Droplet merging self-bounce strengthening control device, method and equipment

Abstract

The invention discloses a droplet merging self-bouncing reinforced control device, method and equipment, and relates to the technical field of fluid mechanics, acoustics and microfluidics, the device comprises a substrate surface, a controller, a signal generator and an ultrasonic transducer; the controller is connected with the signal generator and outputs an electric signal by controlling the signal generator; the ultrasonic transducer is connected with the signal generator and is used for outputting corresponding sound wave parameters according to the electric signals; the upper boundary of the ultrasonic transducer is provided with a substrate surface; the surface of the substrate is used for placing liquid drops and determining a control space according to parameters of the liquid drops; the ultrasonic transducer also generates a sound wave field in the control space according to the sound wave parameters, and the sound wave field is controlled by changing the sound wave parameters, so that the liquid drops enter the standing wave nodes to be merged; and the combined liquid drops are controlled to bounce to a target area at a preset liquid drop bouncing direction and speed by applying a phase gradient sound wave field. According to the invention, the precision and the flexibility of micro-fluidic liquid drop control can be improved.

Description

Technical Field

[0001] The present application relates to the fields of fluid mechanics, acoustics, and microfluidics, and in particular to a device, method, and apparatus for enhancing control of droplet merging and self-bouncing. Background Art

[0002] Droplet manipulation is one of the core research directions of microfluidics technology and is widely used in biomedical testing, drug delivery, flexible electronic manufacturing, inkjet printing and other fields. Current droplet manipulation methods mainly include: (1) Electric field manipulation: changing the contact angle of the droplet through the electric field to achieve the movement and fusion of the droplet; however, this method requires specific dielectric droplets and is easily affected by environmental pollution. (2) Magnetic field manipulation: it is necessary to dope magnetic nanoparticles into the droplet so that it can move in a controlled manner under an external magnetic field; however, its application is limited and it is not suitable for ordinary biological or chemical droplets. (3) Surface patterning manipulation: regulating the movement of the droplet through hydrophobic / hydrophilic patterning; however, the surface pattern is fixed and difficult to adjust dynamically, which is not suitable for complex scenarios.

[0003] In contrast, acoustic wave manipulation of droplets has become a research hotspot in recent years due to its non-contact nature, high controllability, and wide droplet compatibility. However, existing acoustic wave-based droplet manipulation is mainly used for droplet movement and splitting. Furthermore, due to its dynamic characteristics, the direction of droplet merging and bouncing is relatively fixed, and the energy conversion efficiency is low. How to use acoustic waves to precisely control droplet merging and bouncing remains a key technical challenge.

[0004] Therefore, in order to solve the above technical problems, there is an urgent need for a droplet merging and bouncing control method that can improve the precision and flexibility of microfluidic droplet manipulation. Summary of the Invention

[0005] The purpose of this application is to provide a droplet merging and self-bouncing enhanced control device, method and equipment, which can improve the accuracy and flexibility of microfluidic droplet manipulation.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides a droplet merging and self-bouncing enhanced control device, comprising: a substrate surface, a controller, a signal generator, and an ultrasonic transducer;

[0008] The controller is connected to the signal generator and is used to control the signal generator to output an electrical signal;

[0009] The ultrasonic transducer is connected to the signal generator and is used to output corresponding sound wave parameters according to the electrical signal; the sound wave parameters include: the frequency of the sound wave, the phase of the sound wave and the amplitude of the sound wave;

[0010] The upper boundary of the ultrasonic transducer is provided with a substrate surface; the substrate surface is used for placing droplets, and a control space is determined according to the parameters of the droplets; the ultrasonic transducer is further used for generating an acoustic wave field in the control space according to the acoustic wave parameters, and controlling the acoustic wave field by changing the acoustic wave parameters so that the droplets enter the standing wave nodes and merge; and controlling the merged droplets to bounce to the target area in a preset droplet bouncing direction and speed by applying an acoustic wave field with a phase gradient; the parameters of the droplets include: the radius of the droplets and the fluid parameters of the droplets; the fluid parameters of the droplets include: the surface tension of the droplets, the density of the droplets, and the viscosity of the droplets.

[0011] Optionally, the ultrasonic transducer includes multiple ultrasonic transducer units; each of the ultrasonic transducer units is connected to the signal generator respectively, and is used to adjust the corresponding driving voltage under the control of the electrical signal and generate a corresponding phase; the phases of the multiple ultrasonic transducer units constitute a phase gradient.

[0012] Optionally, the frequency range of the acoustic wave field is 20 kHz to 2 MHz.

