A method for fabricating and testing a vortex self-focusing transducer

Abstract

This invention provides a method for fabricating and testing a vortex self-focusing transducer, including the design of the transducer housing, a laser cutting scheme for the piezoelectric ring array, the transducer packaging process, and a method for measuring and analyzing the vortex self-focusing acoustic field. It is suitable for emitting and verifying high-frequency vortex-focused acoustic waves of MHz and above. The design balances the requirements of the transducer housing and the concave piezoelectric ring array, enabling the emission of a vortex-focused acoustic field with a more uniform circumferential intensity distribution. Furthermore, the circuit design and transducer packaging fabrication are less complex, relying on a smaller number of signal generation and power amplification channels, and allowing dynamic adjustment of the topological order of the vortex-focused beam. The vortex-focused acoustic field measurement method overcomes the shortcomings of mechanical scanning methods, offering advantages in real-time observation of changes in the vortex acoustic field. It can quickly determine the acoustic field profile and change the topological order, facilitating the future application of high-quality, tunable vortex-focused acoustic fields to intelligent acoustic tweezers technology.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic transducers, specifically relating to a method for fabricating and testing a vortex self-focusing transducer. Background Technology

[0002] Vortex-focused acoustic waves are an important waveform required for the future development of acoustic tweezers technology. The principle involves modulating a gradually changing phase in the circumferential direction in cylindrical coordinates, and defining the topological order of the vortex-focused acoustic wave based on the number of circumferential phase periods. The topological order is proportional to the size of the acoustic potential well in the acoustic tweezers. Currently, there are three main methods for generating vortex-focused acoustic waves:

[0003] The first type is a passive phased array based on passive sound field modulation. By changing the geometric and material parameters of the internal periodic arrangement units, the incident sound wave is modulated into a spiral-shaped output phase to obtain a vortex-focused sound wave. A typical example is a metasurface acoustic lens.

[0004] The second type is a phased array ultrasonic transducer based on active acoustic field modulation, which emits vortex-focused sound waves by modulating the emission phase of each array element according to the delay method.

[0005] The third method combines the first two approaches. For example, a spiral groove is cut into a piezoelectric material using the acoustic ray method. Due to the difference in the geometric path of sound propagation, a vortex-focused sound wave is formed, which combines the passive sound field modulation and active emission methods mentioned above.

[0006] The second method, phased array ultrasonic transducers, uses a multi-channel circuit system to independently control array elements, offering greater flexibility in the dynamic control of vortex-focused acoustic waves compared to the first method. However, phased array transducers require a large number of array elements for vortex-focused acoustic waves, especially planar phased array ultrasonic transducers, which demand complex circuit designs. The fabrication and manufacturing processes for these transducers are challenging and costly, hindering the widespread application of acoustic tweezers technology.

[0007] The development of acoustic tweezers technology requires real-time dynamic control of the acoustic potential well size of the vortex focusing beam, and a uniform circumferential distribution of acoustic radiation force to stably capture particles of different sizes. This places new demands on the measurement methods of vortex focusing sound fields, namely, higher real-time performance and the ability to observe the sound field in three dimensions. However, current methods for measuring vortex sound fields mainly rely on sound field scanning devices. These devices use a three-axis mechanical displacement stage to measure the target space point by point, then calculate the sound intensity and sound pressure distribution based on the sound pressure amplitude at all points. This spatial resolution heavily depends on the stepping accuracy of the mechanical movement device, does not utilize high-frequency transducers, and suffers from slow measurement speed. Furthermore, the sound pressure field of vortex-focused sound waves exhibits asymmetric characteristics in three-dimensional space. The scanning method limits the transducer's testing efficiency, especially in large measurement spaces, and lacks the ability to observe sound field changes in real time, hindering research on the synchronous control of the sound field during acoustic tweezers particle manipulation. Summary of the Invention

[0008] This invention proposes a method for fabricating and testing a vortex self-focusing transducer, aiming to achieve dynamic control and real-time measurement of the topological order of vortex-focused acoustic waves. The invention includes the design of the vortex self-focusing transducer housing, the laser cutting scheme for the piezoelectric ring array, the transducer packaging process, and methods for emitting, measuring, and analyzing the vortex self-focusing sound field.

[0009] This invention provides a vortex self-focusing transducer for use in liquid environments, comprising a vortex self-focusing transducer housing, a crown-shaped piezoelectric ring array, and a resin sealing body. The vortex self-focusing transducer housing includes spaced-apart outer and inner walls, multiple locking plates, a sealing plate, and a central pre-drilled hole formed by the inner walls. The crown-shaped piezoelectric ring array has multiple fan-shaped concave piezoelectric elements circumferentially, with a pre-drilled central hole. The resin sealing body includes a backing and a matching layer; the matching layer is concave and has the same curvature as the piezoelectric element.

