Optical metasurface resonant cavity sensor and preparation method thereof

Abstract

The present invention discloses an optical metasurface resonant cavity sensor and a preparation method thereof, comprising a liquid inlet end microfluidic component, a liquid outlet end microfluidic component, and an optical metasurface resonant cavity chip embedded in the two; the optical metasurface resonant cavity chip comprises, from bottom to top, a lower transparent substrate, a lower distributed Bragg reflector, a dielectric metasurface built on the lower distributed Bragg reflector, and metal stages at both ends, an upper distributed Bragg reflector, and an upper transparent substrate; the dielectric metasurface is located in the resonant cavity and is composed of nanocolumns arranged in a two-dimensional periodic manner; the upper and lower distributed Bragg reflectors are formed by two films stacked alternately in sequence. The present invention has an air dielectric resonant cavity with a fixed cavity length, and after the liquid medium is passed into the resonant cavity, ultra-strong light field confinement can be achieved in the liquid medium on the sensing surface adjacent to the nanocolumns, so that the sensor has ultra-high sensitivity and quality factor while obtaining an extremely high Q value.

Description

Technical Field

[0001] The present invention relates to the fields of nanophotonics, micro-nano processing, optoelectronic devices and biosensing, and in particular to an optical supersurface resonant cavity sensor and a preparation method thereof. Background Art

[0002] Optical biosensors have attracted much attention in infectious disease monitoring applications due to their advantages such as high sensitivity, high flexibility and real-time detection. They can quantitatively monitor the local refractive index changes caused by the binding of biorecognition elements on the sensing surface to the target, and then convert the optical property changes into readable response signals (such as resonant wavelength shift) through advanced analyzers. Among various types of optical sensors, metal- or dielectric-based nanophotonic biosensors have emerged due to their excellent light manipulation capabilities in subwavelength volumes. Near-field light-matter interactions dominate the sensitivity of nanoresonator sensors, and researchers can adjust the resonance properties to adapt to various biological analytes by adjusting the device structure, configuration or material design of the nanoresonator sensor.

[0003] Metal-based sensors, such as localized surface plasmon resonance and surface lattice resonance, can achieve local field confinement within the nanometer-scale attenuation length, resulting in extremely high surface refraction sensitivity. However, such sensors are limited by the inherent high thermal loss of metal materials or the far-field radiation loss of the device, which can usually only reach the order of tens. Other advanced plasma resonator modes, such as bound state modes in the continuum and devices based on Fabry-Perot coupling modes, can increase their Q values ​​to the order of hundreds. However, the performance of metal nanophotonic sensors is easily affected by temperature changes and has low compatibility with CMOS (Complementary Metal Oxide Semiconductor) devices, which limits their potential for large-scale practical applications.

[0004] In order to address the multifaceted limitations of metal materials, dielectric-based nanophotonic sensors have been proposed, such as bound state modes in nanoscale metasurface-based continua, and micrometer-scale microspheres, microbubbles, and microring resonators for real-time and label-free biosensing. They can provide considerable near-field enhancement in nanoscale volumes with minimal material loss. The whispering gallery sensors reported so far have achieved ultra-high Q values ​​(over 10 6 ).

[0005] However, in biosensing, sensitivity depends not only on the device's strong light field confinement capability, but also on the spatial match between the binding layer of the analyte and the confined electric field. In order to achieve high optical performance resonators (such as high Q values), strong confinement of the light field is necessary, which inevitably reduces the interaction strength of the light field with the surrounding environment, resulting in lower sensitivity. This "trade-off effect" has become a major challenge facing nanophotonic resonator sensors. However, in order to achieve the sensing effect, the light field in the cavity medium needs to be strong enough, rather than being confined in the structure, to achieve a strong enough light-matter interaction.

[0006] In recent years, a type of "metasurface in resonant cavity" coupling mode has achieved optical control with higher degrees of freedom by adding metasurfaces to distributed Bragg reflectors. In one of the reported works, a one-dimensional strip-shaped Al grating was embedded in a Si / SiO distributed Bragg reflector resonant cavity to make a spectroscopic polarization filter, where the cavity medium was SiO. In another study, a two-dimensional square Al metasurface was embedded in a SiO2 / Ta2O5 distributed Bragg reflector to achieve laser polarization control, where the cavity medium was SiO2. In another study, a customized SiO2 array was embedded in a SiO2 / TiO2 distributed Bragg reflector to achieve phase control, where the cavity medium was air, one end of the distributed Bragg reflector was fixed in position, and the other end of the distributed Bragg reflector was connected to a three-axis stage for open alignment. This type of three-dimensional light field control Metacavity is very suitable as a biosensor to increase the overlap area of ​​the electric field-the object to be tested.