[0013] In a second aspect, the present application provides a droplet merging and self-bouncing enhancement control method, which is applied to any of the droplet merging and self-bouncing enhancement control devices described above. The droplet merging and self-bouncing enhancement control method includes:

[0014] setting an upper boundary of the ultrasonic transducer to a substrate surface and placing a liquid droplet on the substrate surface;

[0015] Get the parameters of the droplet;

[0016] Based on the droplet parameters, acoustic wave parameters corresponding to the control space and the standing wave nodes are obtained; the acoustic wave parameters include: the frequency of the acoustic wave, the phase of the acoustic wave, and the amplitude of the acoustic wave;

[0017] Based on the acoustic wave parameters corresponding to the standing wave nodes, the signal generator is controlled by the controller to obtain the corresponding electrical signal;

[0018] The ultrasonic transducer is controlled based on the electrical signal to obtain the acoustic wave field corresponding to the standing wave node in the control space;

[0019] Based on the acoustic wave field corresponding to the standing wave node, the droplets are made to enter the standing wave node and merge;

[0020] Based on the preset droplet bouncing direction and speed, the controller controls the signal generator, which in turn controls the ultrasonic transducer to obtain a phase gradient acoustic wave field.

[0021] The phase gradient-based acoustic wave field controls the merged droplets to bounce to the target area at a preset droplet bouncing direction and speed.

[0022] Optionally, obtaining the acoustic wave parameters corresponding to the control space and the standing wave nodes based on the droplet parameters specifically includes:

[0023] Using the formula p = p0e jωt Determine the lower boundary of the control space; where p represents the sound pressure, p0 represents the amplitude of the sound wave, ω is the angular frequency of the sound wave, t represents the time of the sound wave change, and j represents an imaginary number;

[0024] The upper and side boundaries of the control space are determined using the perfectly matched layer method.

[0025] Optionally, controlling the ultrasonic transducer based on the electrical signal to obtain an acoustic wave field corresponding to a standing wave node in the control space specifically includes:

[0026] Using the formula Determine the equation for the acoustic wave field; where the wave number c represents the speed of sound, π represents the circumference of a circle, and f represents the frequency of the sound wave. represents the gradient operation;

[0027] According to the equation of the acoustic wave field, the finite element method and the finite difference method are used to determine the acoustic wave field.

[0028] Optionally, the step of causing the droplets to enter the standing wave node and merge based on the acoustic wave field corresponding to the standing wave node specifically includes:

[0029] Using the formula Convert the force of the acoustic wave field into acoustic wave force F;

[0030] Based on the action of acoustic wave force, the droplets enter the standing wave node and merge;

[0031] Using the formula Determine the droplet merging time t c ;

[0032] Where R represents the droplet radius, represents the acoustic pressure gradient, ρ represents the density of the droplet, d represents the diameter of the droplet, and γ represents the surface tension of the droplet.

[0033] Optionally, the phase gradient-based acoustic wave field controls the merged droplets to bounce to a target area in a preset droplet bouncing direction and speed, specifically including:

[0034] Using equations Calculate the motion of the droplet;

[0035] Among them, F s represents the acoustic radiation force, u represents the fluid velocity field, μ represents the viscosity of the liquid, and t represents the time for the sound wave to change.

[0036] Optionally, the phase gradient-based acoustic wave field controls the merged droplets to bounce to a target area in a preset droplet bouncing direction and speed, specifically including:

[0037] Using the formula and Calculate the preset bounce direction of the droplet;

[0038] Using the formula Calculate the preset droplet bounce velocity U j ;

[0039] Wherein, X, Y, and Z represent the horizontal projection, longitudinal projection, and vertical projection of the preset droplet's bouncing direction, respectively. represents the phase difference required for the droplet to bounce to the target area with the preset bounce direction and speed, φ represents the phase field variable, x represents the horizontal coordinate of the droplet center of mass, y represents the vertical coordinate of the droplet center of mass, z represents the vertical coordinate of the droplet center of mass, V represents the volume of the droplet, and U y is the velocity component perpendicular to the plane.

[0040] In a third aspect, the present application provides a computer device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the droplet merging and self-bouncing enhancement control method.

[0041] According to the specific embodiments provided in this application, this application has the following technical effects:

[0042] The present application provides a device, method and equipment for enhancing control of droplet merging and self-bouncing, wherein the upper boundary of the ultrasonic transducer is set as the substrate surface, droplets are placed on the substrate surface, and the control space is determined according to the parameters of the droplets, so that the bounce speed and direction of the droplets can be accurately obtained, and the controller is used to control the signal generator to output an electrical signal. The electrical signal output by the signal generator includes an acoustic wave signal of a specific frequency, phase and amplitude, which can achieve precise control of the droplet behavior; the controller is connected to the signal generator, and the ultrasonic transducer is connected to the signal generator. The ultrasonic transducer outputs corresponding acoustic wave parameters according to the electrical signal, and the acoustic wave parameters are adjusted by the controller to control the merging, bouncing and motion trajectory of the droplets. The operation is simple, the adaptability is flexible, and the operating parameters, quantity and arrangement of the transducers can be changed. It can meet different practical needs; the ultrasonic transducer generates an acoustic wave field in the control space according to the acoustic wave parameters, and controls the acoustic wave field by changing the acoustic wave parameters, so as to obtain acoustic wave force, so that the droplets enter the standing wave node, so as to realize the spatial positioning of the droplet movement, merge, improve the droplet merging efficiency, and reduce energy consumption. The droplet merging process is precisely controlled by the acoustic wave parameters to ensure the merging stability and repeatability; and by applying a phase gradient acoustic wave field, the merged droplets are controlled to bounce to the target area with a preset droplet bouncing direction and speed, and non-contact manipulation is adopted to ensure the accuracy of droplet manipulation; the present application can improve the accuracy and flexibility of microfluidic droplet manipulation, and provides a high-precision and low-energy consumption solution for engineering fields such as microfluidics, enhanced heat transfer and surface deicing. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 This is a schematic diagram of a droplet merging and self-bouncing enhancement control device in one embodiment of the present application;

