Dark field differential dynamic microscopy system and method for characterization of bulk nanobubbles

Abstract

The present application relates to the technical field of body phase nanometer bubble characterization, and discloses a dark field differential dynamic microscopic system and method for body phase nanometer bubble characterization.The system comprises an illumination light path and a measurement light path.The illumination light path comprises a laser, a mirror and a cylindrical lens arranged in sequence.The measurement light path comprises a sample cell, a microscope objective, a first lens, a second lens, a third lens and a CMOS high-speed camera arranged in sequence, and the microscope objective, the first lens, the second lens, the third lens and the CMOS high-speed camera are located on the same axis.The present application obtains the motion information of the body phase nanometer bubble by the frequency domain change of the microscopic motion image, thereby calculating the particle size.Compared with the existing characterization technology, the present application greatly reduces the measurement time and instrument cost, solves the defect that the existing characterization technology only uses low concentration samples for characterization, is suitable for a wide range of sample concentrations, and realizes the efficient and accurate characterization of the body phase nanometer bubble under the condition of visualization.

Description

Technical Field

[0001] This invention belongs to the field of bulk nanobubble characterization technology, specifically relating to a dark-field differential dynamic microscopy measurement system and method for bulk nanobubble characterization. Background Technology

[0002] Bulk nanobubbles have attracted attention in various fields due to their unique physicochemical properties, and the characterization techniques for bulk nanobubbles have always been an important part of bulk nanobubble research. Although existing bulk nanobubble characterization methods can accurately measure the particle size information of bulk nanobubbles, they all have problems such as high equipment requirements, long measurement time, and can only be applied to the measurement of low-concentration samples, which will introduce large errors for high-concentration samples.

[0003] Currently, dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) are frequently used to measure the particle size of bulk nanobubbles. However, both DLS and NTA have limitations. NTA requires optically distinguishable particles, thus limiting its application to solutions with varying concentrations and particle sizes, and also resulting in lengthy measurement times. For high-concentration samples, the correlation function of DLS is highly susceptible to multiple scattering, making experimental setups more complex, hindering visualization measurements, and further increasing measurement time. Summary of the Invention

[0004] The purpose of this invention is to provide a dark-field differential dynamic microscopy system and method for characterizing bulk nanobubbles, enabling the measurement of a wide range of bulk nanobubbles under visualized conditions and obtaining particle size information. Dark-field differential dynamic microscopy technology enables visualized measurement of bulk nanobubble particle size on a microscopic system, significantly reducing measurement time and allowing for the measurement of high-concentration samples.

[0005] To achieve the objective of this invention, the present invention provides a dark-field differential dynamic microscopy measurement system for characterizing bulk nanobubbles, comprising an illumination optical path and a measurement optical path: the illumination optical path includes a laser, a reflector, and a cylindrical lens arranged sequentially, the reflector being used to reflect the incident light emitted by the laser to the cylindrical lens; the measurement optical path includes a sample cell, a microscope objective, a first lens, a second lens, a third lens, and a CMOS high-speed camera arranged sequentially, the microscope objective, the first lens, the second lens, the third lens, and the CMOS high-speed camera being located on the same axis.

[0006] Furthermore, the laser, mirror, and cylindrical lens are located on one side of the sample cell. The incident light passes through the mirror and then the cylindrical lens. The center of the mirror and the center of the incident light source are on the same axis, and the center of the mirror and the center of the cylindrical lens are on another axis, and the two axes are perpendicular to each other. The microscope objective, first lens, second lens, third lens, and CMOS high-speed camera are located on one side of the sample cell, and the centers of the microscope objective, the first lens, the second lens, the third lens, and the CMOS high-speed camera are on the same axis, and are perpendicular to the axis of the cylindrical lens.

[0007] Furthermore, the incident light source passes through the reflecting mirror to the cylindrical lens, changing from a point source to a surface source before entering the sample cell. The sample-scattered light passes through the microscope objective, the first lens, the second lens, and the third lens, and is then used to complete microscopic imaging on the CMOS camera.

[0008] Furthermore, the first lens is a microscope tube lens whose focal length matches that of the microscope objective lens, and the second and third lenses are biconvex lenses with the same focal length.

[0009] Furthermore, the acquisition of microscopic motion images is completed on a CMOS high-speed camera, by capturing the motion state of bulk nanobubbles and extracting each frame of the image.

