A plasmon-like sensor and applications thereof

Abstract

This invention provides a surface plasmon resonance sensor and its applications, relating to the field of microwave sensor technology. The surface plasmon resonance sensor of this invention includes a dielectric substrate, a metallic waveguide, and a subwavelength resonator, wherein the subwavelength resonator has a fan-shaped defect structure. By introducing an asymmetric loss structure through the design of the subwavelength resonator with the fan-shaped defect structure, the surface plasmon resonance sensor of this invention achieves a singularity state, exhibiting a square-root-dependent high sensitivity response to external perturbations. This significantly improves detection sensitivity and enables high sensitivity and low detection limits for substances such as deionized water, glycerol solution, and glucose solution, as well as dynamic detection of the hydrolysis process of thioacetylcholine. It has advantages such as simple structure, easy integration, and high sensitivity.

Description

Technical Field

[0001] This invention relates to the field of microwave sensor technology, and in particular to a surface plasmon sensor and its applications. Background Technology

[0002] The sensing of weak physical signals and the detection of low-concentration liquid substances are core technological requirements in fields such as environmental monitoring, bioanalysis, chemical testing, and medical diagnostics. In practical detection scenarios, the targets to be measured often exist in trace amounts and low concentrations, which places stringent demands on the sensor's response capability, detection accuracy, and limit detection performance.

[0003] Currently, most mainstream sensing devices are based on classical Hermitian physics systems. These traditional sensors typically operate at the Dirac point, and their response to external perturbations follows a linear pattern. This linear response characteristic is suitable for routine detection scenarios involving large perturbations and high-concentration samples, meeting basic detection requirements under normal operating conditions. However, in low-scale precision detection scenarios such as capturing trace signals and detecting low-concentration solutions, the technical shortcomings of Hermitian sensors become increasingly prominent: the linear response mechanism of the system has limited amplification capability for weak external perturbations, easily leading to insufficient sensitivity, weak signal response, and high detection limits. It is difficult to accurately identify minute parameter changes caused by trace amounts of analyte, resulting in missed detections of target signals and large errors in detection results. This significantly limits the application scope and detection efficiency of traditional sensors in high-precision, low-content precision detection fields. Summary of the Invention

[0004] This invention addresses the shortcomings of existing microwave sensors, such as insufficient detection limit and low sensitivity when detecting weak signals or low-concentration solutions. It provides a quasi-surface plasmonic sensor by introducing an asymmetric loss structure to construct a quasi-local surface plasmonic resonant sensor, enabling the sensor to reach a singular point state, which can effectively improve detection sensitivity and significantly reduce the detection limit.

[0005] Another objective of this invention is to provide an application of a surface plasmon sensor in the detection of trace liquids.

[0006] In a first aspect, the present invention protects a surface plasmonic sensor comprising a dielectric substrate, a metallic waveguide, and a subwavelength resonator having a fan-shaped defect structure.

[0007] According to the surface-like plasma sensor protected by the present invention, preferably, the inner arc length of the fan-shaped defect structure is 0.6mm~0.8mm, the outer arc length is 0.7mm~0.8mm, the side length is 0.2mm~0.4mm, and it is arranged at a counterclockwise angle of 27~33° relative to the positive x-axis direction, preferably at a counterclockwise angle of 23°.

[0008] According to the surface plasmon sensor protected by the present invention, preferably, the subwavelength resonator includes a central metal disk and circumferentially distributed outer metal strips, wherein the ratio of the radius of the central metal disk to the length of the outer metal strips is 1:1.5~5.

[0009] According to the surface-like plasma sensor protected by the present invention, preferably, the radius of the central metal disk is 0.8mm to 2mm, the length of the outer metal strip is 1mm to 4mm and the width is 0.1mm to 0.5mm, and the circumferential spacing angle between adjacent resonant units is 3 to 10°. The preferred central metal disk has a radius of 1 mm, the outer metal strip has a length of 3 mm and a width of 0.1 mm, the circumferential spacing angle α between adjacent resonant units is 3°, and the period θ is 6°.

[0010] According to the surface plasmon sensor protected by the present invention, preferably, the metal waveguide is composed of a rectangular microstrip line, a horn-shaped microstrip line, and periodically arranged metal pillars. The rectangular microstrip line has a thickness of 0.035 mm, a length of 5-9 mm, and a width of 1-2 mm. The periodically arranged metal pillars have a thickness of 0.035 mm, a length of 1-2 mm, a width of 0.4-0.5 mm, a period of 0.4-0.8 mm, and a number of periods of 20-30. Preferably, the rectangular microstrip line has a thickness of 0.035 mm, a length of 7 mm, and a width of 1.6 mm, and the periodically arranged metal pillars have a thickness of 0.035 mm, a length of 1.5 mm, a width of 0.45 mm, a period of 0.6 mm, and a period number of 27.