[0010] The coronal piezoelectric ring array has a number of fan-shaped concave piezoelectric elements greater than or equal to 8. It is formed by cutting the surface electrode of the concave piezoelectric sheet in multiple layers by a laser cutting machine. During the surface electrode cutting process, the focus of the laser cutting machine needs to be changed multiple times in the height direction.

[0011] The tools for manufacturing a vortex self-focusing transducer include: a laser cutter, a metal ball, a metal ball connecting rod, a lifting platform, a connecting plate, flat-jaw pliers, and a metal cylinder.

[0012] Using the aforementioned manufacturing tools, the manufacturing steps for the vortex self-focusing transducer include:

[0013] Step 1: Multiple positive wires pass through the wire holes of the sealing plate, and each wire is electrically connected to each sector element of the crown piezoelectric ring array.

[0014] Step 2: Use quick-drying epoxy resin or glue to bond the crown piezoelectric ring array to the outer and inner wall mounting plates of the piezoelectric sheet in the vortex focusing transducer housing, and wait for the epoxy resin or glue to cure.

[0015] Step 3: Seal the wire hole with quick-drying epoxy resin or glue;

[0016] Step 4: Wrap the metal ball with plastic film, or spray the surface of the metal ball with anti-stick agent, and wrap the outer wall of the transducer housing with polyimide tape;

[0017] Step 4: Apply an anti-sticking agent to the concave metal cylinder and insert it into the central pre-drilled hole formed by the inner wall of the transducer housing;

[0018] Step 5: Mix the epoxy resin and curing agent in a 4:1 ratio and place them in a vacuum machine to remove air bubbles;

[0019] Step 6: Fill the space between the outer and inner walls with the mixed curing agent and the de-bubbled epoxy resin until it is full;

[0020] Step 7: Press the metal ball firmly onto the top of the vortex focusing transducer and wait at least 24 hours for the epoxy resin to solidify;

[0021] Step 8: Remove the metal ball and the metal cylinder in the center of the outer shell, peel off the plastic film on the metal ball and the tape on the outer wall to complete the fabrication of the vortex focusing transducer.

[0022] The measuring device of the vortex self-focusing transducer includes: a multi-channel signal generator, a multi-channel power amplifier, a multi-jaw mechanical chuck, a chuck connecting rod, a rotary motor, a rotary clamp and universal coupling, a rotary motor bracket, a transparent water tank, sound-absorbing material, a laser irradiation system and an image acquisition system.

[0023] The number of channels in the signal generator and power amplifier is determined based on the topological order of the vortex-focused acoustic wave. The number of channels is equal to a = m / l, where m is the number of concave sector array elements and l is the topological order of the vortex acoustic wave.

[0024] The measurement method for vortex sound fields is based on the Schlieren principle, which states that the sound field causes density changes in the spatial medium. A laser irradiation system emits uniformly collimated light that passes through a non-uniformly distributed vortex focusing sound field, and an image acquisition system receives the diffraction fringe image caused by the density changes in the spatial medium. The measurement image obtained by the Schlieren method is a projection of the vortex sound field; that is, the projected image is a two-dimensional result of the superposition of three-dimensional spatial physical fields along the laser direction.

[0025] The measurement steps for a vortex self-focusing transducer include:

[0026] Step 1: Install the vortex self-focusing transducer on a three-jaw or four-jaw mechanical chuck;

[0027] Step 2: Calculate the phase delay compensation required for each sector concave piezoelectric element of the coronal piezoelectric ring array according to the phased array delay law; allocate a elements for each phase period in the circumferential direction, and calculate the time delay of the nth element in each phase period as (n-1)t / a+ct, where t is the time period of the sound wave and c is a natural number.

[0028] Step 3: Keep the multi-channel signal generator off first, use the silent field image acquired by the image acquisition system at this time as the background image, and then turn on the multi-channel signal generator and multi-channel power amplifier. Determine whether the vortex focusing sound field is being emitted normally based on the ripple results in the image.

[0029] Step 4: The focusing transducer is rotated around its geometric center by a motor with a fixed rotation step size, rotating a total of 180 degrees, and one or more images are recorded each time the rotation is completed.

[0030] Step 5: Subtract the background image from all the images recorded during the rotation process to remove background noise;

[0031] Step 6: Filter the image using at least one of Gaussian, bilateral, or median filtering methods;

[0032] Step 7: Convert the sound pressure schlieren map into a sound intensity map;

[0033] Step 8: Combine the images from all angles into an array, and perform an inverse Radon transform on the data of each cross-section along the vertical direction to obtain the reconstructed three-dimensional sound field;

[0034] Step 9: Analyze the focal length, sound pressure distribution of the beam cross section, sound intensity distribution of the beam cross section, and size of the acoustic potential well based on the measurement and transformation results. If there is obvious asymmetry in the left and right sound intensity fields, it indicates that the signal transmission is incorrect or the array element is damaged.

