Intelligent optical surface control method and device for magnetic driving wrinkle instability

Abstract

This invention discloses a method and apparatus for intelligent optical surface control of magnetically driven wrinkling instability. The method employs soft intelligent materials to construct a magnetoelastic thin film structure (thin film or thin film-substrate composite structure). Leveraging the unique properties of soft intelligent materials, the critical magnetic field parameters that induce wrinkling instability in the magnetoelastic thin film structure are determined through theoretical calculations. After applying mechanical pre-compression / stretching to the magnetoelastic thin film structure, the magnetic induction intensity of the applied magnetic field is adjusted to achieve intelligent optical control of the surface of the magnetoelastic thin film structure, precisely controlling the dynamic transformation of the surface's optical reflection state. This method enables non-contact, reversible, and programmable magnetic field control of the wrinkled morphology of optical surfaces, overcoming the inherent defects of contact-driven methods, and exhibiting excellent cycle stability. Simultaneously, it allows for customized design and precise control, with a simple overall fabrication process, possessing significant engineering application value.

Description

Technical Field

[0001] This invention belongs to the field of intelligent optical surface control technology, and relates to an intelligent optical surface control method and device for magnetically driven wrinkling instability. Background Technology

[0002] Adjustable optical surfaces are the core basic components for realizing active tuning of optical devices. When the optical surface changes from smooth and flat to wrinkled, the incident light changes from specular directional reflection to diffuse scattering, and the optical properties are fundamentally changed. Existing optical surface control technologies mainly include: (1) Mechanical drive: relying on mechanical contact, the drive structure is complex and it is difficult to achieve non-contact and remote control; (2) Thermal drive: slow response speed, low thermal field control accuracy, and high temperature can easily cause aging of elastomers; (3) Pneumatic drive: requires matching air circuit connection, high sealing requirements, which is not conducive to device miniaturization; (4) Electric field / swelling drive: electric field drive requires the application of thousands of volts of high voltage, which poses a safety hazard; swelling drive has a lag response and insufficient control accuracy. The above technologies generally have common defects: the control method relies on physical contact or complex connection, making it difficult to achieve non-contact operation; the reversibility and response performance are poor; the programmable control capability is insufficient, making it difficult to meet the needs of refined and intelligent applications.

[0003] To overcome the shortcomings of existing technologies and further expand the engineering application scenarios of active tuning of optical devices, this invention proposes an intelligent optical surface control method and device for driving wrinkle instability, which has important theoretical value and engineering application significance. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method and apparatus for controlling magnetically driven wrinkling instability in intelligent optical surfaces.

[0005] The technical solution adopted in this invention is as follows: A method for controlling magnetically driven wrinkling instability in intelligent optical surfaces includes the following steps: S11 Preparation of magnetoelastic thin film structures: The magnetoelastic thin film structure is a pure thin film structure, or a thin film-substrate composite structure formed by bonding a thin film to a substrate; wherein, the thin film is a magnetic powder modified thin film, and the substrate includes a hyperelastic substrate or a magnetic substrate; The S12 test determines the initial shear modulus of the film and substrate materials in the magnetoelastic thin film structure. The S13 test determines the magnetic susceptibility of the thin film. ; S14 applies uniaxial or biaxial pre-compression / tension mechanical constraints to the magnetoelastic thin film structure and maintains a stable compression / tension state through a mechanical locking mechanism; S15 determined, through theoretical calculations, the dimensionless critical magnetic field that can cause wrinkling instability in magnetoelastic thin film structures. ; S16 applies an external magnetic field to the magnetoelastic thin film structure to ensure that a uniform magnetic field region covers the entire film, and that the magnetic field generating device has no physical contact with the magnetoelastic thin film structure, thereby achieving non-contact driving. S17 achieves intelligent optical control of the surface of the magnetoelastic thin film structure by adjusting the magnetic induction intensity of the applied external magnetic field, thereby enabling controllable switching of its surface optical reflection state.

[0006] In the above technical solution, the film is further prepared by combining a superelastic material with magnetic iron powder particles, and the magnetic iron powder particles are uniformly dispersed in the superelastic matrix; the substrate is prepared by a superelastic material or by a superelastic material containing magnetic components.

[0007] Furthermore, in step S14, the magnetoelastic thin film structure is clamped in a mechanical loading device, with the center point of the thin film surface as the Cartesian coordinate system. The origin, pointing towards the base direction is X 2 directions, mechanical loading along X 3 directions, and along X Apply external force in direction 1.

