Optical strain sensor and preparation method and application thereof

Abstract

The invention discloses an optical strain sensor and a preparation method and application thereof, and belongs to the technical field of optical sensing. The optical strain sensor provided by the invention is composed of a flexible substrate and nanoparticles adhered to the flexible substrate, the nanoparticles are controlled by an optical tweezers system and are arranged in a patterned manner, and the deformation of the flexible substrate causes the change of gaps among the nanoparticles or the change of positions between the nanoparticles and the flexible substrate. And further, electromagnetic mode coupling among the nano-particles is influenced. The invention also provides a preparation method of the optical strain sensor. The preparation process is simple and can be expanded to any flexible substrate. The optical strain sensor prepared by the invention can detect micro-nano-scale weak strain through scattering intensity change, and can be applied to multi-channel information encryption by taking the substrate wrinkle two-dimensional material as the substrate.

Description

Technical Field

[0001] The present invention relates to the technical field of optical sensors, and in particular to an optical strain sensor and a preparation method and application thereof. Background Art

[0002] With the development of wearable technology, constructing strain-driven optical units on stretchable platforms is becoming increasingly important for applications such as health monitoring, medical treatment, and entertainment. From the perspective of flexible optomechanical systems, plasmonic nanostructures, either single or arrayed, can be used to achieve subwavelength modulation and sensing. However, dielectric nanostructures, which exhibit much lower thermal losses than plasmonic nanostructures, are a better choice for device integration. Silicon nanoparticles, with their high refractive index and low thermal loss, are suitable for integration at the subwavelength scale and enable full-color displays. Currently, most research on dielectric nanostructures is based on lattice effects for strain-tuned reflection or transmission, with limited research focusing on scattering tuning at the single-particle level. Although scattering measurements for each nanoparticle are complex, this approach can detect strain distributions at the micro- and nanoscale, which is not possible with macroscopic measurements. Furthermore, previous studies have required complex "top-down" fabrication methods to fabricate patterns on flexible substrates and achieve color modulation and strain sensing. Summary of the Invention

[0003] In view of this, in order to solve one of the above problems, the purpose of the present invention is to provide an optical strain sensor and its preparation method and application, which can detect micro-nanoscale strain by scattering and perform multi-channel information encryption and decryption.

[0004] On the one hand, the present invention provides an optical strain sensor comprising a flexible substrate and nanoparticles adhered to the flexible substrate, wherein the nanoparticles are manipulated and patterned by an optical tweezers system, and the deformation of the flexible substrate causes a change in the gap between the nanoparticles or a change in the position between the nanoparticles and the flexible substrate, thereby affecting the electromagnetic mode coupling between the nanoparticles.

[0005] Optionally, the material of the flexible substrate includes any one of polydimethylsiloxane (PDMS), polyimide, polyethylene, polyurethane, wrinkled two-dimensional material or skin.

[0006] Optionally, the shape of the nanoparticles includes spheres or spheroids, and the diameter of a single nanoparticle is in the range of 100-200 nm.

[0007] Optionally, the material of the nanoparticles includes a high-refractive-index all-dielectric nanomaterial, and the high-refractive-index all-dielectric nanomaterial includes any one of silicon (Si), germanium (Ge), tellurium (Te) or barium titanate (BaTiO3).

[0008] In another aspect, the present invention provides a method for preparing the optical strain sensor according to the above-mentioned solution, comprising:

[0009] Place the flexible substrate flat on the glass slide, with no bubbles on the contact surface;

[0010] Dropping a dispersed liquid containing nanoparticles on the flexible substrate, covering it with a cover glass to form a liquid environment in which the particles are dispersed, and then inverting the liquid environment on the sample stage of the optical tweezers system;

[0011] Turning on the illumination light of the optical tweezers system and adjusting it to a preset brightness, moving the sample stage and adjusting the focus, and determining a dark field clear image and the position of the flexible substrate;

[0012] Preheating the laser of the optical tweezers system, adjusting the optical tweezers potential well and exposure time to obtain the clearest imaging, and focusing the laser on the flexible substrate;

[0013] adjusting the power of the laser to capture the nanoparticles and arrange the nanoparticles in a pattern;

[0014] After the nanoparticles have completed adhesion, the sample is taken out, the cover glass is removed, and the sample is washed and dried.

