Micro-nano structure surface interface gas mass transfer behavior detection method

Abstract

The application discloses a kind of micro-nano structure surface interface gas mass transfer behavior detection methods, adopt a set of detection system core including laser light source, filtering collimation component and by four lenses constitute special optical imaging component, wherein lens one and two, lens three and four respectively constitute double telecentric light path, and lens two and three confocal plane, lens four focal length is twice of lens three.The method uses the above device, first collect the background image when no gas, then collect the image after the gas to be measured, through specific image processing procedure (including image pre-processing, frequency domain transformation and difference processing), directly from gas Rayleigh scattering light signal inversion two-dimensional spatial distribution of gas concentration.The application realizes the quantitative, visual measurement of gas concentration field near micro-nano structure surface interface, has the advantages of high contrast, high signal-to-noise ratio, and can sensitively characterize transient dynamic phenomena such as subsonic gas density wave.

Description

Technical Field

[0001] This invention belongs to the field of optical sensing and gas dynamics technology, specifically relating to a method for detecting gas mass transfer behavior at the interface of micro / nano structures. Background Technology

[0002] Constructing surface and interface materials with specific micro / nano structures is a general strategy for improving gas separation, catalysis, and sensing performance. Understanding the mass transfer behavior of gas at the surfaces and interfaces of micro / nano structures is crucial for designing and optimizing these high-performance materials and devices. Optical visualization monitoring technology, due to its non-invasive and high-resolution characteristics, is a powerful tool for studying this behavior. Among these methods, imaging based on the principle of Rayleigh scattering of gases is one feasible approach, as the intensity of scattered light is proportional to the concentration of gas molecules. Theoretically, the gas concentration can be quantitatively and visually measured by directly detecting the intensity of scattered light.

[0003] However, currently available gas optical visualization technologies mostly focus on indirect measurement and inversion using changes in light irradiance caused by gas. For example, patent document CN116740125A discloses a transparent fluid detection method based on light refraction and deep learning, which inverts the light deflection angle by calculating background displacement; CN116678586A discloses a focused schlieren flow field display technology, which uses a knife-edge to cut the light source image to display the flow field structure; and CN113108996A discloses a 4-channel optical visualization method for leak detection. f Imaging systems place a knife edge on the spectral plane. These existing technologies share a common characteristic: they all indirectly infer the distribution of gas density or concentration by detecting and comparing changes in irradiance (light intensity) of the background pattern in the presence or absence of gas, failing to directly and quantitatively obtain information about the concentration field of the gas molecules themselves. Furthermore, no publicly available examples of direct imaging using wavefront information from scattered gas light have been reported.

[0004] Therefore, existing technologies have a significant drawback: the lack of a visual detection method that can directly and quantitatively measure the spatial distribution of gas molecule concentration near the interface of micro / nano structures. Indirect inversion methods are limited in accuracy, susceptible to interference, and cannot directly establish a quantitative relationship between image signals and gas concentration, making it difficult to reveal the transient dynamics and scientific nature of gas mass transfer at the micro / nano scale. Summary of the Invention

