Method and apparatus for continuous droplet generation

Abstract

This application provides a method for continuous droplet generation, comprising: introducing at least two immiscible fluids into a first flow channel, the at least two fluids comprising a first liquid and a second liquid in laminar flow, a laminar interface being formed between the first liquid and the second liquid; driving an acoustic device with a first power cycle, causing the acoustic device to periodically generate an acoustic beam toward the laminar interface, at least in the second liquid, the acoustic beam breaking through the laminar interface and entering the first liquid, forming droplets in the first liquid. Alternatively, the acoustic device can generate an acoustic beam at the laminar interface, inducing the second liquid to enter the first liquid and form droplets. The droplet generation method of this application is more flexible and more controllable.

Description

Technical Field

[0001] This application relates to the field of microfluidics, specifically to a method and apparatus for continuous droplet generation. Background Technology

[0002] In the field of microfluidic technology applications, microdroplets (droplets containing sample substances) have been used in numerous reactions and processes in chemistry and life sciences due to their advantages such as small size, stable reaction conditions, and avoidance of cross-contamination between samples. Examples include chemical analysis and synthesis, protein crystallization, cell embedding, and droplet PCR.

[0003] In the fabrication of microdroplets, they are typically generated in a liquid immiscible with the microdroplets to ensure their stable existence and transport. For example, Chinese patent application CN110170343A discloses a water-in-oil microdroplet fabrication system and method. This patent application utilizes the volume force exerted by high-frequency acoustic waves generated by a thin-film bulk acoustic resonator on the sample liquid, propelling the liquid towards the oil layer to form a liquid column at the interface. As the liquid column falls back, the viscous force in the oil phase and the interfacial tension (or interfacial force) clamp the liquid column, forming a water-in-oil droplet. In this scheme, the liquid column is driven by volume force to form a... Figure 13 As shown in the cone shape, the bottom of the liquid column has a large contact area and strong binding force with the water phase below the oil layer, making it difficult for the liquid column to detach from the water phase. Therefore, when the driving of the thin-film bulk acoustic resonator stops, it needs to form a water-in-oil droplet by utilizing the viscous force and interfacial tension when the liquid column falls back. On the other hand, as... Figure 13 As shown, because the liquid column is conical, it is difficult to control the position where the liquid column is snapped, that is, the control of the droplet size is relatively complex.

[0004] Therefore, how to provide an implementation scheme to achieve more flexible and controllable generation of droplets based on acoustics is a technical problem that needs to be solved. Summary of the Invention

[0005] In view of the above-mentioned problems of the prior art, this application provides a method and apparatus for continuous droplet generation, which can generate droplets more flexibly and controllably.

[0006] The first aspect of this application provides a method for continuous droplet generation, comprising: introducing at least two immiscible fluids into a first flow channel, the at least two fluids comprising a first liquid and a second liquid in laminar flow, a laminar interface being formed between the first liquid and the second liquid; driving an acoustic device with a first power cycle, causing the acoustic device to periodically generate a sound beam toward the laminar interface in at least the second liquid, the sound beam breaking through the laminar interface and entering the first liquid, and forming droplets in the first liquid, the droplets being composed of the second liquid.

[0007] A second aspect of this application provides a method for continuous droplet generation, comprising: introducing at least two immiscible fluids into a first flow channel, the at least two fluids comprising a first liquid, a second liquid, and a third liquid in laminar flow, a first laminar interface being formed between the first liquid and the second liquid, and a second laminar interface being formed between the second liquid and the third liquid; driving an acoustic device with a first power cycle, causing the acoustic device to periodically generate a sound beam toward the second laminar interface in at least the third liquid, the sound beam breaking through the second laminar interface and the first laminar interface and entering the first liquid, and forming droplets in the first liquid, the droplets being composed of the second liquid encapsulating the third liquid, or the droplets being composed of two closely adjacent droplets forming a single unit, the two droplets being composed of the second liquid and the third liquid.

[0008] A third aspect of this application provides a method for continuous droplet generation, comprising: introducing at least two immiscible fluids into a first flow channel, the at least two fluids comprising a first liquid and a second liquid in laminar flow, a laminar interface being formed between the first liquid and the second liquid; driving an acoustic device with a first power cycle to periodically generate an acoustic beam along the laminar interface at the laminar interface, the acoustic beam inducing a portion of the second liquid to enter the first liquid and form a droplet in the first liquid, the droplet being composed of the second liquid.

[0009] As one possible implementation of the first, second, or third aspect, the driving of the acoustic device with a first power cycle includes: driving the acoustic device with a first power to operate for at least one driving cycle, each driving cycle including a first phase and a second phase, driving the acoustic device to operate and generate ultrasonography of 0.5-30 GHz in the first phase, and stopping the driving of the acoustic device in the second phase; wherein the magnitude of the first power causes the acoustic device to generate the acoustic beam of a desired intensity in the first phase; the duration of the first phase is less than a threshold or the duty cycle of the first phase in one driving cycle is less than a threshold to suppress the generation of secondary flow in the first channel by the acoustic device.

[0010] As one possible implementation of the first, second, or third aspect, the acoustic beam forms droplets in the first liquid during its entry into the first liquid in one of the following ways: when the acoustic device is driven by a first power cycle, the acoustic beam forms droplets primarily based on the driving energy of the first stage of the driving cycle; or when the velocity difference between the two-phase flows of the first and second liquids causes the shear force at the first laminar interface to exceed a threshold, the acoustic beam forms droplets primarily based on the velocity difference.

[0011] As one possible implementation of the first, second, or third aspect, the size of the formed droplets is controlled by at least one of the following parameters: the first power, the magnitude of which is positively correlated with the droplet size; the duration of the first stage in the driving cycle, the length of which is positively correlated with the droplet size; the shear force formed by the velocity difference between the first and second liquids in the two-phase flow, the magnitude of which is negatively correlated with the droplet size; and the physical properties of the first liquid.

[0012] As one possible implementation of the first, second, or third aspect, when the signal duty cycle of the first stage in the driving cycle that drives the acoustic beam exceeds a threshold, the interfacial force at the laminar interface formed by the first liquid and the second liquid decreases.

[0013] As one possible implementation of the first, second, or third aspect, the viscosity of the first liquid is higher than that of the second liquid.

[0014] A fourth aspect of this application provides an apparatus for continuous droplet generation, comprising: a first flow channel; at least two sample flow channels located upstream of the first flow channel for introducing at least two immiscible fluids, the at least two fluids comprising a first liquid and a second liquid, flowing vertically within the first flow channel, with a horizontal laminar interface formed between the first liquid and the second liquid; an acoustic device at the bottom of the first flow channel, the acoustic device being driven periodically with a first power cycle to cause the acoustic device to periodically generate a sound beam toward the laminar interface, at least in the second liquid, the sound beam breaking through the laminar interface and entering the first liquid, forming droplets in the first liquid, the droplets being composed of the second liquid.

