Multifunctional terahertz biosensor based on multi-band enhanced metasurface

Abstract

The utility model provides a multifunctional terahertz biosensor based on a multi-band enhanced metasurface, and relates to the field of terahertz wave detection. According to the self-similar periodic metal micro-antenna arrays, each micro-antenna array comprises a plurality of antenna structure units which are different in length and are arranged in parallel, the antenna structure units in the single micro-antenna array have the same specification, and the micro-antenna arrays are provided with different antenna structure units; the terahertz generating module is used for enabling a terahertz light beam which is polarized in an incident manner and is parallel to the long axis of the antenna to serve as exciting light, enabling the terahertz light beam to obliquely enter the bottom of the substrate from the bottom, and enabling the upper surface of the substrate to fall on a light beam focal plane; the terahertz signal detection module is used for receiving the reflected terahertz signal so as to reflect the subtle change of the metasurface covering the object to be detected in a terahertz reflection spectrum; and the signal analysis module is used for processing the frequency domain signal based on a deep neural network. And high-sensitivity detection can be carried out on the characteristics of biomolecules and polymers.

Description

Technical Field

[0001] The utility model relates to the technical field of terahertz wave detection, and in particular to a multifunctional terahertz biosensor based on a multi-band enhanced metasurface. Background Art

[0002] Spectroscopic methods, such as infrared (IR) absorption, Raman scattering, and circular dichroism (CD), are powerful label-free tools for detecting biomolecules and extracting complex chemical information in real time and noninvasively. The terahertz (THz) spectral range is crucial for these detection methods because it covers a wide range of rotational and collective vibrational frequencies of condensed matter and biomolecules, enabling the specific identification of biomolecules with distinct chemical properties. Importantly, all building blocks of life, such as amino acids, proteins, and nucleic acids, exhibit distinct and unique fingerprints in this spectral range, with their spectra varying in frequency, position, intensity, and shape. Notably, in bodily fluids, the oscillation modes of the analyte molecules are subject to multiple environmental influences, such as van der Waals forces and hydrogen bonding. Using conventional attenuated total reflectance (ATR) and surface plasmon resonance (SPR) detection techniques for such highly significant and widespread phenomena is extremely challenging. Using sensing effects on net analyte mass and refractive index to analyze the contributions of individual analytes is difficult compared to separating them from the overall system signal. For common biological processes involving mixed systems of multiple elements, distinguishing and monitoring the individual components of this heterogeneous mixture is a central goal of biosensing. Typically, different biomolecules have different optical responses in the terahertz range. Furthermore, in real-world scenarios, they exist as mixtures, which poses an additional challenge in distinguishing them. Therefore, how to distinguish different biomolecular species in trace amounts of the substance to be detected (heterogeneous mixtures) becomes a technical problem that needs to be solved. Utility Model Content

[0003] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art or related art, and provides a multifunctional terahertz biosensor based on a multi-band enhanced metasurface, which can detect biomolecules and polymer characteristics with high sensitivity.

[0004] The utility model is realized by the following technical solutions: a multifunctional terahertz biosensor based on a multi-band enhanced metasurface, comprising: a substrate made of a light-transmitting material with low absorption rate;

[0005] A self-similar periodic metal micro-antenna array is integrated on the upper surface of the substrate to form a multi-band enhanced metasurface. The self-similar periodic micro-antenna array includes multiple micro-antenna arrays, each of which includes multiple antenna structure units of different lengths and arranged in parallel. The antenna structure units in a single micro-antenna array have the same specifications, and each micro-antenna array has different antenna structure units; a terahertz generation module uses a terahertz beam with an incident polarization parallel to the long axis of the antenna as excitation light, which is incident at an angle from the bottom to the bottom of the substrate and makes the upper surface of the substrate fall on the focal plane of the beam; a terahertz signal detection module receives the reflected terahertz signal to reflect the subtle changes of the metasurface covered with the object to be detected in the terahertz reflection spectrum to generate a real-time signal; a signal analysis module processes the frequency domain signal based on a deep neural network to identify and quantitatively detect biological molecules.

