High-frequency focusing ultrasonic transducer for opto-acoustic / ultrasonic endoscopic dual-mode imaging and manufacturing method of high-frequency focusing ultrasonic transducer

Abstract

The invention discloses a high-frequency focused ultrasonic transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging and a manufacturing method of the high-frequency focused ultrasonic transducer. The transducer comprises an acoustic matching layer, a positive electrode, a wafer, a negative electrode, a backing sound absorption material, a substrate and a lead. According to the invention, the wafer is composed of a plurality of same or different units and can generate ultrasonic waves with one or more frequencies, and the wafer and the substrate are jointly processed by a self-focusing hot-pressing process, so that each unit keeps consistent curvature, and single-focus or multi-focus focusing of a sound field is realized; meanwhile, the wafer does not need to be punched, holing is carried out on the substrate, and the integrity of the wafer can be kept. The ultrasonic transducer designed by the invention has a miniaturized structure, a uniform sound wave conduction path and a stable sound field with one or more frequencies, has high durability and reliability, and can effectively improve the imaging quality.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic instruments, and particularly relates to a high-frequency focused ultrasonic transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging and a manufacturing method thereof. Background Art

[0002] The photoacoustic / ultrasonic endoscopic dual-mode imaging technology combines the advantages of optical excitation and ultrasonic detection. By using the photoacoustic signals generated after biological tissues absorb pulsed laser light and combining them with ultrasonic imaging, it realizes the synchronous imaging of high-sensitivity and high-contrast structures and functions. The endoscopic probe of this technology can penetrate deep into the body (such as the digestive tract, blood vessels). While accurately positioning the tumor boundary (photoacoustic reveals the distribution of hemoglobin), ultrasonic tomography shows the deep anatomical structure, and it is widely used in fields such as early cancer diagnosis, vascular imaging, and minimally invasive surgery.

[0003] Currently, one of the key challenges in photoacoustic / ultrasonic dual-mode imaging technology is how to design and manufacture high-performance ultrasonic transducers. In existing transducer designs, especially for high-frequency ultrasonic transducers, their performance is restricted by traditional materials and manufacturing processes in many cases. High-frequency ultrasonic waves have high spatial resolution, but at the same time face problems such as signal attenuation, low signal-to-noise ratio, and complex manufacturing processes. Especially in complex biological tissues, the design of high-frequency ultrasonic transducers needs to take into account the efficient reception and transmission of signals while reducing the interference of background noise. In addition, the requirements for transducers in photoacoustic / ultrasonic dual-mode imaging technology are not only reflected in resolution and penetration ability, but also need to consider the coordination between the transducer and the laser source and detector, as well as its adaptability in complex biological tissues. Traditional high-frequency focused ultrasonic transducers for photoacoustic endoscopic dual-mode imaging directly punch holes on the wafer. This not only may cause certain damage to the wafer during the processing, but also weakens the structural strength of the material. The hole edges are prone to become stress concentration points, and cracks may be induced under long-term high-frequency vibration, shortening the life of the wafer. Especially in high-frequency operations, this problem of structural integrity will affect the durability and reliability of the probe. Punching holes also affects the sound wave conduction path and the uniformity of the sound field. This problem is particularly significant in high-frequency applications, such as sidelobe enhancement and main lobe distortion. Therefore, the presence of holes will disrupt the continuity of sound wave propagation, resulting in attenuation or deviation of ultrasonic signals, thereby reducing the quality of photoacoustic / ultrasonic dual-mode imaging. At the same time, traditional punched-hole transducers can only generate ultrasonic waves of one frequency, and it is difficult to improve the imaging depth and resolution through multi-frequency cooperation, further restricting the versatility of photoacoustic / ultrasonic dual-mode imaging. In addition, for ultrasonic transducers with holes, in order to obtain high sensitivity, it is usually necessary to increase the size of the wafer, resulting in an increase in the size of the transducer. Summary of the Invention

[0004] The present invention provides a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging and a manufacturing method thereof, which are used to solve the technical problems that the existing ultrasound transducers affect the sound wave conduction path and the uniformity of the sound field due to structural designs such as drilling holes on the wafer, thereby reducing the photoacoustic / ultrasound imaging quality, and can only generate ultrasound of one frequency, making it difficult to improve the imaging depth and resolution through multi-frequency cooperation, further restricting the versatility of photoacoustic / ultrasound dual-mode imaging.

[0005] The present invention provides a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging, comprising: an acoustic matching layer, a positive electrode, a wafer, a negative electrode, a backing acoustic absorption material, a substrate, and leads;

[0006] The acoustic matching layer, the positive electrode, the wafer, the negative electrode, and the backing acoustic absorption material are closely arranged in sequence from top to bottom;

[0007] The positive electrode is disposed on the upper surface of the substrate;

[0008] The acoustic matching layer, the positive electrode, and the substrate are all provided with central holes;

[0009] The substrate is provided with a plurality of slotted structures surrounding the central hole; the slotted structures are for the wafer, the negative electrode, and the backing acoustic absorption material to be embedded;

[0010] The wafer is composed of a plurality of units, where each unit is the same or different in material composition and / or structure phase and / or frequency; the wafer and the substrate are jointly processed by a self-focusing hot pressing process so that each unit maintains a consistent curvature;

[0011] One end of the lead is connected to the surface of the substrate, and the other end is connected to the backing acoustic absorption material.

