Quasi-BIC terahertz all-dielectric biosensor and preparation method and application thereof

Abstract

The invention relates to the technical field of terahertz biosensors, in particular to a quasi-BIC terahertz all-dielectric biosensor and a preparation method and application thereof. The biosensor comprises a dielectric layer and a substrate layer, the dielectric layer is an array formed by periodically arranging a plurality of all-dielectric metamaterial unit structures, each unit structure is composed of four asymmetric cylindrical structures, the circle centers of the four cylindrical structures are symmetric, the diameters of three of the four cylindrical structures are the same, and the diameters of the three cylindrical structures are the same. The diameter of the other cylindrical structure is different from that of the other three cylindrical structures, the diameter difference is small, and meanwhile, the period of the unit structure, the cylindrical diameter and the cylindrical distance are limited to meet certain conditions, so that a relatively strong electromagnetic field enhancement effect is achieved. The metamaterial structure is degenerated from a continuous domain bound state to a quasi-continuous domain bound state by designing symmetrical breaking, a high Q factor of the device under the terahertz wave band condition is realized, and the sensor has the effects of high sensitivity and low detection limit on low-concentration biological sample detection in the terahertz wave band.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz biosensors, and in particular to a quasi-BIC terahertz all-medium biosensor and a preparation method and application thereof. Background Art

[0002] Electromagnetic metamaterials are sensitive to the surrounding dielectric environment and can enhance the electromagnetic field locally, so they have a wide range of application potential in the field of sensing. The working principle of biosensors based on electromagnetic metamaterials is to convert the change of the dielectric constant around the sensor into the change of the frequency domain spectrum of the electromagnetic signal, which is specifically manifested as the shift of the resonance peak position. The dielectric constant of the object to be tested is calculated by the shift of the resonance peak, and then the concentration of the sample to be tested is calculated. Because metamaterials have the effect of enhancing the electromagnetic field, the detection sensitivity of the sensor is greatly improved.

[0003] Terahertz (THz) electromagnetic waves refer to electromagnetic waves with a frequency of 0.1-1 THz, which have the characteristics of low energy (the energy of photons with a frequency of 1 THz is about 4 meV) and will not cause ionization damage and changes in biological tissues. Therefore, terahertz metamaterial biosensors have the characteristics of high sensitivity, low detection limit, label-free, non-destructive detection, etc., and have broad application prospects in the detection of extremely low concentration biological samples (such as tumor markers, cytokines, etc.). Among them, sensitivity, biocompatibility, pretreatment complexity, reliability, etc. are the main indicators for measuring the performance of biosensors. Among them, the device Q factor (quality factor) is one of the important performance indicators of biosensors. The larger the Q factor, the sharper the resonance peak of the device's frequency domain transmission spectrum and the higher the sensitivity.

[0004] Metal-based metamaterials are the most widely studied metamaterial system. However, due to the thermal effect of electric current in metal materials, metal-based metamaterials have large losses and low Q factors, which limits the sensitivity of metal-based metamaterial biosensors. In order to obtain high-Q-factor devices, all-dielectric metamaterials are increasingly valued and are increasingly widely used in the field of biosensing.

[0005] Bound continuum states (BICs) are an emerging research hotspot in the field of metamaterials in recent years. BICs are a type of special electromagnetic eigenstate whose frequency is within the radiation continuum but is completely locally confined. Since the internal and external modes of the BIC cannot be coupled, it is completely non-radiative and can only be excited by local sources inside the structure. Theoretically, it has an infinite Q factor. However, the infinite Q factor of BIC in the strict sense cannot be measured, so it cannot be applied to sensors. In order to obtain a practical high-Q factor device, it is necessary to degenerate the BIC into a quasi-BIC mode (quasi-continuum bound state, QBIC), causing a small amount of energy leakage, and then obtain a practically measurable high-Q factor device. There are usually two types of BIC, namely symmetry-protected BIC and accidental BIC. From the perspective of design and processing, the symmetry-protected BIC structure is easier to realize, and the quasi-BIC mode can be easily obtained by destroying the symmetry. For example, Chinese patent CN114577753B discloses a high-Q refractive index sensor based on a quasi-continuous domain bound state and a preparation method thereof. By opening a gap on one side surface of an all-dielectric metasurface unit of a square block structure, the symmetry of the structure in the x direction is destroyed, and the continuous domain bound state is converted into a quasi-continuous domain bound state, thereby obtaining an extremely high Q value, which greatly improves the sensing performance of the refractive index sensor. However, the device is mainly used in the near-infrared light band, and there is still little research on high-Q value biosensors in the terahertz band. Summary of the invention

