A method for generating a specific pattern of particle adsorption based on microfluidic bubble generation

Abstract

The application discloses a method for generating a specific pattern by inducing particle adsorption based on micro-fluidic bubbles, and belongs to the fields of micro-fluidics and fluid mechanics.The method comprises the following steps: obtaining three-dimensional flow field data containing spatial position, corresponding velocity and phase field information; performing numerical simulation on particle motion based on the three-dimensional flow field data, calculating gravity, buoyancy, viscous resistance, van der Waals attraction, electrostatic repulsion, friction, wall support force and capillary force acting on the particle by judging the contact state of the particle with a wall surface and a gas-liquid interface; constructing a particle motion equation under the combined action of the above eight forces, updating the particle position and obtaining a migration track by using a time advancing method according to the motion equation; when the spherical surface of the particle is in contact with the solid wall surface, if the movement speed of the particle in the solid wall surface is consistent with the movement speed of the solid wall surface, it is determined that the particle has completed the transition from free motion to stable deposition, and the position of the particle at this time is recorded as a deposition site; and all the deposition sites are gathered into a specific pattern.

Description

Technical Field

[0001] This invention belongs to the fields of microfluidics and fluid mechanics, and relates to a method for regulating the adsorption and distribution of particles on the solid wall surface of a pipe by generating moving bubbles within a microfluidic chip. Background Technology

[0002] The phenomenon of particles adsorbing onto solid surfaces in confined channels due to bubble motion is common in nature and industry, such as particle enrichment during cardiovascular embolism and contaminant capture in water treatment. Therefore, understanding bubble-driven particle adsorption behavior is of great significance for related applications. Existing research mainly focuses on two-dimensional flow conditions, exploring the influence of flow parameters on particle adsorption; however, in three-dimensional confined channels, the interaction between bubbles and particles is more complex, and the coupling effects of interface deformation, wetting properties, and local flow field structure have not been fully revealed, and its potential pattern-building capability also lacks systematic research.

[0003] In traditional dip coating methods, the adsorption pattern of particles is usually dominated by the relationship between the liquid film thickness and the particle size. The adsorption strips are arranged perpendicular to the direction of liquid film movement and mainly occur in the interfacial contraction region. Although this method is widely used to construct regular patterns, the adsorption strips are always perpendicular to the flow direction. Due to the limitations of gravity and capillary interaction, it is not easy to achieve controllable and oriented pattern construction in microscale confined channels.

[0004] With the development of microfluidic technology, microscale flow environments provide a high-precision and repeatable platform for studying bubble-driven particle adsorption behavior. Among these, microbubble generation based on flow focusing structures is characterized by its simplicity and uniform size. By adjusting the gas-liquid flow ratio, channel geometry, and liquid properties, stable control over bubble size, generation frequency, and trajectory can be achieved. The advantages of microfluidic systems in flow field regulation and interface morphology control give them the potential to construct controlled particle adsorption patterns. However, existing microfluidic platforms are mostly used for traditional particle capture, separation, or enrichment, and their ability to construct particle patterns has not been fully utilized. Furthermore, there is a lack of mature technologies capable of precisely inducing particles to align in specific directions.

[0005] Existing methods have limited control over the direction of particle adsorption, making it difficult to achieve diverse pattern construction within three-dimensional microchannels. Therefore, it is necessary to propose a particle adsorption control method based on microfluidic bubble generation. By precisely controlling the formation and movement of bubbles, this method can overcome the limitations of traditional dip coating and two-dimensional flow conditions, enabling particles to be adsorbed along the direction of liquid film movement. This further enhances the controllability and richness of particle patterns, thus allowing applications in multiple fields such as micro / nano structure fabrication and biosensor preparation. Summary of the Invention

[0006] The purpose of this invention is to provide a method for inducing particle adsorption into specific patterns based on microfluidic bubble generation. This method acquires three-dimensional flow field data and performs numerical simulations of the contact states between particles and the wall surface and the gas-liquid interface. It calculates various forces acting on the particles, including gravity, buoyancy, viscous drag, van der Waals attraction, electrostatic repulsion, friction, wall support force, and capillary force. A particle motion equation is constructed, and the particle position is updated over time to obtain the particle migration trajectory. When a particle completes the transition from free motion to stable deposition, its position is recorded as the deposition point, ultimately forming a specific pattern. Furthermore, this invention also involves using a PDMS chip and microfluidic technology to control the liquid film morphology on the lower surface of the bubble to adjust the particle deposition position on the wall surface and precisely generate particle adsorption patterns. This invention can be applied to the fabrication of micro / nano-scale particle arrangement and surface patterning.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention discloses a method for inducing particle adsorption of specific patterns based on microfluidic bubble generation, comprising the following steps:

