A highly sensitive pressure sensor based on surface plasmons

Abstract

The present invention relates to the field of pressure sensing. The present invention provides a highly sensitive pressure sensor based on surface plasmonics, which includes a fixed mass block, a sliding mass block, a transparent elastic part, a photosensitive layer, a transparent substrate, and a photodetector. The photosensitive layer is composed of metal micro-nano structures distributed on the same plane. The photosensitive layer is completely embedded in the transparent elastic part. The fixed mass block and the sliding mass block are respectively fixedly connected to both ends of the transparent elastic part. The straight line where the connection line between the geometric centers of the contact surfaces of the fixed mass block and the sliding mass block with the transparent elastic is located is not perpendicular to the plane where the metal micro-nano structures are located. The transparent substrate is arranged on one side of the transparent elastic part. The fixed mass block is fixedly arranged at one end of the transparent substrate. The transparent elastic part and the sliding mass block are in close contact with the transparent substrate but not fixedly connected. The photodetector is fixedly arranged on the side of the transparent substrate away from the transparent elastic part. The sensor of the present invention has high sensitivity and accuracy, and is easy to integrate and fabricate.

Description

Technical Field

[0001] The present invention relates to the field of pressure sensing, and particularly to a highly sensitive pressure sensor based on surface plasmon Background Art

[0002] A pressure sensor can sense pressure and convert the pressure signal into other mechanical physical quantities, electrical physical quantities, optical physical quantities, etc. The pressure sensor that currently has the largest market share and is the most widely used is the one that converts mechanics into electrical signals. This type of pressure sensor utilizes the piezoelectric effect of materials or the capacitance change of capacitor components. Its sensitivity almost entirely depends on the piezoelectric effect of piezoelectric materials and the sensitivity of capacitor components. Preparing piezoelectric materials with excellent performance or capacitor components with high sensitivity is the main way to improve the sensitivity of this type of pressure sensor. However, it is difficult to further improve the piezoelectric performance of piezoelectric materials and the sensitivity of capacitor components. Therefore, it is very difficult to further improve the sensitivity of this type of pressure sensor, so that it cannot meet the demand for higher-sensitivity pressure sensors with the progress of science and technology. Based on this, pressure sensors that detect optical physical quantities have become a new research direction.

[0003] Pressure sensors that detect optical physical quantities are mainly divided into fiber-based and non-fiber-based pressure sensors, among which fiber-based pressure sensors are not easy to integrate. Surface plasmon is an electromagnetic mode formed by the interaction between free electrons and photons in the interface region between a metal and a dielectric. It was first proposed by Huffman et al. in 1957. He believed that when free electrons in a metal are excited by an external electromagnetic field, they will perform quantum oscillations, i.e., plasmons, in the background of positive ions. This phenomenon was first confirmed by Powell et al. in an experiment on a metal aluminum in 1959. When an electromagnetic wave irradiates on the interface between a metal and a dielectric, the free electrons on the metal surface undergo collective oscillations, and a near-field electromagnetic wave that propagates along the metal surface is formed by the coupling of the electromagnetic wave and the free electrons on the metal surface. Specifically, in the patent named "A nano-optical pressure sensor based on a surface plasmon resonance cavity" with the authorization announcement number "CN206019882U", a pressure detection device based on surface plasmon is disclosed; an external force to be measured acts on the cavity wall of a metal cavity, changing the shape of the metal cavity, thereby changing the surface plasmon resonance wavelength of the metal cavity. By detecting the change in the resonance wavelength, the pressure to be measured is detected; specifically, the detection process further includes an incident waveguide and an output waveguide that are directly coupled to the metal cavity, providing a detection loop. Due to the presence of directly coupled incident and output waveguides, the structure disclosed in this patent is not easy to integrate; at the same time, the incident waveguide and the output waveguide are directly coupled to the metal cavity, and the coupling efficiency is low, and only the change in the resonance wavelength is used to detect the pressure to be measured, which makes the response of the pressure sensor small, so the sensitivity and accuracy are not high.

[0004] In summary, the existing surface plasmon-based pressure sensors have problems such as being difficult to integrate, low sensitivity, and low accuracy. Summary of the Invention