[0006] In view of the shortcomings and problems of the prior art, in order to improve the sensitivity of the all-dielectric metamaterial biosensor working in the terahertz band, the present invention proposes a quasi-BIC terahertz all-dielectric biosensor and a preparation method and application thereof. The specific scheme is as follows: A quasi-BIC terahertz all-dielectric biosensor comprises a dielectric layer and a substrate layer, wherein the dielectric layer is composed of a plurality of unit structures of all-dielectric metamaterials arranged periodically to form an array, wherein the unit structure is composed of four asymmetric cylindrical structures, wherein the centers of the four cylindrical structures are symmetrical, wherein three of the cylindrical structures have the same diameter of d, and the diameter of another cylindrical structure is different from the other three, d1, d=70-90 μm, d1=70-90 μm, d≠d1, and the asymmetry constant α is defined as:

[0007] The asymmetric constant α is 0.02-0.2. The breaking of symmetry, i.e. the introduction of asymmetry, causes the metamaterial structure to degenerate from a continuous domain bound state (BIC) to a quasi-continuous domain bound state (QBIC), thus achieving a high Q factor of the device.

[0008] Furthermore, the height of the dielectric layer is h1, and the relationship between the diameter of each cylinder and the height h1 is: 3≥h1 / d≥0.5, and / or 3≥h1 / d1≥0.5, so that the resonant mode in the spectrum is clear and the resonant peaks do not overlap.

[0009] Furthermore, the period length and / or period width of the unit structure is P=290-490 μm, and the distance between two adjacent cylindrical structures with the same diameter in the unit structure is a=10-30 μm.

[0010] Furthermore, the period length and / or period width P of the unit structure satisfies P≥3d+2a, four cylinders form a group of unit structures, a strong near-field coupling effect occurs within the four cylinders, and a strong electromagnetic field enhancement effect is achieved. There is a large spacing between units, so that the cylinders within the unit have almost no far-field coupling effect with the cylinders of other units.

[0011] Furthermore, the dielectric layer is made of high-resistance single-crystal silicon material, with a resistivity of more than 5000Ω·cm and a thickness h1 of 100-600μm.

[0012] Furthermore, the substrate layer is made of silicate glass material. Specifically, the silicate glass may be Schott BF33 glass, Schott BK7 glass, or Corning 7070 glass. The substrate layer has a thickness h2 of 200-500 μm, and a real part of a dielectric constant ε<3 in a frequency band of 0.1-1 THz.

[0013] The preparation method of the quasi-BIC terahertz all-medium biosensor comprises the following steps: Step 1: Anodically bonding the unpatterned dielectric layer to the substrate layer; Step 2: Then, glue is applied on the surface of the dielectric layer, and the surface is exposed and patterned by photolithography to obtain a unit structure array pattern consisting of an asymmetric four-cylinder structure; Step 3: Etching the dielectric layer again until the substrate layer is cut off, thereby obtaining a dielectric layer consisting of an asymmetric four-cylinder group; Step 4: The surface of the whole device is modified with specific antibodies to obtain a biosensor.

