Nanometer bubble temperature, pressure and size measuring method based on laser extinction method

Abstract

The invention discloses a nano bubble temperature, pressure and size measurement method based on a laser extinction method, relates to the technical field of nano bubble photo-thermal property measurement, and aims to solve the problem that the temperature, the pressure and the size in a bubble cannot be measured at the same time in a nano bubble forming process in an existing method. According to the method, the laser absorption energy of the nano-particles is obtained according to the change of the transmission light intensity of the nano-particles, the energy is substituted into the energy equation, the temperature, the density, the pressure and the size in the nano-bubble forming process are obtained at the same time through the lattice Boltzmann method, and therefore measurement of the photo-thermal physical property parameters of the nano-bubbles is completed.

Description

Technical Field

[0001] This application relates to the field of photothermal property measurement technology of nanobubbles, specifically a method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction. Background Technology

[0002] Plasmonic nanobubbles are formed by photothermal phenomena generated when plasmonic materials are excited by resonant wavelength lasers. Due to their unique photothermal and optical properties, plasmonic nanobubbles have been widely studied in fields such as microfabrication, micromanipulation, robotic propulsion, molecular enrichment and sensing, clinical treatment, and solar vapor generation. Based on these promising applications, researchers have conducted in-depth and systematic explorations into the formation mechanism of plasmonic nanobubbles. Early methods for capturing bubble growth dynamics included dark-field imaging, hydrophone detection, and transparency testing. However, the nucleation and growth process of bubbles involves dramatic morphological changes, molecular-nanoscale phenomena (such as surface chemistry, curvature, wetting conditions, and surface tension), and other factors (such as pulse duration, nanostructure size, laser intensity, and interfacial thermal resistance), making the growth mechanism of nanobubbles extremely complex. Furthermore, because the nucleation and growth of nanobubbles occur at the nanoscale, current techniques cannot simultaneously measure the internal temperature, pressure, and size of the bubbles during the formation process. Summary of the Invention

[0003] The purpose of this invention is to provide a method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction, addressing the problem that existing methods cannot simultaneously measure the temperature, pressure, and size of nanobubbles during the formation process.

[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0005] A method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction, wherein the measurement method is implemented based on a measuring device, the measuring device comprising: a pulsed laser, a CCD camera, an objective lens, and an avalanche photodetector;

[0006] The laser emitted by the pulsed laser is focused by the objective lens and then irradiates the aqueous solution containing nanoparticles. The CCD camera is used to determine whether the laser irradiates the nanoparticles, and the avalanche photodetector is used to receive the transmission signal after the laser irradiates the nanoparticles.

[0007] Step 1: Turn on the pulsed laser and preheat it thoroughly. Then, adjust the output power of the pulsed laser, i.e. the incident laser power, so that the nanoparticles can heat the surrounding water and generate nanobubbles at this power.

[0008] Step 2: Imaging the laser spot in real time using a CCD camera, while adjusting the position of the laser spot to make it coincide with the nanoparticles. When there is a bright spot in the image, it means that the laser has irradiated the nanoparticles.

[0009] Step 3: Turn on the avalanche photodetector and use it to obtain the transmitted laser power after the nanoparticles are irradiated by the laser.

[0010] Step 4: Subtract the transmitted laser power from the incident laser power to obtain the laser power absorbed by the nanoparticles from the incident laser. ;

[0011] Step 5: Obtain the volume of the nanoparticles and use laser power Divide by the volume of the nanoparticles to obtain the volumetric heat source density of the nanoparticles. ;

[0012] Step 6: Calculate the volumetric heat source density of the nanoparticles. Substituting into the energy equation, we obtain the temperature of the nanoparticles. and fluid temperature And based on the temperature of the nanoparticles and fluid temperature The fluid density and fluid pressure during the formation of nanobubbles were obtained using the lattice Boltzmann method, and the size of the nanobubbles was finally obtained using the fluid density and fluid pressure.

[0013] Furthermore, the specific steps of step 6 are as follows:

[0014] Step 61: Calculate the volumetric heat source density of the nanoparticles. Substituting the values ​​into the energy equation and solving it using the finite difference method, the temperature of the nanoparticles is obtained. and fluid temperature And utilize the temperature of nanoparticles and fluid temperature Constructing temperature spatial distribution ;

[0015] Step 62: Obtain the fluid velocity and fluid density based on the intermolecular forces and the distribution function in the lattice Boltzmann method;

[0016] Step 63: Determine if the maximum number of iterations has been reached. If the maximum number of iterations has been reached, proceed to step 64. If the maximum number of iterations has not been reached, proceed to step 65.

