] When creating line groups, a serpentine scanning mode is used to improve efficiency and accuracy. By adjusting the printing speed and laser energy, complex geometric shapes can be printed, and the job file can be imported into NanoWrite software, which controls the 3D displacement platform and laser switching.

[0094] After modulating the three-dimensional displacement platform and laser type, the single-mode fiber is inserted into the center of the silicon glass insert, aligning their end faces. It is then fixed to the single-mode fiber with UV-cured adhesive to prevent movement during printing. Next, the silicon glass insert and single-mode fiber are inserted into a fixture, and photoresist is dropped onto the tip of the single-mode fiber and immersed into its end face.

[0095] To ensure a good morphology for the controllable microstructure cantilever beam, a 63× (NA = 1.4) oil immersion objective was used for focusing. Polymerization was performed using an objective with appropriate laser energy, scanning speed, line spacing, and layer spacing. Overexposure caused by excessively high laser energy, slow scanning speed, or narrow line spacing or layer spacing can lead to photoresist ablation, bubble formation, and damage or loss of the polymer structure. Here, an FS laser with a pulse width of 250 fs, a wavelength of 1026 nm, a scanning speed of 200 m / s, and a laser power of 30 mW was used for polymerization. The laser beam was focused onto the sample, and the liquid was converted into a solid by polymerizing along the path of the focused laser beam in the photoresist.

[0096] After polymerization, the sample was immersed in propylene glycol methyl ether acetate (PGMEA) for at least 20 minutes and in isopropanol for about 5 minutes to rinse away residual photoresist. Simultaneously, UV irradiation was applied to provide uniform crosslinking of the printed structure, ensuring mechanical stability. After cleaning, the controllable microstructure cantilever beam was successfully printed on the surface of a silicon glass insert containing a single-mode optical fiber.

[0097] This embodiment achieves the following technical effects through the above technical solution:

[0098] Compared to these subtractive manufacturing techniques, this embodiment utilizes additive manufacturing to selectively add materials to three-dimensional structures. Micro / nano-scale additive manufacturing technology is primarily based on the chemical process of photoresist polymerization and curing. This process utilizes the material under laser exposure conditions to generate and distinguish soluble or insoluble blocks, constructing a pre-defined pattern on a two-dimensional level. Finally, through spatial stacking of materials, micro / nano structures are formed. Two-photon polymerization can directly additively print various complex micro / nano structures on fiber optic substrates, effectively achieving precise integration of micro-cantilever beams and optical fibers, making it possible to combine MEMS micro-force sensing technology with fiber optic sensing technology. This embodiment employs a femtosecond laser two-photon polymerization technology for a microstructure-controllable cantilever beam fiber optic micro-force sensor, combined with a chitosan / polyacrylic acid bilayer molecular film, effectively improving the detection accuracy of micro-forces.

[0099] Exemplary Method 2

[0100] like Figure 6 As shown, this embodiment of the invention provides a method for detecting controllable microstructure cantilever beams using fiber optic microforce sensors, comprising the following steps:

[0101] Step S201: Obtain the spectrum information based on the three beams of interference light formed by the resonance of the three mirrors on the fiber end face, the upper surface of the controllable microstructure cantilever, and the lower surface of the controllable microstructure cantilever in the controllable microstructure cantilever fiber microforce sensor.

[0102] Step S202: Analyze the spectrum information, detect the resonant wavelength of the peaks or valleys in the spectrum information, and calculate the deflection information of the controllable microstructure cantilever beam based on the resonant wavelength;

[0103] Step S203: Based on the deflection information and the elastic coefficient of the controllable microstructure cantilever, calculate the force exerted by the biological sample on the controllable microstructure cantilever.

[0104] In step S203, the elastic coefficient of the controllable microstructure cantilever is the coefficient obtained by in-situ quantitative nanoindentation measurement.

[0105] The following specific examples illustrate the detection method of the fiber optic microforce sensor for the controllable microstructure cantilever beam in this embodiment:

[0106] In this embodiment, the sensing and detection device includes: a broadband light source, a spectrometer, a 3dB fiber optic coupler, a 3D micro-controlled displacement platform, a CCD real-time image acquisition system, a controllable microstructure cantilever beam fiber optic micro-force sensor as described in the above embodiment, a biological sample holder, and a stage. This sensing and detection device has advantages such as small size, resistance to electromagnetic interference, good biocompatibility, flexible manufacturing, high mechanical strength, small detection limit, and fast detection speed.

