Acoustically driven microdroplet ejection method and apparatus therefor

Abstract

The present application relates to the field of micro-droplet jet and inkjet technology, and particularly relates to an acoustic driving micro-droplet jetting method and device, which comprises: stably delivering a liquid to be jetted to a nozzle micro-hole assembly; generating an ultrasonic signal, which drives an ultrasonic transducer after power amplification; driving the resonant acoustic cavity nozzle through the ultrasonic transducer to form a stable sub-wavelength scale standing wave acoustic field in the cavity; using the acoustic radiation force to act on the liquid column at the end of the nozzle to realize the non-contact separation and directional jetting of the droplet; and moving the nozzle on the substrate through a multi-axis motion platform to realize the deposition of the droplet according to a predetermined track. The method and device avoid the nozzle blockage and other problems caused by the high viscosity or high solid content of the liquid in the traditional piezoelectric or electrohydrodynamic driving mode; can significantly improve the control accuracy of the droplet size and jetting speed, have excellent fluid adaptability and jetting stability, and are particularly suitable for the precise deposition and patterning jetting of complex fluids such as photoresist, metal paste and functional nanomaterials.

Description

An acoustically driven microdroplet ejection method and apparatus Technical Field

[0001] This invention relates to the field of micron-scale droplet jetting and inkjet technology, specifically to an acoustically driven microdroplet jetting method and apparatus. Background Technology

[0002] With the continuous development of advanced manufacturing technologies, microdroplet inkjet technology based on liquid microfluidics has shown broad application potential in many cutting-edge fields such as integrated circuit photoresist coating and development, power battery spraying, and perovskite solar cells. The development of advanced manufacturing processes places increasingly stringent requirements on droplet size, jet direction, deposition rate, and liquid adaptability. In practical applications, different processes often require the use of liquids with different viscosities, densities, and surface tension characteristics, such as polymer photoresists, biological protein solutions, or metal nanoparticle pastes. This places extremely high demands on the driving capability, flow field stability, and acoustic field coupling design of the jetting device.

[0003] Especially in the jetting of high-viscosity fluids, where the viscosity range is wide (from below 5 cP to over 4000 cP), traditional inkjet systems often face numerous challenges. Specifically, when handling high-viscosity fluids, traditional inkjet systems are prone to problems such as incomplete column breakage, poor droplet formation, and positional misalignment, which severely affect deposition accuracy and reliability. Existing inkjet technologies struggle to balance droplet formation stability, liquid adaptability, and jetting process controllability when dealing with complex high-viscosity fluids, making it difficult to meet the high requirements of advanced manufacturing processes for droplet size consistency and process reliability.

[0004] Traditional piezoelectric or electrofluidic actuation methods are prone to nozzle clogging in the jetting of high-viscosity or high-solids-content fluids due to the special properties of the liquids, affecting the continuity and stability of the jetting process. At the same time, these actuation methods have limited control precision over droplet size and jetting velocity, and cannot meet the stringent requirements for process stability and resolution in high-end micro-nano manufacturing fields.

[0005] Therefore, it is necessary to propose a new microdroplet jetting method and device, aiming to overcome the limitations of traditional piezoelectric or electro-hydraulic jetting methods, significantly improve the adaptability to fluids with different physical properties, reduce the risk of nozzle clogging, and improve the control precision of droplet size and jetting speed, thereby achieving dimensionally stable, concentrated, and highly adaptable droplet output to meet the key process requirements of advanced integrated circuit manufacturing and functional material deposition. Summary of the Invention

[0006] To address the aforementioned issues, this invention provides an acoustically driven microdroplet ejection method and apparatus. This method and apparatus employs a cavity resonance structure to establish a stable standing wave sound field within the cavity. Through acoustic radiation force enhancement and phase modulation, it achieves contactless, non-mechanical driven ejection of discrete droplets. Compared to traditional piezoelectric or electrofluidic drive methods, it significantly reduces the risk of nozzle clogging and significantly improves the system's adaptability to different types of liquids, making it particularly suitable for printing on materials with high viscosity, high solids content, or those sensitive to shear.