[0035] In step 7 above, the calculation method for converting the sound pressure schlieren map into a sound intensity map includes:

[0036] Method 1: Within one time period or wavelength of the sound wave, continuously capture 10 or more images, superimpose all images, and normalize them to obtain a sound intensity distribution map; or,

[0037] Method 2: Subtract 255 / 2 from the grayscale value of the sound pressure splay image and take the absolute value. Extract the maxima and their coordinates corresponding to all peaks and troughs. Use the maxima to construct an envelope diagram to obtain the sound intensity distribution map; or,

[0038] Method 3: Simultaneously change the emission phase of all array elements of the transducer with a phase step size of 1 / 10 or smaller, keep the phase difference between each array element unchanged, record the image corresponding to each phase, and superimpose and normalize all images to obtain the sound intensity distribution map.

[0039] The beneficial effects of the vortex self-focusing transducer and its testing method of this invention are as follows: It can achieve vortex self-focusing and dynamically adjust its topological order, emitting a vortex-focused sound field with uniform circumferential intensity distribution. Compared with current sound field scanning measurement devices, the testing method has high real-time performance, allowing for real-time observation and adjustment of the acoustic potential trap size. Secondly, the fabrication method of the vortex focusing transducer of this invention is simple. The crown-shaped piezoelectric ring array and its phase modulation method can effectively reduce the channel requirements of the signal generator and power amplifier, reduce the complexity of circuit design, and save on electronic component costs.

[0040] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the casing of a vortex self-focusing transducer.

[0043] Figure 2 This is a schematic diagram of laser cutting and electrical connection of a coronal piezoelectric ring array.

[0044] Figure 3 The phase distribution diagrams of the focal cross section are shown when the number of array elements is 4, 6, 8, and 12.

[0045] Figure 4 The sound intensity distribution diagrams are shown for the cross-section of the focal point when the number of array elements is 4, 6, 8, and 12.

[0046] Figure 5 This is a schematic diagram of the packaging tool for a vortex self-focusing transducer.

[0047] Figure 6 This is a schematic diagram of an experimental test of a vortex focusing transducer.

[0048] Figure 7 It is a transducer clamp that can rotate 360 ​​degrees.

[0049] Figure 8 This is a schematic diagram of a cross-sectional Schlieren projection image of a vortex-focused acoustic wave.

[0050] Figure 9 The longitudinal acoustic pressure projection result of the first-order vortex focusing beam.

[0051] Figure 10 This is a sound pressure distribution diagram of the longitudinal section of the center of the first-order vortex focusing beam.

[0052] Figure 11 The sound pressure distribution diagrams are shown in the longitudinal profiles of the center of the first to third order vortex focusing beams.

[0053] Labeling Explanation: 1. Vortex Focusing Transducer Housing; 101. Outer Wall; 102. Inner Wall; 103. Central Pre-drilled Hole; 104. Outer Wall Mounting Stage for Crown Piezoelectric Ceramic Sheet; 105. Inner Wall Mounting Stage for Crown Piezoelectric Ceramic Sheet; 106. Outer Wall Mounting Stage for Metal Ball; 107. Backing Casting Sealing Plate; 108. Wire Hole; 109. Wire Groove; 201. Crown Piezoelectric Ring Array; 202. Top Surface; 203. Bottom Surface; 204. Laser Cutting Machine; 2a-2d. Laser Cutting Focal Point Position; 205. Fan-shaped Concave Piezoelectric Array Element; 206. Cutting Groove; 207. Central Hole. 208 Multi-channel power amplifier, 209 Multi-channel signal generator, 301 Lifting displacement stage, 302 Connecting plate, 303 Metal ball connecting rod, 304 Metal ball, 305 Flat-jaw pliers, 306 Vortex self-focusing transducer, 307 Metal cylinder, 401 Three-jaw or four-jaw mechanical chuck, 402 Chuck connecting rod, 403 Coupling, 404 Rotary motor, 405 Bracket, 406 Transparent water tank, 407 Sound-absorbing material, 408 Laser irradiation system, 409 Image acquisition system, 410 Rotatable fixing clamp or universal coupling. Detailed Implementation

[0054] This invention provides a method for fabricating and testing a vortex self-focusing transducer applicable to liquid environments. The invention, in conjunction with the accompanying drawings, provides a detailed explanation of its principle, design method, fabrication process, testing method, and beneficial effects.

[0055] The fabrication and testing tools for vortex self-focusing transducers include the vortex self-focusing transducer itself, its fabrication tools, and testing tools. The vortex self-focusing transducer includes: a transducer housing, a crown-shaped piezoelectric ring array, and a resin seal. The fabrication tools include: a laser cutter, metal spheres, metal sphere connecting rods, a lifting platform, a connecting plate, flat-jaw pliers, and a metal cylinder. The testing tools include: a multi-channel signal generator, a multi-channel power amplifier, a multi-jaw mechanical chuck, a chuck connecting rod, a rotary motor, a rotary clamp and universal coupling, a rotary motor bracket, a transparent water tank, sound-absorbing materials, a laser irradiation system, and an image acquisition system.