[0011] According to the surface-like plasma sensor protected by the present invention, preferably, the length, width and thickness of the dielectric substrate are 51~53mm, 20~40mm and 0.5~1mm, respectively.

[0012] According to the surface-like plasma sensor protected by the present invention, preferably, the metal waveguide and the subwavelength resonator are coplanarly fabricated on the front side of the dielectric substrate, and the spacing between the metal waveguide and the subwavelength resonator is 0.1~0.3mm, preferably 0.25mm.

[0013] According to the surface plasmon sensor protected by the present invention, preferably, a metal layer is provided on the back side of the dielectric substrate, and no metal layer is provided at the position opposite the resonator.

[0014] Secondly, the present invention also specifically protects the application of a surface plasmon sensor in the detection of trace liquids.

[0015] According to the application protected by the present invention, preferably, the trace liquid is selected from any one or more of water, sugars, alcohols, and trace enzymatic reaction solutions.

[0016] Beneficial effects: This invention provides a surface plasmon resonance sensor that introduces an asymmetric loss structure through a subwavelength resonator with a fan-shaped defect structure. This results in mirror asymmetry of the resonator, breaking the degeneracy of clockwise and counterclockwise waves in the resonator. Consequently, the surface plasmon resonance sensor reaches a singularity state, exhibiting a square root-dependent high sensitivity response to external perturbations. This significantly improves detection sensitivity and enables high sensitivity and low detection limits for substances such as deionized water, glycerol solution, and glucose solution, as well as dynamic detection of the hydrolysis process of thioacetylcholine. It has advantages such as simple structure, easy integration, and high sensitivity. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram and a partial enlarged view of the surface-like plasma sensor of the present invention.

[0019] Figure 2 This is the transmission resonance valley diagram obtained through simulation in this invention.

[0020] Figure 3 The images show the transmission diagrams of two types of resonators obtained through simulation of the sensor of the present invention in response to environmental disturbances. (a) is the transmission diagram of the surface plasmon sensor of the present invention, and (b) is the transmission diagram of the Dirac point sensor.

[0021] Figure 4 This is a comparison chart of the sensing performance of the surface plasmon sensor and the Dirac point sensor of the present invention.

[0022] Figure 5 This invention relates to a sensor performance testing system.

[0023] Figure 6 This is a comparison chart of sensor simulation and actual measurement according to the present invention.

[0024] Figure 7 The figure shows the sensor stability test results of this invention.

[0025] Figure 8 The following is a graph showing the results of quantitative testing of deionized water using the sensor of the present invention: (a) shows the splitting of the resonance valley at different doses, and (b) shows the fitting result of the splitting amount on the dose.

[0026] Figure 9 The graph shows the results of glucose molecular weight testing by the sensor of the present invention. (a) shows the splitting of the resonance valley at different doses, and (b) shows the fitting result of the splitting amount on the dose.

[0027] Figure 10 The following graph shows the results of the sensor test for glycerol concentration in this invention: (a) shows the splitting of the resonance valley at different concentrations, and (b) shows the fitting result of the splitting amount on the dose.

[0028] Figure 11 This is a flowchart of the response sensing experiment for the hydrolysis process of thioacetylcholine.

[0029] Figure 12 The figure shows the results of the response sensing experiment of the hydrolysis process of thioacetylcholine. (a) shows the splitting of the resonance valley at different test times, and (b) shows the nonlinear fitting results of the splitting amount on the test time. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] In a specific embodiment, the present invention provides a surface plasmonic sensor, comprising a dielectric substrate, a metal waveguide, and a subwavelength resonator, wherein the subwavelength resonator has a fan-shaped defect structure.

[0032] It should be noted that: The subwavelength resonator of the surface plasmon resonance sensor provided by this invention has a fan-shaped defect structure, which breaks the mirror symmetry of the sensor system, introduces asymmetric electromagnetic loss, and forms a non-Hermitian system. This causes the two sets of eigenmodes that were originally degenerate at the Dirac point to split their eigenvalues. At this time, the two eigenstates change from degenerate to mutually coupled, and the transmission spectrum changes from a single resonance peak (valley) to two transmission resonance peaks (valleys). According to the Hamiltonian and coupled-mode theory of non-Hermitian systems, by adjusting the coupling coefficient and loss distribution between the two modes (a pair of orthogonal eigenmodes inherent in the subwavelength resonator at the operating frequency), the system operates at a singular point, making the eigenvalues ​​and eigenvectors of the two modes simultaneously degenerate. In this state, the system has a square root response to external perturbations, and the sensing enhancement effect can be achieved even with small perturbations.

