Bifunctional water-based metamaterial sensor and applications thereof

Abstract

The application provides a kind of bifunctional water-based metamaterial sensor and its application, the sensor is composed of multiple unit structures, unit structure includes resin shell, its inside is equipped with the cavity for filling water structure, resin shell bottom is equipped with metal plate.The water-based sensor provided by the application can realize frequency amplitude double sensing function compared with general metamaterial sensor, and can be bidirectionally detected;It realizes double-peak resonance, and has high sensitivity.During detection, the measured object is directly coated on the upper surface of the sensor, and the experiment can be repeated after cleaning, which ensures the reuse of the sensor and greatly reduces the cost;The sensor has simple structure and superior performance, and is suitable for most biological detection, and the detection wave band is gigahertz wave, which is conducive to the popularization and application of the sensor.

Description

Technical Field

[0001] This invention belongs to the field of metamaterial sensor technology, specifically relating to a dual-functional water-based metamaterial sensor and its applications. Background Technology

[0002] Metamaterials are artificial composite materials composed of periodically arranged units. By adjusting the shape, size, and distribution of their unit structures, they can exhibit many unusual physical phenomena that are impossible with traditional materials found in nature. Among these, the amplification of evanescent electromagnetic waves by metamaterials makes them sensitive to the dielectric properties of their surroundings, thus enabling their use in sensing to detect small amounts of analytes. Metamaterial biosensors, as a novel detection method, can overcome the resolution limitations of traditional sensors, enabling label-free detection. They also offer advantages such as small sample volume, high sensitivity, label-free detection without the need for additional reagents, fast response, and simple measurement. Currently, research on this sensor mainly focuses on microwave, terahertz, and optical bands, with limited research in the gigahertz millimeter-wave band.

[0003] Currently, the main materials used in metamaterial sensors are mostly ordinary and noble metals, graphene, carbon nanotubes, silicon, multi-element materials, and hybrid metamaterials. Water-based materials, which possess high dielectric constants and dielectric losses and exhibit rescattering resonance and strong frequency dispersion characteristics at microwave frequencies, are less commonly used. Research and applications of water-based metamaterials for sensor functionality have not yet received widespread attention.

[0004] The working principle of metamaterial sensors is to convert changes in the dielectric constant around the sensor into changes in the electromagnetic signal spectrum, specifically manifested as shifts in the position of the resonance peak, including significant changes in the resonant frequency and resonance depth. Refractive index sensing utilizes the constitutive relations of electromagnetic waves, namely the constitutive relations between electric field and electric displacement vector, magnetic field and magnetic vector, and current and electric field. After the introduction of a medium, the local electric and magnetic fields change, thus affecting the resonant frequencies and resonance depths of the transmission and reflection spectra. The working principle of all-dielectric sensing mainly involves Mie scattering theory. The main point of Mie scattering is that when the size of the dielectric sphere is much smaller than the wavelength of the incident electromagnetic wave, its equivalent dielectric constant and permeability can exhibit negative values ​​under certain conditions. This is related to the first-order electric and magnetic resonance coefficients of the dielectric sphere. For both the equivalent dielectric constant and equivalent permeability to be negative, electric and magnetic resonances must occur simultaneously within the dielectric sphere. By selecting dielectric spheres with high dielectric constants, when irradiated by incident electromagnetic waves, each sphere can be equivalent to a magnetic dipole and an electric dipole, resulting in both magnetic resonance and electric resonance modes. Biosensors using metamaterials for biological detection involve attaching biomolecules to the metamaterial structure, causing changes in the surrounding dielectric constant and thus altering the resonant frequency.

[0005] Furthermore, existing metamaterial sensors mostly convert environmental perception into frequency shifts in the position of resonance peaks. Research on utilizing amplitude shifts to achieve sensing functions is limited. Summary of the Invention

[0006] This invention provides a dual-function water-based metamaterial sensor and its application, which can realize dual sensing functions of amplitude and frequency.