[0005] To solve the above problems, the present invention provides a highly sensitive surface plasmon-based pressure sensor, which includes a fixed mass block, a sliding mass block, a transparent elastic part, a photosensitive layer, a transparent substrate, and a photodetector. The photosensitive layer is composed of metal micro-nano structures distributed on the same plane. The metal micro-nano structures are arranged periodically, and the size of the metal micro-nano structures is in the nanometer range. The material of the metal micro-nano structures is gold or silver. The metal micro-nano structures can be one layer or two layers. When there are two layers, the two layers can be the same or different. The metal micro-nano structures will generate localized surface plasmon resonance under the action of the light field, and the mode and intensity of the localized surface plasmon resonance are related to the relative position of the metal micro-nano structures and the surrounding medium environment. The photosensitive layer is completely embedded in the transparent elastic part. The shape of the transparent elastic part is a cuboid, and the material of the transparent elastic part is polymethyl methacrylate or transparent rubber. The stress change of the transparent elastic part can cause the deformation of the internal photosensitive layer. The fixed mass block and the sliding mass block are respectively fixedly connected to both ends of the transparent elastic part. The materials of the fixed mass block and the sliding mass block are hard materials, and the shapes of the fixed mass block and the sliding mass block are cuboids. The materials, shapes, and sizes of the fixed mass block and the sliding mass block are the same. The fixed mass block is used to fix one end of the transparent elastic part on the transparent substrate, and the sliding mass block is used to interact with the pressure to be measured. When the pressure to be measured acts on the sliding mass block, there is relative movement between the fixed mass block and the sliding mass block, which changes the stress condition of the transparent elastic part, thereby changing the relative position of the internal metal micro-nano structures. At the same time, the surrounding medium environment of the metal micro-nano structures also changes. The straight line connecting the geometric centers of the contact surfaces of the fixed mass block and the sliding mass block with the transparent elastic part is not perpendicular to the plane where the metal micro-nano structures are located, which can ensure that more light irradiates on the metal micro-nano structures. The transparent substrate is arranged on one side of the transparent elastic part. The fixed mass block is fixedly arranged at one end of the transparent substrate. The transparent elastic part and the sliding mass block are in close contact with the transparent substrate but not fixedly connected. The sliding mass block can slide on the transparent substrate. The material of the transparent substrate is silicon dioxide. The photodetector is fixedly arranged on the side of the transparent substrate away from the transparent elastic part, and is used to receive the transmitted light passing through the transparent substrate to obtain the transmission spectrum. The photodetector can be a CCD or a CMOS.

[0006] Advantages of the present invention: The present invention provides a highly sensitive pressure sensor based on surface plasmons. In the present invention, the photosensitive layer interacts with the optical field to generate the local surface plasmon resonance phenomenon. The surface electric field intensity of the photosensitive layer is relatively large, and the optical field energy is localized on the surface of the metal micro-nano structure, forming the energy distribution of the optical field. The transmission spectrum detected by the photodetector is closely related to the energy distribution of the optical field on the surface of the metal micro-nano structure. During detection, under the action of the pressure to be measured, the spacing, angle, and surrounding medium environment of the metal micro-nano structure embedded in the transparent elastic part all change. The spacing, angle, and surrounding medium environment of the metal micro-nano structure are closely related to the local surface plasmon resonance of the metal micro-nano structure and the optical field, as well as the intensity and mode of the local surface plasmon resonance coupling between adjacent metal micro-nano structures. Therefore, the energy distribution of the optical field on the surface of the metal micro-nano structure is closely related to the spacing, angle, and surrounding medium environment of the metal micro-nano structure. In the present invention, the transmission spectrum obtained by the photodetector is related to and closely related to the changes in the spacing, angle, and surrounding medium environment of the metal micro-nano structure. That is, when the pressure to be measured changes, the change in the transmission spectrum is relatively large. Therefore, the sensitivity of the sensor of the present invention is relatively high. Specifically, in the present invention, the change in the pressure to be measured is obtained jointly through the changes in the position of the transmission peak, the half-width of the peak, and the depth of the peak in the transmission spectrum. Therefore, the accuracy of the sensor of the present invention is relatively high. More specifically, the photosensitive layer is composed of metal micro-nano structures arranged periodically and with the same size, which is convenient for integration.

[0007] The following will further describe the present invention in detail with reference to the accompanying drawings. Description of the Drawings

[0008] Figure 1 is a schematic diagram of a highly sensitive pressure sensor based on surface plasmons;

[0009] Figure 2 is a top view of the photosensitive layer in the highly sensitive pressure sensor based on surface plasmons in Embodiment 2;

[0010] Figure 3 is the result of the electric field distribution on the surface of the metal micro-nano structure in Embodiment 2;

[0011] Figure 4 is the change in the transmission spectrum when the adjacent spacing of the metal nanostructure in Embodiment 2 changes;

[0012] Figure 5 is a top view of two layers of metal micro-nano structures in the highly sensitive pressure sensor based on surface plasmons in Embodiment 3.

[0013] In the figure: 1. Mass block; 2. Transparent elastic part; 3. Photosensitive layer; 4. Transparent substrate; 5. Photodetector. Detailed Embodiments

[0014] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the specific implementation manners, structural features and their effects of the present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