[0045] Figure 2 A schematic diagram of the mechanism of acoustic wave action provided in one embodiment of the present application;

[0046] Figure 3 This is a flow chart of a method for enhancing control of droplet merging and self-bouncing provided in one embodiment of the present application;

[0047] Figure 4 A schematic diagram of the position of liquid droplets provided in an embodiment of the present application;

[0048] Figure 5A schematic diagram showing a comparison of droplet bounce speeds in a droplet merging and self-bounce enhancement control method provided in an embodiment of the present application;

[0049] Figure 6 Schematic diagram of the comparison of the lateral velocity of the droplet bouncing after changing the phase angle;

[0050] Figure 7 A schematic diagram of the structure of a computer device provided in one embodiment of the present application.

[0051] Reference numerals:

[0052] 1-control space, 2-substrate surface, 3-droplet, 4-ultrasonic transducer, 5-controller, 6-signal generator. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0054] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0055] In an exemplary embodiment, Figure 1 and Figure 2 As shown, a device for enhancing control of droplet 3 merging and self-bouncing is provided, comprising: a substrate surface 2, a controller 5, a signal generator 6 and an ultrasonic transducer 4.

[0056] The ultrasonic transducer 4 is connected to the signal generator 6 and is used to output corresponding sound wave parameters according to the electrical signal; the sound wave parameters include: the frequency of the sound wave, the phase of the sound wave and the amplitude of the sound wave.

[0057] The upper boundary of the ultrasonic transducer 4 is provided with a base surface 2. This base surface 2 is used to place droplets 3, and the control space 1 is determined based on the parameters of the droplets 3. The ultrasonic transducer 4 is also used to generate an acoustic wave field within the control space 1 based on the acoustic wave parameters. By varying the acoustic wave parameters, the acoustic wave field is controlled to cause the droplets 3 to enter standing wave nodes and merge. The acoustic wave field, which applies a phase gradient, controls the merged droplets 3 to bounce to a target area at a predetermined direction and velocity. This is suitable for a variety of applications, including microfluidics, biomedical analysis, chemical synthesis, and flexible electronics manufacturing. The droplet 3 parameters include the droplet 3 radius and fluid parameters, including surface tension, density, and viscosity. The acoustic wave field frequency range is 20 kHz to 2 MHz, and can be dynamically adjusted based on experimental requirements and droplet 3 size to accommodate the manipulation of different droplet types.

[0058] In an exemplary embodiment, the controller 5 is connected to the signal generator 6 and is used to control the signal generator 6 to output an electrical signal. The controller 5 includes a computer unit and a visualization module (consisting of an independent signal oscilloscope and a high-speed camera that captures the motion of the droplet 3). This provides real-time feedback and allows for control based on the results to improve the precision and efficiency of droplet 3 manipulation. The signal generator 6 includes multiple independent signal channels to enable independent adjustment of acoustic wave parameters in different regions, thereby adapting to complex droplet 3 manipulation requirements.

[0059] In an exemplary embodiment, the controller 5 generates control instructions based on a preset program or external input. These control instructions contain the parameters required for the signal generator 6 and are transmitted to the signal generator 6 via digital or analog signals. Upon receiving the required parameters, the signal generator 6 adjusts its internal circuitry accordingly to generate an electrical signal that meets the requirements. The signal generator 6 changes the frequency of the output signal based on the required parameters, providing an acoustic signal with a specific frequency, phase, and amplitude to precisely control the behavior of the droplet 3. Different frequencies cause the ultrasonic transducer 4 to generate acoustic waves of different frequencies, thereby affecting the speed and direction of the droplet 3's bounce. Increasing the signal frequency may shorten the wavelength of the acoustic waves generated by the transducer, thereby changing the force applied to the droplet 3, causing it to move faster or change direction. By adjusting the amplitude of the signal output from the signal generator 6, the intensity of the acoustic waves generated by the ultrasonic transducer 4 can be controlled. A larger signal amplitude causes the transducer to vibrate more violently, generating stronger acoustic waves, which in turn exerts greater force on the droplet 3 and causes it to bounce more significantly. The signal generator 6 can generate different waveforms, such as sine waves, square waves, and sawtooth waves. Different waveforms will affect the characteristics of the sound waves, and thus affect the movement behavior of the droplet 3 .

