A surface acoustic wave microfluidic acoustic tweezers device and method

Abstract

The application discloses a surface acoustic wave microfluidic acoustic tweezers device and method, and belongs to the technical field of microfluidics. Mainly includes: surface acoustic wave excitation module, application function module, impedance matching module, coupling agent. The surface acoustic wave excitation module is composed of an interdigital transducer and a piezoelectric wafer, and the application function module is composed of a separate working substrate or a working substrate with a microfluidic channel. The surface acoustic wave excitation module excites surface acoustic waves on the piezoelectric wafer, and excites Lamb waves in the application function module through the coupling agent, thereby realizing the arrangement, manipulation, sorting or mixing, centrifugation and other operations of microparticles or cells. In view of the problems that the existing surface acoustic wave microfluidic acoustic tweezers needs complex setting and is difficult to be reused, the device can use different module combinations according to different microfluidic application requirements, realize efficient excitation of surface acoustic waves in any direction in the microfluidic working area, and realize multifunctional and modular microfluidic acoustic tweezers application.

Description

Technical Field

[0001] This application relates to the field of microfluidics, and more specifically, to a surface acoustic wave microfluidic acoustic tweezers device and method. Background Technology

[0002] With the rapid development of fields such as biology and chemical analysis, microfluidics has become a cutting-edge research area both domestically and internationally. Microfluidics can precisely manipulate trace fluids, enabling rapid sample analysis and processing, and has broad application prospects in fields such as biomedicine, drug screening, and environmental monitoring.

[0003] Ultrasonic microfluidics is an important branch of microfluidics, combining ultrasonics and microfluidics to manipulate particles or cells in microfluidics in a non-contact, label-free, and biocompatible manner using ultrasound. Ultrasonic microfluidic devices can be classified into two types based on the type of acoustic excitation: bulk acoustic wave (SAW) microfluidic devices and surface acoustic wave (SAW) microfluidic devices. Among these, SAW microfluidic devices have attracted widespread attention from researchers due to their advantages, such as not relying on the resonance conditions of the cavity walls, achieving precise phase control, and the flexibility in setting up the ultrasonic transducer.

[0004] However, existing surface acoustic wave (SAW) microfluidic devices still have some limitations. In existing devices, the working area and interdigital transducers are usually fabricated on the same piezoelectric wafer, making the wafer non-reusable. For different applications, the wafer needs to be replaced and the device reconfigured and fabricated, a cumbersome and costly process. Furthermore, due to the generally acoustic anisotropy of piezoelectric crystal materials, SAW excited by interdigital transducers only exhibits high electromechanical coupling coefficients and acoustic propagation performance in specific directions. When SAW needs to be excited in multiple directions, even with additional complex setups, it is difficult to achieve consistency in acoustic excitation / propagation performance across all directions. Simultaneously, the optical birefringence of piezoelectric crystals can cause ghosting during microscopic observation of the working area, limiting the application of high-resolution observation methods. Some piezoelectric crystals have poor transmission capabilities for specific wavelengths of light; for example, lithium niobate crystals have limited transmission capabilities for ultraviolet light, making it difficult to integrate these devices with optical observation methods. In addition, existing SAW microfluidic devices are difficult to integrate with existing microfluidic products on the market, limiting their application scope.

[0005] Although some detachable microfluidic cavity devices have emerged in recent years, which separate the microfluidic cavity from the transducer wafer, they have not fundamentally changed the limitations of the transducer wafer, such as the aforementioned anisotropy and optical birefringence problems. This is significantly different from the modular surface acoustic wave microfluidic acoustic tweezers device and method proposed in this application. Summary of the Invention

[0006] 1. Technical problems to be solved

[0007] To address the problem of optical birefringence in existing surface acoustic wave (SAW) microfluidic technology, this application provides a SAW microfluidic acoustic tweezers device and method. By separating the piezoelectric wafer from the working area and assembling it in modules, the device achieves efficient excitation and propagation of SAW waves in different directions, avoids the effects of birefringence during optical observation, and enables the reusability of each module.

[0008] 2. Technical Solution

[0009] The purpose of this application is achieved through the following technical solution.

[0010] One aspect of this specification provides a surface acoustic wave (SAW) microfluidic acoustic tweezers device. By separating and configuring the various functional modules, modular assembly and flexible configuration of the device are achieved. The SAW excitation module includes an interdigital transducer and a piezoelectric crystal. It is used to excite Rayleigh SAW waves on the piezoelectric crystal and to excite Lamb waves in the application functional module via a coupling agent. This allows for efficient excitation of SAW waves in any direction, overcoming the limitations of the acoustic anisotropy of piezoelectric crystal materials. The application functional module carries the particles or cells to be manipulated and performs functions such as arrangement, manipulation, and sorting of particles or cells under ultrasonic action. This module is made of an isotropic transparent material with good optical transmission properties, improving compatibility with optical microscopy systems. The coupling agent effectively couples the SAW waves from the SAW excitation module to the application functional module, ensuring efficient acoustic energy transmission. The bus control circuit connects the SAW excitation module and the impedance matching circuit module, enabling signal transmission and control between the modules. The impedance matching circuit module matches the impedance of the SAW excitation module and the external drive circuit, reducing signal reflection loss and improving the excitation efficiency of the SAW waves. Device master plate: Used to fix and integrate the surface acoustic wave excitation module, application function module, bus control circuit, and impedance matching circuit module to form a complete surface acoustic wave microfluidic acoustic tweezers device. Microscope stage adapter: Used to fix the device master plate to the microscope stage, realizing the integration of the surface acoustic wave microfluidic acoustic tweezers device with an optical microscope, facilitating real-time observation and analysis of particles or cells.

[0011] The surface acoustic wave (SAW) excitation module is one of the core components of the modular SAW microfluidic acoustic tweezers device of this application. It mainly consists of two parts: an interdigital transducer and a piezoelectric wafer. The piezoelectric wafer material can be selected from piezoelectric single crystals, piezoelectric ceramics, or piezoelectric thin films, depending on the specific application requirements and performance indicators. For example, piezoelectric single crystal materials such as lithium niobate and lithium tantalate have excellent electrical coupling coefficients and electromechanical properties, making them suitable for high-frequency, high-efficiency SAW excitation; piezoelectric ceramic materials such as PZT have good electromechanical properties and fabrication processability, making them suitable for large-area, low-cost SAW devices; piezoelectric thin film materials such as ZnO and AlN can be fabricated using semiconductor processes, have a wide application frequency range, and are suitable for miniaturized and integrated SAW devices.

[0012] Interdigital transducers are fabricated on piezoelectric wafers using standard micromachining techniques, and their principles and setup methods are common knowledge in the field. Interdigital transducers convert high-frequency electrical signals into surface acoustic waves (SAWs) through the piezoelectric effect, and their performance has a decisive impact on the excitation efficiency and quality of SAWs. This application specifies particular requirements for the layout of the interdigital transducers: two busbars are distributed on both sides of the piezoelectric wafer, and their area is as large as possible. This layout facilitates effective connection between the interdigital transducers and the bus control circuit, reduces interconnect resistance and parasitic effects, and improves signal transmission efficiency and integrity.

[0013] The application function module is another key component of the modular surface acoustic wave (SAW) microfluidic acoustic tweezers device of this application. It is mainly used to hold the microparticles or cells to be manipulated and to realize various microfluidic functions under the action of SAW. According to different application requirements and operating modes, this application function module is divided into two main categories: microfluidic droplet type and microfluidic cavity type.