[0007] However, in the above three works, other media exist in some resonant cavities, and all resonant cavities are unable to establish suitable sample inlets and outlets to allow the analytes to enter the cavity. Summary of the invention

[0008] In view of the shortcomings of the prior art, the present invention proposes an optical metasurface resonant cavity sensor and a preparation method thereof. The specific technical scheme is as follows:

[0009] An optical metasurface resonant cavity sensor comprises an optical metasurface resonant cavity chip, and a liquid inlet microfluidic component and a liquid outlet microfluidic component; two ends of the optical metasurface resonant cavity chip are respectively embedded in the liquid inlet microfluidic component and the liquid outlet microfluidic component; a liquid inlet is provided on the liquid inlet microfluidic component, and a liquid outlet is provided on the liquid outlet microfluidic component;

[0010] The optical metasurface resonant cavity chip comprises, from bottom to top:

[0011] a lower transparent substrate;

[0012] Lower distributed Bragg reflector;

[0013] a dielectric metasurface built on the underlying distributed Bragg reflector;

[0014] Metal stages are built on both ends of the lower distributed Bragg reflector;

[0015] upper distributed Bragg reflector;

[0016] an upper transparent substrate;

[0017] The upper distributed Bragg reflector and the lower distributed Bragg reflector are bonded together through the metal platform to form a resonant cavity inside; the metal platform is made of copper;

[0018] The dielectric metasurface is located in the resonant cavity and is composed of nanocolumns arranged in a two-dimensional periodic pattern;

[0019] The lower distributed Bragg reflector and the upper distributed Bragg reflector are formed by alternately stacking a first film and a second film in sequence.

[0020] Furthermore, the nanorods are Si3N4 or SiO2.

[0021] Furthermore, the first film is SiO2, and the second film is Ta2O5.

[0022] Furthermore, the lower transparent substrate and the upper transparent substrate are both sapphire substrates.

[0023] Furthermore, the cavity length of the resonant cavity is 1-5 μm.

[0024] Furthermore, the nanocolumns are cylindrical with a diameter of 180-220 nm, a height of 180-200 nm, and a spacing of 400-600 nm.

[0025] Furthermore, the upper distributed Bragg reflector and the lower distributed Bragg reflector are both composed of SiO2 films and Ta2O5 films alternately stacked in sequence for no less than 5 times, and the product of the thickness and the refractive index of the SiO2 film is equal to the product of the thickness and the refractive index of the Ta2O5 film.

[0026] Furthermore, the SiO2 film and the Ta2O5 film in the upper distributed Bragg reflector and the lower distributed Bragg reflector are alternately stacked 10 times.

[0027] A method for preparing an optical metasurface resonant cavity sensor comprises the following steps:

[0028] Step 1: prepare the optical metasurface resonant cavity chip, the liquid inlet microfluidic component and the liquid outlet microfluidic component respectively;

[0029] The preparation of the optical metasurface resonant cavity chip includes:

[0030] (1) Alternately depositing thin film 1 and thin film 2 on a transparent substrate to form a distributed Bragg reflector;

[0031] (2) depositing a dielectric film on the surface of the distributed Bragg reflector;

[0032] (3) Spin coating EBL photoresist on the dielectric film, exposing, developing, and obtaining a pattern of the dielectric metasurface;

[0033] (4) Etching and degumming to obtain nanorods;

[0034] (5) depositing a metal film layer at both ends of the distributed Bragg reflector with nanopillars obtained in step (4) to obtain a lower distributed Bragg reflector modified with a dielectric metasurface; depositing a metal film layer at both ends of the distributed Bragg reflector obtained in step (1);

[0035] (6) bonding the lower distributed Bragg reflector modified by the dielectric metasurface obtained in step (5) and the distributed Bragg reflector after the metal film layer is deposited to obtain an optical metasurface resonant cavity chip;

[0036] The preparation of the liquid inlet microfluidic component and the liquid outlet microfluidic component includes:

[0037] (1) Solidify the lower layer of PDMS in a flat-bottom container;

[0038] (2) placing a mold sheet on the lower PDMS layer, wherein the thickness of the mold sheet is equal to twice the thickness of the optical metasurface resonant cavity chip, and the dimension in the direction perpendicular to the plane composed of the thickness direction and the liquid flow direction is equal to the width of the optical metasurface resonant cavity chip;

[0039] (3) curing the upper PDMS layer on the mold sheet and the lower PDMS layer in step (2) to obtain a PDMS module with upper and lower parts integrated;

[0040] (4) Take out the PDMS module from the flat-bottom container and cut it in the mold sheet to separate it into two parts;

[0041] (5) punching a hole in one part of the PDMS to form a liquid inlet, thereby obtaining a liquid inlet end microfluidic component; punching a hole in another part of the PDMS to form a liquid outlet, thereby obtaining a liquid outlet end microfluidic component;

[0042] Step 2: Encapsulate the two ends of the optical metasurface resonant cavity chip in a liquid inlet microfluidic component and a liquid outlet microfluidic component respectively to form an optical metasurface resonant cavity sensor.