[0007] The technical solution of the present invention is a dual-function water-based metamaterial sensor, which is formed by multiple unit structures arranged periodically along the x and y axes to form a metamaterial array; the unit structure includes a resin shell, which has a cavity inside for filling the water structure, and a metal plate is provided at the bottom of the resin shell.

[0008] Furthermore, the unit structure is cuboid in shape, and its longest side is smaller than the wavelength of the gigahertz wave used when measuring the dielectric constant of the test object.

[0009] Furthermore, the resin is a photosensitive resin with a relative permittivity of 3.2 to 3.7 and a loss tangent of 0.001 to 0.005.

[0010] Furthermore, the metal plate is a copper base plate, whose length and width match the bottom of the resin shell, and its thickness is 0.035 mm. The electrical conductivity of the copper base plate is 5.96 × 10⁻⁶. 7 S / m.

[0011] Furthermore, the shape and size of the cavity match the water structure, which consists of two cross-shaped water bodies connected at the bottom with a staggered bottom and a rectangular water body connecting the intersection of the two cross-shaped water bodies, with an included angle between the two cross-shaped water bodies.

[0012] Furthermore, the overall structure of the water body is located at the center inside the photosensitive resin shell, and the water body in the horizontal direction of the cross-shaped water body is tangent to the photosensitive resin shell; the two cross-shaped water bodies are set facing each other with an included angle of 60°; the included angle between the two cross-shaped water bodies and the horizontal plane is also 60°.

[0013] Furthermore, the outer shell is rectangular, and the cavity corresponding to each cross-shaped water body inside it is connected to the two sides formed by the long side and the wide side of the rectangular structure. The other sides of the outer shell are not connected to the cavity.

[0014] This invention also relates to the application of the aforementioned bifunctional water-based metamaterial sensor in biological detection.

[0015] Furthermore, during the specific testing, the object to be tested is placed on top of the casing, and gigahertz waves are incident from the side away from the metal plate in a direction perpendicular to the plane where the unit structure is placed.

[0016] The present invention has the following beneficial effects:

[0017] 1) The dual-function water-based metamaterial sensor of the present invention consists only of a photosensitive resin shell, a water structure, and a copper metal base plate. The water structure is a three-dimensional irregular structure, which enables absorption over a wider frequency band and achieves high-sensitivity amplitude and frequency dual sensing functions in the 36-41 GHz and 50-55 GHz frequency bands.

[0018] 2) This invention achieves dual sensing functionality for amplitude and frequency. When the object under test changes, not only is the amplitude shift significant, but the frequency shift is also very noticeable, enabling bidirectional detection. No auxiliary power is required, operation is simple, detection is easy, and requirements for the measurement environment are low. During measurement, the object under test is directly placed on top of the unit structure; after cleaning, the experiment can be repeated, greatly reducing costs.

[0019] 3) This invention achieves dual-peak resonance. When the sensor surface is covered with the analyte, the amplitude shift and frequency shift of the two resonance peaks are linearly related to the refractive index of the analyte.

[0020] 4) The dual-functional water-based metamaterial sensor described in this invention has high sensitivity. The refractive index sensitivity S is related to the amplitude change of the f1 resonance peak. dB1 =25.58 dB / RIU, refractive sensitivity S with frequency variation f1 = 5.04 GHz / RIU. The refractive index sensitivity S varies with amplitude at the resonant frequency f2. dB2 =27.85dB / RIU, refractive sensitivity S with frequency variation f2 = 4.09 GHz / RIU. Suitable for dielectric constant detection in biological applications.

[0021] 5) The materials used in the sensor are all conventional and easy to manufacture. Furthermore, water-based materials are significantly cheaper than other metals or composite materials. The sensor also has a simple structure, is manufactured using 3D printing technology, which is technically simple and easy to process, making it highly suitable for widespread application. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a dual-functional water-based metamaterial sensor.

[0023] Figure 2 The diagram shows the water structure breakdown within the sensor unit, including cross-shaped and rectangular water layers.

[0024] Figure 3 (a) is a three-dimensional model of the unit structure of the broadband water-based metamaterial; (b) is a schematic diagram of the dual-functional water-based metamaterial sensor unit array.

