Stepped microfluidic-metamaterial integrated terahertz sensor, preparation method and use method

Abstract

The invention provides a stepped micro-fluidic-metamaterial integrated terahertz sensor, a preparation method and a use method. The stepped micro-fluidic-metamaterial integrated terahertz sensor comprises a metal film (1), detected liquid, a stepped micro-channel substrate (2) and a polyimide film (6), a step-shaped groove is formed in one surface of the step-shaped micro-channel substrate (2); the step-shaped micro-channel substrate (2) is provided with a micro-channel injection channel (5); the detected liquid is injected into the stepped micro-channel substrate (2) through the micro-channel injection channel (5); by applying the technical scheme, the detection limit can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of terahertz sensors, in particular to a stepped microfluidic-metamaterial integrated terahertz sensor, a preparation method and a usage method thereof. Background Art

[0002] A terahertz sensor is a detection and sensing device based on terahertz waves (frequency range: 0.1 - 10 THz, wavelength range: 30 - 3000 μm), which utilizes the characteristics of the interaction between terahertz waves and substances to achieve the detection and analysis of target substances. Terahertz biosensors are a research hotspot in terahertz functional devices. Through the sensor, not only can samples with different components be detected, but also the chemical reactions occurring between biomolecules and drugs can be monitored. Therefore, the development of different types of terahertz biosensors has important research value and significance.

[0003] However, the existing technologies have the following key problems: insufficient sensitivity, as the terahertz wavelength is relatively long, it is difficult to achieve high-precision detection of micron-scale samples or trace substances. Liquid environment interference, water molecules strongly absorb in the terahertz band, resulting in limited detection of the activity of biomolecules in liquids. Existing solutions rely on ultra-thin liquid layers or vacuum environments, with poor practicability and high costs. Penetration depth limitation, insufficient penetration ability for samples behind water-containing obstacles, and traditional sensors cannot effectively enhance the interaction between terahertz waves and samples. Process complexity and cost, relying on complex processing techniques (such as lithography technology) and high-cost equipment, it is difficult to meet the requirements of rapid and low-cost detection.

[0004] In recent years, the combination of metamaterials and microfluidic technology has provided new ideas for terahertz sensing. By designing metamaterial structures, electromagnetic field local enhancement is achieved to improve sensing sensitivity. Using microfluidics to precisely control the liquid thickness (micron scale) reduces water absorption interference. However, the existing integration solutions still have the following defects: the processing techniques of metamaterials and microfluidic channels are separated, resulting in poor structural matching; no dynamic detection mechanism is designed for the change of liquid dielectric properties; there is a lack of low-cost and high-precision integrated manufacturing methods. In the future, it is necessary to further optimize the structure of metamaterials, develop more new technologies similar to microfluidic channels, and propose updated data processing algorithms to more accurately describe the terahertz spectral characteristics of substances. In addition, it is necessary to further reduce the cost of terahertz technology and improve the detection limit, while traditional terahertz sensors cannot meet the requirements, and new terahertz sensors are needed. Summary of the Invention In view of this, the purpose of the present invention is to provide a stepped microfluidic-metamaterial integrated terahertz sensor, a preparation method and a usage method thereof, which achieve an improvement in the detection limit.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A stepped microfluidic-metamaterial integrated terahertz sensor, comprising a metal thin film (1), a liquid to be measured, a stepped microchannel substrate (2), and a polyimide thin film (6); one side of the stepped microchannel substrate (2) is provided with stepped grooves; the stepped microchannel substrate (2) is provided with a microchannel injection channel (5); the liquid to be measured is injected into the stepped microchannel substrate (2) through the microchannel injection channel (5).

[0006] The present invention also provides a preparation method of a stepped microfluidic-metamaterial integrated terahertz sensor, and prepares the above-mentioned stepped microfluidic-metamaterial integrated terahertz sensor; the metal thin film (1) is used as an electromagnetic field enhancement substrate, and the stepped microchannel substrate (2) realizes sub-micron three-dimensional channel forming through femtosecond laser technology, and the liquid to be measured is injected into the microchannel injection channel (5) by using a solution dropper (3) with a precision micro-injection pump.

[0007] In a preferred embodiment, the solution dropper (3) with a precision micro-injection pump injects the liquid to be measured into the stepped microchannel substrate (2) through the self-sealing sampling port of the metal thin film (1), and the injection angle is kept at 45° to match the hydrodynamic characteristics of the stepped microchannel substrate (2), and no air bubbles are ensured during the injection process.