[0008] Furthermore, in S15, the surface impedance method is used to solve for the dimensionless critical magnetic field that drives the magnetoelastic thin film structure to wrinkle and become unstable. Specifically: At the interface between the thin film and the substrate, the stress vector of the thin film minus the stress vector of the substrate equals the stress vector corresponding to the vacuum / air domain; at the interface between the thin film and the substrate, displacement and potential are continuous; at the interface between the thin film and the vacuum / air domain, the stress vector of the thin film equals the stress vector corresponding to the vacuum / air domain. Based on the above boundary conditions, two characteristic equations are obtained for the surface wrinkling instability of the thin film-substrate structure under force-magnetic coupling: or: in, These represent the surface impedance matrices at the thin film-substrate interface, and the corresponding regions in the thin film, substrate, and vacuum / air domains, respectively. The superscript T indicates matrix transpose. Indicates the ratio of shear moduli. and These are the initial shear moduli of the thin film and the substrate, respectively. , , Transmission matrix The submatrix, the transfer matrix, is a linear operator that describes the spatial transfer relationship of displacement, stress, and magnetic potential state vectors between different interfaces in thin films, substrates, and vacuum layered structures. It is used to satisfy the interface continuity condition and derive the characteristic equation of structural instability. When the above characteristic equation is satisfied, there exists a nontrivial incremental solution: corresponding to the magnetic induction intensity. and critical wavenumber , The minimum value corresponding to the curve is the critical magnetic flux density at which the thin film-substrate structure experiences surface wrinkling instability. ;when When the magnetoelastic thin film undergoes wrinkling and instability, the magnetic induction intensity is obtained. and critical magnetic induction intensity .

[0009] Furthermore, in S15, an approximate expression is used to describe the dimensionless critical magnetic field that causes wrinkling instability in the magnetically driven magnetoelastic thin film structure. To perform an approximate solution, specifically: m The approximate bifurcation equation is: in, n Indicates the number of terms in the asymptotic expansion. Representing the Stroh matrix n Power of; Represents the Stroh matrix. These represent the surface impedance matrices at the thin film-substrate interface, corresponding to the thin film, substrate, and vacuum region, respectively. The superscript T indicates matrix transpose. Indicates the ratio of shear moduli. and These are the initial shear moduli of the thin film and the substrate, respectively. Given the constitutive relations of the thin film and the substrate, the corresponding magnetic flux density can be calculated. and the corresponding critical wavenumber , The minimum value corresponding to the curve is the critical magnetic flux density at which the thin film-substrate structure experiences surface wrinkling instability. ;when When the magnetoelastic thin film undergoes wrinkling and instability, the magnetic induction intensity is obtained. and critical magnetic induction intensity .

[0010] Furthermore, in S15, an asymptotic expression is used to solve for the dimensionless critical magnetic field that causes wrinkling instability in the magnetoelastic thin film structure under magnetic drive. Specifically: The explicit asymptotic expression is: in,

[0011] In plane strain state X Deformation ratio in direction 1 Indicates the ratio of shear moduli. and These are the initial shear moduli of the thin film and the substrate, respectively. It is a high-order small quantity and can be ignored.

[0012] Furthermore, the optical surface manipulation specifically includes: 1) When an external magnetic field is applied When the thin film surface is smooth and flat, it undergoes specular reflection, resulting in a clear light spot on the imaging panel used to detect the optical reflection state of the laser source. 2) When At this time, micro-wrinkles will appear on the surface of the thin film, and the light spot on the imaging panel will widen and a scattering halo will appear; 3) When At that time, the thin film showed obvious wrinkles, the specular reflection disappeared and turned into complete diffuse scattering, and the light spot on the imaging panel disappeared.

[0013] Furthermore, by adjusting the initial shear modulus of the film and substrate materials, and / or adjusting the pre-compression / tension applied in S14, the dimensionless critical magnetic field at which the magnetoelastic film structure experiences wrinkling instability can be altered. .

[0014] The present invention also provides an intelligent optical surface control device for magnetically driven wrinkling instability, comprising a magnetoelastic thin film structure, a mechanical loading unit, and an external magnetic field loading unit; The magnetoelastic thin film structure is a pure thin film or a thin film-substrate structure consisting of a thin film and a substrate; the thin film is a magnetic powder modified thin film, and the substrate is a hyperelastic substrate or a magnetic substrate; The mechanical loading unit is used to apply pre-deformation to the magnetoelastic thin film structure, and the external magnetic field loading unit is used to apply a magnetic field to the magnetoelastic thin film structure. By controlling the magnetic induction intensity of the magnetic field, intelligent optical modulation of the surface of the magnetoelastic thin film structure is achieved, and the dynamic change of its optical reflection state is controlled.