[0014] The microfluidic droplet application module consists of a separate working substrate, which can be made of quartz glass or other isotropic, optically transparent solid materials. This material selection offers excellent optical transmission properties, improving the resolution and precision of microscopic observation. In use, a carrier liquid containing microparticles or cells is directly dropped onto a specific location on the working substrate, forming a microfluidic droplet. Then, surface acoustic waves are used to mix the microparticles or cells within the droplet, followed by centrifugation and other operations. This open operating mode is suitable for rapid and flexible sample processing and analysis, such as cell lysis, nucleic acid extraction, and protein crystallization.

[0015] The microfluidic cavity type application module consists of a microfluidic cavity and a working substrate. The microfluidic cavity can be made of polydimethylsiloxane (PDMS), quartz glass, or other polymeric materials, fabricated using well-known microfabrication processes such as soft lithography, wet etching, and laser ablation, and then fixed to the working substrate by bonding or adhesive. In use, a carrier fluid containing microparticles or cells is injected into the microfluidic cavity, forming a microfluidic stream within the cavity. Surface acoustic waves are then used to arrange, manipulate, and sort the microparticles or cells within the microfluidic stream. This closed-loop operating mode is suitable for complex and precise sample processing and analysis, such as cell separation, drug screening, and biochemical reactions.

[0016] The couplant is a crucial medium connecting the surface acoustic wave (SAW) excitation module and the application functional module. Its main function is to ensure efficient transmission of SAW waves from the piezoelectric wafer to the working substrate, and to excite the desired Lamb wave in the working substrate. This application uses liquid or gel-based materials as couplants, such as water, silicone oil, machine oil, and petrolatum. These materials possess excellent acoustic properties and fluidity, enabling the formation of a uniform and tight acoustic coupling layer between the SAW excitation module and the application functional module. During use, the couplant is applied to the contact surfaces of the two modules, ensuring full contact and eliminating air bubbles, thereby minimizing acoustic energy loss and reflection.

[0017] To further improve acoustic coupling efficiency and stability, this application employs a magnetic clamping method to tightly attach the surface acoustic wave (SAW) excitation module to the application function module. Specifically, a magnet is embedded within the device motherboard, and another magnet is placed above the piezoelectric wafer. The attraction between the two magnets ensures close contact between the SAW excitation module and the application function module. Simultaneously, this clamping method also ensures a reliable and stable electrical connection between the busbar of the interdigital transducer and the spring pin array in the bus control circuit, thereby achieving efficient RF signal transmission and excitation.

[0018] In use, an interdigital transducer is excited by a radio frequency drive signal, causing it to generate Rayleigh surface acoustic waves on a piezoelectric wafer. The Rayleigh wave propagates along the surface of the piezoelectric wafer, and upon reaching the couplant layer, it enters the couplant at a specific Rayleigh angle and continues to propagate within it. Due to the good acoustic impedance matching between the couplant and the working substrate, the Rayleigh wave can efficiently penetrate the couplant layer and enter the working substrate, where it excites a Lamb wave. The Lamb wave is a guided wave mode that propagates in a plate-like structure, with its energy concentrated near the surface of the plate, making it suitable for microparticle or cell manipulation applications in microfluidic acoustic tweezers.

[0019] The bus control circuit is a crucial bridge connecting the surface acoustic wave excitation module and the impedance matching circuit module. Its main function is to achieve efficient transmission and distribution of radio frequency signals between different modules. The bus control circuit in this application is constructed using a printed circuit board (PCB) and surface-mount electronic components. The PCB is made of high-frequency board material, possessing excellent electrical performance and mechanical strength, effectively reducing high-frequency signal loss and crosstalk. The entire bus control circuit is secured to the underside of the device motherboard with screws, ensuring its positional stability and reliability.

[0020] In terms of signal transmission, this application employs two different connection methods, connecting the bus control circuit to the surface acoustic wave (SAW) excitation module and the impedance matching circuit module respectively. For the SAW excitation module, a spring-loaded pin array is used to connect the signal lines on the PCB to the busbars of the interdigital transducers. A spring-loaded pin array is a commonly used high-frequency interconnect device, containing multiple elastic metal pins that create a reliable and stable pressure contact between the PCB and the busbars. This connection method offers advantages such as easy insertion and removal, and good reusability, making it particularly suitable for frequent assembly and disassembly in modular setups. For the impedance matching circuit module, magnetic spring-loaded pin elements are used to connect the signal lines on the PCB. These magnetic spring-loaded pin elements introduce magnetic attraction, using the attraction of a magnet to ensure tight contact between the pins and the contacts on the module, further improving the reliability and stability of the connection. Simultaneously, this magnetic design makes module insertion and removal more convenient and flexible, reducing the difficulty of interconnection operations.

[0021] The modular and detachable design of the bus control circuit makes it very convenient to connect with the surface acoustic wave (SAW) excitation module and impedance matching circuit module, enabling rapid system assembly and debugging. In practical use, simply align the busbar of the SAW excitation module with the spring pin array and press it down, then attach the impedance matching circuit module to the magnetic spring pin element to establish a stable and reliable electrical connection, achieving lossless transmission of RF signals. When it is necessary to replace or maintain a module, simply pull out the corresponding pin connection; there is no need to disassemble the entire system, greatly improving the maintainability and flexibility of the system.

[0022] Impedance matching circuit module is a key component for optimizing the electrical performance of acoustic tweezers device. Its main function is to perform impedance matching between surface acoustic wave excitation module, bus control circuit and external drive circuit, so as to minimize the reflection loss of radio frequency signal and improve the electrical efficiency of system.

[0023] Similar to the bus control circuit, the impedance matching circuit module also utilizes a printed circuit board (PCB) and surface-mount electronic components. The PCB provides excellent high-frequency electrical performance and mechanical support, while the surface-mount electronic components implement the specific construction of the impedance matching network. For connectivity, the impedance matching circuit module uses magnetic spring-loaded pins to connect to the lines on the bus control circuit, leveraging magnetic attraction to ensure reliable and stable connections. Simultaneously, the impedance matching circuit module also includes standard RF signal interface components (such as SMA, BNC, etc.) for direct connection to external drive circuits, enabling low-loss transmission of RF signals.

[0024] The specific implementation process of impedance matching is as follows: First, after selecting the surface acoustic wave (SAW) excitation module, a professional impedance analyzer is used to accurately measure the overall electrical impedance of the SAW excitation module and the bus control circuit. Then, based on the measurement results, theoretical analysis is performed on the Smith chart. According to the basic principles and common methods of impedance matching, the optimal impedance matching scheme is determined, and suitable passive components such as capacitors and inductors are selected and soldered onto the PCB of the impedance matching circuit module in series or parallel to construct a complete matching network. The goal of setting up the matching network is to make the overall input impedance of the SAW excitation module and the bus control circuit essentially the same as the output impedance of the external drive circuit (usually 50 ohms), thereby minimizing the reflection loss of the RF signal during transmission and ensuring efficient power transfer.

[0025] In actual operation, the external drive circuit (typically composed of a cascaded RF signal generator and power amplifier) ​​is directly connected to the impedance matching circuit module via a standard RF signal interface component. Due to impedance matching, the RF signal can be transmitted efficiently and losslessly between the two modules, reducing signal reflection and power loss caused by impedance mismatch, and significantly improving the system's electrical efficiency and stability. Furthermore, thanks to its modular design and magnetic connection, the impedance matching circuit module can be easily assembled and disassembled with the bus control circuit and external drive circuit, greatly enhancing the system's flexibility and maintainability.