[0008] The present invention provides a usage method of a stepped microfluidic-metamaterial integrated terahertz sensor, and adopts the above-mentioned stepped microfluidic-metamaterial integrated terahertz sensor; first, place the sensor filled with the liquid to be measured in a sample chamber with a nitrogen atmosphere, and adjust it to the focal plane of the terahertz beam through a three-dimensional precision displacement stage; use a femtosecond laser to excite a photoconductive antenna to generate a terahertz pulse with a pulse width <100 fs, which is collimated by a parabolic mirror and vertically incident on the metamaterial resonant unit; the transmitted signal is received by a ZnTe crystal electro-optic sampling detector, and each sampling point accumulates multiple scans to improve the signal-to-noise ratio; for the stepped channel design, the system automatically performs three-dimensional scanning to obtain multi-dimensional data of microcavities at different depths.

[0009] Compared with the prior art, the present invention has the following beneficial effects: By innovatively introducing the solution thickness as a detection parameter, it combines the electromagnetic field localization characteristics of the gradient-thickness microcavity and the metamaterial resonant unit. This device uses femtosecond laser direct writing technology to integrally integrate a metal thin film substrate, a three-dimensional microchannel, and a metamaterial resonant structure, and synchronously extracts multi-dimensional parameters such as frequency shift, quality factor, and transmission amplitude of liquid layers at multiple depths through a terahertz time-domain spectroscopy system. By changing the dielectric environment caused by the analyte, the amplitude, frequency, or phase can be correspondingly changed, and then according to the change situation, qualitative or quantitative analysis of the analyte is carried out, realizing the identification of substances such as biomolecules and chemical isomers. Description of the Drawings

[0010] Figure 1 Schematic diagram (I) of the stepped microfluidic channel substrate (2) according to a preferred embodiment of the present invention; Figure 2 Schematic diagram (II) of the stepped microfluidic channel substrate (2) according to a preferred embodiment of the present invention; Figure 3 Schematic diagram of the integration process of the stepped microfluidic - metamaterial terahertz device according to a preferred embodiment of the present invention; Figure 4 Schematic diagram of the stepped microfluidic - metamaterial terahertz device according to a preferred embodiment of the present invention; Figure 5 Explosion schematic diagram of the stepped microfluidic - metamaterial terahertz device according to a preferred embodiment of the present invention; Figure 6 Analysis diagram of the usage results of the stepped microfluidic - metamaterial terahertz device according to a preferred embodiment of the present invention; Figure 7 Flow chart of the usage process of the stepped microfluidic - metamaterial terahertz device according to a preferred embodiment of the present invention. Detailed implementation manners

[0011] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0012] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0013] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present application; as used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0014] A stepped microfluidic - metamaterial integrated terahertz sensor 4, refer to Figures 1-7, a multi-dimensional scan is performed on the solution in the gradient-thickness microcavity through a terahertz time-domain spectroscopy system (THz-TDS) to extract characteristic parameters such as frequency shift, change in quality factor, and transmission amplitude. Combining with finite element simulation, precise identification of trace substances is achieved, especially suitable for substances with large dielectric constant differences but similar other structures. This design introduces thickness as a new parameter for detecting substances while maintaining the solution environment of organisms. Compared with existing terahertz integrated devices, a metamaterial with a specific resonance response is combined with a stepped microfluidic chip. The present invention will utilize femtosecond laser direct writing to complete the processing of the stepped microchannel, fabricate the designed sensor, and integrate it. It is verified that different solutions can be distinguished by changing the thickness of the solution to affect the movement of the terahertz spectrum due to different dielectric constants.

[0015] The sensor 4 includes a metal thin film 1, a measured liquid, a stepped microchannel substrate 2, and a polyimide thin film 6; one side of the stepped microchannel substrate 2 is provided with stepped grooves; the stepped microchannel substrate 2 is provided with a microchannel injection channel 5; the measured liquid is injected into the stepped microchannel substrate 2 through the microchannel injection channel 5. The metal thin film 1 serves as an electromagnetic field enhancement substrate, and the stepped microchannel substrate 2 realizes sub-micron three-dimensional channel forming through femtosecond laser technology.

[0016] In the liquid injection process, the operator injects a small amount of the measured solution into the microchannel through the self-sealing sampling port of the metal thin film by a high-precision injection pump, and the injection angle is maintained at 45° to match the hydrodynamic characteristics of the stepped flow channel, ensuring no air bubble perfusion during the injection process.

[0017] The measurement process adopts a cooperative working mode of a terahertz time-domain spectroscopy system and a microfluidic device: First, the device with the solution perfusion completed is placed in the sample chamber with a nitrogen atmosphere and adjusted to the focal plane of the terahertz beam through a three-dimensional precision displacement stage. The system uses a femtosecond laser to excite a photoconductive antenna to generate a terahertz pulse with a pulse width <100 fs, which is collimated by a parabolic mirror and vertically incident on the metamaterial resonant unit. The transmitted signal is received by a ZnTe crystal electro-optic sampling detector, and each sampling point is scanned multiple times cumulatively to improve the signal-to-noise ratio. For the stepped flow channel design, the system automatically performs a three-dimensional scan to obtain multi-dimensional data of microcavities at different depths.