[0007] The technical solution of the present invention is as follows:

[0008] An acoustically driven microdroplet ejection device, comprising:

[0009] The liquid supply device is used to stably deliver the liquid to be sprayed to the micro-orifice assembly of the nozzle;

[0010] An ultrasonic signal excitation system, including a signal generator, a power amplifier, and an ultrasonic transducer, is used to generate high-frequency sound waves and drive a resonant acoustic cavity nozzle.

[0011] The resonant acoustic cavity nozzle, connected to the ultrasonic transducer, is used to form a stable standing wave acoustic field at the subwavelength scale within the cavity and drive the droplets to separate without contact through acoustic radiation force.

[0012] The nozzle micro-orifice assembly, coaxially arranged with the resonant acoustic cavity nozzle, includes a micro-orifice array structure. The nozzle micro-orifice assembly is located in the direction of acoustic radiation force to achieve directional droplet jetting.

[0013] A multi-axis motion platform is used to control the movement of the nozzle micro-orifice assembly in the XY plane to achieve the deposition of droplets on a predetermined trajectory on the substrate;

[0014] The monitoring and control system is connected to the ultrasonic signal excitation system and is used to control the parameters of the ultrasonic signal and monitor the status of the system.

[0015] The resonant cavity nozzle includes three geometric configurations: spherical resonant cavity nozzle, tangential cylindrical resonant cavity nozzle, and radial cylindrical resonant cavity nozzle.

[0016] The nozzle orifice diameter of the micro-orifice assembly ranges from 20 to 80 μm.

[0017] The multi-axis motion platform includes an X-axis guide rail, a Y-axis guide rail, and a stepper motor for driving. The resonant acoustic cavity nozzle is fixedly mounted on a Y-axis slider that is driven to slide by a stepper motor and cooperates with the Y-axis guide rail. The Y-axis guide rail is slidably mounted on the X-axis guide rail and is driven to slide by a stepper motor.

[0018] An acoustically driven microdroplet jetting method includes the following steps: stably delivering the liquid to be jetted to a nozzle micro-orifice assembly; generating an ultrasonic signal, which is then amplified to drive an ultrasonic transducer; driving a resonant acoustic cavity nozzle through the ultrasonic transducer to form a stable standing wave acoustic field at a subwavelength scale within the cavity; utilizing acoustic radiation force to act on the liquid column at the nozzle tip to achieve contactless separation and directional jetting of the droplets; and controlling the nozzle to move on a substrate through a multi-axis motion platform to achieve droplet deposition along a predetermined trajectory.

[0019] The intensity of acoustic radiation is enhanced by adjusting the geometric parameters of the resonant acoustic cavity nozzle to match the driving frequency.

[0020] The phase of the excitation signal is dynamically adjusted by phase modulation technology to precisely control the direction of droplet ejection.

[0021] The resonant cavity nozzle is selected from at least one of the following: spherical resonant cavity nozzle, tangential cylindrical resonant cavity nozzle, or radial cylindrical resonant cavity nozzle, to match different sound field distribution requirements and ensure uniform focusing of sound radiation force in the nozzle area.

[0022] By adjusting the frequency and amplitude of the ultrasonic signal to match the fluid properties.

[0023] The resonant state of the resonant cavity nozzle is monitored in real time by a monitoring and control system; based on the monitoring results, the driving frequency of the ultrasonic signal is dynamically adjusted to maintain the stable standing wave sound field at the subwavelength scale; the nozzle micro-orifice assembly is controlled to move along the X-axis and Y-axis guide rails to achieve precise deposition of droplets along a predetermined trajectory.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. The present invention discloses an acoustically driven microdroplet ejection method and apparatus. The acoustically driven microdroplet ejection method and apparatus adopts acoustic radiation force to drive non-contact droplet ejection, which significantly reduces the risk of nozzle clogging. By constructing a stable sound field inside the acoustic cavity and using acoustic modulation, the acoustic radiation force is controlled to directly act on the liquid column to form droplets, realizing non-contact separation and directional ejection of micron-sized droplets. Since the driving process does not rely on mechanical moving parts or microchannel pressure difference, high viscosity or high solid content particles are not easy to accumulate in the nozzle area, which is especially suitable for the precision deposition of complex fluids such as photoresist, silver paste, and nanoparticle dispersions.