[0010] This invention also provides a dark-field differential dynamic microscopy method for characterizing bulk nanobubbles, characterized in that it employs the system described in any one of claims 1-4, and the method includes the following steps:

[0011] Bulk nanobubbles are injected into the sample cell;

[0012] A laser emits incident light into the sample cell, and a CMOS high-speed camera acquires microscopic motion images.

[0013] The acquired microscopic motion images are differentially analyzed to obtain a difference map. A two-dimensional fast Fourier transform is then performed on the difference map to obtain the frequency domain data of the difference map.

[0014] By fitting the frequency domain data of the difference map, the amplitude A(q) of the image signal, the noise part B(q) of the camera image, and the intermediate scattering function f(q,Δt) are obtained;

[0015] The diffusion coefficient of bulk nanobubbles is obtained by linear fitting of the intermediate scattering function f(q,Δt), and the particle size of bulk nanobubbles is obtained based on the diffusion coefficient of bulk nanobubbles.

[0016] Furthermore, the bulk nanobubbles are generated via an electrochemical method.

[0017] Furthermore, image difference is obtained by subtracting the second to the last photo from the first photo of the microscopic motion image, resulting in a difference map D(x,y,t,Δt), which is used to describe the difference in the intensity of scattered light between time Δt and the initial time.

[0018] Frequency domain analysis involves performing a two-dimensional fast Fourier transform on the obtained difference image to acquire the spectral data of the difference image, and then fitting the image structure function (ISF) to obtain the image structure function (ISF). Data fitting extracts the intermediate scattering function f(q,Δt) from the image structure function (ISF) to obtain the motion information of the bulk nanobubbles, thereby calculating the particle size information of the bulk nanobubbles.

[0019] Furthermore, frequency domain analysis performs a two-dimensional fast Fourier transform on the obtained difference map to acquire the spectral data of the difference image, thereby calculating the image structure function (ISF):

[0020] The expression for the difference graph D(x,y,t,Δt) is:

[0021] D(x,y,t,Δt)=I(x,y,t+Δt)-I(x,y,t)

[0022] In the formula, I(x,y,t) represents the intensity of scattered light and the pixel coordinates (x,y) of the microscopic motion image at time t, and I(x,y,t+Δt) is the microscopic motion image information at time Δt after time t;

[0023] The difference map is subjected to a two-dimensional Fourier transform to obtain the difference map D(u). x ,u y ,Δt):

[0024] |D(u x ,u y ,Δt)| 2 =<|FFT.[ΔI(x,y,Δt)]| 2 >

[0025] Furthermore, one-dimensional processing is achieved by radially averaging different components with the same spatial frequency through data fitting. The equation can be decomposed into three independent functions:

[0026] |D(q,Δt) 2 = A(q)[1-f(q,Δt)]+B(q)

[0027] Here, f(q,Δt) is the intermediate scattering function, which can obtain the motion information of bulk nanobubbles. The diffusion coefficient of the sample is obtained by fitting the intermediate scattering function using the following relationship:

[0028]

[0029] The particle size of bulk nanobubbles was calculated based on the diffusion coefficient Dm of the bulk nanobubbles and the Einstein-Stokes equations.

[0030]

[0031] Among them, K B η is Boltzmann's constant, T is the thermodynamic temperature of the experimental environment (solution), d is the diameter of the bulk nanobubbles, and η is the viscosity coefficient of the solution.

[0032] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0033] (1) The present invention provides a dark field differential dynamic microscopy measurement system and method for characterizing bulk nanobubbles, which can accurately measure the particle size of bulk nanobubbles. At the same time, it greatly reduces the measurement time and instrument cost compared with existing characterization techniques, and achieves efficient and accurate characterization of bulk nanobubbles.

[0034] (2) This invention applies dark-field differential dynamic microscopy to the characterization of bulk nanobubbles, using image processing to acquire motion information of the bulk nanobubbles to characterize particle size. Compared with existing characterization methods, this method lowers the equipment requirements and increases the measurement speed, demonstrating significant technical advantages. Attached Figure Description

[0035] Figure 1 This is a schematic flowchart of a dark-field differential dynamic microscopy method for characterizing bulk nanobubbles according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the overall structure of the dark-field difference dynamic microscopy system in an example of the present invention.

[0037] Figure 3 This is a fitting result diagram of bulk nanobubbles in an embodiment of the present invention. Detailed Implementation

[0038] The specific implementation of the present invention will be further described below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments whose manufacturers are not specified are considered to be conventional products that can be purchased commercially.

