System and method for testing terahertz characteristic spectrum of sample based on closed microflow waveguide channel

Abstract

The invention belongs to the technical field of terahertz biological sample sensing detection and analysis, and relates to a system and a method for testing a terahertz characteristic spectrum of a sample based on a closed microflow waveguide channel, in particular to a method for testing the characteristic spectrum of a liquid biological sample in a terahertz frequency band. The method comprises the following steps: firstly, carrying out an experiment by using a blank solution without a biological sample, and measuring the signal response of the blank solution in a terahertz wave band to obtain a corresponding background characteristic spectrum; then sample liquid containing the biological sample is conveyed into the waveguide, a total characteristic spectrum containing the biological sample and blank liquid is obtained, the measured change of the total characteristic spectrum relative to a background characteristic spectrum is biological sample characteristic information, and a net characteristic spectrum of the biological sample is obtained through calculation by means of a difference algorithm or a neural network or other methods; the terahertz characteristic spectrum is the terahertz characteristic spectrum of the biological sample. The invention provides a high-efficiency, stable and low-cost biological sample terahertz detection scheme for biological detection by using terahertz waves, and has the advantages of high feasibility, multiple method variety selections and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz biosample sensing detection and analysis, and particularly relates to a system and method for testing the terahertz characteristic spectrum of a sample based on a closed microfluidic waveguide channel, especially a method for testing the characteristic spectrum of a liquid biosample in the terahertz frequency band (0.1 - 1 THz). Background Art

[0002] In recent years, with the continuous in - depth research on terahertz technology, it has been found that terahertz radiation has unique properties suitable for biomedical research. Since the frequency range of terahertz waves is of the same order of magnitude as the rotation and vibration frequencies of biological samples such as cells and protein molecules, when terahertz signals propagate through biomolecules, each biomolecule will generate its unique spectral vibration characteristics in the terahertz frequency range, and the terahertz characteristic fingerprint spectrum of biological samples can be analyzed based on this. And the energy of terahertz waves is relatively low, without harmful ionization and radiation damage to biological tissues. Therefore, in biomedical research, it is very safe and feasible to use terahertz signals to detect the characteristic spectra of biological samples at the cellular and molecular levels.

[0003] At present, in the research of terahertz biosensing detection, the methods for testing the characteristic spectra of samples are mainly divided into two aspects: optics and electronics. The common optical method is to combine a terahertz time-domain spectroscopy system (THz-TDS) with sensors such as terahertz metasurfaces for biological detection. Its basic principle is to use a femtosecond laser to excite a specific material, which radiates a terahertz time-domain pulse into free space under interaction. After a series of precise optical components regulate the signal, it radiates through the sample to be tested. The frequency-domain curve of the time-domain pulse is obtained by Fourier transform. By comparing the original detection signal and the terahertz signal carrying sample information, the frequency-domain information of the sample can be extracted. The implementation process of the optical method can be simply divided into two types: one is non-specific detection, that is, covering a layer of the substance to be tested on the surface of the terahertz sensor, comparing with the existing terahertz characteristic spectra for identification, and detecting its concentration level according to the size of the sample absorption peak; or measuring multiple single-component substances respectively, and comparing with the substance spectra obtained by other testing schemes with different principles to clarify its characteristic spectra and structural conformations, etc. The other is specific detection, that is, mainly constructing a specific metasurface sensor, and performing surface modification or special labeling on the sample, so that the sensor can detect specific target biological samples in the mixture. For terahertz biological sample detection based on the electrical method, it mainly relies on a microwave / millimeter-wave high-power signal source and a high-frequency spread-spectrum module to expand the frequency of the electromagnetic wave signal in the sub-terahertz frequency band so that the signal frequency reaches the terahertz frequency band. The difference from the optical method is that the signal starts to be output according to a specific frequency step value, and the signal is output from low frequency to high frequency in the test frequency band, and the signal is transmitted to the device to be tested by means of coaxial, waveguide, etc. Signal analysis and testing do not require first extracting the time-domain pulse and then performing frequency-domain transformation, but rely on devices such as vector network analyzers to measure the transmission / reflection parameters of the signal through the device to be tested at each frequency point, compare the original signal with the tested signal, analyze the frequency response of the sample to be tested to terahertz waves, and obtain the terahertz characteristic spectra of the biological sample from it.