[0026] The device motherboard serves as the foundation and support for the entire modular surface acoustic wave (SAW) microfluidic acoustic tweezers device. Its main function is to integrate and fix the various functional modules in a predetermined position and sequence, ensuring the mechanical stability and reliability of the system. The device motherboard of this application can be made of resin, metal, or other suitable solid materials, possessing sufficient strength and rigidity to provide robust support and protection for other modules. Below the device motherboard, the bus control circuit and the microscope stage adapter are respectively installed using screws. The bus control circuit is responsible for the transmission and distribution of radio frequency signals, while the microscope stage adapter is used to fix the entire acoustic tweezers device onto the microscope stage, enabling docking with the optical observation system.

[0027] In the central area of ​​the device motherboard, there are dedicated mounting positions and limiting structures for placing and securing application function modules. These modules can be microfluidic droplet or microfluidic channel types, used to hold the microparticles or cells to be manipulated. To ensure the positional accuracy and repeatability of the application function modules, the device motherboard has precision limiting grooves at its four corners. These grooves accurately position and secure the application function modules, preventing them from shifting or falling off during use.

[0028] Multiple mounting positions and limiting structures are provided around the device motherboard for placing and fixing the surface acoustic wave (SAW) excitation module. The SAW excitation module is the core component of the acoustic tweezers device, responsible for exciting SAW waves. To ensure precise alignment and tight coupling between the SAW excitation module and the application function module and bus control circuit, precision limiting grooves are provided on both sides of each SAW excitation module on the device motherboard. These limiting grooves can accurately position and fix the SAW excitation module, enabling it to form a stable and reliable acoustic coupling with the application function module.

[0029] In addition, several positioning magnets are embedded inside the device's motherboard. These magnets work in conjunction with the magnets above the surface acoustic wave (SAW) excitation module, using magnetic attraction to tightly press the SAW excitation module and the application function module together. This ensures that SAW waves can be transmitted efficiently and without damage to the application function module, enabling precise manipulation of particles or cells.

[0030] The microscope stage adapter is a key component for integrating the acoustic tweezers device with the optical microscope system. Its main function is to stably and reliably fix the acoustic tweezers device onto the microscope stage, facilitating real-time observation and analysis of the working area of ​​the acoustic tweezers device under the microscope. The microscope stage adapter of this application can be made of resin, metal, or other suitable solid materials, possessing sufficient strength and rigidity to provide robust support and protection for the acoustic tweezers device. During assembly, the microscope stage adapter is fixed to the bottom of the bus control circuit using screws, forming a complete and stable integrated device. This configuration not only ensures a reliable connection between the microscope stage adapter and other components of the acoustic tweezers device but also guarantees the mechanical stability of the entire system.

[0031] Considering the differences in size, shape, and fixing methods among different models and brands of microscope stages, the microscope stage adapter of this application adopts a modular and customizable design. The specific shape and size of the adapter can be customized and optimized according to the specifications of the microscope stage used, ensuring precise and stable docking with the microscope stage. This flexible and customizable design allows the acoustic tweezers device to be adapted to most common microscope stages on the market, greatly expanding its application range and compatibility.

[0032] Another aspect of the embodiments of this specification provides a surface acoustic wave (SAW) microfluidic acoustic tweezers method. The modular SAW microfluidic acoustic tweezers device of this application provides various application function modules, which can be selected and combined according to different target needs to achieve diverse microfluidic operation and analysis functions. For microfluidic cavity-type devices, their main applications include the arrangement, manipulation, and sorting of particles or cells. By setting and fabricating microfluidic channels of specific shapes and sizes on a working substrate, and utilizing the acoustic radiation force generated by SAW within the microfluidic channels, precise control and manipulation of particles or cells can be achieved. For example, by adjusting the frequency, amplitude, and phase of the SAW, the capture, movement, and separation of particles or cells can be achieved, realizing high-throughput, high-precision micro / nano manipulation.

[0033] For microfluidic droplet devices, their main applications include droplet mixing and centrifugation. By forming surface acoustic waves on the surface of the working substrate and utilizing the acoustic flow and radiation forces induced by these waves, the fluid and particles inside the droplet can be controlled and manipulated. For example, strong acoustic flow and eddies can be generated inside the droplet to promote rapid mixing and homogenization between different droplets; and particles inside the droplet can be driven to migrate and accumulate in specific areas, achieving the separation and purification of the droplet contents.

[0034] The device motherboard, bus control circuit, and microscope stage adapter are assembled together with screws to form a complete and stable device base. The purpose of this step is to mechanically integrate the various basic components of the acoustic tweezers device, providing a platform support for the subsequent installation and use of functional modules.

[0035] Based on specific application requirements, select the appropriate application function module and place it in the limiting groove in the center of the device master plate. For microfluidic cavity type application function modules, it is necessary to set and fabricate the required cavity type, shape and size according to the experimental purpose and sample characteristics, and fix it on the working substrate by bonding or adhesive to form a complete microfluidic operation cavity.

[0036] Selecting and installing a surface acoustic wave (SAW) excitation module is the core step in achieving acoustic tweezers manipulation. Users can choose different types of SAW excitation modules, such as parallel interdigital transducers, focused interdigital transducers, and broadband interdigital transducers, based on specific application requirements and desired manipulation effects. These different types of interdigital transducers each have their own characteristics in terms of SAW excitation methods, beam shapes, and frequency characteristics, resulting in different sound field distributions and manipulation effects.

[0037] When using surface acoustic wave (SAW) excitation modules, the position and number of these modules must be rationally arranged according to the desired sound field type. For example, using a pair of identical SAW excitation modules on both sides of the application module can generate a standing wave sound field in a microfluidic channel or droplet. The characteristic of a standing wave sound field is the formation of periodic pressure nodes and antinodes in space, which can confine particles or cells to specific locations, achieving precise positioning and patterned arrangement. Conversely, using only one SAW excitation module on one side of the application module can generate a traveling wave sound field. The characteristic of a traveling wave sound field is that sound energy propagates along a specific direction, generating directional acoustic flow and acoustic radiation force, enabling the directional migration and transport of particles or cells.

[0038] To achieve effective coupling between the surface acoustic wave (SAW) excitation module and the application module, an appropriate coupling agent (such as water or silicone oil) needs to be applied to their contact area. The coupling agent effectively transmits the SAW waves from the piezoelectric substrate to the working substrate of the application module, reducing acoustic energy reflection and attenuation losses. After applying the coupling agent, the interdigital transducer of the SAW excitation module is placed face down in the corresponding limiting groove on the device motherboard, and then firmly pressed against the application module by the magnets on the motherboard, ensuring a stable and uniform acoustic coupling between the two.

[0039] During assembly, it is also necessary to ensure a reliable connection between the interdigital transducer busbar on the surface acoustic wave (SAW) excitation module and the bus control circuit. This can be achieved using a spring pin array pre-installed on the device motherboard. One end of the spring pin array is connected to the signal line of the bus control circuit, and the other end contacts the busbar of the interdigital transducer. When the SAW excitation module is pressed against the spring pin array, the pins undergo a certain elastic deformation, thus forming a stable and reliable electrical connection between the busbar and the signal line. This connection method has advantages such as strong adaptability, reliable contact, and ease of assembly and disassembly, effectively ensuring the efficient transmission of high-frequency electrical signals.

[0040] Impedance matching and external circuit connections are crucial for ensuring the efficient and stable operation of the acoustic tweezers device. The function of the impedance matching circuit is to provide a transition and conversion between two circuits with different impedances, enabling high-frequency signals to be transmitted with maximum power while reducing reflections and losses. When selecting and configuring the impedance matching circuit, it is necessary to first use a professional impedance analyzer or network analyzer to accurately measure the overall impedance of the surface acoustic wave excitation module and the bus control circuit. Based on the measurement results, and according to well-known RF impedance matching theories and methods in the field, the optimal impedance matching circuit topology and component parameters are selected or configured, and then fabricated into an independent impedance matching circuit module.