[0056] Vortex focusing transducer housing 1 as shown Figure 1As shown, the device includes an outer wall 101 and an inner wall 102 spaced apart. The height of the inner wall 102 is lower than that of the outer wall 101. The outer diameter of the inner wall 102 is equal to the inner diameter of the central hole 207 of the crown piezoelectric ring array 201. The upper surface of the inner wall 102 is flush with the bottom surface 203 of the crown piezoelectric ring array 201. A central reserved hole 103 formed by the inner wall 102 is reserved inside the vortex focusing transducer housing 1 for mounting devices such as cameras. To fix the crown piezoelectric ring array 201 above the housing, multiple outer wall mounting platforms 104 and inner wall mounting platforms 105 for crown piezoelectric ceramic sheets are provided on the outer wall 101 and the inner wall 102, respectively. The gap between the upper surface of the inner wall mounting platform 105 and the inner wall 102 is equal to the thickness of the crown piezoelectric ring array 201 plus the thickness of the matching layer. Similarly, the gap between the outer wall mounting plate 106 of the metal sphere and the inner wall mounting plate 105 of the crown piezoelectric ceramic sheet is the sum of the thickness of the piezoelectric sheet and the thickness of the matching layer.

[0057] The matching layer is generally made of epoxy resin because the acoustic impedance of epoxy resin is similar to that of liquid. The thickness of the matching layer is usually 1.16(2n-1)λ / 4, which is about 1 / 4 of the wavelength in an odd multiple, to reduce the transmission loss of sound waves. n is a natural number and λ is the wavelength of sound wave propagation in the matching layer material.

[0058] To facilitate subsequent epoxy resin filling, a gap exists between the crown-shaped piezoelectric ring array 201 and the outer wall 101, allowing the epoxy resin liquid to enter the space between the inner wall 102 and the outer wall 101. Simultaneously, the resin seal prevents short circuits caused by the liquid from affecting the normal operation of the crown-shaped piezoelectric ring array 201. To prevent leakage before the backing material cures and to prevent wires from sticking together, a backing potting sealing plate 107 is provided at the bottom of the vortex focusing transducer housing 1. The backing potting sealing plate 107 is positioned between the outer wall 101 and the inner wall 102, and is connected to both the outer wall 101 and the inner wall 102. The wires of the fan-shaped concave piezoelectric array element 205 are led out through wire holes 108; the number of wire holes 108 depends on the actual number of wires. Then the wires are led out from the wire groove 109 at the bottom edge of the outer wall 101. The purpose of the wire groove 109 is to facilitate the flat placement of the transducer and make it easy to encapsulate. At the same time, it can prevent the transducer from being tilted, which would cause the emission direction of the vortex sound wave to deviate.

[0059] The material of the coronal piezoelectric ring array 201 can be either piezoelectric ceramic or piezoelectric composite material. For example... Figure 2As shown, the coronal piezoelectric ring array 201 has a pre-drilled central hole 207, which mates with the central pre-drilled hole 103 of the vortex focusing transducer housing 1. Compared with a piezoelectric sheet with a complete curved surface, the bottom surface 203 can provide stable placement during laser cutting, preventing the piezoelectric sheet from wobbling during laser cutting. To emit the spiral phase required for vortex focusing sound waves, multiple fan-shaped concave piezoelectric array elements 205 need to be constructed. In this invention, a laser cutting machine 204 is used to cut the surface electrodes of the coronal piezoelectric ring array 201 into n equal parts along the circumference. Before laser cutting, four dot-shaped marks can be made on the top surface 202 or the bottom surface 203 of the coronal piezoelectric ring array 201 respectively, so that the center of the ring piezoelectric sheet can be positioned by the laser cutting machine 204 before cutting.

[0060] To ensure the uniformity of the cutting grooves 206 of the coronal piezoelectric ring array 201 along the height direction of the curved surface, the focal position of the laser cutting machine 204 is set differently in the height direction. That is, the focal point of the laser cutting machine is changed multiple times during the cutting process, resulting in multiple layers of cutting the surface electrodes of the coronal piezoelectric ring array 201 in the height direction. Since the surface electrodes are relatively thin, this invention recommends a laser power of less than 5W, more than 5 cuts per layer, and a delay of more than 0.1s between each cut. The cutting process follows the principle of reducing laser power and increasing the number of cuts, ideally only requiring the surface electrodes to be completely divided. The purpose of setting a delay for each cut is to avoid excessive heat and protect the polarization characteristics of the piezoelectric material.

[0061] Assuming the height of the coronal piezoelectric ring array 201 is h, and it is divided into n layers along the height direction, the laser cutting focus moves h / (n-1) along the height direction after each layer is cut. For example, if the cutting is divided into n=4 layers, the laser focus position 2a is h=0 for the first laser, 2b is h / 3 for the second laser, 2c is 2h / 3 for the third laser, and 2d is h for the fourth laser. Theoretically, the more layers in the height direction, the better the consistency of the width of the cutting groove 206. Then, a multimeter is used to contact the surface electrodes of adjacent sector-shaped concave piezoelectric array elements 205 to measure electrical continuity. If adjacent sector-shaped concave piezoelectric array elements 205 are not connected, the cutting is considered complete. If the sector-shaped concave piezoelectric array elements 205 are connected, the number of cutting layers needs to be increased until adjacent elements are no longer connected.