[0004] Although terahertz waves show amazing application potential in the field of biological detection, there is still a certain distance from large-scale and practical applications. The main reason is that the devices and methods for generating and manipulating terahertz waves using optical devices are still very complex and not conducive to practical applications. Although the emergence of micro-nano devices such as metamaterials has increased the ways to achieve terahertz biological detection, there are still certain limitations in measuring the terahertz characteristic spectra of biological samples such as cells by this method at the present stage. For example, the manufacturing process of the metasurface sensor is relatively complex, and the prepared sensor has poor versatility and must be specially designed and optimized according to specific biological samples. In addition, the sensitivity and accuracy of the sensor are insufficient, making the detection method complex and restricting its development in biological sample detection.

[0005] Terahertz signals refer to electromagnetic wave signals with a frequency range of 0.1 - 10 THz, which play an important role in fields such as non-destructive testing, material property research, and biosensing. However, in the actual detection process, the existing methods using optical terahertz output systems and detectors have limitations such as complex detection systems, high prices, low output power, and insufficient detection sensitivity.

[0006] Measuring terahertz characteristic spectra by optical methods usually requires the assistance of a terahertz time-domain system (THz-TDS) to complete. These systems consist of numerous optical and electronic components, including femtosecond lasers, optical lenses, and detectors, etc. The system setup is complex and the cost is high. In addition, limited by the physical properties of materials such as photonic crystals, high-power terahertz waves cannot be generated based on optical methods. Currently, only millijoule-level pulse energy output can be achieved. The low output power easily causes signal attenuation and energy loss during the detection process, greatly limiting the types of biological samples and sample preparation methods that can be used for detection. In addition, the scheme for generating terahertz signals based on optical methods is very sensitive to environmental factors (such as temperature, humidity, vibration), etc. The measurement results of terahertz characteristic spectra obtained are highly correlated with the correctness of the system setup, and the accuracy cannot be guaranteed.

[0007] Based on this, on the basis of the electronics method, the present invention proposes a novel system and method for testing terahertz characteristic spectra of liquid biological samples by introducing them into a waveguide; this scheme solves multiple key problems existing in the prior art through innovative electronics methods and waveguide structures, and provides an efficient, stable, and low-cost terahertz detection scheme for biological samples. Summary of the Invention

[0008] The object of the present invention is to solve the above problems existing in the prior art, and proposes a system and method for testing terahertz characteristic spectra of samples based on a closed microfluidic waveguide channel. When using terahertz waves to detect biological samples, a liquid sample is input into the closed waveguide through the liquid inlet on the closed waveguide by a vector network analyzer (VNA) and a terahertz characteristic spectrum test structure of the liquid waveguide biological sample. One end of the closed waveguide receives the terahertz signal from the vector network analyzer and the frequency spreading module, and guides it to transmit inside the waveguide; when the terahertz wave passes through the biological sample, it will carry unique information from the biological sample itself. Subsequently, the output terahertz signal is transmitted to the other port of the vector network analyzer and the frequency spreading module, and through internal algorithm program calculation and extraction, the terahertz characteristic spectrum of the biological sample can be obtained. The present invention provides a new idea for biological detection using terahertz waves, and has advantages such as high feasibility and a wide variety of method selections.

[0009] The technical solution of the present invention is:

[0010] The present invention protects a method for testing the terahertz characteristic spectrum of a sample based on a closed microfluidic waveguide channel, comprising the following steps:

[0011] Control by a microfluidic chip to deliver a blank liquid without a biological sample into the waveguide, and a vector network analyzer sends an input signal spread-spectrum to the terahertz band through a spread-spectrum module;

[0012] Use the vector network analyzer to receive and save the frequency-domain signal of the blank liquid spread-spectrum to the terahertz band through the spread-spectrum module as the background characteristic spectrum;

[0013] Control by a microfluidic chip to deliver a sample liquid containing a biological sample into the waveguide, and a vector network analyzer sends an input signal spread-spectrum to the terahertz band through a spread-spectrum module;

[0014] Use the vector network analyzer to receive and save the frequency-domain signal of the sample liquid spread-spectrum to the terahertz band through the spread-spectrum module as the total characteristic spectrum;

[0015] Calculate the obtained total characteristic spectrum and the background characteristic spectrum to obtain the terahertz characteristic spectrum of the biological sample.

[0016] Use transmission lines such as waveguides to transmit signals. For signals of different frequencies, due to the size resonance effect, the internal structure of the closed waveguide also has different critical dimensions. The higher the frequency, the smaller the characteristic dimensions of the corresponding closed waveguide structure. When the signal frequency is in the terahertz band, the structural dimensions of the closed waveguide are roughly in the micrometer range. The structural dimensions of the waveguide channel are close to biological samples such as cells, which provides the rationality and feasibility for placing biological samples in the closed waveguide and analyzing the terahertz signals transmitted through the samples by a vector network analyzer to obtain their frequency characteristic spectra. Place the biological sample into the sample injection channel on the side wall of the closed waveguide and interact with the transmitted terahertz signal inside the waveguide. Compare the obtained output signal with the blank control signal without adding the biological sample in the waveguide, and the characteristic spectrum information of the biological sample in the terahertz band can be obtained.