[0012] Further, the focusing area of the ultrasound transducer is dynamically optimized by adjusting the curvature of the substrate or the arrangement of a plurality of wafers.

[0013] Further, an adhesion layer is provided between the wafer and the positive electrode and between the wafer and the negative electrode.

[0014] Further, the operating frequency range of the high-frequency focused ultrasound transducer is one or more frequencies above 20 MHz.

[0015] Further, both the positive electrode and the negative electrode are made of gold.

[0016] Further, the wafer is composed of piezoelectric ceramics, piezoelectric crystals, and piezoelectric composite materials.

[0017] Further, the backing acoustic material is a cured viscous conductive material.

[0018] Further, the lead wire is specifically a silver strip.

[0019] Further, the adhesion layer is made of chromium.

[0020] The present invention also provides a manufacturing method for a high-frequency focused ultrasound transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging. The method includes:

[0021] Obtain the geometric parameters of each wafer, determine the processing parameters of each wafer based on the target center frequency according to the geometric parameters, and perform microstructural processing on the surface of the wafer based on the processing parameters through laser cutting technology;

[0022] Sputter an adhesion layer and a negative electrode on the lower surface of each wafer in sequence through a magnetron sputtering device;

[0023] Pour the backing acoustic material at the negative electrode on the lower surface of each wafer to a specified thickness;

[0024] Place the fabricated wafer, the negative electrode, and the backing acoustic material in the corresponding slotted structure of the substrate, and fix them with epoxy resin;

[0025] Process the substrate and all the wafers through a self-focusing hot pressing process to make the curvatures of the substrate and all the wafers consistent;

[0026] Sputter an adhesion layer and a positive electrode on the upper surface of the substrate in sequence through a magnetron sputtering device; wherein, the substrate and the crystal are both connected to the positive electrode;

[0027] Connect all the backing acoustic materials through lead wires, and connect the other ends of the lead wires to the upper surface of the substrate;

[0028] Design an acoustic matching layer according to a preset thickness, and bond the acoustic matching layer to the positive electrode.

[0029] It can be seen from the above technical solutions that the present invention has the following advantages:

[0030] The present invention provides a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging and a manufacturing method thereof. The high-frequency focused ultrasound transducer includes: an acoustic matching layer, a positive electrode, a wafer, a negative electrode, a backing acoustic absorption material, a substrate, and a lead wire; the acoustic matching layer, the positive electrode, the wafer, the negative electrode, and the backing acoustic absorption material are tightly arranged in sequence from top to bottom; the positive electrode is disposed on the upper surface of the substrate; the acoustic matching layer, the positive electrode, and the substrate are all provided with a central hole; the substrate is provided with a plurality of slotted structures surrounding the central hole; the slotted structures are for embedding the wafer, the negative electrode, and the backing acoustic absorption material; the wafer is composed of a plurality of units, and at least two of the units are different in material composition and / or phase and / or frequency. The wafer and the substrate are jointly processed by a self-focusing hot pressing process to make the units maintain a consistent curvature; one end of the lead wire is connected to the surface of the substrate, and the other end is connected to the backing acoustic absorption material.

[0031] In the present invention, the wafer and the substrate are jointly processed by a self-focusing hot pressing process to make the units maintain a consistent curvature. For the same wafer, the focal points are at the same position after the self-focusing hot pressing process. For different wafer hot pressing processes, the focal point positions are not at the same point but at multiple focal points on the axis. Thus, single-focus or multi-focus focusing of the sound field can be achieved, forming an acousto-optic excitation and reception mode coaxial with the optical field; at the same time, there is no need to punch holes in the wafer, but holes are opened in the substrate, which can maintain the integrity of the wafer and avoid diffraction of sound waves at the holes, resulting in energy diffusion in an unexpected direction and forming side lobes; moreover, the wafer can be composed of a plurality of identical or different units, which can generate ultrasound of one or more frequencies, and multi-frequency cooperation can improve the imaging depth and resolution, further enhancing the versatility of photoacoustic / ultrasound dual-mode imaging; the high-frequency focused ultrasound transducer provided by the present invention has a uniform sound wave conduction path and a stable sound field, and at the same time has high durability and reliability, can effectively improve the imaging quality, and thus solves the technical problems that the structural design such as punching holes in the wafer of the existing ultrasound transducer affects the sound wave conduction path and the uniformity of the sound field, thereby reducing the photoacoustic imaging quality, and can only generate ultrasound of one frequency, and it is difficult to improve the imaging depth and resolution through multi-frequency cooperation, further limiting the versatility of photoacoustic / ultrasound dual-mode imaging. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1Schematic structural diagram of a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging with a center frequency of 30 MHz provided by this application;

[0034] Figure 2 Schematic cross-sectional diagram of a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging with a center frequency of 30 MHz provided by this application;

[0035] Figure 3 Schematic structural diagram of a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging with dual frequencies of 20 MHz and 30 MHz provided by this application;

[0036] Figure 4 Schematic cross-sectional diagram of a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging with dual frequencies of 20 MHz and 30 MHz provided by this application;