[0025] Figure 4This is a graph showing the relationship between the relative permittivity of the water material used in the sensor of Example 1 and the frequency.

[0026] Figure 5 The graph shows the simulation results of the resonant point of the sensor in Example 1 as a function of the dielectric constant of the analyte.

[0027] Figure 6 The figure shows the simulation results of the resonant point of the sensor in Example 1 as a function of the dielectric loss of the test object.

[0028] Figure 7 The image shows the amplitude change of the sensor's resonant point in Example 1 as the refractive index of the analyte changes from n=1 to n=1.8, and its linear fitting.

[0029] Figure 8 The image shows the frequency change of the sensor in Example 1 as the refractive index of the analyte changes from n=1 to n=1.8, and its linear fitting.

[0030] Figure 9 Example 2 is a simulation result curve of the sensor provided by the present invention detecting breast cancer cells;

[0031] Figure 10 This is a simulation result curve of the sensor provided by the present invention detecting glucose concentration in Example 3.

[0032] Figure 11 The figure shows a comparison of the simulation results of the resonant point as a function of the dielectric constant of the test object when the refractive index of the test object is n=1, after the internal filling material of the sensor in Example 4 was changed to seawater, and that in Example 1.

[0033] Figure 12 Example 5 is a simulation result curve of the sensor's resonant point changing with the dielectric loss of the test object after the photosensitive resin shell is thickened by 0.5 mm both above and below in the y-axis direction, based on Example 1.

[0034] Figure 13 (a) is Comparative Example 1, which is the simulation result curve of the sensor’s resonant point changing with the dielectric loss of the test object after changing the cross water body structure to a rectangular frame structure while keeping other conditions unchanged in Example 1; (b) is a schematic diagram of the rectangular frame structure.

[0035] Figure 14 For Comparative Example 2, that is, based on Example 1, with other conditions unchanged, only the included angle of the cross-shaped water body structure is changed to 45°, the simulation result curve of the sensor's resonant point as a function of the dielectric loss of the test object is shown.

[0036] Figure 15For Comparative Example 3, which is based on Example 1 with other conditions unchanged but with the rectangular water body structure removed, the simulation result curve shows the change of the resonant point of the sensor with the dielectric loss of the test object. Detailed Implementation

[0037] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0038] Example 1

[0039] like Figures 1-3 As shown, a dual-functional water-based metamaterial sensor is constructed by a metamaterial array consisting of multiple unit structures periodically arranged along the x and y axes. Figure 3 As shown in (b), the specific dimensions are 320mm × 200mm. Its unit structure includes a resin shell, which is 3D printed from photosensitive resin and has a rectangular shape. Figure 3 (a) The dimensions L0×W0×h0 are 8mm×5mm×5.6mm, with a relative permittivity of 3.5 and a loss tangent of 0.001. The resin shell has an internal cavity for filling the water structure, and a metal plate, preferably made of copper with a thickness of 0.03–0.04mm, is provided at the bottom of the resin shell to prevent gigahertz waves from passing through. In this embodiment, its dimensions are 8mm×5mm×0.035mm, and its conductivity is 5.96×10⁻⁶. 7 S / m. The bottom metal plate is placed parallel to the resin shell, stacked along the z-direction, and tightly connected.

[0040] The water structure consists of two cross-shaped water bodies and a rectangular water body connecting them, with an included angle between the two cross-shaped water bodies; in this embodiment, the included angle is 60°. A breakdown diagram of the water structure is shown below. Figure 2 As shown, there are cross-shaped and rectangular water layers, respectively. The cross-shaped water layer is composed of long... The rectangular water layer structure is obtained by rotating a cuboid with a width (W1) of 2 mm and a height (H2) of 2 mm around its center by 90°. The rectangular water layer structure has a length (L3) of 4 mm, a width (W3) of 2 mm, and a height (H3) of 1 mm. The two ends of the rectangular water layer are connected to the intersections of two cross-shaped water layers. The water in the structure can be tap water, purified water, or even seawater. This embodiment specifically selects the Water (Debye Model), whose relative permittivity is related to frequency and temperature and can be described using the Debye model.