[0015] A fifth aspect of this application provides an apparatus for continuous droplet generation, comprising: a first flow channel; at least two sample flow channels located upstream of the first flow channel for introducing at least two immiscible fluids, the at least two fluids including a first liquid and a second liquid, flowing in a laminar manner from left to right within the first flow channel, with a vertical laminar interface formed between the first liquid and the second liquid; an acoustic device at the bottom of the first flow channel, the acoustic device being positioned directly opposite the laminar interface, the acoustic device being driven with a first power cycle to periodically generate an acoustic beam along the laminar interface, the acoustic beam inducing a portion of the second liquid to enter the first liquid and form droplets in the first liquid, the droplets being composed of the second liquid.

[0016] This application utilizes an acoustic beam to break through the laminar interface and generate droplets. Due to the strong focusing of the acoustic beam, it is generally cylindrical. The acoustic beam from the second liquid breaks through the laminar interface and enters the first liquid. The intersection of the acoustic beam and the laminar interface is very small (basically the cross-sectional size of the acoustic beam). Compared to the conical liquid column in the prior art, this reduces the difficulty of the acoustic beam detaching from the second liquid. Furthermore, since the detachment point is basically at the laminar interface, it is easier to quantify and control the amount of acoustic beam entering the first liquid, making it easier to control the droplet size and generate larger droplets. Additionally, the laminar interface is less disturbed, making it easier to recover and execute the next droplet generation process. This contributes to the stability of the size of each generated droplet. Moreover, because the generation of the next droplet can be executed quickly, the droplet flux is greater than that of the prior art. Finally, the small intersection of the acoustic beam and the laminar interface makes it easier to achieve the shear force of the laminar interface to detach the acoustic beam from the second liquid and form droplets compared to the prior art. In summary, this application allows for more flexible and controllable droplet generation. Attached Figure Description

[0017] Figure 1 These are images and diagrams illustrating jet and secondary flow phenomena.

[0018] Figure 2 This is a diagram of the acoustic beam generated in a liquid environment according to an embodiment of this application;

[0019] Figure 3 This is a timing diagram of the output signal of the driving device of the ultrasonic device provided in this application embodiment:

[0020] Figure 4 This is a schematic diagram of the driving device for the ultrasonic device provided in the embodiments of this application;

[0021] Figure 5 This is a schematic diagram illustrating the principle of a method for continuous droplet generation provided in the first embodiment of this application;

[0022] Figure 6 This is a schematic diagram illustrating the principle of a method for continuous droplet generation provided in the second embodiment of this application;

[0023] Figure 7 This is a schematic diagram illustrating the principle of a method for continuous droplet generation provided in the third embodiment of this application;

[0024] Figure 8 yes Figure 5 The illustrated embodiment shows a diagram of droplets generated by the first droplet generation method;

[0025] Figure 9 yes Figure 5The illustrated embodiment shows a droplet generated using the second droplet generation method;

[0026] Figure 10 yes Figure 5 The illustrated embodiment shows a diagram of droplets generated using the third droplet generation method;

[0027] Figure 11 yes Figure 7 The diagram shows the droplet generation in the illustrated embodiment;

[0028] Figure 12 This is a schematic diagram showing the dimensions of the ultrasonic device, which is an integrated acoustic resonator, provided in the embodiments of this application.

[0029] Figure 13 This is a schematic diagram illustrating the principle of forming a conical liquid column in Chinese patent application CN110170343A.

[0030] Figure 14 yes Figure 13 A schematic diagram illustrating the principle of droplet generation;

[0031] Figure 15 This is a schematic diagram illustrating the principle of droplet generation at the laminar interface in this application.

[0032] It should be understood that the dimensions and shapes of the blocks in the above structural diagrams are for reference only and should not constitute an exclusive interpretation of the embodiments of the present invention. The relative positions and inclusion relationships between the blocks presented in the structural diagrams are only schematic representations of the structural relationships between the blocks, and are not intended to limit the physical connection methods of the embodiments of the present invention. Detailed Implementation

[0033] The technical solutions provided in this application will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the system architecture and business scenarios provided in the embodiments of this application are mainly for illustrating possible implementations of the technical solutions of this application and should not be construed as the sole limitation on the technical solutions of this application. Those skilled in the art will recognize that the technical solutions provided in this application are equally applicable to similar technical problems as system architectures evolve and new business scenarios emerge.

[0034] It should be understood that the droplet continuous generation schemes provided in the embodiments of this application include methods, apparatus, and applications of droplet continuous generation. Since these technical solutions solve problems based on the same or similar principles, some repetitive details may not be repeated in the following descriptions of specific embodiments. However, it should be considered that these specific embodiments have mutual references and can be mutually referenced and combined.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. In case of any inconsistency, the meaning set forth in this specification or derived from the content described herein shall prevail. Furthermore, the terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application. To accurately describe the technical content of this application and to accurately understand the invention, the following explanations or definitions of the terms used in this specification are provided before describing specific embodiments:

[0036] 1) Acoustic devices, such as ultrasonic devices: A high-frequency resonator, which can be a device that generates mechanical vibration by applying voltage based on the piezoelectric effect. In this application, a piezoelectric resonator that generates ultrasonic waves of not less than 0.5 GHz (GHz is equivalent to gigahertz) during operation is used. Preferably, it is a piezoelectric resonator that generates ultrasonic waves of not less than 1 GHz and not more than 30 GHz during operation, for example, it can be 2 GHz to 2.5 GHz. Such piezoelectric resonators can be, for example, surface acoustic wave (SAW) devices, bulk acoustic wave (BAW) devices, etc. For example, when it is BAW, it can be a thin-film bulk acoustic wave resonator (FBAR), a solid-state assembled resonator (SMR), or a Lamb wave resonator (LWR). For ease of description, the piezoelectric resonator that can generate ultrasonic waves of not less than 0.5 GHz will be referred to as an ultrasonic device from now on.

[0037] 2) Jet phenomenon: This is a phenomenon that occurs when the sound waves from an ultrasonic device act on a liquid. The regional vibration generated at the working interface of the ultrasonic device can form a traveling wave in the liquid and exert a continuous thrust (i.e., volume force) on the local liquid in the liquid environment, causing at least a portion of the liquid to move in a straight line along the direction of sound wave propagation. This phenomenon of straight-line motion is called jet phenomenon.

