Design method of multi-matching-layer piezoelectric ultrasonic transducer based on metamaterial

Abstract

The invention relates to a design method of a multi-matching-layer piezoelectric ultrasonic transducer based on a metamaterial, relates to the technical field of transducers, solves the problem of how to design the transducer conveniently and quickly, selects parameters of thickness and acoustic impedance of each matching layer, designs an acoustic metamaterial for the matching layers, and improves the design efficiency of the transducer. Selecting and designing raw materials of the metamaterial in each matching layer and the component ratio of the raw materials; the method comprises the following steps: designing a multi-matching-layer piezoelectric ultrasonic transducer by using a metamaterial, and simulating impedance spectrum, pulse echo waveform and frequency spectrum performance parameters of the multi-matching-layer piezoelectric ultrasonic transducer; and then, according to a simulation result, processing and manufacturing the multi-matching-layer piezoelectric ultrasonic transducer based on the metamaterial. According to the design method, performance characterization is conducted on the machined and manufactured transducer, it is ensured that the characterization result is consistent with simulation data, and the effect that the multilayer acoustic impedance piezoelectric ultrasonic transducer can be conveniently and rapidly designed is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transducers, in particular to a design method of a multi-matching layer piezoelectric ultrasonic transducer based on metamaterials. BACKGROUND

[0002] When sound waves are incident from one material to another different material, the reflection coefficient on the material interface is related to the acoustic impedance of the two materials, and the reflectivity formula is as follows: Wherein, Z1 and Z2 are the acoustic impedance of the two materials respectively.

[0003] For example: when the sound wave is incident from the piezoelectric material PZT with an acoustic impedance of about 30 Mrayls (1 rayl = 1 N.s / m2) to the human soft tissue with an acoustic impedance of 1.5 Mrayls, the reflectivity is as high as 82%. The reflection of sound waves caused by acoustic impedance mismatch can seriously reduce the efficiency of the transducer. The sound pulse generated by the voltage pulse excitation of the piezoelectric material of the transducer will be reflected back and forth in the piezoelectric material, and the sound pulse emitted after reflection and the initial excited sound pulse are superimposed, which causes the ringing phenomenon, increases the pulse width of the transducer, reduces the bandwidth, and seriously affects the performance of the transducer.

[0004] Generally, there are higher requirements for the bandwidth, pulse width, etc. of the transducer, for example, the harmonic imaging technology requires the transducer to simultaneously receive the signals of the fundamental frequency and the multiple frequency, which requires the transducer to have a large bandwidth. The multi-layer acoustic impedance matching design of the transducer is usually a better method to improve the wideband performance of the transducer.

[0005] The traditional matching layer material includes some materials in nature, such as quartz, glass, etc., or 0-3 type composite materials prepared by epoxy resin and fillers. For high-frequency transducers, when the acoustic wavelength is close to or less than the size of the filler particles, the traditional 0-3 type composite matching layer material will have problems such as uneven material composition, high-frequency acoustic attenuation coefficient, etc.

[0006] Although the use of smaller fillers such as nanoparticles can alleviate this problem to some extent, such materials still face new problems such as particle agglomeration. In addition, as a 0-3 type composite material, the volume ratio of the filler usually has an upper limit, because the addition of the filler in a high proportion will cause the poor flowability of the composite material, which is difficult to mix uniformly and operate.

[0007] Unlike traditional matching layer materials, the acoustic impedance matching layer of metamaterials refers to a 1-3 or 2-2 type periodic composite material made by microfabrication technology, and its structure is as follows: Figure 1As shown, the structural periodic scale of this type of metamaterial can be as small as a few micrometers, which is sufficient for transducer applications with center frequencies up to tens of MHz. Furthermore, this type of metamaterial can easily achieve a wide range of equivalent acoustic impedance variations by adjusting the duty cycle of its components, meeting the design requirements for multilayer acoustic impedance matching in transducers. Therefore, it can be widely used as an acoustic material for transducers.