[0015] Embodiment 1

[0016] The present invention provides a highly sensitive pressure sensor based on surface plasmon, as Figure 1 shown. The pressure sensor includes a mass block 1, a transparent elastic part 2, a photosensitive layer 3, a transparent substrate 4, and a photodetector 5. The transparent elastic part 2 is transparent and elastic. The transparent material enables light to transmit through the transparent elastic part 2, and the elasticity enables the transparent elastic part 2 to deform. The material of the transparent elastic part 2 is polymethyl methacrylate or transparent rubber, and the refractive index is greater than 1, which can localize light in the transparent elastic part 2, enabling light to interact fully with the photosensitive layer 3. The shape of the transparent elastic part 2 is a cuboid. The cuboid is easy to integrate and fabricate, and can make the transparent elastic part 2 in close contact with the mass block 1 and the transparent substrate 4, especially with the transparent substrate 4, with a large contact area. In this way, the energy loss is less when light exits from the transparent elastic part 2 and enters the transparent substrate 4, so that the light energy finally entering the photodetector 5 is larger. Therefore, the response of the pressure sensor of the present invention is larger and the detection accuracy is higher. The photosensitive layer 3 is composed of a plurality of metal micro-nano structures arranged. The arrangement can be periodic or non-periodic. The plurality of metal micro-nano structures are distributed on a plane. The material of the metal micro-nano structures is gold or silver, and the size of the metal micro-nano structures is in the nanometer order. The photosensitive layer 3 is completely embedded inside the transparent elastic part 2 and is used to interact with light, causing the intensity of light to change. Specifically, when light irradiates on the photosensitive layer 3, a local surface plasmon resonance effect is generated on the surface of the metal micro-nano structures, causing the electric field energy to be localized on the surface of the metal micro-nano structures, thereby changing the energy of the transmitted light and further changing the transmission spectrum. More specifically, the intensity of the local surface plasmon resonance effect is closely related to the specific shape, relative position, and surrounding medium environment of the metal micro-nano structures.

[0017] There are two mass blocks 1, which are respectively fixedly connected to both ends of the transparent elastic part 2 and are also distributed at both ends of the photosensitive layer 3. That is, the plane where the photosensitive layer 3 is located is not perpendicular to the straight line where the connection line of the two mass blocks 1 is located. Preferably, the plane where the photosensitive layer 3 is located is parallel to the straight line where the connection line of the two mass blocks 1 is located. In this way, when the relative positions of the two mass blocks 1 change, the component of the force of the mass block 1 on the transparent elastic part 2 in the direction parallel to the plane where the photosensitive layer 3 is located is the largest. Furthermore, the force exerted by the transparent elastic part 2 on the photosensitive layer 3 in this direction is the largest, resulting in the largest deformation degree of the photosensitive layer 3, that is, the largest change in the relative position of the metal micro-nano structure. At the same time, the dielectric environment around the metal micro-nano structure also changes, and the intensity of the local surface plasmon resonance effect on the surface of the metal micro-nano structure changes the most, and the change in the intensity of the local electric field is the largest. As a result, the change in the energy of the transmitted light is relatively large, and the change in the transmission spectrum is relatively large. Therefore, the sensitivity of the pressure sensor of the present invention is relatively high. Specifically, the shapes, materials, and sizes of the two mass blocks 1 are exactly the same. In this way, when a force is applied, the contact conditions at both ends of the transparent elastic part 2 are the same, and the deformation degrees are consistent, so that no spurious peaks will appear in the transmission spectrum, and the detection accuracy of the method of the present invention is higher. More specifically, the material of the mass block 1 is an opaque hard material, such as a hard wooden board, hard alloy, etc. The opacity of the mass block 1 can prevent the light in the transparent elastic part 2 from leaking out from both ends. In this way, the interaction between the light and the photosensitive layer 3 is more sufficient, and the change in the intensity of the transmitted light is larger, that is, the change in the transmission spectrum is larger. Therefore, the sensitivity of the sensor of the present invention is relatively high; the material of the mass block 1 is a hard material, and the hard material is not easily deformed. When the stress to be measured acts on the transparent elastic part 2 through the hard mass block 1, the action of the force has no delay and there is no time error. Therefore, the detection accuracy of the sensor of the present invention is relatively high. The shapes of the two mass blocks 1 are cuboids, and the area of the side in contact with the transparent elastic part 2 is larger than the area of the transparent elastic part 2 on this contact surface. At the same time, the transparent elastic part 2 is not fixed at the center position of the contact surface between the two mass blocks 1. Preferably, the transparent elastic part 2 is fixed at the same-side edge of the contact surface between the two mass blocks 1. In this way, the transparent elastic part 2 and one surface of the two mass blocks 1 can be in the same plane, so that the transparent substrate 4 and the transparent elastic part 2 can be in close contact, reducing the loss of light field energy, thereby improving the accuracy and sensitivity of the sensor.