[0005] This invention aims to solve the problem that existing gas visualization detection technologies cannot directly and quantitatively measure the concentration distribution of gas molecules at the interface of micro-nano structures. It provides a device and method for detecting gas mass transfer behavior at the interface of micro-nano structures, so as to achieve quantitative, visual and accurate characterization of gas mass transfer behavior at the micro-nano scale.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention proposes a method for detecting gas mass transfer behavior at the interface of micro / nano structures, comprising the following steps: A detection optical system is employed, which includes a laser source, a beam expander and collimator, a micro / nano structure placement area, an optical imaging component, and an image receiver arranged sequentially along the optical path; The micro / nano structure sample to be tested is placed in the micro / nano structure placement area; When the laser source is turned on, the emitted excitation light is processed by the beam expander and collimator to form a parallel beam, which then irradiates the micro / nano structure sample and the gas to be tested in the vicinity. When the micro / nano structure placement area is in a state without the gas to be measured, the first image is acquired through the image receiver; The gas to be tested is introduced into the micro / nano structure placement area. The optical imaging component collects the light rays containing the gas-scattered light signals from the micro / nano structure placement area and images them. Then, the image receiver acquires a second image. The optical imaging component includes a lens 1, a lens 2, a lens 3, and a lens 4 arranged coaxially along the optical path. The micro / nano structure placement area is located on the object plane of the optical imaging component. Along the light incident direction, the object plane is located between the lens 1 and its front focal point, and is closer to the lens 1 than the front focal point. The lens 1 and the lens 2 form a first set of telecentric optical paths, and the lens 3 and the lens 4 form a second set of telecentric optical paths. The lens 2 and the lens 3 are arranged in a confocal plane, and the focal length of the lens 4 is twice the focal length of the lens 3. Processing the first image and the second image to separate the signal caused by gas Rayleigh scattering from the second image and invert the gas concentration distribution specifically includes: The first image and the second image are preprocessed separately to enhance contrast; Frequency domain transformation and processing are performed on the preprocessed first and second images to extract the signal caused by gas scattering; Based on the correspondence between the gas scattering signal and the gas concentration, the spatial distribution of the gas concentration can be deduced. This allows for the acquisition and visualization of gas concentration distribution information near the interface of the micro / nano structure.

[0007] Furthermore, the object plane is located at a position one-quarter of the front focal length of the lens.

[0008] Furthermore, the laser source is a continuous laser with a wavelength of 532nm.

[0009] Furthermore, the beam expanding and collimating assembly includes a beam expanding lens, a filter pinhole, and a collimating lens. This assembly sequentially expands and collimates the small original beam emitted by the laser source into a parallel beam with a diameter of 12mm through beam expanding, spatial filtering, and collimation.

[0010] Furthermore, the filter pinhole has a diameter of 3mm.

[0011] Furthermore, the step of introducing the gas to be tested into the micro-nano structure placement area specifically includes: allowing the gas to be tested to flow through a channel with a micro-nano structure on its surface, and the outlet area of ​​the channel is located within the micro-nano structure placement area; The step of processing the first image and the second image is specifically used to acquire and visualize the image of the gas density wave formed after the gas to be tested flows out of the channel; The method characterizes the transient dynamic behavior of the gas near the micro / nanostructure interface of the channel by analyzing images of the gas density wave.

[0012] Furthermore, by changing the characteristic dimensions of the micro-nano structures on the channel surface, the variation law of the peak spacing of the gas density wave was observed and analyzed.

[0013] The beneficial effects of this invention are: 1. Quantitative Visualization Detection: For the first time, a dual telecentric optical path cascade structure is used in conjunction with scattered light intensity inversion to achieve quantitative visualization of gas concentration at the surface of micro-nano structures, solving the technical pain point that traditional methods can only detect qualitatively; 2. High-sensitivity transient detection: The optimized optical path structure and differential imaging method enable high-sensitivity detection of gas density waves excited by subsonic airflow at the micrometer scale, accurately capturing transient gas dynamic behavior; 3. Adaptable to micro-nano scenarios: Its large depth of field and high resolution imaging characteristics can be adapted to complex micro-nano structures such as micro-nano channels with self-assembled micron particles on the surface, making it applicable to a wide range of scenarios. 4. Stable and reproducible structure: The parameters of each component are clearly defined, and the optical path structure can be industrially built, possessing good practicality and scalability. Attached Figure Description

[0014] Figure 1 This invention proposes a device for detecting gas mass transfer behavior at microstructured interfaces.

[0015] Figure 2 This invention proposes a gas image concentration inversion processing method.

[0016] Figure 3 This is a comparison chart of experimental observations and corresponding simulation results of the diffusion behavior of gas incident on the surface of micro / nano structures from different directions.

[0017] Figure 4 It is the equation relating the intensity of scattered light to the concentration of butane gas at different concentrations in the air, obtained by inversion.

[0018] Figure 5 The process involves testing CO2 gas at different concentrations, repeating the above steps, and fitting an equation relating CO2 scattered light to gas concentration. This device determines a precise characterization of gas diffusion patterns by detecting and inverting the gas scattered light signal; therefore, it is suitable for detecting a variety of different gas molecules.

