Nanometer bubble and particle movement cooperative measurement method based on photothermal effect

Abstract

The invention discloses a collaborative measurement method for nano-bubble and particle movement based on a photothermal effect, relates to the technical field of nano-bubble and nano-particle trajectory measurement, and aims to solve the problem that the growth condition of nano-bubbles and particle movement caused by bubble growth are difficult to measure at the same time in the prior art. The laser absorption energy of the nano structure is obtained according to the change of the transmission light intensity of the nano particles, the energy is substituted into the energy equation, and the temperature, the density and the flowing state of the fluid in the forming process of the nano bubble excited by the nano structure are obtained through the lattice Boltzmann method. And meanwhile, the motion trail of the nano-particles controlled by the nano-bubbles is obtained through a dark field imaging method. According to the invention, the size of the nano bubble, the distribution of a flow field around the bubble and the motion trail of particles can be measured at the same time. Movement tracks of multiple particles in a solution can be tracked at the same time, indirect and non-contact measurement can be achieved, and an original sample cannot be damaged.

Description

Technical Field

[0001] This application relates to the field of nanobubble and nanoparticle trajectory measurement technology, specifically a method for the coordinated measurement of nanobubble and particle motion based on photothermal effect. Background Technology

[0002] Plasma nanobubbles are widely used in the manipulation of micro and nanoparticles. Due to the high-speed Marangoni convection at the vapor-liquid interface during nanobubble formation, Marangoni convection offers significantly higher manipulation speeds for micro and nanoparticles compared to other microfluidic particle manipulation techniques such as natural convection and thermophoresis—the manipulation speed can be several orders of magnitude higher. Furthermore, nanobubbles can enable large-scale and multifunctional manipulation of micro and nanoparticles, such as pulling, pushing, rotating, and oscillating. The motion state of particles changes dramatically within the flow field formed by nanobubbles, and accurately acquiring the particle trajectory is fundamental to judging the effectiveness of particle manipulation. Therefore, determining the growth state of nanobubbles and the real-time force conditions on the particles is crucial. Since the formation of nanobubbles and the movement of particles occur simultaneously, it is extremely difficult to simultaneously measure the growth of nanobubbles and the particle movement caused by bubble growth. Summary of the Invention

[0003] The purpose of this invention is to provide a method for the coordinated measurement of nanobubble growth and particle motion based on photothermal effect, addressing the problem in existing technologies that make it difficult to simultaneously measure the growth of nanobubbles and the particle motion caused by bubble growth.

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

[0005] A method for synergistic measurement of nanobubbles and particle motion based on photothermal effect is disclosed. The synergistic measurement method is based on a synergistic measurement device, which includes a pulsed laser, a photodetector, an objective lens, a high-speed camera, and a halogen light source. The high-energy pulsed laser emitted by the pulsed laser is focused by the objective lens and irradiates the nanostructure at the bottom of a microfluidic chamber. The microfluidic chamber contains an aqueous solution. The halogen light source is used to provide illumination for the microfluidic chamber. The photodetector is used to acquire the intensity of the transmitted laser after the pulsed laser irradiates the nanostructure. The high-speed camera is used to monitor the trajectory of the nanoparticles.

[0006] The specific steps of the collaborative measurement method are as follows:

[0007] Step 1: Turn on the pulsed laser, preheat the pulsed laser thoroughly, and then adjust the output power of the pulsed laser so that the nanostructure can heat the surrounding water and generate nanobubbles at this power.

[0008] Step 2: Turn on the photodetector to obtain the transmitted laser power after the pulsed laser irradiates the nanostructure. At the same time, turn on the halogen light source and the high-speed camera. Use the high-speed camera to obtain the trajectory of the nanoparticles and the rotational angular velocity of the nanoparticles. Then, based on the trajectory and rotational angular velocity of the nanoparticles, the motion of the particles can be measured.

[0009] Step 3: Subtract the transmitted laser power from the output power of the pulsed laser; the result is the laser power absorbed by the nanoparticles. ;

[0010] Step 4: Obtain the volume of the nanostructure and utilize laser power. Dividing by the volume of the nanostructure yields the volumetric heat source density of the nanostructure. ;

[0011] Step 5: Increasing the volumetric heat source density of the nanostructure Substituting into the energy equation, we obtain the spatial distribution of temperature. And based on nanostructure and temperature spatial distribution The size of nanobubbles was obtained using the lattice Boltzmann method.