[0015] Optionally, the dispersion containing nanoparticles is prepared by the following method:

[0016] The nanoparticles are added to deionized water, wherein the concentration of the nanoparticles is in the range of 0.05-0.2 mmol / L;

[0017] The ionized water containing the nanoparticles is uniformly dispersed by ultrasonication, wherein the ultrasonication time is 15-30 minutes and the ultrasonication frequency is 10-20 kHz.

[0018] Optionally, adjusting the optical tweezers potential well and exposure time includes:

[0019] Adjusting the potential well switching rate within the range of 1000-5000 Hz;

[0020] The exposure time was adjusted within the range of 20-50 ms.

[0021] Optionally, adjusting the power of the laser to capture the nanoparticles and arranging the nanoparticles in a pattern comprises:

[0022] The power of the laser is adjusted in the range of 10-50 mW to capture the nanoparticles,

[0023] The power of the laser is adjusted within the range of 200-400 mW to arrange the nanoparticles in a pattern.

[0024] The present invention uses an optical tweezers system to capture and pattern nanoparticles, that is, to print the nanopixels formed by the nanoparticles "from the bottom up". This is a simple and efficient preparation method with very low requirements for raw materials, and does not require the design of precise size and position, and does not require the use of complex and expensive equipment. It can even be extended to any flexible material that can disperse silicon nanopixels, and has extremely excellent applicability.

[0025] On the other hand, the present invention provides applications of the optical strain sensor described in the above scheme or the optical strain sensor obtained by the preparation method described in the above scheme in strain detection and multi-channel information encryption.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The optical strain sensor provided by the present invention uses all-dielectric nanoparticles with high refractive index and low heat loss as sensing nanopixels, and is assembled into a device by arranging them on a flexible substrate through a "bottom-up" method. The preparation process is simple, the requirements for raw materials are very low, and there is no need to design precise dimensions and positions. This preparation method can be extended to any other flexible material.

[0028] The optical strain sensor provided by the present invention utilizes single-particle nanopixels as separate sensing devices for the first time, converting stress changes into changes in the scattering spectrum. Moreover, due to the distance-sensitive Mie electromagnetic coupling characteristics of dielectric nanoparticles, dimer or oligomer nanopixels printed using optical tweezers exhibit stronger active tuning capabilities.

[0029] The optical strain sensor proposed by this invention combines silicon nanopixels with a wrinkled two-dimensional material. The spatially dependent coupling between the two improves tuning performance, making the strain-tuned scattering more pronounced. Furthermore, because the strain of the wrinkled two-dimensional material modulates the environment surrounding the nanopixels and the Kerker effect coupling between electromagnetic modes, the spectral response is more sensitive, with significant changes in the scattering response even under very small strain conditions.

[0030] In the optical strain sensor provided by the present invention, the coupling of nanopixels in the wrinkled two-dimensional material shows a strong correlation with the wrinkle state, which is specifically manifested in the increase, unchanged or decrease of the strain-tuned scattering intensity. This characteristic is used to record three changes in intensity in the red, green and blue channels respectively, and information can be stored in it, providing a new idea for multi-channel information encryption. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 1 is a schematic structural diagram of an optical strain sensor provided by an embodiment of the present invention;

[0032] Figure 2Schematic diagram of the capture and adhesion process of medium nanoparticles provided by an embodiment of the present invention;

[0033] Figure 3 This is a schematic diagram of the process of optical tweezers printing nanopixels and an optical topography of nanopixels under a dark-field microscope provided by an embodiment of the present invention;

[0034] Figure 4 is a schematic structural diagram of another optical strain sensor provided by an embodiment of the present invention;

[0035] Figure 5 The scanning electron micrographs of some nanopixels provided in the embodiments of the present invention, as well as the experimental scattering spectra and simulated scattering spectra before and after stretching, are shown;

[0036] Figure 6 10 nanopixel images of the optical strain sensor provided by an embodiment of the present invention at three different locations on a coin;

[0037] Figure 7 is a strain line graph of ten nanopixels at three positions provided by an embodiment of the present invention;

[0038] Figure 8 This is a graph showing changes in the scattering intensity of some pixels in the red, green, and blue channels, provided by an embodiment of the present invention;

[0039] Figure 9 1 is a graph showing the strain intensity change and the multi-base conversion result provided by an embodiment of the present invention;

[0040] Figure 10 This is a flow chart of independently performing optical encryption on the red, green and blue channels provided by an embodiment of the present invention;

[0041] Figure 11 This is a flow chart of optical decryption provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0042] On the one hand, the present invention provides an optical strain sensor comprising a flexible substrate and nanoparticles adhered to the flexible substrate. The nanoparticles are manipulated and patterned by an optical tweezers system. The deformation of the flexible substrate causes a change in the gap between the nanoparticles or a change in the position between the nanoparticles and the flexible substrate, thereby affecting the electromagnetic mode coupling between the nanoparticles.