[0017] Further, the biological sample detected by the method is a liquid biological sample including cells, proteins, DNA or RNA;

[0018] When the biological sample is a cell, a mixed liquid sample of PBS buffer + 2% DMSO can be used. DMSO can reduce the terahertz absorption coefficient by reducing the hydrogen bond density of water molecules, and the impact on cell viability can be ignored;

[0019] When the biological sample is a protein, a mixed liquid sample of glycerol + water can be used to maintain the structural invariance of the protein and reduce the absorption rate of water to terahertz waves;

[0020] When the biological sample contains DNA, a liquid sample of low ionic strength Tris-HCl buffer can be used.

[0021] The method can also be used to detect any liquid sample including organic matter, inorganic matter, and mixed liquid.

[0022] Furthermore, the waveguide is a closed waveguide, and both ends of the closed waveguide are connected with a frequency spreading module and a vector network analyzer; the vector network analyzer and the frequency spreading module output signals of specific frequencies. When the signal is input from one end of the waveguide and transmitted inside the waveguide and passes through the sample, it carries the terahertz characteristic information of the internal sample; when the signal is output from the other end of the waveguide, it is analyzed and processed by the vector network analyzer, the spectral information in a specific frequency band is extracted, and this information is transmitted to the PC side for characteristic spectrum calculation using relevant algorithms.

[0023] Furthermore, the blank liquid selected by the method has less absorption of terahertz electromagnetic waves, higher affinity for biological samples, and will not cause damage to biological samples.

[0024] Furthermore, the biological sample is transported into the waveguide through the liquid inlet on the side wall of the waveguide. The transportation method is to precisely control the liquid sample by a microfluidic chip and then inject it. It can also be directly injected by a pipette, the sample injection can be controlled by a hose plus a peristaltic pump, or the syringe can be pushed by a precision stepping electrode.

[0025] The present invention also protects a system for testing the terahertz characteristic spectrum of a sample based on a closed microfluidic waveguide channel, including a waveguide, a vector network analyzer, and a frequency spreading module; the waveguide is a closed metal waveguide, and a liquid inlet and a liquid outlet are opened on the side wall of the waveguide. Both ends of the waveguide are hermetically connected to window plates through flanges and then connected to the frequency spreading module respectively. The two frequency spreading modules are respectively connected to the input port and the output port of the vector network analyzer.

[0026] Furthermore, the system also includes a microfluidic chip, which is arranged at the positions of the liquid inlet and the liquid outlet or arranged inside the closed waveguide, and is used to control the sample parameters entering the waveguide, including the component ratio, component concentration, and volume mass of the sample.

[0027] Furthermore, the waveguide is a straight waveguide with dimensions meeting the terahertz frequency requirements, and the transverse dimension of the straight waveguide needs to satisfy λ / 4 ≤ d ≤ λ / 2, where λ is the terahertz wavelength corresponding to the center frequency of the working frequency band.

[0028] For example: at 0.3 THz (λ = 1 mm), the waveguide size range should be 250 - 500 μm;

[0029] At 1.0 THz (λ = 0.3 mm), the waveguide size range should be 75 - 150 μm.

[0030] Furthermore, the closed waveguide is a channel for transmitting electromagnetic waves and liquid samples internally. The outer shape of the closed waveguide structure can be rectangular, I-shaped, cylindrical or curved. Its shape and size should preferably ensure a good match of the electromagnetic wave mode and facilitate the uniform and stable flow of liquid biological samples without causing blockage or corrosion.

[0031] Advantages of the present invention:

[0032] (1) Efficient and stable terahertz signal generation and transmission: Compared with traditional optical terahertz signal generation methods, the present invention adopts an electronics solution, which uses a microwave / millimeter-wave high-power signal source combined with a frequency spreading module to up-convert the electromagnetic wave signal in the sub-terahertz frequency band to the terahertz frequency band to generate a high-power terahertz signal. This solution can stably output high-power terahertz signals in a wide frequency band through a vector network analyzer with high output power and a frequency spreading module, thus solving the problems such as signal attenuation and insufficient output power in the optical method, and greatly improving the detection sensitivity and signal quality; especially in the detection of biological samples, the high-power terahertz signal can ensure that the signal carries more accurate information when passing through the biological sample, avoiding the attenuation and distortion of low-power signals in the biological sample.