[0015] Furthermore, the dimensionless critical magnetic field at which the magnetoelastic thin film structure experiences wrinkling instability is... When an external magnetic field is applied When the film surface is smooth and flat, specular reflection occurs on the film surface. At that time, micro-wrinkles and scattering halos appeared on the surface of the thin film. At that time, the film showed obvious wrinkles and completely diffuse scattering.

[0016] The beneficial effects of this invention are as follows: The method of this invention achieves: (1) Non-contact remote control: No physical connection is required, and remote control can be achieved by penetrating shielding objects, which fundamentally overcomes the inherent limitations of contact drive; (2) Fully reversible control: With the elastic recovery characteristics of the superelastic substrate, the cycle stability is excellent; (3) Multi-level programmable continuous control: By continuously adjusting the magnetic induction intensity of the driving magnetic field, precise and continuous optical state control can be achieved between specular reflection and complete diffuse scattering; (4) Customized design on demand: By adjusting the shear modulus ratio, pre-compression / stretching and other parameters of the thin film substrate system, the instability trigger threshold can be flexibly designed; (5) Simple preparation process: No complex micro-nano processing is required, the process is simple, and it is easy to promote and apply on a large scale. Attached Figure Description

[0017] Figure 1 Schematic diagram of the fabrication process of magnetoelastic thin film-substrate structure; Figure 2 Schematic diagram of the thin film-substrate structure: (a) Undeformed state; (b) Pre-compressed / stretched state; (c) Wrinkled state after applying a magnetic field; Figure 3 Critical magnetic induction intensity Elongation ratio and the initial shear modulus ratio of the film to the substrate Relationship curve (comparison of exact and approximate solutions); Figure 4 Critical magnetic induction intensity Elongation ratio and the initial shear modulus ratio of the thin film substrate Relationship curve diagram (comparison diagram of exact solution and asymptotic solution); Figure 5 Schematic diagram of the three stages of optical control. Detailed Implementation

[0018] To make the objectives and concepts of this invention clearer, the method provided by this invention will be further described and illustrated in conjunction with embodiments and accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and do not limit the scope of protection of this invention.

[0019] This invention provides an intelligent optical surface control method for magnetically driven wrinkle instability. By employing soft intelligent materials and utilizing their properties, it achieves non-contact, reversible, and programmable magnetic field control of the wrinkle morphology of the optical surface. The method includes the following steps: S11 Preparation of magnetoelastic thin film structures: The magnetoelastic thin film structure includes a pure thin film structure consisting only of a thin film, or a thin film-substrate structure consisting of a thin film and a substrate. The method of the present invention applies to both.

[0020] The thin film is typically prepared by combining a superelastic material with soft magnetic carbonyl iron powder particles uniformly dispersed in the superelastic material. The substrate is either a non-magnetic substrate made of the superelastic material or a magnetic substrate composed of a magnetic material and a superelastic material.

[0021] According to a specific embodiment of the present invention, the magnetoelastic thin film structure in this embodiment is composed of a thin film and a substrate, and its preparation process is shown in the schematic diagram below. Figure 1 As shown, the preparation steps are as follows: First, a mixture of superelastic matrix material and soft magnetic carbonyl iron powder particles is poured into a mold base of predetermined size (for forming the film). The mold is placed in the center of a homogenizer and rotated at 200 rpm to evenly spread the mixture within the mold and remove excess material. Then, the complete mold is assembled, and the other half of the mold (for forming the substrate) is installed on the base. The superelastic matrix material is then poured into the mold. Finally, the mold is vacuum-treated and placed in an oven at 70 ℃ for curing for 2 hours. After demolding, a magnetoelastic film-substrate composite structure with the film and substrate integrally formed is obtained.