[0026] 2. This invention discloses an acoustically driven microdroplet ejection method and apparatus. This method and apparatus achieve multi-dimensional control of droplet ejection direction, size, and velocity through resonance enhancement and phase modulation mechanisms of the acoustic cavity structure. Through acoustic field equivalent simulation and experimental verification, the acoustic cavity geometry (e.g., spherical, cylindrical) is matched with the driving frequency to form a subwavelength standing wave acoustic field, enhancing the acoustic radiation intensity at the jet outlet and ensuring uniform acoustic radiation force on each nozzle. Furthermore, precise control of the droplet period and direction is achieved by adjusting the excitation phase. This not only improves the dimensional consistency during droplet ejection but also significantly enhances the positioning accuracy of patterned deposition, meeting the stringent requirements of high-end micro / nano manufacturing for process stability and resolution.

[0027] 3. This invention discloses an acoustically driven microdroplet ejection method and apparatus, which has broad fluid applicability and can achieve stable ejection of various liquids such as high viscosity, non-Newtonian fluids, and shear-sensitive liquids. Traditional inkjet systems are prone to nozzle interference or unstable flow rates when handling high-viscosity or particulate fluids. The acoustically driven structure of this invention can adapt to different fluid properties by adjusting the ultrasonic frequency and amplitude, enabling the system to operate stably under special fluid conditions such as high viscosity (up to 4000 cP or more), high solids content, and easy aggregation, thereby expanding its application boundaries in multiple fields such as advanced packaging, flexible electronics, and micro / nano device printing. Attached Figure Description

[0028] The solutions and advantages of this application will become clear to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] In the attached diagram:

[0030] Figure 1 is a schematic diagram of the composition of an acoustically driven microdroplet ejection device according to an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the structure of a spherical resonant acoustic cavity nozzle of an acoustically driven microdroplet jetting device according to an embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of the structure of a tangential cylindrical resonant acoustic cavity nozzle of an acoustically driven microdroplet jetting device according to an embodiment of the present invention;

[0033] Figure 4 is a schematic diagram of the radial cylindrical resonant acoustic cavity nozzle of an acoustically driven microdroplet jetting device according to an embodiment of the present invention.

[0034] Figure 5 is a schematic diagram of the nozzle micro-orifice structure of the tangential cylindrical resonant acoustic cavity nozzle of an acoustically driven micro-droplet ejection device according to an embodiment of the present invention.

[0035] Figure 6 is a schematic diagram of the nozzle micro-orifice structure of the radial cylindrical resonant acoustic cavity nozzle of an acoustically driven micro-droplet ejection device according to an embodiment of the present invention.

[0036] Figures 7-9 are schematic diagrams of the three micropore channels of the nozzle micropore assembly of the cylindrical resonant acoustic cavity nozzle of an acoustically driven microdroplet jetting device according to an embodiment of the present invention.

[0037] Figure 10 is a distribution diagram of the acoustic intensity focused in the acoustic cavity at the resonant frequency of an acoustically driven microdroplet ejection device according to an embodiment of the present invention.

[0038] Figure 11 is a schematic diagram of the multi-axis motion platform structure of an acoustically driven microdroplet ejection device according to an embodiment of the present invention;

[0039] The components represented by the various reference numerals in the diagram are:

[0040] This invention comprises: 140, an ultrasonic transducer; 141, a tangential cylindrical ultrasonic transducer array; 142, a radial cylindrical ultrasonic transducer array; 150, a resonant acoustic cavity nozzle; 151, a spherical resonant acoustic cavity nozzle; 152, a tangential cylindrical resonant acoustic cavity nozzle; 153, a radial cylindrical resonant acoustic cavity nozzle; 160, a liquid supply channel; 170, a nozzle micropore assembly; 200, a signal generator; 210, a power amplifier; 220, a monitoring and control system; 310, a multi-axis motion platform; 311, an X-axis guide rail; 312, a Y-axis guide rail; 320, a substrate; and 410, a liquid supply device. Detailed Implementation

[0041] As shown in Figure 1, the acoustically driven microdroplet jetting device mainly includes the following parts: liquid supply device 410, ultrasonic signal excitation system, resonant acoustic cavity nozzle 150, nozzle micropore assembly 170 and multi-axis motion platform 310.