[0008] However, the introduction of metamaterials has increased the complexity of ultrasonic transducer design. Due to the complex spatial structure and diverse material parameters of metamaterials, traditional design methods based on human experience have low design efficiency and accuracy, and therefore urgently need to be improved. Summary of the Invention

[0009] The purpose of this invention is to provide a method for multi-layer acoustic impedance matching of piezoelectric ultrasonic transducers using metamaterials, thus solving the problem of how to conveniently and quickly design multi-layer acoustic impedance piezoelectric ultrasonic transducers.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a design method for a multi-matching layer piezoelectric ultrasonic transducer based on metamaterials. The multi-matching layer piezoelectric ultrasonic transducer includes a piezoelectric layer, at least one matching layer disposed at the front end of the piezoelectric layer, and a backing layer disposed at the rear end of the piezoelectric layer. The design methodology includes the following steps: S1. Determine the thickness and acoustic impedance parameters of each matching layer in the multi-matching-layer piezoelectric ultrasonic transducer; S2. Design acoustic metamaterials for the matching layers, and select the raw materials and component ratios of the metamaterials in each matching layer. S3. Design a multi-matched piezoelectric ultrasonic transducer using the metamaterial in S2, and simulate the impedance spectrum, pulse echo waveform and spectral performance parameters of the multi-matched piezoelectric ultrasonic transducer. S4. Based on the simulation results in S3, fabricate a multi-matched piezoelectric ultrasonic transducer based on metamaterials; S5. Characterize the performance of the multi-matched piezoelectric ultrasonic transducer based on metamaterials manufactured in S4 to ensure that the characterization results are consistent with the simulation data.

[0011] Furthermore, the multi-matching layer design method in S1 is designed using Desiltes and Souquet; Alternatively, the multi-matching layer design method in S1 can be implemented by designing the broadband acoustic impedance matching layer of the multilayer ultrasonic transducer using an ideal model. In the case of a light backing, the broadband acoustic impedance matching layer of the multilayer ultrasonic transducer can be designed using the KLM equivalent circuit model. Alternatively, the multi-matching layer design in S1 can employ a method that uses numerical optimization algorithms to design a multi-matching layer transducer with optimal pulse echo and spectral curve performance.

[0012] Furthermore, the equivalent acoustic parameters of the metamaterial in S2 are obtained by calculation using ISO-STRAIN theory or by finite element simulation based on Comsol Multiphysics.

[0013] Furthermore, the metamaterial comprises high acoustic impedance materials and low acoustic impedance materials.

[0014] Furthermore, the high acoustic impedance material includes alumina, silicon, and silicon dioxide, and the low acoustic impedance material includes epoxy resin and silicone rubber.

[0015] Furthermore, in S3, the performance parameters of impedance spectrum, pulse echo waveform, and spectrum of the multi-matched piezoelectric ultrasonic transducer based on metamaterials are simulated and tested using the KLM equivalent circuit model or the finite element simulation method.

[0016] Furthermore, in S3, the performance parameters of impedance spectrum, pulse echo waveform, and spectrum of the multi-matched piezoelectric ultrasonic transducer based on metamaterials are simulated and tested using the KLM equivalent circuit model and the finite element simulation software Comsol Multiphysics.

[0017] Furthermore, the preparation method of the metamaterial matching layer in S4 adopts one of chemical etching, precision machining or micro / nano 3D printing.

[0018] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: This invention provides a design method for a multi-matched layer piezoelectric ultrasonic transducer based on metamaterials. The method involves first selecting the thickness and acoustic impedance parameters of each matching layer, designing the acoustic metamaterial used for the matching layers, and selecting the raw materials and component ratios of the metamaterial in each matching layer. The multi-matched layer piezoelectric ultrasonic transducer is then designed using the metamaterial, and its impedance spectrum, pulse-echo waveform, and spectral performance parameters are simulated. Based on the simulation results, the metamaterial-based multi-matched layer piezoelectric ultrasonic transducer is fabricated. The fabricated transducer is then characterized to ensure consistency between the characterization results and the simulation data. This design method allows for convenient and rapid design of multi-layer acoustic impedance piezoelectric ultrasonic transducers, providing a new approach for obtaining metamaterial-based multi-matched layer piezoelectric ultrasonic transducers. Attached Figure Description