[0022] S12 tests the initial shear modulus of the film and substrate in the magnetoelastic thin film structure, where the initial shear modulus of the film and substrate are denoted as [formulas to be inserted here]. and This can be achieved directly using existing testing methods: (1) Sample preparation: Samples were prepared according to ASTM D5279-2013 (dynamic shear), ISO 6721-10:2015 (shear vibration) or GB / T 16776-2025 (shear performance of silicone structural adhesives) standards; among them, dumbbell-shaped (gauge length 20mm×4mm×2mm) or parallel plate samples (diameter 25mm, thickness 2~4mm) were used for the substrate (also known as the hyperelastic substrate), and unnotched rectangular samples (50mm×12mm×12mm) were used for the magnetic powder modified film to ensure that the samples were free of bubbles and magnetic powder agglomeration defects; (2) Strain and loading settings: A rotational rheometer (cone / parallel plate fixture) or a dynamic mechanical analyzer (DMA) was used. The test temperature was controlled at 23±2℃ (standard environment), and the substrate loading rate was 50mm / min (corresponding to a tensile rate of 0.04s). -1 The loading rate of the magnetic powder modified film was 5.5±0.7 mm / min; the shear strain was measured by optical extensometer or DIC technology, and the oscillation frequency was set to 1 Hz and the strain amplitude was 0.1%~1% during dynamic testing (to ensure that it is in the linear viscoelastic region). (3) Data processing: Extract the linear segment of the shear stress-strain (τ-γ) curve. The strain range of 0~10% is taken for the hyperelastic substrate and the strain range of 0~5% is taken for the magnetic powder modified film. The slope G=Δτ / Δγ is calculated by least squares fitting. Repeat the test 3~5 times and take the average value. In the dynamic test, the energy storage modulus is directly read as the initial shear modulus.

[0023] S13 Test the magnetic susceptibility of the thin film This can be achieved directly using existing testing methods: (1) Prepare samples according to standards: Process the samples according to the requirements of the testing equipment to ensure that the magnetic powder in the magnetic powder modified film is uniformly dispersed and free from agglomeration; (2) Test equipment and calibration: According to GB / T 11209-1989, the low frequency band uses an LCR impedance analyzer (frequency 1kHz) or a vibrating sample magnetometer (VSM), and the microwave band uses a vector network analyzer (VNA). Open circuit / short circuit / load calibration is completed before testing to eliminate the influence of the fixture's accompanying inductance. (3) Data acquisition and inversion: Inductance in the low-frequency band is measured using an LCR impedance analyzer. From the formula (1) Inverse calculation of relative permeability , The number of coil turns. The cross-sectional area of ​​the sample is... The initial magnetic permeability can be obtained by taking the slope of the initial magnetization curve obtained by measuring the magnetic path length or by testing the initial magnetization curve using a VSM (vibrating sample magnetometer). Microwave band measurement S The parameters were used to inversely calculate the permeability using the Nicolson-Ross-Weir (NRW) algorithm. Then, through... Inverse calculation of magnetic susceptibility .

[0024] S14 applies a pre-compression / tension constraint: A uniaxial or biaxial pre-compression / tension mechanical constraint is applied to the magnetoelastic thin film structure, and a stable pre-deformation state is maintained by a mechanical locking mechanism. According to one embodiment of the invention, as shown in FIG2, the magnetoelastic thin film structure is sandwiched between two fixed and lubricated rigid plates (the normal direction of the rigid plates is along...). (direction), and along Apply mechanical loads in a specific direction to achieve pre-compression / tension.

[0025] S15 Determine the dimensionless critical magnetic field for wrinkle instability in a magnetoelastic thin film structure system. : The analysis is based on a film-substrate structure formed by bonding a magnetic powder modified film to a superelastic substrate in a half-space. This analysis method is also applicable to pure magnetoelastic films without a substrate, only requiring the thickness of the substrate to be set to 0.

[0026] like Figure 2 As shown, in the initial undeformed configuration, the Cartesian coordinate system is established with the center point of the thin film-substrate interface as the coordinate system. The origin, pointing towards the base direction is X In two directions, the thin film and the substrate occupy different positions. and area, This represents the initial thickness of the thin film. and They are respectively and The initial in-plane feature scale of the direction.

[0027] Under the current deformed configuration, the thin film-substrate system along the... Uniform deformation occurs along the parallel principal elongation directions, and the corresponding principal elongation ratio is: , i =1,2,3. Therefore, the current thickness of the thin film is 1,2,3. The in-plane scales are respectively and The film is completely bonded to the substrate, and both are considered incompressible materials, thus undergoing the same deformation and satisfying the volume conservation condition. The system deformation is driven by force-magnetic coupling: along and The applied mechanical preload, and along A uniform external magnetic field in a specific direction; the magnetic induction vector in Euler's description. The corresponding Lagrange description of the magnetic field is Dimensionless magnetic induction intensity ,in This represents the initial shear modulus of the film. Let be the permeability of free space. After deformation, the coordinates become... ,like Figure 2 As shown in (b).