[0033] (2) Avoiding the complexity and high cost of the optical system

[0034] Traditional terahertz signal generation methods usually rely on complex optical systems, such as femtosecond lasers and optical lenses. These systems are not only complex to build and costly, but also extremely sensitive to environmental factors (such as temperature, humidity, vibration, etc.), resulting in a significant reduction in the stability and accuracy of the signal. The electronics solution of the present invention, especially through the combination of a vector network analyzer and a waveguide structure, avoids the high cost and complexity of the optical system. The electronics solution not only simplifies the system structure, but also can stably output high-power terahertz signals, with high reliability and adaptability, and is suitable for detection applications in the actual biomedical field.

[0035] (3) High stability and precision brought by the waveguide structure

[0036] The present invention uses a metal waveguide as the signal transmission channel. The metal waveguide can effectively reduce the radiation leakage loss in free space transmission and effectively shield the interference of the external electromagnetic environment. This waveguide structure ensures that the terahertz signal will not be affected by environmental noise during the measurement process, thereby improving the stability and accuracy of the measurement results. Compared with traditional optical methods, waveguide transmission can ensure that the signal is transmitted without attenuation over a long distance, thus avoiding the problem of signal loss and improving the detection accuracy.

[0037] (4) Precise control of the flow and quantification of biological samples

[0038] The present invention precisely controls the flow of liquid samples through a microfluidic chip, and can adjust parameters such as the volume, composition, and ratio of the samples to ensure the uniform flow and stability of the samples inside the waveguide. The introduction of microfluidic technology greatly improves the precision control of liquid samples, ensures the accuracy of the sample volume and composition in each experiment, and thus improves the repeatability and stability of test results.

[0039] (5) Non-destructive detection and high sensitivity of biological samples

[0040] Through the interaction between terahertz waves and biological samples, physical and chemical property information of the samples can be obtained without destroying the samples, especially the characteristics at the molecular level such as cells, proteins, and DNA. Compared with traditional biological detection methods such as fluorescence labeling, antibody recognition, and nucleic acid detection, terahertz waves have extremely strong penetration and non-destructiveness, can penetrate deep into the biological samples, and obtain more comprehensive information. Moreover, the electromagnetic wave channel structure in the terahertz frequency band waveguide is basically in the same order of magnitude as the size of biological cells, and the interaction between terahertz waves and biological samples is relatively strong, which makes the solution of the present invention particularly suitable for the detection of biological samples such as cells. By accurately measuring the characteristic spectra of biological samples, more information at the cellular and molecular levels can be obtained, the recognition ability of complex biological samples can be improved, and higher detection sensitivity can be achieved.

[0041] (6) Efficient characteristic spectrum extraction method

[0042] The present invention extracts the net characteristic spectrum of biological samples from the terahertz characteristic spectra obtained in experiments through calculation methods such as differential algorithms or neural networks. First, a reference model is established by measuring the background signal without biological samples; then, the biological samples are injected into the waveguide, and the measured total characteristic spectrum is compared with the background characteristic spectrum to extract the net characteristic spectrum, so as to accurately reflect the terahertz characteristic information of biological samples. Differential algorithms and neural network methods can improve the extraction accuracy of characteristic spectra, reduce the interference of noise, and further improve the accuracy and reliability of measurement results.

[0043] (7) Strong adaptability, suitable for a variety of biological samples

[0044] The technical solution of the present invention has high adaptability, can select suitable liquid solutions according to different types of biological samples, and precisely control the flow and composition of liquid samples through a microfluidic chip. Therefore, this solution is not only applicable to a single type of biological sample, but also can be widely used in the detection of a variety of biological samples, with good versatility. At the same time, in the process of detecting biological samples, the present invention adopts a technology that is non-destructive to biological samples, ensures their normal physiological and biochemical characteristics, and will not cause adverse effects on the samples.

[0045] (8) Diverse alternative solutions and high flexibility

[0046] The present invention also provides a variety of alternative solutions, such as different shapes of the closed waveguide structure (cuboid, I-shaped, cylindrical, etc.), various ways of loading biological samples (injection with a pipette, injection controlled by a peristaltic pump, injection controlled by a stepper motor, etc.), and flexible usage methods of the microfluidic chip. These alternative solutions make the technology highly flexible in different experimental environments and application scenarios, capable of being optimized and adjusted according to requirements, enhancing the operability and universality of the system.