[0019] Figure 6 This is a schematic diagram of the direct observation and quantitative inversion results of the diffusion process of butane gas near the micro-nano structure.

[0020] Figure 7 This is a schematic diagram of two different gas flow patterns generated within a microscale channel.

[0021] Figure 8 This is a schematic diagram showing the propagation of gas generated by an air compressor in the form of waves after flowing into a micro-nano channel.

[0022] Figure 9 It is a comparison and statistical diagram of the gas density waves excited under the characteristic size of surface microstructure and their influence on wave parameters. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the embodiments of this invention are described in further detail below with reference to specific experiments. The following examples are for illustrative purposes only and are not intended to limit the scope of this invention.

[0024] This invention aims to solve the technical problem that existing technologies cannot achieve quantitative visualization of gas concentration at the surface of micro-nano structures and high-sensitivity detection of transient gas dynamics by using a structure design of two sets of cascaded dual telecentric optical paths, combined with a specific focal length ratio and object distance setting. At the same time, it achieves imaging performance with large depth of field, high resolution, and high contrast, providing a high-precision and reproducible detection method for the research and development of micro-nano devices and the study of mass transfer mechanisms.

[0025] Based on the linear relationship between the image grayscale value and the gas concentration of the gas distribution, the spatial distribution of gas concentration φ(x, y) is obtained by inversion, where (x, y) are the spatial coordinates of the gas in the object plane.

[0026] Example 1: Device Setup and Quantitative Visualization of Gas Concentration. This example specifically illustrates the setup method, workflow, and implementation process of the device for quantitatively detecting gas concentration distribution according to the present invention. Device Setup: like Figure 1As shown, this invention provides a device for detecting the gas mass transfer behavior at a microstructure surface, which includes, in sequence along the optical path: a laser source, a beam expander and collimator, a micro / nano structure placement area, an optical imaging component, and an image receiver.

[0027] Laser source: A continuous laser 1 with a wavelength of 532nm and an output power of 1.2W is used to provide a stable excitation beam.

[0028] The beam expanding and collimating assembly includes a beam expanding lens 2, a filtering pinhole 3, and a collimating lens 4. This assembly sequentially expands and collimates the small original beam emitted by the continuous laser 1 into a parallel beam with a diameter of approximately 12 mm through beam expansion, spatial filtering, and collimation. The beam expanding lens 2 is positioned in the output optical path of the continuous laser 1 to initially expand the initial beam emitted by the continuous laser 1, increasing the beam aperture. The filtering pinhole 3 is positioned in the output optical path of the beam expanding lens 2 to perform spatial filtering on the beam after expansion, removing higher-order mode noise and stray light from the beam and improving beam quality. The collimating lens 4 is positioned in the output optical path of the filtering pinhole 3 to collimate the filtered beam, forming a parallel beam with uniform energy distribution for subsequent uniform illumination of the sample. A micro / nano structure placement area is used to place the micro / nano structure 6 to be tested and to introduce the gas to be tested 5 into it. The micro / nano structure 6 can be a PMMA microchannel with its inner wall modified with self-assembled silica microspheres. Its cylindrical channel has a diameter of 0.5 mm. This structure can be used to study the influence of surface and interface properties on gas mass transfer behavior.

[0029] The optical imaging assembly, which forms the core imaging optical path, includes lenses 7 (focal length 7) arranged sequentially along the optical path. =500mm), Lens 2 (focal length) =300mm), Lens 39 (focal length) =15mm) and lens four 10 (focal length) =30mm). Among them, lens 7 and lens 8 share a common focal plane, forming the first group of 4. f Imaging system; Lens 3 (9) and Lens 4 (10) share a common focal plane, forming the second group. Imaging system. This special design ensures that the gas-scattered light signal within the micro-nano channel can be transmitted to the image plane with high fidelity and without aberrations.