[0028] The general solution of the incremental equilibrium equation is constructed as a linear combination of eigensols in the thin film and substrate regions. These solutions are then substituted into the boundary conditions to construct a homogeneous system of equations containing arbitrary constants. In this technical solution, the boundary conditions are extremely complex: they must not only satisfy the Stroh vector... In addition to ensuring continuity at the thin film-substrate interface, the following must also be considered: The vacuum domain (vacuum domain and air domain are the same in this invention) and The Maxwell stress in the hyperelastic substrate region is determined by the surface impedance method. This method exhibits excellent numerical robustness and allows for the derivation of analytical and asymptotic expressions for the dimensionless critical magnetic field.

[0029] The mechanical boundary conditions for the thin film-substrate structure are: (2) Right now At the interface, the stress vector of the thin film Subtract the stress vector of the substrate Equal to the stress vector corresponding to the vacuum domain . At this point, the stress vector of the thin film Equal to the stress vector corresponding to the vacuum region at that interface .in , This indicates the wavelength after the folds.

[0030] exist At the interface, displacement and potential are continuous, meaning the thin film is in and displacement in two directions and electric potential respectively with the base Consistency: (3) For the vacuum region: (4) in: , express The surface impedance matrix at that location.

[0031] Based on the above boundary conditions, two characteristic equations for the surface wrinkling instability of the thin film-substrate structure under the action of force-magnetic coupling field can be derived, as shown in Equation (5) and Equation (6), respectively.

[0032] (5) or: (6) in, They represent The surface impedance matrix corresponding to the thin film, substrate, and vacuum domain, with the superscript T indicating transpose. This indicates the ratio of shear modulus.

[0033] At this location, the surface impedance matrix corresponding to the thin film is: (7) and: (8) in, Represents the eigenvector matrix, From eigenvalues composition.

[0034] Equations (5) and (6) have different expressions, but the calculation results are consistent. When equation (5) or (6) is satisfied, there exists a nontrivial incremental solution, corresponding to the magnetic induction intensity. and the corresponding critical wavenumber ,in , Indicates the wavelength after folding. This indicates the thickness of the film after deformation. The minimum value corresponding to the curve is the critical magnetic flux density at which the thin film-substrate structure experiences surface wrinkling instability. .

[0035] when When smaller, ,in Represents the Stroh matrix. n This represents the number of terms in the asymptotic expansion. Therefore, we can obtain... m The approximate bifurcation equation is: (9) in, .

[0036] Given the energy density functions of the thin film and the substrate, the aforementioned parameters can be calculated. It is assumed that the thin film adopts a neo-Hookean ideal magnetoelastic model, and the substrate adopts a neo-Hookean model. The case of plane strain deformation is considered as follows: This deformation can be achieved by sandwiching the thin-film substrate structure between two fixed, lubricated rigid plates (the normal direction of the rigid plates is along the...). (direction), and along Applying mechanical loads in a certain direction, such as Figure 2 As shown in (b), the specific expressions for the surface impedance matrix in formulas (5) and (6) can be obtained: (10) In this case, for small shear modulus ratio Operating conditions, assumptions r yes kh Second-order small quantity Furthermore, the following explicit asymptotic expression can be obtained using asymptotic analysis: (11) in, (12) Since it is a high-order small quantity, it can be ignored directly; using the above asymptotic expression can significantly reduce the computational difficulty and time.

[0037] S16 applies an external magnetic field: A controllable magnetic field is applied using an electromagnet device, which mainly consists of an iron core, an excitation coil, and a current controller; alternatively, specialized electromagnetic loading equipment can be used directly to apply the magnetic field. The uniform area of ​​the applied magnetic field must completely cover the entire magnetoelastic thin film structure, and there must be no physical contact between the magnetic field loading unit and the thin film structure, thereby achieving non-contact remote actuation.

[0038] S17 implements intelligent optical surface control: An optical detection system was built to support this system. This system includes components such as a laser source, a photodetector, and an imaging panel, and is used to monitor the dynamic changes in the optical reflection state of the thin film surface in real time. By continuously and precisely controlling the magnetic induction intensity of the applied magnetic field, multi-level intelligent control of the optical properties of the magnetoelastic thin film structure surface is achieved. The specific control mechanism is shown in Table 1. Table 1 Optical Control Mechanism

[0039] in, This represents the critical magnetic flux density at which the magnetoelastic thin film-substrate structure experiences wrinkling instability. After the external magnetic field is removed, the elastic restoring force of the hyperelastic substrate can drive the thin film back to its initial flat state, achieving fully reversible control. In this embodiment, an external magnetic field is applied along the X2 direction. In other embodiments of the invention, magnetic fields can also be applied along other directions to drive the magnetoelastic thin film structure to wrinkle instability.