[0043] The beneficial effects of the present invention are as follows:

[0044] (1) The optical metasurface resonant cavity sensor of the present invention has an air resonant cavity with a fixed cavity length and matching microfluidic components at the liquid inlet and outlet ends, so that the liquid medium can pass into the resonant cavity sensor and a stable cavity length is ensured, so that the optical metasurface resonant cavity chip can be used as a stable sensor.

[0045] (2) After a liquid medium is injected into the resonant cavity of the optical metasurface resonant cavity sensor of the present invention, ultra-strong light field confinement can be achieved on the sensing surface adjacent to the nanopillars, so that the optical metasurface resonant cavity sensor can obtain an extremely high Q value while ensuring an extremely high intensity of light-matter interaction on the sensing surface, thereby obtaining ultra-high sensitivity and quality factor. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart for preparing the optical metasurface resonant cavity chip of Example 1.

[0047] Figure 2 This is a flow chart for preparing the liquid inlet end microfluidic component and the liquid outlet end microfluidic component of this embodiment.

[0048] Figure 3 Schematic diagram of the structure of the optical metasurface resonant cavity sensor of Example 1.

[0049] Figure 4 The physical image and the SEM images of the cross section and the surface of the optical metasurface resonant cavity chip of Example 1 are shown; wherein: Figure 4 (a) is the actual picture, (b) is the SEM picture of the cross section and the enlarged picture of the metasurface.

[0050] Figure 5 Schematic diagram and actual picture of the optical metasurface resonant cavity sensor of Example 1 when the sample solution is passed through it.

[0051] Figure 6 2. The simulated and experimental transmission spectra of the optical metasurface resonant cavity sensor of Example 1.

[0052] Figure 7 3. The simulated surface electric field distribution of the three optical modes of the optical metasurface resonant cavity sensor of Example 1.

[0053] Figure 8 When a 100 nm aluminum oxide film is added to the inner surface of the optical metasurface resonant cavity sensor of Example 1, the resonance peaks of the three modes shift.

[0054] Fig. 9 When ethanol solutions with different volume fractions are introduced into the cavity, the resonance peak wavelength of the optical metasurface resonant cavity sensor of Example 1 shifts.

[0055] Fig.10 The experimental Q value changes of the three modes of the optical metasurface resonant cavity sensor of Example 1.

[0056] Fig.11 The virus particle detection laboratory uses optical metasurface resonant cavity sensors to carry out the process of surface biofunctionalization.

[0057] Fig.12 These are the experimental results of the shift of the resonance peak wavelength relative to different COVID-19 Omicron BF.7 pseudovirus loads when the optical metasurface resonant cavity sensor detects the COVID-19 Omicron BF.7 pseudovirus.

[0058] Fig.13 When the logarithm of the distributed Bragg reflector is adjusted for Examples 2 to 6, the transmission spectrum of the optical metasurface resonant cavity sensor changes.

[0059] Fig.14 Changes in the Q value and transmission intensity of the optical metasurface resonant cavity sensor when the logarithm of the distributed Bragg reflector is adjusted for Examples 2 to 6.

[0060] Fig.15 When the distributed Bragg reflector logarithm is adjusted for Examples 2 to 6, changes in the bulk refractive index sensing sensitivity, bulk refractive index sensing quality factor, surface sensing brightness, and surface sensing quality factor of the optical metasurface resonant cavity sensor.

[0061] Fig.16 It is the corresponding signal of the transmission spectrum of the optical metasurface resonant cavity sensor with a cavity length of 1 μm in Example 7 when the refractive index of the medium in the cavity is changed.

[0062] Fig.17 It is the corresponding signal of the transmission spectrum of the optical metasurface resonant cavity sensor with a cavity length of 5 μm in Example 8 when the refractive index of the medium in the cavity is changed.

[0063] Fig.18 The Q value of the optical metasurface resonant cavity sensor varies with the structural parameters, where the structural parameters include the resonant cavity length, the diameter, height and spacing of the dielectric metasurface.

[0064] Fig.19 The surface sensing sensitivity of the optical metasurface resonant cavity sensor varies with the structural parameters, where the structural parameters include the resonant cavity length, the diameter, height and spacing of the dielectric metasurface.

[0065] Fig. 20 The figure is a flow chart of the preparation of a distributed Bragg reflector resonant cavity chip for comparison example.

[0066] Fig.21 This is a physical picture of a distributed Bragg reflector resonant cavity chip for comparison.

[0067] Fig. 22 The Q value of the distributed Bragg reflector resonant cavity and the surface sensor sensitivity vary with the cavity length.

[0068] Fig.23 When a 100nm aluminum oxide film is added to the inner surface of the distributed Bragg reflector resonant cavity, the resonance peaks of the three modes move.