[0041] During assembly, the impedance matching circuit module is connected to the bus control circuit via magnetic spring pin elements mounted on the device motherboard. The working principle of the magnetic spring pin elements is similar to that of the aforementioned spring pin array, except that magnetic material is added to the base of the pins. When the contact area of ​​the impedance matching circuit module is aligned with the magnetic spring pin and pressed down, the pins deform elastically and are magnetically attracted to the contacts, forming a more stable and reliable electrical connection.

[0042] After completing the impedance matching of the internal circuitry, the impedance matching circuit module also needs to be connected to the external drive circuit (such as a signal generator, power amplifier, etc.). This can be achieved by integrating standard RF signal interface components (such as SMA, BNC, etc.) onto the impedance matching circuit module. Users only need to connect the output port of the external drive circuit to the RF interface on the impedance matching circuit module using a standard RF coaxial cable to establish a complete electrical connection, enabling precise and efficient transmission of high-frequency excitation signals from external instruments to the acoustic tweezers device.

[0043] By rationally configuring and using impedance matching circuit modules, and relying on magnetic spring pin components and standard RF interfaces to achieve reliable connection between internal and external circuits, the acoustic tweezers device of this application can minimize the transmission loss of high-frequency signals and improve the excitation efficiency and manipulation quality of surface acoustic waves. This modular and standardized connection method not only simplifies the assembly and debugging process, but also provides great flexibility for the performance optimization and functional expansion of the acoustic tweezers device, enabling it to adapt to different application requirements and working conditions.

[0044] Depending on the specific application objective, a carrier solution containing microparticles or cells should be selected and prepared. The properties and composition of the carrier solution directly affect the effectiveness and efficiency of acoustic tweezers manipulation. Therefore, the composition and concentration of the carrier solution must be rationally formulated based on the type, size, density, and other characteristics of the microparticles or cells to obtain optimal manipulation performance. When using microfluidic cavity-type application modules, a microfluidic pump is needed to inject the carrier solution into the pre-prepared microfluidic cavity through a dedicated microfluidic tube. When using microfluidic droplet-type application modules, a micropipette or other precision liquid transfer device is required to drop the carrier solution onto a specific location on the working substrate, controlling the size and shape of the droplet.

[0045] Based on actual application requirements, a suitable radio frequency (RF) excitation signal is set and generated through an external driving circuit or a self-designed driving circuit. The frequency, amplitude, and phase parameters of the RF excitation signal directly determine the excitation efficiency and sound field distribution of the surface acoustic wave (SAW), thus affecting the precision and flexibility of acoustic tweezers manipulation. When setting the RF excitation signal, it is necessary to fully consider the operating frequency, bandwidth, and power characteristics of the SAW excitation module, as well as the size, shape, and material of the microfluidic channels or droplets in the application functional module. Signal parameters should be optimized through theoretical calculations and numerical simulations to achieve the desired sound field mode and manipulation effect.

[0046] After the radio frequency (RF) excitation signal is generated, it is transmitted to the interdigital transducer of the surface acoustic wave (SAW) excitation module via an impedance matching circuit module. When the RF signal is applied to the interdigital transducer, the piezoelectric material in the transducer undergoes periodic mechanical deformation under the influence of the electric field, exciting SAW waves with frequencies and wavelengths matching the interdigital structure on the surface of the piezoelectric substrate. The SAW waves are efficiently transmitted to the working substrate of the application function module through a coupling agent layer, where Lamb waves are excited.

[0047] When a Lamb wave is incident on a liquid or droplet within a microfluidic cavity, it propagates into the microfluidic at a leakage angle, thereby forming a specific acoustic field distribution and acoustic radiation force distribution within the microfluidic. By rationally setting the layout of the surface acoustic wave excitation module and the parameters of the radio frequency excitation signal, target acoustic pressure nodes and acoustic flow can be generated in the liquid or droplet, thereby enabling flexible manipulation of particles or cells for capture, enrichment, sorting, and migration. For example, standing wave acoustic fields can be used to bind particles or cells to acoustic pressure nodes, forming regular arrays or patterns; tilted standing wave acoustic fields can be used to transport and sort particles or cells along specific directions; and acoustic flow can be used to enrich particles or cells into specific regions.

[0048] 3. Beneficial effects

[0049] Compared to existing technologies, the advantages of this application are:

[0050] (1) By making the surface acoustic wave excitation module, application function module, and impedance matching module detachable, the device is modularly assembled. In different application scenarios, only the corresponding application function module needs to be replaced, without having to reconfigure and manufacture the entire device. This avoids cross-contamination of samples in different applications, improves the reusability of the device, and reduces the cost of use.

[0051] (2) By adopting independent surface acoustic wave excitation modules, the working area is separated from the piezoelectric crystal. In the working area, convenient and efficient sound field control can be achieved in different directions. This overcomes the problem of inconsistent excitation performance in multiple directions caused by the acoustic anisotropy of piezoelectric crystal materials, so that each surface acoustic wave excitation module has a high excitation efficiency, making the application of multidimensional surface acoustic wave microfluidic technology more flexible.

[0052] (3) The application function module is made of optically isotropic material, which avoids the influence of the optical birefringence effect of piezoelectric crystal in traditional ultrasonic microfluidic devices on microscopic observation. Moreover, it has good ultraviolet light transmittance, which improves the compatibility of the device with high-resolution optical microscopy system.

[0053] (4) The introduction of the spring pin connection method of the bus control circuit makes the connection between the bus control circuit and the surface acoustic wave excitation module and the impedance matching module easier, the contact is reliable, and it is easy to disassemble and assemble, thus realizing the efficient connection and impedance matching between the surface acoustic wave excitation module and the external drive circuit.

[0054] (5) The device is easy to integrate and simple to assemble, avoiding the complex assembly process in the fabrication of traditional surface acoustic wave tweezers devices. The surface acoustic wave excitation module is easy to integrate into other microfluidic chips and can work in conjunction with existing microfluidic chips. Attached Figure Description

[0055] Figure 1This is a schematic diagram of the complete structure of the modular surface acoustic wave microfluidic acoustic tweezers of this application;

[0056] Figure 2 This is a schematic diagram of the layered structure of the modular surface acoustic wave microfluidic acoustic tweezers of this application;

[0057] Figure 3 This is a schematic diagram illustrating the working principle of the modular surface acoustic wave microfluidic acoustic tweezers of this application;

[0058] Figure 4 This is a schematic diagram illustrating the working principle of the microfluidic cavity type modular surface acoustic wave microfluidic acoustic tweezers in Embodiments 1 and 2 of this application;

[0059] Figure 5 This is a schematic diagram illustrating the working principle of the microfluidic droplet-type modular surface acoustic wave microfluidic acoustic tweezers in Embodiment 3 of this application.

[0060] The module includes: 1. Impedance matching circuit module; 2. Surface acoustic wave excitation module with interdigital transducer; 3. Application function module; 4. Device master plate; 5. Bus control circuit; 6. Microscope stage adapter; 7. Coupling agent; 8. Microfluidic cavity type application function module; 9. Microfluidic droplet type application function module. Detailed Implementation

[0061] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0062] Example 1

[0063] This embodiment describes a modular surface acoustic wave microfluidic acoustic tweezers device for arranging and manipulating microspheres with a diameter of 10 micrometers, employing a microfluidic cavity-type application functional module 8. The structure of the entire device is as follows: Figure 1 As shown, it mainly consists of a device motherboard 4, a bus control circuit 5, a microscope stage adapter 6, an application function module 3, and a surface acoustic wave excitation module.