[0014] Furthermore, in step 4, the surface of the substrate is firstly cleaned with a mixture of H2SO4 and H2O2, then bombarded with oxygen plasma, and then immersed in a 3-aminopropyltriethoxysilane solution, and then immersed in a solution of carbodiimide and N-hydroxypropyltriethoxysilane. Succinylsulfide Imine The sample is immersed in a mixed solution of the solution and the corresponding antibody of the biological sample to be tested.

[0015] Furthermore, the volume ratio of H2SO4 and H2O2 solutions is 4:1; the power of oxygen plasma is 30-80 W, and the bombardment time is 2-8 min; the volume fraction of 3-aminopropyltriethoxysilane solution is 1%-10%, the solution temperature during immersion is 60-90°C, and the immersion time is 1-4 hours; carbodiimide, N-hydroxy 2-Methylthiosuccinimide The temperature of the mixed solution of the solution and the antibody corresponding to the biological sample to be tested is 35-39° C., and the soaking time is 1-24 hours.

[0016] The above-mentioned quasi-BIC terahertz all-medium biosensor is applied in the field of biological sample detection, wherein the biological samples include proteins, nucleic acids, polypeptides, and cytokines.

[0017] The beneficial effects of the present invention are: (1) The present invention uses all-dielectric metamaterials to construct biosensors. Dielectric metamaterials have a larger Q factor, and silicon has good biocompatibility. It is easy to form silane bonds during the modification process and is easy to bind to antibodies. (2) The present invention is based on a symmetrical four-cylinder unit. By adjusting the diameter of one of the cylinders, the symmetry of the unit is destroyed, so that the device degenerates from BIC to quasi-BIC, introducing asymmetry. The asymmetric four-cylinder unit based on the quasi-BIC mode has obvious resonance peak splitting and a large Q factor. At the same time, the range of the asymmetric constant α is limited, and d and d1 are controlled to have a certain difference but not too large, while meeting the precision and operability of micro-nano processing technology, so that the Q factor working in the terahertz band is high and the preparation is feasible; (3) In addition, in order to further control the strong near-field coupling effect within the four cylinders, there is a large spacing between the units, so that the cylinders within the unit have almost no far-field coupling effect with other unit cylinders, and the period length and period width of the unit structure are limited to meet certain conditions with the cylinder diameter and cylinder spacing to achieve a stronger electromagnetic field enhancement effect; (4) In addition, the cylindrical structure used in this sensor has the clearest resonant mode and is not prone to high-order harmonics and multi-modal overlapping peaks. Therefore, it has a strong advantage as a biosensor. However, metamaterial structures with more edges and corners (parallel sides), such as square columns, generate more high-order harmonics and more miscellaneous peaks. (5) The bonding-photolithography-etching process adopted by the present invention facilitates large-scale device production, improves device reliability and reduces costs. The silicon-glass bonding process is adopted, and the upper dielectric layer is a high-resistance silicon single crystal. The intrinsic electromagnetic parameters such as the dielectric constant are stable and unchanged. Compared with the silicon film obtained by sputtering deposition, the electromagnetic parameters are relatively stable, and the resistivity fluctuation is small. The technical route of the present invention is more convenient and reliable for device design; and the preparation method finally performs amino modification on the surface of the biosensor, which further improves the biocompatibility and selectivity of the biosensor.