[0030] The image receiver employs a high-sensitivity CMOS image sensor 11 with a pixel size of 2.40μm×2.40μm, readout noise below 1.0e-, and a bit depth of 16bit, for high-precision recording of gas scattered light images.

[0031] like Figure 2The diagram illustrates the gas image processing and concentration inversion method provided by this invention. First, the gas outlet is placed on the object plane of the detection device of this invention (located in front of lens one, its position is...). ,in (The focal length of lens one) and the gas to be tested is released at a constant flow rate of 50 mL / min. Under pure air conditions, background illumination light field images without gas introduction are acquired using a CMOS image sensor. Image of the target gas after gas introduction The specific steps are as follows: Obtain the illumination field image as background when no gas is introduced. Image of the target gas after gas introduction : Original target gas image :

[0032] in, T gsn ( x, y () indicates the gas permeability.

[0033] Perform histogram equalization on the obtained image to get: For gas images:

[0034] For the background image:

[0035] in, and These are the normalized grayscale matrices of the gas image and the background image, respectively.

[0036] Taking the logarithm of the obtained image yields ln ; Perform a Fourier transform on the above images and add them together: Perform an inverse Fourier transform on the above results and take the e-exponent to obtain the space gas concentration. ; This processing step eliminates background noise interference caused by uneven illumination and linearly maps the image grayscale values ​​to the [0,1] range, achieving accurate extraction of gas scattered light signals at the interface of micro-nano structures. This provides a standardized and quantitative image data basis for subsequent inversion of the spatial distribution of gas concentration.

[0037] The above processing flow effectively removes the interference caused by uneven background illumination through a series of operations such as normalization, logarithmic transformation, frequency domain difference and phase correction, and realizes the enhancement and extraction of weak gas Rayleigh scattering signals, thus providing a reliable data foundation for the quantitative and visual reconstruction of gas concentration fields at the interface of micro and nano structures.

[0038] Let the gas concentration at each pixel spatial coordinate of the obtained image be... In a vacuum, the intensity of Rayleigh scattering of a gas is linearly related to the gas concentration, i.e. , The slope is the intercept. Here, it is the intercept of the equation relating scattering intensity and gas concentration for air (primarily a mixture of nitrogen and oxygen). The target gas concentration satisfies the following equation: The function of the object plane is to stably place micro / nanostructured samples (such as microchannels with self-assembled micron particles on their surface, or samples to be detected), ensuring the optimal relative position between the sample surface and the imaging optical path. This guarantees the accuracy of gas scattered light acquisition and concentration inversion, while also providing a stable reference for imaging in dual telecentric optical paths, avoiding detection errors caused by sample position shifts. In simple terms, the system object plane serves as both the reference plane for sample placement and the reference plane for optical path imaging. Its core function is to ensure precise alignment between the micro / nanostructured sample, the imaging optical path, and the image acquisition components, guaranteeing the accuracy of gas concentration detection and transient gas behavior capture.

[0039] To verify the accuracy of the device and method of the present invention in quantitatively characterizing gas mass transfer behavior, this embodiment systematically compares the experimental observation results with the computational fluid dynamics simulation results.

[0040] like Figure 3 As shown, a micro / nano structure sample with a specific morphology was first prepared using high-precision 3D printing technology. Subsequently, using the device of this invention, the diffusion process of gas incident on the surface of the microstructure in different directions (including two horizontal directions and one vertical direction) was detected, and the corresponding gas concentration distribution images were acquired. Figure 3 (a)- Figure 3 (c) Right figure). Simultaneously, based on the same physical model and boundary conditions, corresponding numerical simulations were performed, and the simulated gas diffusion distribution results were obtained ( Figure 3 (a)- Figure 3 (c) Left image).

[0041] Comparative analysis shows that the gas diffusion morphology, effective range, and concentration gradient directly measured by the device of this invention are in high agreement with the spatial distribution of the simulation predictions based on the physical model. This consistency strongly cross-validates that the detection device and method provided by this invention can realistically and accurately reflect the complex gas mass transfer behavior at the interface of micro-nano structures, and its measurement results have high reliability and credibility.