[0018] The transparent substrate 4 is disposed on one side of the transparent elastic part 2. Specifically, it is disposed on the side where the transparent elastic part 2 and the two mass blocks 1 are coplanar. The material of the transparent substrate 4 is a hard transparent material, which can be silicon dioxide. Specifically, one of the two mass blocks 1 is a fixed mass block for fixedly connecting the transparent elastic part 2 to one end of the transparent substrate 4, and the other is a sliding mass block for transmitting the pressure to be measured, so that the transparent elastic part 2 and the photosensitive layer 3 inside it are deformed. More specifically, the fixed mass block is fixedly connected to one side edge of the transparent substrate 4, and is fixedly connected to both the transparent substrate 4 and the transparent elastic part 2. The sliding mass block is fixedly connected to the transparent elastic part 2 and is in contact with but not fixedly connected to the transparent substrate 4. The transparent elastic part 2 and the transparent substrate 4 are in close contact but not fixedly connected. In this way, when the pressure to be measured acts on the sliding mass block, the sliding mass block moves along the surface of the transparent substrate 4, and the relative position between the sliding mass block and the fixed mass block changes, so that the transparent elastic part 2 and the photosensitive layer 3 inside it are deformed. Since the transparent substrate 4 is disposed on one side of the transparent elastic part 2, the transparent elastic part 2 and the photosensitive layer 3 inside it can only bend and deform away from the transparent substrate 4. In this way, on the one hand, since it can only deform in one direction, the change trend of the relative positions of the metal micro-nano structures in the photosensitive layer 3 is the same. The same change trend will make the directions of the generated local surface plasmons roughly the same, and the superposition effect is stronger. The inconsistent change trend will make the local surface plasmons in all directions cancel each other out, so that the superposition effect is weakened. Therefore, the present invention avoids the mutual cancellation of the interaction with the light field caused by the inconsistent change trend, which causes a greater change in the transmission spectrum, and the sensitivity of the sensor of the present invention is higher. On the other hand, the deformation on the side away from the transparent substrate 4 will make the distance between the metal micro-nano structures at the middle position of the photosensitive layer 3 in the transparent elastic part 2 and the light source closer. In this way, the local surface plasmon effect of the metal micro-nano structures at the middle position with the largest deformation amount is stronger than that of other metal micro-nano structures, so that the intensity of the transmitted light changes more, and the sensitivity of the sensor of the present invention is higher.

[0019] The photodetector 5 is fixedly arranged on one side of the transparent substrate 4 away from the transparent elastic part 2, and is used to detect the transmission spectrum of the light transmitted through the transparent substrate 4, so as to judge the change of the pressure to be measured. The photodetector 5 can be a CCD or a CMOS or any other type of photodetector. Specifically, the photodetector 5 is in close contact with the transparent substrate 4. Preferably, the connection line between the geometric centers of the contact part between the photodetector 5 and the transparent substrate 4 and the contact part between the transparent substrate 4 and the transparent elastic part 2 is perpendicular to the plane of the transparent substrate 4, and the area of the contact part corresponding to the photodetector 5 and the transparent substrate 4 is greater than or equal to the area of the contact part between the transparent substrate 4 and the transparent elastic part 2, so that the transmitted light can completely enter the photodetector 5, and the center of the transmitted light spot is located at the center of the photodetector 5, making the sensitivity of the photodetector 5 itself relatively high and the sensitivity of the sensor of the present invention relatively high. The size of the sensor of the present invention is on the order of millimeters or centimeters.

[0020] During application, the light source is arranged on the side of the transparent elastic part 2 away from the transparent substrate 4. The light source can be a broadband light source or a laser light source, and the incident light is incident perpendicular to the side of the transparent elastic part 2 away from the transparent substrate 4. The light of the light source irradiates into the transparent elastic part 2 and interacts with the photosensitive layer 3 embedded in the transparent elastic part 2. Specifically, the light irradiation generates a local surface plasmon resonance effect on the surface of the metal nanostructure in the photosensitive layer 3, and a strong electric field is generated on the surface of the metal nanostructure, making the light field energy localize on the surface of the metal nanostructure. More specifically, the strength of the generated local surface plasmon resonance effect is closely related to the deformation degree of the photosensitive layer 3 and the dielectric environment around the metal nanostructure. The light transmitted through the transparent elastic part 2 then passes through the transparent substrate 4 and enters the photodetector 5 to detect the transmission spectrum. During detection, the device of the present invention needs to be fixed in the environment to be measured. One end of the fixed mass block can be fixed, and the pressure to be measured acts vertically on the sliding mass block. Under the action of the pressure to be measured, the relative position of the sliding mass block and the fixed mass block changes. One end where the fixed mass block is located is fixed, and the end where the sliding mass block is located presses the transparent elastic part 2. This makes the stress distribution inside the transparent elastic part 2 uneven. On the one hand, the photosensitive layer 3 embedded inside the transparent elastic part 2 deforms, that is, the relative position of the metal nanostructure changes. On the other hand, the existence of stress makes the density distribution of the transparent elastic part 2 uneven, and the local refractive index of the transparent elastic part 2 changes, that is, the dielectric environment of the metal nanostructure changes. The change in the dielectric environment and the change in the relative position of the metal nanostructure make the intensity of the local surface plasmon resonance effect between the metal nanostructure and the light field change. As a result, the distribution and localization degree of the strong electric field on the surface of the metal nanostructure change, the absorption of the photosensitive layer 3 to the light field changes, the light field energy distribution changes, and the transmission spectrum changes. Since the intensity of the local surface plasmon resonance effect strictly depends on the change in the dielectric environment and the change in the relative position of the metal nanostructure, and at the same time depends on the change in the dielectric environment and the change in the relative position of the metal nanostructure, therefore, under the same change in the pressure to be measured, the change in the transmission spectrum in the present invention is larger, that is, the sensitivity of the sensor of the present invention is higher.