[0040] Experimental verification shows that the intelligent optical surface control method for magnetically driven wrinkle instability proposed in this invention can effectively achieve dynamic control of optical surface properties and complete non-contact, reversible, and programmable magnetic field control of optical surface wrinkle morphology, which has important theoretical value and engineering application significance. The core advantages of this method are as follows: (1) Non-contact remote drive: No physical connection is required, and remote control can be achieved by penetrating shielding objects, which fundamentally overcomes the inherent limitations of contact drive; (2) Fully reversible control: With the help of the elastic recovery characteristics of the superelastic substrate, the cycle stability is excellent; (3) Multi-level programmable continuous control: By continuously adjusting the magnetic induction intensity of the driving magnetic field, precise and continuous optical state control can be achieved between specular reflection and complete diffuse scattering; (4) Customized design as needed: By adjusting the shear modulus ratio, pre-compression / stretching and other parameters of the thin film substrate system, the instability trigger threshold can be flexibly designed; (5) Simple preparation process: No complex micro-nano processing is required, the process is simple, and it is easy to promote and apply on a large scale. Specific implementation examples: This embodiment focuses on the plane strain deformation condition: This deformation can be achieved by sandwiching the system between two fixed, lubricated rigid plates (the normal direction of the rigid plates is along the...). (direction), and along Applying external force in a certain direction, such as Figure 2 As shown in (b).

[0042] The specific steps in this embodiment are as follows: S11 Preparation of magnetoelastic thin film substrate structure: In this embodiment, the film is composed of an Ecoflex 00-50 superelastic silicone rubber matrix and soft magnetic carbonyl iron powder particles (particle size 5 mm) with a volume fraction of 20%. μm The film is fabricated using a composite material with a thickness of 0.8 mm. The substrate is made of Ecoflex 00-30 hyperelastic silicone rubber with a thickness of 19.2 mm. The overall dimensions are 40 mm (length), 40 mm (width), and 20 mm (height). The substrate thickness is 24 times that of the film thickness, and the substrate can be considered a semi-spatial structure. The fabrication process flow diagram of the magnetoelastic film-substrate structure is shown below. Figure 1 As shown in the diagram, the structural schematic is as follows: Figure 2 As shown.

[0043] S12 Determine the initial shear modulus of the film and the substrate: The initial shear modulus of the film was determined to be 10 kPa using standard testing methods, and the initial shear modulus of the hyperelastic substrate was 3 kPa.

[0044] S13 determines the magnetic susceptibility of the thin film: The initial magnetization curve of the thin film was measured using a SQUID-VSM (vibrating sample magnetometer), and the slope was taken to obtain the initial magnetic susceptibility. In this embodiment, the volume fraction of magnetic particles was 20%, and the relative magnetic susceptibility of the thin film was 0.4.

[0045] S14 applies a pre-compression / tension load: Applying plane strain constraints to the thin film-substrate structure, Direction applied uniaxial pretension ratio ,when Indicates compression. This indicates stretching, which is then maintained in a stable compressed state by a mechanical locking mechanism. For example... Figure 2 As shown in (b). Pre-stretch ratio The value can be adjusted according to the actual application requirements. Figure 3 Showing Results under three operating conditions. Figure 4 Showing Results under three operating conditions.

[0046] S15 Determine the dimensionless critical magnetic field for wrinkle instability in thin film-substrate systems. : Combined with the pre-stretch ratio given in S14 Substituting into formula (5) or formula (6), the dimensionless magnetic induction intensity of the thin film-substrate structure can be calculated. The curve, the minimum point of the curve is the dimensionless critical magnetic induction. ,like Figure 3 As shown in the figure. The solid line in the figure represents the exact solution, and the dashed line represents the 6th-order approximate solution calculated by formula (9). The approximate solution can significantly improve the calculation efficiency, and the calculation results are in high agreement with the exact solution. In practical engineering applications, the 6th-order approximate solution can be directly used for rapid calculation. Figure 3 It can be seen that the dimensionless critical magnetic induction intensity With shear modulus ratio r It increases with the increase of the pre-stretch ratio. At the same shear modulus ratio, it increases with the increase of the pre-stretch ratio. It increases with the increase of . At the same time, the result of the asymptotic solution can be calculated by formula (11), such as Figure 4 The application of pre-tension is given Dimensionless critical magnetic fields corresponding to three pre-stretch ratios Domain shear modulus ratio r The relationship curves are shown, with the solid line representing the exact solution and the dashed line representing the asymptotic solution. At small shear modulus ratios... r If the asymptotic solution results are consistent with the exact solution results, then the asymptotic solution expression can be used to calculate the critical magnetic field. This method can further improve the calculation efficiency and is more convenient for practical engineering applications.