[0042] like Figure 4 As shown, in order to quantitatively verify the accuracy of the device of the present invention in directly and quantitatively measuring gas concentration, this embodiment uses butane gas as a standard sample and establishes a quantitative relationship between the intensity of scattered light signal and gas concentration through a systematic calibration experiment.

[0043] The specific implementation process is as follows: Butane and air are mixed at a set ratio using a high-precision mass flow controller to generate a known and precise concentration gradient within the range of 10 ppm to 80 ppm. The mixed gas is delivered to the object plane region of the device through a conduit with an inner diameter of 1 mm at a constant flow rate of 100 mL / min. The Rayleigh scattering light signal generated by the gas at each concentration point is acquired using the CMOS image sensor. To ensure data reliability, three repeated measurements were performed under the same experimental conditions, and the average signal intensity was taken as the final result.

[0044] like Figure 5 The diagram illustrates the detection results of different types of gases using the device and method of the present invention. To verify the universality and accuracy of the device and method for detecting different types of gases, carbon dioxide (CO2) gas was used for verification testing. The device adjustment, image acquisition, and processing steps in Example 1 were repeated to detect CO2 gas samples of known concentrations and collect their scattered light signals. By linearly fitting the signal intensity and gas concentration data, a quantitative equation for the scattered light intensity-concentration relationship of CO2 gas was obtained.

[0045] Experimental results show that for CO2 gas, the intensity of its scattered light signal also exhibits a good linear response with its concentration. This confirms that the effectiveness of the device and method described in this invention is not limited to specific gases (such as butane), but is based on the universal physical principle of Rayleigh scattering of gases. Therefore, this invention can be widely applied to the quantitative and visual detection of mass transfer behavior of various gas molecules at the interfaces of micro- and nano-structures, demonstrating good versatility and application prospects.

[0046] like Figure 6 As shown, this invention demonstrates the quantitative detection results of the free diffusion process of butane gas in a static environment. Figure 6 (a) is the original image obtained by the device of the present invention and the image processing method described above, which intuitively shows the diffusion pattern of gas from the central release point to the surrounding space.

[0047] Figure 6 (b) is a two-dimensional pseudo-color map of gas concentration distribution obtained by inversion based on the aforementioned calibration relationship (i.e., the linear relationship between gas concentration and signal intensity). The color changes in the map represent the spatial gradient of gas concentration, and the color scale on the right quantitatively indicates the concentration value (unit: ppm). For precise quantification, the corresponding gas concentration values ​​are marked at five characteristic spatial coordinate points in the map, namely 36.30 ppm, 13.96 ppm, 21.78 ppm, 31.83 ppm, and 8.93 ppm, which directly verifies the quantitative analysis capability of the method of this invention.

[0048] Experiments show that the gas concentration inversion error achieved by this method is less than 3%, and the spatial resolution reaches 2 μm. This result fully demonstrates that the device and method described in this invention can achieve high-precision, quantitative, and visual detection of gas diffusion concentration fields at the micro-nano scale, fully meeting the precision measurement needs in fields such as internal mass transfer analysis of micro-nano devices and research on surface and interface mass transfer mechanisms.

[0049] The results confirm that the device and method of this invention can not only visualize the diffusion behavior of gases, but more importantly, can convert the collected optical signals into a precise concentration distribution based on the Rayleigh scattering principle of gases through quantitative calibration relationships. This achieves a leap from qualitative observation to quantitative measurement, verifying the core quantitative capability of this invention in characterizing the gas mass transfer behavior at the interface of micro / nano structures.

[0050] like Figure 7 The diagram shows the simulation results of this invention. It illustrates two typical flow modes observed and distinguished by the device of this invention when gas flows within a microscale channel. This result intuitively reveals the complexity of gas flow behavior in micro- and nano-scale confined spaces. Specifically, in the near-wall region of the channel, the characteristic scale of the interaction between gas molecules and the wall is comparable to the channel scale, and the gas exhibits a slip flow mode; while in the central region of the channel, the gas flow is closer to a conventional continuous flow mode. This provides crucial evidence for further in-depth research on the regulation mechanism of gas mass transfer by micro- and nano-structures. The horizontal axis represents the position along the micro- and nano-channel (unit: μm). The zero point (0 μm) is set as one end of the channel, and the horizontal axis from 0 to 450 μm marks the region with a total channel length of 500 μm.