[0033] Surface plasmons refer to electromagnetic density waves generated by the interaction of free electrons in a metal with electromagnetic waves under the influence of electromagnetic waves. They possess the ability to achieve localized electromagnetic enhancement at the subwavelength scale. In the microwave band, structural dispersion can be used to make the dielectric constant of a metal negative, thus achieving surface plasmons, or quasi-surface plasmons, at low frequencies. These also achieve localized electromagnetic enhancement at the subwavelength scale. Combining quasi-surface plasmon structures with sensors, utilizing their resonance to generate localized electromagnetic field enhancement under electromagnetic wave excitation, allows for exceptional sensitivity to the surrounding environment, enabling highly sensitive analysis. This approach offers advantages such as low cost, low power consumption, real-time processing, and ease of integration.

[0034] The surface plasmon sensor described in this invention is mainly based on two types of metal structures: metal waveguides and subwavelength resonators. The metal waveguides are used to transmit electromagnetic waves of surface plasmons, and the subwavelength resonators excite local surface plasmon resonance and form electromagnetic field enhancement. The dielectric substrate serves as the supporting matrix, providing stable support and a low-loss dielectric environment for the metal structure, thereby indirectly regulating the plasma transmission and resonance characteristics.

[0035] The surface-like plasma sensor of the present invention has the advantages of simple structure, easy integration, and high sensitivity.

[0036] In some specific embodiments, the inner arc length of the fan-shaped defect structure mentioned in this invention is 0.6mm~0.8mm, the outer arc length is 0.7mm~0.8mm, the side length is 0.2mm~0.4mm, and it is set at a counterclockwise angle of 27~33° relative to the positive x-axis direction.

[0037] The purpose of designing a sector-shaped defect is to introduce asymmetric defects into the resonator to achieve the design of a non-Hermitian system. By adjusting the geometry and angle of the sector-shaped defect structure, singularities can be induced more effectively.

[0038] In some specific embodiments, the inner arc length of the fan-shaped defect structure mentioned in this invention can be, for example, a point value of 0.60mm, 0.66mm, 0.72mm, or any other arbitrary range, preferably 0.66mm. The outer arc length can be, for example, a point value of 0.7mm, 0.75mm, 0.8mm, or any other arbitrary range, preferably 0.75mm. The side length can be, for example, a point value of 0.2mm, 0.28mm, 0.36mm, or any other arbitrary range, preferably 0.28mm. It is set at a counterclockwise angle relative to the positive x-axis, specifically at angles such as 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, or any other arbitrary range, preferably a 23° counterclockwise angle.

[0039] The subwavelength resonator comprises a central metal disk and circumferentially distributed outer metal strips. The resonant frequency of the surface plasmon resonance resonator is mainly adjusted by the combined length of the outer metal strips (i.e., the outer radius) and the radius of the inner metal disk (i.e., the inner radius). By changing the inner and outer radii during the resonator design process, the resonant frequency can be adjusted, resulting in concentrated field strength and high basic sensitivity. In a specific embodiment, the ratio of the radius of the central metal disk to the length of the outer metal strips in the subwavelength resonator mentioned in this invention is 1:1.5 to 5, for example, it can be a point value such as 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or any arbitrarily constructed range of values.

[0040] In some specific exemplary embodiments, the radius of the central metal disk mentioned in this invention is 0.8mm to 2mm, the length of the outer metal strip is 1mm to 4mm, the width is 0.1mm to 0.5mm, and the circumferential spacing angle between adjacent resonant units is 3 to 10°.

[0041] For example, the radius of the central metal disk can be 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2mm, etc.; the length of the outer metal strip can be 1mm, 2mm, 3mm, 4mm, etc., and the width can be 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, etc.; the circumferential spacing angle between adjacent resonant units can be, for example, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, etc.

[0042] In some preferred embodiments, the central metal disk of the subwavelength resonator mentioned in this invention has a radius of 1 mm, the outer metal strip has a length of 3 mm and a width of 0.1 mm, the circumferential spacing angle α between adjacent resonant units is 3°, and the period θ is 6°.

[0043] More specifically, the subwavelength resonator is shaped like a corrugated metal disk. In the center of the resonator is a metal disk with a radius of 1 mm and a thickness of 0.035 mm. Sixty metal strips with a length of 2 mm, a width of 0.1 mm, and a thickness of 0.035 mm are evenly distributed on the circumference of the metal cylinder in a radial pattern.

[0044] The surface plasmon-like metallic waveguide is composed of three parts coupled sequentially: a rectangular microstrip line, a horn-shaped microstrip line, and periodically arranged metal pillars. Adjusting the geometric dimensions of each component of the waveguide can directly control the equivalent electromagnetic parameters of the structure, causing a significant shift in the waveguide's operating transmission frequency band, bandwidth characteristics, and transmission loss.