[0009] Step 1: Obtain three-dimensional flow field data containing spatial position, corresponding velocity, and phase field information; perform numerical simulation of particle motion based on the three-dimensional flow field data, and calculate the gravity, buoyancy, viscous drag, van der Waals attraction, electrostatic repulsion, friction, wall support force, and capillary force acting on the particles by judging the contact state between the particles and the wall and the gas-liquid interface (including free motion state, wall contact state, pure gas-liquid interface contact state, and gas-liquid interface and solid wall double contact state); construct the particle motion equations acting on the above eight forces, and update the particle position and obtain the migration trajectory by using a time-progression method according to the obtained motion equations.

[0010] Step 2: When the spherical surface of the particle comes into contact with the solid wall, i.e., in a wall-contact state or a dual-contact state between the gas-liquid interface and the solid wall, if the particle's velocity within the solid wall is the same as its velocity on the solid wall, then the particle has completed the transition from free motion to stable deposition, and its position at this moment is recorded as the deposition site. All deposition sites converge to form a specific pattern.

[0011] The gravity G mentioned in step one is:

[0012]

[0013] Buoyancy F b :

[0014]

[0015] Viscous resistance F D :

[0016]

[0017] in:

[0018] Particle radius

[0019] Particle density, 1.05 g / cm³ 3

[0020] The fluid density is 1.05 g / cm³. 3

[0021] It is the gravitational acceleration vector. = (0, 0, - )

[0022] For fluid dynamic viscosity

[0023] Particle velocity vector

[0024] The fluid velocity vector at the center of the particle.

[0025] Van der Waals Attraction F VdW :

[0026]

[0027] in:

[0028] Hamaker constant

[0029] The shortest distance between the particle surface and the wall.

[0030] electrostatic repulsion F ele :

[0031]

[0032] in:

[0033] Relative permittivity

[0034] The vacuum permittivity

[0035] Debye length

[0036] , Zeta potentials of the particle and the glass wall, respectively.

[0037] Wall support force F N :

[0038]

[0039] Friction force F f :

[0040]

[0041] in:

[0042] coefficient of friction

[0043] capillary force :

[0044]

[0045] in:

[0046] The gas-liquid interfacial tension coefficient

[0047] For fill corner

[0048] Let be the unit vector from the center of the circle where the gas-liquid interface contacts the particle to the center of the particle sphere.

[0049] The free motion state described in step one:

[0050] When a particle is completely submerged in the liquid phase and its spherical surface is neither in contact with the solid wall below nor with the gas-liquid interface above, it is considered to be in a state of free motion. At this time, the particle is mainly subjected to three forces: gravity G (vertically downward), buoyancy F (vertically upward). b And the viscous drag F, which is proportional to the relative velocity of the particles and the fluid. D Its equation of motion is as follows:

[0051]

[0052] Among them, particle mass:

[0053] In this state, the motion of the particles is entirely determined by the flow field and their own settling tendency. Based on the obtained particle motion equations, the acceleration of the particles is calculated. Using the velocity and acceleration at the current moment, the particle position at the next moment is determined according to the set time step, thus obtaining the particle's migration trajectory.

[0054] The pure gas-liquid interface contact state described in step one:

[0055] When a particle, during its motion, detects that its spherical surface is only in contact with the gas-liquid interface within the physical field, and the bottom of the particle's spherical surface does not touch the solid wall, it enters a pure gas-liquid interface contact state. The gas-liquid interface is considered as an impenetrable but slippery geometric constraint surface. In this state, complex capillary forces are ignored. The particle's gravity G and buoyancy F... b and viscous resistance F D The resultant force is denoted as F. total The component perpendicular to the interface is balanced by the rigid reaction force of the interface; while the sum of the tangential components of all forces drives the particle to slide along the gas-liquid interface. This resultant tangential force is expressed as:

[0056]

[0057] Where n is the normal vector of the gas-liquid interface. Therefore, the particle motion equation is as follows:

[0058]

[0059] In this state, the particles move along the tangential plane of the gas-liquid interface. Based on the obtained particle motion equation, the acceleration of the particle motion is calculated. Using the velocity and acceleration at the current moment, the particle position at the next moment is determined according to the set time step, thus obtaining the particle's migration trajectory.