[0107] like Figures 1-2 As shown, Figures 1-2 Scanning electron microscopy (SEM) images of the controllable microstructure cantilever beam are shown. The SEM images indicate that the actual dimensions of the controllable microstructure cantilever beam are consistent with the design. It essentially consists of three parts. At the bottom, the base has a cross-sectional area of ​​60 μm x 60 μm. At the top of the base, a honeycomb structure cantilever beam is connected to the base; the honeycomb structure cantilever beam is 30 μm wide, 5 μm thick, and 200 μm long. Above the cuboid block at the end of the honeycomb structure cantilever beam, there is a probe with a height of 15 μm and a diameter of 4 μm, used for mechanical testing. The top view shows that the surface is smooth and the shape is intact. The rectangular block at the end of the honeycomb structure cantilever beam blocks the fiber core to excite interference.

[0108] To determine the mechanical properties of the honeycomb cantilever beam, a nanoindenter (Hysitron TI980) was used. The structure of the honeycomb cantilever beam is a crucial factor affecting the characteristics of the microforce sensor, and the dimensions of the periodic porous structure also play a significant role in mechanical properties. The effects of the side length of the honeycomb cells and the beam length on the mechanical properties of the microcantilever structure were investigated. The side length of the honeycomb cells was initially increased from 0.5 μm to 15 μm, such as... Figure 7 As shown in (a), the force curves of the six groups of micro-cantilever beams exhibit a well-defined separation line shape. Figure 7 As shown in (b), the first-order elastic constant k ranges from 0.980 to 46.092 N / m. The value of k for the cantilever beam of the cellular structure is related to the sensitivity; the smaller the value of k, the higher the sensitivity. Good linearity (R² 99.985%) was observed, indicating that the equation can be used to adjust the cellular geometry with a target k, which can be adjusted by two orders of magnitude by changing the length, and the mechanical properties of the microforce sensor can be optimized by adjusting the side length of the cellular cells.

[0109] In the next step, L was increased from 60 μm to 200 μm, such as... Figure 7 As shown in (c), the longer microcantilever beam incorporates hexagonal honeycomb elements, and the elastic constant k gradually decreases. Figure 7 As shown in (d), the first-order elastic constant k ranges from 0.165 to 0.980 N / m, with good linearity observed (R² 99.734%). Furthermore, the elastic constant k (0.165 N / m) is close to the minimum value at the tip of the atomic force microscope, and the range of the total elastic constant k essentially covers the range of commercial atomic force microscope probes.

[0110] Finally, the stability of the cantilever beam of the honeycomb structure was evaluated by repeating the experiment five times. Figure 7 Figures (e) to (f) show that the force curves for the five cycles overlap, with k being a constant (6.92 ± 0.23 N / m). The small fluctuations in sensitivity confirm that the structure possesses excellent mechanical stability and elasticity under compression conditions.

[0111] The sensing principle of the controllable microstructure cantilever beam fiber optic microforce sensor proposed in this invention is based on the change in the bending deflection of a honeycomb structure cantilever beam above the end face of a single-mode fiber. For example... Figure 8 As shown, Figure 8 (a) shows the reflection spectrum of a cellular cantilever beam connected to a broadband light source (BBS), an OSA spectrometer, and an optical fiber circulator. Figure 8The interference spectrum in (b) shows three-beam interference formed by the resonance of three mirrors on the end face of the single-mode fiber and the upper and lower surfaces of the cellular cantilever beam. The small envelope in the spectrum is formed by the FP cavity of the air medium, which contains the deflection information of the cellular cantilever beam to be monitored. The free spectral range of the cellular cantilever beam near the wavelength of 1451.22 nm is 24.5 nm, with an extinction ratio of 9.6 dB. According to equation (1) in the above embodiment, the cavity length of the fabricated cellular cantilever beam is approximately 43 m. The slight difference in cavity length can be attributed to the adjustment of the first layer of the polymer plane below the fiber end face by more than 10 micrometers during vertical fabrication to ensure that there is no gap between the support post and the end face of the single-mode fiber.