[0045] The localized surface plasmon resonator used in this invention operates stably at a resonant frequency of 27 GHz. To ensure resonant excitation efficiency and detection stability, the matched metal waveguide must have high bandwidth and low loss transmission performance at this target frequency. The rectangular microstrip line mentioned in this invention has a thickness of 0.035 mm, a length of 5-9 mm, and a width of 1-2 mm. The periodically arranged metal pillars have a thickness of 0.035 mm, a length of 1-2 mm, a width of 0.4-0.5 mm, a period of 0.4-0.8 mm, and a period number of 20-30.

[0046] In some specific exemplary embodiments, the thickness of the rectangular microstrip line is 0.035 mm, the length can be, for example, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, etc., and the width is 1~2 mm. The thickness of the periodically arranged metal pillars is 0.035 mm, the length is 1~2 mm, the width is 0.4~0.5 mm, the period can be, for example, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, etc., and the number of periods can be, for example, 20, 22, 23, 25, 27, 30, etc.

[0047] In some preferred exemplary embodiments, the rectangular microstrip line has a thickness of 0.035 mm, a length of 7 mm, and a width of 1.6 mm, and the periodically arranged metal pillars have a thickness of 0.035 mm, a length of 1.5 mm, a width of 0.45 mm, a period of 0.6 mm, and a period number of 27.

[0048] More specifically, the metallic waveguide consists of three parts: rectangular microstrip lines, horn-shaped microstrip lines, and periodically arranged metal pillars. The total length of the metallic waveguide is 52.35 mm. There are two rectangular microstrip lines, each 7 mm long, and two horn-shaped microstrip lines, each 5.15 mm long. Each metal pillar is 0.45 mm wide and has a period of 0.6 mm, for a total of 27 periods. The width of each of the two rectangular microstrip lines is 1.6 mm, and the length of each of the 27 metal pillars is 1.5 mm. The thickness of each of the rectangular microstrip lines, horn-shaped microstrip lines, and periodically arranged metal pillars is 0.035 mm.

[0049] Based on the high-frequency operating requirements of 27GHz, the dimensions of each component of the waveguide were optimized and limited. By optimizing the structural parameters of rectangular microstrip lines, horn-shaped microstrip lines, and periodic metal pillars, a smooth impedance transition, efficient electromagnetic field confinement, and low-loss conduction were achieved, ensuring stable broadband transmission of electromagnetic waves in the 27GHz band and realizing low-loss broadband transmission in the 20~30GHz range. This reduced signal reflection and radiation loss, providing a reliable microwave transmission foundation for precise solution sensing and detection.

[0050] In some specific embodiments, the present invention further defines the length, width and thickness of the mentioned dielectric substrate as 51~53mm, 20~40mm and 0.5~1mm, respectively.

[0051] Limiting the substrate size can stabilize electromagnetic boundary conditions, prevent resonant frequency shift and intrinsic impedance mismatch, regulate transmission spectrum response characteristics, reduce electromagnetic interference at the substrate edge, ensure stable operating frequency band and consistent coupling characteristics of the device, and effectively improve sensor detection accuracy.

[0052] The substrate mentioned in this invention is a rigid substrate. For example, it can be selected from materials such as FR-4 and F4BM217 that are corrosion-resistant and electromagnetically stable, with a length of 51-53mm, a width of 20-40mm, and a thickness of 0.5-1mm.

[0053] In some specific exemplary embodiments, the dielectric substrate mentioned in this invention can be an F4BM217 board with a length, width and thickness of 52.35 mm, 30 mm and 0.6 mm respectively (with a dielectric constant of 2.55 at 20-30 GHz).

[0054] In some specific embodiments, the metal waveguide and subwavelength resonator mentioned in this invention are coplanarly fabricated on the front side of the dielectric substrate, and the spacing between the metal waveguide and the subwavelength resonator is 0.1~0.3mm, preferably 0.25mm.

[0055] In some specific embodiments, the back side of the dielectric substrate mentioned in this invention is provided with a metal layer, while there is no metal layer at the position opposite the resonator.