[0042] The liquid supply device 410 consists of a constant pressure liquid supply pump, which is used to continuously and stably fill the nozzle with the liquid to be sprayed (such as photoresist, metal paste, functional nanomaterials, etc.) to ensure uniform liquid supply during the spraying process.

[0043] The ultrasonic signal excitation system includes a signal generator 200, a power amplifier 210, and an ultrasonic transducer 140.

[0044] The signal generator 200 uses a function signal generator, which can generate arbitrary waveforms (such as sine waves, square waves, pulse waves, triangle waves, etc.), high-frequency, high-stability excitation signals with an adjustable frequency range.

[0045] The power amplifier 210 amplifies the drive signal generated by the signal generator 200 and uses it as a drive source to control the ultrasonic transducer 140 to generate high-frequency sound waves.

[0046] The ultrasonic transducer 140 is connected to the resonant cavity nozzle 150, converting the amplified electrical signal into mechanical vibration to generate kHz-MHz high-frequency sound waves. These waves are used to match the geometry of the resonant cavity nozzle 150 at the resonant frequency, forming a stable standing wave sound field. Depending on the cavity structure and jetting requirements, the ultrasonic transducer 140 can be configured in different forms, such as using a ring arrangement of piezoelectric sheets to excite radial vibration of the cylindrical cavity, or axial arrangement of piezoelectric sheets to achieve axial sound field focusing.

[0047] The resonant cavity nozzle 150 includes three typical forms: spherical resonant cavity nozzle 151, tangential cylindrical resonant cavity nozzle 152, and radial cylindrical resonant cavity nozzle 153. The three types of nozzle structures are suitable for the control requirements of different sound field distributions. The nozzle housing material is made of stainless steel, which has good pressure resistance and acoustic impedance matching characteristics.

[0048] The resonant acoustic cavity nozzle 150 and the ultrasonic transducer 140 are arranged coaxially, forming a closed resonant acoustic cavity inside. When ultrasonic waves encounter obstacles or non-uniform media (such as droplets, interfaces, etc.) during propagation, they generate a nonlinear average force, called acoustic radiation force. Based on the length of the ultrasonic wave, the shape of the resonant acoustic cavity nozzle 150 is designed to have a rigid reflective boundary, forming a standing wave cavity inside. Under the action of the resonant frequency, a standing wave is formed in the cavity, generating nodes and anti-nodes. There is an extremely high sound pressure at the anti-node, which can lead to a strong acoustic radiation force gradient. Through the change of the curvature structure of the resonant cavity, the sound energy is focused, forming a directional acoustic radiation force field. For high-viscosity fluids, their motion is greatly affected by resistance and requires higher sound pressure to overcome. When certain conditions are met, the liquid in the nozzle area forms a slender liquid column under the action of acoustic radiation force. Under the dominance of Rayleigh instability, the liquid column breaks to form discrete droplets, driving the liquid column to break and generate single or periodic micro-droplets. This process does not rely on mechanical pressure difference or thermal bubble drive, avoiding the problems of nozzle clogging and jet instability common in traditional inkjet systems.

[0049] The nozzle micro-orifice assembly 170 is coaxially arranged with the resonant acoustic cavity nozzle 150 and includes a micro-orifice array structure. The nozzle micro-orifice assembly 170 is located in the direction of acoustic radiation force. The orifice structure is arranged at the end of the nozzle and consists of multiple cylindrical micro-orifice arrays (it can also be designed as conical or other shapes according to actual needs). The orifice diameter ranges from 20 to 80 μm, and the orifice material is silicon. The micro-orifices are fabricated by laser processing.

[0050] The layout of the nozzle array is determined according to the acoustic cavity structure. For the spherical resonant acoustic cavity nozzle 151, the nozzles are arranged in concentric circles, that is, the nozzles are set along a circular ring of equal radius, and the center of the circle is aligned with the center of the acoustic cavity to ensure that the acoustic radiation force received by each nozzle is uniform. For the tangential cylindrical resonant acoustic cavity nozzle 152 and the radial cylindrical resonant acoustic cavity nozzle 153, the nozzles are arranged linearly, that is, the nozzles are set at equal intervals along the acoustic radiation direction to support the parallel jetting of the array and the linear printing path.