[0038] Secondary flow phenomena, including eddies and thermal backflow, are another phenomenon generated when a supersonic device acts on a liquid. They include eddies (or micro vortices) caused by the local circulation of the liquid driven by the jet, and thermal backflow generated by the heating of the supersonic device.

[0039] The jet phenomenon and secondary flow phenomenon can be found in [reference needed]. Figure 1 The images and diagrams shown. Figure 1 The diagram shows a schematic of using eddies to capture particles.

[0040] 3) Acoustic Beam: In this application, the acoustic beam is generated based on an acoustic device, which can be one of the aforementioned ultrasonic devices. In this application, the acoustic beam is a unique type of jet phenomenon, characterized by the fluid moving at high speed along the direction of sound wave propagation and exhibiting a thin cylindrical shape within its path. Before significant attenuation, the acoustic beam is essentially in a laminar flow state with the surrounding liquid, exhibiting low mixing with the surrounding liquid. For example... Figure 2 An image of the resulting acoustic beam, captured by a high-speed camera, is shown. Figure 2 It can be seen that the acoustic beam has focusing properties and is no longer like... Figure 1 A cluster of jets, and Figure 2 It is clearly not visible in the middle Figure 1 Secondary flow phenomena in [the context of something].

[0041] The acoustic beam generation conditions in this embodiment are: the ultrasonic device is driven to operate for at least one driving cycle at a first power, each driving cycle including a first stage and a second stage (see...). Figure 3 The drive unit outputs a signal (in the first stage) to drive the ultrasonic device to generate a 0.5-30 GHz ultrasonic effect in the liquid environment, and stops driving the ultrasonic device in the second stage. The first power is sufficient to enable the ultrasonic device to generate a focused columnar acoustic beam perpendicular to the solid-liquid interface during the first stage. The duration of the first stage at the first power is less than a threshold, or the duty cycle of the first stage within one drive cycle is less than a threshold, to keep the temperature of the ultrasonic device within a controllable temperature threshold and to prevent the ultrasonic device from generating secondary flows (including eddies and backflows) in the liquid environment.

[0042] The intensity of the acoustic beam is related to the duration of the first stage (or the duty cycle within a driving cycle) and the intensity of the first power. The duration and power of the first stage determine the amount of energy input to the ultrasonic device within a driving cycle. For example, a shorter first stage duration better suppresses temperature and secondary current, but also results in a lower acoustic beam intensity (a shorter first stage duration means a shorter time for energy accumulation). Conversely, a higher first power leads to a higher acoustic beam intensity and consequently a higher temperature rise in the ultrasonic device. Therefore, applying a higher first power and a shorter first stage not only yields a higher intensity acoustic beam but also effectively suppresses the temperature and secondary current. Thus, when real-time control of the acoustic beam intensity is required, the preferred approach is to use a shorter, fixed first stage (e.g., the duty cycle of the first stage within the cycle is constant) and control the intensity of the generated acoustic beam by applying different amounts of first power. The alternative is to apply the same initial power and adjust different initial stage values ​​(such as the duty cycle of the initial stage value within the period) to control the intensity of the generated acoustic beam, or to adjust the initial stage value and the initial power simultaneously to control the intensity of the generated acoustic beam.

[0043] Once the liquid environment is determined and the ultrasonic device is selected, the relationship between the acoustic beam intensity and control parameters (first power and / or the periodic signal composed of the first and second stages) can be calibrated. In one scenario, if the periodic signal is a constant (i.e., the first and second stages are constant), calibrating the acoustic beam intensity and the first power can yield the magnitude of the first power and the acoustic beam intensity.

[0044] 4) Regarding the first stage within the drive cycle: In the first stage of the drive cycle, the drive unit continuously outputs several signals. For example, when the signal generator outputs a 1GHz signal, assuming the duration of the first stage is 1 microsecond, the drive unit will output 1000 signals during this first stage. The power applied during the first stage will be applied to these 1000 signals to drive the ultrasonic device. In the second stage of the drive cycle (corresponding to...) Figure 3 (Switch signal low level) No drive signal output.

[0045] In certain cases, such as when the first phase is executed only once and then the process ends, this is equivalent to or considered as executing only one drive cycle in this application, and therefore this situation is also within the scope of protection of this application.

[0046] 5) Driving device for special ultrasonic devices: such as Figure 4 One embodiment is shown, including a control unit and a drive unit, the drive unit comprising a signal generator and a power amplifier. Its signal output principle can be found in [reference needed]. Figure 3 As shown.

[0047] The signal generator is used to generate high-frequency signals. The frequency of the original high-frequency signal it generates is the same as or approximately the operating frequency (or the inherent frequency of the ultrasonic device) of the load.

[0048] A power amplifier is used to amplify the signal to be output so that it can drive a high-performance ultrasonic device.

[0049] The control unit can be a switching power supply, which controls the output switching signal. This switching signal can be a periodic signal, with a high level corresponding to the switching on phase (such as the conduction phase of the switching power supply's switching transistor). Figure 3 In the first stage, the switch-off stage corresponds to a low level, which is... Figure 3 The second stage involves controlling the operating voltage or amplification factor input to the power amplifier to achieve different output powers, which is the first power mentioned above. The first power can also be understood as the average energy density input to the ultrasonic device during a driving cycle (which consists of a first stage and a second stage). Since the energy level is related to power and time, the amount of energy input to the ultrasonic device during a driving cycle is related to the level of the first power, the duration of the first stage, or its duty cycle.

[0050] 6) Laminar flow: In this application, it refers to the laminar flow of at least two immiscible liquids in a flow channel, which can be vertical or horizontal.

[0051] 7) Positive and negative correlations between parameters: Taking two parameters as an example, positive correlation means that one parameter increases as the other parameter increases, and negative correlation means that one parameter increases as the other parameter decreases. The parameters mentioned in this application cannot be infinitely small or infinitely large. Therefore, unless otherwise specified, the parameter values ​​mentioned in this application refer to values ​​within a reasonable range. For example, when describing a positive correlation between parameter A and parameter B, it means that within a certain range, parameter A and parameter B are positively correlated, and it can be predicted that beyond this range, parameter B will no longer be positively correlated with parameter A (after parameter A increases by a certain value, B reaches a saturation state, and then parameter B will no longer increase with the increase of parameter A). This range of values ​​is then considered a reasonable range.

[0052] The acoustic beam and related technologies for driving ultrasonic devices to generate acoustic beams, as described above, can also be found in the relevant description in Chinese patent application number CN2024108322079.