[0041]

[0042] In the formula: ε0 and ε ∞ Let be the high-frequency dielectric constant and the static dielectric constant of water, respectively, and τ be the rotational relaxation time. Figure 4 The graph shows the relationship between the dielectric constant of water and frequency at room temperature (25°C), where the solid and dashed lines represent the real and imaginary parts of the dielectric constant, respectively. It can be observed that the relative dielectric constant of water gradually decreases with increasing frequency, ranging from 74 to 16 within the operating frequency range of this embodiment. The loss factor of water (the imaginary part of the dielectric constant) shows a trend of first increasing and then decreasing with frequency, indicating that water exhibits good dispersion characteristics across the entire frequency range.

[0043] The fabrication method of the bifunctional water-based metamaterial sensor employs 3D printing technology. 3D printing technology involves creating or acquiring a 3D model based on a computer-aided 3D design model, importing the model into slicing software for processing, setting printing parameters, and then using laser beams, hot-melt nozzles, or other methods to deposit and bond special materials such as thermoplastic polymers (e.g., ABS and PLA), metals, and ceramics layer by layer until a solid product is formed. Unlike traditional manufacturing methods that use molds, milling, and other mechanical processing to shape and cut raw materials to produce finished products, 3D printing significantly reduces manufacturing complexity. This digital manufacturing model greatly shortens the product development cycle, increases productivity, and reduces production costs.

[0044] Simulation was performed using the aforementioned sensors:

[0045] Simulation tests were conducted using CST simulation software. The results are as follows: Figure 5 and Figure 6 As shown, Figure 5 The change in refractive index *n* of the analyte, increasing it at intervals from *n*=1 to *n*=1.8, causes varying degrees of amplitude and frequency shifts in the two resonant peaks *f1* and *f2* at the resonant frequency. The amplitude of peak *f1* increases from -14.04 dB to -34.17 dB, and its frequency shifts from 40.78 GHz to 36.83 GHz. The amplitude of peak *f2* increases from -11.89 dB to -34.06 dB, and its frequency shifts from 53.74 GHz to 50.25 GHz. The significant and substantial shifts in both amplitude and frequency of these refractive peaks indicate that the changes can be more clearly observed during analyte testing, facilitating practical experimental detection.

[0046] The dielectric loss in the analyte can also lead to different responses in the sensor's reflectance spectrum. The dielectric loss coefficient (tanθ) is often considered a quantitative parameter to describe dielectric loss as a key indicator. Figure 6 As shown, the reflection performance of the reflection curve gradually weakens as tanθ increases from 0 to 0.4. This means that some energy is dissipated in the lossy medium. The amplitude also changes with the variation of tanθ, which helps distinguish analytes with different dielectric losses.

[0047] Furthermore, to further investigate the sensing characteristics of the proposed bifunctional water-based metamaterial sensor, the relationship between the amplitude and frequency changes of the two resonant peaks of the sensor in Example 1 and the refractive index was studied. For example... Figure 7 and Figure 8 As shown, a linear fit was performed on the relationship between the change in refractive index of the analyte and the changes in the amplitude and frequency shift of the resonant peak. The slope of the fitted curve is the corresponding refractive index frequency sensitivity. As the refractive index of the analyte increases from n=1 to n=1.8, the amplitude difference and frequency shift distance between adjacent refractive index peaks gradually increase. The refractive index sensitivity S at the resonant frequency f1 is... dB1 =25.58 dB / RIU, refractive sensitivity S with frequency variation f 1 = 5.04 GHz / RIU. The refractive index sensitivity S varies with amplitude at the resonant frequency f2. dB2 =27.85dB / RIU, refractive sensitivity S with frequency variation f2 = 4.09 GHz / RIU. Therefore, it can be seen that the described dual-function water-based metamaterial sensor can achieve highly sensitive sensing and detection of analytes coated on its unit array surface in terms of amplitude-modulated sensing and frequency-modulated sensing.