[0043] It should be noted that nanoparticles include single particles, dimers or oligomers, etc. Nanoparticles form nanopixels, see Figure 1 .

[0044] Optionally, the material of the flexible substrate includes any one of polydimethylsiloxane, polyimide, polyethylene, polyurethane, wrinkled two-dimensional material or skin.

[0045] It should be noted that the material of the flexible substrate is determined according to actual application and is not specifically limited in this embodiment.

[0046] Optionally, the shape of the nanoparticles includes spheres or spheroids, and the diameter of a single nanoparticle is in the range of 100-200 nm.

[0047] It should be noted that the diameter range of the nanoparticles is determined according to actual applications and is not specifically limited in this embodiment. A spheroid can be understood as a sphere with a certain degree of error.

[0048] Optionally, the material of the nanoparticles includes a high-refractive-index all-dielectric material, and the high-refractive-index all-dielectric material includes any one of silicon, germanium, tellurium or barium titanate.

[0049] It should be noted that the material of the nanoparticles is determined according to actual applications and is not specifically limited in this embodiment.

[0050] The present invention also provides a method for preparing the optical strain sensor described in the above scheme, comprising:

[0051] Cut the flexible substrate into appropriate sizes and place it flat on the glass slide, ensuring there are no bubbles on the contact surface;

[0052] A dispersion containing nanoparticles is dropped onto the flexible substrate using a pipette, and another thin cover glass is gently placed on it to form a liquid environment in which the particles are dispersed, and the flexible substrate is then inverted on the sample stage of the optical tweezers system;

[0053] Turn on the illumination of the optical tweezers system, replace the lens with a darkfield lens, select an objective lens with the appropriate magnification, and adjust the brightness to the appropriate level. Move the sample stage so that the sample is directly above the focusing lens. Observe the sample through the eyepiece, adjust the focal length for the clearest darkfield image, and locate the flexible substrate.

[0054] Open the optical tweezers system computer software and preheat the optical tweezers system laser in advance. Adjust the corresponding optical tweezers potential well so that the image is displayed on the computer screen. Adjust the exposure time to achieve the best imaging effect on the screen. Fine-tune the focal length so that the 1064nm wavelength laser is focused on the substrate, that is, the particles can be captured at the substrate interface.

[0055] The software is calibrated to ensure that the captured particles are located in the center of the potential well, and the position, switch, and power of the potential well laser are controlled with the mouse. Specifically, the laser is turned on and adjusted to the appropriate power. The nanoparticles in the solution are attracted to the center of the beam waist and move downward due to the gradient force pointing to the center of the beam waist and the downward scattering force. At the same time, the focal length is adjusted so that the focal plane is located on the substrate surface. At this time, the nanoparticles are stably captured on the substrate surface. Then the laser power is increased. The adhesion force generated by the photothermal effect and the interaction force between molecules can achieve precise manipulation of the nanoparticles and controllable arrangement on the flexible substrate.

[0056] After the nanoparticles have completed adhesion, carefully remove the sample, remove the coverslip, gently rinse the residual suspension on the surface with deionized water, then use an ear bulb to blow dry the deionized water, and dry it in a dry, dust-free environment to obtain the sample to be used.

[0057] Alternatively, the dispersion containing nanoparticles is prepared by the following method:

[0058] The nanoparticles were added to deionized water, and the concentration of the nanoparticles ranged from 0.05 to 0.2 mmol / L;

[0059] The ionized water containing the nanoparticles is uniformly dispersed by ultrasonication, wherein the ultrasonication time is 15-30 minutes and the ultrasonication frequency is 10-20 kHz.

[0060] Optionally, adjusting the optical tweezers potential well and exposure time includes:

[0061] Adjusting the potential well switching rate within the range of 1000-5000 Hz;

[0062] The exposure time was adjusted within the range of 20-50 ms.

[0063] Optionally, adjusting the power of the laser to capture the nanoparticles and patterning the nanoparticles comprises:

[0064] The power of the laser is adjusted in the range of 10-50 mW to capture the nanoparticles.