[0051] The multi-axis motion platform 310 consists of an X-axis guide rail 311, a Y-axis guide rail 312, a stepper motor, and a drive control system. The resonant acoustic cavity nozzle 150 is fixedly mounted on a Y-axis slider that is driven to slide by a stepper motor and cooperates with the Y-axis guide rail 312. The Y-axis guide rail 312 is slidably mounted on the X-axis guide rail 311 and is driven to slide by a stepper motor.

[0052] The nozzle position is precisely adjusted by the control software and monitoring system 220, which controls the movement of the nozzle micro-orifice assembly 170 in the XY plane to achieve droplet deposition on the substrate 320 along a predetermined trajectory. During the movement, the acoustic cavity resonance state is monitored in real time, and the driving frequency is dynamically adjusted using an impedance analyzer to maintain standing wave stability.

[0053] The monitoring and control system 220 is connected to the ultrasonic signal excitation system to control the parameters of the ultrasonic signal (such as frequency and amplitude), monitor the resonance state of the resonant cavity nozzle 150 in real time, and dynamically adjust the driving frequency of the ultrasonic signal based on the monitoring results to maintain a stable standing wave sound field at the subwavelength scale. At the same time, it controls the nozzle micro-orifice assembly 170 to move along the X-axis guide rail 311 and the Y-axis guide rail 312 to achieve precise deposition of droplets along a predetermined trajectory.

[0054] Based on the above device, the acoustically driven microdroplet ejection method includes the following steps:

[0055] Liquid supply: The liquid supply device 410 stably delivers the liquid to be sprayed to the nozzle micro-orifice assembly 170, ensuring that the liquid is evenly distributed inside the nozzle and preparing for subsequent droplet spraying.

[0056] Generating ultrasonic signals: The signal generator 200 generates an excitation signal with a specific frequency and amplitude, the frequency and amplitude of which can be adjusted according to the physical properties of the liquid to be sprayed (such as viscosity, density, surface tension, etc.).

[0057] Power amplification: The excitation signal is amplified by the power amplifier 210 and drives the ultrasonic transducer 140 to generate high-frequency sound waves.

[0058] Driving the resonant acoustic cavity nozzle: The ultrasonic transducer 140 transmits high-frequency sound waves to the resonant acoustic cavity nozzle 150, forming a stable standing wave sound field at the subwavelength scale inside the resonant acoustic cavity nozzle 150.

[0059] Non-contact separation and directional jetting of droplets: The liquid column at the tip of the nozzle is subjected to acoustic radiation force. When the acoustic radiation force reaches a certain level, the liquid column breaks into discrete droplets under the dominance of Rayleigh instability, thus achieving non-contact separation and directional jetting of droplets.

[0060] Droplet deposition: The nozzle is controlled to move on the substrate 320 by the multi-axis motion platform 310, and droplets are deposited on the surface of the substrate 320 according to a predetermined trajectory to meet the requirements of patterned printing or functional pattern preparation.

[0061] In the specific implementation process, the following operations can also be performed according to actual needs:

[0062] Adjusting the geometric parameters of the resonant acoustic cavity nozzle to match the driving frequency: By adjusting the geometric parameters (such as cavity size, shape, etc.) of the resonant acoustic cavity nozzle 150 to match the driving frequency, the intensity of acoustic radiation force is enhanced, and the droplet jetting effect is improved.

[0063] Phase control: By dynamically adjusting the phase of the excitation signal through phase control technology, the direction of droplet ejection can be precisely controlled to achieve multi-point synchronous ejection or ejection in a specific direction.

[0064] Select the appropriate type of resonant cavity nozzle: Based on different sound field distribution requirements, select at least one of the following: spherical resonant cavity nozzle 151, tangential cylindrical resonant cavity nozzle 152, or radial cylindrical resonant cavity nozzle 153, to ensure uniform focusing of sound radiation force in the nozzle area.