[0018] After packaging is completed, the data processing adopts a time-frequency domain joint analysis method: After the original time-domain waveform is filtered, it is converted to the frequency domain through a fast Fourier transform (FFT) to extract the effective THz frequency band. Based on the metamaterial resonance model of finite element simulation, the system automatically matches three characteristic parameters of resonance frequency shift, change in quality factor, and change in transmission amplitude in the experimental data. Through the established concentration-frequency shift calibration curve, the dielectric characteristics, concentration distribution, and molecular conformation information of the measured solution are analyzed.

[0019] The integrated stepped microfluidic-metamaterial terahertz sensor is based on the thickness change mechanism. According to the principle that different solutions have different dielectric constants and changing its thickness will result in different spectral shift distances, it can analyze substances with different dielectric constants but similar terahertz fingerprint spectra.

[0020] Example 1: Select the most commonly used existing materials: metal thin film 1 (aluminum film) and stepped microchannel substrate 2 (ultra-clear glass) for sample trial processing. Fabricate the metamaterial by femtosecond laser processing platform on the aluminum film, and then bond the metal grating to the polyimide film 6 with resin glue. At the same time, fabricate the microchannel on the material by femtosecond laser, and inject sufficient measured liquid into the injection channel 5 of the processed microchannel with a precision micro-injection pump. To prevent data deviation during detection caused by insufficient solution, the metamaterial is bonded to the polyimide film with resin glue and then leveled and encapsulated by the way of a cover glass as Figures 4-5 shown.

[0021] After the encapsulation is completed, verify it with a terahertz time-domain spectroscopy system. By moving the stepped microfluidic terahertz device and performing time-domain detection in the measured liquid regions with different thicknesses, the spectral red-shift phenomenon can be observed, and the larger the dielectric constant, the larger the offset, and the smaller the dielectric constant, the smaller the offset as Figure 6 shown.

[0022] Those of ordinary skill in the art can understand that the above are only preferred examples for designing and manufacturing the stepped microfluidic-metamaterial integrated terahertz sensor, and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, for those skilled in the art, they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall be included within the protection scope of the invention.

Claims

1. A stepped microfluidic-metamaterial integrated terahertz sensor, characterized in that: The invention comprises a metal film (1), a liquid to be tested, a stepped microfluidic substrate (2) and a polyimide film (6); one side of the stepped microfluidic substrate (2) is provided with a stepped groove; the stepped microfluidic substrate (2) is provided with a microfluidic injection channel (5); the liquid to be tested is injected into the stepped microfluidic substrate (2) through the microfluidic injection channel (5).

2. A method for preparing a stepped microfluidic-metamaterial integrated terahertz sensor, characterized in that: A stepped microfluidic-metamaterial integrated terahertz sensor as claimed in claim 1 is prepared; a metal film (1) is used as an electromagnetic field enhancement substrate, a stepped microfluidic substrate (2) is formed into a submicron-level three-dimensional channel by femtosecond laser technology, and a solution dropper (3) with a precision micro-injection pump is used to inject the measured liquid into the microfluidic injection channel (5).

3. The method for preparing a stepped microfluidic-metamaterial integrated terahertz sensor according to claim 2, characterized in that: A solution dropper (3) with a precision micro-injection pump injects the test liquid into the stepped microfluidic substrate (2) through the self-sealing injection port of the metal film (1). The injection angle is maintained at 45° to match the fluid dynamics characteristics of the stepped microfluidic substrate (2), and bubble-free perfusion is ensured during the injection process.

4. A method for using a stepped microfluidic-metamaterial integrated terahertz sensor, characterized in that: A stepped microfluidic-metamaterial integrated terahertz sensor as described in claim 1 is used; firstly, the sensor filled with the test liquid is placed in a sample chamber in a nitrogen atmosphere, and adjusted to the focal plane of the terahertz beam by a three-dimensional precision translation stage; a femtosecond laser is used to excite the photoconductive antenna to generate a terahertz pulse with a pulse width of <100fs, which is collimated by a parabolic mirror and vertically incident on the metamaterial resonance unit; The transmission signal is received by a ZnTe crystal electro-optical sampling detector, and each sampling point accumulates multiple scans to improve the signal-to-noise ratio. For the stepped flow channel design, the system automatically performs three-dimensional scanning to obtain multi-dimensional data of microcavities at different depths.

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