[0012] Furthermore, the specific steps of step 5 are as follows:

[0013] Step 51: Increasing the volumetric heat source density of the nanostructure Substituting the values ​​into the energy equation and solving it using the finite difference method, the temperature of the nanostructure is obtained. and fluid temperature And utilize the temperature of nanostructures and fluid temperature Constructing temperature spatial distribution ;

[0014] Step 52: Obtain the fluid velocity and fluid density based on the intermolecular forces and the distribution function in the lattice Boltzmann method;

[0015] Step 53: Determine if the maximum number of iterations has been reached. If the maximum number of iterations has been reached, proceed to step 54. If the maximum number of iterations has not been reached, proceed to step 55.

[0016] Step 54: Determine the size of the nanobubbles based on the obtained fluid density;

[0017] Step 55: 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 51 to 53 are repeated.

[0018] Furthermore, the energy equation is expressed as:

[0019] ;

[0020] ;

[0021] 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.

[0022] Furthermore, the distribution function is expressed as:

[0023] ;

[0024] ;

[0025] 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.

[0026] Furthermore, the source item Represented as:

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] ;

[0033] ;

[0034] 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.

[0035] Furthermore, the discrete force term Represented as:

[0036] ;

[0037] in, , , For fluid velocity along , , The components in the three directions of the axis.

[0038] Furthermore, the intermolecular forces of the fluid molecules Represented as:

[0039] ;

[0040] ;

[0041] ;

[0042] in, These are the weighting coefficients. It is an intermediate variable.

[0043] Furthermore, the fluid velocity Represented as:

[0044] ;

[0045] ;

[0046] in, It is the distribution function;

[0047] The fluid pressure Represented as:

[0048] ;

[0049] in, This is the universal gas constant. and It is a constant.

[0050] Furthermore, the specific steps for obtaining the rotational angular velocity of the nanoparticles in step 2 are as follows:

[0051] Step 21: Obtain the torque acting on the particle through the distribution function, and then construct the rotation equation of the particle, expressed as:

[0052] ;

[0053] ;

[0054] ;

[0055] in, The angular velocity of the nanoparticles. Let be the rotational inertia of the nanoparticle. For the torque of nanoparticles, Let be the coordinates of the particle's center of mass. For the first nanoparticle boundary The location of each Lagrange node For the first nanoparticle The fluid forces acting on each Lagrange node For unit arc length, For time step,

[0056] Step 22: Discretize the particle rotation equation to obtain the rotational angular velocity of the nanoparticle at various times, expressed as:

[0057] .

[0058] Furthermore, the nanostructure is a precious metal material.

[0059] The beneficial effects of this invention are:

[0060] This application obtains the energy of laser absorption by the nanostructure based on the change in the intensity of transmitted light from nanoparticles, incorporates this energy into the energy equation, and uses the lattice Boltzmann method to obtain the temperature, density, and fluid flow state during the formation of nanobubbles excited by the nanostructure. Simultaneously, dark-field imaging is used to obtain the motion trajectory of the nanoparticles manipulated by the nanobubbles. This application can simultaneously measure the size of the nanobubbles, the distribution of the flow field around the bubbles, and the motion trajectory of the particles. It can simultaneously track the motion trajectories of multiple particles in a solution, enabling indirect, non-contact measurement without damaging the original sample.

[0061] This application is applicable to trajectory tracking of micro / nano particles of different materials and sizes, enabling high-precision, high-temporal-resolution measurements. By measuring the optical absorption of nanostructures, using the lattice Boltzmann method, and dark-field imaging technology, this application has achieved measurements of particle trajectories and rotational angular velocities during the formation of nanoparticles manipulated by nanobubbles. This provides a new measurement method for the flexible manipulation, enrichment, and assembly of nanoparticles. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the collaborative measurement device structure of this application;

[0063] Figure 2 This is a flowchart of the overall measurement method of this application. Detailed Implementation

[0064] It should be noted that, where there is no conflict, the various embodiments disclosed in this application can be combined with each other.

[0065] Specific Implementation Method 1: This implementation method describes a synergistic measurement method for nanobubbles and particle motion based on the photothermal effect. The method is implemented using a synergistic measurement device, which includes: a pulsed laser, a photodetector, a data acquisition and processing integrated computer, an objective lens, a reflector, a high-speed camera, and a halogen light source. The high-energy pulsed laser emitted by the pulsed laser is focused by the objective lens and irradiates a nanostructure fixed at the bottom of the water. The photodetector is used to acquire the intensity of the transmitted laser after the pulsed laser irradiates the nanostructure. Finally, the data acquisition and processing integrated computer records the intensities of the pulsed laser, the incident laser, and the transmitted laser. The reflector is used to adjust the direction of light propagation. The halogen light source provides high-intensity, continuous-spectrum illumination, causing the nanoparticles in the microfluidic chamber to scatter, thus presenting a bright image against a dark background. The high-speed camera is used for nanoparticle imaging and monitoring of nanoparticle trajectories.