[0019] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic diagram of the structure of the 2-2 type metamaterial in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the type 1-3 metamaterials in Embodiment 1 of the present invention; Figure 3 This is a flowchart of the design method of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the three-layer metamaterial acoustic impedance matching layer transducer of Embodiment 1 of the present invention; Figure 5 This is a schematic diagram comparing the simulated pulse echo curves of the finite element (FEM) and KLM models in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram comparing the simulation spectrum curves of the finite element (FEM) and KLM models in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the four-layer metamaterial acoustic impedance matching layer transducer of Embodiment 2 of the present invention; Figure 8 This is a schematic diagram comparing the simulated pulse echo curves of the finite element (FEM) and KLM models in Embodiment 2 of the present invention; Figure 9 This is a schematic diagram comparing the simulation spectrum curves of the finite element (FEM) and KLM models in Embodiment 2 of the present invention; Figure 10 This is a schematic diagram of a transducer with a two-layer metamaterial acoustic impedance matching layer of polystyrene as the emission medium in Embodiment 3 of the present invention. Figure 11 This is a schematic diagram comparing the simulated pulse echo curves of the finite element (FEM) and KLM models in Embodiment 3 of the present invention; Figure 12 This is a schematic diagram comparing the simulation spectrum curves of the finite element (FEM) and KLM models in Embodiment 3 of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] Example 1 refer to Figure 3 and Figure 4 This example provides a design method for a multi-matching layer piezoelectric ultrasonic transducer based on metamaterials. The multi-matching layer piezoelectric ultrasonic transducer includes a piezoelectric layer, at least one matching layer disposed at the front end of the piezoelectric layer, and a backing layer disposed at the rear end of the piezoelectric layer.

[0024] The specific design method includes the following steps: S1. Determine the thickness and acoustic impedance parameters of each matching layer in the multi-matching-layer piezoelectric ultrasonic transducer; The multi-matching layer design method uses Desiltes and Souquet for design; Alternatively, the broadband acoustic impedance matching layer of the multilayer ultrasonic transducer can be designed using an ideal model. In the case of a light backing, the broadband acoustic impedance matching layer of the multilayer ultrasonic transducer can be designed using the KLM equivalent circuit model (please refer to the existing Chinese patent CN118250618A). Alternatively, a method can be adopted to design a multi-matched layer transducer with optimal pulse echo and spectral curve performance by using numerical optimization algorithms (see Chinese Patent CN118261045A). S2. Design acoustic metamaterials for the matching layers, and select the raw materials and component ratios of the metamaterials in each matching layer. Metamaterials are composed of high acoustic impedance materials and low acoustic impedance materials. High acoustic impedance materials include alumina, silicon and silica, while low acoustic impedance materials include epoxy resin and silicone rubber. The relationship between the equivalent acoustic parameters of metamaterials and their component ratios was obtained through calculations based on the ISO-STRAIN theory. Alternatively, it can be obtained through finite element simulation based on Comsol Multiphysics (please refer to Chinese patent CN117153301A).

[0025] S3. Design a multi-matched piezoelectric ultrasonic transducer using the metamaterial in S2, and simulate the impedance spectrum, pulse echo waveform and spectral performance parameters of the multi-matched piezoelectric ultrasonic transducer. The performance parameters of impedance spectrum, pulse echo waveform and spectrum in multi-matched piezoelectric ultrasonic transducers based on metamaterials were simulated and tested by using the KLM equivalent circuit model or finite element simulation. S4. Based on the simulation results in S3, fabricate a multi-matched layer piezoelectric ultrasonic transducer based on metamaterials; the metamaterial matching layer is prepared by one of the following methods: chemical etching, precision machining, or micro / nano 3D printing. refer to Figure 1 and Figure 2 This is a metamaterial with 1-3 and 2-2 periodicity, fabricated using micro-nano 3D printing technology. The structural periodicity of this metamaterial can be as small as a few micrometers, sufficient for transducer applications with center frequencies up to tens of MHz. Furthermore, this metamaterial allows for easy adjustment of the duty cycle of its components to achieve a wide range of equivalent acoustic impedance variations, meeting the design requirements for multilayer acoustic impedance matching in transducers. Therefore, it can be widely used as an acoustic material for transducers. S5. Characterize the performance of the multi-matched piezoelectric ultrasonic transducer based on metamaterials fabricated in S4 to ensure that the characterization results are consistent with the simulation data.

[0026] refer to Figures 3-6 In this example, the metamaterial matching layer is set as three layers. The metamaterial matrix used is quartz and Spurr epoxy resin. Its acoustic impedance value can vary from 20.6 Mrayals of quartz to 2.42 Mrayals of Spurr epoxy resin. Therefore, this example is a transducer designed with a three-layer matching structure of quartz-metamaterial-Spurr epoxy resin.