[0039] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and do not specifically refer to any order or sequence, nor are they intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0040] Please see Figure 2 This invention provides a dark-field differential dynamic microscopy system for characterizing bulk nanobubbles, comprising an illumination optical path and a measurement optical path. The illumination optical path includes a laser 1, a reflecting mirror 2, and a cylindrical lens 3. The measurement optical path includes a sample cell 4, a microscope objective lens 5, a first lens 6, a second lens 7, a third lens 8, and a CMOS high-speed camera 9. The dark-field differential dynamic microscopy system is used to acquire microscopic motion images.

[0041] A laser 1, a reflector 2, and a cylindrical lens 3 are arranged sequentially on one side of the sample cell 4. The incident light from the laser 1 passes through the reflector 2 and then the cylindrical lens 3. The reflector 2 and the center of the incident light source are on the same axis, and the centers of the reflector 2 and the cylindrical lens 3 are on another axis, and the two axes are perpendicular to each other. The laser 1 is used to generate the incident light beam, and the reflector 2 provides a dark-field lateral illumination mode, allowing the light source to enter from the side of the sample cell 4. The cylindrical lens 3 transforms the point light source of the laser 1 into a line light source that enters the sample cell 4. A microscope objective 5, a first lens 6, a second lens 7, a third lens 8, and a CMOS high-speed camera 9 are arranged sequentially on the other side of the sample cell 4. The centers of the microscope objective 5, the first lens 6, the second lens 7, the third lens 8, and the CMOS high-speed camera 9 are on the same axis and perpendicular to the axis of the cylindrical lens 3, to ensure that the image observed by the CMOS high-speed camera 9 is free of distortion. The first lens 6 is a microscope tube lens with a focal length matching that of the microscope objective lens 5. It is responsible for receiving the light transmitted from the objective lens and focusing the light into the second lens 7. The second lens 7 further magnifies the image passed through the first lens 6 to ensure that only sample information is visible in the field of view of the CMOS high-speed camera 9. The third lens 8 is the imaging lens of the CMOS high-speed camera 9. The light beam passes through the first lens 6, the second lens 7, and the third lens 8, and together with the CMOS high-speed camera 9, completes the microscopic imaging.

[0042] The second lens 7 and the third lens 8, together with the CMOS high-speed camera 9, complete the microscopic imaging. After the system collects the sample motion image, the motion information of the sample is obtained through dark-field differential dynamic microscopy.

[0043] In some embodiments of the present invention, the laser 1 is a laser with a power of 12mW and a wavelength of 635nm; the sample cell 4 is a four-sided transparent glass sample cell, which is filled with samples after ultrasonic cleaning, and the samples are fixed in the sample cell 4 by a sample cell holder; the microscope objective 5 is an infinity working distance objective with a magnification of 20x; the first lens 6 is a microscope tube lens with a focal length matching that of the microscope objective 5; the second lens 7 and the third lens 8 are both biconvex lenses.

[0044] The basic principle of dark-field difference dynamic microscopy is as follows:

[0045] Brownian motion of bulk nanobubbles over a period of time was captured using a dark-field differential dynamic microscopy system. All frames of the video were extracted to obtain a set of images I(x,y,t), where I(x,y,t) represents the scattered light intensity and pixel coordinates (x,y) of the microscopic motion image at time t. Subtracting the first image from the second image until the last image yields a difference map D(x,y,t,Δt), which describes the difference in scattered light intensity between time Δt and the initial time.

[0046] D(x,y,t,Δt)=I(x,y,t+Δt)-I(x,y,t)

[0047] I(x,y,t+Δt) represents the microscopic motion image information at time Δt after time t;

[0048] The difference image retains only the motion information of the particles, eliminating the influence of static noise. Then, a two-dimensional Fourier transform is performed on the difference image to calculate the image structure function (ISF):

[0049] |D(u x ,u y ,Δt)| 2 =<|FFT.[ΔI(x,y,Δt)]| 2 >

[0050] D(u x ,u y Δt) represents the difference image after two-dimensional Fourier transform. FFT[.....] represents Fast Fourier Transform. For each difference image with a fixed time interval, multiple difference images with the same time interval Δt can be averaged over time to reduce systematic errors and improve computational accuracy. ΔI(x,y,Δt) is the image information after time averaging.x ,u y The coordinate system in the frequency domain of the Fourier transform allows for radial averaging of different components with the same spatial frequency, thus achieving one-dimensional processing. u represents the spatial frequency. For ease of processing, the spatial frequency u is replaced by the wave vector q = 2πu, and the equation can be decomposed into three independent functions:

