High-performance transparent piezoelectric composite material, array transducer and preparation method thereof

Abstract

The application provides a high-performance transparent piezoelectric composite material, an array transducer and a preparation method thereof, and comprises the following steps: step 1, performing optical-grade polishing treatment on a piezoelectric material to obtain a polished piezoelectric material; step 2, preparing electrodes on the upper and lower surfaces of the polished piezoelectric material to obtain a piezoelectric material provided with electrodes; step 3, performing transparent treatment on the piezoelectric material provided with electrodes to obtain a transparent piezoelectric layer; step 4, arranging one surface of the transparent piezoelectric layer on a substrate, and performing optical-grade polishing treatment on the other surface of the transparent piezoelectric layer until the designed thickness is reached to obtain a polished transparent piezoelectric layer; and step 5, cutting the polished surface of the polished transparent piezoelectric layer according to a preset matrix structure to obtain a high-performance transparent array piezoelectric composite material; and the application can greatly improve the performance of the transparent transducer.

Description

Technical Field

[0001] This invention belongs to the field of ultrasonic transducers, specifically relating to a high-performance transparent piezoelectric composite material, an array transducer, and its preparation method. Background Technology

[0002] Ultrasonic transducers and ultrasound imaging technology are widely used in biomedical and clinical medicine due to their simple equipment, low cost, safety, lack of radiation, and real-time imaging capabilities. Ultrasonic transducers are mainly divided into single-element ultrasound transducers and array ultrasound transducers. Array transducers can use electronic focusing, or a combination of electronic and physical focusing, to achieve single-point or multi-point focusing with adjustable focal positions. Through electronic scanning, they can achieve real-time, rapid, and high-resolution imaging. Therefore, array transducers have significant advantages in practical applications such as ultrasound imaging. In clinical diagnosis, array transducer probes can determine the location, size, and shape of organs, determine the extent of lesions, provide anatomical diagrams of glandular tissues, and differentiate between normal and abnormal fetuses. They are widely used in ophthalmology, obstetrics and gynecology, and the cardiovascular, digestive, and urinary systems. However, the principle of ultrasound imaging dictates that its imaging contrast originates only from the differences in the physical properties of the object being probed and cannot directly reflect the physiological state of tissues or organs. To overcome the inherent limitations of ultrasound imaging, researchers have combined optical imaging techniques (photoacoustic imaging, laser confocal microscopy, two-photon excitation microscopy, and weak optical coherence tomography, etc.) with traditional ultrasound imaging, developing ultrasound-optical multimodal imaging. This approach significantly improves image resolution and contrast. Ultrasound-optical multimodal imaging not only obtains high-quality morphological information about tissues but also provides metabolic information such as blood oxygen saturation, thus reflecting the physiological state of the tissues. It holds significant promise for applications in early cancer diagnosis, cardiovascular diseases, dermatology, and brain imaging.

[0003] Traditional array ultrasonic transducers typically use high-performance piezoelectric materials, such as lead zirconate titanate (PZT) series piezoelectric ceramics and relaxor ferroelectric single crystal materials. These materials have high dielectric constant, piezoelectric coefficient, and electromechanical coupling coefficient. Combined with a double-layer matching layer design and a high-attenuation backing layer design, they can achieve high bandwidth and sensitivity.

[0004] However, the piezoelectric materials, backing materials, and matching layer materials used in traditional array transducers are usually opaque in the visible light band. This results in the overall structure of traditional array transducers being opaque, requiring complex structural designs to introduce an optical path system into the traditional array ultrasonic transducer probe (for example, by mechanically binding optical fibers to allow the laser to enter the target from the side of the transducer) to meet the requirements of ultrasonic-photoacoustic dual-modal imaging. This not only greatly increases the complexity and design difficulty of the entire system, but also inevitably limits its detection effect.

[0005] Transparent ultrasonic transducers are a novel type of ultrasonic transducer with excellent light transmittance in its overall structure. They allow light to pass directly through the entire transducer structure and illuminate the target, while the transducer receives the photoacoustic signals generated by the target, achieving efficient photoacoustic imaging (CN108703744A-Transparent Ultrasonic Transducer and Application-Disclosure). Currently, most transparent ultrasonic transducers are single-element ultrasonic transducers, which require mechanical scanning to achieve imaging, greatly limiting the imaging speed. Transparent array ultrasonic transducers, on the other hand, can achieve rapid and real-time photoacoustic tomography through electronic scanning, and have broad application prospects in the field of ultrasonic-photoacoustic dual-modal imaging.