[0060] Ultrasonic transducer 4 and signal generator 6 interact through the transmission and conversion of electrical signals. The vibration frequency, amplitude, and other characteristics of ultrasonic transducer 4 are closely related to the received electrical signal. Upon receiving the electrical signal, the piezoelectric material within ultrasonic transducer 4 vibrates. The resulting mechanical deformation under the action of the electric field converts the electrical signal into acoustic wave parameters. After converting the electrical signal into acoustic wave parameters, ultrasonic transducer 4 provides the acoustic force field required to manipulate droplet 3. Using standing wave nodes and acoustic radiation forces, it acts on droplet 3, influencing its motion.

[0061] In an exemplary embodiment, the control space 1 (computational domain) is a three-dimensional cuboid with a length and width of 10R and a height of 20R, where R is the radius of the droplet 3. Two droplets 3 of the same material are placed on the bottom solid surface of the cuboid control space 1. The cuboid is the area where the droplets 3 are located, the two circles are double droplets 3, below which is a super-hydrophobic surface, and the cylinders below the surface are four ultrasonic transducers 4. According to the dynamic characteristics, the merging and bouncing direction of the droplets 3 is relatively fixed. In the case of equal size, the direction of the jump after merging is the normal direction of the surface. In the case of different sizes, due to the asymmetric distribution of the mass of the two droplets 3, the jumping direction is slightly deviated from the normal direction, and there is rotational motion. At the same time, the energy conversion efficiency of the merging self-bouncing process is low, so active fields (such as electric fields, magnetic fields, light fields, etc.) can be used to excite and change the bouncing characteristics.

[0062] The substrate surface 2 is configured as a super-hydrophobic surface. The contact angle of the substrate surface 2 is 170°. At the boundary where the droplet 3 contacts the solid surface, the contact angle θ can be calculated using the gradient of the phase field function and the surface normal direction.

[0063] Specifically, using the formula Calculate the contact angle of substrate surface 2; where, is the gradient of the phase field function, and n is the normal direction of the solid surface.

[0064] As an optional embodiment, the ultrasonic transducer 4 includes multiple ultrasonic transducer 4 units; each of the ultrasonic transducer 4 units is respectively connected to the signal generator 6, and is used to adjust the corresponding driving voltage under the control of the electrical signal and generate a corresponding phase; the phases of the multiple ultrasonic transducer 4 units constitute a phase gradient.

[0065] In another exemplary embodiment, Figure 3 and Figure 4 As shown, a method for enhancing control of the merging and self-bouncing of droplets 3 is provided, including:

[0066] S101: The upper boundary of the ultrasonic transducer 4 is set to the substrate surface 2, and a droplet 3 is placed on the substrate surface 2. The droplets 3 are placed at the center of the substrate surface 2, with either tangent or a small gap between them. Depending on the wettability of the surface, the droplets 3 initially assume a spherical crown shape, with the bottom of the droplet 3 at a 10° tangent angle to the surface. After the ultrasonic transducer 4 generates sound waves, the sound field influences the dynamic behavior of the droplets 3, causing them to merge at a specific location and then bounce to the target location under controlled conditions.

[0067] S102: Obtain parameters of the droplet 3.

[0068] In an exemplary embodiment, the parameters of the droplet 3 are obtained by measuring and analyzing the characteristics of the droplet 3. The size of the droplet 3 does not exceed the millimeter level. Specifically, by measuring and analyzing the relevant characteristics of the droplet 3 in a silent field, including the radius of the droplet 3 and the fluid parameters of the droplet 3, it is obtained that the radius R of the droplet 3 is 690 microns, the surface tension γ of the droplet 3 is 0.0728 N / m, and the liquid density ρ is 998 kg / m 3 , the liquid viscosity μ is 1.071×10 -3 Pa·s. The movement of the droplet 3 is recorded by a high-speed camera, and the motion information of the droplet 3 in the silent field, such as the bounce speed, direction, and height, is obtained in real time using image analysis software. In addition, the air density ρ is also obtained. l 1.19kg / m 3 e, air viscosity μ l 1.8×10 -5 Pa·s.

[0069] S103: Based on the parameters of the droplet 3, obtain the acoustic wave parameters corresponding to the control space 1 and the standing wave node; the acoustic wave parameters include: the frequency of the acoustic wave, the phase of the acoustic wave, and the amplitude of the acoustic wave.

[0070] Among them, S103 includes:

[0071] S301: Use the formula p=p0e jωt Determine the lower boundary of control space 1; where p represents the sound pressure, that is, the sound wave pressure at a certain moment, which is usually a complex number and contains amplitude and phase information. px represents the amplitude of the sound wave, that is, the maximum pressure of the sound wave. ω is the angular frequency of the sound wave, ω = 2πf, f represents the frequency of the sound wave, indicating the speed of periodic change of the sound wave. t represents the time of sound wave change. j represents an imaginary number.