[0021] More specifically, the changes in the relative positions between the metal micro-nano structures include translation and rotation. The change in the local surface plasmon resonance effect caused by translation is mainly the change in the strength of the local surface plasmon resonance coupling within the plane where the metal micro-nano structures are located; the change in the local surface plasmon resonance effect caused by rotation is mainly the change in the local surface plasmon resonance coupling mode in the direction perpendicular to the plane where the metal micro-nano structures are located, that is, the local surface plasmon resonance coupling mode of the metal micro-nano structures changes with the deformation of the photosensitive layer 3. In the transmission spectrum, it is manifested as the movement of the transmission peak and the change in the corresponding half-width; in the transmission spectrum of the sensor of the present invention, there are not only changes in the magnitude of the transmission coefficient (corresponding to the depth of the transmission peak in the transmission spectrum), but also changes in the resonance wavelength (corresponding to the position of the transmission peak in the transmission spectrum), and changes in the half-width of the peak corresponding to the resonance wavelength (corresponding to the half-width of the transmission peak in the transmission spectrum). The change in the pressure to be measured in the present invention is reflected in multiple characteristics of the transmission spectrum, so the sensor of the present invention has a high sensitivity. Since one side of the transparent elastic part 2 is in contact with the transparent substrate 4, the generated deformation is manifested as a greater deformation of the metal micro-nano structures at the middle position, including both greater translation and rotation, and the degree of deformation gradually weakens towards both sides. At the same time, the rotation directions are symmetric on both sides, that is, the metal micro-nano structures close to the fixed mass block rotate counterclockwise, and the metal micro-nano structures close to the sliding mass block rotate clockwise. This can make the middle position with the largest deformation degree closer to the light source, enhance the intensity of the local surface plasmon resonance effect, and enhance the change in the transmission spectrum. The sensor of the present application has a high sensitivity. During the detection process of the sensor of the present invention, there is always contact between the transparent elastic part 2 and the transparent substrate 4 without a gap. When the pressure to be measured is too large, there will be a gap between the transparent elastic part 2 and the transparent substrate 4 of the sensor of the present invention. Therefore, the sensor of the present invention is suitable for detecting weak pressure changes.

[0022] Example 2

[0023] On the basis of Example 1, on the exposed two side surfaces of the transparent elastic part 2, that is, as Figure 1Two planes parallel to the ZX plane as shown, and a reflective film is fixedly arranged on the outer surface of the transparent substrate 4 that does not contact the photodetector 5, the mass block 1, and the transparent elastic part 2. Specifically, due to the good reflection characteristics of metallic silver and the fact that a metallic silver film with a thickness greater than 500 nm can ensure a high reflectivity, the material of the reflective film is metallic silver with a thickness greater than 500 nm. Further, since the transparent elastic part 2 has elasticity, the thickness of the reflective film on it needs to be greater than the thickness of the metallic silver film on the transparent substrate 4. In this way, during the deformation process, a good reflection effect can be ensured during the detection within the range of the pressure to be measured, ensuring that the light emitted by the light source does not leak. At the same time, the light is reflected multiple times by the reflective film and interacts fully with the photosensitive layer 3 within the transparent elastic part 2, making the local surface plasmon resonance effect stronger and the change in the transmission spectrum greater, so that the sensitivity of the sensor of the present invention is higher. Specifically, metallic silver can be prepared by an evaporation coating process.

[0024] The photosensitive layer 3 is embedded on the side close to the transparent substrate 4. When the pressure to be measured acts on the sliding mass block, taking the plane where the photosensitive layer 3 is located as the boundary, the volume of the transparent elastic material on the side close to the transparent substrate 4 is smaller than that of the transparent elastic material on the side far from the transparent substrate 4. Thus, the extrusion degree of the transparent elastic material on the side close to the transparent substrate 4 is stronger than that of the transparent elastic material on the side far from the transparent substrate 4. Therefore, the force exerted by the transparent elastic material on the side close to the transparent substrate 4 on the photosensitive layer 3 is greater than the force exerted by the transparent elastic material on the side far from the transparent substrate 4 on the photosensitive layer 3. This makes the photosensitive layer 3 more prone to deformation, causing the metal micro-nano structure in the middle position to be closer to the side of the transparent elastic part 2 far from the transparent substrate 4. In this way, on the one hand, the part with the largest deformation in the middle is closer to the light source, and the interaction with the light field is stronger. For the same degree of deformation, the change in the intensity of the local surface plasmon resonance effect generated on the metal micro-nano structure in the middle position is larger, that is, the change in the light field energy distribution is larger, the change in the light field energy locally absorbed by the photosensitive layer 3 is larger, the change in the transmission spectrum is larger, and the sensitivity of the sensor of the present invention is higher. On the other hand, the rotation degree of the metal micro-nano structure increases. The greater the rotation degree of the metal micro-nano structure, correspondingly, the greater the change in the local surface plasmon resonance coupling mode in the direction perpendicular to the plane where the metal micro-nano structure is located, and the greater the change in the position and half-width of the transmission peak in the transmission spectrum. The sensitivity of the sensor of the present invention is higher. More specifically, the vertical distance from the transparent substrate 4 can be less than 300 nm, so that the photosensitive layer 3 is closer to the interface between the transparent elastic part 2 and the transparent substrate 4, facilitating the improvement of the interface to enhance the sensitivity of the sensor of the present invention. At the same time, the stress change of the transparent elastic material around the metal micro-nano structure is large, the density change of the transparent elastic material is large, and the refractive index change of the transparent elastic material is large, that is, the change in the medium environment around the metal micro-nano structure is large, the change in the local surface plasmon resonance between the metal micro-nano structure and the light field is large, thereby the change in the light field energy distribution is large, the change in the transmitted light is large, and the change in the transmission spectrum is large. Therefore, the sensitivity of the sensor of the present invention is higher.