[0006] Currently, there are two main ways to realize transparent array ultrasonic transducers. One is the capacitive micromachined transparent array ultrasonic transducer. This type of transducer uses micro-nano fabrication technology. Although it can simultaneously meet the requirements of array transducer and light transmittance, it is limited by the capacitive working principle and requires an additional bias circuit system to achieve high-sensitivity detection. At the same time, its emission response is much lower than that of traditional piezoelectric array ultrasonic transducers, making it difficult to meet the needs of applications such as ultrasonic-photoacoustic dual-modal imaging. In addition, due to the limitations of micro-nano fabrication technology itself, the operating frequency of this capacitive micromachined transparent ultrasonic transducer is usually less than 10MHz, making it difficult to fabricate high-frequency array transducers. (AK Ilkhechi. et al. Transparent capacitive micromachined ultrasound transducer linear arrays for combined real-time optical and ultrasonic imaging[J]. Opt Expres,2020,27;28(9):13750-13760). Another type is the piezoelectric transparent array ultrasonic transducer, which has the same structure as traditional transducers, but uses transparent piezoelectric layers, transparent backing, and transparent matching layers to achieve overall transparency. Theoretically, this type of piezoelectric transparent array ultrasonic transducer can achieve the same performance level as traditional array ultrasonic transducers while ensuring light transmittance. However, current piezoelectric transparent array ultrasonic transducers are limited by fabrication processes, sacrificing bandwidth, sensitivity, and other key performance characteristics to meet light transmittance requirements, thus significantly impacting their application in photoacoustic imaging. For example, Chen et al. fabricated a 64-element transparent array ultrasonic transducer using lithium niobate crystal, a transparent piezoelectric material. This transducer used a glass substrate as a transparent backing layer and a single layer of parylene as a transparent matching layer. Due to the extremely low dielectric constant and piezoelectric coefficient of lithium niobate crystal and limitations in the fabrication method, its bandwidth was only 8%, far lower than that of traditional ultrasonic transducers (~40%-80%). (Chen et al. A Transparent Ultrasound Array for Real-time Optical, Ultrasound and Photoacoustic Imaging[J].BMEFrontiers,2022). In the traditional method of fabricating array ultrasonic transducers, piezoelectric materials are usually processed into 1-3 or 2-2 type piezoelectric composites to improve the bandwidth of the transducer. However, it is difficult to achieve transparency of composite materials using traditional piezoelectric composite preparation methods.For example, after the piezoelectric material is cut and filled with epoxy resin, the excess epoxy resin needs to be ground until the piezoelectric material is exposed. This process damages the polished surface of the piezoelectric material, significantly affecting its light transmittance. Because the polymer and piezoelectric components in the composite material have different hardness, stress exists at the interface during polishing, making it difficult to maintain a smooth surface on the piezoelectric composite material. Therefore, secondary polishing cannot improve light transmittance, greatly impacting the preparation of transparent composite materials. Summary of the Invention

[0007] The purpose of this invention is to provide a high-performance transparent piezoelectric composite material, an array transducer, and a method for preparing the same, which solves the problem that high performance (e.g., bandwidth and sensitivity) and good light transmittance are difficult to achieve in existing array transducers.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a method for preparing a high-performance transparent piezoelectric composite material, comprising the following steps:

[0010] Step 1: The piezoelectric material is optically polished to obtain the polished piezoelectric material;

[0011] Step 2: Electrodes are prepared on both the top and bottom surfaces of the polished piezoelectric material to obtain a piezoelectric material with electrodes.

[0012] Step 3: The piezoelectric material with electrodes is made transparent to obtain a transparent piezoelectric layer;

[0013] Step 4: Place one side of the transparent piezoelectric layer on the substrate and perform optical-grade polishing on the other side of the transparent piezoelectric layer until the designed thickness is achieved, to obtain the polished transparent piezoelectric layer.