[0069] Fig.24 These are the experimental results of the shift of the resonance peak wavelength relative to different COVID-19 Omicron BF.7 pseudovirus loads when a distributed Bragg reflector resonant cavity sensor is used to detect the COVID-19 Omicron BF.7 pseudovirus. DETAILED DESCRIPTION

[0070] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments, and the purpose and effects of the present invention will become more clear. 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.

[0071] Example 1

[0072] like Figure 1 As shown, the optical metasurface resonant cavity chip of this embodiment is prepared by the following steps:

[0073] Step (1): preparing a transparent substrate;

[0074] Step (2): 107 nm thick Ta2O5 and 150 nm thick SiO2 are alternately deposited 10 times on a transparent substrate to form a distributed Bragg reflector;

[0075] Step (3): depositing a Si3N4 film with a thickness of 180 nm on the surface of the distributed Bragg reflector;

[0076] Step (4): Spin-coat a layer of AR300-80 glue with a thickness of 400 nm, a layer of maN2405 glue with a thickness of 500 nm, and a layer of AR-PC 5090.02 glue with a thickness of 200 nm on the dielectric film.

[0077] Step (5): Draw an exposure pattern with a diameter of 200 nm and a pitch of 400 nm, and expose it through EBL with an exposure dose of 150 ; Then maD 525 was used for development for 180 s to obtain a photoresist pattern with a diameter of 200 nm;

[0078] Step (6): Etch with CHF3 and O2 for 150 s and The nanorods were soaked in acetone for no less than 20 min to remove the glue and obtain nanorods as the super surface;

[0079] Step (7): For subsequent biofunctionalization, a 5 nm layer of SiO2 was deposited on the surface of the device obtained in step (6).

[0080] Step (8): depositing a 1.5 μm thick Cu platform on both sides of the distributed Bragg reflector obtained in step (2) and the device obtained in step (7);

[0081] Step (9): Place the two parts obtained in step (8) at 350 The two materials are bonded together at a temperature of 10000 °C and a pressure of 220 kg to form an optical metasurface resonant cavity chip with a cavity length of 3 μm.

[0082] like Figure 2 As shown, the preparation of the liquid inlet end microfluidic component and the liquid outlet end microfluidic component of this embodiment includes:

[0083] Step (1): solidify the lower layer of PDMS in a clean flat-bottom container;

[0084] Step (2): placing the mold sheet on the lower layer of PDMS;

[0085] Step (3): curing the upper PDMS layer;

[0086] Step (4): taking out the formed whole piece of PDMS from a clean flat-bottom container;

[0087] Step (5): cutting to obtain two separate PDMS microfluidic components;

[0088] Step (6): Drill holes on the two PDMS components to establish an inlet and an outlet (6), and install a microfluidic connecting tube on the outlet to obtain an inlet microfluidic component and an outlet microfluidic component.

[0089] Step (7): Encapsulate the two ends of the optical metasurface resonant cavity chip in the liquid inlet microfluidic component and the liquid outlet microfluidic component respectively, and apply glue at the sealing part, so as to obtain an optical metasurface resonant cavity sensor, such as Figure 3 shown.

[0090] Figure 4 (a) shows a physical image of the optical metasurface resonant cavity chip, and (b) shows a cross-sectional scanning tunneling microscope (SEM) image and a surface SEM image. The microfluidic connection tube of the optical metasurface resonant cavity sensor is connected to the injection pump, and the sample solution is injected into the inlet of the optical metasurface resonant cavity sensor through the liquid inlet needle. Figure 5 The schematic diagram and actual picture of the introduction of sample solution into the optical metasurface resonant cavity sensor are shown.

[0091] In order to verify the performance of the optical metasurface resonant cavity sensor obtained in this embodiment, the optical metasurface resonant cavity chip with the above structural parameters is simulated to obtain the simulated transmission spectrum results, as shown in FIG. Figure 6 As shown by the blue dotted line in the figure. Afterwards, the optical properties of the optical metasurface resonant cavity sensor were experimentally characterized. Figure 6 The transmission spectrum of the experiment when the cavity is filled with PBS solution (such as the red solid line) is shown. It can be seen that under the above design, the optical metasurface resonant cavity sensor contains three resonant modes, namely the first mode with a wavelength of 828nm, the second mode at 894nm, and the third mode at 969nm. Their simulated Q values ​​are 4213, 5320 and 1078 respectively. The maximum experimental Q value of the second mode is 4140, and the average Q value is 3688.