[0072] S302: Use the perfectly matched layer (PML) method to determine the upper and side boundaries of control space 1. PML is used to simulate the boundary conditions of an open space. The core concept is to introduce a layer of absorbing medium outside the boundary of control space 1 so that the energy of the incident wave is rapidly attenuated after entering the PML, thereby preventing the reflected wave from interfering with the results within control space 1.

[0073] Specifically, using the formula Determine the perfectly matched layer; where v represents the initial velocity of the droplet 3, ρ0 represents the density of the perfectly matched layer, σ represents the absorption coefficient of the PML, and c represents the speed of sound.

[0074] Among them, the acoustic field boundary conditions and the flow field boundary conditions are set, and the droplet 3 is placed on the super-hydrophobic surface in a stable state under the set contact angle conditions; in the flow field boundary conditions, the super-hydrophobic surface is a solid no-slip boundary (No-Slip Condition), represented by u=0; the other boundaries are pressure outlet boundaries (pressure-outlet condition) represented by p 出口 =p ref +Δp, where p 出口 Indicates the absolute pressure at the outlet, p ref Represents atmospheric pressure, and Δp represents the pressure difference between the absolute pressure at the outlet and the atmospheric pressure. Usually, the relative pressure at the outlet (relative to the reference pressure) is set to 0, which means that the absolute pressure at the outlet is equal to the reference pressure.

[0075] S104: Based on the acoustic wave parameters corresponding to the standing wave nodes, the controller 5 controls the signal generator 6 to obtain a corresponding electrical signal.

[0076] S105: Ultrasonic transducers 4 are controlled based on the electrical signal to obtain acoustic wave fields corresponding to standing wave nodes within control space 1. Ultrasonic transducers 4 can be arranged as a single or multiple arrays to generate a uniform or non-uniform acoustic wave field within control space 1, providing a basic acoustic field environment for regulating the movement of droplets 3 and enabling parallel manipulation of multiple droplets 3. The initial position of droplets 3 must also be determined to ensure they are within an area where the acoustic waves can effectively act.

[0077] Specifically, S105 includes:

[0078] S501: Utilize formula Determine the equation for the acoustic wave field; where the wave number f represents the frequency of the sound wave, represents the gradient operation, c represents the speed of sound, and π represents pi.

[0079] In one exemplary embodiment, an ultrasonic transducer 4 is positioned below the substrate surface 2, approximately cylindrical in shape with a radius of 2R. By adjusting the position and number of ultrasonic transducers 4 and adjusting operating parameters according to actual needs, the droplets 3 can be deflected in a certain direction rather than vertically jumping. The acoustic wave field emitted by the ultrasonic transducer 4 is equivalent to the acoustic field emitted by the substrate surface 2. The acoustic field applied by the substrate surface 2 is calculated based on the Helmholtz equation to obtain the acoustic wave field equation.

[0080] S502: Determine the acoustic wave field using a finite element method and a finite difference method according to the acoustic wave field equation.

[0081] S106: Based on the acoustic wave field corresponding to the standing wave node, droplets 3 are forced to enter the standing wave node for merging. By adjusting the frequency, amplitude, and phase of the acoustic wave, multiple droplets 3 are merged within a predetermined area. The merging process of droplets 3 is precisely controlled by the acoustic wave parameters to ensure merging stability and repeatability.

[0082] In order to further enhance the control accuracy of the droplets 3, the present application utilizes the acoustic streaming effect, allowing the sound waves to cause the droplets 3 to vibrate when propagating in the liquid. Along with the changes in the internal pressure of the droplets 3, the merging of the droplets 3 is enhanced through vibration and deformation.

[0083] In an exemplary embodiment, S106 includes:

[0084] S601: Using public The force of the acoustic field is converted into acoustic force F. According to the acoustic force formula, the force of the acoustic field can be converted into acoustic force, which directly acts on the droplet 3 in its initial state. The droplet 3 is affected by the acoustic force F in the standing wave field.

[0085] S602: Based on the effect of the acoustic wave force, the droplet 3 enters the node of the standing wave and merges.

[0086] The merging process of droplets 3 is optimized by controlling the standing wave pattern of the acoustic wave, so that the droplets 3 gather at the standing wave nodes, and their merging is guided by adjusting the interaction force between adjacent droplets 3.

[0087] S603: Utilize formula Determine the merging time t of droplet 3 c According to the merging mechanism of droplet 3, droplet 3 gradually approaches the standing wave node and merges under the action of the acoustic field. Its dynamics is affected by surface tension, inertial force, and acoustic wave force. The merging time of droplet 3 is obtained based on the formula.

[0088] Where R represents the radius of the droplet 3, represents the acoustic pressure gradient, π represents the circumference of a circle, ρ represents the density of the droplet 3 , d represents the diameter of the droplet 3 , and γ represents the surface tension of the droplet 3 .

[0089] S107: Based on the preset bouncing direction and speed of the droplet 3, the controller 5 controls the signal generator 6, and then controls the ultrasonic transducer 4 through the signal generator 6 to obtain a phase gradient acoustic wave field.