[0065] The power of the laser was adjusted in the range of 200-400 mW to pattern the nanoparticles.

[0066] This invention utilizes an optical tweezer system to manipulate and print single nanoparticle pixels with subwavelength precision in a liquid environment. This allows for the controlled production of nanopixels, including single-particle, dimer, or oligomer structures. This simple and efficient method requires minimal raw materials, eliminates the need for precise size and placement, and eliminates the need for complex and expensive equipment. It can even be applied to any flexible material, demonstrating excellent applicability. It avoids the complex top-down manufacturing process for color tuning and strain sensing, overcomes the difficulty of nanoscaling traditional pixels, and reduces the heat loss associated with plasmonic metal nanopixels.

[0067] The present invention also provides a method for testing the dark-field scattering spectrum of nanopixels in the optical strain sensor described in the above scheme or the optical strain sensor prepared by the above scheme, and a method and technology for applying the method in strain detection, including:

[0068] The flexible substrate was fixed on a custom fixture, and the length of the substrate without stress was recorded;

[0069] Place the prepared sample on the sample stage to be tested, turn on the halogen lamp light source, adjust it to the appropriate brightness, adjust the focus to make the dark field imaging clearest, and find the pixel position to be tested;

[0070] Open the Light Field computer software, cool the sensor to -70°C, adjust the fixture as needed, adjust the pixel to the position corresponding to the slit test, fine-tune the focus to make the image of the pixel to be tested clearest on the software, adjust the appropriate integration time, select the appropriate grating, and click Acquire to collect the scattered light of the pixel to be tested;

[0071] The percentage change of the intensity of the characteristic peak of the spectrum is calculated to obtain the strain information.

[0072] Optionally, the suitable brightness is 5-20W.

[0073] Optionally, the suitable integration time is 0.05-0.5 ms.

[0074] Optionally, the suitable grating is 50-200g / mm.

[0075] It should be noted that the brightness and integration time of the light source are determined according to actual applications and are not specifically limited in this embodiment.

[0076] The present invention also provides a method for applying the optical strain sensor described in the above solution or the optical strain sensor obtained by the preparation method described in the above solution to multi-channel information encryption, comprising the following steps:

[0077] The flexible substrate is stretched to a certain extent, and the few-layer two-dimensional material is transferred onto the flexible substrate. The force of the stretching fixture is then removed to allow the flexible substrate to recover, at which point wrinkles are formed in the few-layer two-dimensional material.

[0078] A method for preparing nanopixels on a flexible substrate is used to print silicon nanopixels on a wrinkled two-dimensional material. Note that the printing position needs to be controlled at various locations on the wrinkles to achieve diversity and randomness of pixel positions.

[0079] Place the wrinkled two-dimensional material with nano-pixels under a dark-field microscope, turn on the illumination, find the pixel position to be measured, open the computer camera software Mshot, adjust the parameters and record the pixel position;

[0080] Narrowband filters with central wavelengths of 450nm, 550nm, and 675nm were added to the incident light path, and the brightness of each pixel after passing through the three narrowband filters (red, green, and blue) was recorded when the flexible substrate was stretched to 0%, 10%, and 20%.

[0081] The brightness changes when the stretching ratio is from 0 to 10% strain and from 10% to 20% strain can be recorded. The brightness decrease can be recorded as 0, the brightness unchanged can be recorded as 1, and the brightness increase can be recorded as 2. At this time, the state of a nanopixel from 0 to 10% and then to 20% can be recorded as two ternary numbers. Convert it into decimal or binary, and you can get the information you want to set according to your needs.

[0082] Optionally, when wrinkles are formed, the stretching ratio of the flexible substrate is 10%-30%, and the two-dimensional material can be one of tungsten disulfide (WS2), molybdenum disulfide (MoS2), molybdenum diselenide (MoSe2), tungsten diselenide (WSe2), graphene, (hexagonal boron nitride) hBN, etc. The thickness of the few layers is preferably 5nm-30nm.

[0083] Optionally, the height of the wrinkles and the distance between the peaks are related to the stretching ratio and the thickness. The peak height is preferably 100-300 nm, and the distance between the peaks is preferably 500-2000 nm.

[0084] Optionally, the bandwidth of the narrowband filter is 10 nm, and the brightness intensity reading is achieved with red, green, and blue (RGB) color acquisition software.