[0056] Based on the transmission characteristics of surface-like plasmas (SLPs), if a metal layer is completely retained on the back side beneath the resonator, the underlying metal will strongly confine and shield the electromagnetic field, trapping most of the SLP electromagnetic waves within the dielectric substrate. This results in weak outward diffusion of the near-field electric field and limited interaction with the external test environment. This invention preferably employs a metal-free design at the corresponding position of the resonator. This optimized design appropriately removes the electromagnetic shielding constraint of the underlying metal, weakening the confinement effect on the local electromagnetic field of the resonator. This allows the near-field electric field of the SLP to better diffuse and extend outward from the substrate, increasing the interaction range and coupling degree between the electromagnetic field and the test liquid and the external dielectric environment. This significantly improves the sensing response sensitivity to changes in the dielectric constant of the external environment, solution concentration, and trace samples, enhancing the ability to identify weak dielectric perturbations. Simultaneously, the remaining area of ​​the substrate retains the back metal layer, maintaining stable impedance characteristics and low-loss transmission performance of the metal waveguide section. Without affecting the overall transmission performance, this further optimizes the sensor's sensing adaptability and detection performance to the external test system.

[0057] The metal layer on the back of the substrate is preferably a metal with the same length and width as the dielectric substrate.

[0058] In some specific exemplary embodiments, the copper layer thickness mentioned in this invention is 0.035 mm.

[0059] In some more specific exemplary embodiments, the copper layer attached to the back of the substrate has a length of 51-53 mm, a width of 20-40 mm, and a thickness of 0.035 mm; more preferably, the copper layer attached to the back of the substrate has a length of 52.35 mm, a width of 30 mm, and a thickness of 0.035 mm.

[0060] The waveguide impedance of this invention is preferably designed to be around 50 ohms to achieve low-loss transmission; therefore, the thickness of the copper layer on the back is preferred. Simultaneously, the bottom copper layer also provides electromagnetic shielding, preventing external noise interference and energy leakage.

[0061] The metal material of the metal layer mentioned in this invention is selected from gold, silver, copper or aluminum, with copper being preferred.

[0062] In a specific embodiment, the metal material mentioned in this invention is attached to the dielectric substrate by a lamination process, and then the structure is etched out by a subtractive etching method. That is, the relative positions of the resonators are not covered. In the etching process, the metal surface is treated with an organic solderable protective layer process, which has the advantages of strong stability and reusability.

[0063] The microwave band surface-like plasma sensor based on singularity enhancement provided by this invention breaks the system symmetry by introducing an asymmetric loss structure and adjusting the coupling between the resonator and the waveguide to achieve simultaneous degeneracy of eigenvalues ​​and eigenstates, i.e., singularity state. In this state, the sensor has a square root-dependent high sensitivity response to external perturbations and can be widely used in the detection of trace liquids.

[0064] The surface plasmon sensor of the present invention can generate a 202MHz resonance valley split for a metal analyte with a diameter of 0.2mm, and has excellent sensing performance under small-scale perturbation conditions.

[0065] The surface plasmon resonance sensor provided by this invention has the advantages of high sensitivity and low detection limit, enabling high-sensitivity, low-detection-limit detection of substances such as deionized water, glycerol solution, and glucose solution, as well as dynamic detection of the hydrolysis process of thioacetylcholine. For example, it can be applied to the detection of deionized water, glucose solution, and glycerol solution, among others. Results show that it can achieve trace detection of at least 4.4 μmol of deionized water, and the linear fitting result is... y =0.048× x +0.215, correlation coefficient R 2=0.99; it can achieve trace detection of 0.13 μmol in glucose solution, and the linear fitting result is... y =0.209× x +0.971, correlation coefficient R 2 =0.967; It can achieve detection of glycerol solutions with concentrations as low as 2%, and the linear fitting result is... y =-0.057× x +1.358, correlation coefficient R 2 =0.960.

[0066] The surface plasmon sensor provided by this invention can also be applied to realize the hydrolysis kinetics sensing of thioacetylcholine. The results show that the hydrolysis kinetics sensing of 250 μL thioacetylcholine solution (100 mg / mL) under the catalysis of 400 μL acetylcholine hydrolase solution (100 μg / mL) can be realized.

[0067] Example 1 A type of surface plasmon sensor (such as) Figure 1 As shown, it includes a dielectric substrate, a metal waveguide attached to the upper surface of the substrate and a subwavelength resonator with a fan-shaped defect, and a metal copper layer attached to the back of the substrate.

[0068] Where x and y represent the width and length of the substrate, t1 represents the thickness of the substrate, R1 and R2 represent the inner and outer radii of the resonator, and k, g, h, and t2 represent the side length, outer chord length, inner chord length, and thickness of the fan-shaped defect, respectively. θ and α represent the period and gap of the external metal strip of the resonator, respectively. c, d, h, and p represent the tooth width, period, depth, and width of the waveguide, respectively.

[0069] The total length of the metallic waveguide is 52.35 mm. There are two rectangular microstrip lines, each 7 mm long, and two horn-shaped microstrip lines, each 5.15 mm long. The width (c) of each metal pillar is 0.45 mm, the period (d) is 0.6 mm, and there are a total of 27 periods. The width of the two rectangular microstrip lines is 1.6 mm, the length (h) of the 27 metal pillars is 1.5 mm, the thickness of all three is 0.035 mm, and the depth (p) is 0.5 mm.