[0090] Based on the preset bouncing direction and speed of the droplet 3, the acoustic wave parameters are further adjusted, or the arrangement relationship of multiple ultrasonic transducer 4 units (acoustic wave sources) is adjusted to form a phase gradient of a specific direction and magnitude in the area where the droplet 3 is located, thereby obtaining a phase gradient acoustic wave field. The change in phase gradient will cause the direction and intensity of the acoustic flow to change. By designing a specific phase gradient distribution, the acoustic flow can form a localized circulation or directional flow, thereby pushing the droplet 3 to bounce along the preset direction, causing the merged droplet 3 to produce a directional bounce, and ensuring that the merged droplet 3 bounces to the target area in the set direction and speed. Among them, the direction and speed of the bounce can be adjusted by controlling the spatial distribution of the acoustic wave field and the energy input.

[0091] S108: Based on the phase gradient acoustic wave field, the merged droplet 3 is controlled to bounce to the target area in a preset bouncing direction and speed.

[0092] Under the action of the phase gradient, the droplet 3 is subjected to the effects of acoustic radiation force and other factors and begins to accelerate and merge. The motion state of the droplet 3 is monitored in real time, and the parameters such as the phase gradient are adjusted and optimized as needed to make the droplet 3 jump up according to the preset bounce speed and direction. The merger can induce the droplet 3 to spontaneously jump off the surface. The droplet 3 can jump up because the expanded liquid bridge after the merger will hit the super-hydrophobic surface, and the surface provides an upward reaction force to prompt the droplet 3 to leave the surface. From the perspective of energy conservation, the excess surface energy released after the merger can overcome the adhesion between the solid and the liquid and then be converted into kinetic energy for jumping up. This merger-induced spontaneous jumping off the surface behavior has a wide range of application value, such as dehydration and defrosting, liquid transportation, and enhanced droplet condensation heat transfer. Therefore, active fields (such as electric fields, magnetic fields, light fields, etc.) can be used to stimulate and change the bouncing characteristics.

[0093] The phase gradient required for droplet 3 to bounce to the target area at a predetermined bounce direction and speed is calculated. This phase gradient is achieved by adjusting the driving voltage of each unit in the acoustic wave transmitter. By adjusting the phase difference and amplitude of the acoustic wave, the bounce speed and path of droplet 3 are precisely controlled. Optical or other sensors are used to monitor the movement of droplet 3 to ensure it adheres to the predetermined bounce trajectory. Based on the actual movement of droplet 3, the acoustic field parameters are adjusted in real time to optimize the bounce effect.

[0094] This application also utilizes the acoustic radiation effect, allowing the sound waves to undergo physical effects such as reflection, refraction, and scattering with the surface of the droplet 3 during propagation, while also exchanging energy with the droplet 3. Macroscopically, this manifests as the sound waves exerting acoustic force on the droplet 3, thereby pushing the droplet 3 to merge and even move upward. This method applies multiple sound waves of different frequencies within the computational domain, allowing the droplet 3 to exhibit different motion characteristics under the action of sound fields of different frequencies. By appropriately adjusting the interaction between these frequencies, the merging rate of the droplet 3 and the direction and amplitude of the bounce can be further optimized.

[0095] In an exemplary embodiment, the phase field method (PFM) is used to track the interface of the droplet 3. The PFM uses the phase field variables Represents different phases (droplet 3 and surrounding medium), where φ=1 represents the droplet 3 region, and φ=0 represents the gas phase region. The Navier-Stokes equation is solved in combination with the Cahn-Hilliard equation to describe the merging and bouncing behavior of droplet 3.

[0096] Using the formula represents the result of combining the Navier-Stokes equation with the Cahn-Hilliard equation, where M is the phase field mobility coefficient, μ Φ is the chemical potential for a particular phase field variable φ, λ is the interface thickness parameter, f(φ) is the derivative of the free energy density with respect to φ, and a bistable state is taken.

[0097] Using equations Calculate the motion of droplet 3; where F s represents the acoustic radiation force, u represents the fluid velocity field, μ represents the liquid viscosity, and t represents the time variable of the acoustic wave. The motion of droplet 3 is solved using the Navier-Stokes equations, discretized using the Galerkin method for FEM. The computational domain is divided into an unstructured triangular mesh and solved using the PDE module.

[0098] Specifically, S108 includes:

[0099] S801: Using the public and The preset bouncing direction of the droplet 3 is calculated.

[0100] S802: Using formula Calculate the preset bounce speed U of droplet 3 j .

[0101] Wherein, X, Y, and Z represent the horizontal projection, longitudinal projection, and vertical projection of the corresponding bouncing direction of the droplet 3, respectively. represents the phase difference required for the droplet 3 to bounce to the target area with the preset bounce direction and speed, φ represents the phase field variable, x represents the horizontal coordinate of the center of mass of the droplet 3, y represents the vertical coordinate of the center of mass of the droplet 3, z represents the vertical coordinate of the center of mass of the droplet 3, V represents the volume of the droplet 3, U y is the velocity component perpendicular to the plane.