[0048] This invention also relates to the application of the proposed bifunctional water-based metamaterial sensor in biological detection.

[0049] Example 2

[0050] During testing, normal cells and breast cancer cells extracted from the breast tissue are coated onto the upper part of a resin shell, respectively. Electromagnetic waves (wavelength 8 mm) are then incident perpendicularly onto the sensor surface along the z-axis (the side of the resin shell away from the metal plate). Because normal cells and breast cancer cells from the human breast tissue have different refractive indices (1.387 and 1.401 respectively), in the simulation, normal cells and breast cancer cells can be set as test objects with the same height (1 mm) but different refractive indices. Through observation... Figure 9 It can be observed that, compared to healthy cells, both resonance peaks in breast cancer cells are shifted towards the positive y-axis, with an amplitude shift of approximately 0.3 dB. This can be used to screen for breast cancer cells and normal cells.

[0051] Example 3:

[0052] The glucose solution concentrations and corresponding refractive indices used in the examples are shown in Table 1 below:

[0053] Table 1 Relationship between glucose solution concentration and refractive index

[0054]

[0055] Different concentrations of glucose solution were quantitatively drop-coated onto the sensor surface. Then, the surrounding medium was altered based on the different refractive indices of the glucose solutions at different concentrations. In the simulation, glucose solutions of varying concentrations were presented as a layer of the same height (1 mm) containing different refractive indices of the target material. The simulation yielded the following results: Figure 10 The reflection curves shown indicate that the frequencies of the two resonant peaks of the reflection coefficient redshift with increasing glucose concentration, and the amplitudes also shift downwards with increasing glucose concentration. According to sensing principles, the frequency and amplitude shifts in the simulated data change linearly with the refractive index. Therefore, with more supporting data on glucose concentration and refractive index, the concentration of the glucose solution can be detected through the correlation between concentration and refractive index.

[0056] Example 4: The sensor structural parameters remain consistent with those in the previous example, except that the internal water filling material is changed to seawater for simulation verification. Figure 11 As shown in the comparison, it can be seen that the simulation results of the seawater sensor fluctuate greatly and have many jumps, making it difficult to detect the results in actual testing. Therefore, the water material Water (Debyemodel) provided in Example 1 is the optimal choice.

[0057] Example 5: Based on Example 1, with other conditions remaining unchanged, only the thickness of the photosensitive resin shell was varied to observe the sensor's sensing effect. We chose to change only the thickness of the photosensitive resin shell along the y-axis, specifically increasing the thickness by 0.5 mm at both the top and bottom. Then, the test object was coated onto the upper part of the resin shell along the y-axis, changing the refractive index of the test object at equal intervals of 0.2 within the range of n = 1.0 to n = 1.8. The simulation results of the sensor under this condition are as follows: Figure 12 As shown in the figure, the resonance peak exhibits a certain degree of amplitude and frequency shift. Comparing this with the simulation results of the resonance point of the sensor in Example 1 as a function of the dielectric constant of the analyte, it can be seen that although the sensor under this condition can achieve a certain level of sensing, it is not as effective as the sensor in Example 1. Furthermore, the figure shows that, except for the 58GHz resonance point, the peak value changes are relatively small at other resonance points. This indicates that under this condition, only single-point sensing can be achieved, and the sensing effect is far inferior to that of the sensor proposed in Example 1.

[0058] Comparative Example 1: Based on Example 1, the only difference is that the cross-shaped water structure is replaced with a rectangular ring water structure. The specific parameters are: the outer ring (L4×W4×H4) is 5mm×4mm×2mm, and the inner ring (L5×W3×H4) is 3mm×2mm×2mm. The simulation results are as follows... Figure 13As shown, the sensor exhibits almost no significant reflection after being replaced with a rectangular ring structure, with all reflection curves above 0.9. Therefore, this structure is not suitable, demonstrating the irreplaceable nature of the proposed cross-shaped structure.