[0014] Step 5: Cut the polished surface of the polished transparent piezoelectric layer according to the preset matrix structure to obtain a high-performance transparent array piezoelectric composite material.

[0015] Preferably, in step 1, the piezoelectric material is a binary relaxo-lead titanate ferroelectric material or a ternary relaxo-lead titanate ferroelectric material.

[0016] Preferably, in step 3, the piezoelectric material with electrodes is subjected to a transparentizing process, and the specific process conditions are as follows:

[0017] When the piezoelectric material is a binary relaxo-lead titanate ferroelectric material: the frequency of the alternating current electric field is 0.1-102Hz; the waveform of the alternating current electric field is a sine wave, triangular wave, square wave or pulse wave; the polarization temperature is 25-120℃; and the peak value of the alternating current electric field is 0.5-5.0kV.

[0018] When the piezoelectric material is a ternary relaxo-lead titanate ferroelectric material: the DC electric field amplitude is 0.5-5.0kV mm-1; the polarization temperature is 25-120℃.

[0019] Preferably, in step 5, the polished surface of the polished transparent piezoelectric layer is cut according to a preset matrix structure to obtain a high-performance transparent array piezoelectric composite material. The specific method is as follows:

[0020] The polished surface of the polished transparent piezoelectric layer is cut according to a preset matrix structure, wherein the cutting depth is less than the thickness of the polished transparent piezoelectric layer;

[0021] A layer of blue chip film is attached to the cut surface of the transparent piezoelectric layer after cutting.

[0022] Insulating epoxy resin is filled into the side of the cut, and after the epoxy resin dries and cures, the blue film of the chip is removed to obtain a high-performance transparent array piezoelectric composite material.

[0023] A high-performance transparent array piezoelectric composite material, wherein the high-performance transparent array piezoelectric composite material is prepared by the method described above.

[0024] A method for fabricating a high-performance transparent array transducer includes the following steps:

[0025] A high-performance transparent array transducer was prepared using the high-performance transparent piezoelectric composite material obtained by the method described above.

[0026] Preferably, a high-performance transparent array transducer is prepared using a high-performance transparent piezoelectric composite material. The specific method is as follows:

[0027] Step 1: A transparent electrode layer is formed on one surface of a high-performance transparent piezoelectric composite material;

[0028] Step 2: A transparent matching layer is prepared on the surface of the transparent electrode layer;

[0029] Step 3: Cut the other surface of the high-performance transparent piezoelectric composite material according to the preset array structure until it is connected to the array structure of the other surface of the high-performance transparent piezoelectric composite material to obtain multiple array elements.

[0030] Step 4: Connect the electrodes of each array element to the flexible circuit board;

[0031] Step 4: Prepare a transparent backing layer on the upper surface of the flexible circuit board to obtain a high-performance transparent array transducer.

[0032] A high-performance transparent array transducer is prepared by the method described above.

[0033] An application of a high-performance transparent array transducer: a transducer probe is fabricated using the high-performance transparent array transducer prepared by the method described above.

[0034] Preferably, the transducer probe includes a housing, within which a high-performance transparent array transducer, a lens, and an optical fiber bundle are disposed. The transmitting end of the optical fiber bundle passes through the lens and is incident on the high-performance transparent array transducer, and the transmitting end of the high-performance transparent array transducer is used to emit laser signals.

[0035] Compared with the prior art, the present invention has at least the following advantages:

[0036] This invention provides a method for preparing a high-performance transparent piezoelectric composite material. The preparation method uses a process of filling the adhesive from the side of the cut, which can ensure that the surface of the epoxy resin and the surface of the piezoelectric material are flush and coplanar without secondary grinding. This avoids the influence of stress at the interface between the polymer material and the piezoelectric material in traditional piezoelectric composite material preparation methods on the grinding and polishing effect and light transmittance.