[0112] According to equation (2) in the example above, micro-force sensitivity can be obtained by the tilt wavelength shift caused by a unit force on the probe of the honeycomb cantilever beam. The device consists of a BBS, OSA, 3dB coupler, and a 3D electrical displacement platform for micromanipulation. A coverslip is placed on the sample holder, and the sensor probe is placed on the surface of the coverslip to deflect the honeycomb cantilever beam. The elastic coefficient k of the sensor probe is 0.165 by in-situ quantitative nanoindentation measurement. The reaction force on the sensor probe is based on Hooke's Law, expressed as follows:

[0113] F=k×d (3)

[0114] The elastic modulus (k) of the honeycomb cantilever beam is 0.165, and the probe of the honeycomb cantilever beam is subjected to phase synchronous load displacement compression each time, that is, the bending deformation (d) of the honeycomb cantilever beam is 50nm.

[0115] According to formula (3), the microforce on the cantilever beam of the honeycomb structure is 8.25 N at each step of 50 nm. The reflectance spectrum is acquired in real time during the application of the progressive force.

[0116] like Figure 9 As shown, Figure 9 Figure (a) shows the change in the reflectance spectrum as the force gradually increases from 0 to 66 nN. As indicated by the arrows, a blue shift is clearly observed at the tilted wavelength. Due to the bending of the cantilever beam in the honeycomb structure, the extinction ratio of the reflectance spectrum decreases with increasing force. The relationship between the tilted wavelength and the force is shown in Figure (a). Figure 9 As shown in (b), the falling wavelength linearly shifts to a shorter wavelength as the applied force increases. Based on the linear fit of the falling wavelength change, the force sensitivity is calculated to be 154.04 nm / N, which is two orders of magnitude higher than previously reported fiber optic force sensors. The R² describing the matching degree is 0.99412. In microforce sensing measurements, the sensor probe operates within the framework of linear elasticity and there is no hysteresis between changes in force and cavity length.

[0117] In ideal sensor devices, the Q-factor and detection limit (DL) are crucial because they represent overall performance. For fiber optic sensors, Q is defined as follows:

[0118]

[0119] Wherein, λQ is the center wavelength of the resonance peak, and ΔλQ is the half-peak width of the resonance peak.

[0120] according to Figure 9 In the spectrum of (a), λQ and ΔλQ are 1451.22 nm and 4.03 nm, respectively, therefore, Q is 360.104.

[0121] DL is typically determined by sensor resolution (R) and sensor sensitivity (S). S can be calculated. R can be approximated by a single noise variance (i.e., R = 3σ):

[0122]

[0123] Standard deviation (σ) describes the amplitude variation caused by noise, and SNR represents the signal-to-noise ratio. At the spectral resolution of the demodulator instrument, σ also exists in the spectral variation:

[0124]

[0125] In the micro-force sensing experiments, the main limitations of the detection limit were: a measured value of 4.03 nm and a SNR expressed in linear units (50 dB). The calculated DL of the device was 980.8 pN, and the small DL facilitated the detection of minute force changes. By testing the micro-force sensor's response to other loads, the maximum applied force was 4.62 μN.

[0126] This embodiment achieves the following technical effects through the above technical solution:

[0127] The controllable microstructure cantilever beam fiber optic microforce sensor detection method provided in this embodiment is based on a sensor with high sensitivity, high mechanical strength and ultra-low detection limit. It can perform detection of weak forces on the order of pionewtons (pN) in biological samples. Furthermore, the elastic constant k of the fiber optic microforce sensor can be adjusted by two orders of magnitude by changing the structural size, which can match the mechanical properties of various biological samples.

[0128] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided by this invention can include non-volatile and / or volatile memory.

[0129] In summary, this invention provides a controllable microstructure cantilever beam fiber optic microforce sensor, its fabrication, and a detection method, comprising: a silicon glass insert; a single-mode fiber embedded in the silicon glass insert; a controllable microstructure cantilever beam disposed on one side of the single-mode fiber and embedded in the silicon glass insert; the end face of the single-mode fiber, the lower surface of the controllable microstructure cantilever beam, and the upper surface of the controllable microstructure cantilever beam resonate to form the reflection spectrum of the fiber optic microforce sensor; the end face of the single-mode fiber and the lower surface of the controllable microstructure cantilever beam form an air microcavity; the lower surface of the controllable microstructure cantilever beam and the upper surface of the controllable microstructure cantilever beam form a polymer microcavity; and the end face of the single-mode fiber and the upper surface of the controllable microstructure cantilever beam form a hybrid microcavity. The novel controllable microstructure cantilever beam probe fiber optic microforce sensor of this invention has a simple structure and advantages such as high sensitivity, high mechanical strength, and ultra-low detection limit.