[0053] In the prior art, Chinese patent application CN110170343A discloses a water-in-oil microdroplet manufacturing system and method. This patent application utilizes the volume force exerted by high-frequency acoustic waves generated by a thin-film bulk acoustic resonator on the sample liquid, propelling the liquid towards the oil layer to form a liquid column at the interface. As the liquid column falls back, the viscous force of the oil relative to the liquid column and the interfacial tension between the oil and water clamp the liquid column, forming water-in-oil droplets. The volume force utilized in this patent application, i.e., the continuous thrust generated by the jet phenomenon on the local liquid, is used to generate the liquid column. Because the jet itself has a relatively large range of action, the liquid column morphology exhibited at the oil-water interface is as follows: Figure 13 The illustrated liquid column is conical in shape. The bottom of the liquid column has a large contact area and strong binding force with the sample liquid below the oil layer, making it difficult for the liquid column to detach directly from the sample liquid. Therefore, it is necessary to stop driving the thin-film bulk acoustic resonator and use the viscosity of the oil relative to the liquid column and the oil-water interfacial tension to clamp the liquid column at a certain point in the conical shape, forming an oil-in-water droplet. For example... Figure 14 A schematic diagram of its formation of droplets is shown.

[0054] This application provides an improved solution for continuous droplet generation. The droplet generation method provided is not limited to generating droplets when the acoustic device stops working; it offers greater flexibility in droplet generation and easier control over the size of the generated droplets. The main principle of the continuous droplet generation method provided is as follows: at least two immiscible fluids are introduced into a flow channel. An acoustic device periodically generates an acoustic beam towards the laminar interface in one phase of the fluid. This periodically generated acoustic beam breaks through the laminar interface and enters the other phase, forming continuous droplets. Alternatively, an acoustic device periodically generates an acoustic beam along the laminar interface of the two fluids. This periodically generated acoustic beam induces a portion of the liquid in one phase to enter the other phase, forming continuous droplets. The following detailed description, in conjunction with the accompanying drawings and embodiments, further illustrates this application.

[0055] The first embodiment of this application provides a method for continuous droplet generation, including:

[0056] At least two immiscible fluids are introduced into the first flow channel, the at least two fluids comprising a first liquid and a second liquid in laminar flow, and a laminar interface is formed between the first liquid and the second liquid;

[0057] The acoustic device is driven with a first power cycle, causing the acoustic device to periodically generate an acoustic beam toward the laminar interface, at least in the second liquid. The acoustic beam breaks through the laminar interface and enters the first liquid, forming droplets in the first liquid, the droplets being composed of the second liquid.

[0058] Among them, such as Figure 5One embodiment of the first embodiment described above is shown, specifically an embodiment in which a two-phase fluid is introduced into a first flow channel. In some embodiments, Figure 5 This can be a side view, where the two-phase fluids are layered vertically within a first flow channel, and the acoustic device is located at the bottom of the first flow channel (e.g., on a substrate forming the bottom of the flow channel). In other embodiments, Figure 5 It can be a top view, in which the two-phase fluid is layered on the left and right sides in the first flow channel, and the acoustic device is located on the sidewall of the first flow channel (for example, on the substrate forming the sidewall of the flow channel).

[0059] Among them, reference Figure 2 The acoustic beam shown is generally columnar in shape. This is to illustrate... Figure 2 The acoustic beam shown is generated in a static liquid. Figure 5 In the illustrated embodiment, the acoustic beam will experience some deflection due to the presence of the two fluid velocities. However, because the intensity of the acoustic beam generated in the second liquid needs to be controlled so that its velocity before entering the first liquid can reach the speed required to overcome the constraints of the laminar interface, the acoustic beam's velocity before entering the first liquid is much higher than the velocity of the two-phase flow, and the deflection of the acoustic beam before entering the first liquid can be ignored. After the acoustic beam enters the first liquid, the factors that cause it to generate droplets are related to the intensity of the acoustic beam (or the remaining energy of the acoustic beam after entering the first liquid), the laminar interface shear force formed by the velocity difference between the two phase flows, and the physical properties of the first liquid.

[0060] For a better understanding of this application, please refer to... Figure 14 The diagram shown illustrates the principle of droplet generation in the existing scheme. Figure 15 This diagram illustrates the principle of droplet generation based on acoustic beam penetration of the laminar flow interface in this application (for ease of comparison and analysis). Figure 15 (Without considering the flow of the first and second liquids), it can be seen that due to the strong focusing of the acoustic beam, it is generally columnar. The acoustic beam of the second liquid breaks through the laminar interface and enters the first liquid. The intersection of the acoustic beam and the laminar interface is very small (basically the cross-sectional size of the acoustic beam). Figure 14 The conical liquid column in the liquid reduces the difficulty of the acoustic beam detaching from the second liquid. Furthermore, since the detachment point is essentially at the laminar interface, it makes it easier to quantify and control the amount of acoustic beam entering the first liquid, thus making it easier to control the droplet size. Figure 14 It is easier to generate larger droplets; furthermore, the area of ​​the laminar interface subject to disturbance is relatively small. Figure 14 Smaller size allows for easier recovery of the laminar interface, facilitating the generation of the next droplet. This promotes stable droplet size and, due to the rapid generation of the next droplet, compared to... Figure 14 This method generates a larger droplet flux; furthermore, when considering laminar flow, compared to... Figure 14 The method of generating droplets is a conical liquid column at the laminar interface. Figure 15 The intersection of the acoustic beam-driven liquid column and the laminar interface is very small, making it easier to achieve the separation of the acoustic beam from the second liquid and the formation of droplets through the shear force of the laminar interface.

[0061] In some embodiments, the thickness of the second liquid is less than a threshold value, which allows the acoustic beam generated in the second liquid to maintain a flow velocity (or energy) that can break through the laminar interface when it reaches the laminar interface.

[0062] A second embodiment of this application also provides a method for continuous droplet generation, wherein, compared to the first embodiment, at least two phases of fluid include a first liquid, a second liquid, and a third liquid in laminar flow. Specifically, the method includes:

[0063] At least two immiscible fluids are introduced into a first flow channel. The at least two fluids include a first liquid, a second liquid, and a third liquid in laminar flow. A first laminar interface is formed between the first liquid and the second liquid, and a second laminar interface is formed between the second liquid and the third liquid.

[0064] An acoustic device is driven with a first power cycle, causing it to periodically generate an acoustic beam toward the second laminar interface, at least within a third liquid. This acoustic beam penetrates both the second and first laminar interfaces and enters the first liquid, forming a first droplet. This first droplet contains adjacent second and third droplets, which are respectively composed of a second liquid and a third liquid. In other embodiments, the first droplet formed in the first liquid contains a second droplet, and the second droplet encapsulates a third droplet, which is also composed of a second liquid and a third liquid. This configuration is more common than the first droplet containing adjacent second and third droplets. For example, the first, second, and third liquids can be inorganic reagents such as water, mineral oil, silicone oil, fluorinated oil, various biological agents, etc. For instance, in one embodiment, the first liquid is a DNA solution, the second liquid is mineral oil, and the third liquid is water.