[0092] At the same time, the electric field distribution of the three modes and the mode overlap factor (R value) are calculated, such as Figure 7 As shown. The calculation formula of R value is as follows:

[0093]

[0094] in, to represents the optical metasurface resonant cavity, including the upper and lower distributed Bragg reflectors, to Represents the range inside the optical metasurface resonant cavity. The work published in Volume 14 of Science Advances in 2024 (Hong Zhou, Dongxiao Li, Zhihao Ren, Cheng Xu, Lin-Fa Wang, Chengkuo Lee. Surface plasmons-phonons for mid-infrared hyperspectral imaging Science Advanced 2024, 10.) pointed out that the R value can reflect the ability of optical sensor devices to achieve high sensitivity. The three modes of the optical metasurface resonant cavity sensor prepared in this embodiment have different R values, which are 0.82, 0.86 and 0.83 respectively. Therefore, the second mode of the sensor of this embodiment has a higher sensing sensitivity. In order to further verify the sensing sensitivity of the sensor of this embodiment in the second mode, a 100nm Al2O3 layer was added to the inner surface of the optical metasurface resonant cavity through simulation to simulate the virus particles (diameter of 80-120nm) bound to the surface. The simulation results show that the second mode does have a larger resonance peak wavelength shift, that is, a higher sensitivity, such as Figure 8Therefore, the present invention recommends using the resonance mode with a wavelength of 850nm to 950nm as the sensing performance indicator of the optical metasurface resonant cavity sensor.

[0095] Then, the bulk refractive index sensing performance of the optical metasurface resonant cavity sensor was tested by passing deionized water and 5%, 10%, 15%, 20%, 25%, and 30% ethanol aqueous solutions into the cavity to adjust the refractive index in the cavity. We measured a total of 4 samples, and their peak position shifted with the change of the refractive index in the cavity. Fig. 9 The simulated value and quality factor of the simulated volume refractive index sensor sensitivity are 491.90 nm / RIU and 1824 RIU respectively. -1 , the experimental values ​​are 449.43 nm / RIU and 1669RIU -1 .

[0096] We compared the experimental bulk refractive index sensing performance of plasmon-based and dielectric-based micro-nano optical sensors in recent years. The experimental Q value of plasmon-based micro-nano optical sensors is usually less than 500, and the experimental quality factor is usually less than 300 RIU -1 The experimental Q value of dielectric-based micro-nano optical sensors is usually less than 1500, the experimental volume refractive index sensitivity is usually less than 350nm / RIU, and the experimental quality factor is usually less than 400 RIU -1 The experimental Q value of the optical metasurface resonant cavity sensor obtained in this embodiment is Fig.10 The maximum value is 4140, the average Q value is 3688, the refractive index sensitivity of the experimental body is 449.43 nm / RIU, and the quality factor is 1669 RIU -1 , which proves that the optical metasurface resonant cavity sensor proposed in the present invention achieves not only an ultra-high Q value, but also a higher volume refractive index sensing performance.

[0097] Finally, in order to verify the performance of the optical metasurface resonant cavity sensor in virus particle detection, a customized microfluidic channel was used to Fig.11 The steps shown are to conduct biological experiments:

[0098] Step (1): Use PBS buffer to soak the inner surface of the optical metasurface resonant cavity sensor.

[0099] Step (2): Pass the silica-binding protein solution for 20 minutes to modify the chip surface. The silica-binding protein has been shown to be able to be used for simple and efficient site-directed modification of antibodies on silica surfaces (Xixi Song, Ying Tao, Sumin Bian, Mohamad Sawan, Optical biosensing of monkeypox virus using novel recombinant silica-binding proteins for site-directed antibody immobilization. Journal of Pharmaceutical Analysis, 100995 (2024).).

[0100] Step (3): Bebtelovimab-specific monoclonal antibody was introduced for 20 min. This step fixed the monoclonal antibody on the sensor surface.

[0101] Step (4): Wash the surface of the optical metasurface resonant cavity sensor with PBS buffer for 10 min, and record the spectrum every 1 minute starting from the 5th minute to obtain 5 initial resonance peak wavelengths ( to ). Calculate the average value of the initial resonance peak wavelength and standard deviation .

[0102] Step (5): Introduce different concentrations of COVID-19 Omicron BF.7 pseudovirus solutions in sequence.

[0103] Step (6): Between each two concentrations of the novel coronavirus Omicron BF.7 pseudovirus solution, PBS was passed through to clean the optical metasurface resonant cavity sensor surface for 10 min, and the spectrum was recorded during the process to obtain the resonance peak wavelength corresponding to each novel coronavirus Omicron BF.7 pseudovirus solution concentration ( ), where n is the concentration group of the virus solution. Calculate the resonance peak wavelength shift , and obtain a value higher than of value, and the Corresponding virus solution concentration value ,Should This is the detection limit of the optical metasurface resonant cavity sensor.

[0104] The resonance peak wavelength shifts of five groups of optical metasurface resonant cavity sensors were measured when the pseudovirus load of COVID-19 Omicron BF.7 was 20, 40, 80, 150, 300, 600 and 1700 viral copies / mL, respectively. Fig.12 As shown. It can be seen that when the COVID-19 Omicron BF.7 pseudovirus load is higher than 150 viral copies / mL, the average resonance peak wavelength shift of the five groups of optical metasurface resonant cavity sensors is higher than By measuring the resonance peak wavelength shift corresponding to 80 and 150 viral copies / mL and Linear difference was performed and the detection limit of the metasurface resonant cavity sensor was found to be 119 viral copies / mL.