[0018] The present invention constructs an asymmetric four-cylinder unit, so that the device degenerates into a quasi-BIC, introduces asymmetry, and has obvious resonance peak splitting based on the quasi-BIC mode, thereby improving its Q factor in the terahertz band, so that the biosensor of the present invention can be used for the detection of biological samples including proteins, nucleic acids, polypeptides, cytokines, etc., has a lower detection limit and higher sensitivity, and will not cause ionization damage and changes to biological tissues. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The embodiments of the present invention are further described below with reference to the accompanying drawings, in which: Figure 1 The schematic diagram (left) and scanning electron microscope image (right) of the quasi-BIC terahertz all-medium biosensor of the present invention are shown; Figure 2 A schematic top view of a unit structure in the quasi-BIC terahertz all-medium biosensor of the present invention is shown; Figure 3 The THz transmission spectrum (left) and sensitivity fitting curve (right) of the biosensor of Example 1 of the present invention are shown; Figure 4 The THz transmission spectrum (left) and sensitivity fitting curve (right) of the biosensor of Example 2 of the present invention are shown; Figure 5 A schematic top view of a unit structure of a biosensor according to Comparative Example 1 of the present invention is shown; Figure 6 The THz transmission spectrum (left) and sensitivity fitting curve (right) of the biosensor of Comparative Example 1 of the present invention are shown; Figure 7 A schematic top view of a unit structure of a biosensor according to Comparative Example 2 of the present invention is shown; Figure 8 The THz transmission spectrum of the biosensor of Comparative Example 2 of the present invention is shown. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Example 1

[0021] The asymmetric four-cylinder unit metamaterial biosensor was obtained by anodic bonding, photolithography patterning, etching, and biospecific modification. The specific preparation process is as follows: the high-resistance silicon (dielectric layer) to be bonded is connected to the positive electrode of the power supply, the BF33 glass (substrate layer) is connected to the negative electrode, the glass-silicon wafer is heated to 350°C at a voltage of 1000V, and the bonding is carried out for 30 min, high-resistance silicon is bonded to BF33 glass; positive resist is applied on the surface of the dielectric layer, exposed, and photolithographic patterning is performed to obtain a unit structure array pattern composed of asymmetric four cylinders; the upper layer of high-resistance silicon is etched, and the etching depth is cut off to the bonding interface; a mixed solution of H2SO4 and H2O2 with a volume ratio of 4:1 is used to clean the surface of the entire device, and then the surface of the dielectric layer is cleaned with oxygen plasma, with an oxygen plasma power of 50W and a bombardment time of 6min to remove the upper photoresist, increase the roughness of the device, and make its surface easy to bind to antibodies. After cleaning, the device is immersed in a 3-aminopropyltriethoxysilane solution with a volume fraction of 5% at a temperature of 80°C for 3h, and then immersed in a mixed solution of carbodiimide solution, N-hydroxysulfosuccinimide and the corresponding antibody of the biological sample to be tested at 35°C for 10h for specific antibody modification to obtain a biosensor. The dielectric layer is high-resistance silicon, and the substrate layer is Schott BF33 glass. The resistivity of high-resistance silicon is 8000Ω·cm. The dielectric layer is composed of a plurality of high-resistance silicon unit structures arranged periodically to form an array. The unit structure is composed of four asymmetric cylindrical structures. The four cylindrical structures are symmetrical in center. Three of the cylindrical structures have the same diameter d, and the diameter of the other cylindrical structure is different from the other three, which is d1. The period length and period width of the unit structure are the same, which is P=300 μm. The diameter of the three identical cylinders is d=80 μm, and the diameter of the other cylinder is d1=74 μm. The spacing between two adjacent cylinders of the same diameter is a=20 μm. The thickness of the dielectric layer h1 is 150 μm; the thickness of the substrate layer glass material h2 is 300 μm. In the 0.1-1 THz frequency band, the real part of the dielectric constant ε=2.14. The period length or period width of the unit structure means that the unit structure includes four asymmetric cylindrical structures and the spaces between them, the dielectric layer is composed of periodically arranged unit structures, adjacent unit structures are arranged without gaps, and the length and width of the unit structure are called the period length or period width.

[0022] The prepared device was applied to the detection of cytokine interleukin 6 (IL-6). Five different concentrations of IL-6 biological sample solutions were prepared with bovine serum as solvent: 100 pg / mL, 1 ng / mL, 10 ng / mL, 100 ng / mL, and 1 μg / mL. The THz transmission spectra and sensitivity fitting results are shown in the attached figure. Figure 3 shown.