[0065] Adapting to fluid properties: By adjusting the frequency and amplitude of the ultrasonic signal to adapt to the properties of different fluids, the system can work stably under special fluid conditions such as high viscosity (up to 4000 cP or more), high solid content, and easy aggregation.

[0066] This acoustically driven microdroplet ejection device and method, through a cavity resonance enhancement structure and micropore array design, achieves stable ejection of high-viscosity, non-Newtonian, shear-sensitive liquids. It effectively reduces the risk of nozzle clogging and improves droplet size control accuracy and ejection direction consistency. In precision inkjet applications in high-end manufacturing fields such as advanced packaging, microelectronics manufacturing, flexible device printing, and photolithography pattern filling, it can meet the high requirements for droplet size consistency and process reliability, demonstrating promising application prospects.

[0067] Example

[0068] This acoustically driven, non-contact microdroplet jetting method and apparatus aim to improve adaptability to fluids with different properties and achieve precise control of the droplet jetting process. Specifically, based on a cavity standing wave enhancement structure design, a stable standing wave sound field at the subwavelength scale is established within the cavity. Various geometric configurations, such as spherical or cylindrical shapes, are used to concentrate the acoustic radiation force at the nozzle. Combined with phased-array excitation and a micro-hole array structure, the directional, synchronous, and stable jetting of micron-sized droplets is ensured under non-contact driving. Its core lies in the precise matching mechanism between the cavity geometry and the standing wave frequency, the dynamic control technology of the phased-array for droplet direction, and, in conjunction with a high-speed motion platform and a precision liquid supply system, enabling on-demand deposition of droplets on the target substrate surface. This method is suitable for high-precision manufacturing of complex materials such as high-viscosity liquids, non-Newtonian fluids, and nano-slurries. The innovative high-viscosity fluid jetting method proposed in this invention breaks through the limitations of traditional piezoelectric or electrohydrodynamic driving technologies and further solves common problems in the jetting of high-viscosity fluids (such as photoresist and metal nanoparticle paste) in fields such as semiconductor manufacturing and micro / nano functional material printing, including problems such as uneven droplet size, nozzle clogging and uncontrolled jetting direction.

[0069] As shown in Figure 1, the microdroplet jetting device includes: an ultrasonic signal excitation system, a resonant acoustic cavity nozzle 150, a nozzle micropore assembly 170, a multi-axis motion platform 310, a liquid supply device 410, and a monitoring and control system 220.

[0070] The ultrasonic signal excitation system consists of a function signal generator 200, a power amplifier 210, and an ultrasonic transducer 140. The function signal generator 200 can generate excitation signals of arbitrary waveforms, high frequency, and high stability, such as sine waves, square waves, pulse waves, and triangular waves. After being amplified by the power amplifier 210, the signal drives the ultrasonic transducer 140 to generate kHz-MHz high-frequency sound waves, which are used to match the geometry of the resonant cavity nozzle 150 at the resonant frequency, forming a stable standing wave sound field.

[0071] The resonant cavity nozzle 150 and the ultrasonic transducer 140 are arranged coaxially, forming a closed resonant cavity inside. When ultrasonic waves encounter obstacles or non-uniform media (such as droplets, interfaces, etc.) during propagation, a nonlinear average force is generated, called acoustic radiation force. Therefore, based on the ultrasonic wave length, the shape of the resonant cavity nozzle 150 is designed to have a rigid reflective boundary, forming a standing wave cavity inside. At this time, under the action of the resonant frequency, a standing wave is formed in the cavity, generating nodal and anti-nodal points. Extremely high sound pressure exists at the anti-nodal point, which can lead to a strong acoustic radiation force gradient. And through the change of the curvature structure of the resonant cavity, the sound energy is focused, forming a directional acoustic radiation force field.