[0102] like Figure 5 As shown, the acoustic wave frequency used is approximately 1 MHz, the sound pressure is approximately 7.37 Pa, and the action time is approximately 0.1 ms. Gradually decreasing the frequency also reduces the initial velocity of droplet 3. Adding an acoustic field to the initial flow field is equivalent to giving droplet 3 greater initial kinetic energy. Calculate the initial velocity v of droplet 3.

[0103] Specifically, using the formula Calculate the initial velocity v of the droplet 3, where P represents the sound pressure in Pa and A represents the amplitude of the sound wave in m.

[0104] like Figure 6 As shown, the acoustic wave frequency used is approximately 1 MHz, the acoustic pressure is approximately 3.8 Pa, and the exposure time is approximately 0.1 ms. Gradually increasing the phase angle also increases the X-direction bounce velocity of the droplet 3. Based on the droplet 3 bounce dynamics, the merged droplet 3 continues to be affected by the phase gradient acoustic wave field, allowing for more precise control of the droplet 3's bounce direction and velocity.

[0105] The key technical advantages of this application include: non-contact manipulation, high-precision adjustment, low energy consumption, high efficiency, and high flexibility. The non-contact manipulation is suitable for sensitive applications such as biomedicine. The high-precision adjustment is reflected in the dynamic adjustment of acoustic wave parameters to precisely control the movement of droplets. Compared with traditional methods, this application improves the efficiency of droplet merging and reduces energy consumption. The application is simple to operate and flexible to adapt, and the operating parameters, number, and arrangement of transducers can be changed to meet different practical needs.

[0106] The present application can be applied to the fields of enhanced heat transfer, surface deicing, and surface self-cleaning. In the field of enhanced heat transfer, it can accelerate the detachment of condensed droplets 3 from the surface, effectively improve the droplet condensation heat transfer coefficient, and prevent heat transfer deterioration. In the field of surface deicing, the droplets 3 can be precisely positioned to manufacture organic light-emitting diodes (OLEDs) and inkjet printing technology. In the field of surface self-cleaning, the behavior of the droplets 3 can be controlled in a microgravity environment for material testing.

[0107] This application uses an adaptive sound field adjustment mechanism to monitor the motion state of droplets 3 in real time and dynamically adjust the parameters of the sound field, so that droplets 3 can achieve stable merging and bouncing under different environmental conditions. Compared with the traditional fixed sound field method, the adaptive sound field adjustment described in this application can effectively improve the flexibility of manipulation, reduce experimental errors, and expand the scope of application, thereby improving the precision and flexibility of microfluidic droplet 3 manipulation. This is particularly important in special environments such as microfluidics, biomedicine, and aerospace microgravity experiments, ensuring that the precise manipulation of droplets 3 is not affected by external temperature fluctuations.

[0108] In an exemplary embodiment, a computer device is provided. The computer device may be a server or a terminal. The internal structure diagram thereof may be as follows: Figure 7 As shown. The computer device includes a processor, a memory, an input / output interface (Input / Output, abbreviated as I / O) and a communication interface. The processor, memory and input / output interface are connected through a system bus, and the communication interface is connected to the system bus through the input / output interface. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and computer program in the non-volatile storage medium. The input / output interface of the computer device is used to exchange information between the processor and an external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a droplet merging self-bouncing enhancement control method is implemented.

[0109] Those skilled in the art will understand that Figure 7 The structure shown in the figure is merely a block diagram of a portion of the structure related to the solution of the present application and does not constitute a limitation on the computer device to which the solution of the present application is applied. A specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement. In an exemplary embodiment, a computer device is provided, including a memory and a processor. The memory stores a computer program, and the processor implements the steps of the above-mentioned method embodiments when executing the computer program.

[0110] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0111] Those skilled in the art will understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0112] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may include, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic units, data processing logic units based on quantum computing, and the like.

[0113] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0114] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A droplet merging and self-bouncing enhanced control device, characterized in that: The droplet merging and self-bouncing enhancement control device includes: a substrate surface, a controller, a signal generator and an ultrasonic transducer; The controller is connected to the signal generator and is used to control the signal generator to output an electrical signal; The ultrasonic transducer is connected to the signal generator and is used to output corresponding sound wave parameters according to the electrical signal; the sound wave parameters include: the frequency of the sound wave, the phase of the sound wave and the amplitude of the sound wave; The upper boundary of the ultrasonic transducer is provided with a substrate surface; the substrate surface is used for placing droplets, and a control space is determined according to the parameters of the droplets; the ultrasonic transducer is further used for generating an acoustic wave field in the control space according to the acoustic wave parameters, and controlling the acoustic wave field by changing the acoustic wave parameters so that the droplets enter the standing wave nodes and merge; and controlling the merged droplets to bounce to the target area in a preset droplet bouncing direction and speed by applying an acoustic wave field with a phase gradient; the parameters of the droplets include: the radius of the droplets and the fluid parameters of the droplets; the fluid parameters of the droplets include: the surface tension of the droplets, the density of the droplets, and the viscosity of the droplets.