[0023] For the above biosensor, the two resonance peaks can be used as biosensor characteristic peaks in the range of 100 pg / mL to 1 μg / mL. The detection limit for IL-6 is about 100 pg / mL, and the asymmetry constant α=0.144. The height of the cylinder is equivalent to the diameter, h1 / d=1.875. The resonance peak Q factor is calculated using the formula Q=f / FWHM, where f is the resonance peak frequency and FWHM is the half-width of the resonance peak. The Q factors of the two resonance peaks are both about 99.

[0024] The frequency shift ∆f is linearly related to the logarithm of the concentration. When the IL-6 concentration is in the range of 100 pg / mL to 1 μg / mL, the resonance peak position f and the concentration c are fitted to obtain formulas (1) and (2). The absolute value of the slope of the equation represents the sensitivity. The larger the absolute value of the slope, the higher the sensitivity. The sensitivity of the device is 0.00253 and 0.00229.

[0025] f=-0.00253×lg(c)+0.6114 (1) f=-0.00229×lg(c)+0.6216 (2) Example 2

[0026] An asymmetric four-cylinder unit metamaterial biosensor is obtained by anodic bonding, photolithography patterning, etching, and biospecific modification (the specific preparation process is the same as in Example 1). The dielectric layer is high-resistance silicon, the substrate layer is Schott BF33 glass, the resistivity of high-resistance silicon is 8000Ω·cm, the dielectric layer is composed of a plurality of high-resistance silicon unit structures arranged periodically to form an array, the unit structure is composed of four asymmetric cylindrical structures, the center of the four cylindrical structures is symmetrical, three cylindrical structures have the same diameter d, and the diameter of another cylindrical structure is different from the other three, which is d1, the period length and period width of the unit structure are the same, which is P=310μm, the diameter of three identical cylinders is d=86 μm, the diameter of another cylinder is d1=80 μm, the cylinder spacing is a=15 μm, the dielectric layer thickness h1 is 180 μm; the thickness of the substrate layer glass material h2 is 280 μm, and in the 0.1-1 THz frequency band, the real part of the dielectric constant ε=2.14.

[0027] The prepared device was applied to the detection of cytokine interleukin 6 (IL-6). Six different concentrations of IL-6 biological sample solutions were prepared with bovine serum as solvent: 100 pg / mL, 1 ng / mL, 10 ng / mL, 100 ng / mL, 1 μg / mL, and 10 μg / mL. The THz transmission spectra and sensitivity fitting results are shown in Figure 2. Figure 4 shown.

[0028] For the above biosensor, the two resonance peaks can be used as biosensor characteristic peaks in the range of 100 pg / mL to 10 μg / mL. The detection limit for IL-6 is about 100 pg / mL, and the asymmetry constant α=0.135. The height of the cylinder is equivalent to the diameter, h1 / d=2.093. The resonance peak Q factor is calculated using the formula Q=f / FWHM, where f is the resonance peak frequency and FWHM is the half-width of the resonance peak. The Q factors of the two resonance peaks are 78 and 88 respectively.

[0029] Frequency Shift It is linearly related to the logarithm of the concentration. When the IL-6 concentration is in the range of 100 pg / mL to 10 μg / mL, the resonance peak position f and the concentration c are fitted to obtain formulas (3) and (4). The absolute value of the slope of the equation represents the sensitivity. The larger the absolute value of the slope, the higher the sensitivity. The sensitivity of the device is 0.00285 and 0.00273.

[0030] f=-0.00285×lg(c)+0.6539 (3) f=-0.00273×lg(c)+0.7525 (4)

[0031] Comparative Example 1

[0032] An asymmetric four-block metamaterial biosensor is obtained by anodic bonding, photolithography, etching, and surface modification. The preparation process is the same as in Example 1. The dielectric layer is high-resistance silicon, and the substrate layer is Schott BF33 glass. The resistivity of high-resistance silicon is 8000Ω·cm, and the thickness h1 is 150 μm; the thickness h2 of the bottom glass material is 300 μm, and in the 0.1-1 THz frequency band, the real part of the dielectric constant ε=2.14. The period length and period width of the unit structure are the same, P=300 μm, the side length of the three identical squares is 80 μm, the side length of the other square is 74 μm, and the square spacing is 20 μm. As shown in the attached Figure 5 shown.