[0006] In this technological solution, a self-similar microantenna array with discrete asymmetry is introduced, which facilitates the simultaneous detection of different molecular vibrational fingerprints at multiple spectral points. A terahertz beam polarized parallel to the x-direction is used as the incident light, incident obliquely onto the metasensor from the bottom, with the beam focus aligned with the upper surface. Subtle changes in the analyte covering the metasensor surface are reflected in the terahertz reflectance spectrum, enabling the identification and quantitative detection of biomolecules. The temporal evolution of the absorption fingerprint can be independently tracked to distinguish different biomolecular species. A multi-resonant metasurface composed of a periodically arranged microantenna array is employed to enhance the near-field intensity of multiple characteristic fingerprints. The use of incident light from a backward direction ensures easy operation of the enhanced sensing platform and minimizes the detrimental effects of water absorption on THz signal penetration through the water layer. This allows for in situ, real-time resolution of the dynamics of the L-glutamate (L-Glu) absorption fingerprint during water evaporation. The collection of subtle, real-time signals from the reflectance method allows the construction of a deep neural network capable of accurately discriminating between simultaneously present biomolecules without the use of any external labels.

[0007] According to the multifunctional terahertz biosensor based on the multi-band enhanced metasurface provided by the present invention, preferably, the substrate material is polymethylpentene TPX.

[0008] According to the multifunctional terahertz biosensor based on the multi-band enhanced metasurface provided by the present invention, preferably, the period of a single antenna structure unit along the long axis direction of the antenna is 200 μm, and the period along the direction perpendicular to the long axis is 50 μm.

[0009] According to the multifunctional terahertz biosensor based on the multi-band enhanced metasurface provided by the present invention, preferably, the width of the micro-antenna in the antenna structure unit is 5 μm, and the gap between the micro-antennas is 5 μm.

[0010] According to the multifunctional terahertz biosensor based on the multi-band enhanced metasurface provided by the present invention, preferably, the lengths of the multiple micro-antennas in the antenna structure unit decrease successively.

[0011] According to the multifunctional terahertz biosensor based on the multi-band enhanced metasurface provided by the present invention, preferably, there are 10 micro-antenna arrays, corresponding to 10 groups of antenna structure units of different specifications, the width of each micro-antenna is 5μm, and the interval gap is 5μm. In each group of structures, only the length parameters of multiple micro-antennas are changed.

[0012] According to the multifunctional terahertz biosensor based on the multi-band enhanced metasurface provided by the present invention, preferably, the deep neural network analysis adopts the principal component analysis method to classify different substances with different mixing ratios, and combines the multimodal deep neural network to establish a mixed analyte ratio prediction regression model to output the concentration prediction of all components in the mixture.

[0013] The beneficial effects achieved by the present invention include at least the following: Existing technologies are based on homogeneous arrays composed of multiple resonant elements. However, for the purpose of multi-band sensing, the resonances in such systems typically reduce the excitation efficiency level of higher-order modes associated with smaller resonant feature sizes, resulting in a degradation of the enhanced terahertz absorption performance at these resonant frequencies. In addition, electromagnetic coupling between different resonant modes and feature sizes hinders direct spectral tuning. In addition, the complex structure will increase the design and experimental processing costs. The present invention overcomes these three major limitations by designing multiple asymmetric dipole antenna array structures within a single unit to allocate different resonant frequencies accordingly. Biomolecules and polymer features can be detected with high sensitivity, and applications include biosensing and environmental monitoring. The present invention overcomes the challenges associated with experimental complexity and training data availability by combining deep learning technology with enhanced sensing using reflection-enhanced plasmonics methods. This represents a dramatic and transformative advance in high-sensor identification of biosensors in complex bioanalysis and mixed drug applications, providing new insights into neurotransmitter conduction or passage processes in basic research. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A structural schematic diagram of a multifunctional terahertz biosensor based on a multi-band enhanced metasurface according to an embodiment of the present utility model is shown.

[0015] Figure 2 A schematic diagram of the structural unit of a multifunctional terahertz biosensor based on a multi-band enhanced metasurface according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0016] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] Conventional terahertz (THz) detection technologies face several challenges in achieving high-sensitivity spectroscopic sensing of trace analytes. These challenges include increasing the optical absorption of molecules in specific fingerprint bands, miniaturizing the device footprint, and mitigating the stronger absorption of polar solutions. Broadband-enhanced THz spectroscopy offers a potential solution to overcome some of these obstacles. Metasurfaces excel at arbitrarily tuning the spectral response and optical localization of nanophotonic devices, as well as manipulating light at the micro- and nanoscales. Engineered metasurfaces can enhance the operating band and generate intense, highly confined electromagnetic field hotspots, enabling robust interactions with neighboring analytes, making them promising candidates for biosensing applications. However, due to low-Q resonances, THz metasurface-based biosensors remain far from satisfactory. Recently, bound states in continuum media (BICs) have emerged as a powerful tool for achieving high-Q resonances. BICs correspond to dark eigenstates that exist in the continuum spectrum but are fully decoupled from the external environment. For practical applications, BICs must be converted into quasi-BICs (QBICs, continuum quasi-bound states whose eigenacoustic fields possess chirality) with finite and high Q factors. It is worth noting that high-Q QBICs are always accompanied by extreme field enhancements, and therefore hold great promise for enhancing light-matter interactions. Based on the aforementioned principles, the present invention discloses a label-free, multifunctional terahertz plasmon biosensing platform based on multiple quasi-bound states (multiple QBICs) in a continuum.