[0065] Among them, such as Figure 6 One embodiment of the second embodiment described above is shown, specifically an embodiment in which a three-phase fluid is introduced into a first flow channel. In some embodiments, Figure 6 This can be a side view, where the three-phase fluid is layered vertically within a first flow channel, and the acoustic device is located at the bottom of the first flow channel (e.g., on a substrate forming the bottom of the flow channel). In other embodiments, Figure 6 It can be a top view, in which the two-phase fluids are layered sequentially from left to right in the first flow channel, and the acoustic device is located on the sidewall of the first flow channel (for example, on the substrate forming the sidewall of the flow channel).

[0066] for Figure 6 In the embodiments shown, in some embodiments, the first droplet can be formed in the first liquid as described above. In other embodiments, the intensity of the acoustic beam can be controlled so that the acoustic beam generated in the third liquid and directed towards the second laminar interface only breaks through the second laminar interface, generating a droplet in the second laminar flow, the droplet being composed of the third liquid. That is, different droplets can be generated in the first liquid or in the second liquid by controlling the intensity of the acoustic beam.

[0067] In some embodiments, the total thickness of the third liquid and the second liquid is less than a threshold value, which allows the acoustic beam generated in the third liquid to maintain a flow velocity sufficient to penetrate the laminar interface when it breaks through the second liquid and reaches the laminar interface between the first and second liquids. Similarly, more phase fluids can be introduced into the first flow channel so that the generated droplets comprise multiple layers, with the liquids in each droplet corresponding sequentially from the inside out to the phases extending from the direction directly opposite the acoustic device.

[0068] The third embodiment of this application provides another method for continuous droplet generation, including:

[0069] At least two immiscible fluids are introduced into the first flow channel, the at least two fluids comprising a first liquid and a second liquid in laminar flow, and a laminar interface is formed between the first liquid and the second liquid;

[0070] The acoustic device is driven by a first power cycle, causing the acoustic device to periodically generate an acoustic beam along the laminar interface at the laminar interface. The acoustic beam induces a portion of the second liquid to enter the first liquid and form droplets in the first liquid, the droplets being composed of the second liquid.

[0071] Among them, such as Figure 7 One embodiment of the third embodiment described above is shown, specifically an embodiment in which a two-phase fluid is introduced into a first flow channel. In some embodiments, Figure 7 This can be a side view, where the two-phase fluids are layered vertically within a first flow channel, and the acoustic device is located on the sidewall of the first flow channel (e.g., on a substrate forming the sidewall of the flow channel). In other embodiments, Figure 7 This can be a top view, where the two-phase fluids are layered horizontally along their direction of extension within the first flow channel, and the acoustic devices are located at the bottom of the first flow channel (e.g., on a substrate forming the bottom of the flow channel). Figure 11 This diagram illustrates a method for generating droplets, shown as a top view. The two-phase fluids are layered horizontally along their extension direction within the first flow channel. Figure 11In the example, the acoustic device is a bulk acoustic wave device located at the interface of two phase flows. The first power driving the acoustic device is 0.5W, the driving period is 2ms, the first stage (i.e., pulse width) is 1ms, the first liquid is mineral oil with a flow rate of 3ul / min, and the second liquid is water with a flow rate of 1ul / min.

[0072] for Figure 7 In the embodiments shown, in some embodiments, the viscosity of the first liquid is higher than the viscosity of the second liquid. In other embodiments, the viscosity of the first liquid may be lower than the viscosity of the second liquid.

[0073] In some embodiments, such as Figure 5 or Figure 6 In the illustrated embodiments, the acoustic beam of the acoustic device may be perpendicular to the laminar interface; in other embodiments, the acoustic beam may also be at an acute or obtuse angle to the laminar interface in space.

[0074] In some embodiments, such as... Figure 7 In the illustrated embodiment, the acoustic beam of the acoustic device is located at the laminar interface. In other embodiments, the acoustic beam may also be spatially parallel to the laminar interface and spaced less than a threshold value, which enables... Figure 7 In some embodiments, the second liquid is induced to enter the first liquid to form droplets. Figure 7 In the illustrated embodiments, the acoustic beam can be perpendicular to the direction of liquid flow, or it can be at an acute or obtuse angle.

[0075] In some embodiments, the acoustic device is driven with a first power cycle to generate an acoustic beam. The magnitude of the first power is described in the foregoing introduction to the acoustic beam and driving cycle, and will not be repeated here. Furthermore, the magnitude of the first power should also be such that the generated acoustic beam can break through the aforementioned laminar interface to form droplets in the target liquid (such as the first liquid).

[0076] The preceding section introduced the factors that cause droplet formation after the acoustic beam enters the first liquid (such as droplet size, droplet spacing, droplet velocity, flux, etc.). These factors are related to the intensity of the acoustic beam (or the remaining energy of the acoustic beam after entering the first liquid), the shear force at the laminar interface formed by the velocity difference between the two phases, and the physical properties of the first liquid. Specifically, in some embodiments, during the process of the acoustic beam breaking through the laminar interface and entering the first liquid, droplets are formed in the first liquid through at least one of the following a1-a2 methods. When the acoustic beam does not break through the laminar interface, droplets can be formed through the following a3 method:

[0077] a1. When the acoustic device is driven with a first power cycle, the droplet is formed based on the driving energy of the first stage of the driving cycle. In this method, the first power allows the acoustic beam to penetrate the laminar interface and enter the first liquid, as can be referred to... Figure 15 The schematic diagram shows that the acoustic beam entering the first liquid can form droplets. This method (a1) can be understood as using the force of the acoustic beam generated by the acoustic device to primarily generate droplets. For example, Figure 8 A diagram showing droplet formation at the rising edge (i.e., the first stage) is shown. Figure 8 It is a top view. Figure 8 In the example, the driving power is 0.5W.

[0078] a2. The velocity difference between the first and second liquid phases causes the shear force at the first laminar interface to exceed a threshold, causing the acoustic beam to form droplets. In this method, compared to method a1, the velocity difference between the two phases is larger, resulting in a larger shear force at the laminar interface, thus shearing the acoustic beam and forming droplets. Method a2 can be understood as droplet formation primarily driven by the two-phase shear force generated by the inertial fluid. Figure 9 The diagram shows the formation of droplets dominated by shear forces at the laminar interface. Figure 9 In the example, the second liquid is water with a flow rate of 1 μL / min, and the second liquid is mineral oil with a flow rate of 8 μL / min.