[0051] like Figure 8 As shown, this is a unique dynamic phenomenon observed using the device of the present invention, which is generated when gas flows at high speed in a micro-nano channel with surface microstructures.

[0052] The left side shows a schematic diagram of the experimental setup. An air compressor generates subsonic gas flow (velocity 153 m / s, Mach number 0.45), which flows into the micro-nano channel 82 through nozzle 81. This channel is fabricated using a CO2 laser to engrave a PMMA plate; it is a hollow cylinder with a diameter of 0.5 mm, and its inner wall is self-assembled using a sol-gel method to form a layer with a diameter of... d Silica microspheres with a diameter of 10 μm form a periodic surface structure.

[0053] The image on the right shows a transient image of gas flowing out of the channel, directly acquired and processed using the device and method of this invention. The results show that the gas did not diffuse uniformly, but rather formed a series of forward-propagating, regularly arranged periodic density waves (I represents signal intensity, and r represents spatial position in the image). This is the first experimental observation of this type of gas density wave phenomenon generated by microstructural disturbances in subsonic airflow. Further research shows that the wavelength of the generated gas density wave is related to the diameter of the self-assembled nanoparticles on the channel surface, and decreases as the particle diameter decreases. This result strongly demonstrates that the device of this invention has extremely high spatiotemporal resolution and detection sensitivity, enabling it to reveal the transient dynamics of gas-surface interaction at the micro-nano scale, which is difficult to capture using traditional methods. This patent overcomes the limitation of previous systems that could not directly measure gas concentration information, realizing the direct detection and quantitative characterization of gas concentration and its fluctuation parameters (such as density wave wavelength). This result strongly demonstrates that the device of this invention has extremely high spatiotemporal resolution, detection sensitivity, and quantitative capability, enabling it to reveal the transient dynamics of gas-surface interaction at the micro-nano scale, which is difficult to capture using traditional methods, and its inherent laws.

[0054] To quantitatively reveal the influence of surface microstructure feature size on the characteristics of excitation gas density waves, this embodiment further changed the size of the self-assembled microparticles on the inner wall of the channel and repeated the high-speed gas flow experiment.

[0055] like Figure 9 The figure shows a comparison and statistical diagram of the gas density waves excited under the characteristic size of surface microstructure and their influence on wave parameters.

[0056] To further verify the ability of the device of this invention to explore the microscopic mass transfer mechanism, we studied the influence of the surface microstructure feature size on the excited gas density wave and its key parameter (wave crest spacing).

[0057] The specific experiment is as follows: While keeping the gas type, flow rate, pressure, and other experimental conditions exactly the same, only the diameter of the silica microspheres modified on the inner wall of the microchannel was changed. The diameters were successively adjusted. d 1 = 10 micrometers d 1' = 5 micrometers and dMicrospheres with a diameter of 1'' = 2 micrometers were used for modification. The device of this invention was used to observe and image the gas flow and concentration distribution near the surface of different samples.

[0058] (a) Comparison of structural changes and phenomena: Figure 9 (a) illustrates the comparison of observational results corresponding to microstructures with different feature sizes. It can be clearly observed that as the feature size of the surface microstructure decreases, the spacing between the peaks of the excited gas density wave also decreases significantly. This indicates that the geometric scale of the micro / nanostructure directly modulates the characteristic spatial frequency of the gas mass transfer process in its vicinity.

[0059] (b) Quantitative statistical analysis: To accurately characterize this pattern, we analyzed three different feature sizes ( d 1 = 10 micrometers d 1' = 5 micrometers d The peak spacing of the gas density wave generated at 1'' = 2 micrometers was repeatedly measured and statistically analyzed at multiple consecutive position intervals (AB, BC, CD) after the gas flow out of the channel. The results are as follows: Figure 9 (b) is shown in the bar chart.