[0060] The wall contact state described in steps one and two:

[0061] When the spherical bottom of the particle is low enough to contact the solid wall, it is considered to be in wall contact. This is in addition to gravity G and buoyancy F. b and viscous resistance F D In addition, particles will be subjected to complex surface forces from the wall: including intermolecular van der Waals forces F that vary with distance. vdW The electrostatic repulsion force F generated by the surface charge ele And the sliding friction force F that prevents the particles from sliding along the wall. f and the supporting force F provided by the solid wall. N The net force acting on it is denoted as F. total Therefore, the equation of motion for the particles is as follows:

[0062]

[0063] In this state, the particles move near the wall. Based on the obtained particle motion equations, the particle acceleration is calculated. Using the current velocity and acceleration, and according to a set time step, the particle position at the next moment is determined, thus obtaining the particle's migration trajectory. In the bubble reference frame, when the particle's velocity within the solid wall matches the velocity of the solid wall, the particle is considered to have completed the transition from free motion to stable deposition. This position is recorded as the deposition site, and all deposition points converge to form a specific pattern.

[0064] The gas-liquid interface and solid wall surface in double contact state described in steps one and two:

[0065] When a particle's spherical surface is simultaneously identified as being in contact with both a solid wall and a gas-liquid interface, it is determined to be in a state of dual contact between the gas-liquid interface and the solid wall. In this state, the particle is "compressed" between the solid wall and the gas-liquid interface, causing significant deformation of the gas-liquid interface and thus generating a significant capillary force F. γ Furthermore, a contact circle exists between the gas-liquid interface and the particle. Using discrete point data of the gas-liquid interface at a distance of no more than 20 μm from the normal direction of the particle's sphere, a contact plane between the particle and the gas-liquid interface is fitted. The center of the particle's sphere is then vertically projected onto this fitted plane to obtain the center of the contact circle. This 20 μm threshold range ensures that, considering local interface curvature and numerical discretization errors, the selected data points can effectively characterize the geometric features of the contact area. The capillary force F... γ The direction of the force is from the center of the contact circle to the center of the particle, and its size is related to the interfacial tension coefficient, the particle radius, and the contact angle between the particle and the gas-liquid interface. In this state, the force on the particle is the most comprehensive of all states (e.g., ...). Figure 1 As shown in a), gravity G and buoyancy F need to be considered simultaneously. b Viscous resistance F D Wall van der Waals force F VdW electrostatic force F ele Friction force F f Wall support force F N And the crucial capillary force F γ The net force acting on it is denoted as F. total Therefore, the equation of motion for the particles is as follows:

[0066]

[0067] In this state, the particles are trapped between the gas-liquid interface and the solid wall. Based on the obtained particle motion equations, the particle acceleration is calculated. Using the current velocity and acceleration, and according to a set time step, the particle position at the next moment is determined, thus obtaining the particle's migration trajectory. In the bubble reference frame, when the particle's velocity within the solid wall matches the velocity of the solid wall, the particle is considered to have completed the transition from free motion to stable deposition. This position is recorded as the deposition site, and all deposition points converge to form a specific pattern.

[0068] The method for creating a specific pattern by adsorbing particles includes the following steps:

[0069] S1. A PDMS chip layer is prepared by casting PDMS material in an acrylic mold, and then bonded to a glass slide after being treated by a plasma cleaner to obtain a microfluidic chip.

[0070] S2. Air, solution, and particulate suspension are injected into the microfluidic chip via an injection pump. Bubbles are stably generated by the chip's flow focusing structure, and the moving bubble liquid film induces the particles to be adsorbed on the lower wall of the channel.

[0071] S3. By adjusting the speed of bubble movement, the morphology of the liquid film on the lower surface of the bubble is controlled, and the relative size relationship between the diameter of the injected particles and the thickness of the liquid film on the lower surface is adjusted, so as to control the particles to be deposited on the wall at predetermined points to form an adsorption pattern.