[0033] The prepared device was applied to the detection of cytokine interleukin 6 (IL-6). Five different concentrations of IL-6 biological sample solutions were prepared with bovine serum as solvent: 100 pg / mL, 1 ng / mL, 10 ng / mL, 100 ng / mL, and 1 μg / mL. The THz transmission spectra and sensitivity fitting results are shown in the attached figure. Figure 6 shown.

[0034] Depend on Figure 5It can be seen that when the IL-6 concentration is 100 pg / mL, the peak position of its resonance peak is very different from that of the device modified with only IL-6 antibody, and is almost indistinguishable, so the detection limit is about 100 pg / mL. The Q factor of the resonance peak is about 57 (less than the Q factor 99 in Example 1 and 78 and 88 in Example 2), and the resonance peak position f and concentration c are fitted to obtain formula 5.

[0035] f=-0.00198×lg(c)+0.6266 (5) The device sensitivity is 0.00198 (less than the sensitivities of 0.00253 and 0.00229 in Example 1, and also less than the sensitivities of 0.00285 and 0.00273 in Example 2). In addition, a stray peak is generated at 0.57 THz, and the relationship between the low-frequency resonance peak and the concentration near 0.6-0.61 THz is not obvious. Only one resonance peak near 0.626 satisfies the linear relationship between the resonance peak position f and the logarithm of the concentration c. It can be seen that the performance of the device in Comparative Example 1 is obviously inferior to that in Example 1.

[0036] Comparative Example 2 An asymmetric four-cylinder unit metamaterial biosensor is obtained by anodic bonding, photolithography patterning, etching, and biospecific modification. The specific preparation process is the same as in Example 1. The dielectric layer is high-resistance silicon, the substrate layer is Schott BF33 glass, the resistivity of high-resistance silicon is 8000Ω·cm, the dielectric layer is composed of a plurality of high-resistance silicon unit structures arranged periodically to form an array, the unit structure is composed of four asymmetric cylindrical structures, the center of the four cylindrical structures is symmetrical, three of the cylindrical structures have the same diameter d, and the diameter of the other cylindrical structure is different from the other three, which is d1. The period length and period width of the unit structure are the same, which is P=270 μm, the diameter of the three identical cylinders is d=90 μm, the diameter of the other cylinder is d1=70 μm, the cylinder spacing a=35 μm, the dielectric layer thickness h1 is 150 μm; the thickness of the substrate layer glass material h2 is 300 μm, and in the 0.1-1 THz frequency band, the real part of the dielectric constant ε=2.14. Asymmetry constant α=0.395. The height of the cylinder is equivalent to the diameter, h1 / d=1.67. Figure 7 shown.

[0037] The prepared device was applied to the detection of cytokine interleukin 6 (IL-6). Six different concentrations of IL-6 biological sample solutions were prepared with bovine serum as solvent: 100 pg / mL, 1 ng / mL, 10 ng / mL, 100 ng / mL, 1 μg / mL, and 10 μg / mL. The THz transmission spectrum results are shown in the attached figure. Figure 8 shown.

[0038] The resonance peak Q factor is calculated using the formula Q=f / FWHM, where f is the resonance peak frequency and FWHM is the half-peak width of the resonance peak. The Q factors of the two resonance peaks are both about 18. Since the asymmetry constant α is large, the Q factor is small, and since the period P is small, the four cylinders cannot form an effective unit to produce the field coupling enhancement effect. Through experiments, it can be observed that the logarithmic law of the frequency shift ∆f and the concentration is not obvious, and a linear equation cannot be fitted, so it cannot be used as a biosensor.