[0062] The more fan-shaped concave piezoelectric elements 205 there are, the smaller the step size of the circumferential phase setting can be, resulting in a better spiral phase effect and a more uniform circumferential intensity distribution at the focal position. For example... Figure 3 As shown, the four sub-figures represent the phase distribution of the cross-section at the focal point of the vortex-focused acoustic wave when the number of 205 piezoelectric elements in the fan-shaped concave surface is 4, 6, 8, and 12. Figure 4As shown, the four sub-figures represent the sound intensity distribution at the cross-section of the vortex-focused acoustic wave focal point when the number of 205 fan-shaped concave piezoelectric array elements is 4, 6, 8, and 12. It can be seen that when the number reaches 8, the distribution characteristics of the central phase tend to be stable, and the sound intensity distribution tends to be a smooth ring.

[0063] The positive terminals of all the concave piezoelectric elements 205 are independently connected to a multi-channel power amplifier 208, and then independently connected to a multi-channel signal generator 209. For high-order vortex-focused acoustic waves, to save on instrument channels and reduce device costs, a repeating signal channel can be used for each phase cycle. That is, the number of channels is determined by the topological order of the vortex-focused acoustic wave, and the number of channels equals a = m / l, where m is the number of concave piezoelectric elements and l is the topological order of the vortex acoustic wave. For example, if the topological order of the vortex acoustic wave is l = 2 and the number of concave piezoelectric elements 205 is m = 12, then the number of channels in the signal generator and power amplifier is a = 6. In this case, every 6 concave piezoelectric elements 205 constitute one phase cycle, and the first and seventh concave piezoelectric elements 205 can use the same signal channel.

[0064] After all the sector-shaped concave piezoelectric array elements 205 are electrically connected, the crown-shaped piezoelectric ring array 201 needs to be encapsulated in the vortex focusing transducer housing 1. The encapsulation tool is as follows: Figure 5 As shown, the metal ball connecting rod 303 connects the metal ball 304 with a threaded hole and the connecting plate 302. The radius of the metal ball 304 is equal to the curvature of the crown piezoelectric ring array 201. Before encapsulation, the concave metal cylinder 307 needs to be placed into the pre-drilled hole 103 in the center of the vortex focusing transducer housing 1. The curvature of the concave surface of the concave metal cylinder 307 is also equal to the curvature of the crown piezoelectric ring array 201. The connecting plate 302 is fixed on the lifting platform 301, and the vortex self-focusing transducer 306 is clamped by flat-jaw pliers 305. Using the above tools, the basic steps for encapsulating the vortex self-focusing transducer 306 are as follows:

[0065] Step 1: Multiple positive wires are passed through the wire hole 108, and each wire is individually electrically connected to each sector concave piezoelectric element 205. Then, the wire hole 108 is sealed in drop form using quick-drying epoxy resin or glue.

[0066] Step 2: Use quick-drying epoxy resin or glue to gently bond the crown piezoelectric ring array 201 to the outer wall mounting base 104 and inner wall mounting base 105 of the crown piezoelectric ceramic sheet of the vortex focusing transducer housing 1 in drop form, and wait for the epoxy resin or glue to solidify.

[0067] Step 3: Wrap the metal ball 304 with a tough plastic film, such as cling film or tape, or spray an anti-sticking agent on the surface of the metal ball 304. Wrap the outer wall 101 of the vortex focusing transducer housing 1 with polyimide tape, ensuring that no obvious wrinkles appear on the wrapped surface.

[0068] Step 4: Apply anti-sticking agent to the metal cylinder 307 with a concave upper surface, pass the metal cylinder 307 through the central hole 207 of the crown piezoelectric ring array 201, and insert it into the central reserved hole 103 of the vortex focusing transducer housing 1. The function of the metal cylinder 307 is to prevent the reserved central reserved hole 103 from being blocked during the epoxy resin potting process.

[0069] Step 5: Mix epoxy resin and curing agent in a disposable beaker at a ratio of 4:1, and place the disposable beaker in a vacuum chamber to remove air bubbles from the liquid.

[0070] Step 6: Fill the space between the outer wall 101 and the inner wall 102 of the vortex focusing transducer housing 1 with the prepared epoxy resin.

[0071] Step 7: Use the lifting platform 301 to press the metal ball 304 firmly onto the top of the vortex self-focusing transducer 306, and wait for 24 hours or more;

[0072] Step 8: After the epoxy resin has solidified, remove the metal ball 304, peel off the film on the metal ball 304 and the tape on the outer wall 101 of the vortex focusing transducer housing 1, and take out the metal cylinder 307.