[0051] |D(q,Δt)| 2 = A(q)[1-f(q,Δt)]+B(q)

[0052] Where D(q,Δt) is the frequency domain data of the difference map after a two-dimensional Fourier transform, where the wave vector q replaces the spatial frequency; A(q) is the amplitude of the image signal, which depends on the characteristics of the sample and the imaging system; B(q) is considered as the noise component of the microscopic motion image; and f(q,Δt) is the intermediate scattering function, which can obtain the particle motion information. The wave vector value q is determined by the pixel size of the CMOS high-speed camera and the resolution of the microscopic motion image. Based on the imaging principle of dark-field images, initial fitting values ​​for A(q), B(q), and f(q,Δt) are selected to fit the frequency domain data D(q,Δt) of the difference map, obtaining the amplitude A(q) of the image signal, the noise component B(q) of the camera image, and the intermediate scattering function f(q,Δt). Then, using:

[0053]

[0054] and:

[0055]

[0056] By fitting the relationships between f(q,Δt) and τ(q) as described above, the diffusion coefficient Dm of the bulk nanobubbles can be obtained. Finally, the particle size of the bulk nanobubbles is determined using the Einstein-Stokes equations:

[0057]

[0058] Among them, K B η is Boltzmann's constant, T is the thermodynamic temperature of the experimental environment, d is the diameter of the bulk nanobubbles, and η is the viscosity coefficient of the solution.

[0059] Please see Figure 1 The present invention provides a dark-field differential dynamic microscopy method for characterizing bulk nanobubbles, comprising the following steps:

[0060] Step 1: Generate bulk nanobubbles.

[0061] In some embodiments of the present invention, nanobubbles are generated using an electrochemical method. An electrochemical device is used to electrolyze a salt solution at 20V for 20 minutes to obtain stable bulk nanobubbles. The bulk nanobubbles generated in this embodiment have a diameter of 323.2 nm.

[0062] Step 2: Inject the prepared bulk nanobubbles into sample cell 4 of the dark-field differential dynamic microscopy system.

[0063] Step 3: Turn on laser 1 to emit incident light into sample cell 4, and complete the acquisition of microscopic motion images on CMOS high-speed camera 9.

[0064] Step 4: Perform difference analysis on the acquired microscopic motion images to obtain a difference map; perform a two-dimensional fast Fourier transform on the difference map to obtain the difference map D(u). x u y The frequency domain data D(q,Δt) of the difference map is obtained by replacing the spatial frequency u with the wave vector q.

[0065] Step 5: Select the initial values ​​for fitting based on the imaging principle of dark field images, and fit the frequency domain data D(q,Δt) of the difference map to obtain the amplitude A(q) of the image signal, the noise part B(q) of the camera image, and the intermediate scattering function f(q,Δt).

[0066] Step 6: Linearly fit the obtained intermediate scattering function f(q,Δt) to obtain the diffusion coefficient of the bulk nanobubbles, and calculate the particle size of the bulk nanobubbles using the Einstein-Stokes equation.

[0067] In some embodiments of the present invention, the fitting results of bulk nanobubbles measured by dark-field difference dynamic microscopy are as follows: Figure 3 As shown, based on the principle of dark-field differential dynamic microscopy, the intercept obtained after linear fitting is the diffusion coefficient of the bulk nanobubbles. The fitting result obtained in this embodiment is 326.7 nm, with a relative error of less than 5%.

[0068] In the field of bulk nanobubble characterization, there is currently no characterization technique that offers low equipment requirements, rapid measurement, and visualization capabilities, significantly increasing the cost of measuring instruments and time. Furthermore, it is difficult to accurately measure high-concentration samples, limiting the analyzable sample concentration range. The foregoing embodiments of this invention provide a dark-field differential dynamic microscopy measurement system for bulk nanobubble characterization. Dark-field differential microscopy is an image analysis method that combines scattering sensitivity with microscopic imaging visualization, enabling the acquisition of bubble motion information and integrating theoretical simulation with practical experiments. It significantly lowers the equipment requirements, increases measurement speed, and allows for the measurement of samples with a wider concentration range. This invention is of great significance for the research on bulk nanobubble characterization techniques and stability studies.