[0105] Embodiment 2~6

[0106] In this embodiment, we adjusted the Ta2O5 / SiO2 logarithm in the distributed Bragg reflector in the optical metasurface resonant cavity sensor (hereinafter referred to as "distributed Bragg reflector logarithm") to prove that the proposed optical metasurface resonant cavity sensor can maintain good sensing characteristics under a large change in the distributed Bragg reflector logarithm.

[0107] like Fig.13 As shown, the parameters of the dielectric metasurface structural unit (diameter: 200nm, height: 180nm, spacing: 400nm) are kept the same as in Example 1, and the number of Ta2O5 (107 nm) / SiO2 (150 nm) pairs is changed to 5, 6, 7, 8, 9 and 11 pairs to observe the changes in the bulk refractive index sensing sensitivity and quality factor of the optical metasurface resonant cavity sensor, as well as the changes in the surface sensing sensitivity and quality factor. As the number of distributed Bragg reflectors increases, the line width of the second mode gradually narrows ( Fig.13 ), the corresponding Q value becomes higher ( Fig.14 ), the transmission intensity becomes lower ( Fig.13 , Fig.14 As for the sensing performance, with the increase of the number of distributed Bragg reflectors, the bulk refractive index sensing sensitivity gradually decreases slowly, the surface sensing sensitivity has a certain fluctuation, and the bulk refractive index sensing quality factor and surface sensing quality factor both increase. Fig.15As shown. Examples 2 to 6 prove that when the number of distributed Bragg reflector pairs is greater than 5 pairs, the number of distributed Bragg reflector pairs will only affect the optical performance and sensing performance of the optical metasurface resonant cavity sensor, but will not change its nature as a high-performance sensor. However, since the transmission intensity shows a significant attenuation with the increase of the number of distributed Bragg reflector pairs, in order to increase the measurability of the spectrum, the number of distributed Bragg reflector pairs should not be too many; at the same time, in order to ensure an excellent Q value, the present invention recommends 10 pairs of distributed Bragg reflectors.

[0108] Embodiment 7-8

[0109] These two embodiments adjust the cavity length of the optical metasurface resonant cavity sensor to prove that the proposed optical metasurface resonant cavity sensor can achieve better sensing characteristics within a larger cavity length range.

[0110] In order to build a stable microfluidic system, the cavity length needs to be greater than 1 μm. The parameters of the dielectric metasurface structure unit in these two embodiments (diameter: 200 nm, height: 180 nm, spacing: 400 nm) are the same as those in Example 1, and the cavity lengths are 1 μm and 5 μm respectively. The sensing performance and optical performance of the optical metasurface resonant cavity sensor of the embodiment are calculated under the cavity lengths of 11 μm and 5 μm. Fig.16 As shown in Figure 2, when the cavity length is 1 μm, the optical metasurface resonant cavity sensor has two resonant modes, the bulk refractive index sensing sensitivity in the range of 1.33-1.35 RIU is 311.05 nm / RIU, and the bulk refractive index sensing quality factor is 1056 RIU -1 .like Fig.17 As shown in Figure 2, when the cavity length is 5 μm, the optical metasurface resonant cavity sensor has 6 resonant modes, the bulk refractive index sensing sensitivity in the range of 1.33-1.35 RIU is 543 nm / RIU, and the bulk refractive index sensing quality factor is 4793 RIU. -1 Through these two embodiments, it is proved that the cavity length only affects the mode number, optical and sensing performance of the optical metasurface resonant cavity sensor, but does not change its essence as a high-performance sensor.

[0111] Embodiments 9 to 26

[0112] By changing the diameter, spacing, height of the dielectric metasurface structural unit and changing a certain resonant cavity length, the optical and sensing performance of the optical metasurface resonant cavity sensor under more structural parameters is studied. The structural parameters of Examples 9-26 listed in Table 1, the number of distributed Bragg reflector pairs of these embodiments is 10 pairs, where the thicknesses of film 1 (Ta2O5 film) and film 2 (SiO2 film) are 107 nm and 150 nm, respectively. The simulation results show that the Q value of the optical metasurface resonant cavity sensor fluctuates less with the size of the dielectric metasurface, while the fluctuation with the change of the resonant cavity length is relatively more obvious, such as Fig.18 As shown. Overall, the Q value of the optical metasurface resonant cavity sensor has high robustness against changes in structural parameters.