[0037] Figure 5 Flowchart of the steps of a manufacturing method of a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging provided by this application;

[0038] Among them, the reference numerals are: acoustic matching layer 1, first-layer acoustic matching structure 11, second-layer acoustic matching structure 12, 20 MHz acoustic matching structure 13, positive electrode 2, wafer 3, 20 MHz wafer 31, 30 MHz wafer 32, negative electrode 4, backing acoustic absorption material 5, substrate 6, and lead 7. Detailed implementation manners

[0039] The embodiments of the present invention provide a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging and a manufacturing method thereof, which are used to solve the technical problems that the structural design such as punching holes in the wafer of the existing ultrasound transducer affects the sound wave conduction path and the uniformity of the sound field, thereby reducing the photoacoustic imaging quality, and only one frequency of ultrasound can be generated, making it difficult to improve the imaging depth and resolution through multi-frequency cooperation, further restricting the versatility of photoacoustic / ultrasound dual-mode imaging.

[0040] To make the invention purpose, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0041] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0042] Unless otherwise clearly specified and defined, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] Please refer to Figures 1-4 , this application provides a high-frequency focused ultrasound transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging, including: an acoustic matching layer 1, a positive electrode 2, a wafer 3, a negative electrode 4, a backing acoustic absorption material 5, a substrate 6, and a lead 7;

[0044] The acoustic matching layer 1, the positive electrode 2, the wafer 3, the negative electrode 4, and the backing acoustic absorption material 5 are arranged closely in sequence from top to bottom;

[0045] The positive electrode 2 is arranged on the upper surface of the substrate 6; the acoustic matching layer 1, the positive electrode 2, and the substrate 6 are all provided with central holes; the substrate 6 is provided with a plurality of slotted structures surrounding the central hole; the slotted structures are for the wafer 3, the negative electrode 4, and the backing acoustic absorption material 5 to be embedded; the wafer 3 is composed of a plurality of units, and the wafer 3 and the substrate 6 are jointly processed by a self-focusing hot pressing process so that each unit maintains a consistent curvature; one end of the lead 7 is connected to the surface of the substrate 6, and the other end is connected to the backing acoustic absorption material 5.

[0046] It should be noted that the operating frequency of the high-frequency focused ultrasound transducer provided by the present invention is one or more frequencies above 20 MHz. Please refer to Figure 1 and Figure 2 , this embodiment provides a high-frequency focused ultrasound transducer structure for photoacoustic / ultrasonic endoscopic dual-mode imaging with a central frequency of 30 MHz; please refer to Figure 3 and Figure 4 , this embodiment provides a high-frequency focused ultrasound transducer structure for photoacoustic / ultrasonic endoscopic dual-mode imaging with dual frequencies of 30 MHz and 20 MHz.

[0047] In the present invention, an acoustic matching layer 1, a positive electrode 2, a wafer 3, a negative electrode 4, a backing acoustic absorption material 5, and a lead 7 are sequentially and closely arranged to form an acoustic coupling system, which can achieve single-focus or multi-focus focusing of the sound field and form an acousto-optic excitation and reception mode coaxial with the light field.

[0048] Specifically, the wafer 3 is composed of multiple units, and each unit is the same or different in terms of material composition and / or phase and / or frequency; during manufacturing, a self-focusing hot pressing process can be carried out jointly with the substrate 6 to ensure that each unit maintains a consistent curvature, and the consistent curvature of multiple identical or different units can be simply achieved, thereby optimizing the focusing performance of the transducer; the slotted structure is used to accurately position the wafer array formed by multiple wafers 3; the substrate 6 is provided with a central hole at the center of the formed wafer array to allow the laser beam to be accurately incident.

[0049] Among them, the acoustic matching layer 1 is used to effectively transfer the ultrasonic waves formed on the surface to be measured to the wafer 3 and improve the transmission efficiency of the ultrasonic waves to optimize the imaging signal-to-noise ratio; while the backing acoustic absorption material 5 is used to suppress the echo period on the lower surface of the wafer 3, reduce unnecessary reflections, and improve the imaging clarity.

[0050] In addition, connecting the lead 7 to the substrate 6 can restore its connection function by reconnecting to the substrate 6 when the lead 7 is damaged, because the substrate 6 has a large contact area, while the area of the wafer 3 is small. If directly connected to the wafer 3, it is difficult to reconnect once the lead 7 is damaged, thereby improving the convenience of maintenance and the reliability of the design. It should be noted that the acoustic-optic matching layer 1 is also connected with a lead 7.