[0085] The present invention manipulates nanoparticles through optical tweezers and prints them on a flexible substrate. By testing the scattering of the nanoparticles on the flexible substrate under different applied stress states, it achieves sensing of stress changes. Furthermore, nanoparticles printed on a wrinkled two-dimensional material not only have a stronger ability to sense stress changes, but also exhibit different scattering responses in different bands, enabling information encryption. By using the numbering of silicon nanopixels and the selected RGB channels, the brightness information corresponding to the strain can be represented in various bases, and the nanopixel intensity information can be encrypted in the form of a QR code. Regardless of whether the key is binary, ternary, decimal, or the RGB channel and number of the nanopixel, the information can be decrypted, providing a new approach to micro- and nanoscale information encryption.

[0086] The optical strain sensor provided by the present invention, its preparation method and application are further described in detail below with reference to the accompanying drawings and specific embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0087] In the following examples, unless otherwise specified, all methods are conventional.

[0088] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0089] Example 1

[0090] An embodiment of the present invention provides a method for preparing an optical strain sensor based on a flexible PDMS substrate: the PDMS to be used is cut into 10mm*10mm squares. The protective layers on the top and bottom surfaces are gently removed with tweezers. The clean PDMS is then attached to a newly removed glass slide. Double-sided tape of equal thickness can also be adhered to the upper and lower edges of the flexible substrate to create a gap between the flexible substrate and the cover glass. A suspension containing silicon nanoparticles is ultrasonically cleaned for 30 minutes. The concentration of the silicon nanoparticle suspension is 0.05-0.2 mmol / L. 100-300 μL of the suspension is then dripped onto the PDMS. A cover glass is placed over the double-sided tape to create a liquid environment filled with particles above the PDMS, facilitating manipulation with optical tweezers. The sample to be processed is placed upside down on the sample stage of the optical tweezers system, with the cover glass at the bottom and the PDMS at the top. Turn on the optical tweezers system and let the laser preheat for 5 minutes. Replace the lens of the optical tweezers with a dark field lens and select an objective lens with a magnification of 60 times and a numerical aperture of 0.7. Adjust the dark field scattered light lens, sample, and objective lens to be on the same straight line. Adjust the various parameters in the optical tweezers software, add a potential well to manipulate the optical force, set the switching frequency to 2000Hz, the frame rate to 30FPS, the exposure time to 50ms, and the laser emitted by the optical tweezers to a Gaussian beam with a wavelength of 1064nm. The optical potential well power is set to 20mW. The nanoparticles are placed in the solution. Due to the effect of the Gaussian beam, the medium nanoparticles will be stably captured at the beam waist under the action of the light gradient force, and move toward the PDMS substrate interface in the Z direction along the direction of the light scattering force. When the particles move to the target position, due to the electrostatic force and van der Waals force between the particles and the substrate, they cannot directly and stably adhere to the substrate. Increasing the power of the optical potential trap to 200mW increases the gradient force and scattering force of the laser on the nanoparticles, allowing them to overcome the electrostatic force and van der Waals force repelling the particles. At this time, the nanoparticles can be adhered to the flexible substrate. The process of optical potential trap capturing and printing silicon nanoparticles onto a flexible substrate is shown in the figure. Figure 2 As shown, Figure 2 (a) is a schematic diagram showing the capture of silicon nanoparticles by optical potential traps. Figure 2 (b) shows the schematic diagram of silicon nanoparticle adhesion. Schematic diagram of the process of printing nanopixels with optical tweezers and the optical morphology of nanopixels under dark field microscope. Figure 3 As shown in the figure, particle selection is achieved through CCD imaging of the optical tweezers system. The optical tweezers system is switched to dark-field CCD imaging. The particles of appropriate size are roughly screened out by the scattering color of the particles in the aqueous solution, and multiple optical potential wells are added to manipulate the nanoparticles to the upper surface of the substrate. By increasing the potential well power, the selected nanoparticle aggregates or single particles are printed on the flexible substrate, and a dark-field optical topography of a 5*5 array of nanopixels printed on PDMS is given. The sensor structure formed after the nanopixel points on the flexible substrate PDMS are prepared is shown in the figure. Figure 1 As shown in the figure, the source of the color difference of nano-pixels is factors such as the size and number of silicon nanoparticles. The substrate is PDMS, and stress is applied to PDMS through a homemade elastic clamp, and the direction of stress application is parallel.