[0064] In step one, the device motherboard 4, the bus control circuit 5, and the microscope stage adapter 6 are first assembled together using screws, such as... Figure 2 As shown in sections 4, 5, and 6, these three components constitute the basic support and electrical connection platform of the entire acoustic tweezers device. The device mother plate 4 is made of 3D-printed photocurable resin, possessing excellent mechanical strength and processing precision. A 24×24mm² four-corner limiting groove is provided in the central area of ​​the mother plate for precise placement and fixation of the application function module 3. Limiting grooves of 20×30mm² are also provided in the four directions of the mother plate for placement and fixation of the surface acoustic wave excitation module. In addition, slots are reserved on the mother plate for placing positioning magnets, for embedding and fixing neodymium iron boron permanent magnets, providing magnetic force to press the surface acoustic wave excitation module and the application function module 3.

[0065] The bus control circuit 5 is fabricated using an FR-4 type double-layer printed circuit board, which possesses excellent high-frequency electrical performance and mechanical strength. Two rows of 1×4 spring pin arrays are soldered onto the circuit board at the positions corresponding to the interdigital transducer busbars in the surface acoustic wave excitation module, ensuring reliable electrical connection with the interdigital transducer busbars. Simultaneously, two magnetic spring pin elements are soldered onto the circuit board at the corresponding positions of each impedance matching circuit module 1, providing both electrical connection and mechanical fixation. Internal wires on the circuit board connect each spring pin array to its corresponding magnetic spring pin element, forming a complete signal transmission path.

[0066] The microscope stage adapter 6 is also made of 3D-printed photocurable resin. Its size and shape are customized according to the model of the microscope stage to be used, so as to achieve precise docking and stable fixation of the acoustic tweezers device with the microscope system. The device motherboard 4, the bus control circuit 5, and the microscope stage adapter 6 all have four standard screw holes pre-drilled. During assembly, the three components are securely assembled together with screws to form a complete, mechanically stable acoustic tweezers device base, facilitating subsequent installation and debugging of functional modules.

[0067] In step two, based on actual application requirements, a suitable microfluidic cavity type application function module 8 is selected and placed in the limiting groove in the center of the device mother plate 4, such as... Figure 2 As shown in Part 3 of the document. The purpose of this step is to integrate a microfluidic chip with a specific function with an acoustic tweezers device to form a complete acoustic tweezers manipulation platform.

[0068] For applications involving the arrangement and manipulation of particles with a diameter of 10 micrometers, a quartz glass substrate with dimensions of 24×24×0.3mm is used. 3 Quartz glass possesses excellent optical transparency, mechanical strength, and surface smoothness. The dimensions of the working substrate are matched with the size of the central limiting groove in the device motherboard 4, ensuring precise positioning and fixation of the chip within the device.

[0069] A microfluidic cavity structure composed of polydimethylsiloxane (PDMS) was fabricated on a quartz glass substrate, with internal dimensions of 1800 × 1800 × 50 μm³. PDMS is a commonly used microfluidic chip material with excellent biocompatibility, transparency, and flexibility, and is easily fabricated into the desired microfluidic structure using methods such as soft photolithography. Inlet and outlet channels are provided on both sides of the cavity for introducing and discharging the microparticle suspension to be manipulated.

[0070] To fabricate PDMS microfluidic channels, a SU-8 photoresist mold with the desired channel structure is first created on a silicon wafer or other substrate using methods such as photolithography. SU-8 is a commonly used negative photoresist with advantages such as high aspect ratio and high resolution, making it particularly suitable for fabricating molds for microfluidic chips. Next, the PDMS prepolymer and curing agent are mixed in a specific ratio and poured into the SU-8 mold. After curing at a certain temperature, the PDMS structure is carefully peeled off the mold. Then, the PDMS structure is cut to the required size using a dicing tool or laser cutter, and holes are drilled at the inlet and outlet to insert microfluidic tubing.

[0071] To firmly bond PDMS microfluidic channels to a quartz glass substrate, a common method is to use a plasma cleaner to expose the PDMS and glass surfaces in oxygen or air plasma for tens of seconds, generating a large number of hydroxyl functional groups on the surface, thereby increasing surface energy and adhesion. Then, the treated PDMS and glass surfaces are rapidly bonded together and pressurized at a certain temperature for several hours to form a strong covalent bond.

[0072] Through the above steps, a quartz glass working substrate integrating PDMS microfluidic channels was prepared and precisely placed in the central limiting groove of the acoustic tweezers device mother plate 4. This modular, plug-and-play setup allows users to quickly replace and integrate various functional microfluidic chips according to different application needs, greatly improving the applicability and flexibility of the acoustic tweezers device. Simultaneously, the precise limiting and fixing mechanism ensures high-precision alignment and stable coupling between the chip and other components of the acoustic tweezers device, laying the foundation for subsequent high-efficiency, high-quality acoustic tweezers manipulation.

[0073] In step three, a suitable surface acoustic wave (SAW) excitation module is selected based on the specific requirements of particle arrangement and manipulation, and integrated into the acoustic tweezers device. The purpose of this step is to generate the required SAW and couple it into the microfluidic chip to achieve precise manipulation of the particles.

[0074] For applications involving the arrangement and manipulation of 10-micrometer particles, a parallel interdigital transducer with a fixed finger spacing and a characteristic wavelength of 300 micrometers was selected. The parallel interdigital transducer is one of the most commonly used surface acoustic wave (SAW) excitation devices. Its periodically arranged fingers, when an RF voltage is applied, can excite SAW waves on the piezoelectric substrate with wavelengths matching the finger period. The selection of the wavelength requires comprehensive consideration of factors such as the size of the manipulated particle, the attenuation characteristics of the SAW waves, and the size of the microchannel to obtain optimal manipulation performance.

[0075] The interdigital transducer is fabricated on a 128°YX lithium niobate wafer with a wafer size of 20×30×1mm. 3Lithium niobate is a commonly used piezoelectric material with excellent electromechanical coupling and low-loss characteristics, making it particularly suitable for fabricating high-frequency surface acoustic wave (SAW) devices. The 128° YX cutting method maximizes the voltage drive coefficient, improving transducer efficiency. The wafer size matches the dimensions of the four side-mounted limiting grooves on the device's motherboard, ensuring precise positioning and fixation of the SAW excitation module within the device.

[0076] Interdigital transducers were fabricated on the surface of a lithium niobate wafer using standard microelectronic fabrication processes. First, an interdigital pattern was transferred onto the wafer surface using photolithography. Then, thin films of metallic chromium and gold were deposited by ion beam sputtering to form the interdigital electrodes.

[0077] In this embodiment, four identical surface acoustic wave (SAW) excitation modules are arranged around the perimeter of the microfluidic chip. This layout creates a uniform standing wave acoustic field within the chip, which is beneficial for achieving two-dimensional arrangement and manipulation of particles. When integrating the SAW excitation modules, a layer of silicone oil is first applied to the contact area between the module and the chip using a micro-injector, serving as the acoustic coupling agent 7. Silicone oil possesses excellent acoustic impedance matching characteristics and chemical stability, effectively transmitting SAW waves from the piezoelectric substrate to the microfluidic chip while reducing interface reflection and energy loss.