[0051] When the high-frequency focused ultrasound transducer is working, in the photoacoustic imaging mode, the laser emitted by the laser source is accurately guided through the central hole to the surface of the tissue to be measured; the laser forms light absorption in the tissue to be measured, causing the local temperature to rise instantaneously, thereby causing thermal expansion and contraction of the tissue to be measured, and exciting ultrasonic signals; the acoustic matching layer 1 can improve the acoustic coupling between the wafer 3 and the tissue to be measured, ensuring that the ultrasonic signals are effectively transmitted from the target tissue to the wafer 3; the wafer 3 receives the ultrasonic signals generated by the photoacoustic effect, converts the mechanical vibration into an electrical signal and transmits it to the backing acoustic absorption material 5; the backing acoustic absorption material 5 transmits the electrical signal to the photoacoustic imaging system through the lead wire 7; the electrical signal is amplified and filtered by the signal processing system of the detector, etc., to generate high-resolution photoacoustic imaging data. In the ultrasonic imaging mode, the ultrasonic imaging system applies high-frequency electrical pulses (frequency range 20 - 50 MHz) to the positive and negative electrodes through the lead wire 7, exciting the wafer 3 to generate the inverse piezoelectric effect, converting electrical energy into mechanical vibration. Multiple piezoelectric units of the wafer 3 vibrate synchronously under the drive of the high-frequency electrical pulses, emitting a focused ultrasonic beam. The acoustic matching layer 1 reduces the reflection loss of the sound wave at the transducer-tissue interface through the acoustic impedance gradient design, ensuring efficient coupling of the ultrasonic wave to the tissue to be measured. When the emitted ultrasonic wave propagates in the tissue, it encounters an interface with different acoustic impedance (such as the blood vessel wall, tumor boundary) and reflects, forming an echo signal. The echo signal propagates back to the transducer, and the wafer 3 converts the mechanical vibration into an electrical signal through the direct piezoelectric effect. The backing acoustic absorption material 5 absorbs the clutter radiated by the wafer in the backward direction, suppresses noise interference, and improves the signal-to-noise ratio. The electrical signal is transmitted to the signal processing module of the ultrasonic imaging system through the lead wire 7. The electrical signal is amplified and filtered by the signal processing system of the detector, etc., to generate high-resolution ultrasonic imaging data.

[0052] In this embodiment, the wafer 3 and the substrate 6 are jointly processed by the self-focusing hot pressing process so that each unit maintains a consistent curvature, which can achieve geometric focusing of the sound field and form an acousto-optic excitation and reception mode coaxial with the light field; at the same time, there is no need to punch holes in the wafer 3, but holes are opened in the substrate 6, which can maintain the integrity of the wafer 3 and avoid diffraction of the sound wave at the hole, resulting in the diffusion of energy in an unexpected direction and forming side lobes; and the wafer 3 can be composed of multiple identical or different units, which can generate ultrasonic waves of one or more frequencies, and the multi-frequency cooperation can improve the imaging depth and resolution, further enhancing the versatility of the photoacoustic / ultrasonic dual-mode imaging.

[0053] It should be noted that the ultrasonic transducer can be compatible with existing photoacoustic / ultrasonic dual-mode imaging systems, has optimal confocal imaging performance, supports precise docking with laser sources and detectors, forms an efficient photoacoustic confocal imaging system, and achieves imaging effects with high signal-to-noise ratio and high resolution. Through photoacoustic / ultrasonic endoscopic dual-mode imaging, the ultrasonic transducer can achieve high-resolution and precise imaging in early cancer diagnosis, minimally invasive surgery, and other biomedical applications, showing broad clinical application prospects.

[0054] Furthermore, the focusing area of the ultrasonic transducer is dynamically optimized by adjusting the curvature of the substrate 6 or the arrangement of multiple wafers 3.

[0055] It should be noted that the focusing area of the ultrasonic transducer refers to the area where sound waves converge within a specific region of the ultrasonic transducer during propagation, forming an energy-concentrated area; for the ultrasonic transducer provided in this solution, the focusing area can be dynamically optimized by adjusting the curvature of the substrate 6 or the arrangement of the wafer 3 array to improve the accurate detection of sound waves.

[0056] Furthermore, adhesive layers are provided between the wafer 3 and the positive electrode 2 and between the wafer 3 and the negative electrode 4. Among them, the adhesive layer is used to more firmly bond the wafer 3 and the electrodes on its surface to ensure the working stability of the electrodes.

[0057] Furthermore, both the positive electrode 2 and the negative electrode 4 are made of gold. Among them, using gold as the conductive material of the electrode enables the conductive layer to have excellent electrical conductivity and antioxidant ability, which can significantly improve the electrical performance and environmental tolerance of the transducer.

[0058] Furthermore, the wafer 3 is made of piezoelectric ceramics, piezoelectric crystals, and piezoelectric composite materials.

[0059] Furthermore, the backing acoustic absorption material 5 is a curable viscous conductive material, specifically conductive silver paste E-solder3022.

[0060] Among them, the conductive silver paste E-solder 3022 is in liquid form and has conductivity. When it is poured, excess silver paste will be generated on both sides. After it is cured, the excess silver paste can be cut by a tool to isolate the conductivity, and the cured conductive silver paste has an adsorption effect on the wafer 3.

[0061] Furthermore, the lead wire 7 is specifically a silver strip.

[0062] Furthermore, the adhesive layer is made of chromium. Among them, using chromium as the material of the adhesive layer can achieve a firm connection with the surface of the wafer 3 and ensure the long-term stability of the electrodes.

[0063] The high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging provided by the present invention has the following advantages:

[0064] 1. The present invention can avoid stress defects caused by punching holes in the wafer, reduce the yield rate, thereby optimizing the conduction of acoustic waves and photoacoustic signals, and ensuring the stability and clarity of the imaging quality.