[0072] S4. Using a microscope, the observation plane is locked on the area near the wall of the channel. A high-speed camera is used to continuously acquire video and record images of the bubble movement and particle adsorption process. After waiting for a period of time, the particle adsorption pattern on the lower wall of the pipe along the direction of bubble liquid film movement is obtained.

[0073] Beneficial effects:

[0074] 1. The present invention discloses a method for inducing particle adsorption of specific patterns based on microfluidic bubble generation, which unifies particle force analysis, local liquid film thickness, interface morphology and multi-force field coupling within the same calculation framework, thereby achieving accurate prediction of adsorption patterns driven by multiple physical factors.

[0075] 2. The present invention discloses a method for inducing particle adsorption of specific patterns based on microfluidic bubble generation. It utilizes the interaction between the bubble liquid film and particles in the microfluidic channel to achieve directional adsorption of particles on the wall of the microchannel, so that the particles can form regular and repeatable strip patterns along the direction of bubble movement.

[0076] 3. This invention discloses a method for inducing particle adsorption into specific patterns based on microfluidic bubble generation. It utilizes a PDMS chip and microfluidic technology to control the liquid film morphology on the lower surface of the bubbles. By adjusting parameters such as bubble liquid film thickness and particle diameter, the distribution morphology of particle strips can be flexibly controlled, exhibiting high controllability and precisely generating particle adsorption patterns. This invention can be applied to the fabrication of micro / nano-scale particle arrangement and surface patterning.

[0077] 4. This invention discloses a method for inducing particle adsorption into specific patterns based on microfluidic bubble generation. By acquiring three-dimensional flow field data and combining it with numerical simulations of the contact states between particles and the wall surface and the gas-liquid interface, various forces acting on the particles are calculated, including gravity, buoyancy, viscous drag, van der Waals attraction, electrostatic repulsion, friction, wall support force, and capillary force. A particle motion equation is constructed, and the particle position is updated over time to obtain the particle migration trajectory. When a particle completes the transition from free motion to stable deposition, its position is recorded as the deposition point, ultimately forming a specific pattern. Attached Figure Description

[0078] Figure 1 Force and near-wall data were obtained from numerical simulations. (a) Schematic diagram of forces acting on near-wall particles; (b) Overlay image, including the velocity field (upper part) and the bubble in the near-wall region. The lower part shows the shape of the gas-liquid interface, and this data is used for particle force calculation. The solid red ellipse line represents the projected shape of the bubble on the xOy plane;

[0079] Figure 2 Predicted near-wall trajectories and deposition locations of particles are derived through force calculations. 5 μm particles, uniformly distributed in the y-direction, are released in front of the bubble; their trajectories and particle velocities are displayed in the bubble reference frame. Asterisks indicate deposition locations. The solid blue ellipse represents the bubble's projection onto the xOy plane.

[0080] Figure 3 Bubbles in capillary number The adsorption pattern formed by inducing the adsorption of 5 μm particles. Detailed Implementation

[0081] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0082] Example 1:

[0083] This embodiment uses the kinetic equation method described in the invention to calculate the trajectory of a 5 µm diameter particle in a liquid film, in order to predict its deposition position distribution on the solid wall. Specifically, at each time step, the net force acting on the particle is calculated based on its contact state, and then the acceleration is solved using Newton's second law to update the particle's velocity and position. This method directly considers the instantaneous acceleration of the particle, enabling a more accurate description of its transient motion behavior.

[0084] This embodiment discloses a method for inducing particle adsorption of specific patterns based on microfluidic bubble generation, the specific implementation method of which is as follows:

[0085] In numerical calculations, the selection of the time step must refer to the characteristic time scale that can resolve the changes in particle momentum—the Stokes time. Stokes time is a characteristic timescale describing the time required for the velocity of a small spherical particle in a viscous fluid to relax exponentially from its initial value to the flow field velocity. Physically, it is the characteristic time for the particle's momentum to be dissipated through viscous damping, and its expression is:

[0086]

[0087] If the selected computation time step is much larger than If the selected time step is smaller than or equal to the instantaneous process of particle acceleration change, it will be unable to accurately capture the transient process, resulting in a distorted motion description; conversely, if the selected time step is smaller than or equal to the instantaneous process of particle acceleration change, it will be more accurate. If the time steps are sufficiently equal, the instantaneous relationship between the force and acceleration of the particles can be fully analyzed, ensuring the accuracy of the dynamic description. Therefore, corresponding time steps are set for particles of different sizes, as shown in Table 1, ensuring that they are all less than the corresponding Stokes time. Taking a 5 µm particle as an example, its Stokes time... The selected time step is 4×10 -8 The time step is set to s, satisfying the above requirements. This principle is followed in selecting the time step for all operating conditions, thereby ensuring both computational stability and the physical authenticity of the simulation results.