[0039] Some exemplary embodiments of the present invention are described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the scheme obtained thereby is still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without making creative work, that is, all modifications, equivalent substitutions and improvements made within the spirit and principles of this application, fall within the protection scope required by the present invention.

Claims

1. A quasi-BIC terahertz all-dielectric biosensor, comprising a dielectric layer and a substrate layer, characterized in that: The dielectric layer is composed of a plurality of unit structures of all-dielectric metamaterials arranged periodically to form an array, and the unit structure is composed of four asymmetric cylindrical structures, and the centers of the four cylindrical structures are symmetrical, wherein three of the cylindrical structures have the same diameter of d, and the diameter of the other cylindrical structure is different from the other three, which is d1, d=70-90 μm, d1=70-90 μm, d≠d1, and the asymmetric constant α is defined as: The asymmetry constant α=0.02-0.

2.

2. The quasi-BIC terahertz all-medium biosensor according to claim 1, characterized in that: The height of the dielectric layer is h1, and the relationship between the diameter of each cylinder and the height h1 is: 3≥h1 / d≥0.5, and / or 3≥h1 / d1≥0.

5.

3. The quasi-BIC terahertz all-medium biosensor according to claim 1, characterized in that: The period length and / or period width of the unit structure is P=290-490 μm, and the distance between two adjacent cylindrical structures with the same diameter in the unit structure is a=10-30 μm.

4. The quasi-BIC terahertz all-medium biosensor according to claim 3, characterized in that: The period length and / or period width P of the unit structure satisfies P≥3d+2a.

5. The quasi-BIC terahertz all-medium biosensor according to claim 1, characterized in that: The dielectric layer is made of high-resistance single-crystal silicon material, with a resistivity of more than 5000Ω·cm and a thickness h1 of 100-600μm.

6. The quasi-BIC terahertz all-medium biosensor according to claim 1, characterized in that: The substrate layer is made of silicate glass material, the thickness h2 of the substrate layer is 200-500 μm, and the real part of the dielectric constant ε is less than 3 in the frequency band of 0.1-1 THz.

7. The method for preparing the quasi-BIC terahertz all-medium biosensor according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Anodically bonding the unpatterned dielectric layer to the substrate layer; Step 2: Then, glue is applied on the surface of the dielectric layer, and the surface is exposed and patterned by photolithography to obtain a unit structure array pattern consisting of an asymmetric four-cylinder structure; Step 3: Etching the dielectric layer again until the substrate layer is cut off, thereby obtaining a dielectric layer consisting of an asymmetric four-cylinder group; Step 4: The surface of the whole device is modified with specific antibodies to obtain a biosensor.

8. The method for preparing the quasi-BIC terahertz all-medium biosensor according to claim 7, characterized in that: In step 4, the sample is first cleaned with a mixture of H2SO4 and H2O2, then bombarded and cleaned with oxygen plasma, then immersed in a 3-aminopropyltriethoxysilane solution, and then immersed in a mixed solution of carbodiimide, N-hydroxysulfosuccinimide solution and the antibody corresponding to the biological sample to be tested.

9. The method for preparing the quasi-BIC terahertz all-medium biosensor according to claim 8, characterized in that: The volume ratio of H2SO4 and H2O2 solutions is 4:1; the power of oxygen plasma is 30-80 W, and the bombardment time is 2-8 min; the volume fraction of 3-aminopropyltriethoxysilane solution is 1%-10%, the solution temperature during immersion is 60-90°C, and the immersion time is 1-4 hours; the temperature of the mixed solution of carbodiimide, N-hydroxysulfosuccinimide solution and the corresponding antibody of the biological sample to be tested is 35-39°C, and the immersion time is 1-24 hours.

10. Application of the quasi-BIC terahertz all-medium biosensor according to any one of claims 1 to 6 in the field of biological sample detection, characterized in that: The biological samples include proteins, nucleic acids, polypeptides, and cytokines.

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