[0079] a3. Additionally, when the acoustic beam does not break through the laminar interface, it can also be based on... Figure 14 Droplets are generated in a similar manner. For example, if the initial power is relatively weak, in the first stage of the driving cycle, the generated acoustic beam does not break through the laminar interface. The tension of the laminar interface and the thrust of the acoustic beam form a conical laminar interface that bulges towards the first liquid (due to the focusing property of the acoustic beam, the diameter of the conical base formed by this acoustic beam is much smaller than the diameter of the conical base formed by the jet). In the second stage of the driving cycle, the bulge falls back to form the droplets (the principle is similar). Figure 14 The principle illustrated will not be repeated here. This method (a3) ​​can be understood as the droplet formation being primarily driven by the viscous force of the first liquid and the interfacial forces at the laminar interface. For example... Figure 10 The diagram shows the formation of droplets in the second stage before the acoustic beam breaks through the laminar interface. Figure 10 In the example, the driving power is 0.25W.

[0080] In some embodiments, the droplet size formed when the acoustic beam breaks through the laminar interface is controlled by at least one of the following parameters b1-b4:

[0081] b1. The first power driving the acoustic device, wherein the magnitude of the first power is positively correlated with the droplet size. (Refer to...) Figure 15 The reason for this can be explained as follows: the higher the first power, the longer the acoustic beam that drives the second liquid to form, that is, the more acoustic beam enters the first liquid, and therefore the larger the droplets formed.

[0082] b2. The duration of the first stage in the driving cycle, wherein the length of the first stage is positively correlated with the droplet size. (Refer to...) Figure 15 and Figure 3 The reason for this can be explained as follows: the first stage is the effective time for driving, so it lasts a long time and pushes more sound beams into the first liquid, thus forming larger droplets.

[0083] b3. The shear force formed by the velocity difference between the first and second liquid phases, wherein the magnitude of the velocity difference is negatively correlated with the droplet size. Conversely, the velocity difference and shear force are positively correlated; the larger the velocity difference, the greater the shear force. A greater shear force makes it easier to cut off the acoustic beam at the laminar interface. Therefore, the magnitude of the velocity difference is negatively correlated with the droplet size.

[0084] b4. The physical properties of the first liquid, including viscosity and temperature. The viscosity is positively correlated with the droplet size. Temperature affects viscosity; therefore, temperature is negatively correlated with droplet size.

[0085] b5. Regarding the case of b2, another phenomenon occurred in the experiment: when the signal duty cycle length of the first stage in the driving cycle that drives the formation of the acoustic beam increases beyond a threshold, such as 90%-100%, the droplet size will decrease. One possible reason for this is that the second stage (i.e., the non-driving stage) is too short, which prevents the laminar interface formed by the first liquid and the second liquid from recovering in time, resulting in a decrease in interfacial force and thus a decrease in the size of the generated droplets.

[0086] In some embodiments, the droplet size formed by the acoustic beam not breaking through the laminar interface is related to the interfacial force at the laminar interface formed by the first liquid and the second liquid, and the magnitude of the interfacial force is positively correlated with the droplet size. (Refer to...) Figure 14 The reason for this can be explained as follows: the greater the interfacial force, the easier it is to cut off the liquid column near the bottom of the cone, thus forming a larger droplet.

[0087] In some embodiments, the first liquid and the second liquid can be water, various biological reagents such as DNA solution, solutions containing cells, inorganic solutions such as calcium chloride, or oils, and can be a random combination of two immiscible liquids. For example, in one embodiment, the first liquid can be an oil phase and the second liquid can be an aqueous phase. The viscosity of the first liquid can be higher or lower than that of the second liquid.

[0088] In some embodiments, the second liquid may be water or other liquids that are immiscible with the first liquid. In other embodiments, the second liquid may be a liquid containing other substances, such as a liquid containing certain particles, thereby enabling the generated droplets to include the particles. When the droplets include particles, the particles in the droplets can be screened, analyzed, chemically reacted, etc., downstream based on the droplets.

[0089] In some embodiments, the aforementioned microparticles can refer to any microscopic particles located in a liquid environment that are distinguishable from the liquid environment (i.e., insoluble) and capable of movement within the liquid environment. In some embodiments, the particle diameter can range from the nanometer scale to the millimeter scale, and the microparticles can include cells, molecules, molecular polymers, DNA, nucleic acids, etc. In some embodiments, the microparticles can be fluorescently labeled microparticles, referred to herein as fluorescent microparticles. The fluorescent microparticles include a microparticle core and a fluorescent layer or are doped with fluorescent substances. The microparticle core can be silica, magnetic iron oxide, polystyrene, polylactic acid, polyacrylic acid, polyamides, polyaniline, gelatin, calcium carbonate, barium carbonate, cellulose, pectin, starch, albumin, chitosan, stained cells or bacteria, etc., and the fluorescent layer can be a fluorescent dye, quantum dots, antibody proteins labeled with fluorescent molecules, or nucleic acids, etc.

[0090] In some embodiments, the aforementioned flow channels, such as the first flow channel and the sample flow channel, can be closed flow channels with a top cover, such as microchannels, or they can be open flow channels without a top cover.

[0091] The fourth embodiment of this application provides a device for continuous droplet generation, which can be found in [reference 1]. Figure 5 or Figure 6 The schematic diagram shown includes: a first flow channel; at least two sample flow channels located upstream of the first flow channel for introducing at least two immiscible fluids, the at least two fluids including a first liquid and a second liquid, which flow in laminar flow in the first flow channel, forming a horizontal laminar interface between the first liquid and the second liquid; an acoustic device at the bottom of the first flow channel, driven by a first power cycle, causing the acoustic device to periodically generate a sound beam toward the laminar interface, at least in the second liquid, the sound beam breaking through the laminar interface and entering the first liquid, forming droplets in the first liquid, the droplets being composed of the second liquid.

[0092] The fifth embodiment of this application provides a device for continuous droplet generation, which can be found in [reference 1]. Figure 7The schematic diagram shown includes: a first flow channel; at least two sample flow channels located upstream of the first flow channel for introducing at least two immiscible fluids, the at least two fluids including a first liquid and a second liquid, which are in laminar flow from left to right within the first flow channel, and a vertical laminar interface is formed between the first liquid and the second liquid; an acoustic device is located at the bottom of the first flow channel, the acoustic device is positioned opposite the laminar interface, and the acoustic device is driven with a first power cycle to periodically generate a sound beam along the laminar interface, the sound beam inducing a portion of the second liquid to enter the first liquid and form droplets in the first liquid, the droplets being composed of the second liquid.