[0018] like Figure 1 As shown, one embodiment of the present invention discloses a multifunctional terahertz biosensor based on a multi-band enhanced metasurface, comprising: a substrate 1, a self-similar periodic metal micro-antenna array 2, a substance to be detected 3, a terahertz generation module 4, and a terahertz signal detection module 5. The self-similar periodic metal micro-antenna array is integrated on the upper surface of the substrate to form a multi-band enhanced metasurface. The self-similar periodic micro-antenna array includes multiple micro-antenna arrays, each of which includes multiple antenna structure units of different lengths and arranged in parallel. The antenna structure units in a single micro-antenna array have the same specifications, and each micro-antenna array has different antenna structure units. The terahertz generation module uses a terahertz beam with an incident polarization parallel to the long axis of the antenna as excitation light, which is incident obliquely from the bottom to the bottom of the substrate and causes the upper surface of the substrate to fall on the focal plane of the beam. A multi-resonant metasurface composed of periodically arranged micro-antenna arrays is used to enhance the near-field intensity of multiple characteristic fingerprints. The terahertz signal detection module receives the reflected terahertz signal to reflect subtle changes in the metasurface covering the substance to be detected in the terahertz reflection spectrum, generating a real-time signal.

[0019] In this example, a finely pixelated, multiband plasmonic antenna array is integrated onto a substrate composed of low-absorption polymethylpentene (TPX) for broad resonance-enhanced molecule-specific detection. Compared to conventional dielectric-based integrated devices, this compact metasurface-based device exhibits a significantly reduced footprint and broadband performance. Incident light originates from the backside of the chip and is subsequently reflected back to the detector. A significant advantage of this approach is its ability to minimize the detrimental effects of water absorption on the terahertz signal. By effectively utilizing the strong near-field generated by the metallic microantenna, the weak vibrational fingerprint signals emitted by nanoscale analytes can be amplified.

[0020] like Figure 2 The individual structural units shown are along P x The period p of the direction is 200 μm, along P y The period of the direction is 50μm. Four parallel micro-antennas with lengths of L1, L2, L3 and L4 are symmetrically connected to the center of the structural unit. The width of each antenna is d = 5μm and a small gap g = 5μm is separated. Figure 1 In the ten groups of micro-antenna structures shown, the length parameters of L1, L2, L3, and L4 are changed in each group of structures, while other parameters remain unchanged, that is, the length parameters of L1, L2, L3, and L4 are: L1 = 92μm, L2 = 74μm, L3 = 56μm, L4 = 47μm; L1 = 94μm, L2 = 76μm, L3 = 58μm, L4 = 48μm; L1 = 96μm, L2 = 78μm, L3 = 60μm, L4 = 49μm; L1 = 98μm, L2 = 80μm, L3 = 62μm, L4 = 50μm; L1 = 100μm, L2=82μm, L3=64μm, L4=51μm; L1=102μm, L2=84μm, L3=66μm, L4=52μm; L1=104μm, L2=86μm, L3=68μm, L4=53μm; L 1=106μm, L2=88μm, L3=70μm, L4=54μm; L1=108μm, L2=90μm, L3=72μm, L4=55μm; L1=110μm, L2=92μm, L3=74μm, L4=56μm.

[0021] According to the above embodiment, the system preferably further includes a signal analysis module that processes frequency-domain signals based on a deep neural network to identify and quantitatively detect biomolecules. The deep neural network analysis utilizes principal component analysis to classify different substances at different mixture ratios. In combination with a multimodal deep neural network, a regression model for predicting the proportion of mixed analytes is established, outputting predicted concentrations of all components in the mixture.

[0022] In this example, a deep neural network was constructed from subtle, real-time signals collected by the reflectometry method, which was able to accurately distinguish between simultaneously present biomolecules without the use of any external labels. By combining deep learning techniques with enhanced sensing using reflectometry-enhanced plasmonics, challenges associated with experimental complexity and training data availability were overcome.