[0072]

[0073] Where p1: first-order sound pressure disturbance; v1: first-order sound velocity disturbance; ρ0: static density of the liquid; <>: time average; for high-viscosity fluids, their motion is greatly affected by resistance, requiring higher sound pressure to overcome:

[0074]

[0075] Where μ represents the dynamic viscosity. When F > F visic During this process, the liquid in the nozzle area forms a slender column under the influence of acoustic radiation. Under the dominance of Rayleigh instability, the liquid column breaks into discrete droplets, driving the liquid column to rupture and generate single or periodic microdroplets. This process does not rely on mechanical pressure difference or thermal bubble drive, avoiding problems such as nozzle clogging and jet instability common in traditional inkjet systems.

[0076] As shown in Figures 2, 3, and 4, the nozzle assembly 150 can be divided into three typical forms: a spherical resonant nozzle 151, a tangential cylindrical resonant nozzle 152, and a radial cylindrical resonant nozzle 153. These three nozzle structures are suitable for controlling sound field distributions of different shapes. The nozzle housing material can be stainless steel, glass, or engineering plastic, with its pressure resistance and acoustic impedance matching characteristics determined according to actual process requirements.

[0077] As shown in Figures 3 and 4, the ultrasonic transducer 150 can be configured in different forms according to the differences in acoustic cavity structure and jet requirements. For example, the cylindrical cavity is excited by radial vibration through the ring arrangement of piezoelectric sheets; the axial arrangement of piezoelectric sheets is used to achieve axial sound field focusing.

[0078]

[0079] P focal denoted as focal sound pressure level; G as geometric gain; f as focal length; and D as nozzle diameter.

[0080] As shown in Figures 5 and 6, the nozzle array layout includes concentric circle arrangement (corresponding to a spherical cavity) and linear arrangement (corresponding to a cylindrical cavity). The position and spacing of the nozzle array are optimized according to the sound field focusing pattern. In the concentric circle arrangement, the nozzles are arranged along circular rings of equal radius, with the center of the ring aligned with the center of the acoustic cavity, ensuring that the sound radiation force received by each nozzle is uniform. In the linear arrangement, the nozzles are evenly spaced along the sound radiation direction to support parallel jetting and a linear printing path.

[0081] As shown in Figures 7 to 9, the nozzle structure 170 is arranged at the end of the nozzle and consists of an array of multiple cylindrical or conical micro-holes. The shape of the nozzle can be designed according to the liquid properties and the size of the target droplet, with a diameter range of 20-80 μm. The nozzle materials include silicon, stainless steel, glass, etc., and the micro-holes are made by laser processing, etching, or CNC precision machining.

[0082] As shown in Figure 10, the acoustic cavity resonant structure can achieve a subwavelength standing wave enhancement effect by adjusting the cavity geometry to match the excitation frequency. In the resonant state, the sound field energy density is focused in the nozzle region, and the acoustic radiation force reaches its maximum value, ensuring stable jet formation conditions. Using finite element software such as ANSYS and COMSOL to simulate and analyze different acoustic cavity geometries and material parameters, the optimal resonant frequency matching range can be obtained to enhance the jet driving force.

[0083] As shown in Figure 11, the multi-axis motion platform 310 consists of an X-axis guide rail 311, a Y-axis guide rail 312, a stepper motor, and a drive control system. Precise adjustment of the nozzle position is achieved through control software and a monitoring system 220. During motion, the acoustic cavity resonance state is monitored in real time, and the drive frequency is dynamically adjusted using an impedance analyzer to maintain standing wave stability.

[0084] The microdroplet jetting method and apparatus provided by this invention achieve stable jetting of high-viscosity, non-Newtonian, shear-sensitive liquids through acoustic cavity resonance enhancement structure and micropore array design; effectively reducing the risk of nozzle clogging and improving droplet size control accuracy and jetting direction consistency; it is particularly suitable for precision inkjet scenarios in high-end manufacturing fields such as advanced packaging, microelectronics manufacturing, flexible device printing, and photolithography pattern filling.