[0091] Example 2

[0092] An embodiment of the present invention provides another method for preparing an optical strain sensor based on wrinkled few-layer tungsten disulfide (WS2): Based on the above embodiment, in addition to printing nanopixels on PDMS, the printing method can also be extended to wrinkled few-layer WS2. In a specific embodiment, the PDMS to be used is first cut into a square of 10mm*10mm in size, and the protective layers on the upper and lower surfaces are gently removed with tweezers. The clean PDMS is fixed with a clamp, and the PDMS length is stretched to 12mm by the clamp. At this time, the few-layer WS2 is transferred to the PDMS by a dry transfer method, and the clamp is released to restore the PDMS to its initial state. At this time, wrinkles are formed on the few-layer WS2, and the subsequent nanoparticle printing process is consistent with the above embodiment. The sensor structure after the nanopixel points on the wrinkled few-layer WS2 are prepared is as follows. Figure 4 shown.

[0093] Example 3

[0094] The present invention also provides a strain detection application based on a scattering test technology of nano-pixels on a flexible substrate and optical strain sensing. The specific implementation process is as follows: in order to test the stress difference at different positions, the scattering intensity obtained by the tensile strain test is used for calibration. The scanning electron micrographs of some nano-pixels on the PDMS and the experimental scattering spectra and simulated scattering spectra before and after stretching are shown in FIG. Figure 5 As shown, the particle composition and size of pixels 1-4 have been marked in the scanning electron micrograph, which was obtained through experimental scattering spectrum testing and simulated scattering spectrum calculation before and after stretching. The black, blue and red lines represent the stretching ratios of 0%, 50% and 100% respectively. The results show that nanopixels can achieve optical sensing of stress, which is specifically manifested in the increase of spectral peak intensity, and the intensity change of nanopixels composed of multiple particles is more obvious. In order to further prove the optical sensing ability of nanopixels to stress, PDMS with nanopixels was attached to the coin, and the scattering of ten pixels at positions A, B and C was tested respectively. The pixel position to be tested was found under a dark field microscope, and the computer camera software Mshot was opened. The exposure time was adjusted to 100ms, and the position of the nanopixel to be tested was recorded by taking pictures. The PDMS containing the nanopixels to be tested was placed at three positions on the coin as shown below. Figure 6As shown. Open the Light Field computer software, cool the Sensor to -70℃, find the position of the pixel to be tested, adjust the pixel to be tested to the position corresponding to the slit test, fine-tune the focal length to make the image of the pixel to be tested clearest on the software, set the integration time to 0.5ms, select the grating density to 150g / mm, set the spectral center wavelength to 650nm, click Acquire to collect the scattered light of the pixel to be tested, measure the original spectral data, adjust other pixels to the position corresponding to the slit, repeat the steps to test different pixels at the same position of the coin, switch the position of PDMS on the coin after the test is completed, repeat the above steps to obtain the scattering data of nano-pixels at different positions, and obtain the scattering spectrum after data processing. The strain calculated by the change of scattering intensity of ten nano-pixels at three positions is as follows Figure 7 As shown, the tensile strain ratio corresponding to position A is 7.56%, the tensile strain ratio corresponding to position B is 1.64%, and the tensile strain ratio corresponding to position C is 3.67%.