[0025] More specifically, the arrangement of the metal micro-nano structures constituting the photosensitive layer 3 can be periodic or random. Preferably, the metal micro-nano structures are arranged periodically, so that the local surface plasmon resonance of each metal micro-nano structure is similar, and the resonance modes in all directions are superimposed and enhanced with each other, and the resonance modes in all directions will not cancel each other out. As a result, the overall resonance is enhanced, the local characteristics of the optical field energy are stronger, during detection, the change in energy distribution is greater, the change in transmitted light is greater, and the change in the transmission spectrum is greater. Therefore, the sensor of the present invention has higher sensitivity. More preferably, the spacing of the periodic arrangement, that is, the spacing between adjacent metal micro-nano structures, is less than 500 nm, so that the change in the coupling mode between adjacent metal micro-nano structures can be maximized, and thus the sensor of the present invention has relatively high sensitivity; when the spacing is too large, there will be no coupling effect between adjacent metal micro-nano structures, and when the spacing is too small, a slightly larger deformation degree will cause the metal micro-nano structures to contact or even squeeze each other, causing irreversible damage to the metal micro-nano structures, resulting in a smaller detection range. The shape of the metal micro-nano structures can be any shape, and the size is in the nanometer order. Specifically, as Figure 2 shown, it is a top view of the photosensitive layer 3. In this embodiment, the metal micro-nano structure is composed of a cuboid and two spheres. The height of the cuboid is equal to the diameter of the spheres, which is convenient for integrated preparation. More specifically, the two spheres are respectively located on the opposite sides of the two ends of the cuboid and are tangent to the side surface of the cuboid. The straight line where the two tangent points are located is perpendicular to the side surface of the cuboid and is located at the midpoint of the height of the cuboid. After such a periodic arrangement, the resonance modes of the sphere and the side surface of the cuboid can be generated on each side surface of the adjacent metal micro-nano structures. Since the sphere is tangent to the side surface of the cuboid and the electric field distributions are quite different, the resonance intensity of the resonance modes of the sphere and the side surface of the cuboid is relatively large, and the transmission peaks on the transmission spectrum are relatively obvious. The changes in the position, intensity, and half-width of the corresponding transmission peaks are relatively obvious. As Figure 3 shown, it is the result of the electric field distribution simulated by COMSOL software. Among them, different brightness levels represent different electric field intensities. The dark areas represent larger electric field intensities, and the bright areas represent smaller electric field intensities. The areas with stronger electric field intensities are the areas with stronger resonance. Different distributions represent different resonance modes. From Figure 3It can be seen that the electric field at the contact between the side surface of the cuboid and the sphere is strong, indicating a strong resonance between the sphere and the side surface of the cuboid. Two spheres are arranged at both ends of the cuboid. When the metal micro-nano structure rotates, the more prominent sphere is more likely to generate resonance coupling with the side surface of the adjacent cuboid, generating a new coupling mode. The opposite-side setting makes it easy to generate a new coupling mode with the side surface of the adjacent cuboid in any rotation direction. The generation and change of the coupling mode are more easily observed in the transmission spectrum. Specifically, it is manifested as the appearance of a new transmission peak and the change in the position of the transmission peak. Since the change in the position of the transmission peak caused by the change in the coupling mode is large, the sensitivity of the sensor of the present invention is high. The height of the cuboid in the metal micro-nano structure is 50 - 100 nm, the length of the cuboid is 600 - 1000 nm, and the width is 100 - 300 nm. Figure 4 For the change of the transmission spectrum when the spacing between adjacent metal nanostructures changes, where the three curves are the transmission spectra when the spacing is 20 nm, 50 nm, and 200 nm respectively. Figure 4 It can be seen that there are three main transmission peaks, which are 400 - 500 nm, 500 - 600 nm, and 1200 - 1600 nm respectively. Among them, the change in the resonance mode in the range of 1200 - 1600 nm is the most obvious with the change in the spacing. Specifically, the position, half-width, and intensity of the corresponding peak have all changed. This shows that the change in the spacing can be clearly observed in the transmission spectrum. Based on this, the change in the spacing can be obtained according to the change in the peak in this range. Further, by comprehensively considering the change in the characteristic peak of the rotation change, the change in the characteristic peak of the medium environment change, etc., the change in the pressure to be measured can be accurately obtained.