[0093] In some embodiments, the flow channel material includes polydimethylsiloxane, optical glass, organic materials, etc. In some embodiments, the acoustic device may be an ultra-ultrasonic device operating at 0.5 GHz to 50 GHz, preferably an ultra-ultrasonic device operating at 1 GHz to 5 GHz, and more preferably an ultra-ultrasonic device operating at 2 GHz to 2.5 GHz.

[0094] In some embodiments, the direction of the generated acoustic beam can be perpendicular to the surface of the ultrasonic device, for example, when the ultrasonic device is a bulk acoustic wave (BAW) device. This is because the piezoelectric constant d33 of the BAW piezoelectric layer (such as an AlN layer) is directional along the thickness direction, i.e., the vibration direction of the BAW piezoelectric layer, and thus the sound wave propagation direction is perpendicular to the BAW. In other embodiments, the direction of the acoustic beam can be at an acute angle to the surface of the ultrasonic device. For example, when the ultrasonic device is a surface acoustic wave (SAW) device, the angle between the acoustic beam direction, i.e., the sound wave propagation direction, and the SAW surface is approximately between 30 and 50 degrees.

[0095] In some embodiments, when the acoustic device is an ultrasonic device, it can be a polygon, especially a polygon with an odd number of sides. For example, in one embodiment, it can be a regular pentagon or a scalene pentagon. In other embodiments, it can be an olive-shaped, triangular, elliptical, rhomboid, semicircular, or any combination of shapes of any size polygon.

[0096] The area of ​​the ultra-ultrasonic device (referring to the radial dimension, not the thickness dimension, i.e., the device interface dimension) is approximately 10-1,000,000 μm. 2 Preferably, it is about 100-40000μm 2 More preferably 1000–10000 μm 2 In order to intuitively understand the dimensions of ultrasonographic devices, Figure 12A dimensional diagram of the ultra-ultrasonic device as an integrated acoustic resonator is shown. The size of the ultra-ultrasonic device is negatively correlated with the achievable resonant frequency; therefore, reducing the size can increase the resonant frequency. In other embodiments, the resonant frequency of the ultra-ultrasonic device can also be changed by altering the shape of the device, such as the number of polygonal elements, the angles between adjacent sides, and the length of each side.

[0097] The diameter of the generated acoustic beam is related to the parameters of the ultrasonic device itself. The smaller the area (radial dimension or interface dimension) of the ultrasonic device, the smaller the acoustic beam diameter. Smaller microscales also result in better sound wave focusing. Specifically, under the same initial power application, using a smaller microscale in the ultrasonic device results in a stronger acoustic beam, a smaller beam diameter, and a faster response speed (the time to generate the acoustic beam).

[0098] Specifically, for the driving device, its output first power satisfies the condition that the acoustic beam can penetrate the laminar interface and enter the first liquid. The output first power is approximately 0.1-500W, preferably 2-50W, and more preferably 5-15W. The specific power range used is selected based on the desired acoustic beam intensity. The waveform of the signal generator can be a rectangular wave (e.g.,...). Figure 3 The signals shown include square waves, sawtooth waves, sharp pulses (or triangular waves), stepped waves, sine waves, or half-waves. The output signal of the corresponding drive unit is modulated into sawtooth waves, sharp pulses (or triangular waves), stepped waves, sine waves, or half-waves.

[0099] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods are not limited to the above embodiments and can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0100] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0101] Furthermore, the terms "first, second, third, etc." or similar terms such as module A, module B, and module C used in the specification and claims are only used to distinguish similar objects and do not represent a specific ordering of objects. It is understood that, where permissible, a specific order or sequence may be interchanged so that the embodiments of this application described herein can be implemented in an order other than that illustrated or described herein.

[0102] In the above description, the labels of the steps involved, such as S10, S20, etc., do not mean that the steps will necessarily be executed. The order of the steps can be interchanged or executed simultaneously if permitted.

[0103] The term "comprising" as used in the specification and claims should not be construed as limiting itself to what follows; it does not exclude other elements or steps. Therefore, it should be interpreted as specifying the presence of the mentioned feature, integral, step, or component, but does not exclude the presence or addition of one or more other features, integrals, steps, or components, or groups thereof. Thus, the statement "device comprising means A and B" should not be limited to a device consisting solely of components A and B.

[0104] The terms "an embodiment" or "an embodiment" as used in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in at least one embodiment of this application. Therefore, the terms "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics can be combined in any suitable manner, as will be apparent to those skilled in the art from this disclosure.

[0105] Note that the above are merely preferred embodiments and the technical principles employed in this application. Those skilled in the art will understand that this application is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this application. Therefore, although this application has been described in detail through the above embodiments, this application is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of this application, all of which fall within the scope of protection of this application.

Claims

1. A method for continuous droplet generation, characterized in that, include: At least two immiscible fluids are introduced into the first flow channel, the at least two fluids comprising a first liquid and a second liquid in laminar flow, and a laminar interface is formed between the first liquid and the second liquid; The acoustic device is driven with a first power cycle, causing the acoustic device to periodically generate an acoustic beam toward the laminar interface, at least in the second liquid. The acoustic beam breaks through the laminar interface and enters the first liquid, forming droplets in the first liquid, the droplets being composed of the second liquid.

2. The method according to claim 1, characterized in that, The acoustic device driven by the first power cycle includes: The acoustic device is driven to operate at a first power for at least one driving cycle, each driving cycle including a first stage and a second stage, wherein the acoustic device is driven to operate in the first stage to generate a supersonography of 0.5-30 GHz, and the driving of the acoustic device is stopped in the second stage. Wherein, the magnitude of the first power causes the acoustic device to generate the acoustic beam of the desired intensity during the first phase; the duration of the first phase is less than a threshold or the duty cycle of the first phase during a drive cycle is less than a threshold, so as to suppress the generation of secondary flow by the acoustic device in the first channel.

3. The method according to claim 2, characterized in that, As the acoustic beam enters the first liquid, it forms droplets in the first liquid through one of the following methods: When the acoustic device is driven in the first power cycle, the energy of the drive in the first stage of the drive cycle dominates the formation of the droplets from the acoustic beam. When the velocity difference between the first liquid and the second liquid in the two-phase flow causes the shear force at the first laminar interface to exceed a threshold, the acoustic beam is formed into droplets primarily due to the velocity difference.

4. The method according to claim 2 or 3, characterized in that, The size of the formed droplets is controlled by at least one of the following parameters: The first power is positively correlated with the droplet size; The duration of the first stage in the driving cycle is positively correlated with the droplet size. The shear force formed by the velocity difference in the two-phase flow of the first liquid and the second liquid, wherein the magnitude of the velocity difference is negatively correlated with the droplet size; The physical properties of the first liquid.