[0047] Through innovative electronics solutions, metal waveguide structures, and microfluidic technologies, the present invention solves multiple bottlenecks in the prior art and provides an efficient, stable, and low-cost method for detecting the terahertz characteristic spectrum of biological samples. This method can not only improve the detection sensitivity, stability, and accuracy but also has strong adaptability and flexibility; its non-destructive detection characteristic makes it have broad application prospects in the fields of biomedicine, drug detection, environmental monitoring, etc. Description of the Drawings

[0048] Figure 1 It is a system structure diagram;

[0049] Figure 2 It is an enlarged view of the key structure of the system;

[0050] Figure 3 It is a sectional view of the system structure;

[0051] Figure 4 It is a flowchart of the test process;

[0052] In the above figures, 1, waveguide; 2, microfluidic chip; 3, liquid inlet; 4, liquid outlet; 5, spread spectrum module; 6, vector network analyzer; 7, flange; 8, window. Detailed Embodiments

[0053] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0054] To further understand the present invention, the present invention will be further described in conjunction with the drawings and embodiments.

[0055] Embodiment 1

[0056] To better utilize terahertz waves for biological detection, this embodiment provides a system for testing the terahertz characteristic spectrum of samples based on a closed microfluidic waveguide 1 channel.

[0057] In terms of terahertz test signal generation, amplification, and test system construction, based on an electronics solution, an analog circuit microwave / millimeter-wave high-power signal output source is utilized. In combination with a frequency spreading module 5, electromagnetic wave signals in the sub-terahertz frequency band are up-converted to the terahertz frequency band to achieve the generation of terahertz signals. Based on a high-power millimeter-wave signal source and a vector network analyzer 6, high-power output of terahertz signals is achieved. By using multiple groups of frequency spreading modules 5, the output signals of a single fixed frequency band are spliced and calibrated in frequency band to achieve stable output of high-power terahertz signals over a wide frequency band. The vector network analyzer 6 is used for high-precision signal measurement, and the flange 7 structure is used to reliably fixedly connect the precision metal waveguide 1 to components such as the vector network analyzer 6 and the frequency spreading module 5, realizing leak-free transmission of terahertz signals in the waveguide 1, avoiding the radiation leakage loss caused by the transmission of terahertz signals in free space in the optical solution, and the metal waveguide 1 can effectively shield the interference of the external electromagnetic environment, improving the signal quality and stability.

[0058] In terms of the system structure, as Figure 1 shown, the system includes a waveguide 1, a vector network analyzer 6, and a frequency spreading module 5. Both ends of the straight waveguide 1 that meets the terahertz frequency requirement dimensions are sealed respectively using window wafers 8 and the flange 7 structure to obtain a closed metal waveguide 1. The two ends of the closed waveguide 1 are respectively connected to the frequency spreading module 5, and the two frequency spreading modules 5 are respectively connected to the input port and the output port of the vector network analyzer 6. Openings are made on the side wall of the waveguide 1 orthogonal to the signal transmission direction as the paths for biological samples to enter and exit, the liquid inlet 3 and the liquid outlet 4. When the terahertz wave emitted by the vector network analyzer 6 enters the waveguide 1 from one end, the inside of the waveguide 1 has been pre-filled with the sample solution to be measured, so that the terahertz wave signal carrying its information can be received at the other end after passing through the biological sample.

[0059] The key structure of the system is as Figure 2 and Figure 3 shown. Window wafers 8 need to be used to seal both ends of the waveguide 1 to prevent liquid leakage. Then, using the flange 7 structure, the waveguide 1 is connected to the frequency spreading module 5, and the frequency spreading module 5 is generally connected to the vector network analyzer 6 using cables.

[0060] The function of the sealing window wafer 8 is to form a sealed environment for the waveguide 1 that allows terahertz electromagnetic waves to pass through, but the liquid biological sample cannot flow out from the signal input and output ports. In this way, without hindering the transmission of electromagnetic waves, the internal liquid can be sealed and will not flow into electrical components such as the vector network analyzer 6 and the frequency spreading module 5, causing problems such as equipment contamination and electric shock damage.

[0061] The function of flange 7 is to provide a standard and stable physical interface for the sealed window pane 8, metal waveguide 1, and test port, and to achieve reliable connection by using mechanical components such as pins, thereby improving the stability and reliability of the system at the hardware level.