[0047] S16 applies an external magnetic field: This embodiment employs specialized electromagnetic loading equipment to apply a magnetic field, ensuring that the uniform magnetic field area completely covers the magnetoelastic thin film-substrate structure. Furthermore, the magnetic field generating device has no physical contact with the thin film-substrate structure, achieving non-contact remote actuation. During loading, the magnetic induction intensity of the applied magnetic field is gradually increased starting from 0T, and the evolution of wrinkles on the structure surface is observed in real time until the magnetic field strength reaches and exceeds the critical magnetic field, providing the magnetic field conditions for step-by-step optical control.

[0048] S17 implements intelligent optical surface control: An optical inspection system was built, utilizing components such as a laser light source and an imaging panel to monitor the dynamic changes in the optical reflection state of the thin film surface in real time. The control process is shown in Figure 5, and is divided into three stages: 1) When an external magnetic field is applied When the thin film surface is smooth and flat, the incident light undergoes specular reflection, and a clear light spot appears on the imaging panel.

[0049] 2) When When this happens, micro-wrinkles appear on the surface of the thin film, causing partial scattering of the incident light, resulting in the light spot on the imaging panel widening and the appearance of a scattering halo.

[0050] 3) When At that time, the thin film showed obvious wrinkles, the specular reflection disappeared, the incident light was completely diffused, and the light spot on the imaging panel disappeared completely.

[0051] Those skilled in the art will understand that the embodiments of the present invention can be provided as methods, systems, or apparatus products. The embodiments described above are only some preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for controlling intelligent optical surface instability caused by magnetically driven wrinkles, characterized in that, Includes the following steps: S11 Preparation of magnetoelastic thin film structures: The magnetoelastic thin film structure is a pure thin film structure, or a thin film-substrate composite structure formed by bonding a thin film to a substrate; wherein, the thin film is a magnetic powder modified thin film, and the substrate includes a hyperelastic substrate or a magnetic substrate; The S12 test determines the initial shear modulus of the film and substrate materials in the magnetoelastic thin film structure. The S13 test determines the magnetic susceptibility of the thin film. ; S14 applies uniaxial or biaxial pre-compression / tension mechanical constraints to the magnetoelastic thin film structure and maintains a stable compression / tension state through a mechanical locking mechanism; S15 determined, through theoretical calculations, the dimensionless critical magnetic field that can cause wrinkling instability in magnetoelastic thin film structures. ; S16 applies an external magnetic field to the magnetoelastic thin film structure to ensure that a uniform magnetic field region covers the entire film, and that the magnetic field generating device has no physical contact with the magnetoelastic thin film structure, thereby achieving non-contact driving. S17 achieves intelligent optical control of the surface of the magnetoelastic thin film structure by adjusting the magnetic induction intensity of the applied external magnetic field, thereby enabling controllable switching of its surface optical reflection state.

2. The intelligent optical surface control method for magnetically driven wrinkling instability according to claim 1, characterized in that, The film is prepared by combining a superelastic material with magnetic iron powder particles, and the magnetic iron powder particles are uniformly dispersed in the superelastic matrix; the substrate is prepared by a superelastic material or by a superelastic material containing magnetic components.

3. The intelligent optical surface control method for magnetically driven wrinkling instability according to claim 1, characterized in that, In step S14, the magnetoelastic thin film structure is clamped in a mechanical loading device, with the center point of the thin film surface as the Cartesian coordinate system. The origin, pointing towards the base direction is X 2 directions, mechanical loading along X 3 directions, and along X Apply external force in direction 1.

4. The intelligent optical surface control method for magnetically driven wrinkling instability according to claim 3, characterized in that, In S15, the dimensionless critical magnetic field that causes the magnetoelastic thin film structure to wrinkle and become unstable is solved using the surface impedance method. Specifically: At the interface between the thin film and the substrate, the stress vector of the thin film minus the stress vector of the substrate equals the stress vector corresponding to the vacuum / air domain; at the interface between the thin film and the substrate, displacement and potential are continuous. At the interface between the thin film and the vacuum / air domain, the stress vector of the thin film is equal to the stress vector corresponding to the vacuum / air domain. Based on the above boundary conditions, two characteristic equations are obtained for the surface wrinkling instability of the thin film-substrate structure under force-magnetic coupling: ， or: ， in, These represent the surface impedance matrices at the thin film-substrate interface, and the corresponding regions in the thin film, substrate, and vacuum / air domains, respectively. The superscript T indicates matrix transpose. Indicates the ratio of shear moduli. and These are the initial shear moduli of the thin film and the substrate, respectively. , , Transmission matrix The submatrix, the transfer matrix, is a linear operator that describes the spatial transfer relationship of displacement, stress, and magnetic potential state vectors between different interfaces in thin films, substrates, and vacuum layered structures. It is used to satisfy the interface continuity condition and derive the characteristic equation of structural instability. When the above characteristic equation is satisfied, there exists a nontrivial incremental solution: corresponding to the magnetic induction intensity. and critical wavenumber , The minimum value corresponding to the curve is the critical magnetic flux density at which the thin film-substrate structure experiences surface wrinkling instability. ;when When the magnetoelastic thin film undergoes wrinkling and instability, the magnetic induction intensity is obtained. and critical magnetic induction intensity .