[0059] Comparative Example 2: Based on Example 1, the only difference was that the included angle of the cross-shaped water body was changed from 60° to 45°. Under these conditions, the analyte was coated onto the sensor, with the refractive index varying at equal intervals of 0.2 within the range of n = 1.0 to n = 1.8, as shown below. Figure 14 The simulation results are shown below. Compare them with the simulation results of Example 1. Figure 4 A comparison reveals that the difference is primarily observed between refractive indices n = 1.6 and n = 1.8. When the angle between the cross-shaped water bodies is 45°, the reflection curve at a refractive index of 1.8 is higher than that at 1.6, indicating a non-linear change in the sensor's refractive index amplitude. Therefore, in practical applications, confusion can easily arise between refractive indices of 1.4 and 1.8, leading to inaccurate detection. Thus, a 60° angle for the cross-shaped water body structure is the optimal choice.

[0060] Comparative Example 3: Based on Example 1, the only difference is the removal of the rectangular water body from the water structure. The analyte was coated onto a sensor under these conditions, and the refractive index of the analyte was varied at equal intervals of 0.2 within the range of n = 1.0 to n = 1.8, resulting in the simulated curve shown below. Figure 15 As shown in the figure, the simulated refractive peak value near 50.0 GHz rebounds at a refractive index n = 1.8, exceeding the peak value at n = 1.4. Therefore, the refractive peak value is not linear within the range of n = 1.0 to n = 1.8. Consequently, errors and inaccurate detection may occur in the range of n = 1.2 to n = 1.8 in actual testing. Furthermore, compared with the simulation in Example 1... Figure 5 In comparison, removing the rectangular block not only resulted in the loss of dual-frequency detection, but also made the curve changes less pronounced and clearer than in Example 1 after altering the refractive index of the analyte. Therefore, it can be seen that rectangular water bodies are indispensable in water structure.

[0061] The above embodiments are only for illustrating the technical concept and features of the present invention, and the content described is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Within the technical scope disclosed in the present invention, equivalent changes or improvements made to the technical solution and inventive concept of the present invention should all be covered within the scope of protection of the present invention.

Claims

1. A dual-functional water-based metamaterial sensor, characterized in that, The sensor consists of a metamaterial array formed by multiple unit structures arranged periodically along the x and y axes. Each unit structure includes a resin shell with a cavity inside for filling a water structure. A metal plate is located at the bottom of the resin shell. The cavity matches the shape and size of the water structure, which consists of two cross-shaped water bodies connected at their bottoms with a staggered bottom and a rectangular water body connecting the intersection of the two cross-shaped water bodies. There is an angle between the two cross-shaped water bodies. The two cross-shaped water bodies are arranged facing each other with an angle of 60°. The angle between the two cross-shaped water bodies and the horizontal plane is also 60°. The resin is a photosensitive resin with a relative permittivity of 3.2~3.7 and a loss tangent of 0.001~0.

005.

2. The dual-functional water-based metamaterial sensor according to claim 1, characterized in that: The unit structure is cuboid in shape, and its longest side is smaller than the wavelength of the gigahertz wave used to measure the dielectric constant of the test object.

3. The dual-functional water-based metamaterial sensor according to claim 1, characterized in that: The metal plate is a copper base plate, whose length and width match the bottom of the resin shell, and whose thickness is 0.03~0.04mm.

4. The dual-functional water-based metamaterial sensor according to claim 3, characterized in that: The overall structure of the water body is located at the center inside the photosensitive resin shell, and the horizontal axis of the cross-shaped water body is tangent to the photosensitive resin shell.

5. The dual-functional water-based metamaterial sensor according to claim 4, characterized in that: The outer shell is rectangular, and the cavity corresponding to each cross-shaped water body inside it is connected to the two sides formed by the length and height of the rectangular structure. The other sides of the outer shell are not connected to the cavity.

6. The application of the bifunctional water-based metamaterial sensor according to any one of claims 1 to 5 in biological detection.

7. The application according to claim 6, characterized in that: During the actual test, the object to be tested is placed on top of the casing, and gigahertz waves are incident from the side away from the metal plate in a direction perpendicular to the plane where the unit structure is placed.

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