[0065] 2. The present invention uses a hot pressing process to jointly fabricate the wafer and the substrate, and can achieve consistent curvature of multiple wafers to improve the focusing effect.

[0066] 3. By using wafers with different main frequencies, a multi-frequency ultrasound endoscope probe with a smaller diameter can be simply manufactured, which can transmit and receive multiple ultrasound main frequencies to obtain more comprehensive imaging information, while maintaining the miniaturized design of the probe for easy in-vivo examination.

[0067] 4. The acoustic matching layer, positive electrode, wafer, negative electrode, backing acoustic absorption material, and lead are sequentially and tightly arranged to form an acoustic coupling system, which can achieve single-focus or multi-focus focusing of the sound field, and form an acoustic-optic excitation and reception mode coaxial with the light field.

[0068] Please refer to Figure 5 , the present invention also provides a manufacturing method for a high-frequency focused ultrasound transducer for photoacoustic / ultrasound endoscopic dual-mode imaging, and the method includes:

[0069] Step 101: Obtain the geometric parameters of each wafer 3, determine the processing parameters of each wafer 3 based on the target center frequency according to the geometric parameters, and perform microstructure processing on the surface of the wafer 3 based on the processing parameters by laser cutting technology;

[0070] It can be understood that the laser cutting technology is a non-contact processing method and will not cause mechanical stress or damage to the wafer 3; at the same time, the corresponding slit size is designed according to different preset center frequencies to process the wafer 3, so that the wafer 3 can be applied to different application scenarios to meet the acoustic characteristic design of the target center frequency.

[0071] Step 102: Sputter an adhesion layer and a negative electrode 4 on the lower surface of each wafer 3 in sequence through a magnetron sputtering device;

[0072] Step 103: Pour the backing acoustic absorption material 5 at the negative electrode 4 on the lower surface of each wafer 3 to a specified thickness; wherein, the backing acoustic absorption material 5 is used to suppress the echo period on the lower surface of the wafer 3, reduce unnecessary reflections, and improve the imaging clarity;

[0073] Step 104: Place the fabricated wafer 3, negative electrode 4, and backing acoustic absorption material 5 in the corresponding grooved structure of the substrate 6, and fix them with epoxy resin;

[0074] It is understandable that the structure of the substrate 6 is designed according to the acoustic characteristics of different target center frequencies, and corresponding slotted structures are formed in the substrate 6 to place the crystal, the negative electrode 4, and the backing sound-absorbing material 5; meanwhile, a central hole is also formed at the center of the substrate 6 for guiding the incidence of the laser.

[0075] Step 105, process the substrate 6 and all the wafers 3 through a self-focusing hot pressing process to make the curvatures of the substrate 6 and all the wafers 3 consistent;

[0076] More specifically, a small steel ball can be used to press the surfaces of the substrate 6 and all the wafers 3. During the processing, a high-precision control system is used to adjust the pressing force and displacement to ensure the uniformity and consistency of the surface curvatures of the substrate 6 and the wafers 3, so that they maintain the same focus or coaxial foci.

[0077] Step 106, sputter an adhesion layer and a positive electrode 2 on the upper surface of the substrate 6 in sequence through a magnetron sputtering device to realize the connection between the wafer 3 and the substrate 6 and the positive electrode 2; among them, both the substrate and the crystal are connected to the positive electrode.

[0078] Step 107, connect all the backing sound-absorbing materials 5 through the lead 7, and connect the other end of the lead 7 to the upper surface of the substrate 6;

[0079] It should be noted that connecting the backing sound-absorbing material 5 and the substrate 6 through the lead 7 can ensure the reliability of the electrical connection and avoid signal interference.

[0080] Step 108, design the acoustic matching layer 1 according to a preset thickness and bond the acoustic matching layer 1 to the positive electrode 2. Among them, the acoustic matching layer 1 is used to effectively transmit the ultrasonic waves formed on the surface to be measured to the wafer 3 and improve the transmission efficiency of the ultrasonic waves to optimize the imaging signal-to-noise ratio.

[0081] It should be noted that the high-frequency focused ultrasound transducer designed in the present invention is mainly composed of components such as a substrate 6, a lead 7, a wafer 3, an acoustic matching layer 1, a backing sound-absorbing material 5, a positive electrode 2, and a negative electrode 4; among them, the designed ultrasound transducer has a uniform acoustic wave conduction path and a stable sound field, and at the same time has high durability and reliability, and can effectively improve the imaging quality; among them, during the manufacturing process, operations such as drilling holes in the wafer 3 are not required, and the wafer 3 and the substrate 6 are jointly processed through a self-focusing hot pressing process to make each unit have a consistent curvature, and acoustic-optical excitation and reception modes coaxial with the optical field can be formed.