[0062] Furthermore, the system also includes a microfluidic chip 2. Liquid precision control components such as the microfluidic chip 2 are provided at the liquid inlet 3 and liquid outlet 4 to achieve the inflow and outflow of the liquid sample to be measured, and to precisely regulate properties such as the composition ratio, component concentration, and volume mass of the liquid sample. In this embodiment, the amount of sample entering the waveguide 1 is controlled by the microfluidic chip 2. The microfluidic chip 2 has various usage methods. It can be controlled by combining the microfluidic chip 2 at the positions of the liquid inlet 3 and liquid outlet 4; it can also be controlled by integrating a microfluidic structure inside the closed waveguide 1. However, when the microfluidic structure is placed in the waveguide 1, it is necessary to meet the condition of not interfering with the measured electromagnetic wave signal, and at the same time, it can effectively regulate the internal liquid sample.

[0063] It should be noted that the outer shape of the closed waveguide 1 structure can be rectangular, I-shaped, cylindrical, curved, etc. The shape and size of the channels for transmitting electromagnetic waves and liquid samples inside should preferably ensure good matching of the electromagnetic wave mode and facilitate the uniform and stable flow of the liquid biological sample without causing damage such as blockage or corrosion. The sealed window pane 8 needs to be integrated with the waveguide 1 structure. The integration method can be fixedly connected through structures such as flange 7, or space can be reserved at both ends of the waveguide 1 structure, and it can be integrated by means of insertion fixation, glue bonding, etc. to ensure that the liquid does not leak; the material of the window pane 8 can be materials with low absorption and low attenuation of terahertz signals such as PTFE and TPX.

[0064] Furthermore, the waveguide 1 is a straight waveguide with dimensions meeting the terahertz frequency requirements. The transverse dimension of the straight waveguide needs to satisfy λ / 4 ≤ d ≤ λ / 2, where λ is the terahertz wavelength corresponding to the center frequency of the working frequency band. For example: at 0.3 THz (λ = 1 mm), the size range of the waveguide 1 should be 250 - 500 μm; at 1.0 THz (λ = 0.3 mm), the size range of the waveguide 1 should be 75 - 150 μm; a rectangular waveguide such as the WM-380 band with a width of 380 microns and a height of 190 microns can be used, which is suitable for the THZ band.

[0065] Embodiment 2

[0066] This embodiment provides a method for testing the terahertz characteristic spectrum of a sample based on a closed microfluidic waveguide 1 channel. In this method, both ends of the waveguide 1 corresponding to the terahertz frequency band are connected to the frequency spreading module 5 through the flange 7 and the sealing window 8. The frequency spreading module 5 is then connected to the input port and the output port of the vector network analyzer 6. An opening is made on the side wall of the waveguide 1 perpendicular to the signal transmission direction as the channel for the liquid biological sample to enter and exit, and microfluidic technology is used to control the composition and volume of the sample solution entering the waveguide 1 at the microscale. The vector network analyzer 6 and the frequency spreading module 5 output test signals of specific frequencies. When the signal is input into one end of the waveguide 1 through the sealing window 8, it will be transmitted inside the waveguide 1, pass through the biological sample placed in the waveguide 1 and interact with it, thereby carrying the terahertz characteristic information reflecting the characteristics of the biological sample. When the signal is output from the other end of the waveguide 1, after being analyzed and processed by the vector network analyzer 6, the spectral information in a specific frequency band can be extracted, and this information is transmitted to the PC side for calculating the characteristic spectrum and electrical parameters using relevant algorithms. By comparing the analysis result with the initially incident test signal, the terahertz characteristic spectrum information of the biological sample contained in the signal can be obtained.

[0067] Specifically, as Figure 4 shown, the steps include:

[0068] From the liquid inlet 3, use the microfluidic chip 2 to transport liquid into the waveguide 1. First, conduct experiments with the blank liquid without biological samples. The vector network analyzer 6 sends and collects the frequency-domain signals that have been frequency-spread to the terahertz frequency band through the frequency spreading module 5 and passed through the blank liquid as the corresponding background characteristic spectrum. Then, transport the sample liquid containing biological samples into the waveguide 1 through the microfluidic chip 2. The vector network analyzer 6 sends and collects and saves the frequency-domain signals of the sample liquid that have been frequency-spread to the terahertz frequency band through the frequency spreading module 5 to obtain the total characteristic spectrum containing biological samples and blank liquid. The changes in the measured total characteristic spectrum relative to the background characteristic spectrum are the characteristic information of the biological sample. Using calculation methods such as differential algorithms or neural networks, the net characteristic spectrum of the biological sample is extracted, and this net characteristic spectrum reflects the terahertz characteristic information of the biological sample.