[0069] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A dark-field differential dynamic microscopy measurement system for characterizing bulk nanobubbles, characterized in that, Includes the illumination optical path and the measurement optical path: The illumination optical path includes a laser (1), a reflector (2), and a cylindrical lens (3) arranged in sequence. The reflector (2) is used to reflect the incident light emitted by the laser (1) to the cylindrical lens (3). The laser (1), the reflector (2), and the cylindrical lens (3) are located on one side of the sample cell (4). The incident light passes through the reflector (2) and then through the cylindrical lens (3). The center of the reflector (2) and the center of the incident light source are on the same axis. The center of the reflector (2) and the center of the cylindrical lens (3) are on another axis, and the two axes are perpendicular to each other. The measurement optical path is used to acquire microscopic motion images of bulk nanobubbles for frequency domain quantitative analysis. It includes a sample cell (4), a microscope objective (5), a first lens (6), a second lens (7), a third lens (8), and a CMOS high-speed camera (9) arranged in sequence. The microscope objective (5), the first lens (6), the second lens (7), the third lens (8), and the CMOS high-speed camera (9) are located on the other side of the sample cell (4) and on the same axis, which is perpendicular to the axis of the cylindrical lens (3). The first lens (6) is a microscope tube with a focal length that matches that of the microscope objective (5), and the second lens (7) and the third lens (8) are both biconvex lenses.

2. A dark-field differential dynamic microscopy method for characterizing bulk nanobubbles, characterized in that, Using the system of claim 1, the method includes the following steps: Bulk nanobubbles are injected into the sample cell; A laser emits incident light into the sample cell, and a CMOS high-speed camera acquires microscopic motion images. The acquired microscopic motion images are differentially analyzed to obtain a difference map. A two-dimensional fast Fourier transform is then performed on the difference map to obtain the frequency domain data of the difference map. By fitting the frequency domain data of the difference map, the amplitude of the image signal can be obtained. A(q) Noise in camera images B(q) and intermediate scattering function f(q, Δt) ; For intermediate scattering function f(q, Δt) The diffusion coefficient of bulk nanobubbles is obtained by linear fitting, and the particle size of bulk nanobubbles is obtained based on the diffusion coefficient of bulk nanobubbles. The process of performing differential analysis on the acquired microscopic motion images to obtain a difference map, and then performing a two-dimensional fast Fourier transform on the difference map to obtain its frequency domain data, includes: Difference graph D(x, y, t,Δt) The expression is: In the formula, I(x, y, t) This represents the intensity and coordinate position of the scattered light in the microscopic motion image at time t. (x,y) pixels, I (x, y, t+Δt) Distance t After the moment Δt Microscopic motion image information at any given moment; The difference map is obtained by performing a two-dimensional Fourier transform on the difference map. : In the formula, This represents the difference graph after a two-dimensional Fourier transform. FFT[.....] represents the Fast Fourier Transform. This is the image information after time averaging. u x , u y Represents the coordinate system in the frequency domain of the Fourier transform, and the spatial frequency. ; wave vector Replace spatial frequency u ,get: In the formula, wave vector q Frequency domain data of the difference plot after two-dimensional Fourier transform, replacing spatial frequency. A(q) It is the amplitude of the image signal. B(q) This represents the noise component in a microscopic motion image. f(q, Δt) It is the intermediate scattering function; Frequency domain data of the difference plot By performing fitting, the amplitude of the image signal is obtained. A(q) Noise in microscopic motion images B(q) and intermediate scattering function f(q, Δt) The intermediate scattering function is obtained through the following relationship. f(q, Δt) By fitting the data, the diffusion coefficient of the bulk nanobubbles was obtained. ; Based on the diffusion coefficient of bulk nanobubbles The particle size of bulk nanobubbles was calculated using the Einstein-Stokes equations. Among them, K B η is Boltzmann's constant, T is the thermodynamic temperature of the experimental environment, d is the diameter of the bulk nanobubbles, and η is the viscosity coefficient of the solution.

3. The dark-field differential dynamic microscopy method for characterizing bulk nanobubbles according to claim 2, characterized in that, The bulk nanobubbles are generated by an electrochemical method.

4. The dark-field differential dynamic microscopy method for characterizing bulk nanobubbles according to claim 2, characterized in that, Image difference is obtained by subtracting the second to the last images from the first image in a photomicrograph.

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