[0037] The present invention provides a method for fabricating a high-performance transparent array transducer, which not only enables the array transducer to meet the requirements of light transmittance, but also, due to the excellent electromechanical coupling and piezoelectric properties of the composite material, avoids the influence of the transverse vibration mode of the transducer elements, making the performance (e.g., bandwidth and sensitivity) of the transparent array transducer comparable to that of traditional array transducers, so as to meet the application requirements of ultrasound-optical dual-modal imaging; the fabrication method can realize the fabrication of high-frequency transparent array transducers with a frequency greater than 10MHz. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the cutting of a high-performance transparent piezoelectric composite material;

[0039] Figure 2 This is a schematic diagram of high-performance transparent piezoelectric composite material filled with insulating epoxy resin;

[0040] Figure 3 This is a schematic diagram of the cutting of a high-performance transparent array transducer;

[0041] Figure 4 This is a schematic diagram of a high-performance transparent array transducer;

[0042] Figure 5 This is a schematic diagram of the structure of a high-performance transparent array transducer probe;

[0043] Figure 6 This is a pulse-echo performance test diagram of a high-performance transparent array transducer;

[0044] Among them, 1. piezoelectric material, 2. transparent electrode, 3. glass substrate, 4. blade, 5. blue film, 6. insulating epoxy resin, 7. flexible circuit board, 8. transparent backing layer, 9. fiber optic fixer, 10. fiber optic bundle, 11. lens, 12. high-performance transparent array transducer, 13. transparent matching layer, 14. dropper. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings.

[0046] The present invention provides a high-performance transparent piezoelectric composite material, which is composed of a transparentized binary / ternary relaxo-lead titanate ferroelectric single crystal and a polymer material with good light transmittance.

[0047] The present invention provides a method for preparing a high-performance transparent piezoelectric composite material, comprising the following steps:

[0048] Step 1: The surface of the piezoelectric material is optically polished using diamond polishing paste to obtain polished piezoelectric material 1. The piezoelectric material is a binary / ternary relaxo-lead titanate ferroelectric material with a thickness of 0.5-1 mm. The particle size of the polishing paste decreases from 3 μm to 0.5 μm. Polishing is performed until there are no visible scratches on the surface.

[0049] Step 2: Transparent electrodes 2 are prepared on both the upper and lower surfaces of the polished piezoelectric material 1 to obtain a piezoelectric material with electrodes. Specifically, the transparent electrodes are prepared by high-temperature (300℃) electron beam evaporation to deposit indium tin oxide. The sheet resistance of the transparent electrodes is less than 20Ω / □ and the thickness is 200nm.

[0050] Step 3: The piezoelectric material of the prepared electrode is subjected to a transparent treatment to obtain a transparent piezoelectric layer. The specific process conditions are as follows:

[0051] When the piezoelectric material is lead magnesium niobate-lead titanate from the binary relaxomeric lead titanate ferroelectric materials: the frequency of the alternating electric field is 0.1-10. 2 Hz; the waveform of the alternating current electric field is a sine wave, triangular wave, square wave, or pulse wave; the polarization temperature is 25-120℃; the peak value of the alternating current electric field is 0.5-5.0kV;

[0052] When the piezoelectric material is lead indium niobate-lead magnesium niobate-lead titanate ferroelectric material (e.g., ternary relaxor-lead titanate), the DC electric field amplitude is 0.5-5.0 kV mm. -1 The polarization temperature is 25-120℃.

[0053] Transparency conditions / material composition PMN-0.29PT 0.26PIN - 0.44PMN - 0.30PT Thickness dimension 0.5mm 1mm Polarization electric field waveform sine wave DC Polarization electric field frequency 1Hz - Polarization electric field amplitude 250V 1kV polarization temperature 25℃ 80℃

[0054] The piezoelectric properties and light transmittance of the material were tested, and the piezoelectric coefficient d was measured. 33At 2000 pC / N, the electromechanical coupling coefficient k 33 The transmittance is 94%, and the transmittance in the visible light band is 65%-70%.

[0055] Step 4: Fix one side of the transparent piezoelectric layer to the glass substrate 3 with paraffin wax, and grind and optically polish the other side of the transparent piezoelectric layer until the designed thickness (130um) is achieved, and the polished transparent piezoelectric layer is obtained.

[0056] Step 5: The polished surface of the polished transparent piezoelectric layer is cut using a semiconductor dicing machine according to the designed element spacing (180μm) and number of elements (128 elements) to obtain the cut transparent piezoelectric layer.