[0073] If a hole appears in the solidified epoxy resin, repeat steps 5 to 7 to fill the hole.

[0074] After the vortex self-focusing transducer 306 is packaged, its emitted vortex focused sound field is finally tested. The testing tools for the vortex self-focusing transducer 306 are as follows: Figure 6 and Figure 7 As shown, a three- or four-jaw mechanical chuck 401 clamps the vortex self-focusing transducer 306, with the sound wave emission direction vertically downward. A coupling 403 connects the chuck connecting rod 402 of the three- or four-jaw mechanical chuck 401 to the rotating shaft of a rotary motor 404. The rotary motor 404 is mounted on a bracket 405. The vortex self-focusing transducer 306 is placed in a transparent water tank 406 and submerged in the water. The bottom of the transparent water tank 406 is made of sound-absorbing material 407, which prevents sound wave reflection from the bottom of the transparent water tank 406 from affecting the measurement of the emitted sound field. A laser irradiation system 408 is arranged on one side of the transparent water tank 406, and an image acquisition system 409 is arranged on the other side. To measure the oblique profile of the vortex-focused sound wave, the chuck connecting rod 402 is connected to the rotating shaft of the motor using a rotatable clamp or a universal coupling 410.

[0075] The measurement method for vortex sound fields is based on the Schlieren schlieren principle, such as... Figure 8 As shown, the laser irradiation system 408 emits collimated light rays that pass through a vortex focusing sound field with a non-uniform sound pressure distribution, and then the image acquisition system 409 receives the diffraction fringe image generated by the laser. The image measured by the Schlieren schlieren method is a two-dimensional projection result of the superposition of the three-dimensional spatial physical fields along the laser direction, as shown in the figure. Figure 9 The numerical simulation results show that the sound pressure distribution in the longitudinal profile at the center of the vortex focusing beam is as follows: Figure 10 As shown. The beam center is a potential well, and the size of the potential well is proportional to the absolute value of the topological order of the vortex-focused acoustic wave. For example... Figure 11 As shown, with the increase of the topological order of the vortex-focused acoustic wave, the gap in the middle of the beam becomes larger, indicating that the acoustic potential well increases and can be used to capture particles with larger diameters. The experimental steps for testing the vortex self-focusing transducer are as follows:

[0076] Step 1: Install the vortex self-focusing transducer 306 on the three-jaw or four-jaw mechanical chuck 401.

[0077] Step 2: Calculate the phase delay compensation required for each sector concave piezoelectric array element 205 according to the phased array delay law; allocate a array elements for each phase period in the circumferential direction, and calculate the time delay of the nth array element in each phase period as (n-1)t / a+ct, where t is the time period of the sound wave and c is a natural number.

[0078] Step 3: Keep the multi-channel signal generator 209 off. Use the silent field image acquired by the image acquisition system 409 as the background image. Turn on the multi-channel signal generator 209 and the multi-channel power amplifier 208. Determine whether the vortex focusing sound field is being emitted normally based on the ripple results in the image.

[0079] Step 4: Rotate the vortex focusing transducer around its geometric center by a motor with a fixed rotation step size, for a total rotation of 180 degrees, and record one or more images each time the rotation is completed.

[0080] Step 5: Subtract the background image from all the images recorded during the rotation process to remove background noise.

[0081] Step 6: Filter the image using at least one method such as Gaussian, bilateral, or median.

[0082] Step 7: Convert the sound pressure schlieren map into a sound intensity map.

[0083] Step 8: Combine the images from all angles into an array, and perform an inverse Radon transform on the data of each cross-section along the vertical direction to reconstruct the three-dimensional sound field. The smaller the rotation step size, the better the sound field reconstruction effect.

[0084] Step 9: Analyze the focal length, sound pressure distribution of the beam cross section, sound intensity distribution of the beam cross section, and size of the acoustic potential well based on the measurement and transformation results. If there is obvious asymmetry in the left and right sound intensity fields, it indicates that the signal transmission is incorrect or the array element is damaged.

[0085] For step 7 above, in order to obtain the sound intensity distribution, the following three methods can be used to process the schlieren image:

[0086] Method 1: Take 10 or more images continuously within one time period or wavelength of the sound wave, and then overlay and normalize all the images to obtain a sound intensity distribution map.

[0087] Method 2: Subtract 255 / 2 from the grayscale value of the sound pressure schlieren grayscale image and take the absolute value. Extract the maximum values ​​and coordinates corresponding to all peaks and troughs, and draw an envelope diagram of the maximum values ​​to obtain the sound intensity distribution map.

[0088] Method 3: Synchronously change the emission phase of all elements of the vortex self-focusing transducer with a phase step of 1 / 10 or smaller, while keeping the phase difference between each element unchanged. Record the image corresponding to each phase, and then superimpose and normalize all the images to obtain the sound intensity distribution map.