[0082] Among them, the working principle of the high-frequency focused ultrasound transducer provided by the present invention is as follows: In the photoacoustic imaging modality, a laser is guided into the tissue to be measured through the central hole of the substrate 6; then, the laser excites the photoacoustic effect in the tissue to be measured and generates ultrasonic signals; the ultrasonic signals are received by the wafer 3 through the acoustic matching layer 1, and the wafer 3 converts the ultrasonic signals into electrical signals and transmits the electrical signals to the backing sound-absorbing material 5; the backing sound-absorbing material 5 transmits the electrical signals to the photoacoustic imaging system connected to the substrate 6 through the lead wire 7, and finally the photoacoustic imaging system generates the photoacoustic imaging data corresponding to the tissue to be measured. In the ultrasonic imaging modality, the ultrasonic imaging system synchronously vibrates through multiple piezoelectric units of the wafer 3 under the drive of high-frequency electrical pulses to emit a focused ultrasonic beam. The acoustic matching layer 1 reduces the reflection loss of sound waves at the transducer-tissue interface through the design of the acoustic impedance gradient. The echo signal propagates back to the transducer. The backing sound-absorbing material 5 absorbs the clutter radiated backward by the wafer. The electrical signal is transmitted to the signal processing module of the ultrasonic imaging system through the lead wire 7 to generate high-resolution ultrasonic imaging data.

[0083] The following further describes the manufacturing method of a high-frequency focused ultrasound transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging with central frequencies of 30 MHz and 20 MHz.

[0084] Example 1

[0085] This Example 1 is a high-frequency focused ultrasound transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging with a central frequency of 30 MHz, which is used for fine observation of superficial tissue structures, such as the vascular wall layer and micro-lesion areas, commonly found in ophthalmology, dermatology, and biomedical research. Please refer to Figure 1 and Figure 2 ; In this embodiment, the wafer 3 used is specifically a 30 MHz wafer, the material is PMN-PT / epoxy resin 1-3 composite material, and the size is 0.8×0.8 mm; the size of the substrate 6 used is 1.5×3 mm, the aperture of the slotted structure is 1×1 mm, and the diameter of the middle hole is 0.3 mm; the acoustic matching layer 1 used is specifically a 30 MHz acoustic-optical matching structure, specifically adopting a double-layer structure. The first acoustic matching structure 11 is 1um alumina and 301 epoxy resin, and the second acoustic matching structure 12 selects 301 epoxy resin; the backing sound-absorbing material 5 is conductive silver paste E-solder 3022; the electrodes used are a double layer of chromium / gold, and the lead wire 7 used is a silver strip.

[0086] The manufacturing process of the high-frequency focused ultrasound transducer in this Example 1 is as follows:

[0087] (1) Wafer manufacturing

[0088] In this embodiment, the upper surface of the 30 MHz wafer 32 is micro-structured by laser cutting technology, and its geometric parameters are precisely adjusted to achieve the acoustic characteristic design of the selected 30 MHz center frequency. The designed slit size meets , where is the polymer shear rate, is the thickness vibration frequency. Then, the lower surface of the wafer 3 is ground to a specified thickness t that meets , is the piezoelectric column width. Finally, a slit size of 6.5 microns and a thickness of 40 microns are obtained.

[0089] (2) Depositing a negative electrode

[0090] The lower surface of the 30 MHz wafer 32 is sputtered with a chromium / gold electrode using a magnetron sputtering device. Among them, the chromium layer serves as an adhesion layer, firmly bonding to the surface of the 30 MHz wafer 32 to ensure the long-term stability of the electrode; while the gold layer serves as the conductive layer of the negative electrode 4. Gold has excellent electrical conductivity and antioxidant ability, which can significantly improve the electrical performance and environmental tolerance of the transducer.

[0091] (3) Filling the backing sound-absorbing material

[0092] The conductive silver paste E-solder 3022 is poured onto the lower surface electrode of the wafer 3 to a specified thickness of 0.65 mm, and then it is placed in a constant-temperature oven for curing treatment. Among them, the curing temperature and time are 45 °C and 24 h respectively to ensure that the silver paste is fully cured, forming an adsorption layer with high electrical conductivity and mechanical strength.

[0093] (4) Placing in the substrate

[0094] The two fabricated 30 MHz wafers 32, the negative electrode 4, and the backing sound-absorbing material 5 are placed in the slotted structure around the substrate 6. Then, epoxy resin is poured around the hole ends of the slotted structure of the 30 MHz wafer 32 and the substrate 6, and then it is cured in a 45 °C constant-temperature oven for 12 h. After curing, the excess epoxy resin is ground off using a tool.

[0095] (5) Hot pressing

[0096] Through the self-focusing hot pressing process, the small steel ball is pressed onto the entire surface of the substrate 6 and all the 30 MHz wafers 32, so that the curvatures of the substrate 6 and all the 30 MHz wafers 32 are kept consistent, forming an accurate specified curvature. At the same time, during the processing, the pressing force and displacement can be adjusted using a high-precision control system, thereby ensuring the uniformity and consistency of the surface curvatures of the substrate 6 and all the 30 MHz wafers 32.

[0097] (6) Depositing a positive electrode

[0098] Sputter a chromium / gold electrode on the upper surface of the substrate 6 using a magnetron sputtering device.

[0099] (7)Lead connection

[0100] Use a lead 7 to connect the backing acoustic material 5, and then connect the other end of the lead 7 to the upper surface of the substrate 6 to ensure the reliability of the electrical connection and avoid signal interference.