[0095] Example 4

[0096] An embodiment of the present invention provides a multi-channel information encryption technology based on an optical strain sensor of a wrinkled two-dimensional material. Since the silicon nanopixels printed on the wrinkles WS2 exhibit wavelength selectivity in different strain scattering spectra, this characteristic is applied to multi-channel information encryption at the nanoscale. The specific implementation process is as follows: place the wrinkled two-dimensional material with nano-pixels under a dark field microscope, turn on the lighting, find the pixel position to be tested, open the computer camera software Mshot, set the exposure time to 300ms, and record the pixel position; add red, green and blue narrow-band filters to the incident light path, where the red narrow-band filter has a passing wavelength of 615-625nm, the green narrow-band filter has a passing wavelength of 525-535nm, and the blue narrow-band filter has a passing wavelength of 455-465nm. Record the brightness of each pixel after passing through the three narrow-band filters of red, green and blue when the flexible substrate is stretched to 0%, 10% and 20% respectively; record the brightness changes when the stretching ratio is from 0 to 10% strain and from 10% to 20% strain. The brightness reduction can be recorded as 0, the brightness unchanged as 1, and the brightness increase as 2. The scattering intensity change information of some pixels in the red, green and blue channels is as follows: Figure 8 As shown, the state of a nano pixel from 0 to 10% and then to 20% can be recorded as two ternary numbers, which can also be converted into decimal or binary. The specific conversion results are as follows Figure 9 This information can be read out independently on three channels. Since silicon nanopixels have different optical switching properties on RGB channels, optical encryption can be performed independently on the three RGB channels, as shown in Figure 2. Figure 10In addition, according to the universal standard ASCII characters, characters, numbers, uppercase and lowercase letters, and even abbreviations are defined, that is, they can be converted between binary, octal, decimal and characters. Since the intensity information of the silicon nanopixels on the wrinkled WS2 can also be expressed in binary, ternary and decimal forms, the nanopixel number and different RGB channels can be used as customized keys for decryption, as shown in the figure below. Figure 11 As shown, for example, the binary code corresponding to the capital letters 'Y ES' is '0101-1001 0100-0101 0101-0011', the corresponding decimal code is '5-9 4-55-3', the corresponding ternary code is '12-100 11-12 12-10', and the corresponding RGB channels and numbers of the nanopixels are 'blue 0-reverse green 4 red 8-blue 2 blue 0-red 9'. That is, the customized key, whether binary, ternary, decimal or nanopixel RGB channels and numbers, can be converted to each other to obtain the encrypted information 'YE S'.

[0097] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. An optical strain sensor, characterized in that: The system comprises a flexible substrate and nanoparticles adhered to the flexible substrate. The nanoparticles are precisely manipulated and patterned by an optical tweezers system. The deformation of the flexible substrate causes a change in the gap between the nanoparticles or a change in the position between the nanoparticles and the flexible substrate, thereby affecting the electromagnetic mode coupling between the nanoparticles.

2. The optical strain sensor according to claim 1, characterized in that The material of the flexible substrate includes any one of polydimethylsiloxane, polyimide, polyethylene, polyurethane, wrinkled two-dimensional material or human skin.

3. The optical strain sensor according to claim 1, wherein The shape of the nanoparticles includes spheres or spheroids, and the diameter of a single nanoparticle is in the range of 100-200 nm.

4. The optical strain sensor according to claim 1, wherein The material of the nanoparticles includes a high-refractive-index all-dielectric nanomaterial, and the high-refractive-index all-dielectric nanomaterial includes any one of silicon, germanium, tellurium or barium titanate.

5. A method for preparing an optical strain sensor, characterized in that: The optical strain sensor according to any one of claims 1 to 4 comprises: Place the flexible substrate flat on the glass slide, with no bubbles on the contact surface; Dropping a dispersed liquid containing nanoparticles on the flexible substrate, covering it with a cover glass to form a liquid environment for particle dispersion, and then inverting it on the sample stage of the optical tweezers system; Turning on the illumination light of the optical tweezers system and adjusting it to a preset brightness, moving the sample stage and adjusting the focus, and determining a dark field clear image and the position of the flexible substrate; Preheating the laser of the optical tweezers system, adjusting the optical tweezers potential well and exposure time to obtain the clearest imaging, and focusing the laser on the flexible substrate; adjusting the power of the laser to capture the nanoparticles and arrange the nanoparticles in a pattern; After the nanoparticles have completed adhesion, the sample is taken out, the cover glass is removed, and the sample is washed and dried.

6. The preparation method according to claim 5, characterized in that The dispersion containing nanoparticles is prepared by the following method: The nanoparticles are added to deionized water, wherein the concentration of the nanoparticles is in the range of 0.05-0.2 mmol / L; Deionized water containing the nanoparticles is uniformly dispersed by ultrasonication, wherein the ultrasonication time is 15-30 minutes and the ultrasonication frequency is 10-20 kHz.

7. The preparation method according to claim 5, characterized in that The adjusting the optical tweezers potential well and exposure time comprises: Adjusting the potential well switching rate within the range of 1000-5000H; The exposure time was adjusted within the range of 20-50 ms.

8. The preparation method according to claim 5, characterized in that The step of adjusting the power of the laser to capture the nanoparticles and arranging the nanoparticles in a pattern comprises: The power of the laser is adjusted in the range of 10-50 mW to capture the nanoparticles, The power of the laser is adjusted within the range of 200-400 mW to arrange the nanoparticles in a pattern.

9. Use of the optical strain sensor according to any one of claims 1 to 4 or the optical strain sensor obtained by the preparation method according to any one of claims 5 to 7 in strain detection and multi-channel information encryption.

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