[0069] The calculation steps are as follows:

[0070] (1) Align the spectrum of the blank liquid and the spectrum of the sample containing cells so that the two spectra have consistent frequency resolution and frequency range on the frequency axis. If there are differences, methods such as interpolation can be used for adjustment.

[0071] (2) Perform noise filtering on the two spectra respectively. Filtering algorithms such as wavelet transform or adaptive filtering can be used to weaken noise interference, improve the signal-to-noise ratio of the spectrum, make the characteristic peaks easier to identify, and lay a good foundation for subsequent differentiation.

[0072] (3) After completing data alignment and noise processing, taking the same frequency points as the benchmark, subtract the spectral intensity values of the cell-containing sample from those of the blank solution point by point. That is, for each frequency point f, calculate the differential spectral intensity S_diff(f) = S_sample(f) - S_blank(f), where S_sample(f) is the spectral intensity of the cell-containing sample and S_blank(f) is the spectral intensity of the blank solution at the corresponding frequency point. Negative values or outliers may appear after differentiation, which may be caused by factors such as measurement errors and noise interference. Set negative values to zero or make reasonable corrections, and filter and smooth the outliers to obtain a more authentic and reliable spectrum of the pure cell response signal.

[0073] (4) Compare the differential spectrum with the original spectrum of the cell-containing sample to check whether the characteristic peaks are retained and prominent, and whether the background signal is effectively subtracted. If the characteristic peaks of the differential spectrum are obvious and the background is clean, it indicates that the differentiation effect is good; otherwise, it is necessary to check the algorithm parameters and processing steps, optimize them, and conduct multiple experiments on the same sample until the results are stable and repeatable.

[0074] The above method is applicable to detecting liquid biological samples such as cells, proteins, DNA, or RNA. For the selection of liquid samples, the following two conditions need to be met: the selected liquid must have a small absorption of terahertz electromagnetic waves to avoid excessive attenuation of the measured signal. In addition, it is necessary to have a high affinity for biological samples, no toxicity or side effects, and will not affect the normal physiological and biochemical characteristics of biological samples, nor cause damage to the biological samples to be measured, affecting the rationality and accuracy of the test results.

[0075] When the biological sample is a cell, a mixed liquid sample of PBS buffer + 2% DMSO can be used. DMSO can reduce the terahertz absorption coefficient by reducing the hydrogen bond density of water molecules, and its impact on cell viability can be ignored;

[0076] When the biological sample is a protein, a mixed liquid sample of glycerol + water can be used to maintain the structural invariance of the protein and reduce the absorption rate of water to terahertz waves;

[0077] When the biological sample contains DNA, a liquid sample of low ionic strength Tris-HCl buffer can be used.

[0078] Furthermore, the biological sample is transported into the waveguide 1 through the liquid inlet 3 on the side wall of the waveguide 1. The transportation method is that after the microfluidic chip 2 precisely controls the liquid sample, it is then injected. It can also be directly injected by a pipette, injected by a hose with a peristaltic pump to control the sample, or pushed in by a precision stepper electrode to control the syringe.

[0079] Application Example 1

[0080] Taking a cell sample as an example, the detection process is as follows:

[0081] (1) Using a micro-injection pump, inject the blank solution (PBS buffer + 2% DMSO) into the microfluidic channel at a flow rate of 0.5 μL / min. The liquid film thickness is controlled by a sensor to be 20.0 ± 0.5 μm. Use a vector network analyzer 6 to collect and save the frequency-domain signal of the blank solution that has been spread-spectrum to the terahertz band by the spread-spectrum module 5 (as the background reference).

[0082] (2) Rinse the channel 3 times with 10 μL of ultrapure water and blow dry with nitrogen (pressure 0.2 MPa, for 10 seconds) to ensure that there is no liquid residue in the channel (residue volume < 0.1 μL). Inject the sample solution containing the target cells, maintain the flow rate at 0.5 μL / min, and keep the liquid volume the same as that of the blank solution.

[0083] (3) Wait for 3 - 5 minutes to stabilize the system temperature and liquid film thickness to the initial state (the same as the detection conditions of the blank solution). Use the vector network analyzer 6 to collect the terahertz frequency-domain signal of the cell-containing sample under the same parameters.

[0084] (4) Preprocess the two obtained spectral signals. After spectral calibration, dynamically subtract the blank signal from the sample signal using the differential algorithm to obtain the pure cell response signal.

[0085] (5) In the obtained terahertz frequency-domain absorption spectrum, identify the characteristic absorption peaks generated by the target biological sample and exclude environmental noise and non-target interference. The characteristic peaks can be used to distinguish different biological samples, and the peak position shift or intensity change can reflect the pathological state of the sample.