[0060] Data shows that within any selected measurement interval (AB, BC, or CD), the measured value of the peak spacing systematically and significantly decreases with decreasing diameter of the modified silica microspheres. For example, in all intervals, d The mean peak spacing is smallest at 1'' (2 micrometers). d 1' (5 micrometers) is the next best, d The maximum value is 1 (10 micrometers). This statistical result quantitatively and conclusively demonstrates a direct correlation between the morphological parameters (crest spacing) of the gas density wave and the feature size of the surface microstructure.

[0061] This embodiment not only demonstrates that the method of the present invention can clearly observe and quantify the microscopic phenomenon of gas density waves, but more importantly, by actively changing the size of the surface microstructure and using the present invention for precise measurement, it reveals the physical law that "the spacing between wave crests decreases as the size of the structural feature decreases." This fully demonstrates that the device of the present invention is not only an observation tool, but also a powerful research means to reveal the intrinsic mechanism of microscopic mass transfer processes, providing direct experimental evidence and data support for micro / nano system design, catalyst optimization, and other fields. In this invention, "gas density wave" specifically refers to the phenomenon that, near the interface of a micro / nano structure, the local gas concentration fluctuates periodically and regularly in space due to the complex mass transfer, adsorption, or reaction processes between the gas and the solid surface. Optically, this concentration fluctuation manifests as the periodic modulation of Rayleigh scattering intensity, thus forming alternating bright and dark stripes or wavy patterns with specific spatial frequencies in the detected gas concentration distribution image.

[0062] This series of experiments quantitatively confirmed the following core principle: the characteristic size of the surface microstructure is a key parameter for regulating the transient mass transfer behavior of near-wall gas, and the wavelength of the excited gas density wave decreases as the characteristic size of the surface microstructure decreases. This discovery not only highlights the superior ability of the device of this invention to capture weak signals at the micro- and nano-scale and to quantitatively analyze physical laws, but also provides direct experimental evidence and theoretical guidance for regulating gas mass transfer processes through the active design of surface microstructures.

[0063] In summary, the working principle of this invention is as follows: This invention employs a cascaded dual telecentric optical path design. The first dual telecentric optical path achieves large depth of field and distortion-free imaging in the object space, while the second dual telecentric optical path achieves high-precision magnification in the image space. Combined with a fourth lens and a focal length ratio of 2:1 with the third lens, and an object distance setting of -1 / 4 the front focal length of the first lens, the contrast and signal-to-noise ratio of scattered light imaging are significantly improved. By acquiring the Rayleigh scattering intensity signal of the gas, a linear correspondence between image grayscale and gas concentration is established, enabling quantitative visualization of gas concentration at the micro / nano structure interface. Through differential imaging processing in gas-free and gas-flowing states, background noise is effectively suppressed, achieving high-sensitivity detection of gas density waves when subsonic airflow passes through micro / nano channels, accurately characterizing the correlation between peak spacing and micron particle size.

[0064] This invention achieves a large optical field illumination range by employing a beam-expanding and collimating assembly composed of lenses with focal lengths of 5cm and 20cm. Combined with a high-power, short-wavelength (532nm) laser source and a short object distance design—specifically, the short object distance refers to the distance from the sample under test (i.e., the micro / nanostructure placement area) to the first imaging lens (lens one)—this distance is designed to be less than the focal length of lens one. This maximizes the collection of weak Rayleigh scattered light, optimizes the depth of field for microscale imaging, and works in conjunction with subsequent optical paths to separate scattered light from background light, ultimately achieving the invention's objective of quantitatively visualizing and highly sensitively detecting the gas concentration at the micro / nanostructure surface. These technical features synergistically achieve a large field of view and high-sensitivity imaging of gas Rayleigh scattering signals, enabling clear capture and quantitative analysis of transient gas mass transfer behavior at the micro / nano scale.

[0065] It should be understood that the above description of the preferred embodiments is quite detailed and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art, under the guidance of the present invention, can make substitutions, modifications, or improvements without departing from the scope of protection of the claims, all of which fall within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the appended claims.