[0066] The method includes:

[0067] Step 1: Turn on the pulsed laser and preheat it thoroughly. Then, adjust the output power of the laser so that the nanostructure can heat the surrounding water to generate nanobubbles. Adjust the position of the laser so that it irradiates the nanostructure.

[0068] Step 2: Record the incident laser power using an integrated data acquisition and processing computer. Turn on the photodetector to record the transmission signal after the laser irradiates the nanoparticles, and record the transmitted laser power.

[0069] Step 3: Based on the incident laser power and transmitted laser power from Step 3, subtracting the transmitted laser power from the incident laser power gives the laser power absorbed by the nanoparticles. This portion of the energy is converted into heat by the gold nanostructures, heating the surrounding water to produce nanobubbles.

[0070] Step 4; Based on the laser power absorbed by the nanoparticles in Step 4 , laser power Dividing by the particle volume yields the volumetric heat source density of the nanostructure. The volume of the nanostructure can be obtained based on the fabricated dimensions, and this volume can be incorporated into the energy equation. The temperature of the nanostructure during the formation of nanobubbles can then be solved using the finite difference method. and fluid temperature The energy equations for the water surrounding the nanoparticles and the interior of the nanostructure are as follows:

[0071] ;

[0072] ;

[0073] 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.

[0074] Step 5: Using the nanostructure and fluid temperature obtained in Step 5, the density of the fluid during nanobubble formation is obtained using the lattice Boltzmann method, thereby determining the nanobubble size. Step 6 includes the following specific steps:

[0075] 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:

[0076] ;

[0077] ;

[0078] in For position vectors, For time step. It is the identity matrix. For discrete force terms, For source terms, A diagonal matrix consisting 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.

[0079] Where the transformation matrix The expression is:

[0080] ;

[0081] Furthermore, source phase It has the following form:

[0082] ;

[0083] Furthermore, The specific expression is as follows:

[0084] ;

[0085] ;

[0086] ;

[0087] ;

[0088] ;

[0089] ;

[0090] in and It is a constant. Here is a diagonal matrix containing relaxation factors:

[0091] ;

[0092] in , , , , , , It is a relaxation factor.

[0093] Furthermore, discrete force terms The expression is as follows:

[0094] ;

[0095] 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:

[0096] ;

[0097] 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:

[0098] ;

[0099] in For the speed of sound in a grid, .

[0100] Furthermore, based on intermolecular forces and distribution functions, the velocity and density of the fluid can be obtained, as shown in the following equation:

[0101] ;

[0102] ;

[0103] in For fluid density, The fluid velocity.

[0104] Furthermore, the fluid pressure is obtained through the PR equation of state, which is shown below:

[0105] ;

[0106] in This is the universal gas constant. and It is a constant. The expression is as follows:

[0107] ;

[0108] in It is the critical temperature.

[0109] Step Six: Simultaneously with activating the pulsed laser and photodetector in Steps One and Three, activate the halogen light source and high-speed camera. When nanobubbles form, they induce fluid flow around them, thereby manipulating the movement of the micro / nano particles. When the halogen light source illuminates the nanoparticles, the particles scatter light, creating bright spots against the dark background of the high-speed camera. This scattering by the nanoparticles allows us to obtain their trajectory based on the real-time position of these bright spots, thus enabling the measurement of the nanoparticles' trajectory.

[0110] 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 nanostructure is made of precious metal materials.

[0111] A device for co-measuring the trajectory of nanoparticles manipulated by plasma nanoparticles, wherein the method for measuring the rotational angular velocity of the nanoparticles manipulated by the nanoparticles is as follows:

[0112] ;

[0113] in, It is the angular velocity of the nanoparticles. It is the rotational inertia of the nanoparticles. This refers to the torque of the nanoparticles, where the specific expression for torque is:

[0114] ;

[0115] in These are the coordinates of the fluid points surrounding the particles. It is the first nanoparticle at the boundary The location of each Lagrange node It is the first nanoparticle The fluid forces acting on each Lagrange node are expressed as follows:

[0116] ;

[0117] In summary, by discretizing the particle rotation equation, the angular velocity of the nanoparticles at various moments can be obtained:

[0118] .