[0078] Then, the four surface acoustic wave (SAW) excitation modules, with the interdigital transducers facing down, were carefully placed in the limiting slots on the four sides of the device mother plate 4, and magnets were placed on top of the modules. The magnets provided stable clamping force, ensuring close contact between the SAW excitation modules and the microfluidic chip in the coupling area through the silicone oil layer, guaranteeing good acoustic coupling. Simultaneously, the busbars of the interdigital transducers in the SAW excitation modules were reliably connected to the bus control circuit 5 via a spring pin array, such as... Figure 2 As shown in Part 2 of the diagram. The spring pin array provides a flexible and reliable electrical connection that is easy to assemble and disassemble, and can accommodate height differences and positional deviations between the module and the bus control circuit 5.

[0079] In step four, an impedance analyzer is used to measure and analyze the electrical impedances of the four surface acoustic wave excitation modules and the bus control circuit 5, and a suitable impedance matching circuit module 1 is set accordingly. The purpose of this step is to match the impedance of the entire acoustic tweezers device with the standard 50-ohm impedance of the RF system, reduce the transmission reflection loss of the RF signal, and improve the electrical efficiency and stability of the device.

[0080] Based on the measured impedance data, a suitable impedance matching network is set between each excitation module and the bus control circuit 5. The basic principle of impedance matching is to adjust the equivalent impedance of the circuit by introducing appropriate passive components (such as capacitors and inductors) to match the standard impedance value of 50 ohms, thereby achieving maximum power transmission and minimum reflection loss. These components are connected in series or parallel according to a specific topology and soldered onto the printed circuit board of the corresponding impedance matching circuit module 1 to form a complete impedance matching network. After conditioning by the matching network, the equivalent impedance of each excitation module and the bus control circuit 5 is adjusted to 50 ohms, matching the standard RF system impedance.

[0081] To facilitate the integration and connection of the impedance matching circuit module 1 and the bus control circuit 5, magnetic spring pin components that match the bus control circuit 5 are soldered onto the circuit board of each module. For example... Figure 2 As shown in Part 1, these pin components can be directly inserted into the corresponding magnetic contacts on the bus control circuit board 5, providing a reliable electrical and mechanical connection. Additionally, each impedance matching circuit module 1 integrates an SMA standard RF interface for connection to external RF drive circuits.

[0082] The external RF drive circuit consists of a signal generator and a power amplifier. The signal generator generates RF control signals with the required frequency and waveform, while the power amplifier amplifies the control signals to a sufficiently high power level to drive the surface acoustic wave excitation module. The RF drive circuit is connected to the impedance matching circuit module 1 via a standard SMA coaxial cable.

[0083] In step five, a carrier liquid containing the microparticles to be manipulated is prepared according to the actual application requirements. In this example, 10-micrometer-diameter polystyrene microparticles are used, which are uniformly dispersed in a suitable liquid medium to form a stable microparticle suspension. To optimize the acoustic tweezers manipulation effect, the surface of the microfluidic channel needs to be treated to improve its hydrophilicity and reduce its adhesion to the microparticles. The surface of the channel is chemically modified using a hydrophilic reagent, and a layer of biomolecules such as bovine serum albumin is deposited on the surface through physical adsorption. After preparing the microparticle suspension, an external syringe pump is used to slowly inject it into the microfluidic channel through the microfluidic tube, ensuring that the microparticles are uniformly distributed within the microfluidic channel for subsequent effective manipulation and positioning.

[0084] In step six, a suitable radio frequency (RF) excitation signal is selected for acoustic tweezer manipulation based on the settings parameters of the surface acoustic wave (SAW) excitation module and the microfluidic cavity. This example uses a 13.2 MHz sinusoidal continuous wave signal, which matches the center frequency of the SAW excitation module, enabling efficient and stable SAW generation. Four independent RF excitation signals are generated by an external RF drive circuit (including a signal generator and power amplifier) ​​and applied to the interdigital transducers of the four SAW excitation modules via impedance matching circuit module 1 and bus control circuit 5.

[0085] When an radio frequency electrical signal is applied to the interdigital transducer, the surface acoustic wave (SAW) excitation module excites Rayleigh-type SAW waves on its surface, with frequencies and wavelengths matching the interdigital structure. These SAW waves are efficiently transmitted to the glass substrate of the microfluidic chip via silicone oil coupling agent 7, where they excite Lamb waves, such as... Figure 3 As shown, Lamb waves leak into the liquid medium within the microfluidic cavity, exerting acoustic radiation force on the particles.

[0086] In this example, a pair of surface acoustic wave (SAW) excitation modules are placed on each side of the microfluidic cavity. Their excitation signals have the same frequency but controllable phase. Under the action of the two opposing excitation modules, a standing wave acoustic field is formed within the microfluidic cavity along the direction of the interdigital transducer fingers. When all four excitation modules operate simultaneously, a two-dimensional standing wave acoustic field distribution is formed within the microfluidic cavity, as shown below. Figure 4 As shown, the characteristic of a standing wave sound field is that the sound pressure distribution exhibits a periodic spatial variation, with the sound pressure being the lowest at the wave nodes and the highest at the wave antinodes.

[0087] Ten-micron polystyrene particles suspended within a microfluidic cavity are subjected to a net force directed towards the wave nodes under the influence of acoustic radiation, eventually stabilizing and accumulating at the wave node positions of the two-dimensional standing wave acoustic field, forming a regular two-dimensional periodic array. By adjusting the relative phase difference of the electrical excitation signals of a pair of relatively placed surface acoustic wave excitation modules, the spatial distribution of the standing wave acoustic field can be precisely controlled, causing the wave node positions to shift. The particle array also moves accordingly to the new wave node positions, achieving two-dimensional manipulation of the particles. By independently adjusting the magnitude of the phase difference in two directions, the trajectory and position of the particle array can be flexibly controlled, achieving high-precision, dynamic particle manipulation.

[0088] By rationally configuring the layout of the surface acoustic wave (SAW) excitation module and the parameters of the radio frequency excitation signal, and matching appropriate microfluidic chip structures and materials, this example successfully achieved two-dimensional contactless manipulation of 10-micron polystyrene particles, demonstrating the powerful capabilities and application potential of acoustic tweezers technology in the field of micro- and nano-particle manipulation. This particle manipulation method based on SAW standing wave fields has advantages such as high throughput, high precision, low cost, and easy integration, and is expected to be widely used in many fields such as biomedicine, materials science, and drug screening.

[0089] Example 2

[0090] Steps one through four are the same as in Example 1. The difference is that the internal dimensions of the polydimethylsiloxane cavity used are 6000×900×50um. 3 The interdigitated transducer used has a characteristic wavelength of 400 micrometers, and only two identical surface acoustic wave excitation modules are used. In step five, a mixed carrier liquid containing polystyrene microparticles with diameters of 10 micrometers and 5 micrometers was prepared according to actual application requirements. Compared with single-sized microparticles, the mixed-size microparticle suspension better reflects the size selectivity and resolution of acoustic tweezers technology, and is also more consistent with the complex composition of actual samples. The inner surface of the cavity was pretreated using the same method as in Example 1.

[0091] In the microfluidic chip setup, in addition to the main channel for the sample carrier liquid, two sheath flow channels are introduced, referred to as the primary sheath flow and the secondary sheath flow, respectively. The role of the sheath flow is to form a stable fluid interface on both sides of the main channel, confining the sample carrier liquid to the central region of the main channel through a hydrodynamic focusing effect, preventing its diffusion and contact with the wall surface. This microfluidic chip setup can significantly improve the efficiency and reliability of acoustic tweezers separation.