[0027] The selected piezoelectric material is PZT piezoelectric ceramic. Its piezoelectric parameters are obtained by testing the impedance spectrum of the piezoelectric material, as shown in Table 1 below: Table 1: Piezoelectric layer material parameters: The output medium of the transducer is water, therefore its load impedance is 1.5Mrayls; The backing material uses a sound-absorbing material with an acoustic impedance of 7.28 Mrayls.

[0028] The three-layer metamaterial matching layer was optimized using the above design method. The optimized matching layer parameters are shown in Table 2 below. Table 2: Parameters of the Matching Layer of the Three-Layer Metamaterial The optimized metamaterials in Table 2 above are used to design a multi-matching layer piezoelectric ultrasonic transducer, as follows: The first matching layer uses pure quartz material with an impedance of 13.23 Mrayls; the second matching layer uses a metamaterial composed of quartz and epoxy resin, with a quartz component ratio of 21.6% and an acoustic impedance of 5.26 Mrayls; the third matching layer uses pure Spurr epoxy resin material with an acoustic impedance of 2.42 Mrayls. The designed transducer structure is referenced from... Figure 4 As shown.

[0029] Subsequently, the transducer designed above was simulated using the finite element simulation software Comsol Multiphysics and the KLM equivalent circuit model. The obtained pulse echo results are referenced. Figure 5 and Figure 6 As shown, since the finite element simulation is a quasi-one-dimensional model, its results are consistent with those of the KLM model. The three-layer metamaterial matching layer transducer designed in this example has a simulation bandwidth exceeding 80% and a very narrow echo pulse, approximately only two cycles.

[0030] Example 2 The content of this embodiment is basically the same as that of embodiment 1, except that: refer to Figure 7 , Figure 8 and Figure 9 This example designs a transducer with four metamaterial matching layers. The matching layer design method follows the same method as in Example 1. The final matching layer parameters are shown in Table 3 below: Table 3: Parameters of the four-layer metamaterial matching layer The optimized metamaterials in Table 3 above are used to design a multi-matching-layer piezoelectric ultrasonic transducer, as follows: The first matching layer uses pure silicon material with an acoustic impedance of 20.6 Mrayls; the second matching layer uses a silicon-epoxy resin metamaterial with an acoustic impedance of 9.92 Mrayls and a silicon content of 36.93%; the third matching layer also uses a silicon-epoxy resin metamaterial with an acoustic impedance of 4.775 Mrayls and a silicon content of 8.67%; the last matching layer uses pure Spurr epoxy resin material with an acoustic impedance of 2.42 Mrayls. A schematic diagram of the four-layer metamaterial matching layer transducer is shown below. Figure 7 As shown.

[0031] The transducer designed above was simulated using the finite element simulation software Comsol Multiphysics and the KLM equivalent circuit model. The obtained pulse echo results are referenced. Figure 8 and Figure 9 As shown, the transducer with a four-layer metamaterial matching layer can achieve a -6dB bandwidth of over 90% when its pulse width does not exceed 2.5 cycles. The simulation results of the quasi-one-dimensional finite element model are consistent with the simulation results of the KLM equivalent circuit model. However, since the four-layer matching has one more matching layer than the three-layer matching, the pulse echo results obtained by the two methods are significantly different.

[0032] Example 3 The content of this embodiment is basically the same as that in Embodiment 1, except that: refer to Figure 10 , Figure 11 and Figure 12 Surface acoustic waves (SAWs) are elastic waves that propagate along the surface of a material. Their energy is concentrated within approximately two wavelengths below the surface (about 0.1-1 mm depth). They are characterized by high sensitivity, low attenuation, and strong directionality. Their propagation speed is affected by physical properties such as material density and elastic modulus, and they are sensitive to surface microcracks and scratches. SAWs can be generated using interdigital transducers, but SAW probes used for non-destructive testing typically convert longitudinal waves generated by piezoelectric transducers into waveforms by passing them through a polymer wedge at a specific angle. The polymer materials used are generally plexiglass, polystyrene, etc.