[0101] (8)Bonding of the acoustic matching layer

[0102] Design the thickness of the acoustic matching layer 1 according to 1 / 4 of the designed target wavelength of the ultrasonic transducer. Among them, the acoustic matching layer 1 consists of two layers. The first acoustic matching structure 11 is 1um alumina and 301 epoxy resin, and the mixing ratio of the two is 3:2, with a thickness of 22 microns; the second acoustic matching structure 12 uses 301 epoxy resin, with a thickness of 26 microns. After production, bond the acoustic matching layer 1 on the upper surface of the positive electrode 2.

[0103] Example 2

[0104] This Example 2 is a high-frequency focused ultrasonic transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging with center frequencies of 20MHz and 30MHZ, used for imaging of medium-depth and superficial tissues, taking into account both resolution and penetration ability, and widely used in clinical diagnosis of larger cavities, such as monitoring of esophageal, tracheal, and vascular lesions, to meet the detection requirements of deeper levels. Please refer to Figure 3 and Figure 4 ; In this example, the material of the wafer 3 used is PMN-PT / epoxy resin 1-3 composite material. In particular, in order to meet the dual-frequency requirements, this example selects a 20MHz wafer 31 and a 30MHz wafer 32; among them, the size of the 20MHz wafer 31 is 1.5×1.5mm, and the size of the 30MHz wafer 32 is 0.8×0.8mm; the size of the substrate 6 used is 4×2 mm, the material is PZT, the aperture of the slotted structure is 1×1mm and 1.6×1.6mm, and the diameter of the central hole is 0.3mm; the acoustic matching layer 1 used includes a 20MHz acoustic matching structure and a 30MHz acoustic matching structure. Among them, the 20MHz acoustic matching structure 13 uses a single-layer epoxy resin structure, while the 30MHz acoustic matching structure uses a double-layer structure. The first acousto-optic matching structure 11 is 1um alumina and 301 epoxy resin, and the second acousto-optic matching structure 12 uses 301 epoxy resin; the backing acoustic material 5 used is conductive silver paste E-solder 3022; the electrode used is a double layer of chromium / gold, and the lead 7 used is a silver strip.

[0105] The manufacturing process of the high-frequency focused ultrasonic transducer in this Example 2 is as follows:

[0106] (1)Wafer fabrication

[0107] In this embodiment, the upper surface of the wafer 31 is microstructurally processed by laser cutting technology, and its geometric parameters are precisely adjusted to achieve the acoustic characteristic design of the selected center frequencies of 20 MHz and 30 MHz. The designed slit size satisfies , where is the polymer shear rate, is the thickness vibration frequency. Then, the lower surface of the wafer 3 is ground to a specified thickness t that satisfies , is the piezoelectric column width. For the wafer 31 with a center frequency of 20 MHz, the final slit size is 10 microns and the thickness is 60 microns. For the wafer 32 with a center frequency of 30 MHz, the final slit size is 6.5 microns and the thickness is 40 microns.

[0108] (2) Coating the negative electrode

[0109] The lower surfaces of the 20 MHz wafer 31 and the 30 MHz wafer 32 are sputtered with chromium / gold electrodes using a magnetron sputtering device. Among them, the chromium layer serves as an adhesion layer, firmly bonding to the surface of the piezoelectric wafer to ensure the long-term stability of the electrode; while the gold layer serves as the conductive layer of the negative electrode 4. Gold has excellent electrical conductivity and antioxidant ability, which can significantly improve the electrical performance and environmental tolerance of the transducer.

[0110] (3) Infusing the backing acoustic material

[0111] The conductive silver paste E-solder 3022 is infused into the lower surface electrodes of the 20 MHz wafer 31 and the 30 MHz wafer 32 to a specified thickness of 0.5 mm, and then it is placed in a constant-temperature oven for curing. Among them, the curing temperature and time are set to 45 °C and 24 h respectively to ensure that the silver paste is fully cured to form an adsorption layer with high conductivity and mechanical strength.

[0112] (4) Placing into a hollow mold

[0113] The fabricated 20 MHz wafer 31, 30 MHz wafer 32, negative electrode 4, and backing acoustic material 5 are placed into the slotted structure around the substrate 6. Then, epoxy resin is infused around the hole ends of the slotted structure between the wafer 3 and the substrate 6, and then it is cured in a 45 °C constant-temperature oven for 12 h. After curing, the excess epoxy resin is ground off using a tool.

[0114] (5) Hot pressing

[0115] Through the self-focusing hot pressing process, small steel balls are pressed onto the entire surface of the substrate 6 and all the wafers 3 to keep the curvature of the substrate 6 and all the wafers 3 consistent, forming an accurate specified curvature. During the processing, a high-precision control system can be used to adjust the pressing force and displacement, thereby ensuring the uniformity and consistency of the curvature of the mold surface.

[0116] (6)Plating the positive electrode

[0117] The upper surface of the substrate 6 is sputtered with a chromium / gold electrode using a magnetron sputtering device.

[0118] (7)Lead access

[0119] A lead 7 is used to connect the backing sound-absorbing material 5, and then the other end of the lead 7 is connected to the upper surface of the substrate 6, thereby ensuring the reliability of the electrical connection and avoiding signal interference.