[0017] Step 64: Determine the nanobubble size based on the obtained fluid density;

[0018] Step 65: Based on temperature spatial distribution The fluid pressure is obtained using the PR equation of state, and the fluid pressure and fluid velocity are used as the fluid pressure and fluid velocity in the energy equation and distribution function, respectively. Steps 61 to 63 are repeated.

[0019] Furthermore, the energy equation is expressed as:

[0020] ;

[0021] ;

[0022] in, , , These are fluid density, thermal conductivity, and specific heat capacity, respectively. For time, subscript Precious metal material, subscript It is an aqueous solution. For fluid pressure, The fluid velocity.

[0023] Furthermore, the distribution function is expressed as:

[0024] ;

[0025] ;

[0026] in, For position vectors, For time step, It is the identity matrix. For discrete force terms, For source terms, It is a diagonal matrix composed of relaxation parameters. , , , Both are distribution functions. Let be the equilibrium state distribution function. For discrete velocities.

[0027] Furthermore, the source item Represented as:

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] ;

[0033] ;

[0034] ;

[0035] in, , , , , , for The amount, For the speed of sound in a grid, and For coefficients, The coefficient of intermolecular forces. It is a pseudopotential function. The forces between fluid molecules. , , They are respectively Along , , The components in the three directions of the axis.

[0036] Furthermore, the discrete force term Represented as:

[0037] ;

[0038] in, , , For fluid velocity along , , The components in the three directions of the axis.

[0039] Furthermore, the intermolecular forces of the fluid molecules Represented as:

[0040] ;

[0041] ;

[0042] ;

[0043] in, These are the weighting coefficients. It is an intermediate variable.

[0044] Furthermore, the fluid velocity Represented as:

[0045] ;

[0046] ;

[0047] in, is the distribution function.

[0048] Furthermore, the fluid pressure Represented as:

[0049] ;

[0050] in, This is the universal gas constant. and It is a constant.

[0051] Furthermore, the nanoparticles are precious metal materials.

[0052] The beneficial effects of this invention are:

[0053] This application obtains the energy of laser absorbed by nanoparticles based on the change in the intensity of transmitted light, incorporates it into the energy equation, and then uses the lattice Boltzmann method to simultaneously obtain the temperature, density, pressure and size of the nanobubble formation process, thereby completing the measurement of the photothermal physical parameters of the nanobubble.

[0054] This application can simultaneously measure the photothermal properties of nanobubbles, reducing computational costs while improving computational efficiency. Furthermore, this application can flexibly adjust the temporal and spatial resolution based on the mesh division in the lattice Boltzmann method. It can also obtain the real-time size of nanobubbles based on fluid density distribution analysis, thereby enabling the detection of nanobubbles. By measuring the optical absorption of gold nanoparticles and using the lattice Boltzmann method, this application achieves simultaneous measurement of transient temperature, density, pressure, and size during the formation of nanobubbles. This provides a new technical means for measuring the photothermal properties of nanobubbles and for their application in photothermal diagnostic and therapeutic integration. Attached Figure Description

[0055] Figure 1 This is a structural diagram of the measuring device used in this application;

[0056] Figure 2 This is a flowchart of the measurement method in this application. Detailed Implementation

[0057] It should be noted that, where there is no conflict, the various embodiments disclosed in this application can be combined with each other.

[0058] Specific Implementation Method 1: This implementation method describes a method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction. The method is implemented using a measuring device, which includes a pulsed laser, a CCD camera, an objective lens, an avalanche photodetector, and a data acquisition and processing integrated computer. Figure 1 As shown, the laser emitted by the pulsed laser is first reflected by a mirror and then focused into a smaller spot by an objective lens. A CCD camera can monitor the position of the laser spot in real time through the reflected light and can detect whether the laser spot is illuminating the nanoparticles. After the laser irradiates the nanoparticles, the intensity of the transmitted laser is obtained by an avalanche photodetector, and the intensity of the incident laser and the transmitted laser are recorded in real time by an integrated computer for data acquisition and processing.

[0059] The method includes the following steps:

[0060] Step 1: Turn on the pulsed laser, preheat the laser thoroughly, and adjust the output power of the laser so that the nanoparticles can heat the surrounding water to generate nanobubbles. Record the incident laser power using a data acquisition and processing integrated computer.