[0033] Therefore, the output medium of the surface acoustic wave ultrasonic transducer should also be plastics such as plexiglass or polystyrene. Assuming the wedge is made of polystyrene, the acoustic load impedance of the transducer would be 2.57 Mrayls. Under this condition, we used PZT-5A material with an acoustic impedance of 33.48 Mrayls, with the acoustic impedance of polystyrene as the acoustic load, and designed a transducer with two metamaterial matching layers using the same design method as in Example 1. The matching layer parameters are shown in Table 4 below. Table 4: Parameters of the two-layer metamaterial matching layer The optimized metamaterials in Table 4 above were used to design a multi-matching-layer piezoelectric ultrasonic transducer. The metamaterial matrix materials were selected as quartz and Spurr epoxy resin. The first matching layer was a quartz-epoxy resin metamaterial with 86% quartz content and an acoustic impedance of 11.97 Mrayls. The second matching layer was a quartz-epoxy resin metamaterial with 14% quartz content and an acoustic impedance of 4.34 Mrayls. Finally, the designed transducer structure was referenced. Figure 10 As shown.

[0034] Subsequently, simulation results using finite element software and the KLM model were obtained as follows: Figure 11 and Figure 12 As shown in the figure. Simulation results show that the -6dB bandwidth of the two-layer metamaterial matching layer transducer can reach 76% when its pulse width does not exceed 3 cycles. The simulation results of the quasi-one-dimensional finite element model are consistent with the simulation results of the KLM equivalent circuit model.

[0035] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A design method for a multi-matching-layer piezoelectric ultrasonic transducer based on metamaterials, the multi-matching-layer piezoelectric ultrasonic transducer comprising a piezoelectric layer, at least one matching layer disposed at the front end of the piezoelectric layer, and a backing layer disposed at the rear end of the piezoelectric layer; characterized in that, The design methodology includes the following steps: S1. Determine the thickness and acoustic impedance parameters of each matching layer in the multi-matching-layer piezoelectric ultrasonic transducer; S2. Design acoustic metamaterials for the matching layers, and select the raw materials and component ratios of the metamaterials in each matching layer. S3. Design a multi-matched piezoelectric ultrasonic transducer using the metamaterial in S2, and simulate the impedance spectrum, pulse echo waveform and spectral performance parameters of the multi-matched piezoelectric ultrasonic transducer. S4. Based on the simulation results in S3, fabricate a multi-matched piezoelectric ultrasonic transducer based on metamaterials; S5. The performance of the multi-matched piezoelectric ultrasonic transducer based on metamaterials manufactured in S4 is characterized to ensure that the characterization results are consistent with the simulation data.

2. The design method for a multi-matched piezoelectric ultrasonic transducer based on metamaterials according to claim 1, characterized in that, The multi-matching layer design method in S1 uses Desiltes and Souquet. Alternatively, the multi-matching layer design method in S1 can be implemented by designing the broadband acoustic impedance matching layer of the multilayer ultrasonic transducer using an ideal model. In the case of a light backing, the broadband acoustic impedance matching layer of the multilayer ultrasonic transducer can be designed using the KLM equivalent circuit model. Alternatively, the multi-matching layer design in S1 can employ a method that uses numerical optimization algorithms to design a multi-matching layer transducer with optimal pulse echo and spectral curve performance.

3. The design method for a multi-matched piezoelectric ultrasonic transducer based on metamaterials according to claim 1 or 2, characterized in that, The equivalent acoustic parameters of the metamaterial in S2, as a function of its component ratio, are obtained through calculations based on ISO-STRAIN theory or through finite element simulations based on Comsol Multiphysics.

4. The design method for a multi-matched piezoelectric ultrasonic transducer based on metamaterials according to claim 3, characterized in that, The metamaterial comprises high acoustic impedance materials and low acoustic impedance materials.

5. The design method for a multi-matched piezoelectric ultrasonic transducer based on metamaterials according to claim 4, characterized in that, The high acoustic impedance material includes alumina, silicon, and silicon dioxide, and the low acoustic impedance material includes epoxy resin and silicone rubber.

6. The design method for a multi-matched piezoelectric ultrasonic transducer based on metamaterials according to claim 4 or 5, characterized in that, In S3, the performance parameters of impedance spectrum, pulse echo waveform and spectrum of the multi-matched layer piezoelectric ultrasonic transducer based on metamaterial are simulated and tested using the KLM equivalent circuit model and the finite element simulation software Comsol Multiphysics.

7. The design method for a multi-matched piezoelectric ultrasonic transducer based on metamaterials according to claim 6, characterized in that, The preparation method of the metamaterial matching layer in S4 is one of chemical etching, precision machining or micro / nano 3D printing.

Images