[0089] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications, additions, or use similar methods to replace the described specific embodiments without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

[0090] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A fabrication and testing tool for a vortex self-focusing transducer, characterized in that, The manufacturing and testing tools include a vortex self-focusing transducer, a tool for manufacturing the vortex self-focusing transducer, and a testing tool for the vortex self-focusing transducer. The vortex self-focusing transducer includes: a vortex focusing transducer housing, a crown-shaped piezoelectric ring array, and a resin sealing body; the crown-shaped piezoelectric ring array is fixed in the vortex focusing transducer housing; the resin sealing body is disposed in the gap between the crown-shaped piezoelectric ring array and the vortex self-focusing transducer housing; The manufacturing tools for the vortex self-focusing transducer include: a laser cutting machine for circumferentially cutting the crown-shaped piezoelectric ring array into multiple piezoelectric units, a metal ball, a metal ball connecting rod, a lifting platform, a connecting plate, flat-jaw pliers, and a metal cylinder; the metal ball connecting rod connects the metal ball with a threaded hole and the connecting plate, and the radius of the metal ball is equal to the curvature of the crown-shaped piezoelectric ring array; before encapsulation, a concave metal cylinder needs to be pre-placed into the central reserved hole of the vortex focusing transducer shell, and the curvature of the concave surface of the concave metal cylinder is also equal to the curvature of the crown-shaped piezoelectric ring array; the connecting plate is fixed on the lifting platform, and the vortex self-focusing transducer is clamped by flat-jaw pliers; The testing equipment for the vortex self-focusing transducer includes: a multi-channel signal generator, a multi-channel power amplifier, a multi-jaw mechanical chuck, a chuck connecting rod, a rotary motor, a rotary clamp and universal coupling, a rotary motor bracket, a transparent water tank, sound-absorbing material, a laser irradiation system, and an image acquisition system. The piezoelectric unit is connected to the multi-channel signal generator and the multi-channel power amplifier. The vortex self-focusing transducer is held in place by the multi-jaw mechanical chuck, with the sound wave emission direction vertically downward. The universal coupling or rotary clamp connects the chuck connecting rod to the rotating shaft of the rotary motor. The rotary motor is mounted on the rotary motor bracket. The vortex self-focusing transducer is placed in the transparent water tank and below the water surface. The bottom of the transparent water tank is lined with sound-absorbing material. A laser irradiation system is arranged on one side of the transparent water tank, and an image acquisition system is arranged on the other side.

2. The fabrication and testing tool for the vortex self-focusing transducer according to claim 1, characterized in that, The vortex self-focusing transducer is applied in a liquid environment. The vortex focusing transducer housing includes an outer wall and an inner wall spaced apart, multiple mounting platforms, a sealing plate, and a central pre-drilled hole formed by the inner wall. The height of the inner wall is lower than the height of the outer wall, and the upper surface of the inner wall is in contact with metal. The side of the outer wall facing the inner wall includes piezoelectric plate mounting platforms and metal ball mounting platforms. The side of the inner wall facing the outer wall has multiple piezoelectric plate mounting platforms. The sealing plate is disposed between the outer wall and the inner wall and is connected to both the outer wall and the inner wall. The central pre-drilled hole is used to assemble a camera. The coronal piezoelectric ring array includes a plurality of circumferentially fan-shaped concave piezoelectric elements, a central hole, and a bottom surface; the plurality of fan-shaped concave piezoelectric elements are of the same size and are distributed around the center of the coronal piezoelectric ring array, and are not electrically connected to each other; the number of fan-shaped concave piezoelectric elements is greater than or equal to 8; the inner diameter of the central hole is the same as the outer diameter of the inner wall; the coronal piezoelectric ring array is attached to the outer wall mounting base and the inner wall mounting base of the piezoelectric element; there is a gap between the coronal piezoelectric ring array and the outer wall; the bottom surface is flush with the upper surface of the inner wall; The resin sealant includes a backing and a matching layer. The backing is filled between the vortex focusing transducer housing, the sealing plate, and the coronal piezoelectric ring array. The matching layer is filled between the coronal piezoelectric ring array and the metal sphere. The matching layer is concave and has the same curvature as the piezoelectric element.

3. The fabrication and testing tool for the vortex self-focusing transducer according to claim 2, characterized in that, The outer and inner wall mounting platforms are located away from the upper surface of the sealing plate; the distance between the outer wall mounting platform of the piezoelectric sheet and the outer wall mounting platform of the metal ball is equal to the total thickness of the crown-shaped piezoelectric ring array plus the matching layer; the distance between the inner wall mounting platform and the upper surface of the inner wall is equal to the total thickness of the crown-shaped piezoelectric ring array plus the matching layer; the thickness of the matching layer is set as follows: 1.16(2n-1)λ / 4 Where n is a natural number and λ is the wavelength of sound wave propagation in the matching layer material.

4. The fabrication and testing tool for the vortex self-focusing transducer according to claim 2, characterized in that, The sealing plate is provided with wire holes; the wires of the plurality of fan-shaped concave piezoelectric array elements are exposed from the wire holes in the vortex self-focusing transducer; the wires are led out from the wire groove at the bottom of the outer wall.