[0088] Table 1. Stokes time and calculation time step for particles of different diameters.

[0089] Particle diameter d (µm) Stokes time τ(s) Calculate the time step Δt(s) 3 <![CDATA[1.7×10 -8 ]]> <![CDATA[1×10 -8 ]]> 5 <![CDATA[4.9×10 -8 ]]> <![CDATA[4×10 -8 ]]> 6 <![CDATA[7×10 -8 ]]> <![CDATA[5×10 -8 ]]> 7 <![CDATA[9.5×10 -8 ]]> <![CDATA[8×10 -8 ]]> 16 <![CDATA[5×10 -7 ]]> <![CDATA[4×10 -7 ]]>

[0090] The liquid film exhibits three characteristic thicknesses during particle deposition: the first is the thinnest part of the catamaran-shaped liquid film. Secondly, the area where the film thickness abruptly decreases at the tail of the bubble corresponds to... Thirdly, the average film thickness in the abdomen of the bubble is nearly uniform. The relationship between particle diameter and the aforementioned three characteristic thicknesses determines its deposition mode. (Using capillary number...) Taking the simulation of long bubbles under certain conditions as an example, at this time... .

[0091] Taking 5 µm particles as an example, 18 particles were numerically released at the bubble leading edge. These particles were initially located at different y-coordinate positions and were uniformly distributed (e.g., ...). Figure 2 (As shown). The bubble morphology and capillary number Ca are both related to... Figure 1 Condition b is consistent, capillary number At this point, the minimum thickness of the liquid film The speed of the bubble movement is The particle trajectory is obtained by time-step integration, and the Viridis color scheme line segments on the particle trajectory represent the velocity magnitude at each time step. A 5µm particle is located at the leading edge of the bubble, and its diameter satisfies... Most particles maintain a horizontal, straight trajectory during penetration of the liquid film; only a small number of particles deflect their trajectories in the positive y-direction. Overlap occurs on the outer side. In this case, the particle deposition location is concentrated in... The surrounding area forms bands, and the asterisks in the figure indicate the deposition locations of particles in the bubble reference system.

[0092] The specific steps for creating a particle adsorption pattern are as follows:

[0093] S1. Draw the microfluidic chip structure diagram. Protruding channel structures with rectangular cross-sections are machined on an acrylic plate using a milling process. PDMS and a crosslinking agent are mixed at a mass ratio of 9:1 and degassed. The mixture is poured into a mold containing the protruding channels obtained by milling the acrylic plate. It is then cured at a constant temperature of 70℃ to form a PDMS layer with a microchannel structure. After cutting and punching holes, the PDMS layer is surface-treated with plasma and bonded to a glass slide to obtain a closed microfluidic chip with three independent inlets (air inlet, pure PEG solution inlet, and particulate suspension inlet) and one outlet.

[0094] S2. Multiple injection pumps are connected to the chip's air inlet, pure PEG solution inlet, and particle suspension inlet via hoses to ensure unobstructed fluid flow in each channel. A 25 wt% PEG solution and 5 μm diameter monodisperse polystyrene microspheres are used. Absorbent material is placed at the chip outlet to absorb discharged liquid and prevent backflow from affecting system stability. The air inlet flow rate is set to 150 μl / min, and the PEG solution inlet flow rate is set to 45 μl / min. Uniform and controllable-sized microbubbles are formed through the flow focusing structure within the chip, allowing these bubbles to continuously advance along the microchannel direction and achieve a basically uniform and stable motion. The moving bubble liquid film induces particle adsorption at the lower wall of the channel.

[0095] S3. By adjusting the bubble movement speed, the morphology of the liquid film on the lower surface of the bubble is controlled, and the relative relationship between the injected particle diameter and the thickness of the liquid film on the lower surface is adjusted to control the bubble capillary number to the capillary number simulated by the numerical model above. The particles are controlled to deposit at predetermined points on the wall surface to form an adsorption pattern.