Claims

1. An acoustically driven microdroplet ejection device, characterized in that, include: A liquid supply device (410) is used to stably supply the liquid to be sprayed to the nozzle micro-orifice assembly (170); an ultrasonic signal excitation system, including a signal generator (200), a power amplifier (210), and an ultrasonic transducer (140), is used to generate high-frequency sound waves and drive the resonant acoustic cavity nozzle (150); the resonant acoustic cavity nozzle (150) is connected to the ultrasonic transducer (140) to form a stable standing wave sound field at a subwavelength scale in the cavity and drive the droplets to separate without contact through acoustic radiation force; the nozzle micro-orifice assembly (170) is connected to the resonant acoustic cavity nozzle (140) to generate high-frequency sound waves and drive the droplets to separate without contact through acoustic radiation force; 50) Coaxial arrangement, including micropore array structure, nozzle micropore assembly (170) is located in the direction of acoustic radiation force formed by resonant acoustic cavity nozzle (150), used to make the acoustic radiation force act on the liquid column at its end, to realize non-contact separation and directional spraying of droplets; multi-axis motion platform (310) is used to control the movement of nozzle micropore assembly (170) in XY plane to realize the deposition of droplets on the substrate (320) along a predetermined trajectory; monitoring and control system (220) is connected to ultrasonic signal excitation system to control the parameters of ultrasonic signal and monitor system status.

2. The acoustically driven microdroplet ejection device according to claim 1, characterized in that, The resonant cavity nozzle (150) includes three geometric configurations: a spherical resonant cavity nozzle (151), a tangential cylindrical resonant cavity nozzle (152), and a radial cylindrical resonant cavity nozzle (153).

3. The acoustically driven microdroplet ejection device according to claim 1, characterized in that, The nozzle micro-orifice assembly (170) has an orifice diameter ranging from 20 to 80 μm.

4. The acoustically driven microdroplet ejection device according to claim 1, characterized in that, The multi-axis motion platform (310) includes an X-axis guide rail (311), a Y-axis guide rail (312), and a stepper motor for driving. The resonant acoustic cavity nozzle (150) is fixedly mounted on a Y-axis slider that is driven to slide by a stepper motor and cooperates with the Y-axis guide rail (312). The Y-axis guide rail (312) is slidably mounted on the X-axis guide rail (311) and driven to slide by a stepper motor.

5. An acoustically driven microdroplet ejection method, based on an acoustically driven microdroplet ejection device according to any one of claims 1-4, characterized in that, Includes the following steps: The liquid to be sprayed is stably delivered to the nozzle micro-orifice assembly (170); an ultrasonic signal is generated and driven by the ultrasonic transducer (140) after power amplification; the ultrasonic transducer (140) drives the resonant acoustic cavity nozzle (150) to form a stable standing wave acoustic field of subwavelength scale in the cavity; the acoustic radiation force generated by the stable standing wave acoustic field is used to act on the liquid column at the end of the nozzle micro-orifice assembly to realize non-contact separation and directional spraying of the droplets; the nozzle is controlled to move on the substrate (320) by the multi-axis motion platform (310) to realize the deposition of droplets along a predetermined trajectory.

6. The acoustically driven microdroplet ejection method according to claim 5, characterized in that, The intensity of acoustic radiation is enhanced by adjusting the geometric parameters of the resonant cavity nozzle (150) to match the driving frequency.

7. The acoustically driven microdroplet ejection method according to claim 5, characterized in that, The phase of the excitation signal is dynamically adjusted by phase modulation technology to precisely control the direction of droplet ejection.

8. The acoustically driven microdroplet ejection method according to claim 5, characterized in that, The resonant cavity nozzle (150) is selected from at least one of a spherical resonant cavity nozzle (151), a tangential cylindrical resonant cavity nozzle (152), or a radial cylindrical resonant cavity nozzle (153) to match different sound field distribution requirements and ensure uniform focusing of sound radiation force in the nozzle area.

9. The acoustically driven microdroplet ejection method according to claim 5, characterized in that, By adjusting the frequency and amplitude of the ultrasonic signal to match the fluid properties.

10. The acoustically driven microdroplet ejection method according to claim 5, characterized in that, The resonant state of the resonant cavity nozzle (150) is monitored in real time by the monitoring and control system (220); based on the monitoring results, the driving frequency of the ultrasonic signal is dynamically adjusted to maintain the stable standing wave sound field at the subwavelength scale; the nozzle micro-orifice assembly (170) is controlled to move along the X-axis guide rail (311) and the Y-axis guide rail (312) to achieve precise deposition of droplets along a predetermined trajectory.

Images