5. The method according to claim 4, characterized in that, When the signal duty cycle of the first stage in the driving cycle that drives the formation of the acoustic beam exceeds a threshold, the interfacial force at the laminar interface formed by the first liquid and the second liquid decreases.

6. The method according to claim 1, characterized in that, The viscosity of the first liquid is higher than that of the second liquid.

7. A method for continuous droplet generation, characterized in that, include: At least two immiscible fluids are introduced into a first flow channel. The at least two fluids include a first liquid, a second liquid, and a third liquid in laminar flow. A first laminar interface is formed between the first liquid and the second liquid, and a second laminar interface is formed between the second liquid and the third liquid. The acoustic device is driven with a first power cycle, causing the acoustic device to periodically generate an acoustic beam toward the second laminar interface in at least the third liquid. The acoustic beam breaks through the second laminar interface and the first laminar interface and enters the first liquid, forming droplets in the first liquid. The droplets are composed of a second liquid enveloping a third liquid, or the droplets are composed of two closely adjacent droplets that are integrated into one, and the two droplets are composed of the second liquid and the third liquid.

8. The method according to claim 7, characterized in that, The acoustic device driven by the first power cycle includes: The acoustic device is driven to operate at a first power for at least one driving cycle, each driving cycle including a first stage and a second stage, wherein the acoustic device is driven to operate in the first stage to generate a supersonography of 0.5-30 GHz, and the driving of the acoustic device is stopped in the second stage. Wherein, the magnitude of the first power causes the acoustic device to generate the acoustic beam of the desired intensity during the first phase; the duration of the first phase is less than a threshold or the duty cycle of the first phase during a drive cycle is less than a threshold, so as to suppress the generation of secondary flow by the acoustic device in the first channel.

9. The method according to claim 8, characterized in that, As the acoustic beam enters the first liquid, it forms droplets in the first liquid through one of the following methods: When the acoustic device is driven in the first power cycle, the energy of the drive in the first stage of the drive cycle dominates the formation of the droplets from the acoustic beam. When the velocity difference between the first liquid and the second liquid in the two-phase flow causes the shear force at the first laminar interface to exceed a threshold, the acoustic beam is formed into droplets primarily due to the velocity difference.

10. The method according to claim 8 or 9, characterized in that, The size of the formed droplets is controlled by at least one of the following parameters: The first power is positively correlated with the droplet size; The duration of the first stage in the driving cycle is positively correlated with the droplet size. The shear force formed by the velocity difference in the two-phase flow of the first liquid and the second liquid, wherein the magnitude of the velocity difference is negatively correlated with the droplet size; The physical properties of the first liquid.

11. The method according to claim 10, characterized in that, When the signal duty cycle of the first stage in the driving cycle that drives the formation of the acoustic beam exceeds a threshold, the interfacial force at the laminar interface formed by the first liquid and the second liquid decreases.

12. The method according to claim 7, characterized in that, The viscosity of the first liquid is higher than that of the second liquid.

13. A method for continuous droplet generation, characterized in that, include: At least two immiscible fluids are introduced into the first flow channel, the at least two fluids comprising a first liquid and a second liquid in laminar flow, and a laminar interface is formed between the first liquid and the second liquid; The acoustic device is driven by a first power cycle, causing the acoustic device to periodically generate an acoustic beam along the laminar interface at the laminar interface. The acoustic beam induces a portion of the second liquid to enter the first liquid and form droplets in the first liquid, the droplets being composed of the second liquid.

14. The method according to claim 13, characterized in that, The acoustic device driven by the first power cycle includes: The acoustic device is driven to operate at a first power for at least one driving cycle, each driving cycle including a first stage and a second stage, wherein the acoustic device is driven to operate in the first stage to generate a supersonography of 0.5-30 GHz, and the driving of the acoustic device is stopped in the second stage. Wherein, the magnitude of the first power causes the acoustic device to generate the acoustic beam of the desired intensity during the first phase; the duration of the first phase is less than a threshold or the duty cycle of the first phase during a drive cycle is less than a threshold, so as to suppress the generation of secondary flow by the acoustic device in the first channel.

15. The method according to claim 14, characterized in that, As the acoustic beam enters the first liquid, it forms droplets in the first liquid through one of the following methods: When the acoustic device is driven in the first power cycle, the energy of the drive in the first stage of the drive cycle dominates the formation of the droplets from the acoustic beam. When the velocity difference between the first liquid and the second liquid in the two-phase flow causes the shear force at the first laminar interface to exceed a threshold, the acoustic beam is formed into droplets primarily due to the velocity difference.

16. The method according to claim 14 or 15, characterized in that, The size of the formed droplets is controlled by at least one of the following parameters: The first power is positively correlated with the droplet size; The duration of the first stage in the driving cycle is positively correlated with the droplet size. The shear force formed by the velocity difference in the two-phase flow of the first liquid and the second liquid, wherein the magnitude of the velocity difference is negatively correlated with the droplet size; The physical properties of the first liquid.

17. The method according to claim 16, characterized in that, When the signal duty cycle of the first stage in the driving cycle that drives the formation of the acoustic beam exceeds a threshold, the interfacial force at the laminar interface formed by the first liquid and the second liquid decreases.

18. The method according to claim 13, characterized in that, The viscosity of the first liquid is higher than that of the second liquid.

19. A device for continuous droplet generation, characterized in that, include: First flow channel; At least two sample channels located upstream of the first flow channel are used to introduce at least two immiscible fluids, the at least two fluids including a first liquid and a second liquid, which flow in laminar flow in the first flow channel, and a horizontal laminar interface is formed between the first liquid and the second liquid. The bottom of the first flow channel has an acoustic device. The acoustic device is driven by a first power cycle, causing the acoustic device to periodically generate an acoustic beam toward the laminar interface, at least in the second liquid. The acoustic beam breaks through the laminar interface and enters the first liquid, forming droplets in the first liquid. The droplets are composed of the second liquid.

20. A device for continuous droplet generation, characterized in that, include: First flow channel; At least two sample channels located upstream of the first flow channel are used to introduce at least two immiscible fluids, the at least two fluids including a first liquid and a second liquid, which are in a laminar flow from left to right in the first flow channel, and a vertical laminar interface is formed between the first liquid and the second liquid. The bottom of the first flow channel has an acoustic device facing the laminar interface. The acoustic device is driven by a first power cycle, causing the acoustic device to periodically generate an acoustic beam along the laminar interface. The acoustic beam induces a portion of the second liquid to enter the first liquid and form droplets in the first liquid. The droplets are composed of the second liquid.

Images