[0026] Example 3

[0027] On the basis of Example 2, the photosensitive layer 3 is two layers of metal nanostructures. Specifically, the shapes, sizes, and arrangements of the two layers of metal nanostructures can be the same or different. The additional layer can be arranged on the side of the photosensitive layer 3 close to the transparent substrate 4 or on the side of the photosensitive layer 3 far from the transparent substrate 4. Preferably, as Figure 5 shown, the shapes and sizes of the two layers of metal nanostructures are the same, which is convenient for integrated preparation. The metal micro-nano structure of the other photosensitive layer 3 is perpendicularly arranged to the metal micro-nano structure in Example 2. The straight line where the connection line of the geometric centers of the corresponding metal micro-nano structures is located is perpendicular to the plane where the metal micro-nano structure is located. That is, after the perpendicularly arranged metal micro-nano structure rotates, the resonance modes on the corresponding two cuboids can be coupled with each other, and the spheres at the corresponding positions can also be coupled with each other. The height difference between the two layers of metal micro-nano structures is 300 - 500 nm, so that a coupling effect can be generated between the two layers of metal micro-nano structures, making the change in the energy distribution of the photosensitive layer 3 related to the change in the spacing between the two layers of metal micro-nano structures, the coupling between the two layers of metal micro-nano structures, and the change in the medium environment.

[0028] Specifically, when the metal micro-nano structure has two layers, on the one hand, the stress distribution in the transparent elastic material part 2 is more uneven, making the density distribution of the transparent elastic material more uneven, and thus the refractive index of the transparent elasticity more uneven. During detection, the change in the medium environment around the metal micro-nano structure layer is greater. Therefore, the change in the local surface plasmon resonance between the metal micro-nano structure and the light field is greater, the change in the transmitted light is greater, the change in the transmission spectrum is greater, and the sensor sensitivity is relatively high. On the other hand, when the transparent elastic part 2 deforms, it will cause the change in the layer spacing of the two-layer metal micro-nano structure. Due to the bending deformation, the degree of spacing change at each position is different. The spacing change in the middle position is the largest, and the spacing change near both sides is smaller. That is, the change in the local surface plasmon resonance coupling intensity caused by the change in the spacing of the metal structure in the middle position is relatively large, the change in the transmitted light is relatively large, and the change in the transmission spectrum is relatively large. Therefore, the sensitivity of the sensor of the present invention is relatively high. On the further hand, when the metal nano-structure has two layers and the transparent elastic part 2 deforms, the rotation of the metal nano-structure will cause resonance coupling at local positions that originally did not produce coupling resonance between the two layers. Specifically, the metal micro-nano structures perpendicularly arranged in the XY plane and the ZX plane will both rotate. The rotation in the XY plane makes the corresponding metal nano-structures in the two layers no longer perpendicular, so that the resonance coupling intensity and resonance coupling mode in the Z direction between the corresponding spheres in the two-layer metal nano-structures change. The half-width of the transmission peak corresponding to the coupling between the spheres is relatively small, and it is easy to distinguish the transmission peaks with smaller changes. Therefore, the sensitivity of the sensor of the present invention is relatively high; at the same time, the rotation in the XY plane makes the shape of the corresponding overlapping part of the corresponding cuboid no longer a square, that is, the corresponding coupling area changes, causing the electric field distribution to change, and the position and half-width of the corresponding transmission peak change, that is, the change in the transmission spectrum is greater, and the sensitivity of the sensor of the present invention is higher. The rotation in the ZX plane makes the change in the distance between the corresponding spheres greater, the change in the intensity of the corresponding local surface plasmon resonance greater, the change in the light field energy distribution greater, and the change in the transmission spectrum greater. The sensitivity of the sensor of the present invention is higher; at the same time, the rotation in the ZX plane will cause resonance coupling in the cuboid area that originally did not produce resonance coupling or strong resonance coupling in the area that originally had weak resonance coupling, that is, the change in the intensity and mode of resonance coupling on the cuboid is greater, and the change in the electric field distribution on it is greater. Therefore, the sensitivity of the sensor of the present invention is relatively high.