[0070] The subwavelength resonator is shaped like a corrugated metal disk. At its center is a metal cylinder with a radius R2 of 1 mm and a thickness of 0.035 mm. Sixty metal rectangles, each with a length (R1) of 3 mm, a width of 0.1 mm, and a thickness of 0.035 mm, are evenly distributed radially around the circumference of this cylinder. The circumferential spacing angle α between adjacent resonant units is 3°, and the period θ is 6°. The fan-shaped defect has a side length k of 0.28 mm, an outer chord length g of 1075 mm, an inner chord length h of 0.66 mm, and a thickness t2 of 0.035 mm.

[0071] The copper layer attached to the back of the substrate is 52.35 mm long, 30 mm wide, and 0.035 mm thick.

[0072] The dielectric substrate is made of F4BM217 material with a dielectric constant of 2.55 at 20-30GHz, a thickness t1 of 0.6mm, a length y of 52.35mm, and a width x of 30mm.

[0073] Example 2 Performance Analysis of Surface Plasma Sensors This embodiment evaluates the performance of a microwave-like surface plasmonic singularity sensor by the degree of resonance valley splitting, sensitivity, and sensing enhancement compared to a Dirac point sensor.

[0074] The difference between the Dirac sensor and the surface-like plasma sensor of Example 1 is that there is no sector defect in the resonant cavity, while the other parameters, structure and materials are the same.

[0075] The degree of resonant valley splitting is defined as: Δω=ω1-ω2, and the degree of sensing enhancement compared to the Dirac point sensor is defined as: Q=ΔωEP / ΔωDP.

[0076] Modeling and simulation analysis were performed, with radiation boundary conditions set. The z-direction was the electric field direction, the y-direction was the magnetic field direction, and the electromagnetic wave was incident along the x-direction. In the simulation, under the excitation of the electromagnetic wave, the surface-like plasmonic sensor of Example 1 will exhibit a plasma vortex resonance valley with a topological charge of 3 and a resonant frequency of 26.94 GHz. Figure 2 As shown. The sensing performance of the designed microwave-type surface plasmon resonance sensor was analyzed. The analyte was a copper metal disc, with the radius increasing sequentially from 0.18 mm to 0.28 mm in increments of 0.02 mm. Simulations were performed, as follows. Figure 3 As shown, the obtained transmission spectrum is as follows Figure 3 As shown in (a) and (b), with the increase of the radius of the analyte, a significant increase in frequency splitting occurs at the frequency where the resonance valley is located.

[0077] Based on the sensing enhancement formula, the sensing enhancement contrast of the surface plasmon sensor (singularity sensor) in Example 1 compared to the Dirac point sensor was obtained. The sensing contrast gradually increases as the size of the metal analyte decreases, such as... Figure 4 As shown.

[0078] Example 3 Application of a surface plasmon sensor in the detection of trace liquids.

[0079] This embodiment describes the detection of liquid volume or concentration using the surface plasmon sensor (singularity sensor) of Example 1: the liquid to be detected includes, but is not limited to, deionized water, glucose solution, glycerol solution, etc.

[0080] The specific steps are as follows: Preparation of three solutions: Preparation of deionized water using ion exchange: Pre-treatment of raw water removes suspended particles; Sulfonic acid-based cation exchange resins are used to remove impurity cations (Ca) from water. 2+ Mg 2+ Na + ); Using quaternary ammonium anion exchange resin to remove impurities (Cl-) from water - SO4 2- The deionized water prepared had a conductivity of 1~10 μS / cm.

[0081] Preparation of glucose solution: Dissolve 1 mg of glucose solid powder in 10 mL of deionized water to prepare a 0.1 mg / mL glucose solution.

[0082] Preparation of glycerol solution: Take 0.02 μL, 0.04 μL, 0.06 μL, 0.08 μL, and 0.1 μL of 100% pure glycerol, and dissolve and mix them thoroughly with 0.98 μL, 0.96 μL, 0.94 μL, 0.92 μL, and 0.9 μL of deionized water, respectively, to prepare 1 μL of glycerol solutions with volume concentrations of 2%, 4%, 6%, 8%, and 10%.

[0083] Testing process: A sensor testing system was built using a vector network analyzer, 10MHz-50GHz coaxial cables, a constant current pump, a 2μL micro-sampler, and two commercial microwave adapters. Figure 5 As shown.

[0084] The sensor's transmittance coefficient S21 under no-load conditions was tested using the sensor testing system described above as a control group. The results are as follows: Figure 6As shown.