[0120] (8)Bonding of the acoustic matching layer

[0121] The thickness of the acoustic matching layer 1 is designed according to 1 / 4 of the target wavelength of the ultrasonic transducer design. Among them, the 20MHz acoustic matching structure 13 is composed of a single-layer structure of epoxy resin with a thickness of 33 microns; the 30MHZ acoustic matching structure is composed of two layers. The first acoustic matching structure 11 is 1um alumina and 301 epoxy resin, and the mixing ratio of the two is 3:2, with a thickness of 22 microns; the second acoustic matching structure 12 selects 301 epoxy resin with a thickness of 26 microns. After production, the acoustic matching layer 1 is bonded to the upper surface of the positive electrode 2. After production, the acoustic matching layer 1 is bonded to the upper surface of the positive electrode 2.

[0122] The manufacturing method of the high-frequency focused ultrasonic transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging provided by the present invention has the following advantages:

[0123] 1. When manufacturing the ultrasonic transducer of the present invention, there is no need to drill holes in the wafer, which can maintain the integrity of the wafer, ensure its stability in high-frequency operation, and reduce the risk of failure; in addition, this design can optimize the conduction of sound waves and photoacoustic signals, ensuring the stability and clarity of the imaging quality.

[0124] 2. By pressing multiple wafers and substrates simultaneously with the same steel ball, the curvature of the substrate and all the wafers can be kept consistent, so as to ensure that multiple wafers can work synchronously when receiving ultrasonic signals, thereby forming a unified focused sound beam, which can achieve geometric focusing of the sound field and form an acoustic-optic excitation and reception mode coaxial with the light field.

[0125] 3. Connect the substrate and the backing sound-absorbing material through leads; then when the leads are damaged, the connection function can be restored by reconnecting the leads to the substrate; compared with the existing connection achieved through wafers, the use of the substrate for connection in the present invention provides convenience and reliability for subsequent maintenance; since the substrate has a larger contact area while the wafer area is smaller, if directly connected to the wafer, it is impossible to reconnect once the leads are damaged.

[0126] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-frequency focused ultrasound transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging, characterized in that, Comprising: an acoustic matching layer, a positive electrode, a wafer, a negative electrode, a backing acoustic absorption material, a substrate, and a lead; the acoustic matching layer, the positive electrode, the wafer, the negative electrode, and the backing acoustic absorption material are sequentially and closely arranged from top to bottom; the positive electrode is disposed on the upper surface of the substrate; the acoustic matching layer, the positive electrode, and the substrate are all provided with central holes; the substrate is provided with a plurality of grooved structures surrounding the central hole; the grooved structures are for the wafer, the negative electrode, and the backing acoustic absorption material to be embedded; the wafer is composed of a plurality of units, where each unit is the same or different in material composition and / or phase and / or frequency; the wafer and the substrate are jointly processed by a self-focusing hot pressing process so that each unit maintains a consistent curvature; one end of the lead is connected to the surface of the substrate, and the other end thereof is connected to the backing acoustic absorption material.

2. The high-frequency focused ultrasound transducer according to claim 1, wherein The focusing area of the ultrasonic transducer is dynamically optimized by adjusting the curvature of the substrate or the arrangement of a plurality of wafers.

3. The high-frequency focused ultrasound transducer according to claim 1, characterized in that, An adhesion layer is provided between the wafer and the positive electrode and between the wafer and the negative electrode.

4. The high-frequency focused ultrasound transducer according to claim 1, characterized in that, The operating frequency range of the high-frequency focused ultrasonic transducer is one or more frequencies above 20 MHz.

5. The high-frequency focused ultrasound transducer according to claim 1, wherein Both the positive electrode and the negative electrode are made of gold.

6. The high-frequency focused ultrasound transducer according to claim 1, wherein The wafer is made of piezoelectric ceramics, piezoelectric crystals, and piezoelectric composite materials.

7. The high-frequency focused ultrasound transducer according to claim 1, wherein The backing acoustic absorption material is a cured viscous conductive material.

8. The high-frequency focused ultrasound transducer according to claim 1, characterized in that The lead is specifically a silver strip.

9. The high-frequency focused ultrasound transducer according to claim 3, wherein The adhesion layer is made of chromium.

10. A manufacturing method of a high-frequency focused ultrasound transducer for photoacoustic / ultrasonic endoscopic dual-mode imaging, characterized in that, The method includes: obtaining the geometric parameters of each wafer, determining the processing parameters of each wafer based on the geometric parameters according to the target center frequency, and performing microstructure processing on the surface of the wafer based on the processing parameters by laser cutting technology; sequentially sputtering an adhesion layer and a negative electrode on the lower surface of each wafer by a magnetron sputtering device; pouring a backing acoustic absorption material at the negative electrode on the lower surface of each wafer to a specified thickness; placing the fabricated wafer, negative electrode, and backing acoustic absorption material in the corresponding grooved structure of the substrate and fixing them with epoxy resin; processing the substrate and all the wafers by a self-focusing hot pressing process to make the curvature of the substrate and all the wafers consistent; sequentially sputtering an adhesion layer and a positive electrode on the upper surface of the substrate by a magnetron sputtering device; wherein, both the substrate and the crystal are connected to the positive electrode; connecting all the backing acoustic absorption materials by leads and connecting the other end of the leads to the upper surface of the substrate; designing an acoustic matching layer according to a preset thickness and bonding the acoustic matching layer to the positive electrode.

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