[0113] As for the sensing performance, through simulation, Al2O3 with thickness t = 20nm, 40nm, 80nm and 120nm was added to the internal sensing surface of the optical metasurface resonant cavity sensor, and the surface sensitivity (m) was calculated by fitting according to the corresponding resonance peak wavelength shift:

[0114]

[0115] in is the shift of the resonance peak wavelength, obtained by simulation calculation. is the refractive index of the material added on the surface. Here, Al2O3 is used, with a refractive index of 1.63. is the refractive index of the cavity medium, PBS is used here, and the refractive index is 1.34. l is the attenuation coefficient, which is obtained by fitting formula 2. Thus, the changes of m in Examples 9 to 26 are obtained, as shown in Fig.19 As shown. Fig.19 It can be seen that m varies greatly with the structural parameters of the optical metasurface resonant cavity sensor, especially it is more sensitive to the change of cavity length. However, the above example shows that changing the structural parameters will only change the relative advantages and disadvantages of the sensing performance of the optical metasurface resonant cavity sensor, and will not change its nature as a high-performance sensor.

[0116] Table 1 Structural parameters of optical metasurface resonant cavity sensor of Examples 9-26

[0117]

[0118] Comparative Examples 1 to 2

[0119] In order to highlight the advantages of the optical metasurface resonant cavity sensor of the present invention, two distributed Bragg reflector chips without dielectric metasurfaces are bonded together to obtain a distributed Bragg reflector resonant cavity chip as a comparative example. The parameters of film 1 (Ta2O5: 107 nm) and film 2 (SiO2: 150 nm) are controlled, and the cavity length is adjusted to obtain comparative example 1 (cavity length 3.0 μm) and comparative example 2 (cavity length 3.2 μm). Fig. 20 As shown, the specific preparation steps of the comparative example are as follows:

[0120] Step (1): preparing a transparent substrate;

[0121] Step (2): 107 nm thick Ta2O5 and 150 nm thick SiO2 are alternately deposited 10 times on a transparent substrate to form a distributed Bragg reflector;

[0122] Step (3): depositing a 1.5 μm thick Cu platform on both sides of the distributed Bragg reflectors obtained in the two steps (2);

[0123] Step (4): Place the two parts obtained in step (3) at 350 The chips are bonded together at a temperature of 1.500°C and a pressure of 220 kg to form a distributed Bragg reflector resonant cavity chip with a cavity length of 3 μm. Fig.21 A physical picture of a distributed Bragg reflector resonant cavity chip is shown.

[0124] At the same time, the distributed Bragg reflector resonant cavity chips of comparative examples 1 and 2 are simulated, and Al2O3 with thickness t = 20nm, 40nm, 80nm and 120nm is added to the internal sensing surface of comparative examples 1 and 2, and the changes in the simulated surface sensitivity of the two comparative examples are obtained by fitting according to the corresponding resonance peak wavelength. Fig. 22 It can be seen that the surface sensitivity of the two comparative examples is much lower than that of Example 1 and Examples 9 to 26. At the same time, the calculation of Comparative Example 1 adds a 100nm Al2O3 layer on the inner surface of the distributed Bragg reflector resonant cavity, and the resonance peak wavelengths of the three resonance modes are shifted, such as Fig.23 The simulation results show that when the parameters of the resonant cavity (including the material and thickness of film one, the material and thickness of film two, and the cavity length) are the same, the resonance peak wavelength shift of the distributed Bragg reflector resonant cavity is significantly lower than that of the optical metasurface resonant cavity sensor.

[0125] Therefore, dielectric metasurfaces play an indispensable role in enhancing the sensitivity of resonant cavity sensors.

[0126] Adopt and Fig.11The inner surface of the sensor was biofunctionalized in the same way, and the resonance peak wavelength shifts of four groups of distributed Bragg resonant cavity sensors of two comparative examples were measured when the COVID-19 Omicron BF.7 pseudovirus loads were 20, 40, 80, 150, 300, 600 and 1700 viral copies / mL, respectively. Fig.24 As shown. It can be seen that when the COVID-19 Omicron BF.7 pseudovirus load is higher than 300 viral copies / mL, the average resonance peak wavelength offset of the four groups of distributed Bragg resonant cavity sensors is higher than By measuring the resonance peak wavelength shift corresponding to 150 and 300 viral copies / mL and Linear difference was performed and the detection limit of the metasurface resonant cavity sensor was 306 viralcopies / mL. This detection limit is much higher than that of the optical metasurface resonant cavity sensor, proving that the optical metasurface resonant cavity sensor is more suitable as a low detection limit virus particle detection sensor.

[0127] Those skilled in the art can understand that the above are only preferred embodiments of the invention and are not intended to limit the invention. Although the invention is described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions recorded in the above embodiments or replace some of the technical features with equivalents. Any modification, equivalent replacement, etc. made within the spirit and principle of the invention shall be included in the protection scope of the invention.