[0086] (6) Conduct multiple experiments. Measure the intensity of the characteristic peaks through standard samples with known concentrations, and fit linear or non-linear equations. Establish a mathematical model to correlate the physical parameters (intensity, position, shape) of the characteristic peaks with the quantitative indicators (concentration, activity, disease stage, etc.) of the biological sample, which is used to assist in formulating treatment plans.

[0087] The above description is only the preferred embodiment of the present invention and is not a limitation to the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, modifications, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for testing the terahertz characteristic spectrum of a sample based on a closed microfluidic waveguide channel, characterized in that It includes the following steps: Control the delivery of a blank liquid without biological samples into the waveguide through a microfluidic chip, and a vector network analyzer sends an input signal that has been spread-spectrum to the terahertz band by a spread-spectrum module; Use the vector network analyzer to receive and save the frequency-domain signal of the blank liquid that has been spread-spectrum to the terahertz band by the spread-spectrum module as the background characteristic spectrum; Control the delivery of a sample liquid containing biological samples into the waveguide through a microfluidic chip, and a vector network analyzer sends an input signal that has been spread-spectrum to the terahertz band by a spread-spectrum module; Use the vector network analyzer to receive and save the frequency-domain signal of the sample liquid that has been spread-spectrum to the terahertz band as the total characteristic spectrum; Calculate the obtained total characteristic spectrum and the background characteristic spectrum to obtain the terahertz characteristic spectrum of the biological sample.

2. The method according to claim 1, characterized in that, The biological sample detected by the method is a liquid biological sample including cells, proteins, DNA or RNA; When the biological sample is cells, a mixed liquid sample of PBS buffer + 2% DMSO is used; When the biological sample is protein, a mixed liquid sample of glycerol + water is used; When the biological sample contains DNA, a liquid sample of low ionic strength Tris-HCl buffer is used.

3. The method according to claim 1, wherein The waveguide is a closed waveguide, and both ends of the closed waveguide are connected to a spread-spectrum module and a vector network analyzer; the vector network analyzer and the spread-spectrum module output signals of specific frequencies. When the signal is input from one end of the waveguide and transmitted inside the waveguide and passes through the sample, it carries the terahertz characteristic information of the internal sample; After the signal is output from the other end of the waveguide, it is analyzed and processed by the vector network analyzer, the spectral information in a specific frequency band is extracted, and this information is transmitted to the PC side for characteristic spectrum calculation using relevant algorithms.

4. The method according to claim 1, wherein The blank liquid selected by the method has less absorption of terahertz electromagnetic waves, higher affinity for biological samples, and will not cause damage to biological samples.

5. The method according to claim 1, wherein The biological sample is delivered into the waveguide through the liquid inlet on the side wall of the waveguide. The delivery method is to precisely control the liquid sample by a microfluidic chip and then inject it. It can also be directly injected by a pipette, the sample injection is controlled by a hose and a peristaltic pump, or the syringe is pushed in by a precision stepping electrode.

6. A system for testing the terahertz characteristic spectrum of a sample based on a closed microfluidic waveguide channel, characterized in that, It includes a waveguide, a vector network analyzer, and a spread-spectrum module; the waveguide is a closed metal waveguide, and there are liquid inlets and outlets on the side wall of the waveguide. Both ends of the waveguide are hermetically connected to window pieces through flanges, and then connected to the spread-spectrum module respectively. The two spread-spectrum modules are respectively connected to the input port and the output port of the vector network analyzer.

7. The system according to claim 6, characterized in that, The system further includes a microfluidic chip, which is arranged at the positions of the liquid inlet and the liquid outlet or inside the closed waveguide, and is used to control the sample parameters entering the waveguide, including the composition ratio, component concentration, and volume mass of the sample.

8. The system according to claim 6, wherein The waveguide is a straight waveguide that meets the size requirements of terahertz frequencies. The transverse size of the straight waveguide needs to satisfy λ / 4 ≤ d ≤ λ / 2, where λ is the terahertz wavelength corresponding to the center frequency of the working frequency band.

9. The system according to claim 6, wherein The closed waveguide is a channel for transmitting electromagnetic waves and liquid samples internally. The outer shape of the closed waveguide structure can be rectangular, I-shaped, cylindrical or curved. Its shape and size should preferably ensure a good match of the electromagnetic wave mode and facilitate the uniform and stable flow of liquid biological samples without causing blockage or corrosion.

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