[0061] The input current of the pulsed laser is changed by an integrated computer for data acquisition and processing to make it emit laser power of sufficient intensity, and the incident laser power is recorded.

[0062] Step 2: Imaging the laser spot in real time using a CCD camera, while adjusting the position of the laser spot to make it coincide with the nanoparticles. When there are obvious bright spots in the image, it indicates that the laser has irradiated the nanoparticles.

[0063] Step 3: Turn on the avalanche photodetector to record the projected signal after the laser irradiates the nanoparticles, and record the transmitted laser power.

[0064] Step 4: Based on the incident laser power and transmitted laser power from Steps 1 and 3, subtract the transmitted laser power from the incident laser power to obtain the laser power absorbed by the nanoparticles from the incident laser. This portion of the energy is converted into heat by the gold nanoparticles, heating the surrounding water to produce nanobubbles.

[0065] Step 5; Based on the laser power absorbed by the nanoparticles in Step 4 , laser power Dividing by the particle's volume gives the particle's volumetric heat source density. The energy equations are then substituted into the energy equations, and the temperature during the formation of nanobubbles is solved using the finite difference method. The energy equations for the water surrounding the nanoparticles and the interior of the nanoparticles are as follows:

[0066] ;

[0067] ;

[0068] in , , These are density, thermal conductivity, and specific heat capacity, respectively, indicated by subscripts. and These represent water and gold, respectively. The spatial temperature distribution across the entire geometric domain can be obtained based on the temperature of the nanostructure and the fluid temperature. , Represents time, Represents pressure, Represents fluid velocity.

[0069] Step Six: Using the temperatures of the nanoparticles and fluid obtained in Step Five, the density and pressure of the fluid during the formation of nanobubbles are obtained using the lattice Boltzmann method, thereby determining the size of the nanobubbles. The specific process of Step Six includes:

[0070] The distribution function is used to simulate the interactions between fluid molecules. The macroscopic motion state of the fluid is obtained through the "collision" and "diffusion" steps of the distribution function, that is, through its iterative update. The update equation of the distribution function is as follows:

[0071] ;

[0072] ;

[0073] in For position vectors, For time step. It is the identity matrix. For discrete force terms, For source terms, It is a diagonal matrix composed of relaxation parameters. , , , Both are distribution functions, and they are connected by a transformation matrix. accomplish, = , = , It is by The matrix formed It is by The matrix formed This is the equilibrium state distribution function.

[0074] The transformation matrix The expression is:

[0075] ;

[0076] Furthermore, source phase It has the following form:

[0077] ;

[0078] Furthermore, The specific expression is as follows:

[0079] ;

[0080] ;

[0081] ;

[0082] ;

[0083] ;

[0084] ;

[0085] in and It is a constant. Here is a diagonal matrix containing relaxation factors:

[0086] ;

[0087] in , , , , , , It is a relaxation factor.

[0088] Furthermore, discrete force terms The expression is as follows:

[0089] ;

[0090] in The intermolecular forces of the fluid flow along , , The components in the three directions of the axis are , , Fluid molecules move under this force, and its specific expression is as follows:

[0091] ;

[0092] in The coefficient of intermolecular forces. These are weighting coefficients. It is a discrete velocity. It is a pseudopotential function, which is obtained by the following formula:

[0093] ;

[0094] in For the speed of sound in a grid, .

[0095] Furthermore, based on intermolecular forces and distribution functions, the velocity and density of the fluid can be obtained, as shown in the following equation:

[0096] ;

[0097] ;

[0098] in For fluid density, The fluid velocity.

[0099] Furthermore, the fluid pressure is obtained through the PR equation of state, which is shown below:

[0100] ;

[0101] in This is the universal gas constant. and It is a constant. The expression is as follows:

[0102] ;

[0103] in This is the critical temperature. In summary, step six allows for real-time updates of temperature, pressure, and density at each moment during the formation of nanobubbles. The size of the nanobubbles can be obtained step by step based on the density, thus enabling real-time measurement of the nanobubbles.

[0104] In this embodiment, the pulse width of the pulsed laser is between 100 fs and 100 ns, the pulsed laser power is between 3 mW and 200 mW, and the diameter of the nanoparticles is between 10 nm and 100 nm.