[0057] The cutting process conditions are as follows: the selected blade width is 12μm; the cutting step is half the element spacing (90μm); the cutting depth is less than the total thickness of the piezoelectric material by approximately 40μm to avoid breakage of the piezoelectric units; the cutting speed is less than 0.4mm / second, and the blade rotation speed is 30,000 rpm to minimize the impact of kerf chipping on the light transmittance of the composite material; Figure 1 As shown;

[0058] The cutting method is mechanical cutting, laser cutting, wet etching, or dry etching.

[0059] Step 6: Attach a layer of chip blue film 5 to the cut surface of the cut transparent piezoelectric layer to ensure that the chip blue film is tightly attached to the wafer without air bubbles, and that the chip blue film and the surface of the piezoelectric material remain flat.

[0060] like Figure 2 As shown, insulating epoxy resin 6 is filled into the side of the cut using capillary principle as an acoustic decoupling material to form a piezoelectric composite material structure. After the epoxy resin dries and cures, the blue film of the chip is removed. This method can ensure that the surface of the epoxy resin and the surface of the piezoelectric material are flush and coplanar without secondary grinding, avoiding damage to the surface of the piezoelectric material caused by secondary grinding, thus ensuring the best light transmittance of the composite material, thereby obtaining a high-performance transparent piezoelectric composite material.

[0061] The present invention provides a method for fabricating a high-performance transparent array transducer, comprising the following steps:

[0062] Step 1: Prepare a low-temperature indium tin oxide transparent electrode on the cut surface of the high-performance transparent piezoelectric composite material to form a transparent electrode layer. Preparing a low-temperature indium tin oxide transparent electrode can avoid the damage of the epoxy resin structure caused by high temperature, and also avoid the depolarization of the piezoelectric material caused by high temperature. The preparation method is to use room temperature DC magnetron sputtering. The sheet resistance of the transparent electrode is less than 60Ω / □ and the thickness is 200nm.

[0063] Step 2: Prepare a transparent matching layer 13 on the surface of the transparent electrode;

[0064] The transparent matching layer 13 is composed of a single layer or multiple layers of transparent materials, including but not limited to organic polymer materials such as epoxy resin, acrylic resin, and Parylene, as well as inorganic transparent materials such as glass and crystal.

[0065] Step 3: Fix the transparent matching layer onto the glass substrate, and cut the other surface of the high-performance transparent piezoelectric composite material according to a preset array structure to obtain multiple array elements; such as Figure 3 As shown;

[0066] Among them, the cutting depth is greater than 40μm, which completely cuts away the uncut parts left in the array structure of the high-performance transparent piezoelectric composite material, thereby dividing the electrodes and reducing crosstalk between piezoelectric array elements.

[0067] Step 4: Connect the electrodes of each array element to the flexible circuit board 7 by adhesive bonding, and connect them to the electronic system through an adapter and coaxial cable.

[0068] The flexible circuit board adopts a localized light transparency design to ensure the connectivity between the piezoelectric array elements and the electronic system without affecting the overall light transmittance of the array transducer.

[0069] Step 5: Fabricate a transparent backing layer 8 on top of the flexible circuit board to obtain a high-performance transparent array transducer, such as... Figure 4 As shown.

[0070] The transparent backing layer 8 is composed of a single layer or multiple layers of transparent materials, including but not limited to organic polymer materials such as epoxy resin, acrylic resin, and Parylene, as well as inorganic transparent materials such as glass and crystals.

[0071] Figure 6 The pulse echo performance of the prepared transducer was tested to characterize the transducer's center frequency and bandwidth. The black curve represents the time-domain signal of the transducer's echo response, and the red curve represents the spectrum of the echo signal. The graph shows that the transducer's center frequency is 10MHz and the -6dB relative bandwidth can reach 80%.

[0072] like Figure 5 As shown, the present invention also provides a high-performance transparent array transducer probe, including a housing, an optical fiber holder 9 disposed inside the housing, an optical fiber bundle 10 fixed on the optical fiber holder 9, and a laser emitting end of the optical fiber bundle 10 incident on a lens 11; the emitting end of the lens incident on a high-performance transparent array transducer 12; the emitting end of the high-performance transparent array transducer is used to transmit laser signals, and can also receive and transmit ultrasonic signals.