Claims

1. An optical metasurface resonant cavity sensor, characterized in that: It comprises an optical metasurface resonant cavity chip, and a liquid inlet end microfluidic component and a liquid outlet end microfluidic component; the two ends of the optical metasurface resonant cavity chip are respectively embedded in the liquid inlet end microfluidic component and the liquid outlet end microfluidic component; The microfluidic component at the liquid inlet end is provided with a liquid inlet, and the microfluidic component at the liquid outlet end is provided with a liquid outlet; The optical metasurface resonant cavity chip comprises, from bottom to top: A lower transparent substrate (1); Lower distributed Bragg reflector (2); A dielectric metasurface (3) built on the underlying distributed Bragg reflector (2); Metal platforms (10) built on both ends of the lower distributed Bragg reflector (2); upper distributed Bragg reflector (6); An upper transparent substrate (5); The upper distributed Bragg reflector (6) and the lower distributed Bragg reflector (2) are bonded together via the metal platform (10), forming a resonant cavity inside; the metal platform (10) is made of copper; The dielectric metasurface (3) is located in the resonant cavity and is composed of nanocolumns arranged in a two-dimensional periodic pattern; The lower distributed Bragg reflector (2) and the upper distributed Bragg reflector (6) are formed by alternately stacking thin films one and two in sequence.

2. The optical metasurface resonant cavity sensor according to claim 1, characterized in that: The nanorods are Si3N4 or SiO2.

3. The optical metasurface resonant cavity sensor according to claim 1, characterized in that: The first film is SiO2, and the second film is Ta2O5.

4. The optical metasurface resonant cavity sensor according to claim 1, characterized in that: The lower transparent substrate (1) and the upper transparent substrate (5) are both sapphire substrates.

5. The optical metasurface resonant cavity sensor according to claim 1, characterized in that: The cavity length of the resonant cavity is 1-5 μm.

6. The optical metasurface resonant cavity sensor according to claim 1, characterized in that: The nanopillars are cylindrical with a diameter of 180–220 nm, a height of 180–200 nm, and a spacing of 400–600 nm.

7. The optical metasurface resonant cavity sensor according to claim 1, characterized in that: The upper distributed Bragg reflector (6) and the lower distributed Bragg reflector (2) are both composed of SiO2 thin films and Ta2O5 thin films alternately stacked in sequence for no less than 5 times, and the product of the thickness and the refractive index of the SiO2 thin film is equal to the product of the thickness and the refractive index of the Ta2O5 thin film.

8. The optical metasurface resonant cavity sensor according to claim 7, characterized in that: The number of times the SiO2 film and the Ta2O5 film are alternately stacked in the upper distributed Bragg reflector (6) and the lower distributed Bragg reflector (2) is 10.

9. A method for preparing an optical metasurface resonant cavity sensor according to any one of claims 1 to 8, characterized in that: The steps include: Step 1: prepare the optical metasurface resonant cavity chip, the liquid inlet microfluidic component and the liquid outlet microfluidic component respectively; The preparation of the optical metasurface resonant cavity chip includes: (1) Alternately depositing thin film 1 and thin film 2 on a transparent substrate to form a distributed Bragg reflector; (2) depositing a dielectric film on the surface of the distributed Bragg reflector; (3) Spin coating EBL photoresist on the dielectric film, exposing, developing, and obtaining a pattern of the dielectric metasurface; (4) Etching and degumming to obtain nanorods; (5) depositing a metal film layer at both ends of the distributed Bragg reflector with nanopillars obtained in step (4) to obtain a lower distributed Bragg reflector modified with a dielectric metasurface; depositing a metal film layer at both ends of the distributed Bragg reflector obtained in step (1); (6) bonding the lower distributed Bragg reflector modified by the dielectric metasurface obtained in step (5) and the distributed Bragg reflector after the metal film layer is deposited to obtain an optical metasurface resonant cavity chip; The preparation of the liquid inlet end microfluidic component and the liquid outlet end microfluidic component includes: (1) Solidify the lower layer of PDMS in a flat-bottom container; (2) placing a mold sheet on the lower PDMS layer, wherein the thickness of the mold sheet is equal to twice the thickness of the optical metasurface resonant cavity chip, and the dimension in the direction perpendicular to the plane composed of the thickness direction and the liquid flow direction is equal to the width of the optical metasurface resonant cavity chip; (3) curing the upper PDMS layer on the mold sheet and the lower PDMS layer in step (2) to obtain a PDMS module with upper and lower parts integrated; (4) Take out the PDMS module from the flat-bottom container and cut it in the mold sheet to separate it into two parts; (5) punching a hole in one part of the PDMS to form a liquid inlet, thereby obtaining a liquid inlet end microfluidic component; punching a hole in another part of the PDMS to form a liquid outlet, thereby obtaining a liquid outlet end microfluidic component; Step 2: Encapsulate the two ends of the optical metasurface resonant cavity chip in a liquid inlet microfluidic component and a liquid outlet microfluidic component respectively to form an optical metasurface resonant cavity sensor.

Images