5. The fabrication and testing tool for the vortex self-focusing transducer according to claim 2, characterized in that, The plurality of fan-shaped concave piezoelectric elements are formed by cutting the surface electrodes in multiple layers and multiple times using a laser cutting machine, wherein the laser cutting machine changes the focal point multiple times in the height direction.

6. The fabrication and testing tool for the vortex self-focusing transducer according to claim 1, characterized in that, The curvature of the metal ball is equal to that of the crown-shaped piezoelectric ring array. The metal ball has a screw hole, and the metal ball connecting rod and connecting plate connect the metal ball to the lifting platform.

7. The fabrication and testing tool for the vortex self-focusing transducer according to claim 1, characterized in that, The steps for fabricating a vortex self-focusing transducer using the aforementioned fabrication tool include: Multiple positive wires pass through the wire holes of the sealing plate, and each wire is individually electrically connected to each sector concave piezoelectric element of the crown piezoelectric ring array. Use quick-drying epoxy resin or glue to bond the crown piezoelectric ring array to the outer and inner wall mounting plates of the piezoelectric sheet in the vortex focusing transducer housing, and wait for the epoxy resin or glue to solidify. Seal the wire holes with quick-drying epoxy resin or glue. Wrap the metal ball with plastic film, or spray the surface of the metal ball with anti-stick agent, or wrap the outer wall of the vortex focusing transducer housing with polyimide tape; Apply an anti-sticking agent to the concave metal cylinder and insert it into the central pre-drilled hole formed by the inner wall of the vortex focusing transducer housing. Mix the epoxy resin and curing agent in a 4:1 ratio, and then place them in a vacuum machine to remove air bubbles. Fill the space between the outer and inner walls with the mixed curing agent and the de-bubbled epoxy resin until it is full; Press the metal ball firmly onto the top of the vortex self-focusing transducer and wait at least 24 hours for the epoxy resin to solidify. Remove the metal sphere and the metal cylinder at the center of the outer shell, peel off the plastic film on the metal sphere and the tape on the outer wall to complete the fabrication of the vortex self-focusing transducer.

8. The fabrication and testing tool for the vortex self-focusing transducer according to claim 1, characterized in that, The number of channels in the signal generator and power amplifier is determined based on the topological order of the vortex-focused acoustic wave. The number of channels is equal to a = m / l, where m is the number of concave sector array elements and l is the topological order of the vortex acoustic wave.

9. The fabrication and testing tool for the vortex self-focusing transducer according to claim 1, characterized in that, The steps for testing a transducer using the aforementioned testing tool include: Mount the vortex self-focusing transducer on a three-jaw or four-jaw mechanical chuck; The phase delay compensation required for each sector concave piezoelectric element of the coronal piezoelectric ring array is calculated according to the phased array delay law; a elements are allocated for each phase period in the circumferential direction, and the time delay of the nth element in each phase period is calculated as (n-1)t / a+ct, where t is the time period of the sound wave and c is a natural number. The multi-channel signal generator is first kept off, and the silent field image acquired by the image acquisition system at this time is used as the background image. Then, the multi-channel signal generator and multi-channel power amplifier are turned on, and the vortex focusing sound field is determined to be emitted normally based on the ripple results in the image. The vortex self-focusing transducer is rotated around its geometric center by a motor with a fixed rotation step size, rotating a total of 180 degrees, and recording one or more images each time it rotates. Subtract the background image from all images recorded during the rotation process to remove background noise; The image is filtered using at least one of the following methods: Gaussian, bilateral, and median. Convert the sound pressure schlieren map into a sound intensity map; The images from all angles are combined into an array, and the Radon inverse transform is performed on the data of each cross-section along the vertical direction to obtain the reconstructed three-dimensional sound field; Based on the measurement and transformation results, analyze the focal length of the vortex focusing sound field, the sound pressure distribution of the beam cross section, the sound intensity distribution of the beam cross section, and the size of the sound potential well. If there is a significant asymmetry between the left and right sound intensity fields, it indicates that the signal transmission is incorrect or the array element is damaged.

10. The fabrication and testing tool for the vortex self-focusing transducer according to claim 9, characterized in that, The specific calculation method for converting the sound pressure schlieren map into a sound intensity map includes: Within one time period or wavelength of the sound wave, take 10 or more images consecutively, overlay all images, and normalize them to obtain a sound intensity distribution map; or... Subtract 255 / 2 from the grayscale value of the sound pressure splay image and take the absolute value. Extract the maxima and their coordinates corresponding to all peaks and troughs. Use the maxima to construct an envelope diagram to obtain the sound intensity distribution map; or... The emission phase of all elements of the vortex self-focusing transducer is changed simultaneously with a phase step of 1 / 10 or smaller, while the phase difference between each element remains unchanged. The image corresponding to each phase is recorded, and all images are superimposed and normalized to obtain the sound intensity distribution map.

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