[0092] In practice, an external syringe pump is used to inject the carrier fluid and sheath fluid into different inlets of the microfluidic cavity. For the sample carrier fluid, it is injected into the sample inlet of the cavity through the microfluidic tube at a flow rate of 0.6 μL / min. This flow rate needs to be optimized based on parameters such as particle size, density, and cavity size to ensure that the particles can stably enter the manipulation area while avoiding excessive flow rate that could affect the time and effectiveness of acoustic tweezers manipulation. For the sheath fluid, deionized water is injected into the main and secondary sheath inlets at flow rates of 1.4 μL / min and 0.4 μL / min, respectively. A suitable sheath flow rate can create a stable hydrodynamic focusing effect in the main channel, confining the sample carrier fluid within a specific width range.

[0093] In step six, a suitable radio frequency (RF) excitation signal is selected for acoustic tweezers manipulation and particle sorting based on the settings of the surface acoustic wave (SAW) excitation module and the microfluidic cavity. This example uses a 9.95MHz sinusoidal continuous wave signal, which matches the center frequency of the SAW excitation module, generating efficient and stable SAW waves. Unlike the aforementioned two-dimensional manipulation example, only two independent RF excitation signals are used here, generated by an external RF drive circuit (including a signal generator and power amplifier), and applied to the interdigital transducers of two oppositely placed SAW excitation modules via impedance matching circuit module 1 and bus control circuit 5.

[0094] When an radio frequency electrical signal is applied to the interdigital transducer, the surface acoustic wave (SAW) excitation module excites SAW waves on its surface with frequencies and wavelengths matching the interdigital structure. These SAW waves are efficiently transmitted to the working substrate of the microfluidic chip via acoustic coupling agent 7, where they excite Lamb waves, such as... Figure 3 As shown, Lamb waves leak into the liquid medium within the microfluidic cavity, exerting acoustic radiation force on the particles.

[0095] In this example, a surface acoustic wave (SAW) excitation module is placed on each side of the microfluidic cavity. Their excitation signals have the same frequency but controllable phase. Under the action of the two opposing excitation modules, a one-dimensional standing wave acoustic field is formed within the microfluidic cavity along the direction of the interdigital transducer fingers, as shown below. Figure 4 As shown, unlike the conventional standing wave sound field perpendicular to the flow direction, the nodal lines of the standing wave sound field are set at a 15° angle to the streamlines of the cavity. This tilted one-dimensional standing wave sound field setting can establish a balance between the transverse component of the acoustic radiation force and the longitudinal component of the fluid drag force, thereby achieving particle sorting under continuous flow conditions.

[0096] Within the tilted one-dimensional standing wave acoustic field region, suspended 10-micron and 5-micron polystyrene particles are simultaneously subjected to acoustic radiation force and Stokes drag force. The acoustic radiation force is the time-averaged force exerted on the particles by the acoustic field, and its magnitude is proportional to the particle's volume. Therefore, the 10-micron particles experience a much greater acoustic radiation force than the 5-micron particles. During the continuous flow of the sample carrier liquid, the 10-micron particles experience significant lateral displacement under the influence of the lateral component of the acoustic radiation force, gradually deviating from their original streamlines. In contrast, the 5-micron particles experience a smaller acoustic radiation force, resulting in very limited lateral displacement, essentially remaining on their original streamlines.

[0097] When the particles reach the outlet of the cavity, due to the accumulated difference in lateral displacement, 10-micrometer and 5-micrometer particles will flow out from different outlet channels, achieving size-based passive sorting. The sorted particles can be collected into different containers or introduced into subsequent detection and analysis units for further characterization and processing.

[0098] By setting up a tilted one-dimensional standing wave acoustic field and balancing the effects of acoustic radiation force and fluid drag force, this example successfully achieved continuous flow sorting of mixed-size particles, demonstrating the unique advantages of acoustic tweezers technology in the manipulation and separation of micro- and nano-sized particles. This chip platform, integrating acoustic manipulation and microfluidics, offers advantages such as high throughput, high precision, low cost, and ease of integration, and is expected to find wide application in numerous fields including biomedicine, materials science, and environmental monitoring, thus driving the development of micro- and nano-scale sample processing and analysis techniques.

[0099] Example 3

[0100] Steps one through four are the same as in Example 1. The difference is that a microfluidic droplet-type application function module 9 is used, and the quartz glass working substrate size is 24×24×0.17mm. 3 The interdigital transducers used had a characteristic wavelength of 200 micrometers, and only two identical surface acoustic wave (SAW) excitation modules were used. In step five, three different liquid materials were prepared according to actual application requirements: colored ink, glycerol, and a carrier liquid containing 1-micrometer-diameter polystyrene particles. The colored ink was mainly used for tracing and visualization, while glycerol is a commonly used viscoelastic fluid. The carrier liquid containing 1-micrometer-diameter polystyrene particles was used to investigate the enrichment and manipulation capabilities of acoustic tweezers for small objects.

[0101] During the experimental preparation phase, a suitable amount of liquid carrier is dropped onto a specific location on the working substrate using a syringe or pipette. The selection of this location requires consideration of factors such as the chip layout, the arrangement of the surface acoustic wave (SAW) excitation modules, and the desired droplet manipulation mode. In this example, the liquid carrier is placed near a corner of the working substrate. Two adjacent SAW excitation modules generate a traveling wave sound field, producing an asymmetric acoustic flow effect, thereby driving the droplet along the same rotational direction.

[0102] When a radio frequency (RF) signal is applied to two adjacent surface acoustic wave (SAW) excitation modules, they excite traveling wave-type SAW waves propagating in a specific direction on the surface of the working substrate. Unlike standing wave sound fields, traveling wave sound fields do not have fixed nodes and antinodes in space, but instead exhibit continuous propagation of crests and troughs. When the high-frequency traveling wave sound field encounters a droplet on the surface of the working substrate, it generates a strong acoustic flow effect within the droplet, propelling the droplet to rotate along the direction of sound propagation.

[0103] Inside the droplet, the traveling wave acoustic field drives the fluid to generate internal vortex acoustic flow, causing the suspended 1-micron polystyrene particles to move accordingly. Under the combined action of acoustic radiation force and viscous drag force, the particles form specific distribution and aggregation patterns within the droplet. This example fully utilizes the harmonic flow effect of ultrasonic traveling waves to achieve flexible manipulation of droplets and particles on a microfluidic chip.

[0104] In step six, a suitable radio frequency (RF) excitation signal is selected for droplet manipulation and particle centrifugation based on the settings of the surface acoustic wave (SAW) excitation module and the working substrate. This example uses a 19.9 MHz sinusoidal continuous wave signal, which matches the center frequency of the SAW excitation module, generating efficient and stable SAW waves. Unlike the previous examples, two independent RF excitation signals are used here, applied to two adjacent SAW excitation modules respectively, to generate mutually orthogonal traveling wave sound fields.

[0105] When an radio frequency electrical signal is applied to the interdigital transducer, the surface acoustic wave (SAW) excitation module excites SAW waves on its surface with frequencies and wavelengths matching the interdigital structure. These SAW waves are efficiently transmitted to the working substrate of the microfluidic chip via acoustic coupling agent 7, where they excite Lamb waves, such as... Figure 3 As shown, Lamb wave leakage enters the microfluidic droplets, causing vortex acoustic flow.

[0106] In this example, two adjacent surface acoustic wave (SAW) excitation modules apply orthogonal traveling wave acoustic fields from two sides of the droplet. Under this bidirectional asymmetric excitation, the droplet rotates on the surface of the working substrate, as shown below. Figure 5 As shown.