[0096] S4. Using a microscope, fix the observation plane on the near-wall area of ​​the channel. Utilize a high-speed camera to continuously acquire video and record images of the bubble movement and particle adsorption process. After a period of time, obtain the particle adsorption pattern on the lower wall of the pipe along the direction of bubble-liquid film movement, such as... Figure 3 .

[0097] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for inducing particle adsorption of specific patterns based on microfluidic bubble generation, characterized in that: Includes the following steps: Step 1: Obtain three-dimensional flow field data containing spatial position, corresponding velocity, and phase field information; perform numerical simulation of particle motion based on the three-dimensional flow field data, and calculate the forces acting on the particles—gravity, buoyancy, viscous drag, van der Waals attraction, electrostatic repulsion, friction, wall support force, and capillary force—by determining the contact states between the particles and the wall and the gas-liquid interface; construct the particle motion equations based on the combined action of the above eight forces, update the particle positions and obtain the migration trajectories using a time-progression method according to the obtained motion equations; contact states include free motion state, wall contact state, pure gas-liquid interface contact state, and dual contact state between the gas-liquid interface and the solid wall. Step 2: When the spherical surface of the particle comes into contact with the solid wall, that is, when it is in a state of wall contact or a state of double contact between the gas-liquid interface and the solid wall, if the velocity of the particle in the solid wall is the same as the velocity of the solid wall, then it is determined that the particle has completed the transition from free motion to stable deposition, and the position of the particle at this time is recorded as the deposition site. All the deposits converge to form a specific pattern.

2. The method as described in claim 1, characterized in that: The gravity G mentioned in step one is: Buoyancy F b : Viscous resistance F D : in: Particle radius Particle density fluid density It is the gravitational acceleration vector. = (0, 0, - ) For fluid dynamic viscosity Particle velocity vector Let be the fluid velocity vector at the center of the particle.

3. The method as described in claim 1, characterized in that: The van der Waals attraction F described in step one VdW : in: Hamaker constant The shortest distance between the particle surface and the wall. electrostatic repulsion F ele : in: Relative permittivity The vacuum permittivity Debye length , Zeta potentials of particles and glass walls, respectively. Wall support force F N : Friction force F f : in: coefficient of friction capillary force : in: The gas-liquid interfacial tension coefficient For fill corner Let be the unit vector from the center of the circle where the gas-liquid interface contacts the particle to the center of the particle sphere.

4. The method as described in claim 1, characterized in that: The free motion state described in step one is defined as follows: when the particle is completely submerged in the liquid phase and its spherical surface is neither in contact with the solid wall below nor with the gas-liquid interface above, it is considered to be in a free motion state. At this time, the particle is mainly subjected to three forces: gravity G (vertically downward), buoyancy F (vertically upward). b And the viscous drag F, which is proportional to the relative velocity of the particles and the fluid. D Its equation of motion is as follows: Among them, particle mass In this state, the motion of the particles is entirely determined by the flow field and their own settling tendency. Based on the obtained particle motion equation, the acceleration of the particle motion is obtained. Using the velocity and acceleration at the current moment, the particle position at the next moment is obtained according to the set time step, thus obtaining the particle migration trajectory.

5. The method as described in claim 1, characterized in that: The pure gas-liquid interface contact state described in step one occurs when, during particle movement, the particle's spherical surface is detected to be in contact only with the gas-liquid interface within the physical field, while the bottom of the particle's spherical surface does not touch the solid wall. The gas-liquid interface is considered an impenetrable but slippery geometric constraint surface. In this state, complex capillary forces are ignored. The gravity G and buoyancy F acting on the particle are... b and viscous resistance F D The resultant force is denoted as F. total The component perpendicular to the interface is balanced by the rigid reaction force of the interface; while the sum of the tangential components of all forces drives the particle to slide along the gas-liquid interface. This resultant tangential force is expressed as: Where n is the normal vector of the gas-liquid interface; therefore, the particle motion equation is as follows: In this state, the particles move along the tangential plane of the gas-liquid interface. Based on the obtained particle motion equation, the acceleration of the particle motion is obtained. Using the velocity and acceleration at the current moment, the particle position at the next moment is obtained according to the set time step, thus obtaining the particle migration trajectory.