5. The intelligent optical surface control method for magnetically driven wrinkling instability according to claim 3, characterized in that, In S15, an approximate expression is used to describe the dimensionless critical magnetic field that causes wrinkling instability in the magnetically driven magnetoelastic thin film structure. To perform an approximate solution, specifically: m The approximate bifurcation equation is: ， in, n Indicates the number of terms in the asymptotic expansion. Representing the Stroh matrix n Power of; Represents the Stroh matrix. These represent the surface impedance matrices at the thin film-substrate interface, corresponding to the thin film, substrate, and vacuum region, respectively. The superscript T indicates matrix transpose. Indicates the ratio of shear moduli. and These are the initial shear moduli of the thin film and the substrate, respectively. Given the constitutive relations of the thin film and the substrate, the corresponding magnetic flux density can be calculated. and the corresponding critical wavenumber , The minimum value corresponding to the curve is the critical magnetic flux density at which the thin film-substrate structure experiences surface wrinkling instability. ;when When the magnetoelastic thin film undergoes wrinkling and instability, the magnetic induction intensity is obtained. and critical magnetic induction intensity .

6. The intelligent optical surface control method for driving wrinkle instability according to claim 3, characterized in that, In S15, an asymptotic expression is used to solve for the dimensionless critical magnetic field that causes wrinkling and instability of the magnetoelastic thin film structure under magnetic drive. Specifically: The explicit asymptotic expression is: ， in, ， In plane strain state X Deformation ratio in direction 1 Indicates the ratio of shear moduli. and These are the initial shear moduli of the thin film and the substrate, respectively. It is a high-order small quantity and can be ignored.

7. The intelligent optical surface control method for magnetically driven wrinkling instability according to claim 1, characterized in that, The optical surface manipulation specifically refers to: 1) When an external magnetic field is applied When the thin film surface is smooth and flat, it undergoes specular reflection, resulting in a clear light spot on the imaging panel used to detect the optical reflection state of the laser source. 2) When At this time, micro-wrinkles will appear on the surface of the thin film, and the light spot on the imaging panel will widen and a scattering halo will appear; 3) When At that time, the thin film showed obvious wrinkles, the specular reflection disappeared and turned into complete diffuse scattering, and the light spot on the imaging panel disappeared.

8. The intelligent optical surface control method for magnetically driven wrinkling instability according to claim 1, characterized in that, By adjusting the initial shear modulus of the film and substrate materials, and / or adjusting the pre-compression / tension applied in S14, the dimensionless critical magnetic field at which the magnetoelastic film structure experiences wrinkling instability can be altered. .

9. A smart optical surface control device for magnetically driven wrinkle instability, characterized in that, Includes a magnetoelastic thin film structure, a mechanical loading unit, and an external magnetic field loading unit; The magnetoelastic thin film structure is a pure thin film or a thin film-substrate structure consisting of a thin film and a substrate; the thin film is a magnetic powder modified thin film, and the substrate is a hyperelastic substrate or a magnetic substrate; The mechanical loading unit is used to apply pre-deformation to the magnetoelastic thin film structure, and the external magnetic field loading unit is used to apply a magnetic field to the magnetoelastic thin film structure. By controlling the magnetic induction intensity of the magnetic field, intelligent optical modulation of the surface of the magnetoelastic thin film structure is achieved, and the dynamic change of its optical reflection state is controlled.

10. The intelligent optical surface control device for magnetically driven wrinkling instability according to claim 9, characterized in that, The dimensionless critical magnetic field at which the magnetoelastic thin film structure experiences wrinkling instability is: When an external magnetic field is applied When the film surface is smooth and flat, specular reflection occurs on the film surface. At that time, micro-wrinkles and scattering halos appeared on the surface of the thin film. At that time, the film showed obvious wrinkles and completely diffuse scattering.

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