[0130] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A controllable microstructured cantilevered beam fiber micro-force sensor, characterized in that, The fiber optic micro-force sensor includes: Silicon glass inserts; A single-mode optical fiber, wherein the single-mode optical fiber is embedded in the silicon glass insert; A controllable microstructure cantilever beam is disposed on one side of the single-mode optical fiber and on the surface of the silicon glass insert. The controllable microstructure cantilever beam includes a base, a honeycomb structure cantilever beam, and a probe. The honeycomb structure cantilever beam is located at the upper end of the base, and the probe is located at the end of the honeycomb structure cantilever beam opposite to the base. The cross-sectional area of ​​the base is... The thickness of the honeycomb structure cantilever beam is The side length of the honeycomb unit in the honeycomb structure cantilever beam is The length of the honeycomb structure cantilever beam is ; The end face of the single-mode optical fiber, the lower surface of the controllable microstructure cantilever beam, and the upper surface of the controllable microstructure cantilever beam resonate to form the reflection spectrum of the optical fiber microforce sensor. The end face of the single-mode optical fiber and the lower surface of the controllable microstructure cantilever beam form an air microcavity; the lower surface of the controllable microstructure cantilever beam and the upper surface of the controllable microstructure cantilever beam form a polymer microcavity; the end face of the single-mode optical fiber and the upper surface of the controllable microstructure cantilever beam form a hybrid microcavity. The relationship between the free spectral range of the air microcavity and the cavity length is as follows: ； in, Where λ is the resonant wavelength, L is the cavity length of the fiber optic micro-force sensor, and n is the refractive index of the cavity medium of the fiber optic micro-force sensor. In the air microcavity, the polymer microcavity, and the hybrid microcavity, the relationship between the wavelength change and the cavity length is as follows: ； in, This represents the change in cavity size; This is the change in wavelength; The resonant wavelength; L is the cavity length of the fiber optic micro-force sensor; When the probe of the controllable microstructure cantilever beam is subjected to a certain force, the honeycomb structure cantilever beam in the controllable microstructure cantilever beam deforms, and the optical path difference of the entire sensor cavity changes along with the interference fringes; by detecting the resonant wavelength of the peaks or valleys in the interference spectrum, the degree of bending of the honeycomb structure cantilever beam can be determined.

2. A method for fabricating a controllable microstructure cantilever beam fiber optic microforce sensor, characterized in that, include: A series of controllable microcantilever beams with honeycomb structures were generated using 3D software. The controllable micro cantilever beam generated from the CAD model is exported as an STL file, and then sliced ​​and filled using filling software to obtain a pre-generated job file. Adjust the printing speed and laser energy, and import the pre-generated job file into the printing software. Use the printing software to control the switching of the three-dimensional displacement platform and the laser. Insert the optical fiber into the silicon glass insert and fix it to the optical fiber with UV-curable adhesive; The silicon glass insert is attached to the optical fiber insertion clamp, and photoresist is dropped onto the tip of the optical fiber and immersed into the end face. The controllable microstructure cantilever beam fiber optic microforce sensor sample was obtained by using an objective lens to aggregate the laser energy, scanning speed, line spacing, and layer spacing according to the preset laser energy, scanning speed, and layer spacing. An FS laser with a pulse width of 250 fs, a wavelength of 1026 nm, a scanning speed of 200 m / s, and a laser power of 30 mW was used in the aggregation process. The obtained sample was immersed in propylene glycol methyl ether acetate and isopropanol successively to rinse off the residual photoresist and then subjected to UV irradiation to obtain the controllable microstructure cantilever beam fiber optic microforce sensor.

3. A method for detecting controllable microstructure cantilever beams using fiber optic microforce sensors, characterized in that, include: The spectral information is obtained by using the three interferometric beams formed by the resonance of three mirrors on the fiber end face, the upper surface of the controllable microstructure cantilever, and the lower surface of the controllable microstructure cantilever in the fiber optic microforce sensor. The spectral information is analyzed to detect the resonant wavelengths of peaks or valleys in the spectral information, and the deflection information of the controllable microstructure cantilever beam is calculated based on the resonant wavelengths. Based on the deflection information and the elastic coefficient of the controllable microstructure cantilever, the force exerted by the biological sample on the controllable microstructure cantilever is calculated; wherein, the elastic coefficient of the controllable microstructure cantilever is a coefficient obtained by in-situ quantitative nanoindentation measurement.

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