[0085] The stability of the sensor was tested using the sensor system built above.

[0086] Add 0.4 μL of 100% pure glycerol to the sensitive area of ​​the sensor, and record the results after the test results of the vector network analyzer have stabilized.

[0087] The sensor was rinsed with deionized water to remove pure glycerin. After the sensor was completely dry, the transmittance of the sensor was tested.

[0088] Repeat the above test five times, and the results are as follows: Figure 7 As shown in (a) and (b).

[0089] Deionized water sensing test: Using a constant flow pump and micro-syringe, 4.4 μmol, 6.6 μmol, 8.8 μmol, 11.1 μmol, 15.5 μmol, 17.7 μmol, 20.0 μmol, and 22.2 μmol of deionized water were drawn and added dropwise to the sensing area of ​​the sensor. After each test, the sensor was cleaned before the next test was performed. The test results are as follows: Figure 8 As shown in (a) and (b) Glucose solution sensing test: Using a constant flow pump and micro-syringe, glucose solutions containing 0.13 μmol, 0.18 μmol, 0.22 μmol, and 0.27 μmol of glucose were respectively added to the sensor's sensitive area. After each test, the sensor was cleaned before proceeding to the next test. The test results are as follows: Figure 9 As shown in (a) and (b).

[0090] Glycerol solution sensing test: Glycerol solutions containing 2%, 4%, 6%, 8%, and 10% glycerol were drawn using a constant flow pump and a micro-syringe and added dropwise to the sensor's sensitive area. The sensor was cleaned after each test before proceeding to the next. Test results are as follows: Figure 10 As shown in (a) and (b). All the above tests were conducted at room temperature, with a vector network analyzer frequency range of 25-30 GHz.

[0091] Test Result Analysis: The microwave-based plasma singularity sensor resonates at 27.1 GHz, which deviates by 0.59% from the simulation result of 26.94 GHz. This is because the sensor is connected to the vector network analyzer, which serves as the signal source, via a coaxial cable and a microwave adapter, resulting in a certain insertion loss in the transmission spectrum.

[0092] In the stability test, the average resonant frequency of the unloaded sensor was 27.1 GHz, and the standard deviation of the six test results was 0.007 GHz; the average resonant frequency of the loaded sensor was 26.9 GHz, and the standard deviation of the five test results was 0.008 GHz. Both the unloaded and loaded results remained stable.

[0093] In eight sets of deionized water tests, the resonant frequency splitting increased linearly with increasing molar mass, consistent with the trend of frequency splitting under different dielectric constants. The fitting results are as follows: y =0.048 x +0.215, correlation coefficient R 2 =0.993.

[0094] In four glucose solution tests, solutions of the same concentration were used, and the molar mass of glucose was increased by increasing the volume of the detection solution. The resonant frequency splitting increased linearly with increasing molar mass, consistent with the trend of frequency splitting under different dielectric constants. The fitting results are as follows: y =0.209 x +0.971, correlation coefficient R 2 =0.967.

[0095] In the four glycerol solution tests, the same volume of solution was used, and the glycerol content was increased by increasing the test concentration. The resonant frequency splitting decreased linearly with increasing glycerol concentration. This is because the dielectric constant of glycerol is lower than that of deionized water at room temperature and in the microwave band; therefore, for the same volume, the higher the glycerol concentration, the lower the dielectric constant of the solution. The test results are consistent with the trend of frequency splitting of the sensor under different dielectric constants.

[0096] The fitting result is y =-0.057 x +1.358, correlation coefficient R 2 =0.960.

[0097] Example 4 Application of a surface plasmon sensor in the dynamic detection of the hydrolysis process of thioacetylcholine.

[0098] This embodiment illustrates the detection of the hydrolysis process of thioacetylcholine using a singularity sensor. The specific detection steps are as follows: Preparation of three solutions: Add 1 mg of acetylcholine hydrolase to 10 mL of deionized water and stir for 2 minutes to ensure that the acetylcholine hydrolase is evenly distributed in the deionized water, thus preparing a 100 μg / mL acetylcholine hydrolase solution.

[0099] Add 1g of thioacetylcholine to 10mL of deionized water and stir for 2 minutes to fully dissolve the thioacetylcholine in the deionized water, thus preparing a 100mg / mL thioacetylcholine solution.

[0100] Add 1 mL of 1 mol / mL hydrochloric acid buffer to 49 mL of deionized water and stir for 2 minutes to prepare 20 mmol / mL hydrochloric acid buffer.

[0101] Thioacetylcholine hydrolysis experiment: Take 350 μL of hydrochloric acid buffer (20 mmol / mL), 400 μL of acetylcholine hydrolase solution (100 μg / mL), and 250 μL of thioacetylcholine solution (100 mg / mL) and add them to a 10 mL test tube in sequence. Place the test tube containing the mixed solution into a water bath at 37 °C.