[0105] It should be noted that the specific embodiments are merely explanations and illustrations of the technical solution of the present invention and should not be used to limit the scope of protection. Any modifications made in accordance with the claims and specification of the present invention that are only partial should still fall within the protection scope of the present invention.

Claims

1. A method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction, characterized in that... The measurement method is based on a measurement device, which includes: a pulsed laser, a CCD camera, an objective lens, and an avalanche photodetector. The laser emitted by the pulsed laser is focused by the objective lens and then irradiates the aqueous solution containing nanoparticles. The CCD camera is used to determine whether the laser irradiates the nanoparticles, and the avalanche photodetector is used to receive the transmission signal after the laser irradiates the nanoparticles. Step 1: Turn on the pulsed laser and preheat it thoroughly. Then, adjust the output power of the pulsed laser, i.e. the incident laser power, so that the nanoparticles can heat the surrounding water and generate nanobubbles at this power. Step 2: Imaging the laser spot in real time using a CCD camera, while adjusting the position of the laser spot to make it coincide with the nanoparticles. When there is a bright spot in the image, it means that the laser has irradiated the nanoparticles. Step 3: Turn on the avalanche photodetector and use it to obtain the transmitted laser power after the nanoparticles are irradiated by the laser. Step 4: Subtract the transmitted laser power from the incident laser power to obtain the laser power absorbed by the nanoparticles from the incident laser. ; Step 5: Obtain the volume of the nanoparticles and use laser power Divide by the volume of the nanoparticles to obtain the volumetric heat source density of the nanoparticles. ; Step 6: Calculate the volumetric heat source density of the nanoparticles. Substituting into the energy equation, we obtain the temperature of the nanoparticles. and fluid temperature And based on the temperature of the nanoparticles and fluid temperature The fluid density and fluid pressure during the formation of nanobubbles were obtained using the lattice Boltzmann method, and the size of the nanobubbles was finally obtained using the fluid density and fluid pressure.

2. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 1, characterized in that, The specific steps of step 6 are as follows: Step 61: Calculate the volumetric heat source density of the nanoparticles. Substituting the values ​​into the energy equation and solving it using the finite difference method, the temperature of the nanoparticles is obtained. and fluid temperature And utilize the temperature of nanoparticles and fluid temperature Constructing temperature spatial distribution ; Step 62: Obtain the fluid velocity and fluid density based on the intermolecular forces and the distribution function in the lattice Boltzmann method; Step 63: Determine if the maximum number of iterations has been reached. If the maximum number of iterations has been reached, proceed to step 64. If the maximum number of iterations has not been reached, proceed to step 65. Step 64: Determine the nanobubble size based on the obtained fluid density; Step 65: Based on temperature spatial distribution The fluid pressure is obtained using the PR equation of state, and the fluid pressure and fluid velocity are used as the fluid pressure and fluid velocity in the energy equation and distribution function, respectively. Steps 61 to 63 are repeated.

3. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 2, characterized in that, The energy equation is expressed as: ； ； in, , , These are fluid density, thermal conductivity, and specific heat capacity, respectively. For time, subscript Precious metal material, subscript It is an aqueous solution. For fluid pressure, The fluid velocity.

4. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 3, characterized in that, The distribution function is expressed as: ； ； in, For position vectors, For time step, It is the identity matrix. For discrete force terms, For source terms, It is a diagonal matrix composed of relaxation parameters. , , , Both are distribution functions. Let be the equilibrium state distribution function. For discrete velocities.

5. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 4, characterized in that, The source item Represented as: ； ； ； ； ； ； ； in, , , , , , for The amount, For the speed of sound in a grid, and For coefficients, The coefficient of intermolecular forces. It is a pseudopotential function. The forces between fluid molecules. , , They are respectively Along , , The components in the three directions of the axis.

6. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 5, characterized in that, The discrete force term Represented as: ； in, , , For fluid velocity along , , The components in the three directions of the axis.

7. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 6, characterized in that, The intermolecular forces of the fluid Represented as: ； ； ； in, These are the weighting coefficients. It is an intermediate variable.

8. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 7, characterized in that, The fluid velocity Represented as: ； ； in, is the distribution function.

9. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 8, characterized in that, The fluid pressure Represented as: ； in, This is the universal gas constant. and It is a constant.

10. The method for measuring the temperature, pressure, and size of nanobubbles based on laser extinction as described in claim 1, characterized in that, The nanoparticles are precious metal materials.

Images