2. The droplet merging and self-bouncing enhancement control device according to claim 1, characterized in that: The ultrasonic transducer includes multiple ultrasonic transducer units; each of the ultrasonic transducer units is connected to the signal generator respectively, and is used to adjust the corresponding driving voltage under the control of the electrical signal and generate a corresponding phase; the phases of the multiple ultrasonic transducer units constitute a phase gradient.

3. The droplet merging and self-bouncing enhancement control device according to claim 1, characterized in that: The frequency range of the acoustic wave field is 20 kHz to 2 MHz.

4. A droplet merging and self-bouncing enhancement control method, applied to the droplet merging and self-bouncing enhancement control device according to any one of claims 1 to 3, characterized in that: The droplet merging and self-bouncing enhanced control method comprises: setting the upper boundary of the ultrasonic transducer to the substrate surface and placing the liquid droplet on the substrate surface; Get the parameters of the droplet; Based on the droplet parameters, acoustic wave parameters corresponding to the control space and the standing wave nodes are obtained; the acoustic wave parameters include: the frequency of the acoustic wave, the phase of the acoustic wave, and the amplitude of the acoustic wave; Based on the acoustic wave parameters corresponding to the standing wave nodes, the signal generator is controlled by the controller to obtain the corresponding electrical signal; The ultrasonic transducer is controlled based on the electrical signal to obtain the acoustic wave field corresponding to the standing wave node in the control space; Based on the acoustic wave field corresponding to the standing wave node, the droplets are made to enter the standing wave node and merge; Based on the preset droplet bouncing direction and speed, the controller controls the signal generator, which in turn controls the ultrasonic transducer to obtain a phase gradient acoustic wave field. The phase gradient-based acoustic wave field controls the merged droplets to bounce to the target area at a preset droplet bouncing direction and speed.

5. The droplet merging and self-bouncing enhancement control method according to claim 4, characterized in that: The acoustic wave parameters corresponding to the control space and the standing wave nodes are obtained based on the droplet parameters, specifically including: Using the formula p = p0e jωt Determine the lower boundary of the control space; where p represents the sound pressure, p0 represents the amplitude of the sound wave, ω represents the angular frequency of the sound wave, t represents the time of sound wave change, and j represents an imaginary number; The upper and side boundaries of the control space are determined using the perfectly matched layer method.

6. The droplet merging and self-bouncing enhancement control method according to claim 5, characterized in that: The control of the ultrasonic transducer based on the electrical signal to obtain the acoustic wave field corresponding to the standing wave node in the control space specifically includes: Using the formula Determine the equation for the acoustic wave field; where the wave number c represents the speed of sound, π represents the circumference of a circle, and f represents the frequency of the sound wave. represents the gradient operation; According to the equation of the acoustic wave field, the finite element method and the finite difference method are used to determine the acoustic wave field.

7. The droplet merging and self-bouncing enhancement control method according to claim 6, characterized in that: The step of causing the droplets to enter the standing wave nodes and merge based on the acoustic wave field corresponding to the standing wave nodes specifically includes: Using the formula Convert the force of the acoustic wave field into acoustic wave force F; Based on the effect of acoustic wave force, the droplets enter the standing wave node and merge; Using the formula Determine the droplet merging time t c ; Where R represents the droplet radius, represents the acoustic pressure gradient, ρ represents the density of the droplet, d represents the diameter of the droplet, and γ represents the surface tension of the droplet.

8. The droplet merging and self-bouncing enhancement control method according to claim 7, characterized in that: The phase gradient-based acoustic wave field controls the merged droplets to bounce to the target area in a preset droplet bouncing direction and speed, specifically including: Using equations Calculate the motion of the droplet; Among them, F s represents the acoustic radiation force, u represents the fluid velocity field, μ represents the viscosity of the liquid, and t represents the time for the sound wave to change.

9. The droplet merging and self-bouncing enhancement control method according to claim 4, characterized in that: The phase gradient-based acoustic wave field controls the merged droplets to bounce to the target area in a preset droplet bouncing direction and speed, specifically including: Using the formula and Calculate the preset bounce direction of the droplet; Using the formula Calculate the preset droplet bounce velocity U j ; Wherein, X, Y, and Z represent the horizontal projection, longitudinal projection, and vertical projection of the preset droplet's bouncing direction, respectively. represents the phase difference required for the droplet to bounce to the target area with the preset bounce direction and speed, φ represents the phase field variable, x represents the horizontal coordinate of the droplet center of mass, y represents the vertical coordinate of the droplet center of mass, z represents the vertical coordinate of the droplet center of mass, V represents the volume of the droplet, and U y is the velocity component perpendicular to the plane.

10. A computer device comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the droplet merging and self-bouncing enhancement control method according to any one of claims 4 to 9.

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