Claims

1. A method for preparing a high-performance transparent array piezoelectric composite material, characterized in that, Includes the following steps: Step 1: The piezoelectric material is optically polished to obtain the polished piezoelectric material; Step 2: Electrodes are prepared on both the top and bottom surfaces of the polished piezoelectric material to obtain a piezoelectric material with electrodes. Step 3: The piezoelectric material with electrodes is made transparent to obtain a transparent piezoelectric layer; Step 4: Place one side of the transparent piezoelectric layer on the substrate and perform optical-grade polishing on the other side of the transparent piezoelectric layer until the designed thickness is achieved, to obtain the polished transparent piezoelectric layer. Step 5: Cut the polished surface of the polished transparent piezoelectric layer according to the preset matrix structure to obtain a high-performance transparent array piezoelectric composite material. In step 3, the piezoelectric material with electrodes is made transparent. The specific process conditions are as follows: When the piezoelectric material is a binary relaxomeric lead titanate ferroelectric material: the frequency of the alternating electric field is 0.1-10. 2 Hz; the waveform of the alternating current electric field is a sine wave, triangular wave, square wave, or pulse wave; the polarization temperature is 25-120℃; the peak value of the alternating current electric field is 0.5-5.0 kV; When the piezoelectric material is a ternary relaxomeric lead titanate ferroelectric material: the DC electric field amplitude is 0.5-5.0 kV mm. -1 The polarization temperature is 25-120℃. In step 5, the polished surface of the polished transparent piezoelectric layer is cut according to a preset matrix structure to obtain a high-performance transparent array piezoelectric composite material. The specific method is as follows: The polished surface of the polished transparent piezoelectric layer is cut according to a preset matrix structure, wherein the cutting depth is less than the thickness of the polished transparent piezoelectric layer; A layer of blue chip film is attached to the cut surface of the transparent piezoelectric layer after cutting. Insulating epoxy resin is filled into the side of the cut, and after the epoxy resin dries and cures, the blue film of the chip is removed to obtain a high-performance transparent array piezoelectric composite material.

2. The method for preparing a high-performance transparent array piezoelectric composite material according to claim 1, characterized in that, In step 1, the piezoelectric material is a binary relaxo-lead titanate ferroelectric material or a ternary relaxo-lead titanate ferroelectric material.

3. A high-performance transparent array piezoelectric composite material, characterized in that, The high-performance transparent array piezoelectric composite material is prepared by the method described in any one of claims 1-2.

4. A method for fabricating a high-performance transparent array transducer, characterized in that, Includes the following steps: A high-performance transparent array transducer is prepared using the high-performance transparent piezoelectric composite material obtained by any one of claims 1-2.

5. The method for fabricating a high-performance transparent array transducer according to claim 4, characterized in that, A high-performance transparent array transducer was prepared using a high-performance transparent piezoelectric composite material. The specific method is as follows: Step 1: A transparent electrode layer is formed on one surface of a high-performance transparent piezoelectric composite material; Step 2: A transparent matching layer is prepared on the surface of the transparent electrode layer; Step 3: Cut the other surface of the high-performance transparent piezoelectric composite material according to the preset array structure until it is connected to the array structure of the other surface of the high-performance transparent piezoelectric composite material to obtain multiple array elements. Step 4: Connect the electrodes of each array element to the flexible circuit board; Step 4: Prepare a transparent backing layer on the upper surface of the flexible circuit board to obtain a high-performance transparent array transducer.

6. A high-performance transparent array transducer, characterized in that, The high-performance transparent array transducer is prepared by the method described in claim 4 or 5.

7. An application of a high-performance transparent array transducer, characterized in that, A transducer probe is prepared using the high-performance transparent array transducer obtained by the method described in claim 4 or 5.

8. The application of a high-performance transparent array transducer according to claim 7, characterized in that, The transducer probe includes a housing, within which a high-performance transparent array transducer, a lens, and an optical fiber bundle are disposed. The transmitting end of the optical fiber bundle passes through the lens and is incident on the high-performance transparent array transducer. The transmitting end of the high-performance transparent array transducer is used to emit laser signals.

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