6. The method as described in claim 1, characterized in that: The wall contact state is defined as the state when the bottom spherical surface of the particle is low enough to contact the solid wall. Besides gravity G and buoyancy F b and viscous resistance F D In addition, particles will be subjected to complex surface forces from the wall: including intermolecular van der Waals forces F that vary with distance. VdW The electrostatic repulsion F generated by the surface charge ele And the sliding friction force F that prevents the particles from sliding along the wall. f and the supporting force F provided by the solid wall. N The net force acting on it is denoted as F. total Therefore, the equation of motion for the particles is as follows: In this state, the particles move near the wall. Based on the obtained particle motion equation, the acceleration of the particle motion is obtained. Using the velocity and acceleration at the current moment, the particle position at the next moment is obtained according to the set time step, thus obtaining the particle migration trajectory. In the bubble reference frame, when the particle's velocity within the solid wall reaches the same velocity as the solid wall, it is determined that the particle has completed the transition from free motion to stable deposition. The position at this moment is recorded as the deposition site, and all deposition points converge into a specific pattern.

7. The method as described in claim 1, characterized in that: The dual contact state between the gas-liquid interface and the solid wall is defined as follows: when the spherical surface of the particle is simultaneously identified as being in contact with both the solid wall and the gas-liquid interface, it is determined to be in a dual contact state between the gas-liquid interface and the solid wall. At this time, the particle is "compressed" between the solid wall and the gas-liquid interface, causing significant deformation of the gas-liquid interface, thereby generating a significant capillary force F. γ Furthermore, a contact circle exists between the gas-liquid interface and the particle. Using discrete point data of the gas-liquid interface at a distance of no more than 20 μm from the normal direction of the particle's spherical surface, a contact plane between the particle and the gas-liquid interface is fitted. The center of the particle's sphere is then vertically projected onto this fitted plane to obtain the center of the contact circle. This 20 μm threshold range ensures that, considering the local curvature of the interface and numerical discretization errors, the selected data points can effectively characterize the geometric features of the contact area. The capillary force F... γ The direction of the contact circle points from the center of the contact circle to the center of the particle, and its size depends on the interfacial tension coefficient, the particle radius, and the contact angle between the particle and the gas-liquid interface. In this state, the forces acting on the particle are the most comprehensive of all states, and gravity G and buoyancy F must be considered simultaneously. b Viscous resistance F D Wall van der Waals force F VdW electrostatic force F ele Friction force F f Wall support force F N And the crucial capillary force F γ The net force acting on it is denoted as F. total Therefore, the equation of motion for the particles is as follows: In this state, the particles are trapped between the gas-liquid interface and the solid wall. Based on the obtained particle motion equation, the acceleration of the particle motion is calculated. Using the velocity and acceleration at the current moment, the particle position at the next moment is determined according to the set time step, thus obtaining the particle migration trajectory. In the bubble reference frame, when the particle's velocity within the solid wall and the velocity of the solid wall reach the same level, it is determined that the particle has completed the transition from free motion to stable deposition. The position at this moment is recorded as the deposition site, and all deposition points converge into a specific pattern.

8. A method for producing the pattern as described in claim 1 or 2, characterized in that: Includes the following steps, S1. A PDMS chip layer is prepared by casting PDMS material in an acrylic mold, and then bonded to a glass slide after being treated by a plasma cleaner to obtain a microfluidic chip. S2. Air, solution and particulate suspension are injected into the microfluidic chip through an injection pump. Bubbles are stably generated by the chip's flow focusing structure. The moving bubble liquid film induces the particles to be adsorbed on the lower wall of the channel. S3. By adjusting the speed of bubble movement, the morphology of the liquid film on the lower surface of the bubble is controlled, and the relative size relationship between the diameter of the injected particles and the thickness of the liquid film on the lower surface is adjusted to control the particles to be deposited on the wall at predetermined points to form an adsorption pattern. S4. Using a microscope, lock the observation plane onto the area near the wall of the channel. Use a high-speed camera to continuously acquire video and record images of the bubble movement and particle adsorption process. After waiting for a preset time, obtain the particle adsorption pattern on the lower wall of the pipe along the direction of bubble liquid film movement.

Images