[0102] Every 10 minutes, a 0.4 μL sample of the mixed solution was added to the sensor's sensitive area using a 2 μL microsyringe, while the sensor's transmittance was measured using a vector network analyzer. After each test, the sensor was cleaned with deionized water. The experimental procedure is as follows: Figure 11 As shown, the test results are as follows: Figure 12 As shown in (a) and (b).

[0103] Test Result Analysis: Within one hour of sensing, the number of splits in the transmission spectrum generally showed an increasing trend. The rate of increase was fastest in the first 30 minutes, decreased between 30 and 40 minutes, and remained essentially constant between 40 and 60 minutes. Thioacetylcholine, when dissolved in deionized water, produces polar ATCH... + Cations affect the rotational speed of water molecules, thus binding them. Bound water molecules cannot effectively respond to an external electric field, leading to a decrease in the overall dielectric polarization of the solution. Therefore, before the reaction, ATCH... + The relatively low dielectric constant of the solution results in a lower splitting of the transmission spectrum; as the hydrolysis reaction proceeds, ATCH + As cations are gradually hydrolyzed, the increase in the number of free water molecules enhances the dielectric polarization response of the solution, which macroscopically manifests as an increase in the dielectric constant, exhibiting a nonlinear trend.

[0104] According to the above method, the microwave-based plasma singularity sensor provided by the present invention can achieve qualitative and quantitative detection of the volume or concentration of different solutions, and has excellent sensing performance. It also proves the effectiveness of the sensing test method and analysis of the present invention.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A surface plasmonic sensor, comprising a dielectric substrate, a metallic waveguide, and a subwavelength resonator, characterized in that, The subwavelength resonator has a fan-shaped defect structure.

2. The surface plasmon sensor according to claim 1, characterized in that, The inner arc length of the fan-shaped defect structure is 0.6mm~0.8mm, the outer arc length is 0.7mm~0.8mm, and the side length is 0.2mm~0.4mm, relative to... x The axis is set at a counterclockwise angle of 27° to 33° in the positive direction, preferably at a counterclockwise angle of 23°.

3. The surface plasmon sensor according to claim 1 or 2, characterized in that, The subwavelength resonator includes a central metal disk and circumferentially distributed outer metal strips, with the ratio of the radius of the central metal disk to the length of the outer metal strips being 1:1.5~5.

4. The surface plasmon sensor according to claim 3, characterized in that, The central metal disk has a radius of 0.8mm to 2mm, the outer metal strip has a length of 1mm to 4mm and a width of 0.1mm to 0.5mm, and the circumferential spacing angle between adjacent resonant units is 3 to 10°. The preferred central metal disk has a radius of 1 mm, the outer metal strip has a length of 3 mm and a width of 0.1 mm, the circumferential spacing angle α between adjacent resonant units is 3°, and the period θ is 6°.

5. The surface-like plasma sensor according to any one of claims 1 to 4, characterized in that, The metallic waveguide is composed of rectangular microstrip lines, horn-shaped microstrip lines, and periodically arranged metal pillars. The rectangular microstrip lines have a thickness of 0.035 mm, a length of 5-9 mm, and a width of 1-2 mm. The periodically arranged metal pillars have a thickness of 0.035 mm, a length of 1-2 mm, a width of 0.4-0.5 mm, a period of 0.4-0.8 mm, and a period number of 20-30. Preferably, the rectangular microstrip line has a thickness of 0.035 mm, a length of 7 mm, and a width of 1.6 mm, and the periodically arranged metal pillars have a thickness of 0.035 mm, a length of 1.5 mm, a width of 0.45 mm, a period of 0.6 mm, and a period number of 27.

6. The surface-like plasma sensor according to any one of claims 1 to 5, characterized in that, The length, width, and thickness of the dielectric substrate are 51~53mm, 20~40mm, and 0.5~1mm, respectively.

7. The surface plasmon sensor according to claim 6, characterized in that, The metal waveguide and the subwavelength resonator are coplanarly fabricated on the front side of the dielectric substrate, and the spacing between the metal waveguide and the subwavelength resonator is 0.1~0.3mm, preferably 0.25mm.

8. The surface plasmon sensor according to claim 7, characterized in that, The back of the dielectric substrate is provided with a metal layer, while there is no metal layer at the position opposite the resonator.

9. The application of a surface plasmon sensor as described in any one of claims 1 to 8 in the detection of trace liquids.

10. The application according to claim 9, characterized in that, The trace liquid is selected from any one or more of water, sugars, alcohols, and trace enzymatic reaction solutions.

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