[0107] To achieve the mixing of glycerol and water droplets, 1 μL of glycerol and 1 μL of colored ink are first dropped onto specific locations on the working substrate. Then, an radio frequency excitation signal is activated, causing two surface acoustic wave (SAW) excitation modules to generate orthogonal traveling wave sound fields. Under the influence of acoustic radiation stress, the glycerol and colored ink droplets rapidly fuse and continuously stretch and deform during rotation, achieving uniform and thorough mixing in a very short time. This ultrasound-driven mixing method is simple to operate, provides thorough mixing, and is time-efficient, showing promise for important applications in accelerating chemical reactions and PCR synthesis.

[0108] To centrifuge 1-micrometer-diameter polystyrene particles, a 2 μL droplet containing the particles is placed at a specific location on a working substrate. Upon activation of the radio frequency excitation signal, the droplet rotates at high speed under the influence of an orthogonal traveling wave acoustic field, creating a centrifuge-like effect. Under centrifugal force, the 1-micrometer polystyrene particles suspended in the droplet gradually migrate towards the edge, eventually forming a ring-shaped aggregation zone, achieving rapid enrichment and separation of micro- and nano-particles. This acoustically driven centrifugation method requires no complex mechanical devices, is simple to operate, and highly flexible, making it promising for widespread application in the separation and purification of tiny samples such as biomolecules, cells, and microcapsules.

[0109] The foregoing illustrative description of the invention and its embodiments is not restrictive and can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. The accompanying drawings are only one embodiment of the invention, and the actual structure is not limited thereto. No reference numerals in the claims should limit the scope of the claims. Therefore, if a person skilled in the art, inspired by this description, creates a similar structure and embodiment without departing from the spirit of the invention, such a creation should fall within the scope of this patent. Furthermore, the word "comprising" does not exclude other elements or steps, and the word "a" preceding an element does not exclude the inclusion of "a plurality" of that element. Multiple elements stated in the product claims can also be implemented by a single element through software or hardware. The terms "first," "second," etc., are used to indicate names and do not indicate any specific order.

Claims

1. A surface acoustic wave microfluidic acoustic tweezers device, characterized in that: include: Surface acoustic wave excitation module, application function module, coupling agent; The surface acoustic wave excitation module includes an interdigital transducer and a piezoelectric wafer. The interdigital transducer is disposed on the piezoelectric wafer and is used to excite surface acoustic waves on the piezoelectric wafer and couple the surface acoustic waves to the application function module through a coupling agent. The application function modules include microfluidic droplet type and microfluidic cavity type. The microfluidic droplet type application function module is composed of a working substrate, and the microfluidic cavity type application function module is composed of a microfluidic cavity and a working substrate. Surface acoustic waves couple out Lamb waves in the working substrate and propagate into the microfluidic fluid to perform particle manipulation. It also includes: bus control circuitry and impedance matching module; The bus control circuit is used to connect the surface acoustic wave excitation module and the impedance matching module, and to conduct the circuits of both so that the radio frequency signal can be transmitted from the impedance matching module to the surface acoustic wave excitation module. Impedance matching module is used to perform impedance matching between surface acoustic wave excitation module and bus control circuit to match the impedance of surface acoustic wave excitation module and external drive circuit, thereby reducing signal reflection; The impedance matching module uses a magnetic spring pin element to connect to the bus control circuit, and transmits the radio frequency signal to the bus control circuit through the magnetic spring pin element. The impedance matching module uses standard RF interface components to connect to the external drive circuit and receives RF signals input from the external drive circuit through the standard RF interface components. Also includes: device master plate and microscope stage adapter; The device master plate is used to fix the surface acoustic wave excitation module, application function module, bus control circuit and impedance matching module to enable physical connection and data transmission between modules; Microscope stage adapter, used to fix the device motherboard to the microscope stage; The bus control circuit is fixed below the mother plate of the device and is connected to the interdigital transducer on the surface acoustic wave excitation module by a spring pin array, transmitting the radio frequency signal from the bus control circuit to the interdigital transducer. The bus control circuit uses a magnetic spring pin element to connect with the impedance matching module, transmitting the radio frequency signal from the impedance matching module to the bus control circuit.

2. A surface acoustic wave (SAW) microfluidic acoustic tweezers method for executing the SAW microfluidic acoustic tweezers device of claim 1, comprising: The assembly includes a motherboard, a bus control circuit, and a microscope stage adapter. The bus control circuit is fixed below the motherboard and physically connected to it. Select either the microfluidic droplet type application function module or the microfluidic cavity type application function module according to the application objectives; and place the selected application function module on the device master plate; Based on the selected application function module, select the surface acoustic wave excitation module containing interdigital transducers and piezoelectric wafers, and align the interdigital transducers with the spring pin array of the bus control circuit. The selected application function module and the surface acoustic wave excitation module are acoustically coupled using a coupling agent. Connect the busbar of the interdigital transducer to the spring pin array of the bus control circuit to form a transmission channel for radio frequency signals; The impedance matching module is connected to the bus control circuit via a magnetic spring pin element to form a transmission channel for radio frequency signals. The impedance matching module is connected to the external drive circuit through standard RF interface components to form a RF signal transmission channel; Injecting microfluidic liquid containing microparticles to be manipulated into the application function module as a carrier liquid; injecting droplets directly into the microfluidic droplet type application function module; injecting liquid into the microfluidic cavity type application function module; The radio frequency signal is input to the impedance matching module through the external driving circuit, and then transmitted to the bus control circuit through the impedance matching module, and then transmitted to the surface acoustic wave excitation module through the bus control circuit. The interdigitated transducer in the surface acoustic wave excitation module excites Rayleigh surface acoustic waves on the piezoelectric wafer; the Rayleigh surface acoustic waves excite Lamb waves in the application function module through a coupling agent, and the particles are manipulated without contact through the Lamb waves; By changing the parameters of the radio frequency signal, particle arrangement, migration, and separation operations can be performed; Also includes: By adjusting the resistance values ​​of capacitors and inductors in the impedance matching module, the impedances of different surface acoustic wave excitation modules and external drive circuits are matched, thereby reducing the reflection of radio frequency signals. The frequency of the radio frequency signal is matched with the characteristic frequency of the interdigital transducer in the surface acoustic wave excitation module.

3. The surface acoustic wave microfluidic acoustic tweezers method according to claim 2, characterized in that: When arranging and manipulating particles, the type and size of the selected surface acoustic wave excitation module and microfluidic cavity application function module are set according to the acoustic contrast factor between the particles and the fluid carrier liquid and the preset sorting target; and the corresponding drive control signal is set according to the acoustic contrast factor and the preset sorting target to control the surface acoustic wave excitation module to generate the corresponding surface acoustic wave.

4. The surface acoustic wave microfluidic acoustic tweezers method according to claim 3, characterized in that: When sorting particles, the type and size of the microfluidic cavity are set according to the acoustic contrast factor of the particles to be sorted and the preset sorting target, and the liquid flow rate in the cavity is controlled; at the same time, the type and size of the selected surface acoustic wave excitation module and the microfluidic cavity application function module are set; and according to the acoustic contrast factor and the preset sorting target, the corresponding drive control signal is set to control the surface acoustic wave excitation module to generate the corresponding surface acoustic wave.

5. The surface acoustic wave microfluidic acoustic tweezers method according to claim 4, characterized in that: During droplet mixing and centrifugation of particles within the droplets, the type and size of the selected surface acoustic wave excitation module and microfluidic droplet application function module are set according to the type of sample particles and the preset application objectives. The position of the droplet in the microfluidic droplet application function module is also set. The corresponding driving signal is set according to the type of sample particles and the preset application objectives.

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