[0023] According to another embodiment of the present invention, a method for fabricating a multifunctional terahertz biosensor chip structure based on a multi-band enhanced metasurface is also disclosed: a gold film is deposited on a 2mm thick polymethylpentene (TPX) substrate using radio frequency magnetron sputtering; the metal structure is etched using step-and-repeat lithography and ion beam etching. This design can excite multiple QBIC resonances and fully overlap with the vibrations of the characteristic absorption bands I and II of the neurotransmitters L-Glu and γ-aminobutyric acid (GABA). TPX was chosen as the substrate material because it has relatively high transmittance for terahertz waves and other compelling optical properties, making it a commonly used substrate material for metasurfaces.

[0024] As can be seen from the above embodiments, achieving resonance at a specific frequency in the present invention may require more complex parameter settings. Nevertheless, compared to the complex metamaterial structures used in the prior art, this method is easier to design and manufacture, especially for implementing multispectral devices. The resonance position can be adjusted as needed by adjusting the length parameters of the designed structure. In summary, the number of resonances and the center frequency of the resonance peak in this sensor can be adjusted by varying the number and length of structures in each structural unit. This provides advantages for the research of multi-band blocking filters, sensors, and other multispectral devices with simple structures and flexible adjustability.

[0025] The multifunctional terahertz biosensor based on a multi-band enhanced metasurface disclosed in the above-mentioned embodiment of the present invention exhibits sharp resonances caused by interference between subradiant and superradiant plasma resonances, capable of identifying molecular characteristic absorptions and analyzing the composition of mixtures. The designed sensor uses a multi-resonant metasurface composed of a microantenna array to achieve multiple resonances by introducing structural asymmetry in the microstructure. The frequency of the subradiant resonance can be precisely determined and matched to the vibrational fingerprint of the molecule. This configuration is cleverly designed to enhance biosensing capabilities and facilitate the detection of molecular absorption features at multiple spectral points through strong near-field coupling. This chemically specific nanoplasmonic approach allows for precise resolution of absorption fingerprints, eliminating the need for frequency scanning or mechanical movement.

[0026] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A multifunctional terahertz biosensor based on a multi-band enhanced metasurface, characterized in that: include: a substrate made of a light-transmitting material with low absorption; A self-similar periodic metal micro-antenna array is integrated on the upper surface of the substrate to form a multi-band enhanced metasurface, wherein the self-similar periodic micro-antenna array includes multiple micro-antenna arrays, each of which includes multiple antenna structure units of different lengths and arranged in parallel. The antenna structure units in a single micro-antenna array have the same specifications, and each micro-antenna array has different antenna structure units. A terahertz generating module is used to generate a terahertz beam, wherein the terahertz beam with incident polarization parallel to the long axis of the antenna is used as excitation light, is incident obliquely from the bottom to the bottom of the substrate, and the upper surface of the substrate falls on the focal plane of the beam; A terahertz signal detection module is used to receive and detect the reflected terahertz signal, so as to reflect the subtle changes of the metasurface covered with the object to be detected in the terahertz reflection spectrum and generate a real-time signal; The signal analysis module is used to receive the detection result of the terahertz signal detection module and process the frequency domain signal based on a deep neural network.

2. The multifunctional terahertz biosensor based on the multi-band enhanced metasurface according to claim 1, characterized in that: The material of the substrate is polymethylpentene TPX.

3. The multifunctional terahertz biosensor based on the multi-band enhanced metasurface according to claim 1, characterized in that: The period of a single antenna structure unit along the long axis of the antenna is 200 μm, and the period along the direction perpendicular to the long axis is 50 μm.

4. The multifunctional terahertz biosensor based on the multi-band enhanced metasurface according to claim 3, characterized in that: The width of the micro-antennas in the antenna structure unit is 5 μm, and the gap between the micro-antennas is 5 μm.

5. The multifunctional terahertz biosensor based on the multi-band enhanced metasurface according to claim 1, characterized in that: The lengths of the multiple micro-antennas in the antenna structure unit decrease in sequence.

6. The multifunctional terahertz biosensor based on the multi-band enhanced metasurface according to claim 1, characterized in that: There are 10 micro-antenna arrays in total, corresponding to 10 groups of antenna structure units of different specifications. The width of each micro-antenna is 5 μm, and the interval gap is 5 μm. In each group of structures, only the length parameters of multiple micro-antennas are changed.

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