[0029] Example 4

[0030] Based on Example 3, metal nanoparticles are fixedly arranged at the interface between the transparent elastic part 2 and the transparent substrate 4. Specifically, they are fixedly arranged on the surface of the transparent substrate 4. The material of the metal nanoparticles is gold or silver. The shape of the metal nanoparticles is spherical, and the size of the metal nanoparticles is 50 - 500 nm. The area of the region where the metal nanoparticles are arranged is larger than the contact surface between the transparent elastic part 2 and the transparent substrate 4, so that the light entering the photodetector 5 all passes through the metal nanoparticles. Specifically, on the one hand, the metal nanoparticles generate a local surface plasmon resonance effect in the optical field, and there is a strong electric field locally on the surface of the metal nanoparticles. Since the vertical distance between the metal nanostructure and the transparent substrate 4 is less than 300 nm, that is, there is a local surface plasmon resonance coupling phenomenon between the metal nanoparticles and the two-layer metal micro-nano structure, which makes the electric field distributions on the surfaces of the metal nanoparticles and the two-layer metal micro-nano structure affect each other, changes the coupling strength, and generates a new coupling mode. When the transparent elastic part 2 is stressed, both the distance and the relative angle between the metal micro-nano structure and the metal nanoparticles change, resulting in a change in the electric field distribution on the surfaces of the two-layer metal micro-nano structure and the metal nanoparticles, that is, the resonance mode changes and the transmission spectrum changes. The change in distance mainly changes the intensity of the coupled resonance, and the change in the relative angle mainly changes the mode of the coupled resonance; the layer of the two-layer metal micro-nano structure closer to the metal nanoparticles has a greater influence on the electric field distribution of the metal nanoparticles, and the layer farther away from the metal nanoparticles has a smaller influence on the electric field distribution of the metal nanoparticles. The electric field distribution of the layer of the metal micro-nano structure closer to the metal nanoparticles is closely related to the electric field distributions on the surfaces of the other layer of the metal micro-nano structure and the metal nanoparticles, that is, the two-layer metal nanostructures and the metal nanoparticles affect each other, enhancing such as Figure 1The resonant coupling in the Z direction shown makes the intensity of the resonant coupling and the mode of the resonant coupling change more, and the change of the transmission spectrum is greater, so the sensitivity of the sensor of the present invention is higher. On the other hand, one side of the metal nanoparticle contacts the hard transparent substrate 4, and one side elastically contacts the transparent elastic part 2, that is, the difference in the refractive index of the contact medium on both sides is large. During detection, the pressure to be measured will not cause the transparent substrate 4 to deform, that is, the refractive index of the transparent substrate 4 does not change with the change of the pressure to be measured, and the refractive index of the transparent elastic part 2 will change with the change of the pressure to be measured. That is, the surface electric field distribution characteristics of the metal nanoparticles are different from those of the metal micro-nano structure completely embedded in the transparent elastic part 2, which is specifically reflected in that the position of the transmission peak on the transmission spectrum is far apart, so that it can be easily identified on the transmission spectrum and is not easily mixed with other spectrum lines, so that the sensitivity of the sensor is higher. On the other hand, the hardness of the metal nanoparticles is greater than that of the transparent elastic material, so that the stress conditions of the transparent elastic material around it change more, and the refractive index changes more, that is, the medium environment around the metal nanoparticles changes more, the intensity and mode of the local surface plasmon resonance of the metal nanoparticles in the light field change more, the electric field distribution on the surface of the metal nanoparticles changes more, and the transmission spectrum changes more. Therefore, the sensitivity of the sensor of the present invention is higher; at the same time, the change in the intensity of the coupled resonance caused by the change in distance is greater, and the change in the resonance mode caused by the change in the relative angle is greater, thereby the change in the transmission spectrum is greater. Therefore, the sensitivity of the sensor of the present invention is higher.

[0031] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A highly sensitive pressure sensor based on surface plasmons, characterized in that, The pressure sensor includes a fixed mass block, a sliding mass block, a transparent elastic part, a photosensitive layer, a transparent substrate, and a photodetector. The photosensitive layer is composed of two layers of metal micro-nano structures. The metal micro-nano structures are arranged periodically, and the distance between adjacent metal micro-nano structures in the same layer is less than 500 nm. The photosensitive layer is completely embedded in the transparent elastic part. The fixed mass block and the sliding mass block are respectively fixedly connected to both ends of the transparent elastic part. The straight line where the geometric centers of the contact surfaces of the fixed mass block and the sliding mass block with the transparent elastic part are located is not perpendicular to the plane where the metal micro-nano structures are located. The transparent substrate is arranged on one side of the transparent elastic part. The fixed mass block is fixedly arranged at one end of the transparent substrate. The transparent elastic part and the sliding mass block are in close contact with the transparent substrate but not fixedly connected. The sliding mass block can slide on the transparent substrate. The photodetector is fixedly arranged on the side of the transparent substrate away from the transparent elastic part. The metal micro-nano structure is composed of a cuboid and two spheres. The height of the cuboid is equal to the diameter of the sphere. The two spheres are respectively located on the opposite sides of both ends of the cuboid and are tangent to the side surface of the cuboid. The straight line where the two tangent points are located is perpendicular to the side surface of the cuboid and is located at the midpoint of the height of the cuboid. The straight line where the geometric centers of the two layers of metal micro-nano structures are located is perpendicular to the plane where the two layers of metal micro-nano structures are located, that is, after the vertically arranged metal micro-nano structures are rotated, the resonance modes on the corresponding two cuboids can be coupled with each other, and the spheres at the corresponding positions can also be coupled with each other. In the top view direction, the length extension directions of the two nearest corresponding cuboids in the two layers of micro-nano structures are cross-shaped.

2. The highly sensitive pressure sensor based on surface plasmon as claimed in claim 1, wherein: The size of the metal micro-nano structure is at the nanometer order of magnitude.

3. The highly sensitive pressure sensor based on surface plasmon as claimed in claim 2, wherein: The shapes of the transparent elastic part, the fixed mass block, and the sliding mass block are cuboids.

4. The highly sensitive pressure sensor based on surface plasmon as claimed in claim 3, wherein: The shapes, sizes, and materials of the fixed mass block and the sliding mass block are the same.

5. The highly sensitive pressure sensor based on surface plasmon as claimed in claim 1, wherein: The material of the metal micro-nano structure is gold or silver.

6. The highly sensitive pressure sensor based on surface plasmon as claimed in claim 1, characterized in that: The material of the transparent substrate is silicon dioxide.

7. The highly sensitive surface plasmon resonance-based pressure sensor according to claim 1, characterized in that: The material of the transparent elastic part is transparent rubber.

8. The highly sensitive surface plasmon-based pressure sensor according to claim 1, wherein: The photodetector is a CCD or a CMOS.

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