[0119] 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 synergistic measurement of nanobubble and particle motion based on photothermal effect, characterized in that, The collaborative measurement method is based on a collaborative measurement device, which includes a pulsed laser, a photodetector, an objective lens, a high-speed camera, and a halogen light source. The high-energy pulsed laser emitted by the pulsed laser is focused by the objective lens and irradiates the nanostructure at the bottom of the microfluidic chamber. The microfluidic chamber contains an aqueous solution. The halogen light source is used to provide illumination for the microfluidic chamber. The photodetector is used to acquire the intensity of the transmitted laser after the pulsed laser irradiates the nanostructure. The high-speed camera is used to monitor the trajectory of the nanoparticles. The specific steps of the collaborative measurement method are as follows: Step 1: Turn on the pulsed laser, preheat the pulsed laser thoroughly, and then adjust the output power of the pulsed laser so that the nanostructure can heat the surrounding water and generate nanobubbles at this power. Step 2: Turn on the photodetector to obtain the transmitted laser power after the pulsed laser irradiates the nanostructure. At the same time, turn on the halogen light source and the high-speed camera. Use the high-speed camera to obtain the trajectory of the nanoparticles and the rotational angular velocity of the nanoparticles. Then, based on the trajectory and rotational angular velocity of the nanoparticles, the motion of the particles can be measured. Step 3: Subtract the transmitted laser power from the output power of the pulsed laser; the result is the laser power absorbed by the nanoparticles. ; Step 4: Obtain the volume of the nanostructure and utilize laser power. Dividing by the volume of the nanostructure yields the volumetric heat source density of the nanostructure. ; Step 5: Increasing the volumetric heat source density of the nanostructure Substituting into the energy equation, we obtain the spatial distribution of temperature. And based on nanostructure and temperature spatial distribution The size of nanobubbles was obtained using the lattice Boltzmann method.

2. The method for synergistic measurement of nanobubble and particle motion based on photothermal effect according to claim 1, characterized in that, The specific steps of step 5 are as follows: Step 51: Increasing the volumetric heat source density of the nanostructure Substituting the values ​​into the energy equation and solving it using the finite difference method, the temperature of the nanostructure is obtained. and fluid temperature And utilize the temperature of nanostructures and fluid temperature Constructing temperature spatial distribution ; Step 52: Obtain the fluid velocity and fluid density based on the intermolecular forces and the distribution function in the lattice Boltzmann method; Step 53: Determine if the maximum number of iterations has been reached. If the maximum number of iterations has been reached, proceed to step 54. If the maximum number of iterations has not been reached, proceed to step 55. Step 54: Determine the size of the nanobubbles based on the obtained fluid density; Step 55: 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 51 to 53 are repeated.

3. The method for synergistic measurement of nanobubble and particle motion based on photothermal effect according to 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 synergistic measurement of nanobubble and particle motion based on photothermal effect according to 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 synergistic measurement of nanobubble and particle motion based on photothermal effect according to 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 synergistic measurement of nanobubble and particle motion based on photothermal effect according to 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 synergistic measurement of nanobubble and particle motion based on photothermal effect according to 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 synergistic measurement of nanobubble and particle motion based on photothermal effect according to claim 7, characterized in that, The fluid velocity Represented as: ； ； in, It is the distribution function; The fluid pressure Represented as: ； in, This is the universal gas constant. and It is a constant.

9. The method for synergistic measurement of nanobubble and particle motion based on photothermal effect according to claim 8, characterized in that, The specific steps for obtaining the rotational angular velocity of the nanoparticles in step 2 are as follows: Step 21: Obtain the torque acting on the particle through the distribution function, and then construct the rotation equation of the particle, expressed as: ； ； ； in, The angular velocity of the nanoparticles. Let be the rotational inertia of the nanoparticle. For the torque of nanoparticles, Let be the coordinates of the particle's center of mass. For the first nanoparticle boundary The location of each Lagrange node For the first nanoparticle The fluid forces acting on each Lagrange node For unit arc length, For time step, Step 22: Discretize the particle rotation equation to obtain the rotational angular velocity of the nanoparticle at various times, expressed as: 。 10. The method for synergistic measurement of nanobubble and particle motion based on photothermal effect according to claim 1, characterized in that, The nanostructure is a precious metal material.

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