[0066] The specific embodiments described in this invention are merely illustrative and not intended to limit the scope of protection. Within the scope defined by the spirit and claims of this invention, various modifications and implementations are possible: the steps described in this invention may be executed in a different order than those described in the embodiments, and may also be used when multitasking or parallel processing is feasible; any specific modifications, improvements, or implementations made by those skilled in the art based on the teachings of this invention after learning of this invention, without departing from the above-mentioned scope of protection, shall fall within the scope of protection of this invention.

Claims

1. A method for detecting gas mass transfer behavior at the interface of micro / nano structures, characterized in that, Includes the following steps: A detection optical system is employed, which includes a laser source, a beam expander and collimator, a micro / nano structure placement area, an optical imaging component, and an image receiver arranged sequentially along the optical path; The micro / nano structure sample to be tested is placed in the micro / nano structure placement area; When the laser source is turned on, the emitted excitation light is processed by the beam expander and collimator to form a parallel beam, which then irradiates the micro / nano structure sample and the gas to be tested nearby. When the micro / nano structure placement area is in a state without the gas to be measured, the first image is acquired through the image receiver; The gas to be tested is introduced into the micro / nano structure placement area. The optical imaging component collects the light rays containing the gas-scattered light signals from the micro / nano structure placement area and images them. Then, the image receiver acquires a second image. The optical imaging component includes lenses one, two, three, and four arranged coaxially along the optical path. The micro / nano structure placement area is located on the object plane of the optical imaging component, along the light incident direction. The object plane is located between lens one and its front focal point, and is closer to lens one than the front focal point. Lens one and lens two form a first set of telecentric optical paths, and lens three and lens four form a second set of telecentric optical paths. Lens two and lens three are arranged in a confocal plane, and the focal length of lens four is twice the focal length of lens three. Processing the first image and the second image to separate the signal caused by gas Rayleigh scattering from the second image and invert the gas concentration distribution specifically includes: The first image and the second image are preprocessed separately to enhance contrast; Frequency domain transformation and processing are performed on the preprocessed first and second images to extract the signal caused by gas scattering; Based on the correspondence between the gas scattering signal and the gas concentration, the spatial distribution of the gas concentration can be deduced. This allows for the acquisition and visualization of gas concentration distribution information near the interface of the micro / nano structure.

2. The method for detecting gas mass transfer behavior at the interface of micro / nano structures according to claim 1, characterized in that, The object plane is located at a position one-quarter of the front focal length of the lens.

3. The method for detecting gas mass transfer behavior at the interface of a micro / nano structure according to claim 1, characterized in that, The laser source is a continuous laser with a wavelength of 532nm.

4. The method for detecting gas mass transfer behavior at the interface of micro / nano structures according to claim 1, characterized in that, The beam expanding and collimating assembly includes a beam expanding lens, a filter pinhole, and a collimating lens. This assembly sequentially expands and collimates the small original beam emitted by the laser source into a parallel beam with a diameter of 12mm through beam expanding, spatial filtering, and collimation.

5. The method for detecting gas mass transfer behavior at the interface of a micro / nano structure according to claim 4, characterized in that, Furthermore, the filter pinhole has a diameter of 3mm.

6. A method for detecting gas mass transfer behavior at the interface of a micro / nano structure according to any one of claims 1 to 5, characterized in that, The step of introducing the gas to be tested into the micro-nano structure placement area specifically includes: allowing the gas to be tested to flow through a channel with a micro-nano structure on its surface, and the outlet area of ​​the channel is located within the micro-nano structure placement area; The step of processing the first image and the second image is specifically used to acquire and visualize the image of the gas density wave formed after the gas to be tested flows out of the channel; The method characterizes the transient dynamic behavior of the gas around the micro / nanostructure interface of the channel by analyzing images of the gas density wave.

7. The method for detecting gas mass transfer behavior at the interface of a micro / nano structure according to claim 6, characterized in that, By changing the characteristic dimensions of the micro-nano structures on the channel surface, the variation law of the peak spacing of the gas density wave was observed and analyzed.

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